Impact of three different feeding regimens on performance, microbiology, sensory, and objective characteristics of Flori...

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Impact of three different feeding regimens on performance, microbiology, sensory, and objective characteristics of Florida Brangus beef cattle
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Thesis (Ph. D.)--University of Florida, 2006.
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Includes bibliographical references.
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by Keawin Sarjeant.
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IMPACT OF THREE DIFFERENT FEEDING REGIMENS ON PERFORMANCE,
MICROBIOLOGY, SENSORY, AND OBJECTIVE CHARACTERISTICS OF
FLORIDA BRANGUS BEEF CATTLE















By

KEAWIN CARON SARJEANT


A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA


2006

























Copyright 2006

by

Keawin Caron Sarjeant














ACKNOWLEDGMENTS

I wish to express my gratitude to Dr. Sally K. Williams, associate professor and

supervisory committee chairperson, for her guidance, patience, and support throughout

the Doctor of Philosophy program. I thank her for being all that she is to me and

believing in me. Appreciation is extended to Dr. Ray Mobley for all of his guidance and

words of encouragement. Thanks are also extended to Dr. Gary Rodrick, Dr. D.D.

Johnson, and Dr. Adegbola Adesogan. I want to thank my parents, Lindsey and Veronica

Sarjeant, and my brother, Kevin Sarjeant, for their love, patience, caring, and support

throughout my pursuit of my Ph.D. degree. Throughout the good and the bad they have

been there for me giving me unconditional love, support, and guidance. Without all of

them I would not be where I am today and be the person I am today. I want to make all of

them just as proud of me as I am of them. I thank Natasha Nicole Sarjeant. Without her I

am nothing. I want to thank my sons, my oldest Keiron Lindsey Sarjeant and my

youngest Kaden Emory Sarjeant for loving daddy no matter what and for being who they

are. They both are my pride and joy and everything that I do, I do it for them. I want to

thank my best friend, Johnny Davis, for everything he has done for me from getting me

here to getting me out of here. I also thank Johnny for keeping me sane throughout the

stressful times and always being there for me, helping me every step of the way. Finally I

want to thank Noufoh Djeri for all of her support, patience, and motherly advice.













TABLE OF CONTENTS


ACKNOWLEDGMENTS .............................................. iii

LIST OF TABLES ................................... ................... vi

ABSTRACT ........................................ ................... x

INTRODUCTION ......................................................1

LITERATURE REVIEW ...................................... ............ 6

Performance ........................... ............................. 6
Pasture and Forages ........................................ ......... 11
Concentrates and Supplements ........................................ 23
Feed Additives ..................................................... 30
M icrobiology .................................. .................... 36
Microorganisms of Concern in Beef Cattle Food Safety ..................... 37
Characteristics of Escherichia coli ..................................... 37
Fecal coliforms ............................. ........................ 43
Characteristics of Salmonella ......................................... 44
Parasites ............................... ........................... 45
Sensory Characteristics of Beef ........................................ 50
Objective Characteristics ................................... .......... 53

MATERIALS AND METHODS .......................................... 58

Anim als ................................... ....................... 58
Animal Diets and Feeding Procedure .................................. 59
Weight, Fecal, and Blood Collection ................................. 60
Microbiological Analysis .............................................. 61
Parasite Analysis ................................................... 63
Environmental Samples .............................................. 63
Animal Slaughter and Carcass Characteristics ............................ 65
Sensory Analysis ................................................... 66
Objective Color Analysis ..................................... .. 68
Warner Bratzler Shear Analysis ........................................ 68
pH ............................................................... 69








Data Analysis .. .... ... .. ... .......... .. .... ... 69

RESULTS AND DISCUSSION .......................................... 71

Experiment One: Performance, Microbiology, Sensory and Objective Analyses for
17 Month Old Brangus Cattle and Environmental Sample Analyses ......... 71
Experiment Two: Performance, Microbiology, Sensory and Objective Analyses for
10 Month Old Brangus Cattle and Environmental Sample Analyses ......... 97
Cost Analysis for Experiment One ................................... 118
Cost Analysis for Experiment Two ................................... 121

SUMMARY AND CONCLUSIONS ..................................... 125

APPENDIX MEAN WEIGHT OF BRANGUS STEERS DURING EXPERIMENT
ONE AND TWO .......................................... 131

LIST OF REFERENCES ................................................ 134

BIOGRAPHICAL SKETCH ............................................ 153














LIST OF TABLES


Table ae

1 Average daily weight gain values of Brangus steers fed different commercially
available feed concentrates, and allowed to graze on bahiagrass or allowed to graze
only for four months: Experiment One ................................ 72

2 Average daily weight gain values of Brangus steers that were initially fed Super 12,
or B-80 and allowed to graze, or allowed to graze only and then placed onto Super
12 concentrate: Experiment One ...................................... 74

3 Mean total aerobic bacteria counts of steer fecal samples. Steers were given two
different commercially available feeds and allowed to graze on bahiagrass or
allowed to graze only: Experiment One ................................ 76

4 Mean generic Escherichia coli counts of steer fecal samples. Steers were given two
different commercially available feeds and allowed to graze on bahiagrass or
allowed to graze only: Experiment One ............................... 77

5 Mean total aerobic bacterial counts of bahiagrass that was grazed by all three
groups of steers for Experiment One ................................... 80

6 Mean total aerobic bacteria counts, Escherichia coli, and Fecal coliform counts for
the animal drinking water for Experiment One ........................... 80

7 Mean total aerobic bacterial counts of the two commercially available animal feeds
given to the steers for Experiment One ................................ 81

8 Mean parasitic eggs isolated from feces of steers given two different commercially
available feeds and allowed to graze on bahiagrass or allowed to graze only:
Experiment One ................................................... 82

9 Mean proximate analysis values and pH for bahiagrass samples collected from
pastures for Experiment One.......................................... 83

10 Mean blood values of aspartate amino transferase and gamma glutamyl
transpeptidase in the blood of steers given two different commercially available








feeds and allowed to graze on bahiagrass or allowed to graze only for Experiment
O ne ............................................................. 84

11 Mean blood values for calcium, magnesium, chloride and potassium in the blood of
steers given two different commercially available feeds and allowed to graze on
bahiagrass or allowed to graze only for Experiment One ................... 85

12 Mean blood values for anion gap, glucose, and carbon dioxide in the blood of steers
given two different commercially available feeds and allowed to graze on
bahiagrass or allowed to graze only for Experiment One ................... 89

13 Carcass characteristics and standard error of means from steers that were given two
different commercially available feeds and allowed to graze on bahiagrass or
allowed to graze only for Experiment One ....... ..................... 90

14 Mean objective color values of Brangus steer steaks cut from the short loin portion
of steers given two different commercially available feeds and allowed to graze on
bahiagrass or allowed to graze only for Experiment One ................... 92

15 Mean pH values of Brangus steer steaks cut from the short loin portion of steers
given two different commercially available feeds and allowed to graze on
bahiagrass or allowed to graze only for Experiment One ................... 93

16 Mean thaw loss and cooking loss of Brangus steer steaks cut from the short loin
portion of steers given two different commercially available feeds and allowed to
graze on bahiagrass or allowed to graze only for Experiment One ............ 94

17 Mean trained sensory panel scores of Brangus steer steaks cut from the short loin
portion of steers given two different commercially available feeds and allowed to
graze on bahiagrass or allowed to graze only for Experiment One ............ 95

18 Mean Warner-Bratzler Shear force values of Brangus steer steaks cut from the short
loin portion of steers given two different commercially available feeds and allowed
to graze on bahiagrass or allowed to graze only for Experiment One .......... 96

19 Average daily weight gain values of Brangus steers fed different commercially
available feed concentrates, and allowed to graze on bahiagrass or allowed to graze
only for seven months: Experiment Two .............................. 98

20 Average daily weight gain values of Brangus steers that were initially fed Super 12,
or B-80 and allowed to graze, or allowed to graze only and then placed onto Super
12 concentrate: Experiment Two .................................... 100








21 Mean total aerobic bacteria counts, of steer fecal samples. Steers were given two
different commercially available feeds and allowed to graze on bahiagrass or
allowed to graze only for Experiment Two .......................... 101

22 Mean generic Escherichia coli counts, of steer fecal samples. Steers were given
two different commercially available feeds and allowed to graze on bahiagrass or
allowed to graze only for Experiment Two ............................. 103

23 Mean Fecal coliforms counts, of steer fecal samples. Steers were given two
different commercially available feeds and allowed to graze on bahiagrass or
allowed to graze only for Experiment Two ............................. 104

24 Mean total aerobic bacteria counts, Escherichia coli, and Fecal coliform counts of
bahiagrass that was grazed by all three groups of steers only for Experiment
Two ........................................................... 105

25 Mean total aerobic bacterial counts, Escherichia coli, and Fecal coliform counts of
the animal drinking water of steers given two different commercially available
feeds and allowed to graze on bahiagrass or allowed to graze only for Experiment
Two ........................................................... 106

26 Mean total aerobic bacterial counts, E. coli, and fecal coliforms of the two
commercially available animal feeds given to the steers only for Experiment
Two ........................................................... 107

27 Mean coccidia parasitic eggs isolated from feces of steers given two different
commercially available feeds and allowed to graze on bahiagrass or allowed to
graze only for Experiment Two ..................................... 108

28 Mean parasitic eggs, isolated from feces of steers given two different commercially
available feeds and allowed to graze on bahiagrass or allowed to graze only for
Experiment Two .................................................. 108

29 Mean proximate analysis values and pH for bahiagrass samples collected from
pastures for Experiment Two ...................................... 109

30 Mean blood for chloride, sodium, potassium and phosphorous for steers given two
different commercially available feeds and allowed to graze on bahiagrass or
allowed to graze only for Experiment Two ............................. 110

31 Carcass characteristics and standard error of means for steers that were given two
different commercially available feeds and allowed to graze on bahiagrass or
allowed to graze only for Experiment Two ............................. 112








32 Mean objective color values of steaks cut from the short loin portion of steers given
two different commercially available feeds and allowed to graze on bahiagrass or
allowed to graze only for Experiment Two .......................... 114

33 Mean pH values of steaks cut from the short loin portion steers given two different
commercially available feeds and allowed to graze on bahiagrass or allowed to
graze only for Experiment Two ...................................... 115

34 Mean thaw loss and cooking loss for steaks cut from the short loin portion of steers
given two different commercially available feeds and allowed to graze on
bahiagrass or allowed to graze only for Experiment Two .................. 115

.35 Mean trained sensory panel scores of steaks cut from the short loin portion steers
given two different commercially available feeds and allowed to graze on
bahiagrass or allowed to graze only for Experiment Two .................. 116

36 Mean Warner-Bratzler Shear force (WBS) values of steaks cut from the short loin
portion steers given two different commercially available feeds and allowed to
graze on bahiagrass or allowed to graze only for Experiment Two ........... 117

37 Commercial feed cost summary for Experiment One ..................... 119

38 Commercial feed cost summary for Experiment Two ..................... 122

39 Mean weight of Brangus steers fed different commercially available feed
concentrates, and allowed to graze on bahiagrass or allowed to graze only for four
months: Experiment One ........................................... 131

40 Mean weight of Brangus steers that were initially fed Super 12, or B-80 and
allowed to graze, or allowed to graze only and then placed onto Super 12
concentrate: Experiment One .................................... 132

41 Mean weight of Brangus steers fed different commercially available feed
concentrates, and allowed to graze on bahiagrass or allowed to graze only for ten
months: Experiment Two .......................................... 133












Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy

IMPACT OF THREE DIFFERENT FEEDING REGIMENS ON PERFORMANCE,
MICROBIOLOGY, SENSORY, AND OBJECTIVE CHARACTERISTICS OF
FLORIDA BRANGUS BEEF CATTLE

By

Keawin Caron Sarjeant

May 2006

Chair: Sally K. Williams
Major Department: Animal Sciences

Two experiments were conducted to evaluate three typical commercially available

feeding regimens and their effects on average daily weight gain, prevalence of E. coli

0157:H7, generic E. coli, fecal coliforms, total aerobic bacteria, and parasites in beef

cattle. This study also focused on blood chemistry of the animals, the proximate

composition of the grass on which animals grazed, animal drinking water, animal feed,

the resulting carcass characteristics, pH, objective color characteristics and sensory

attributes of steaks collected from the short loin of the carcasses. Sixty Florida Brangus

steers, where 30 steers with an average age of 17 months were used for Experiment One,

and 30 steers with an average age of 9 months were used in Experiment Two. Steers in

both experiments were assigned randomly to one of three feeding regimens: 1) Super 12,

a non medicated concentrate, plus bahiagrass, 2) B-80, a medicated concentrate








containing lasalocid, plus bahiagrass, and 3) bahiagrass only (Grazers). Cattle fed Super

12 concentrate had a higher average daily gain (ADQ) and reached the target slaughter

weight two and three months earlier than cattle fed B-80 and grazer cattle in Experiments

One and Two, respectively. Super 12 cattle had significantly higher (P < 0.05) carcass

weights when compared to grazer cattle in Experiment One, and B-80 and grazer cattle in

Experiment Two. No E. coli 0157:H7 nor Salmonella spp. were detected in any of the

fecal samples analyzed in both experiments. The cattle fed the two concentrates had

significantly lower coccidia parasites in Experiment One but not Experiment Two when

compared to grazer cattle. The proximate composition of the grass was similar (P > 0.05)

for all treatments. Objective color, pH, and Warner Bratzler shear force were similar (P >

0.05) for all treatments. In Experiment One sensory panelists detected significantly lower

(P < 0.05) overall tenderness in steaks from Super 12 fed cattle when compared to

grazers. Panelists also detected significantly lower (P < 0.05) connective tissue in steaks

from the grazer cattle when compared with steaks from Super 12 and B-80 fed cattle. In

Experiment Two, panelists detected significantly lower (P < 0.05) juiciness in steaks from

Super 12 and B-80 fed cattle when compared to steaks from grazer cattle. Data in this

study demonstrated that beef cattle grazing bahiagrass and supplemented with Super 12

can be raised in a shorter amount of time and produce steaks acceptable in meat quality

and palatability to consumers.













INTRODUCTION

The National Commission on Small Farms, which was designed in 1997 by the

U.S. Secretary of Agriculture to examine issues facing small farms, defines a small farm

as a farm with less than $250,000 gross receipts annually and on which day-to-day labor

and management are provided by the farmer and/or farm family that owns the production

or owns, or leases, the productive assets (Hoppe and Banker, 2005). Large farms are

defined as farms having sales of $250,000 to $499,999, and very large farms are defined

as farms having sales of $500,000 or more. Small farms have been critical to the fabric of

American society throughout the nation's history. Today, as historically, the vast majority

of all farms in the United States are considered small (90%) but these small farms

produced a modest share (28%) of farm output in 2001 (Hoppe and Banker, 2005). Large

and very large farms account for only about 7% of farms in the United States but 58% of

the value of production in 2001. Owning and operating a small farm represents an

avenue to economic independence and entrepreneurial achievement for many Americans

from all walks of life. Small farm owners and operators are a diverse group of

Americans, including Hispanics, Native Americans, ethnic Europeans, African-

Americans, Asians, women, persons with disabilities, and other minorities.

In Florida, the nearly 44,000 commercial farmers are among the most productive in

the world, furnishing the nation with a dependable and safe food supply, and providing an






2

economic base for the state. In 2003, Florida farmers utilized 10.2 million of the state's

nearly 35 million acres. Florida ranks No. 9 nationally in the value of farm products with

2002 sales of $6.85 billion. State ranchers and herdsmen rank among the top 28 states in

the production of beef, poultry and pork, with livestock and product sales topping $1.2

billion in 2003. Florida employed more than 87,000 farm workers in 2003 and paid them

$1.4 billion. In addition, Florida farmers rank third nationally in net farm income with

$2.7 billion in 2002 (Mongiovi, 2004).

Production technologies, management systems, research and extension education

that are appropriate for small and economically disadvantaged livestock producers are

needed to identify and enhance the efficiency, profitability and competitive position of

family farms. A major concern of a cattle operation is an effective feeding program. The

diversity of programs and methods of raising cattle make this area one that requires

factual and practical information. Small and limited income farmers may not have the

same resources or capabilities to feed cattle to target weights as a larger producer.

Therefore, small and limited income farmers are challenged to provide cost effective and

practical approaches to feeding cattle to market weight in order to realize a profit and

maintain sustainability. Beef enterprises work well with grain, orchard, vegetable, or

other crop operations. Cattle can make efficient use of feed resources that have little

alternative use, such as crop residues, marginal cropland, untillable land, or rangeland

that cannot produce crops other than grass (Pirelli et al., 2000).

Traditional feeder-cattle enterprises grow weaned calves (450 to 600 pounds) and

yearling steers or heifers (550 to 800 pounds) to slaughter weights of 1,100 to 1,400

pounds (Comerford et al., 2001). Many cattle feeders purchase lightweight feeder calves








(350 to 550 pounds), graze them during the spring and summer and then finish them in

the feedlot starting in late summer or fall (Comerford et al., 2001). Cattle producers rely

on several feeding strategies to bring cattle to market weights. These include extensively

feeding pasture only, semi-intensive feeding of pasture and concentrate feeds and

intensive feeding of high protein feeds. In many instances, feeds are medicated to

increase weight gain and decrease bacteria and gastrointestinal parasite loads. There is

increased skepticism for the use of non-therapeutic medications in that the practice is

viewed as potentially increasing the resistance by microorganisms and parasites.

The meat and poultry industries are always concerned with the problem of

pathogenic bacteria appearing and becoming widespread in fresh and processed meat and

poultry products. Since 1996, Food Safety Inspection Service (FSIS), the primary

enforcement body of the U.S. for meat and poultry, has required that all plants develop,

adopt, and implement a Hazard Analysis Critical Control Points (HACCP) food safety

program. This system is designed to ensure the safety of food products by requiring each

individual plant that produces meat and poultry, whether fresh or processed, to look at

every step in their respective processes, and establish critical control points (CCP's),

critical limits (CL's), corrective actions for deviations from the CCP's, monitoring of

those CCP's to assure they are under the CL's, and keeping extensive written records.

Schmidt (2001) described HACCP as a logical system and preventive approach to food

safety designed to identify hazards and/or critical situations and to produce a structured

plan to control these situations. The emphasis of HACCP is to base the food safety

program on sound scientific data, and to focus on prevention and control of food safety

problems at highly specific (and controllable) points in the process chain (Schmidt,






4

2001). Microbiological contamination of animal carcasses during slaughtering

procedures is an undesirable but unavoidable problem in the conversion of live animals to

meat for human consumption (Dickson and Anderson, 1991). Although good farming

and manufacturing practices discourage harmful bacteria from entering the food supply,

they do not guarantee a product that is free of pathogens that could cause food borne

illness.

The term "pre-harvest food safety" has been coined to describe attempts to ensure

safety of the final product by minimizing or eliminating potential human pathogens and

chemical residues from farm animals. Pre-harvest food safety in the food animal area has

been recognized for centuries as an important aspect of assuring overall quality and safety

of food animal products going into the human food chain (Marion, 2002). Preharvest

cattle management significantly impacts public health (Hovde et al., 1999). Cattle

transiently harbor Escherichia coli 0157:H7 in their gastrointestinal tracts, and many

human infections result from ingestion of contaminated bovine food products (Kaper and

O'Brien, 1998). E. coli 0157:H7 contamination, which has caused product recalls and

plant closures, has an enormous economic impact on the meat industry (Centers for

Disease Control, 1997). Human infections with E. coi 0157:H7 result in hemorrhagic

colitis that can progress to hemolytic-uremic syndrome, a life threatening sequela that is

the most common cause of acute renal failure in children (Kaper and O'Brien, 1998).

This project work is designed to develop a model program that can be utilized by

small livestock producers to enhance the value and safety of livestock products; monitor

performance parameters and prevalence of E. coli 0157:H7, generic E. coi, fecal

coliforms, total aerobic bacteria, and parasites in livestock when subjected to a






5

comprehensive feeding and optimized management program; and monitor the effects of

the program on dressing percentage, and subjective and objective consumer parameters.













LITERATURE REVIEW

Performance

Performance is the key to success in the cattle business. Good genetics, proper

nutrition and top-notch health programs are the all-important ingredients that go into a

successful cattle breeding program (Rew, 1998). Improving animal performance, carcass

characteristics, and meat quality traits are the main objectives of most research carried out

in the beef production area (Sami et al., 2004). Satisfying the consumer's requirement for

a consistent product is the major target of beef producers and retailers. Small and limited

income farmers are challenged to provide cost effective and practical approaches to

feeding cattle to market weight in order to realize a profit and maintain sustainability.

There are two main types of growing and feeding operations-steer/heifer operations

and stocker (or backgrounding) operations. In a steer or heifer operation, 500- to 600-

pound feeder calves are purchased after weaning at approximately 7 to 10 months of age.

They can be fed out and marketed in less than a year from the time of purchase. Thus, the

investment on each calf is returned within a comparatively short time. This type of

operation may not require much land, but adequate facilities are essential so that animals

can be kept comfortable and under control (Pirelli et al., 2000). A stocker or

backgrounding operation pastures or feeds calves until they reach 750 to 800 pounds,

after which they are sold to a feedlot for finishing. Usually weaned calves or yearlings






7

are purchased, go on pasture when the grass is ready, and are sold when the pasture

season is over. In these calf and yearling enterprises, purchase price and selling price

greatly influence profitability (Pirelli et al., 2000).

Cattle producers rely on several feeding strategies to bring cattle to market weight

These include extensively grazing on pasture alone, semi-intensive grazing on pasture

with concentrate supplementation, and intensive feeding of high protein feeds. The

feeding plan is considered one of the most important factors that affect meat production

(Sami et al., 2004). Feed requirements are based on the need for specific amounts of

various classes of nutrients. Each nutrient fulfills specific roles in growth, production or

metabolism. Nutrient classes are defined by their chemical structure or by their function

in metabolism. The classes are energy, protein, minerals, and vitamins.

Energy provides the body with the ability to do work (Hamilton, 1991). In beef

cattle rations, energy is usually expressed as % total digestible nutrients (TDN).

Maintenance includes growth, lactation, reproduction, movement and feed digestion.

Energy is the nutrient required by cattle in the greatest amount. It usually accounts for the

largest portion of feed costs (Steen and Kilpatrick, 1995). The primary sources of energy

for cattle are cellulose and hemicellulose from roughages, and starches from grains. Fats

and oils have a high energy content but usually make up only a small part of the diet.

Protein is one of the main building blocks of the body. It is usually measured as %

crude protein (CP) (Kijowski, 2001). It is a major component of muscles, the nervous

system and connective tissue. Protein is composed of chains of amino acids. Adequate

dietary protein is essential for maintenance, growth, lactation and reproduction.

Information about protein sources has changed much over the past 10 years. Words like






8

"bypass," "escape," or "slowly degraded" have been used to describe some proteins. These

terms have the same meaning and refer to a protein source's ability to escape breakdown

in the rumen (Stock et al., 1996). Digestible protein entering the rumen is either broken

down by the rumen microbes to volatile fatty acids and ammonia or it escapes breakdown

and passes "as is" to the small intestine where it is digested and absorbed as amino acids

and peptides. This latter protein is called bypass or escape, or sometimes is known as

slowly degradable protein (Kijowski, 2001). The extent to which a particular protein

source is broken down depends on its rate of rumen digestion. Soybean meal protein is

broken down to a greater extent, and less escapes the rumen undigested compared to

protein sources like dehydrated alfalfa, blood meal, meat meal or corn gluten meal.

The rumen microbes require a certain amount of nitrogen in the form of ammonia.

When feeding sources of protein that are slowly degraded, supplemental urea is used to

meet the microbes' nitrogen needs. Although nonprotein nitrogen sources (urea, biuret)

are completely broken down in the rumen, they supply only nitrogen to the microbes.

They do not supply amino acids, peptides or any carbon chains. The microbes also need

carbon chain fragments to form microbial protein. Most of these carbon chains are

produced in the digestion of forages or grains. However, certain carbon chains

(branched-chain fatty acids) may not be produced in sufficient quantities to provide for

maximum microbial protein synthesis. Degradation of feed proteins can supply these

limiting branched-chain fatty acids. This protein source is called rumen degradable or

rapidly degradable protein.

Protein sources can be divided into four categories: 1) high bypass or slowly

degradable protein; 2) intermediate bypass protein; 3) low bypass protein; and 4) rapidly






9
degradable protein. Examples of high bypass/slowly degradable protein are blood meal,

fish meal, corn gluten meal, and dehydrated alfalfa (Stock et al., 1996). Examples of

intermediate bypass protein include cottonseed meal and linseed meal. Some examples

of low bypass protein are soybean meal, alfalfa (hay, haylage, sun-cured pellets), peanut

meal, sunflower meal, safflower meal, feather meal and rape seed (Canola) meal.

Rapidly degradable protein sources include casein, whey, steep liquor and distillers

solubles (Stock et al., 1996). Animals consuming grain, silage, alfalfa or lush pasture do

not need to be supplemented with rumen degradable protein (Stock et al., 1996).

Inadequate and excessive intakes of protein have been shown to have significant

detrimental effects on the liveweight gain and carcass composition of beef cattle (Lindsay

and Davies, 1981; Steen, 1988, 1989).

Various minerals are required for growth, bone formation, reproduction and many

other body functions. Those that are required in fairly large amounts are called

macrominerals (Hamilton, 1991; Romans et al., 1994). They include sodium (salt),

calcium, phosphorous, magnesium and potassium. Those that are required in very small

amounts (micro or trace minerals) include iodine, copper, zinc, sulphur and selenium.

Adding supplementary minerals to the ration is usually required to ensure that the proper

amounts of these elements are available to the animal. The type of supplementary mineral

mix required is determined by the feeds in the ration and the animal's requirements

(Hamilton, 1991).

Vitamins are biological compounds which are active in extremely small amounts.

Vitamins of concern in beef cattle nutrition include Vitamin A, Vitamin D and Vitamin

E. They are usually reported in International Units (IU's) (Hamilton, 1991; Romans et al.,






10

1994). Vitamin needs of beef cattle are largely confined to A, D, and E, because bacteria

in the rumen of cattle are considered to have the ability to synthesize vitamin K and the B

vitamins in sufficient quantities to meet the animal's requirement (Sewell, 1993).

Vitamin K is essential in the liver for production of prothrombin. Low levels of

prothrombin in the blood lengthen blood clotting time and cause internal bleeding. Some

metabolic functions of vitamin A are not yet known. A chief role is maintenance of

epithelial tissue (skin and lining of respiratory, digestive and reproductive tract) in a

healthy condition. Vitamin A is essential for proper kidney function and normal

development of bones, teeth and nerve tissue (Sewell, 1993). Vitamin D increases the

absorption from the digestive tract and metabolic use of calcium and phosphorus. It helps

regulate blood calcium levels and the conversion of inorganic to organic phosphorus.

Vitamin D aids in the formation of sound bones and teeth (Sewell, 1993). Its principal

role may be as a chemical antioxidant to reduce the destruction of other vitamins and

essential fatty acids both in the digestive tract and after their absorption. Stiff-lamb

disease and white-muscle disease in calves have been prevented and cured by use of

vitamin E (Sewell, 1993).

Fresh forage is a good source of Vitamins A, D and E. Vitamin content of well

preserved hay is initially high, but declines over time. Silages usually contain low levels

of vitamins because the fermentation process destroys most of the vitamins. Grains

usually contain relatively low amounts of these vitamins (Hamilton, 1991; Romans et al.,

1994).






11

Pasture and Forages

The world's most abundant renewable sources of energy are pastures and forages.

Swine, poultry, and humans are unable to utilize forages to any great extent because

monogastrics lack the enzymes or bacteria needed to degrade fibrous compounds.

Fortunately, ruminant animals can utilize this energy through their symbiotic relationship

with fiber-fermenting microorganisms in the rumen (Cecava, 1995).

Cattle grazing is an efficient way to produce food for human use on land where

crops for human consumption cannot be produced. In the U.S., land area that is used for

grazing animals is more than twice the size of land area that can be used for producing

food. The use of land to graze animals more than doubles the land area in the U.S. that

can be used to produce food. The number of acres needed for each cow depends on the

level of forage production, as well as the cattle and their management. The level of

forage production varies with species, soil fertility, moisture, temperature, season, and

other related factors (Aerts and Nesheim 2002).

Grasses are the backbone of the Florida livestock industry. Different grasses are

used for different purposes depending on season of year (warm or cool season), soil

conditions (dry or wet), age of livestock utilizing the forage (mature cattle or weaned

calves), management methods used (continuous or rotational grazing), and fertilization

program (Mislevy, 2002). Some forages can also be grown for hay, while others are

suitable only for grazing. Several forages that grow in south Florida cannot be grown in

north Florida because they lack sufficient cold tolerance. Some forages can only be grown

on well-drained soils while others are adapted to very moist soils (Aerts and Neseim,

2002).






12

Pastures and forages can be classified into two different categories that designate

their general life expectancy. These classifications are permanent (perennials) and

temporary pastures (annuals). Permanent pasture is a type of pasture that lives for many

years. This type of pasture is usually found on land that cannot be used for cultivated

crops, largely because of topography or moisture. With minimal care, such pastures can

last indefinitely. Most farms have at least some such land which is fit only for permanent

pasture (Cecava, 1995). Temporary pastures are pastures that are seeded for use for very

short periods of time. They are provided when regular permanent or rotational grazing is

not available. Examples include, sudan grass or sudex seeded in the spring for summer

grazing, or oats and rape seeded for spring and summer grazing. Rye may often be

seeded following bean or corn harvest for fall and winter grazing (Cecava, 1995).

The success of a beef cattle operation is tied directly to the amount and quality of

forage, whether pasture or hay, available to the beef animals. As a general rule, readily

available pasture of high quality is the cheapest source of feed nutrients (Aerts and

Nesheim, 2002). Selection of pasture species for beef cattle depends on three major

factors: temperature, soil moisture, and soil fertility. Selection of pasture species in

Florida must focus primarily on temperature, due to the wide-ranging climate. South

Florida has a climate similar to subtropical regions, while north Florida has subtropical

summers but temperate winters (Aerts and Nesheim, 2002).

One method of categorizing pasture crops is to divide them into grasses and

legumes. The grasses include, bahiagrass, bermudagrass, bluegrass, bromegrass, timothy,

fescue, and sorghums. The legumes include, alfalfa, bur clover, red clover, alsike clover,

white clover, birdsfoot trefoil, and vetches. Warm season perennial grasses, are the






13

foundation of pastures in Florida. Bahiagrass is predominantly used. It can be established

from seed and is widely adapted, very dependable, persistent, and easy to manage (Aerts

and Nesheim, 2002).

Generally, crude protein (CP) content of a forage is positively correlated with

quality. In general, high-protein forages are considered high-quality forages. If a

high-protein forage is fed, less supplemental protein will be needed. This usually reduces

feed costs since most protein supplements are purchased. High-protein forages generally

are more digestible and provide more energy per pound than low-protein forages (Aerts

and Nesheim, 2002).

Fiber content of forages is inversely related to quality. Fiber can be measured many

ways, but the single best method for comparing different forages is neutral detergent fiber

(NDF) (Weiss et al., 1999). Acid detergent fiber (ADF) is determined frequently and is

useful in comparing and estimating forage quality within forage species, however it is not

a good measurement to compare quality among different forage species. Plant fiber is

composed largely of cellulose and hemicellulose. The amount of cellulose is relatively

constant among forage species, but the amount of hemicellulose differs greatly between

grasses and legumes. Cellulose is the primary constituent of ADF, but NDF contains both

cellulose and hemicellulose. Therefore, grasses and legumes may have similar ADF

values, but NDF values will almost always be substantially higher for grasses. Fiber

content and energy content are closely related since almost all researchers use fiber (either

ADF or NDF) to estimate available energy. Concentration of fiber is negatively related to

quality because forages with high concentrations of fiber contain less available energy

and are consumed in lesser amounts by cows than are forages with low amounts of fiber.








Bahiagrass

Bahiagrass (Paspalum notatum), a warm-season perennial, is grown throughout

Florida and in the Coastal Plain and Gulf Coast regions of the southern United States. At

least 70 percent of Florida pasture acreage is bahiagrass (Pate, 1992). In Florida,

bahiagrass is used on more land area than any other single pasture species, covering an

estimated 2.5 million acres (Chambliss, 2002; Arthington, 2000). Most of this acreage is

used for grazing with some hay, sod, and seed harvested from pastures. Bahiagrass is

adapted to climatic conditions throughout Florida and can be grown on upland

well-drained sands as well as the moist, poorly-drained flatwood soils of peninsular

Florida (Chambliss, 2002).

Bahiagrass is a warm-season grass that produces more grazing in summer than

winter. Due to the longer growing season, forage growth is more evenly distributed

throughout the year in southern Florida than in northern Florida. In southern Florida,

growth of bahiagrass pastures slows in October, and many pastures have very little forage

after mid-December until the grass starts growing again in early March. In northern

Florida, bahiagrass pastures are productive from April to November (Chambliss, 2002).

A major advantage of bahiagrass is persistence, even with little or no management

It grows well with limited amounts of fertilizer, usually 50 pounds of nitrogen (N)/acre

usually applied in the spring. This is an important practice to improve the amount and

quality of grazing at a critical time of year. For cows coming off winter pastures and onto

bahiagrass from March to May (a 90-day breeding season), it helps provide needed

nutrition to get lactating cows into a weight-gaining condition to increase their chances of

rebreeding. For cows bred from December to February, it provides nutrition to improve






15

lactating ability of cows and, hence, bigger calves. Whatever the situation, the results of

spring fertilization of bahiagrass are dependent on rainfall, which is often very little at

this time. Day length and temperature are not the limiting factors that they are in winter.

Crude protein in -fertilized bahiagrass in April is two to three percentage units

greater than that found in unfertilized grass (12 to 15 percent for fertilized versus nine to

12 percent for unfertilized grass) (Kalmbacher and Wade, 2003). Bahia has moderate

quality for most of the year, having 8 to 10 percent crude protein and about 50 percent

TDN, with little or no fertilizer. The lower the rainfall, the higher the crude protein

concentration in leaves because yields are lower and protein is more concentrated. By

June the difference in crude protein concentration between fertilized and unfertilized

grass is minimal (both will be eight to 10 percent). Across the April-to-June period,

crude protein in the total mass of grass produced during this period averages one to two

percentage units greater with N fertilization. Total digestible nutrients (TDN) in

bahiagrass will be increased by N fertilizer applied in March, but only by one to two

percentage units (Kalmbacher and Wade, 2003). It may be the best grass for small

ranches where grazing management is difficult and having a dependable grass is most

important (Pate, 1992).

Bahiagrass is popular with Florida ranchers because it: 1) tolerates a wider range of

soil conditions than other improved grasses; 2) has the ability to produce moderate yields

on soils of very low fertility; 3) is easily established from seed; 4) withstands close

grazing; and 5) is relatively free from damaging insects (except for mole crickets) and

diseases (Chambliss, 2002).






16

One major disadvantage of bahiagrass is that it will never obtain a consistently high

quality, regardless of management or fertilization practices. It is not a good grass as the

only forage for young cattle. Its quality particularly TDN, is low in the winter and

supplementation is needed for any class of cattle grazing bahiagrass during this period

(Pate, 1992). Other disadvantages of bahiagrass are that it is susceptible to mole crickets.

Bahiagrass is used mainly for beef cattle pastures. If it is fertilized, rotational grazing can

be sustained from approximately mid-March to mid-November. However in Northern

Florida, this period is slightly reduced (Chambliss, 2002). The quality of bahiagrass

forage is adequate for mature beef cattle, but weaned calves or stocker yearlings make

relatively low daily gains, especially from July through September (Chambliss, 2002).

Bermudagrass

Bermudagrass has excellent agronomic characteristics making it a popular perennial

forage grown in much of the southeastern U.S., including Florida. The grass has

high-yielding ability, high-drought resistance, and sufficiently tolerates highly-acidic soils

(Staples, 1995). There are several different hybrids of bermudagrass. Coastal, Alicia,

Callie, Tiflon 44, Tifton 78, and Tifton 85 are examples. Coastal was the first major

hybrid developed and occupies more acreage than all other hybrids combined. The Alicia

hybrid, has the lowest quality of the group. It is susceptible to rust disease. Rust diseases

are found throughout the U.S. on most species of grasses (Duble, 2004). Alicia is lower

yielding than Coastal, and is usually used as a last choice for planting (Staples, 1995).

Callie is good quality, being superior to the Coastal hybrid, but it is susceptible to rust in

the spring, which can reduce yield and quality, depending upon the extent of the rust

infestation. Tifton 44 is the most winter-hardy of the group, but its forage quality is






17
lower than other newly developed hybrids. Utley et al., (1978), conducted a study

comparing Tifton 44 and Coastal bermudagrass as pastures and as harvested forages.

Utley et al. (1978) reported that the average daily gain of steers grazing Tifton 44

bermudagrass was 19% greater than steers grazing on Coastal pastures. When pellets

made from Tifton 44 and Coastal forage of comparable chronological age were fed, steers

given the Tifton 44 pellets gained 19% more on 16% less fed. Tifton 78 has been shown

to produce the highest quality forage but establishment has been a problem for many

producers (Staples, 1995). Tifton 85 bermudagrass is the fastest growing, tallest, and

largest stem hybrid of the group. A study conducted by Hill et al. (1993) showed that

when compared to Tifton 78 in a 3-year grazing study using steers, Tifton 85 supported

equal body weight gains and more grazing days per acre.

Bluegrass

Characterized by Kentucky bluegrass, these non-legumes are common in the

northeastern quarter of the United States, where there are cooler conditions with adequate

rainfall. Bluegrass is adapted to better-drained loams of limestone origin, such as those in

Virginia and Kentucky. One of the disadvantages to this pasture grass is the marked

periodicity in growth and development: greatly reduced production occurs from mid-July

through August (Cecava, 1995). It is well adapted to mixtures with legumes, especially

the white clovers and birdsfoot trefoil, but it is too competitive with alfalfa and red

clover. Following its dormancy period in late summer, it responds to Fall rains and

produces well in September and October. Unpastured bluegrass that is allowed to grow

and fall over is a most excellent forage crop for beef cattle in the late fall months

(Cecava, 1995).








Bromegrass

These grasses are adapted to cool climates or to regions in which cool seasons

prevail for a portion of the season. The Greek derivative Bromus signifies oats and thus

the name oats grass often has been applied. There are at least 60 varieties ofbromegrass;

the most common is smooth bromegrass. It is fairly resistant to drought, but in severe

drought it becomes dormant much the same as other grasses. Smooth brome is used both

alone and in mixtures with other grasses and legumes. In mixtures with legumes, the first

cutting often goes for hay, followed then by grazing. Bromegrass is one of the most

palatable of the grasses and maintains its palatability and nutritive value at much later

stages of growth than most grasses, except perhaps bluegrass (Cecava, 1995).

Timothy

Timothy is adapted to a cool and humid climate, and thus it is restricted primarily to

the northeastern portion of the United States. It is grown primarily for hay but is

generally included in pasture seeding mixtures, especially with clover. Such mixtures are

generally harvested in the first growth of the year for hay, at the time the timothy heads

bloom. Subsequently it can be grazed as a pasture mixture. Young, succulent timothy is

often relished more than bluegrass by livestock. Timothy is gradually crowded out of

permanent pasture by bluegrass (Perry and Cecava, 1995).

Fescue

The fescue group has a wide distribution but the greatest concentration of growth is

in the southeastern United States and along the coasts of Oregon and Washington. In the

southeast, fescue is especially important as a winter pasture crop and does not persist as

well in the hot summer environment. Fescue establishes one of the strongest sods which






19

is thus resistant to breakthroughs from grazing traffic. Its winter growth habits make it

important in a grazing program designed for year-round use (Cecava, 1995). Fescue

pastures can tolerate more grazing abuse than any other pasture sod. Heavily overgrazed

pastures seem to come back with excellent growth after cattle are removed (Cecava,

1995).

A disadvantage of feeding fescue is that at certain phases of their growth the

fescues become rather unpalatable and cattle will not eat them unless forced (Cecava,

1995). This is caused by an endophyte fungus (Acremonium coenophialum) which

infects the fescue plant. The fungus has no adverse effects on the plant itself but can

cause toxicity in animals grazing infected pastures. There is also the matter of "fescue

foot". This is a condition in which animals grazing fescue tend to become lame. They

eventually develop a deformed hoof which may slough off. Establishment of 15-30%

legumes in a fescue pasture appears to counteract the periodic toxic aspects of fescue

pasture for beef cattle (Perry and Cecava, 1995).

Sorghums

Sorghums for pasture are perhaps best typified by sudan grass and hybrids thereof.

The sorghum plants are resistant to drought and thus, they are grown primarily in the

southern Great Plains area. Sudan grass grows most rapidly in hotter weather when most

other pasture crops are dormant (Cecava, 1995). Cattle relish sudan grass. Sudan grass is

especially adapted to rotation grazing; while one plot is recovering from having been

grazed, the other is being grazed into the ground. Sudan grass stores energy in its roots,

thus there is no danger to the plant in grazing it down to the ground (Cecava, 1995).






20

A disadvantage to grazing sudan grass is there is always the potential danger of

prussic acid poisoning for cattle. The most critical times for this are in the early stages

(two- and three-leaf stages) or immediately after the plants have been frosted or frozen.

Mature sudan grass or that which has been cut for hay or silage has no danger for

poisoning cattle (Cecava, 1995).

Alfalfa

Alfalfa, or lucerne, as it is called in many parts of Europe, is well adapted to a wide

range of climatic and soil conditions. It responds to fertilization and water along with

good cultural practices, including inoculation with nitrogen-fixing bacteria. It is one of

the most important forage plants in the United States because it has the highest feeding

value of commonly grown forage crops. It produces more protein than that of clover and

many times that produced by the nonlegumes (Perry and Cecava, 1995). Alfalfa, if

harvested in the late bud stage of maturity, can contain 20 to 25% CP on a dry matter

basis (DM basis). If it is harvested in late maturity it can contain 10 to 14% CP (DM

basis). Grasses, if fertilized properly and harvested in the vegetative stage of maturity,

can have more than 20% CP. An exception to this general relationship is corn silage,

which is low in CP but is a high-quality forage because of its energy content (Weiss et al.,

1999). High-quality alfalfa will contain 35 to 40% NDF (25 to 30% ADF), and

high-quality grasses will contain 55 to 60% NDF (30 to 35% ADF). Low-quality grasses

can contain 70 to 80% NDF (Weiss et al., 1999).

Alfalfa is not used commonly as the sole pasture crop for beef cattle because of its

bloat-causing effect It is much more satisfactory as a pasture crop for beef cattle when it

is grown in a mixture with nonlegumes, such as bromegrass or orchardgrass, or even






21

bluegrass. Alfalfa can be prone to insect infestation and a variety of diseases associated

with bacterial infections so it is often difficult to maintain a stand of alfalfa (Perry and

Cecava, 1995).

Bur Clover/Spotted Bur Clover

These are relatives of alfalfa. They are weak stemmed plants resembling clovers.

California bur clover contributes to the range pastures of the California and Arizona

foothills. In the southeastern states, spotted bur clover is the primary species. All bur

clovers are unable to stand the rigors of winter and thus are restricted to more temperate

climates (Perry and Cecava, 1995). In the western states, bur clover comes up as a

"volunteer" in range pastures whereas in the southern states spotted bur clover must be

seeded. However, once seeded, stand life is indefinite (Perry and Cecava, 1995).

Red Clover

Red clover grows abundantly in the midwest, as well as in the entire northeastern

quarter of the United States. Furthermore, it grows well as a winter annual in the

southeastern United States, and under irrigation in the six or seven far western states.

Red clover is seldom used as the sole pasture crop but rather is grown in mixtures with

grasses (Perry and Cecava, 1995).

Alsike Clover

Alsike clover is a perennial which contributes to cattle pasture mixtures. Because

of its adaptation to wet soils, Alsike is good for establishing pasture sod on wet natural

meadows or where irrigation is used. It may persist in bottomlands along creeks or rivers

where alfalfa and red clover are unable to survive. It is well adapted to cool climates. It






22

can tolerate greater soil acidity than clover or alfalfa, but nevertheless responds to

limestone applications (Perry and Cecava, 1995).

White Clover

These are perennials and are grown widely throughout the world. This group is one

of the most nutritious and palatable of all the legumes. The white clovers are usually

grown in association with other legumes or with grass, or with complex mixes of both. It

also occurs as weeds of lawns, turfgrass, landscapes and orchards. The white clovers

usually appear as volunteers, especially in the cooler northern pastures (Cecava, 1995).

White clover pasture is not very desirable as a horse pasture because it causes excessive

salivation or "slobbering" of horses (Perry and Cecava, 1995).

Birdsfoot Trefoil

Essentially grown in the northeastern quarter of the United States and also along a

narrow strip of the west coast, birdsfoot trefoil has not had a wide acceptance as a pasture

legume because of the extremely slow development of its seedlings; in mixtures with

clovers and grasses, birdsfoot is not able to compete (Cecava, 1995). It has some

resemblance to alfalfa. However, no cases of cattle bloat are known to have occurred on

birdsfoot trefoil (Cecava, 1995). It has a wide soil tolerance to fertility and acidity. It is a

perennial which reseeds itself, even when grazed closely. It is especially compatible with

Kentucky bluegrass, and may stay in existence and in balance for many years (Perry and

Cecava, 1995).

Vetches

The vetches are most common in the southeastern quarter of the United States.

Some 150 species are known, about 25 of which are native in the United States. There






23

are several varieties of vetch including hairy, madison, common, Hungarian, narrowleaf,

purple, and bard. They are especially well adapted as cover crops for land exposed in

highway construction because of their matting characteristic. They are usually considered

winter annuals, reseeding themselves each year. During the winter period of the year,

land in the southern states is not occupied with cash crops such as cotton or peanuts, and

thus the vetches are excellent crops at that time. All vetches are edible and palatable to

cattle but only those with hard seed and good seeding habits are recommended for use in

permanent pastures. Vetches may become troublesome weeds in grain fields but are

readily controlled with herbicides. These include hairy and smooth vetches (Perry and

Cecava, 1995).

Concentrates and Supplements

Cattle have the capacity to utilize tremendous quantities of roughage because of the

anaerobic microorganisms found in the rumen. Cattle subsisted primarily on forages and

roughages as sources of energy and other nutrients for centuries. However, man

domesticated cattle and introduced concentrated energy and protein feedstuffs into the

ruminant diet. Concentrate feeding was and continues to be attractive from an economic

standpoint. Cereal grains and animal and plant proteins can often be used to supply

energy and protein at lower cost per nutrient input compared with forages (Cecava, 1995).

Supplements are often fed to heifers and steers after weaning until winter pasture is

ready for grazing. Grain supplements such as corn will improve gains of calves grazing

residual pasture or fed hay. Several by-product feeds are also available in Florida and

often are lower-cost sources of energy and other nutrients than corn and other grains.






24

Feeds such as molasses, whole cottonseed, citrus pulp, soybean hulls, wheat midds and

hominy are available in many areas of Florida (Kunkle et al., 2004).

The major source of energy concentrates for cattle is cereal grains, primarily corn,

grain sorghum, barley, oats, and wheat. The major sources of plant protein concentrates

include the oilseed meals (i.e., soybean, cottonseed, and linseed) and by-products of

cereal grain processing, such as corn gluten meal, corn gluten feed, distiller's grains, and

brewer's grains. The major sources of animal protein concentrates are by-products of the

animal processing industry. These include bloodmeal, meat and bone meal, fishmeal, and

poultry feathermeal.

Quantitatively, corn grain is the most important cereal concentrate fed to livestock

in the United States. As would be expected, the majority of grain consumption by beef

cattle occurs in the feedlot Almost 90% of all cattle on feed are located in 13 states

found primarily in the Midwest or high plains regions of the country, where grain is

plentiful (Cecava, 1995).

All of the cereal grains are high in starch and low in fiber. They are rich in energy

and generally quite palatable. The highest concentrations of digestible energy are found

in corn, grain sorghum, and wheat. Lower energy concentrations are found in barley and

oats. Generally, the balance of amino acids is poor for the cereal grains. Notably, grains

tend to be deficient in lysine and tryptophan. Corn is especially low in total protein,

averaging 7.8 to 9.0% protein on a dry matter basis whereas barely and grain sorghum

may contain 12% protein or greater. Cereal grains are extremely low in calcium but

almost adequate in phosphorous relative to the needs of growing cattle (Cecava, 1995).






25

Lipids also represent a source of energy used in beef cattle diets. The rendering

industry is a source of tallow and lard (grease) commonly fed to growing and finishing

cattle. Substantial amounts of lipid from vegetable sources, such as soybean oil, are also

used (Loest et al., 2001; Cecava, 1995).

Whole Cottonseed

Whole cottonseed is a by-product of cotton production. Whole cottonseed can be

fed to ruminants or processed for its oil content, and an increasing proportion has been

fed in recent years. Whole cottonseed is high in TDN (94%) and crude protein (23%) and

is a good feed for cattle (Kunkle et al., 2004). Cottonseed is light, with a weight of 9 to

11 kg/0.03 m3 (20 to 25 lb/ft3). It is usually transported in dump trailers or trucks with a

bottom conveyor. It can also be transported and stored in peanut drying wagons.

Cottonseed must be dry or it will mold during storage. Cottonseed does not need to be

processed and can be mixed in diets or fed in feedbunks or on a clean sod. At first

offering, whole seed may need to be mixed with other ingredients, but after adaptation

cattle will usually consume it readily. Feeding cottonseed at a level to meet the

supplemental protein needs of growing cattle and beef cows is common (Kunkle et al.,

2004). Cottonseed can also be fed as an energy supplement depending upon economic

feasibility (Kunkle et al., 2004).

Feeding cottonseed to beef cattle does have disadvantages as well. Due to the high

fat content (18%) and gossypol, a toxic pigment obtained from cottonseed oil, whole

cottonseed should be limited to roughly 25% of the total dry matter intake of beef cattle

(Kunkle et al., 2004).








Cottonseed Meal

Cottonseed meal is a high protein by-product from the extraction of oil from whole

cottonseed. Cottonseed meal is palatable and commonly is used in cattle rations in the

southern and western U.S. (Kunkle et al., 2004). Cottonseed meal is used as a protein

supplement and can replace all of the soybean meal in the ration. Cottonseed meal

contains gossypol, which is a toxic pigment obtained from cottonseed oil and is

detoxified by heating. Although cottonseed meal contains gossypol, under typical

conditions where protein supplement is given, even high-producing cows will not

consume enough cottonseed meal to suffer from gossypoltoxicity (Kunkle et al., 2004).

Cottonseed meal contains approximately 41.5% crude protein, 1.5% fat, 12.5% crude

fiber, and has a 70% TDN (Cecava, 1995). Brown and Pate (1997) reported Brahman

crossbred yearling steers fed ammoniated hay plus a liquid cane molasses based

supplement containing cottonseed meal and urea, or feather meal and urea gained more

weight and were more efficient than steers supplemented with urea only.

Citrus Pulp

Citrus pulp is a by-product of the orange- and grapefruit-processing industries, with

over 500,000 tons produced annually in Florida. Citrus pulp has a 79% TDN and 8%

crude protein concentration, making it a good energy supplement for cattle. Most citrus

pulp is dried, and much of the supply was exported to Europe during the 1980s. Supplies

are available during the citrus-processing season with prices fluctuating with the

international market. Wet citrus pulp is available seasonally during periods of heavy

harvest and may be an economical supplement for cattle within 30 miles of the processing

plant (Kunkle et al., 2004).






27

Most dried citrus pulp is ground and pelleted, which nearly doubles its bulk density

and improves its handling characteristics. It is sensitive to moisture and needs to be dry

when stored. Pelleted citrus pulp will usually flow in storage bins and self feeders and

can be mixed with other feed ingredients. Citrus pulp is very palatable to cattle and will

improve the intake of some rations. Wet citrus pulp (15 to 20% dry matter) is acid and

can be stored for short periods. Most wet citrus pulp is fed by dumping piles in pastures

and allowing cattle to consume it, which results in some spoilage and wasted pulp

(Kunkle et al., 2004).

Molasses

Another supplement that can be used for beef cattle is molasses. Molasses is a by-

product of the sugar, wood and citrus processing industries. Cane and beet molasses are

by-products of sugar manufacturing from sugar cane and sugar beets, respectively,

whereas citrus molasses is produced from the juice of citrus waste. Wood molasses is

produced during paper manufacturing (Cecava, 1995). Cane molasses is extremely

palatable to beef cattle, and is often included for its dust-settling effect and for the

pleasant aroma it imparts to feeds. Cane molasses can be offered on a free-choice basis

or it may be incorporated into a portion of the ration, as in the protein supplement, or into

the total ration. When molasses is included in dry diets, it is usually restricted to less than

10 to 15% of the diet on a dry matter basis because diets containing higher amounts are

difficult to handle and may cause digestive disturbances (Cecava, 1995).

Soybean Hulls

The soybean hull is the seed coat removed during oil extraction. It is usually toasted

and ground after removal and may be added back to the meal. Soybean meal with 48%






28

crude protein does not have the hulls added back after processing, and 44% soybean meal

contains the hulls. Soybean hulls are high in fiber that is highly digestible by ruminants.

Soybean hulls contain 77% TDN, 12% crude protein and 14% starch. The low starch

concentration results in a lower rate of fermentation and reduces problems with acidosis

(Kunkle et al., 2004).

Unpelleted soybean hulls are light and bulky with a weight of 9 kg/0.03 m3 (20

lb/ft3). Pelleted soybean hulls have a higher bulk density. They are usually stored in

flat-bed storage and loaded with a front-end-loader. They are very palatable to cattle and

are a good feed for newly weaned calves. The protein, calcium and phosphorus is usually

adequate and nearly balanced, making soybean hulls a commodity that can be fed without

mixing with other feeds. They have also been used to supplement bulls since soybean

hulls are palatable and their low starch concentration reduces the chance of acidosis and

founder. When used as a supplement with forage, soybean hulls have less of a depressing

effect on forage intake and digestibility, and usually result in better cattle gains than cattle

fed similar amounts of TDN from grains (Kunkle et al., 2004).

Cotton Gin Trash

Cotton gin trash contains mostly cotton lint with some pieces of stems, immature

seeds, and other cotton plant parts harvested with the cotton. It is a waste product at

cotton gins and often is hauled to landfills. Typically cotton gin trash has an energy

concentration similar to mature bahiagrass hay and protein is typically 10% or higher. It is

best suited as a feed source for mature dry beef cows and is usually available for the cost

of hauling from the cotton gin. Cotton gin trash is bulky and often hauled in trucks with

live bottoms and unloaded in the fields where it is fed to cattle. It smells good and is very






29

palatable to cattle. Cotton gin trash is limited in energy, and additional supplements may

be needed to avoid body condition loss and improve cattle performance (Kunkle et al.,

2004).

Urea

Urea is a non-protein nitrogen (NPN) compound. Urea supplies part of the protein

equivalent in many of the commercial supplements formulated for beef cattle today.

When soybean meal and other plant proteins are high in price, more urea is used to

replace plant protein in the ration of beef cattle and sheep (Sewell, 2006). The simple

urea compound contains 46.7 percent nitrogen. Most of the urea used in livestock feeds

has 45 percent nitrogen, but some has 42 percent (Sewell, 2006). Feed grades of urea

have less nitrogen than the pure compound because the particles of urea are coated with

clay or treated with formaldehyde or other material to prevent caking and lumping.

Cattle, sheep and other ruminants can use urea to replace part of the protein in their diet

because of the host of microorganisms (bacteria and protozoa) present in their rumen. In

their multiplication and growth, rumen microorganisms use the ammonia released from

the breakdown of protein and non-protein nitrogen compounds (urea, etc.) to manufacture

microbial protein. The bacteria and protozoa produced in the rumen pass further down the

digestive tract and are digested, making the proteins from their cells available to the host

animal (Sewell, 2006).

Shain et al. (1998) reported that supplementing crossbred yearling steers with 0.88,

1.34, and 1.96% urea had no effect on dry matter intake, average daily gain, or feed

efficiency. However, steers fed diets supplemented with urea were 5.4% more efficient

and gained 6.6% faster than steers receiving no supplemental urea (Shain et al., 1998).






30

Feed Additives

The proper nutrition of beef cattle is a key component of a successful production

system. Feed usually accounts for the single largest input cost associated with beef cattle

production (Hamilton, 1991). Increased demand for leaner beef and consumer resistance

to beef with a high fat content have necessitated interest in the effects of feeding strategy

on the carcass composition of beef cattle (Steen and Kilpatrick, 1995).

One management strategy for reducing feed costs and improving gain is the use of

feed additives. Their primary effects are to improve feed efficiency and/or daily gain.

Some feed additives have secondary benefits which include reducing the incidence of

acidosis, coccidiosis, and grain bloat, while others suppress estrus, reduce liver abscesses,

or control foot rot problems.

Each feed additive has its own characteristics and feeding limitations. Some are

approved to be fed in combination with others. Using the proper level of feed additives is

very important because excessive levels will decrease animal performance, especially

with cattle on low-quality roughages.

Antibiotics

One type of feed additive is antibiotics. In domestic animals antimicrobial agents

are used for three major purposes: therapy to treat an identified bacterial infection,

prevention of bacterial infections in animals at risk, or as feed additives to enhance

performance (van den Bogaard and Stobberingh, 1999). Veterinary antibiotic therapy

involves treatment of an individual animal or a group of sick animals with one or more

antibiotics during a defined period of time, and in most Western countries, only upon

prescription from a veterinarian. Similarly, antibiotics can be prescribed by a veterinarian






31

for a defined period of time to prevent the spread of an existing infection in a herd. In the

situations when antimicrobials are used for therapy or for prevention of disease in a group

of animals, antibiotics are mostly dissolved in the drinking water or milk, or mixed in the

feed. This is called group or mass medication (van den Bogaard and Stobberingh, 1999).

Apart from veterinary use, antibiotics are added to the feed of animals used as a food

source (i.e. "food animals") for humans (e.g. pigs, poultry and cattle), to enhance their

performance and increase growth (van den Bogaard and Stobberingh, 1999; Schroeder et

al., 2002 ). In this situation they are considered antimicrobial growth promoters (AGP).

The term growth promoter is used for feed additives, other than dietary nutrients, which

increase growth rate and/or improve feed efficiency in healthy animals fed a balanced diet

(van den Bogaard and Stobberingh, 1999). Antimicrobial growth promoters are more

effective in young than in older animals. The general opinion is that the observed growth

and feed efficiency responses to the use of AGP are lower under optimal hygienic and

animal husbandry conditions compared with poorer environments (Rosen, 1995; van den

Bogaard and Stobberingh, 1999). Despite the fact that AGP are not intended for and not

registered for prevention of bacterial diseases, a part of their positive effect is most likely

caused by prevention or suppression of bacterial infections. This might be an explanation

of why they are more effective in young animals and when used under suboptimal

conditions. Other names for AGP are antimicrobial performance enhancers,

antimicrobial feed additives, feed savers, digestion enhancers or intestinal flora

modulators (van den Bogaard and Stobberingh, 1999).

In the 1950's, microbiologists began to detect bacteria that were resistant to

antibiotics, and these resistances were spread from one bacterium to another on extra-






32

chromosomal elements called plasmids (Russell and Houlihan, 2003). Resistance to

antimicrobial drugs can arise either from new mutations in the bacterial genome or

through the acquisition of genes coding for resistance. These genetic changes alter the

defensive functions of the bacteria by changing the target of the drug, by detoxifying or

ejecting the antibiotic, or by routing metabolic pathways around the disrupted point

(Witte, 1998). Antimicrobial-resistant bacteria from food animals may colonize the

human population via the food chain, contact through occupational exposure, or waste

runoff from animal production facilities (Witte, 1998; van den Bogaard and Stobberingh,

1999; Schroeder et al., 2002). Food animals, in particular mature cattle, which may be

asymptomatic carriers of E. coli 0157:H7, when exposed to antimicrobial agents in the

animal production environment, may serve as a reservoir of antimicrobial resistant

bacteria (Schroeder et al., 2002).

Antibiotics have been used to improve gain and feed efficiency of cattle.

Antibiotics are added to feed to minimize secondary bacterial infections and to control

liver abscesses. Some of the antibiotics available include chlortetracycline,

oxytetracycline, bacitracin, and tylosin.

Beef cattle are commonly fed a class of antibiotics known as ionophores.

Ionophores alter rumen fermentation characteristics, as well as inhibit the growth of

specific rumen microorganisms. The result is improved feed efficiency at the same or

higher level of gain compared to a diet without ionophores. Several authors have

reported that ionophores can increase feed efficiency by as much as 10% (Goodrich et al.,

1984; Russell and Strobel, 1989). Ionophores alter rumen fermentation in three major

ways. First an improvement in the efficiency of energy metabolism occurs by changing






33

the types of volatile fatty acids produced in the rumen thus decreasing energy lost during

fermentation of the feed. Improved animal performance results from increased energy

retention during fermentation in the rumen. Second, ionophores decrease the breakdown

of feed protein and may also decrease microbial protein synthesis. This has minimal

effects on the performance of cattle on high-grain diets, but may have important

implications with growing cattle fed high-roughage diets. Third, ionophores may reduce

the incidence of acidosis, grain bloat, and coccidiosis. Reducing these stresses should

result in improved animal performance (Goodrich et al., 1984; Russell and Strobel,

1989). With high-grain diets, ionophores generally decrease feed intake, improve feed

conversion, maintain or increase daily gain, and do not affect carcass characteristics.

When cattle in confinement (feedlot) are fed diets containing large proportions of

roughage, ionophores improve daily gain and feed conversion. Feed intake of animals fed

high-roughage diets do not change if the proper level of ionophore is fed (Goodrich et al.,

1984; Russell and Strobel, 1989).

Important ionophores include monensin, lasalocid, salinomycin, and narasin. At

present, monensin (RumensinT") and lasalocid (Bovatecc") are the only ionophores

approved to be fed to beef cattle. The ionophores RumensinTm and Bovatec'" are

probably the most familiar ionophores for producers because they have been on the

market for a relatively long time.

Ionophores are lipophilic compounds that are toxic to many bacteria, protozoa,

fungi, and higher organisms (Russell and Strobel, 1989). Their mode of action is their

ability to penetrate into biological membranes and subsequently alter the flux of ions

from and into the cell. They attach to the lipid bilayer of the cell membrane of ruminal






34

gram-positive bacteria and protozoa (Chow et al., 1994; Ipharraguerre and Clark, 2003).

Once at the membrane interface, they interfere with the flux of ions either by forming

cyclic ion-ionophore complexes that function as ion-selective mobile carriers (e.g.

monensin and lasalocid) (Bergen and Bates, 1984; Russell and Strobel, 1989) or by

creating pores that promote a less specific influx and efflux of ions (e.g. gramicidin)

(Russell and Strobel, 1989). More specifically, they facilitate the net exchange of

intracellular K' for extracelluar protons and Na across the membrane. This forces gram

positive microorganisms to expel protons and Nae at the expense of adenosine

triphosphate (ATP), causing a depletion in the energy reserve, impaired cell division and

likely death of the microorganism (Russell and Strobel, 1989). The net effect is a change

in the microbial ecosystem of the rumen favoring mostly gram negative microorganisms

that are not sensitive to ionophores (Russell and Strobel, 1989). The effect of ionophores

on the rumen volatile fatty acid profile is an increased proportion of propionate to acetate

in the rumen. There is also a depression in methane (CH4) production.

Ionophores are fed to approximately 90% of all feedlot cattle in the U.S. They are

particularly beneficial for cattle fed high grain (less than 12% roughage) diets because of

their role in reducing acidosis and bloat. Ionophores may not improve feed efficiency in

diets with greater than 4% tallow, but they would still be effective insurance against

acidosis and bloat.

In recent years, there has been a keen debate concerning the causes of antibiotic

resistance and steps that should be taken (Lewis et al., 2002). This debate has been

sharply divided between two major groups: 1) physicians and veterinarians who use

antibiotics therapeutically to treat acute disease and 2) livestock producers who feed






35

antibiotics sub-therapeutically to promote (enhance) animal growth. Physicians argue

that the routine use of antibiotics in animal feed creates a selection pressure for

resistances that eventually spread to man. Agriculturists counter that resistance is more

apt to appear when physicians and veterinarians misdiagnose infections and improperly

administer antibiotics. When antibiotics are misused in this latter fashion, the dosage is

greater, and the environment already has a large population of pathogens (e.g. hospitals)

(Russell and Houlihan, 2003). Ruminal bacteria resistant to one ionophore can also be

resistant to other ionophores (Russell and Strobel, 1989) but until recently the mechanism

of this resistance was not well defined (Russell and Houlihan, 2003). Ionophores are

technically considered antibiotics and for this reason, some groups have called for a ban

on their use and argue that ionophore resistance poses the same public health threat as

conventional antibiotics (Russell and Houlihan, 2003).

Schroeder et al. (2002) studied the antimicrobial resistance of E. coli 0157 isolates

from humans, cattle, swine and food to better understand the prevalence of antimicrobial

resistance among these organisms. The authors used a total of 361 isolates, with 36%

recovered from humans, 37% recovered from cattle, 19% recovered from swine, and 8%

recovered from food. A total of 7 different classes of antimicrobials were used;

Cephalosporins, Penicillins, Sulfonamides, Quinolones and fluoroquinolones, Phenicols,

Aminoglycosides, and Tetracyclines. The authors reported that 61% of the isolates

analyzed during the study were susceptible to all the antimicrobials assayed. However,

7.5% were resistant to one antimicrobial, 17% were resistant to two, 8% were resistant to

three, 5% were resistant to four, 2% were resistant to five and 0.1% were resistant to six.

Among the 361 isolates tested, the authors reported that 27% were resistant to






36
tetracycline, 26% were resistant to sulfonamides, and 23% were resistant to both

antimicrobials (Schroeder et al., 2002). Of these co-resistant isolates, 57% were from

swine, 19% were from cattle, 17% were from humans, and 7% were from food. Although

sulfa drugs and tetracycline are approved for use in cattle, the authors could not determine

conclusively whether the high rates of resistance observed among the isolates could be

attributed to the use of these drugs in cattle production (Schroeder et al., 2002).

Microbiology

Ruminant animals are populated by a microbial consortium that allows the animal

to convert cellulosic forages to high quality meat, milk, or fiber (Hungate 1966). The

microbial population of the ruminant is very diverse and microbes are found throughout

the rumen, as well as the gastrointestinal tract (Hungate 1966).

In the past, muscle tissue in the living and growing animal was thought to be sterile,

or nearly so, with the exception of the lymph nodes (Romans et al., 1994). There are

several types of microorganisms that can grow in/on beef. Bacteria are clearly the most

predominant and important (Romans et al., 1994). Molds and yeasts are another type of

microorganism (fungi) that are of minor importance in meat. Molds are more apt to cause

spoilage or pose a health hazard in other types of foods although they have been shown to

grow on meat products (Nuru et al., 1971). Yeasts may be involved in the spoilage of

food products that contain high amounts of sugar, but since meat has only approximately

1% sugar or carbohydrates, yeasts are generally not a problem in meat. However, yeast

have been isolated on rare occasions in beef cattle (Nuru et al.,1971; Romans et al.,

1994).






37

Microorganisms of Concern in Beef Cattle Food Safety

General Microflora

Potential bacteria that can be found in beef cattle pre-harvest to fabrication include

(in no particular order): Enterococcus sp, Pseudomonas sp, Micrococcus sp, Fecal

Coliforms, Corynebacterium sp, Streptomyces sp, Streptococcus faecalis, Staphylococcus

aureus, Bacillus sp, Lactobacillus sp, Clostridium perfringens, Salmonella sp, and

Escherichia coli (Collier and Rossow, 1964; Nuru et al., 1971; Hood and Zottola, 1997).

Nuru et al. (1971) reported very little differences in the microflora populations present in

the feces of cattle and pigs. E. coli are rarely cultured in high numbers from the rumen of

cattle (less than 10' cells/ml out of a population of 10" cells/ml) (Wolin, 1969). They

can be found at concentrations from 102 to 107 cells/g of feces at slaughter (Davidson and

Taylor 1978).

Characteristics of Escherichia coli

Escherichia coli is one of the most widely spread types of microorganisms in nature

(Romans et al.,1994). E. coli is a straight rod measuring 1.1 to 1.5 pm by 2.0 to 6.0 pm

which occur singly or in pairs and has an optimum growth temperature of 37C. Capsules

or microcapsules occur in many strains and some strains are motile by means of a

flagella. E. coli is a facultative anaerobic bacterium that is a normal inhabitant of the

mammalian intestinal tract (Drasar, 1974). E. coli is commonly found in human and

animal intestinal tracts and, as a result of fecal contamination or contamination during

food animal slaughter, it is often found in soil, water, and foods (Schroeder et al., 2002).

Many E. coli strains are harmless and even beneficial to the host; however, some strains

such as E. coli 0157:H7 are pathogenic and cause diarrheal illness (Callaway et al.,






38
2003). The strains of E. coli that cause disease are grouped on the basis of clinical

syndromes, virulence properties, mechanisms of pathogenicity, and distinct O:H

serogroups (Doyle et al., 1997).

E. coli isolates are serologically classified on the basis of three major surface

antigens: 0 (somatic), H flagellaa) and K (capsule). The serogroup of the strain is

identified by the 0 antigen and its combination with the H antigen identifies the serotype.

There are several different types of E. coli that have the potential to cause

gastrointestinal disease in humans. They are enteropathogenic (EPEC), enterotoxigenic

(ETEC), enteroinvasive (EIEC), diffuse-adhering (DAEC), and enterohaemorrhagic

(EHEC) (Gorbach 1986; Doyle et al., 1997). The enteropathogenic E coli (EPEC) strains

attach to the brush border of intestinal epithelial cells and cause a specific type of cell

damage called effacing lesions. Effacing lesions or attaching-effacing (A/E) lesions

represent destruction of brush border microvilli adjacent to adhering bacteria. This cell

destruction leads to diarrhea by improper absorption (Prescott et al., 1999).

The enterotoxigenic E. coli (ETEC) strains produce one or both of two distinct

enterotoxins which are responsible for the diarrhea and distinguished by their heat

stability: heat-stable enterotoxin (ST) and heat labile (LT) enterotoxin. ST binds to a

glycoprotein receptor that is coupled to guanylate cyclase on the surface of intestinal

epithelial cells. Activation of guanylate cyclase stimulates the production of cyclic

guanosine monophosphate (cGMP), which leads to the secretion of electrolytes and water

into the lumen of the small intestine, manifested as the watery diarrhea characteristic of

an ETEC infection. Heat labile enterotoxin (LT) binds to specific gangliosides on the

epithelial cells and activates membrane bound adenylate cyclase which leads to increased






39
production of cyclic adenosine monophosphate (cAMP). The result of this increased

production of cAMP is hypersecretion of electrolytes and water into the intestinal lumen

(Prescott et al., 1999).

The enteroinvasive E. coli (EIEC) strains cause non-bloody diarrhea and dysentery

similar to that caused by Shigella spp. by penetrating and multiplying within the intestinal

epithelial cells. As is the case for Shigella spp., the invasive capacity of EIEC is

associated with the presence of a large plasmid (140 MDa) which encodes several outer

membrane proteins (OMP's) involved in invasiveness. The principle site of bacterial

localization is the colon, where EIEC invade and proliferate in epithelial cells, causing

cell death (Doyle et al., 1997; Prescott et al., 1999).

The diffusely adherring E. coli (DAEC) strains adhere over the entire surface of

epithelial cells and usually cause disease in immunologically compromised or

malnourished children (Prescott et al., 1999). These strains can produce mild diarrhea

without blood or fecal leukocytes and are identified by a characteristic diffuse-adherent

pattern of adherence to Hep-2 or HeLa cell lines. DAEC generally do not produce heat

stable or heat-labile toxins or elevated levels of Shiga toxins. They also do not invade

epithelial cells (Doyle et al., 1997; Prescott et al., 1999).

The enterohemorrhagic E. coli (EHEC) strains carry the genetic determinants for

attaching-effacing lesions and Shiga-like toxin production. The attaching-effacing lesion

causes hemorrhagic colitis with severe abdominal pain and cramps followed by bloody

diarrhea. The Shiga-like toxins I and II (also called verotoxins I and 2 due to their being

cytotoxic to African green monkey kidney (Vero) cells) have also been implicated in two

extraintestinal diseases; hemolytic uremic syndrome and thrombotic thrombocytopenic






40
purpura (Prescott et al., 1999; Callaway et al., 2003). The major foodbome pathogen

associated with the EHEC group is the serotype 0157:H7. Although several E. coli

strains (i.e. 0111,026) can cause hemorrhagic colitis in humans, the most notable strain

is 0157:H7.

Studies have indicated that a reduction in concentration of E. coli in the intestinal

tract of cattle may be achieved on the basis of diet manipulation (Diez-Gonzalez et al.,

1998). However there are still differing opinions on whether this is possible (Hancock et

al., 1999; Duncan et al., 2000). Diez-Gonzalez et al. (1998) reported that when cattle

were abruptly switched from a 90% grain finishing ration to a 100% hay diet, fecal E. coli

populations declined 1000-fold. The population of E. coli resistant to an "extreme" acid

shock declined more than 100,000-fold within 5 days (Diez-Gonzalez et al., 1998).

Escherichkia coU 0157:1H7

The first confirmed isolation of Escherichia coli 0157:H7 in the United States was

in 1975 from a California woman with bloody diarrhea. The bacterium was first

identified as a human pathogen in 1982, when it was associated with two foodborne

outbreaks of hemorrhagic colitis (Karmali et al., 1983; Riley et al., 1983). E. coli

0157:H7 is a small, gram negative, non-sporing, straight rod. This pathogen is a

facultative anaerobe and can therefore grow in the presence or absence of oxygen

(Acheson, 2000). This pathogen can be encountered through the fecal oral route or

through human to human transmission. It is highly acid resistant and has a low infectious

dose of less than 100 cells and possibly as few as 10 cells. E. coli 0157:H7 causes over

73,000 illnesses in the United States each year resulting in approximately 60 deaths






41
(Callaway et al., 2003). Enterohemorrhagic E. coli infections are estimated to cost the

United States economy approximately $1 billion per year (USDA:ERS, 2001).

Most strains of E. coli 0157:H7 possess several characteristics uncommon to most

other E. coli such as the inability to grow well, if at all at temperatures of 44.5C,

inability to ferment sorbitol within 24 hr, and inability to produce 13-glucuronidase (Doyle

et al., 1997). It possesses a 60 MDa plasmid, and has an attaching and effacing (eae) gene

(Doyle et al., 1997; Neill, 1997; Law, 2000). The eae gene is responsible for the

production of an attaching and effacing lesion that causes the degradation and effacement

of intestinal epithelial cell microvilli, adherence of bacteria to the epithelial cells, and

assembly of highly organized cytoskeletal structures in the cells beneath attached bacteria

(Doyle and Schoeni, 1984; Knutten et al., 1989; Raghubeer and Matches, 1990). Once E.

coli 0157:H7 attaches to the mucosa, it will grow and secrete potent cytotoxins. These

cytotoxins are referred to as Shiga toxins, Shiga-like toxins, and verotoxins (Doyle and

Schoeni, 1984).

Unlike most foodbome pathogens, E. coli 0157:H7 is uniquely tolerant to acidic

environments (Brackett et al., 1994). Acid-resistant E coli is a potential pathogen for

humans if it contaminates food because of its ability to tolerate the low pH of the gastric

stomach (Fu et al., 2003). Inoculation studies conducted by Glass et al., (1992), have

shown that E. coli 0157:H7 can survive fermentation, drying, and storage of fermented

sausage (pH 4.5) for up to 2 months at 4*C, with only a 100-fold reduction in cell

populations. Studies conducted using lactic acid, acetic acid, or citric acid at

concentrations of up to 1.5% as organic acid sprays on beef showed that E. coli 01570H7

cells were not significantly affected by any of the concentrations used in the study






42

(Brackett et al., 1994). The mechanism of acid tolerance has not been fully elucidated but

appears to be associated with a protein(s) that can be induced by pre-exposing the bacteria

to acid conditions (Doyle et al., 1997).

Studies conducted on the heat sensitivity of E. coli 0157:H7 in ground beef have

shown that the pathogen has no unusual resistance to heat. Heating ground beef

sufficiently to kill typical strains of Salmonella will also kill E. coli 0157:H7. Line et al.

(1991), reported that the presence of fat increases the heat tolerance of E. coli 0157:H7 in

ground beef, with D values for lean (-2.0 % fat) and fatty (30.5 % fat) ground beef of 4.1

and 5.3 min, respectively, at 57.20C and 0.3 and 0.5 min respectively at 62.8*C. Proper

heating of foods of animal origin, i.e. heat foods to an internal temperature of at least

68C, is an important critical control point to ensure inactivation of E. coli 0157:H7

(Doyle et al., 1997).

The most frequently implicated vector for E. coli 0157:H7 outbreaks has been

ground beef. Bovine derived products have been linked to approximately 75% of

outbreaks (Callaway et al., 2003). Most confirmed human E. coli 0157:H7 outbreaks

have been associated with the consumption of undercooked ground beef, and less

frequently, unpasteurized milk; hence, cattle have been the focus of many studies to

determine their involvement in transmitting the pathogen (Martin et al., 1986; Borczyk et

al., 1987). Repeated outbreaks of hemorrhagic colitis linked to ground beef and/or cattle

and E. coli 0157:H7 have firmly established the connection between cattle and E. coli

0157:H7 in the public mind. Repeated large scale recalls of contaminated ground beef,

and the deaths of children who consumed foods contaminated by exposure to meat






43

products have further shaken the confidence of consumers in the wholesomeness and

safety of beef (Callaway et al., 2003).

The first reported isolation of E. coli 0157:H7 from cattle was from a less than 3-

week-old calf with colibacillosis in Argentina in 1977 (Orskov et al., 1987). Prevalence

surveys conducted on cattle estimated the overall fecal prevalence of E. coli 0157:H7 to

be very low (Elder et al, 2000). A study conducted by Wells et al. (1991) of cattle in

herds associated with two cases of human E. coli 0157:H7 infection revealed that 2.3%

of calves and 3.0% of heifers, but only 0.15% of adult cows, shed E. coli 0157:H7 in

feces. Hence young animals tend to carry E. coli 0157:H7 more frequently than adult

cattle. E. coli 0157:H7 is isolated predominantly from young animals, with the highest

rate of isolation from postweaned calves (Doyle et al., 1997). Several researchers have

reported that peak E. coli 0157:H7 fecal shedding rates occur during the summer and

early fall. These researchers reported shedding rates that can vary from a low of 0% to as

high as 61% on some farms. To date no factors have been identified, other than season,

that consistently affect the E. coli 0157:H7 shedding rates of cattle (Heuelink et al., 1998;

Jackson et al., 1998; Laegreid et al., 1999; Elder et al., 2000).

Sources of E. coli 0157:H7 for cattle have not been clearly identified. Possible

sources include contaminated feedstuffs, or water, colonized animals in herds, infected

wildlife, and humans, or contaminated facilities and equipment surfaces from contact

with feces (Doyle et al., 1997).

Fecal coliforms

Fecal coliforms are a group of bacteria that primarily live in the lower intestines of

all warm-blooded animals, including humans. These bacteria have several traits in






44

common with E. coli: they are gram negative rods, they rapidly grow, they ferment

lactose, and they do not form spores. E. coli is considered a type of fecal coliform. Fecal

coliforms such as E. coli, as the name implies, are frequently found in the feces of warm-

blooded animals including humans. Because they are found in feces, fecal coliforms have

been used as 'indicator bacteria' to detect the presence of fecal contamination in food and

water (Henken and Cocanougher, 1998).

Characteristics of Salmonella

Salmonella spp. are gram-negative non-spore forming, ova-shaped, facultative

anaerobes. These organisms produce gas from glucose and utilize citrate as their sole

carbon source (D'Aoust 1989; Takaya et al., 2002). They produce hydrogen sulfide gas,

decarboxylate lysine, and ornithine but are urease-negative and do not produce indole

(D'Aoust 1989). The rate of growth is dependent on temperature, pH, salinity, water

activity (ak), and nutrient level of the suspending medium (D'Aoust, 1989; Guthrie,

1992). Salmonellae are considered to be mesophilic bacteria with a temperature growth

range of 8-45*C; with optimum growth occurring in the range of 35-37C (D'Aoust,

1989; Guthrie, 1992). The organisms' growth can be inhibited at temperatures below

6.7*C; however, they are not killed and will resume growth if the temperature is returned

within the optimal range (Nickerson and Sinskey, 1972). Salmonella bacteria are killed at

temperatures 70C or above. Due to this characteristic, cooking for the amount of time it

takes to reach this temperature throughout the food being cooked is sufficient to destroy

Salmonella cells. The growth of Salmonella is generally inhibited in the presence of 3-

4% NaCl (D'Aoust, 1989). Their optimum pH range for growth is between 6.5-7.5 but it

has been shown that they can grow at pH ranges from 4 to 9. Salmonella, need a water






45
activity (a,) level of above 0.94 to grow with optimal growth occurring at 0.99 (D'Aoust,

1989).

Salmonella is not species specific (equine, poultry, swine, and bovine) and can be

transferred from animal to man through undercooked meat, raw eggs, or feces. Animals

can carry Salmonella species until they go to slaughter, or animal products may be

contaminated during processing and preparation (Cooke, 1996; Prescott et al., 1999).

They may be present in the intestinal tract and other tissues of red meat animals and

poultry without producing any apparent symptoms of infection in the animal (Marriot,

1999).

Parasites

All cattle are victims of internal nematode (worms) parasitism as long as they are

maintained on pasture. Gastrointestinal parasites are a major constraint to animal health,

productivity, and profitability in grazing livestock production systems (Stuedemann et al.,

2004). Anything that negates profitability results in loss to the producer and to the

livestock economy. Thus parasites negatively affect the economy of the industry

(Corwin, 1997). Worldwide, gastrointestinal nematode parasites and those of the

respiratory tract have a potentially major impact on herd health (Corwin, 1997). Parasite

free pastures would improve cattle health and performance, resulting in possible

economic return to producers (Stuedemann et al., 2004).

The impact of parasitism on the health of animals in general includes but is not

limited to production losses due to depressed appetite, reduced feed digestibility, and/or

disruption of normal metabolic or hormonal processes (Dargie 1987; Williams et

al.,1992; Herd, 1993). A severe parasitic load can result in weight loss, slow growth rates






46
of animals, and ultimately a loss in potential profits. In extreme conditions, heavy

parasitic infestation can lead to death (McGowan, 2003).

The effects of internal parasites on cattle will vary with the severity of infection as

well as age and stress level of the animal. In general, younger animals and animals under

stress are most likely to show signs of parasitism. Mature cows acquire a degree of

immunity to parasites that reside in the lower gastrointestinal tract (Gadberry et al., 2004;

Loyacano et al., 2002). In addition, parasite burdens are most detrimental in mature cows

near parturition because immunity is suppressed. Cows, especially dairy, in early lactation

are often in a negative energy balance due to the stress of lactation. These cattle are

affected more by parasitism than cows in later lactation, when smaller levels of milk are

being produced. Bulls are more susceptible to internal parasites than cows (Gadberry et

al., 2004).

The effects of parasitism can be separated into two types subclinical and clinical.

Losses in animal productivity (milk production, weight gain, altered carcass composition,

conception rate, etc.) are all subclinical effects; whereas, visible disease-like symptoms

(roughness of coat, anemia, edema, diarrhea) are clinical effects. The subclinical effects

are of major economic importance to the producer (Gadberry et al., 2004).

In an effort to determine whether or not an animal is ill due to internal parasites,

taking a fecal sample and examining it for the presence of parasite eggs is essential. This

is also necessary to avoid wasting money treating an animal needlessly. The flotation

method is based on the differential specific gravity of parasite eggs/oocysts and fecal

debris. Eggs and oocysts float in saturated sugar or salt solutions, while most debris

settles. By knowing just what type of eggs are present and an estimate of how many, it






47

can be decided if an animal or herd needs to be treated and if so which drugs to use

(Tritschler and LeaMaster, 1998).

There are two main types of parasite infestations in cattle: internal and external.

Major external parasites include horn flies, house flies, stable flies, horse flies, deer flies,

black flies, mosquitoes, cattle grubs, mites, ticks, and lice. Gastrointestinal worms

inhabit specific areas from the abomasum to the colon. There are many species, and all

can cause serious loss of condition (Catcott, 1977). Parasitized cattle are harmed, not

only by the parasites themselves, but also by the indirect damage the parasites cause to

the immune system (Bliss, 1999). Major internal parasites include stomach worms, lung

worms, liver flukes, and coccidia.

Haemonchus spp. also known as stomach worms, hairworms, barber's pole worm,

blood worm and "humongous" worm. Haemonchus spp. or stomach worms, are

nematodes found in the abomasum, intestine and lungs of cattle. The most common of

these is the brown worm, which causes non-specific immunosuppressive effects. The

brown stomach worm can destroy important glands located in the abomasum resulting in

loss of serum proteins, reduced acidity and diarrhea. This nematode parasite causes

inefficient feed utilization, depressed milk production and lighter calves at weaning

(Larson, 1997). Most Haemonchus worms are transmitted when infected cattle pass eggs

in manure onto the ground, eggs hatch in the manure, rain washes the larvae from the

manure and cattle swallow larvae on wet grass in moderate temperatures (Larson, 1997).

In regions such as the southeast and south-central United States, nematode parasitism is a

fact of life and without some form of effective prevention and control, losses in






48

productivity or deaths will occur (Larson, 1997). Haemonchus worms cannot be seen in

the manure. A diagnosis is made by finding worm eggs under the microscope.

Lung worms cause a lung disease in cattle with clinical signs similar to those

caused by viruses, bacteria and allergies. Transmission is similar to that of hairworms.

Lung worm disease occurs in previously unexposed cattle, such as calves (Faries, 1998).

Lung worms cause respiratory problems in calves and yearlings (Worley, 2000), and lung

worms cause pneumonia and provide an environment conducive for viral and bacterial

pneumonia, with labored breathing and anxiety leading to depressed performance

(Corwin and Randle, 1993).

Liver fluke infections may be developed in cattle living in wet areas with alkaline

soils. Clinical signs of liver fluke infestation are evident and cause digestive inefficiency

in young cattle with acute liver disease or in older cattle with chronic liver disease. Liver

flukes are transmitted when infected cattle, deer and rabbits pass eggs in manure and drop

the manure in water, eggs hatch in water and larvae develop in snails, and cattle swallow

cysts on grass or hay. Cattle with liver flukes have symptoms similar to those with

malnutrition and hairworms (Faries, 1998).

A major parasite that is a problem in many parts of the world including Florida is a

group of protozoa collectively called coccidia. The most important of these belong to the

genera of Eimeria. Coccidiosis continues to be one of the major disease problems for

cattle producers. Coccidia are protozoan parasites that are host specific. The oocyst, or

infective form of the parasite, is usually shed in the feces of affected animals or carrier

animals. The oocyst is highly resistant and can survive for years (Kirkpatrick and Selk,

2000).






49

Coccidiosis occurs more frequently in calves from one to six months of age, but

older cattle, especially those from one to two years, are often affected (Ferguson, 1996).

Coccidiosis in cattle usually presents as acute diarrhea, with or without blood, straining,

severe weight loss, and not uncommonly as a neurologic form which usually results in

death of the animal. The more chronic form causes growth retardation and/or is a stressor

causing an increased susceptibility to other infections. Coccidiosis is transmitted from

animal to animal by the fecal-oral route. Infected fecal material contaminating feed, water

or soil serves as carriers for the oocyst for the susceptible animal to contract by eating,

drinking, or licking itself. The severity of the clinical disease depends on the number of

oocysts ingested (Kirkpatrick and Selk, 2000).

Most cattle producers recognize that internal parasite infestation can damage their

livestock. Treatment with one or several dewormers is commonly applied. Strategic

deworming is the term in common use for preventing nematodes in beef cattle by

stopping pasture contamination. Too often deworming occurs when it is convenient or

when the cattle are being handled (Kvasnicka et al., 1998). The objective of strategic

deworming is to reduce parasite challenge by lowering parasite numbers on the pasture

and inside the animal. Hamilton and Giesen, (1997) reported that grazing yearling cattle

treated with a formulation of the dewormer fenbendazole (Safeguard, Hoescht) had

increased weight gains compared with control cattle. After 6 weeks of grazing, treated

cattle had 0% fecal samples positive for worm eggs, while control cattle had 50% positive

samples.

Dewormers are administered to cattle to kill internal parasites and stop damage

caused by these parasites. Administering drugs at the right time is critical to stop parasite






50

life cycles. The effective ingredients in dewormers include chemicals such as lasalocid,

sulfonamides, amprolium, benzimidazoles, albendazole, fenbendazole, oxfendazole,

ivermectin, levamisole and morantel. Once a parasite population is established within a

herd of cattle, they must be identified and treated. Accurate, specific and regular

treatment is the only path to elimination and prevention of parasites in a cow-calf herd. A

strategic deworming program must be outlined specifically for each ranch and for each

cattle management plan.

Sensory Characteristics of Beef

Palatability characteristics, such as flavor and tenderness, are major factors

influencing consumer acceptance of beef and beef products. Research in the past has

concentrated on identifying certain production variables, such as feeding and management

programs, which may affect beef palatability (Xiong et al., 1996). Some authors

concluded that beef flavor from forage-fed cattle was not negatively affected (Oltien et

al., 1971; Cross &Dinius, 1978), whereas most other reports indicated beef from forage

fed-cattle had a less desirable flavor (e.g. "grassy") than that from grain-fed cattle

(Reagan et al., 1977; Bowling et al., 1978). The undesirable flavor in forage fed beef is

attributed mainly to volatiles, which are soluble in the lipid component (Larick & Turner,

1990). Forage finishing of beef has not been recommended in the past due to lower

dressing percent, decreased quality grade, yellow fat color, dark muscle color, and

decreased flavor and tenderness relative to grain-fed beef (Mandell et al., 1997). In

contrast, other studies (Bidner et al., 1981; Fortin et al., 1985; McCaughey and Clipef

1996) generally found no differences in palatability attributes between forage- and grain-

finished beef (Mandell et al., 1997).






51

Several factors have been identified as general predictors of whether beef will be

acceptably tender. Most notable among these factors are age and sex of the animal (Huff

and Parrish, 1993). Beef from more mature animals repeatedly has been found less tender

than beef from younger animals (Tuma et al., 1963; Dikeman and Tuma, 1971; Smith et

al., 1982). Sex of the animal (castrated vs non-castrated males), however, has been

shown to have somewhat less of a definitive effect upon tenderness (Huff and Parrish,

1993).

Meat quality is an important criterion that influences the decision of a consumer to

purchase beef. Many investigators (Maltin et al., 2001; Mandell et al., 1998; May et al.,

1992; Moloney et al., 2001; Sinclair et al., 1998) studied the relation among different

production factors (feeding plan, age, breed, gender, etc.) and sensory attributes

(tenderness, juiciness, flavor, texture, color). Among the factors that influence consumer

perception of meat quality are tenderness (Chrystall, 1994), color (Baardseth et al., 1988),

juiciness (Hutchings and Illford, 1988) and flavor (Melton, 1990).

As grain prices increase, interest in beef cattle forage-finishing systems also

increases. Climate and forage resources could allow the southeastern United States the

opportunity to utilize alternative finishing systems although cow-calf operations

predominate the Southeast (Sapp et al., 1996). Forage-fed beef has been discriminated

against due to lean color, lower palatability, off flavors, and less retail stability which

limits consumer acceptability (Sapp et al., 1996).

Sapp et al. (1996) conducted a study to compare pasture-fed (wheat-ryegrass) and

grain-fed beef from young Angus steers for palatability, storage and shelf life

characteristics. A total of 60 animals over two years were subjected to one of three






52

postweaning feeding programs wheat-ryegrass pasture only, wheat-ryegrass pasture

followed by grain, and a mixed ration in drylot fed ad libitum. The researchers reported

that pasture-fed beef and grain fed beef were similar in sensory panel tenderness scores

but pasture/grain-beef was less tender than either the pasture-fed or grain-fed beef. The

reason for this difference could have been due to connective tissue content of the

pasture/grain-fed beef. Sensory panel connective tissue scores reflected tenderness scores

with pasture- and grain-fed beef containing less connective tissue. The researchers

reported that grain-fed beef was juicier than pasture- and pasture/grain-fed beef according

to sensory panel scores. Schroeder et al. (1980) reported higher juiciness scores for

steaks from grain-fed cattle versus steaks from forage-fed cattle. Juiciness is usually

associated with intramuscular fat and as a result the differences could be due to marbling

differences between the treatment groups (Sapp et al., 1996). Breidenstein et al. (1968)

and Gilpin et al. (1965) found that steaks from carcasses with higher marbling scores

were associated with consistently higher juiciness ratings when evaluated by sensory

panels. Sapp et al. (1996) reported no flavor differences between grain-, pasture- and

pasture/grain-fed beef. However, other researchers have reported lower flavor scores for

forage-fed beef compared to grain-fed beef. Schroeder et al. (1980) reported higher

flavor scores for steaks from grain-fed cattle versus forage-fed cattle. Bowling et al.

(1977), Harrison et al. (1978), and Meyer et al. (1960) all found that forage-fed beef had

lower flavor desirability scores. Sapp et al. (1996) also reported that pasture/grain-fed

and grain-fed beef displayed lower incidence of off flavor than pasture-fed beef.

While there is evidence, particularly from North American beef production systems,

that concentrate-fed animals produce more tender and better flavored meat than forage-






53

fed animals (Sapp et al., 1996; French et al., 2000), dietary effects in many of these

experiments are confounded by differences in animal age or carcass weight at slaughter

(Bowling et al., 1978; Harrison et al., 1978). When both feeds are offered ad libitum,

carcass growth of concentrate-fed cattle is often higher relative to animals fed grazed

grass or other forages. Thus, concentrate-fed animals have heavier and fatter carcasses

than forage-fed animals when grown for a constant time period or may be younger when

grown to a specific body weight or back fat thickness (French et al., 2000). Carcass

weight, back fat thickness, age at slaughter and pre-slaughter growth rate have all been

shown to alter meat quality, specifically tenderness and flavor (French et al., 2000).

Objective Characteristics

Color

Color is an extremely critical component of the appearance of fresh beef sold

through retail, and among visual characteristics has substantial influence on purchase

decisions. Muscle color is an important criterion by which many consumers evaluate

meat quality and acceptability. In red meats, consumers relate a bright-red color to

freshness, but discriminate against meat that has turned brown (O'Sullivan et al., 2004;

Sami et al., 2004).

Retaining cattle after weaning and even to a finished weight, and allocating

different types of beef cattle to forage can allow an option for increased productivity and

profit to producers. However, on a similar time scale, forage-fed cattle typically do not

have the same degree of finish as grain-fed cattle due to the decreased energy available in

the forage (Baublits et al., 2004). Although typical forage-fed beef is lean and warrants

an acceptable USDA yield grade, it is often inferior to traditional grain-fed beef in terms






54
of both USDA quality grade and has a darker lean color as well as a more yellow fat color

(Priolo et al., 2001; Morgan et al., 1969). The color of the lean and external fat cuts of

meat has been shown to be influential on the purchasing ability and visual acceptability

by the consumer (Baublits et al., 2004).

Typically, forage-based rations, as well as different forages and seasonal changes,

allow for carcasses with a darker lean appearance or fat that is yellow in appearance. The

darker lean can be attributed to increased myoglobin, decreased muscle glycogen, or both,

and the yellow fat is due to forages having increased carotenoids (which are deposited in

adipose tissue) compared to concentrates (Priolo et al., 2001). A study conducted by

Baublits et al. (2004) examined beef lean color characteristics of steers and heifers

grazing cool season forages supplemented with soyhulls. The forages used were tall

fescue (Fescue) and orchardgrass (Orchard). These authors reported lower L* values for

control animals that grazed Fescue pasture with no supplementation compared to animals

that grazed Fescue and Orchard but were supplemented with pelleted soy hulls. The

authors could not determine the exact cause for the lower L* values in control carcasses

but it was thought that it could be due to differences in antemortem muscle glycogen and

its effect on the pH of the meat. Vestergaard et al. (2000) reported less glycogen, a higher

pH, and darker lean for longissimus muscle from young bulls that were fed a forage-

limited diet compared to young bulls fed concentrates ad libitum. Baublits et al. (2004)

reported lower b* values, indicating degree of yellow appearance, for control animals

than that of Fescue or Orchard animals. The differences were thought to be due to muscle

pH. Page et al. (2001) reported a negative correlation between pH and b values.

Therefore, if the cattle had less muscle glycogen at the time of slaughter, then a higher






55
muscle pH and lower lean b* values could have been the result. Carotenoid

concentrations in adipose tissue could also have an effect upon yellowness and b* values

(Morgan et al., 1969). Baublits et al. (2004) reported no differences between treatments

for objective adipose color, therefore illustrating that carotenoid concentrations in their

study did not contribute to the differences in yellowness of the lean color. Bennett et al.

(1995) reported that the lean color of steers finished on rhizoma peanut tropical grass

pasture, was darker than that of concentrate finished steers. Bidner et al. (1981) and

Reagan et al. (1977) both reported a darker lean color for forage fed animals in

comparison with concentrate-fed animals. Both of these authors attributed part of the

darker lean color to a higher myoglobin concentration in the longissimus muscle of forage

finished steers. The heme pigment, myoglobin is mainly responsible for the color of

meat. Varnam and Sutherland (1995) hypothesized that grass-fed animals have more

muscle myoglobin, due to more activity pre-slaughter than their feedlot counterparts.

Tenderness

Meat tenderness, and the factors that affect it, have been studied for many years.

Tenderness can vary from animal to animal, from muscle to muscle within an animal, and

from area to area within a muscle (Bourne, 1982). Tenderness is further affected by

processing treatments applied to the animal. Many studies have shown that tenderness

can be significantly decreased in beef if the muscle is removed from the carcass before

proper aging is completed (Kastner, 1983; Jeremiah et al., 1985). Differences in the rate

and extent of postmortem tenderization are the principle sources of variation in meat

tenderness and are probably the source of inconsistency in meat tenderness at the

consumer level. To solve the tenderness problem, an even greater understanding of the






56
mechanisms regulating meat tenderness and tenderization must be gained (Koohmaraie et

al., 1996).

Tenderness is extremely difficult to measure objectively because the chewing

motions involved in mastication involve both vertical and lateral movements of the

human jaw as well as various in-between modifications, which together produce the

impression of tenderness (Pearson, 1963). A number of objective methods for evaluating

meat tenderness have been developed. One of the first to be developed, and one still

widely used, is the Warner-Bratzler shear WBS (Bratzler, 1932). The WBS method uses

a single blade to shear a uniform core of meat, and registers the maximum or peak load
4
necessary to effect the shear.

Due to time and money, it is very difficult to maintain a well-trained sensory panel,

to evaluate meat characteristics from different studies. Tenderness of a cooked meat

samples can be assessed much more easily using WBS than a trained sensory panel

analysis (Shackelford et al., 1995). Harris and Shorthose (1988) reported that shear

force does not accurately reflect tenderness differences among muscles, however most

researchers rely upon WBS for objective estimates of tenderness (Smith et al., 1978).

Several authors have found positive correlations between sensory panel tenderness ratings

and WBS values for the same muscles, which suggest that WBS is reliable to use in lieu

of trained sensory panel results (Brady, 1937; Kropf and Graf, 1959; Alsmeyer et al.,

1966).

Schaake et al. (1993) conducted a study comparing steers that were fed exclusively

fescue clover pasture, pastured on fescue clover then placed on summer pastures (i.e.

sorghum sudangrass, millet, coastal bermudagrass, or Tifton 44 bermudagrass), pastured






57
on fescue-clover and then placed in a drylot for 45, or 75 days, and steers that were placed

in a drylot after weaning and conditioning. The researchers reported that the steaks from

the carcasses of the steers that were placed in the drylot after weaning and conditioning

were most tender according to WBS measurements but did not differ from steaks from

summer pasture-fed animals (Schaake et al., 1993). According to a trained taste panel

done in the same study, panelists found steaks from the summer pasture-fed steers to be

more tender but otherwise similar to steaks from the long term drylot steers in agreement

with the WBS measurements (Schaake et al., 1993). Sapp et al. (1996) reported that

WBS values for strip loin steaks from pasture/grain-fed steers were higher than steaks

from grain-fed steers. Smith et al. (1978) suggested that shear force and trained sensory

panel tenderness ratings are sufficiently correlated to justify the use of either measure for

assessing the tenderness of muscles in a beef carcass.













MATERIALS AND METHODS

Experiments were conducted to evaluate the effects of three feeding regimens on

performance, microbiology, sensory and objective characteristics of beef cattle. The

study was conducted at the University of Florida's Boston Farm Santa Fe River Ranch

Beef Unit at Alachua, Florida. The study was conducted over three consecutive years -

Summer 2002 to Spring 2003 and Fall 2003 to Spring 2005. Two experiments were

conducted. A total of 60 Brangus cattle were employed in the study. Experiments One

and Two, utilized a complete random design with 30 Brangus beef cattle with three

treatments, and ten replicate cattle per treatment per experiment.

Animals

The animals in Experiment One ranged in age from 15 to 18 months of age with an

average age of 17 months. The average initial weight of the cattle during this experiment

was 344.73 kg. The cattle in Experiment Two ranged in age from 8 to 10 months with an

average age of 9 months. The average initial weight of the cattle during this experiment

was 247.21 kg. All animals used in the study had been vaccinated and were weaned. All

animals were dewormed using a dewormer with ivermectin injectible prior to the start of

each experiment. Animals were tagged with an identification label that corresponded to

its treatment group. Appropriate feeding, and care management practices were employed

for all animals. Approved medications (Liquamycin) were administered as needed to






59
insure the health of all animals. This study was approved by the Institutional Animal

Care and Use Committee (IACUC).

Animal Diets and Feeding Procedure

Animal diets in both Experiment One and Experiment Two, consisted of two

different isoprotein diets and bahiagrass ad libitum. The first treatment group often

animals received a commercially available 12% protein non-medicated concentrate (F-R-

M Super 12, Flint River Mills Inc., Bainbridge, GA) once per day in addition to being

allowed to graze in a 2-acre plot of fertilized bahiagrass pasture. The second treatment

group of ten animals received a commercially available 12% protein concentrate that

contained a coccidiostat "lasalocid" (Cattle Pasture Supplement B-80 Medicated, Flint

River Mills Inc., Bainbridge, GA) once per day in addition to being allowed to graze a 2-

acre plot of fertilized bahiagrass pasture. The third treatment group of ten animals was

only allowed to graze ad libitum in a 2-acre plot of fertilized bahiagrass pasture. The

Super 12 concentrate contained corn chops, wheat middlings, rice mill by-product, cane

molasses, salt, Vitamin A supplement, Vitamin D-3 supplement, and minerals. The

Cattle Pasture Supplement B-80 Medicated concentrate contained, lasalocid, cottonseed

meal, corn meal, soybean meal, rice mill by product, animal fat stabilized with BHA,

urea, Vitamin A supplement, Vitamin D-3 supplement, salt, and minerals. All three

groups of steers were given a mineral mix (Special UF Mineral Mix, University of

Florida, Gainesville, Fl) which contained calcium, phosphorous, salt, magnesium, copper,

cobalt, iodine, manganese, selenium, and fluorine. The amount of each concentrate

supplement was regulated on the basis of total consumption. The Super 12 concentrate

was initially fed at a rate of 2.3 kg (5 lb) per animal to its respective group of animals. It






60
was increased 0.5 kg (1 lb) to a maximum of 11.4 kg (25 lbs) per animal/day unless there

was feed left from the previous day in which case the same amount as the previous day

was given. According to manufacturer instructions, each pound of B-80 medicated

concentrate provided 40 mg of lasalocid and was to be fed continuously at a rate of no

less than 60 mg nor no more than 200 mg of lasalocid per animal per day. The B-80

medicated concentrate was given initially at a rate of 0.7 kg (1.5 lbs) per animal. It was

increased 0.1 kg (0.25 lbs) to a maximum of 2.3 kg (5 lbs) per animal/day unless there

was feed left from the previous day in which case the amount given either remained the

same as the previous day or was reduced 0.1 kg.

Weight, Fecal, and Blood Collection

The animals were weighed every 28 days until the project target weight of 453 + 22

kg (1000 50 lbs) was reached. From these weights, average daily gain (ADG) was

calculated. Fecal samples were also collected from each animal on the weighing date.

Fecal sample collection consisted of taking a rectal sample directly from the animal and

placing it into a sterile container (Fisher Scientific, Pittsburgh, PA 15238). The fecal

samples were then divided in half. Half of the sample was transported to the Meat

Science microbiology laboratory for analysis, and the remaining half was taken to Florida

A&M University for analysis of parasites. During Experiment One, blood samples were

collected every 28 days using blood collection needles (Vaccutainer, Franklin Lakes, NJ,

02685A) and Vaccutainer blood collection tubes without coagulant (Vaccutainer,

Franklin Lakes, NJ, 02685A). During Experiment Two, blood samples were collected at

the beginning of the trial and then again at the end of the trial. Blood samples were

transported to University of Florida Veterinary Science Department and analyzed for total






61
blood chemistry. Total blood chemistry included analyzing for albumin, alkaline

phosphate (Alk Phos), anion gap, aspartate amino transferase (AST), bilirubin, blood urea

nitrogen, calcium, carbon dioxide, chloride, creatinine, gamma glutamyl transpeptidase

(Gamma GT), globulin, glucose, magnesium, phosphorous, potassium, sodium, and total

protein.

Microbiological Analysis

Twenty-five grams of each fecal sample were taken and placed in sterile 18 x 30 cm

Fisherbrand stomacher bags (400 ml, Fisher Scientific, Pittsburgh, PA 15238) along with

250 ml of sterile 0.1% peptone water. The stomacher bags were stomached in a

stomacher (Tekmar Company, Cincinnati, Ohio, 45222 Model #400) for two minutes.

One milliliter of the sample diluent from the stomacher bag, 1:10 solution, was

transferred to a test tube containing 9 ml of sterile 0.1% peptone water from which 102 to

10.5 were prepared. One gpl from the dilutions was pipetted onto Soribitol MacConkey

Agar (SMAC, Difco Laboratories, Detroit, MI 46232-7058, Cat. No. DF0078-17-7) for

the detection of generic Escherichia coli and Escherichia coli 0157:H7 and spread onto

the plates using a glass hockey stick, which was flame sterilized before spreading. One

Itl from the same dilutions was pipetted onto Tryptic Soy Agar (TSA, Difco Laboratories,

Detroit, MI 46232-7058, Cat. No. DF0369-17-6), and onto mFC Agar (media for

enumeration of fecal coliforms, Difco Laboratories, Detroit, MI 46232-7058, Cat. No.

DF0677-17-3) for the detection of aerobic bacteria and fecal coliforms respectively. In

addition one jil was also pipetted onto Xylose Lysine Desoxycholate Agar (XLD, Difco

Laboratories, Detroit, MI 48232-7058, Cat. No. DFO 788-17-9) and Hektoen Enteric

Agar (HE, Difco Laboratories, Detroit, MI 48232-7058, Cat No. DFO 853-17-9) for the






62
direct detection of Salmonella organisms. All plates were prepared in duplicate. The

SMAC plates were incubated at 35*C for 24 hours. The TSA, XLD, and HE plates were

incubated at 37C for 24 hours. The mFC plates were incubated at 43C for 24 hours.

After 24 hours of incubation, typical generic E. coli and E. coli 0157:H7 colony forming

units from the SMAC plates were enumerated and averaged. Following 24 hour

incubation, colony forming units (CFU) from the TSA and mFC plates were counted,

averaged, and recorded as total aerobic bacteria, and fecal coliform bacteria, respectively.

After incubation period, typical Salmonella CFU from the XLD and HE plates were

enumerated and averaged.

The presence of Salmonella was determined by placing Ig of fecal sample into 9 ml

of lactose broth and incubated at room temperature for 60 min. After incubation at room

temperature, the sample was then incubated at 35C for 24 hours. After 24 hour

incubation 0.1 ml of the broth was transferred to 10 ml of Rappaport-Vassiliadis (RV,

Difco Laboratories, Detroit, MI, 48232-7058, Cat. no. DFO 1858-17). The RV medium

was then incubated at 43*C for 24 hours. After this incubation a loopful of the RV

sample was streaked onto XLD and HE agar and the plates were incubated for 24 hours at

37*C. After 24 hours the plates were examined for typical Salmonella and recorded.

Except for the substitution of Violet Red Bile Agar (VRBA, Difco Laboratories,

Detroit, MI, 48232-7058, Cat. No. DFO012177) for SMAC media, all microbial analyses

were the same for Experiment Two. The SMAC media was substituted due to the fact

that VRBA produced more of a distinct color difference between generic E. coli and E.

colil 0157:H7.






63

Parasite Analysis

Coccidia, Haemonchus, and Moniezia parasite analysis was conducted using a fecal

flotation method (Tritschler and LeaMaster, 1998). One gram of fecal sample was placed

into a jar along with enough water to form a 1:10 ratio of sample to water. The jar was

then shaken to disperse the fecal material. A 1.5 ml aliquot of the mixture was

transferred to a test tube. The test tube was then filled with a concentrated salt solution

until a meniscus was formed at the top. A glass slide was placed over the tube for

approximately 15 5 minutes. The slide was then examined under a microscope moving

from edge to edge. When worm like eggs were observed, the microscope was focused to

determine identification. A descriptive chart was used to verify the type of eggs being

observed. A qualitative and quantitative count was conducted. The number of eggs per

gram (EPG) of feces was calculated using the following formula: EPG = (grams of feces

+ ml of fluid)/grams of feces x 1/3 x (no. of eggs counted).

Environmental Samples

Bahiagrass

Three grass samples per plot were randomly collected at the beginning and the end

of Experiment One from the two acre plots where each group of steers grazed. Samples

were collected during the month of June (early summer), and then again during the month

of November (late fall). During Experiment Two, three random grass samples per plot

were collected at the beginning and the end of the experiment from the plots where each

group of steers grazed. Samples were taken once during November (late fall) and again

during June (early summer). All samples were analyzed for moisture (AOAC 930.04), fat

(AOAC 930.09), crude protein (AOAC 978.04), ash (AOAC 930.05), neutral detergent






64
fiber (NDF) and acid detergent fiber (ADF) (during Experiment Two only) (AOAC,

1997; Van Soest and Robertson, 1985). The total fiber content of the grass was estimated

by difference (i.e. total fiber) during Experiment One.

Microbial analysis of the grass included enumerating aerobic organisms, fecal

coliforms, generic E. coli and E coli 0157:H7, and evaluating for the presence of

Salmonella spp. Enumeration involved aseptically transferring 25g of bahiagrass into a

sterile stomacher bag, making a 1:10 dilution with 0.1% peptone water. The sample was

stomached for 2 min. Serial dilutions were made with 0.1% peptone water. Dilutions

were then transferred and spread onto selective media. Aerobic organisms were

enumerated on TSA. E. coli organisms were enumerated on SMAC. The presence of

Salmonella was done as previously described. TSA plates were incubated at 37.C for 24

hours. SMAC plates were incubated at 35*C for 24 hours. After 24 hour incubation,

colonies were enumerated, and averaged.

Animal Drinking Water

Three samples of animal drinking water were taken directly from the animal

drinking supply. Sterile container cups (Fisher Scientific, Pittsburgh, PA 15238, Cat. no.

14-375-147) were opened and placed into the animal drinking water supply. Cups were

then sealed and transported back to the meat science laboratory for microbial analysis.

Animal drinking water was analyzed for aerobic bacteria, E. coli, E. coi 0157:H7,

fecal coliforms, and Salmonella. A 0.1 pl aliquot was taken from the undiluted sample

and spread evenly onto selective media. Aerobic organisms were enumerated on TSA.

E. coli organisms were enumerated on SMAC. Salmonella organisms were enumerated

on XLD and HE plates.








Animal Feed

Three grab samples were aseptically collected in sterile cups at the beginning and at

the end of experiment one from each of the two commercially available animal feeds.

Cups were sealed, labeled and transported to the meat science laboratory for microbial

analysis. Animal feed was analyzed for aerobic bacteria, E. coli, E. coli 0157:H7, fecal

coliforms, and Salmonella.

Twenty-five grams of animal feed were added to a sterile stomacher bag along with

225 ml of 0.1% peptone water to prepare a 1:10 dilution. The sample was then

stomached in a stomacher for 2 min. Serial dilutions with 0.1% peptone water were

prepared and spread onto selective media. Aerobic organisms were enumerated on TSA.

E. coli organisms were enumerated on SMAC. The analysis for presence of Salmonella

was conducted as previously described. TSA plates were incubated at 37C for 24 hours.

SMAC plates were incubated at 35C for 24 hours. After 24 hour incubation, CFU's

were enumerated and averaged.

Animal Slaughter and Carcass Characteristics

When at least ten animals irrespective of treatment, reached the target weight of

453.6 22.7 kg (1000 50 lbs) that group often animals were transported to Central

Beef Company, Center Hill, Florida for slaughter. The remaining 20 animals irrespective

of treatment were then placed on the F-R-M Super 12 commercial feed until the target

weight range was reached. Once that target weight range was reached, the remaining 20

animals were then transported and slaughtered at a commercial United States Department

of Agriculture (USDA) inspected plant. Carcass weights were recorded for each animal.

The resulting carcasses were split longitudinally, rinsed and sprayed with a 2% lactic acid






66

solution for microbial intervention and chilled for 24 hours in a 1 2*C cooler. The

chilled carcasses were ribbed and evaluated subjectively by trained meat staff personnel

for hot carcass weight, USDA yield grade, marbling score, fat over the eye, measured rib

eye area, lean color, lean texture, and lean firmness. Lean color was determined using an

eight point rating scale: (1= dark pink, 2= very light cherry red, 3= light cherry red, 4=

slightly light cherry red, 5= cherry red, 6= moderately dark red, 7= dark red, 8= very dark

red). Lean texture was determined using a seven point scale: (1= very fine, 2= fine, 3=

moderately fine, 4= slightly coarse, 5= coarse, 6= very coarse, 7= extremely coarse).

Lean firmness was determined using a seven point scale: (1= very firm, 2= firm, 3=

moderately firm, 4= slightly soft, 5= soft, 6= very soft, 7= extremely soft). The short loin

portion of each animal (between the 12t rib and the sirloin area, including the 13th rib

excluding the flank) was then harvested and cut into steaks for sensory analysis, pH,

Warner Bratzler Shear (WBS), and objective color analysis.

Sensory Analysis

Steaks were cut from the short loin portion of each animal. Individual steaks were

vacuum sealed in Cryovac B550T (Sealed Air Corp., Duncan, SC) bags and subsequently

heat shrunk in 82*C water as per manufacturers recommendation. Steaks were then

subjected to postmortem aging for 14 days at 2 20C in a walk in cooler. After the

postmortem aging period, steaks were frozen at -40 2C then transferred to a -20 2C

holding freezer until sensory analysis was conducted. Steaks were thawed for 18 hours at

2 to 4C then broiled on Faberware (Farberware, Bronx, NY) open-hearth broilers to an

internal temperature of 71*C (American Meat Science Association, 1995). The housing

and drip pans of each broiler were covered with aluminum foil and preheated for 15 min.






67
Copper-constantan thermocouples (Omega Engineering, Inc., Stamford, CT) were placed

in the approximate geometric center of each steak and used to record internal

temperature. Steaks were turned when the internal temperature of 350C was reached and

removed from the broiler when the internal temperature reached 71C. Weight in grams

was recorded while the steaks were frozen, after thawing, and after cooking for

calculation of cook loss and thaw loss.

A sensory panel of 7 to 11 trained panelists were used to evaluate all samples for 5

characteristics using the following trait and rating scales: juiciness (8 = extremely juicy,

7 = very juicy, 6 = moderately juicy, 5 = slightly juicy, 4 = slightly dry, 3 = moderately

dry, 2 = very dry, and I = extremely dry); beef flavor intensity (8 = extremely intense, 7

very intense, 6 = moderately intense, 5 = slightly intense, 4 = slightly bland, 3 =

moderately bland, 2 = very bland, and I = extremely bland); overall tenderness (8 =

extremely tender, 7 = very tender, 6 = moderately tender, 5 = slightly tender, 4 = slightly

tough, 3 = moderately tough, 2 = very tough, and 1 = extremely tough); connective tissue

(8 = none detected, 7 = practically none, 6 = trace amounts, 5 = slight amount, 4 =

moderate amount, 3 = slightly abundant, 2 = moderately abundant, and 1 = abundant

amount); off flavor (6 = none detected, 5 = threshold; barely detected, 4 = slight off-

flavor, 3 = moderate off-flavor, 2 = strong off-flavor, and 1 = extreme off-flavor).

Panelists were also asked to identify any off-flavors that may have been detected such as

rancidity, salty, sweet, sour, fishy, bitter, metallic, sulfur, soapy, garlic, and grassy. At

each session, panelists were served 5 samples, a warm-up sample, water for rinsing their

pallets, and unsalted crackers. The lighting in the room consisted of using red and white






68

fluorescent lighting. The sensory panel required approval from the University of Florida

Review Board in order to be conducted.

Objective Color Analysis

Instrumental color data were obtained 48 hours postmortem by using a Minolta

chromatographer (Model CR-300; Minolta Corp., Ramsey, NJ). Upon ribbing of the

carcass and exposure of the longissimus muscle at the 12* rib, a blooming period of

approximately 30 min was utilized before instrumental color analysis. Instrumental color

data of the lean was measured using the L* a* b* color spectrum. This spectrum includes

L* (lightness) which is a measure of total light reflected on a scale ranging from 0 = black

to 100 = white. The a* (red/green) value is a measure of the red (positive values) and

green (negative values) colors of a sample. As the value of a* increases, the sample has

an increase in red coloration. As the value of a* decreases the sample has an increase in

green coloration. The b* (blue/yellow) value is a measure of the yellow (positive values)

and blue (negative values) colors of a sample. As the value of b* increases, the sample

takes on a more yellow coloration. As the value of b* decreases the sample takes on

more of a blue coloration. Steaks were cut from the short loin portion of each animal,

and analyzed for color. The objective color values were obtained at the central, medial,

and lateral areas of the exposed longissimus at the 12* rib, and a mean value of the three

locations was calculated.

Warner Bratzler Shear Analysis

After the postmortem aging period, steaks were frozen at -40*C then transferred to a

-20'C holding freezer until Warner Bratzler Shear (WBS) analyses were conducted. Loin

steaks were thawed for 18 hours at 2 to 40C then broiled on Faberware (Farberware,






69

Bronx, NY) open-hearth broilers to an internal temperature of 71C (American Meat

Science Association, 1995). The housing and drip pans of each broiler were covered with

aluminum foil and preheated for 15 min. Copper-constantan thermocouples (Omega

Engineering, Inc., Stamford, CT) attached to a potentiometer were placed in the

approximate geometric center of each steak and used to record internal temperature.

Steaks were turned when the internal temperature of 35*C was reached and removed from

the broiler when the internal temperature reached 71*C. Samples were allowed to cool at

2 to 4"C for approximately 18 hours and then 4 to 6 1.27-cm cores were removed from

each steak, parallel to fiber orientation, for WBS shear force determination. Shear force

determinations were conducted on an Instron (Instron Corporation, Canton, MA, Model

1011) universal testing machine equipped with a WBS head, with a crosshead speed of

200 mm/min.

pH

The pH of the steaks was measured by using an Accumet Basic pH meter (Fisher

Scientific, Pittsburgh, PA 15238 Model AB15). The pH probe was standardized using

standard buffer solutions of pH 4.0 and pH 7.0. A 10-g sample was taken from each

steak (one steak per animal id) and placed into a stomacher bag along with 100 ml of

distilled water and gently massaged by hand for one min. The pH was then recorded. The

probe was rinsed with distilled water, and blotted dry with a Kim wipe (Kimberly-Clark

Corporation, Roswell, GA, Cat no. 06-666) between each sample measurement.

Data Analysis

The statistical analysis for this study was performed using SAS for Windows (SAS

Institute, 1998). Two experiments were conducted and both utilized a complete






70
randomized design. Both experiments had three treatments and ten animals per

treatment A total of 60 animals (30 per experiment) were used in this study. Analysis of

variance was performed using a PROC mixed procedure of SAS to analyze cattle average

daily gain, total aerobic bacteria, generic E. coli, fecal coliforms, total blood chemistry,

and parasites. A repeated measures design was used to investigate the effects of

treatment (diet) and time (month) and the interaction of treatment and time. Comparisons

among means were performed using least square means (lsmeans statement) of SAS.

Treatment effects and differences were considered significant when P s 0.05. Analysis of

variance was performed to analyze animal feed samples, animal drinking water samples,

bahiagrass samples, carcass data, objective measurements (color, pH, Warner-Bratzler

Shear Force), and sensory panel evaluation in both experiments using the general linear

models procedure (PROC GLM) and least square means (Ismeans) of SAS (SAS Institute,

1998). Treatment effects and differences were considered significant when P < 0.05.













RESULTS AND DISCUSSION

The objectives of this study were (1) to monitor the performance of Florida Brangus

beef cattle fed three different diets that could be utilized by small farmers, (2) to monitor

the prevalence of E. coli 0157:H7, generic E. coli, fecal coliforms, total aerobic bacteria,

and parasites in the cattle when subjected to a comprehensive feeding and optimized

management program, (3) to monitor the effects of the program on dressing percentage

and subjective and objective consumer parameters, and 4) to determine the microbiology

and proximates of the concentrates and bahiagrass fed to the cattle. The study included

two experiments.

Experiment One: Performance, Microbiology, Sensory and Objective Analyses for
17 Month Old Brangus Cattle and Environmental Sample Analyses

Growth Performance

Initial weights of the cattle were taken at the end of June 2002. Average daily gains

were calculated beginning in July (month 0). The initial starting weights of all cattle were

similar (P > 0.05) (Table 1). Feeding cattle B-80 concentrate for 28 days resulted in an

increase in average daily weight gain during the first month when compared to cattle fed

Super 12 concentrate and cattle allowed to graze only. After two months, the cattle fed

the B-80 experienced a significant decline in average daily weight gain which resulted in

all the cattle having a similar (P > 0.05) average daily weight gain. After 3 and 4 months,

the cattle that were fed the Super 12 concentrate had significantly higher (P < 0.05)

average daily gain when compared to cattle fed B-80 concentrate and cattle allowed to








graze only. After two months the cattle fed B-80 concentrate and the cattle allowed to

graze only had similar (P > 0.05) average daily weight gain.

Table 1. Average daily weight gain values of Brangus steers fed different
commercially available feed concentrates, and allowed to graze on bahiagrass or
allowed to graze only for four months: Experiment One.
Average Daily Weight Gain (kg)
Month
Treatment
Initial Weight (kg)r 0 1 2 3 4
Super 12b 345.1 1."OY 0.7" 0.7" 0.8" 0.8"
B-80 348.3x 2.9' 1.1f 0.6O" 0.4"M 0.4
Grazersd 342.1x 1.2y 0.8" 0.5x 0.3Y 0.4w
"cattle initial weight
bSuper 12 consisted of 10 steers given F-R-M Super 12 concentrate and allowed to
graze on bahiagrass.
9B-80 consisted of 10 steers given B-80 concentrate with "lasalocid" and allowed to
graze on bahiagrass.
dGrazers consisted of 10 steers allowed to graze on bahiagrass only.
"means in the same row with different superscripts differ significantly (P 0.05).
"first month of steers on respective diets
"'Ymeans in the same column with different superscripts differ significantly (P 0.05).

Sollenberger et al. (1988) reported that Brangus steer gains on bahiagrass averaged

0.4 kg/day over a 2-year trial. They also reported that average daily weight gains on

bahiagrass were greatest in the spring and early summer and generally declined over the

remainder of the grazing season. Similar to previous reports (Sollenberger et al., 1988;

Sollenberger et al., 1989) the ADG in this study generally declined throughout the

experiment Previous reports (Martin et al., 1984; Kiser et al., 1985) regarding the

influence of lasalocid on beef cattle performance have been contradictory. Kiser et al.

(1985) found that 200-mg lasalocid/head/d enhanced weight gain of cows fed sorghum

silage, and Martin et al. (1984) reported that 200-mg lasalocid added to a corn silage diet






73

increased rate and efficiency of gain. In contrast, no performance response was seen

when 200 mg lasalocid/d was fed in a grain carrier to fall-calving beef cows (Hopman

and Weber, 1986), or when lasalocid was added to protein-supplemented corn silage diets

fed to growing animals (Berger et al., 1981; Horton and Brandt, 1981). In the current

study where the B-80 concentrate containing lasalocid was fed in a cottonseed, corn, and

soybean meal-based formulation, the results agreed with those of Horton and Brandt,

(1981). Feeding lasalocid improved average daily weight gain when compared to grazing

alone. However, no advantage in average daily gain was observed for cattle fed B-80

when compared to cattle fed Super 12.

The significant treatment*month interaction (P = 0.0001) determined for average

daily weight gain was due to the significant decreases in the cattle average daily weight

gain in months 3 and 4 for cattle fed B-80 and allowed to graze only. Cattle fed Super 12

did not experience a significant decline in average daily weight gain (Table 1). After 3

and 4 months cattle fed Super 12 concentrate had significantly higher (P < 0.05) average

daily weight gain when compared to cattle fed B-80 concentrate, and cattle allowed to

graze only (Table 1).

The cattle that were fed Super 12 concentrate and allowed to graze reached the

target weight of 453 22 kg after four months which was approximately two months

faster than the cattle fed B-80 and allowed to graze, or cattle that were allowed to graze

only. All cattle that reached the target weight range, were weighed and transported to a

local meat processing plant for harvesting. A total of 14 cattle (6 from the Super 12

treatment, 5 from the B-80 treatment and 3 from the grazers treatment) were harvested.






74

The remaining cattle (i.e. 16 animals) were placed on the Super 12 concentrate and

allowed to graze until the target weight was reached.

Table 2. Average daily weight gain values of Brangus steers that were initially fed
Super 12, or B-80 and allowed to graze, or allowed to graze only and then placed onto
Super 12 concentrate: Experiment One.
Average Daily Gain (kg)
Month
Treatment 52 6 Final Weight (kg)'
Super 12b 0.7 0.5" 460.8x
Super 12 (B-80)C 0.5" 0.5" 445.8y
Super 12 (Grazers)d 0.4Oy 0.5m" 436.8y
Remaining animals placed on Super 12 and allowed to graze.
bSuper 12 consisted of 4 steers placed on Super 12 and allowed to graze on bahiagrass.
cSuper 12 (B-80) consisted of 5 steers fed B-80 concentrate and allowed to graze on
bahiagrass until month 5 at which time they were removed from B-80 and fed Super
12 and allowed to graze.
"Super 12 (Grazers) consisted of 7 steers allowed to graze on bahiagrass only until
month 5 at which time they were fed Super 12 concentrate and allowed to graze.
'means in the same row with different superscripts differ significantly (P s 0.05).
*final weight of animals before slaughter.
"means in the same column with different superscripts differ significantly (P 0.05).

After two months on Super 12, all cattle had similar (P > 0.05) average daily gains.

Cattle that were initially on B-80 and cattle that were initially allowed to graze only did

not experience a significant increase or decrease in average daily weight gain after being

placed on Super 12 (Table 2). However, cattle that were initially given B-80 and allowed

to graze and the cattle that were allowed to graze only reached the target weight range

within an additional 2 months after being fed the Super 12. Overall the cattle that were

fed the Super 12 initially had a higher (P < 0.05) final weight when compared to the cattle

that were initially fed B-80 and allowed to graze only. One reason for this difference is






75
due to the fact that the steers fed B-80 and the steers allowed to graze only began with

similar (P > 0.05) initial weights as cattle fed Super 12 throughout the study but had

lower average daily weight gains.

Martz et al. (1999) reported that steers on grass-legume pastures (consisting of

mostly tall fescue and Kentucky Bluegrass and red clover, white clover and birdsfoot

trefoil) required more days, 40 to 88, to reach a finished weight (1200 lbs) than feedlot

steers. Their findings were similar to previous research (Davies, 1977; Turner and

Raleigh, 1977) wherein cattle finished on pasture had equivalent final weights to feedlot

cattle with 40 to 60 additional finishing days on high quality pasture either with pasture

alone or with full feeding of grain on pasture.

Microbiology of Fecal Samples

A significant treatment*month interaction (P = 0.0001) was revealed for total

aerobic bacteria counts. This significant interaction was due to the decrease in aerobic

bacteria over time (Table 3). In general the three treatments had similar (P > 0.05) total

aerobic bacteria counts across the sampling period with the exception of a decrease and

then an increase during the last two sample periods (months 3 and 4), respectively (Table

3).

Initially, the cattle that received the Super 12 concentrate had significantly lower (P

< 0.05) aerobic bacteria counts than cattle fed B-80, or were allowed to graze only (Table

3). During the next two months (months I and 2) Super 12 fed cattle were similar (P >

0.05) in total aerobic bacteria counts when compared to cattle fed B-80 and cattle allowed

to graze only. Cattle allowed to graze only were significantly lower (P < 0.05) in total

aerobic bacteria when compared to cattle fed B-80 (Table 3).








Table 3. Mean total aerobic bacteria counts of steer fecal samples. Steers were given
two different commercially available feeds and allowed to graze on bahiagrass or
allowed to graze only: Experiment One.

logo CFU/g
Month
Treatment
0" 1 2 3 4 Overall mean
Super 12b 7.3yf 7.0'" 7.2" 6.3Y 8.3y 7.2y
B-80 7.6"' 7.3xy 7.6x" 6.8xh 8.2y 7.5x
Grazersd 7.8 6.7Y8 7.1 6.6 8.9 7.4A
Overall mean 7.5' 7.0" 7.38 6.6' 8.46
"initial month samples taken (July)
'Super 12 consisted of 10 steers given Super 12 concentrate and allowed to graze on
bahiagrass.
"B-80 consisted of 10 steers given B-80 concentrate with "lasalocid" and allowed to
graze on bahiagrass.
dGrazers consisted of 10 steers allowed to graze on bahiagrass only.
'means in the same row with different superscripts differ significantly (P < 0.05).
'Ymeans in the same column with different superscripts differ significantly (P < 0.05).

Over the next month (month 3) the cattle fed the Super 12 had significantly (P <

0.05) lower total aerobic bacteria counts than the cattle fed B-80 or cattle allowed to

graze only. Aerobic bacteria counts were similar (P > 0.05) for the cattle fed B-80 and

the cattle allowed to graze only (Table 3). During month 4, the grazers group had

significantly higher (P < 0.05) total aerobic bacteria counts than the cattle fed B-80 and

Super 12. The cattle that were fed Super 12 and B-80 had similar (P > 0.05) total aerobic

bacteria counts (Table 3).

Generic E. coli, E. coli 0157:H7, and Salmonella spp.

Initially, the cattle in all treatments had similar (P > 0.05) generic K coi (Table 4).

During months 1, 2 and 3, the Super 12 concentrate group had significantly higher (P >

0.05) generic K coli counts when compared to the grazers (Table 4). The animals that






77
were fed the B-80 medicated concentrate were similar (P > 0.05) to the animals that

received the Super 12 concentrate during months 1,.2 and 3. After month 4, all

treatments were similar (P > 0.05) in generic E. coli counts (Table 4).

Table 4. Mean generic Escherichia coli counts of steer fecal samples. Steers were
given two different commercially available feeds and allowed to graze on bahiagrass or
allowed to graze only: Experiment One.
logo CFU/g
Month
Treatment
0O 1 2 3 4 Overall mean
Super 12b 3.9" 4.2"x 4.3"* 6.2Vf 7.8" 5.3x
B-800 3.2xg 3.2x' 3.8x" 6.2~f 7.9" 4.7y
GrazersO 3.6"' 3.0" 3.4Y 5.5; 7.9" 4.7
Overall mean 3.5s 3.5' 3.8' 6.1f 7.9c
'initial month samples taken (July)
bSuper 12 consisted of 10 steers given Super 12 concentrate and allowed to graze on
bahiagrass.
WB-80 consisted of 10 steers given B-80 concentrate with "lasalocid" and allowed to
graze on bahiagrass.
^Grazers consisted of 10 steers allowed to graze on bahiagrass only.
"means in the same row with different superscripts differ significantly (P s 0.05).
x"means in the same column with different superscripts differ significantly (P s 0.05).

The highest level of generic E coli was observed during months 3 and 4 (October

and November respectively) (Table 4). Callaway et al. (2003) discussed peak fecal

shedding of generic E. coli and concluded that peak fecal E coli shedding occurs more

frequently during the summer and late fall months. The data in the current study follow

that same pattern. No significant treatment*month interaction (P = 0.1779) was revealed

for generic E. coli. In general generic E. coli increased as time increased. All fecal

samples collected for all cattle were negative for E. coli 0157:H7 and Salmonella spp.






78
Several researchers (Diez-Gonzalez et al., 1998; Scott et al., 2000; Krause et al., 2003)

have observed an increase in E. coli when cattle consume high-grain diets, while others

have demonstrated that high-grain diets result in decreased shedding (Hovde et al., 1999).

Diez-Gonzalez et al. (1998) reported that cattle fed a 90% corn/soybean meal ration

(feedlot-type ration) contained generic E. coli populations that were 100-fold higher than

cattle fed a 100% good-quality hay (Timothy) diet. The E. coli recovered

from the feces of grain-fed cattle were 1000-fold more resistant to an "extreme" acid

shock that simulated passage through the human stomach than were E. coli from cattle

fed only hay (Diez-Gonzalez et al., 1998). Diez-Gonzalez et al. (1998) suggested that the

acidic conditions within the animal resulting from the feeding of high-grain diets, allows

a population of acid resistant E. coli to proliferate. Acid resistant E. coi would in turn

survive the acidic conditions in the human gastric stomach and result in an increased risk

of human infection (Diez-Gonzalez et al., 1998). The results of the current study agree

with those of Diez-Gonzalez et al. (1998) in that an increase in generic E. coli

populations was observed in the cattle fed Super 12 when compared to cattle that were

allowed to graze only. However that was not true with cattle fed B-80 when compared to

cattle allowed to graze only. In contrast Hovde et al. (1999) found no significant

differences in E. coli present in experimentally infected cattle fed high-grain or high-fiber

diets.

Hancock et al. (1997) examined 36 beef cattle herds between Idaho, Oregon, and

Washington (12 in each state). Their research showed a range of 0% to 5.5% herd

prevalence for E. coi 0157:H7, with a strong clustering toward the lower end of this

range. It has been reported that weaned dairy cattle and yearling beef cattle at slaughter






79
are more likely to shed E. coli 0157:H7 in their feces than adult cattle (Buchko et al.,

2000).

Microbiology for Bahiagrass

The mean total aerobic bacteria counts for the bahiagrass samples were similar (P

> 0.05) in months 0 and 4 (July and November respectively) (Table 5). The total aerobic

bacteria counts for all grass samples were approximately 6 logo CFU/g. E. coli, E. coli

0157:H7, fecal coliforms, and Salmonella spp. were not detected on any of the grass

samples.

Microbiology for Animal Drinking Water

The mean total aerobic bacteria counts for the animal drinking water samples were

similar (P > 0.05) for all treatments in months 0 and 4 (July and November respectively)

(Table 6). Total aerobic bacteria counts were approximately 3.0 logo CFU/ml for all

treatments. The mean counts for generic E. coli and fecal coliforms were also similar (P

> 0.05) for all treatments, and were less than 1.0 logo CFU/ml, and 2.0 logo CFU/ml

respectively. No E. coli 0157:H7 or Salmonella spp. was detected in any of the drinking

water samples. E. coli 0157:H7 can persist in water trough sediments for periods of at

least 4 months and may even be able to replicate in this environment (Hancock et al.,

1997).

Microbiology for Animal Feed

The mean total aerobic bacteria counts for the Super 12 and the B-80 medicated

feeds were similar (P > 0.05) (Table 7). E. coli, E. coli 0157:H7, Salmonella and fecal

coliforms were not detected in any of the two feeds during the month 0 and 4 (July and

November respectively).








Table 5. Mean total aerobic bacterial counts of bahiagrass that was grazed by all three
groups of steers for Experiment One.
(logl0 CFU/g)
Month
Treatment 0 4 Mean
Super 128 6.1"' 6.0"' 6.0'
B-80b 5.7"' 5.8"' 5.8x
Grazerse 6.1"" 6.1" 6.1'
'Super 12 consisted of 10 steers given Super 12 concentrate and allowed to graze on
bahiagrass.
bB-80 consisted of 10 steers given B-80 concentrate with "lasalocid" and allowed to
graze on bahiagrass.
"Grazers consisted of 10 steers allowed to graze on bahiagrass only.
'means in the same row with different superscripts differ significantly (P s 0.05).
"means in the same column with different superscripts differ significantly (P < 0.05).

Table 6. Mean total aerobic bacteria counts, Escherichia coli, and Fecal coliform
counts for the animal drinking water for Experiment One.
total aerobic bacteria E. coli Fecal coliforms
(logo CFU/ml) (log CFU/ml) (lto10 CFU/ml)
Month

Treatment 0 4 Mean 0 4 Mean 0 4 Mean
Super 12" 3.1"' 3.2" 3.2' 1.0" 0.8"' 0.9' 1.9" 1.8"A 1.8S
B-80b 2.8" 3.0"" 2.9' 0.3"' 0.5"' 0.3 1.5"1 1.6" 1.5'
Grazers" 2.7" 2.9" 2.8' 0.6" 0.4"' 0.5' 1.8' 1.8"' 1.8
"Super 12 consisted of 10 steers given Super 12 concentrate and allowed to graze on
bahiagrass.
bB-80 consisted of 10 steers given B-80 concentrate with "lasalocid" and allowed to
graze on bahiagrass.
cGrazers consisted of 10 steers allowed to graze on bahiagrass only.
means in the same row with different superscripts differ significantly (P < 0.05).
'means in the same column with different superscripts differ significantly (P f 0.05).








Table 7. Mean total aerobic bacterial counts of the two commercially available animal
feeds given to the steers for Experiment One.
(logl0 CFU/g)
Month
Feed Concentrates 0 4 Mean
F-R-M Super 12' 4.5'" 4.6 4.6"
B-80 Medicatedb 5.6"c 5.7" 5.6'
9Super 12 concentrate fed to 10 animals in addition to grazing on bahiagrass.
bB-80 concentrate containing lasalocid and fed to 10 animals in addition to grazing on
bahiagrass.
'means in the same row with different superscripts differ significantly (P < 0.05).
'means in the same column with different superscripts differ significantly (P s 0.05).

Parasites

Coccidia are protozoan parasites chiefly of the genus Eimeria. Coccidia destroy the

epithelial cells of the intestine and impair the absorption of nutrients. A significantly

higher (P < 0.05) count for coccidia eggs was determined in the animals that were

allowed to graze on bahiagrass only, when compared to cattle fed Super 12 and B-80

(Table 8). Cattle fed Super 12 and B-80 concentrates had similar (P > 0.05) levels of

coccidia eggs (Table 8). However, a lower number of coccidia were isolated from the

cattle fed B-80 concentrate when compared to Super 12 and cattle allowed to graze only.

A possible explanation for this is the fact that the B-80 concentrate contained lasalocid

which is used as a coccidiostat. Diet regimen had no effect on the level of the

Haemonchus or Moniezia eggs isolated from the three treatment groups (Table 8).

Haemonchus thrives under Florida weather conditions, and is a potential year round

threat. During the summer months the eggs hatch readily in the warm, humid and rainy

climate, releasing viable larvae into the environment. This is the time of greatest






82

Table 8. Mean parasitic eggs isolated from feces of steers given two different
commercially available feeds and allowed to graze on bahiagrass or allowed to graze
only: Experiment One.
Treatment Coccidia (EPG) Haemonchus (EPG) Moniezia (EPG)
Super 12' 8.38y 1.37x 0.29x
B-80b 3.66 1.15x 0.15x
Grazersc 18.28x 1.80X 0.00O
Super 12 consisted of 10 steers given Super 12 concentrate and allowed to graze on
bahiagrass.
bB-80 consisted of 10 steers given B-80 concentrate with "lasalocid" and allowed to
graze on bahiagrass.
cGrazers consisted of 10 steers allowed to graze on bahiagrass only.
x-ymeans in the same column with different superscripts differ significantly (P < 0.05).

exposure and highest incidence of disease. During the cooler weather of winter months

larvae have developed the ability to "hibernate". This process is called hypobiosis. During

this time the worms are metabolically very inactive and quite resistant to treatment. In

the spring the dormant worms become active again, resulting in a "spring rise" in the

number of eggs excreted, and a seeding of the environment just before optimal summer

conditions occur (Heath and Harris, 1991).

Bahiagrass Samples

Moisture, ash, fat, protein, pH and crude fiber of the grass samples were similar (P

> 0.05) for all plots of grass grazed by the animals (Table 9). Protein percentage of any

grass sample depends on the maturity of the grass, and whether grass has been fertilized.

Kalmbacher and Wade (2003) reported a crude protein value of 12-15% for fertilized

bahiagrass and a value of 9-12% for unfertilized bahiagrass. The protein values in this

study are in agreement with those reported by Kalmbacher and Wade (2003).








Table 9. Mean proximate analysis values and pH for bahiagrass samples collected
from pastures for Experiment One.

Bahiagrass
Treatment Super 12' B-80b Grazerse
Month 0* Month 4f Month 0 Month 4 Month 0 Month 4
Moisture, % 52.6d 50.7d 51.3d 50.6d 52.8d 50.5d
Ashs, % 5.5d 5.6d 4.9d 5.5d 5.1d 5.3d
Fat*, % 2.4d 2.6d 2.8d 2.5d 2.4d 2.2d
Proteins, % 15.8d 7.2d 14.2d 7;4d 14.1d 7.7d
Crude fiber, % 23.7d 33.9d 26.8d 34.0d 25.6d 34.3d
pH 6.7d 6.7d 6.5d 6.6d 6.8d 6.6d
"Super 12 consisted of 10 steers given Super 12 concentrate and allowed to graze on
bahiagrass.
bB-80 consisted of 10 steers given B-80 concentrate with "lasalocid" and allowed to
graze on bahiagrass.
cGrazers consisted of 10 steers allowed to graze on bahiagrass only.
means in the same row with different superscripts differ significantly (P 0.05).
*June 2002
'June 2004
*values expressed on a dry matter basis

Cattle Blood Samples

Aspartate amino transferase (AST) is an enzyme that promotes transfer of an amino

group from glutamic acid to oxaloacetic acid. Gamma glutamyl transpeptidase (GGT) is

an enzyme that participates in the transfer of amino acids across the cellular membrane.

They both can be measured in the blood to test liver function. Significantly higher (P <

0.05) amounts of AST, and GGT were found in the cattle that were fed the Super 12

concentrate when compared to cattle allowed to graze only, and cattle fed B-80 (Table

10). The cattle that were fed B-80 and the cattle that were allowed to graze only were

similar (P > 0.05) for AST and GGT. Although there were significantly higher amounts






84

detected in this group they were not high enough to indicate severe liver disease

(Osweiler et al., 1993). Although there was a higher amount of AST and GGT detected

in the blood of the cattle that were fed the Super 12 concentrate, the values detected in the

blood of all animals regardless of diet were within the expected range of 46-185 U/L, and

11-60 U/L for AST and GTT, respectively.

There was a significantly higher (P < 0.05) amount of calcium detected in the cattle

that were fed the B-80 concentrate when compared to the cattle that were fed the Super 12

and the cattle that were allowed to graze only. A similar (P > 0.05) amount of calcium

was detected in the blood of the cattle that were fed the Super 12 concentrate and the

cattle that were allowed to graze only (Table 11).

Table 10. Mean blood values of aspartate amino transferase and gamma glutamyl
transpeptidase in the blood of steers given two different commercially available feeds
and allowed to graze on bahiagrass or allowed to graze only for Experiment One.
Treatment AST (U/L)d GGT (U/L)d
Super 12" 96.3x 21.1x
B-80b 75.5y 12.0y
Grazerse 74.3Y 13.4A
"Super 12 consisted of 10 steers given Super 12 concentrate and allowed to graze on
bahiagrass.
B-80 consisted of 10 steers given B-80 concentrate with "lasalocid" and allowed to
graze on bahiagrass.
'Grazers consisted of 10 steers allowed to graze on bahiagrass only.
'AST = Asparate Amino Transferase
*GGT = Gamma glutamyl transpeptidase
meanss in the same column with different superscripts differ significantly (P K 0.05).

Although there was a significantly higher amount of calcium detected in the cattle

that were fed the B-80, the level of calcium in the blood of all cattle was within the

expected range of 8.1-11.0 mg/dL. Calcium (Ca) and phosphorus (P) has a vital function






85

in almost all tissues in the body and must be available to livestock in the proper quantities

and ratio. These elements make up over 70% of the total mineral elements in the body

(McDowell and Arthington, 2005). Ninety-nine percent of the Ca and 80% of the P in the

entire body are found in bones and teeth. Adequate Ca and P nutrition depends not only

on sufficient total dietary supplies, but also on the chemical form in which they occur in

the diet and on the vitamin D status of the animal. The dietary Ca:P ratio also can be

important A dietary Ca:P ratio between 1:1 and 2:1 is assumed to be ideal for growth

and bone formation as this is approximately the ratio of the two minerals in bone.

Ruminants can tolerate a wider range of Ca:P particularly when their vitamin D status is

high. Clinical signs of borderline Ca deficiencies are not easily distinguishable from

other deficiencies. An inadequate intake of Ca may cause weakened bones, slow growth,

low milk production in dairy cattle and tetany (convulsions) in severe deficiencies

(Williams et al., 1990; McDowell and Arthington, 2005).

Table 11. Mean blood values for calcium, magnesium, chloride and potassium in the
blood of steers given two different commercially available feeds and allowed to graze
on bahiagrass or allowed to graze only for Experiment One.
Treatment Calcium Magnesium Chloride Potassium
(mg/dL) (mg/dL) (mEq/L) (mEq/L)
Super 12' 8.9y 2.1x 106.6" 4.6Y
B-80b 9.5" 1.8y 107.5" 5.0X
Grazerse 8.9y 2.lx 102.9y 4.5y
"Super 12 consisted of 10 steers given Super 12 concentrate and allowed to graze on
bahiagrass.
B-80 consisted of 10 steers given B-80 concentrate with "lasalocid" and allowed to
graze on bahiagrass.
'Grazers consisted of 10 steers allowed to graze on bahiagrass only.
meanss in the same column with different superscripts differ significantly (P < 0.05).






86

A significantly lower (P < 0.05) amount of magnesium was detected in the cattle

that were fed the B-80 concentrate when compared to the cattle that were fed the Super 12

concentrate and the cattle that were allowed to graze only (Table 11). A similar amount

of magnesium was detected in the blood of the cattle that were fed the Super 12

concentrate and the cattle that were allowed to graze only. However, the level of

magnesium in all cattle was within the expected range of 1.8-3.0 mg/dL. Magnesium

(Mg) has many diverse physiological functions. The Mg in the skeleton is important for

the integrity of bones and teeth. Magnesium is the second most plentiful cation (after

Potassium) of intracellular fluids. Deficiency of Mg in cattle can lead to

hypomagnesemic tetany (convulsions) which can be classified into clinical and non-

clinical tetany (McDowell and Arthington, 2005).

A significantly lower (P < 0.05) amount of chloride (Cl) was detected in the blood

of the cattle that were allowed to graze only when compared to cattle fed the concentrates

(Table 11). The concentration of chloride was similar (P > 0.05) for cattle that were fed

the Super 12 and B-80 concentrates. Although there were differences in chloride detected

between the groups, the level of chloride for all cattle was within the expected range of

99-110 mEq/L. Sodium and chloride, in addition to potassium, all function in

maintaining osmotic pressure and regulating acid-base equilibrium. These two mineral

elements function as electrolytes in body fluids and are specifically involved at the

cellular level in water metabolism, nutrient uptake, and transmission of nerve impulses.

Chlorine is necessary for activation of amylase and is essential for formation of gastric

hydrochloric acid (McDowell and Arthington, 2005). The essential need for sodium (Na)

and Cl by livestock has been demonstrated for thousands of years by a natural craving for






87

common salt Sodium is the critical nutrient in salt and evidence of a naturally occurring

dietary deficiency of Cl, as distinct from Na, has not been established. However, the

requirement is often expressed as salt (NaCI) (McDowell and Arthington, 2005). The Na

requirement for ruminants is between 0.04% and 0.25% of the diet. The Cl requirement

for ruminants is generally unknown. Fettman et al. (1984) estimated a Cl requirement for

lactating dairy cows to be between 0.10% and 0.20% and would not exceed 0.27%.

The initial sign of Na deficiency is a craving for salt, demonstrated by the avid

licking of wood, soil, and sweat from other animals and drinking water. Cattle deprived

of salt may be so voracious that they often injure each other in attempting to reach salt. A

prolonged deficiency causes loss of appetite, decreased growth, unthrifty appearance,

reduced milk production, and loss of weight. More pronounced signs of Na deficiencies

include shivering, incoordination, weakness, and cardiac arrhythmia, which can lead to

death (McDowell and Arthington, 2005). Coppock (1986) reported that an

experimentally produced Cl deficiency, independent ofNa deficiency, results in clinical

signs in dairy cows that include decreased body weight and milk production, depraved

appetite, lethargy, anorexia, emaciation, constipation, cardiovascular depression, and milk

dehydration.

A significantly higher (P < 0.05) amount of potassium was detected in the blood

of the cattle that were fed the B-80 concentrate when compared to the cattle that were fed

the Super 12 and the cattle that were allowed to graze only (Table 11). The concentration

of potassium was similar (P > 0.05) for cattle that were fed the Super 12 concentrate and

the cattle that were allowed to graze only (Table 11). Although there was a significantly

higher amount of potassium detected in the cattle that were fed B-80, the level of






88

potassium for all cattle was within the expected range of 4.0-5.5 mEq/L. Potassium is the

third most abundant mineral element in the animal body and is the principal cation of

intracellular fluid. It also is a constituent of extracellular fluid where it influences muscle

activity. Potassium is essential for life, being required for a variety of body functions

including osmotic balance, acid-base equilibrium, several enzyme systems and water

balance. Potassium deficiency for ruminants results in non-specific signs such as slow

growth, reduced feed and water intake, lowered feed efficiency, muscular weakness,

nervous disorders, stiffness, decreased pliability of hide, emaciation, intracellular

acidosis, and degeneration of vital organs (McDowell and Arthington, 2005).

There was a significantly higher (P < 0.05) anion gap (acid/base balance) in the

cattle that were fed Super 12 concentrate when compared to the cattle that were fed the B-

80 and the cattle that were allowed to graze only (Table 12). The anion gap was similar

(P > 0.05) for cattle that were fed B-80 concentrate and cattle that were allowed to graze

only (Table 12). Despite the higher anion gap in the Super 12 cattle, all three groups of

cattle were within the expected anion gap range of 10-30.

There was a significantly higher (P < 0.05) concentration of glucose detected in

the blood of the cattle that were fed the Super 12 concentrate when compared to the cattle

fed the B-80 and the cattle that were allowed to graze only (Table 12). A similar (P >

0.05) amount of glucose was detected in the blood of the cattle fed B-80 and the cattle

that were allowed to graze only (Table 12). Despite the differences in glucose levels

detected within the blood, all glucose levels regardless of diet regimen were within the

expected range for glucose of 40-80 mg/dL.






89

A significantly higher (P < 0.05) amount of carbon dioxide was detected in the

blood of cattle that were allowed to graze only when compared to the cattle that were fed

the B-80 and Super 12 concentrates (Table 12). The cattle that were fed the Super 12 and

B-80 concentrates had similar (P > 0.05) levels of carbon dioxide detected in their blood.

All cattle's carbon dioxide levels regardless of diet regimen were within the expected

range for carbon dioxide of 15-34 mEq/L.

Table 12. Mean blood values for anion gap, glucose, and carbon dioxide in the blood
of steers given two different commercially available feeds and allowed to graze on
bahiagrass or allowed to graze only for Experiment One.
Treatment anion gap glucose (mg/dL) carbon dioxide (mEq/L)
Super 12" 18.8x 75.8x 21.3y
B-80b 6.6y 69.7y 21.3y
Grazersc 17.2y 70.5y 24.3x
"Super 12 consisted of 10 steers given Super 12 concentrate and allowed to graze on
bahiagrass.
'B-80 consisted of 10 steers given B-80 concentrate with "lasalocid" and allowed to
graze on bahiagrass.
CGrazers consisted of 10 steers allowed to graze on bahiagrass only.
'Ymeans in the same column with different superscripts differ significantly (P 5 0.05).

Carcass

The cattle that were fed the Super 12 concentrate had a significantly higher (P <

0.05) carcass weight when compared to the cattle that were allowed to graze only (Table

13). The cattle that were fed B-80 concentrate had similar carcass weight (P > 0.05)

when compared to cattle fed Super 12 concentrate and cattle that were allowed to graze

only (Table 13). The significantly higher (P < 0.05) carcass weight observed in the cattle

that were fed Super 12 when compared to the cattle that were allowed to graze only is due

to the fact that cattle that were allowed to graze only had similar initial live body weight