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 Mineral interrelationships
 Chelation
 Literature cited














Title: Recent developments in minerals for beef cattle and swine
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Permanent Link: http://ufdc.ufl.edu/UF00072999/00001
 Material Information
Title: Recent developments in minerals for beef cattle and swine
Physical Description: 16 leaves : ; 28 cm.
Language: English
Creator: Cunha, T. J ( Tony Joseph ), 1916-
University of Florida -- Dept. of Animal Science
Publisher: University of Florida, Department of Animal Science
Place of Publication: Gainesville Fla
Publication Date: 1966
 Subjects
Subject: Minerals in animal nutrition   ( lcsh )
Beef cattle -- Feeding and feeds -- Florida   ( lcsh )
Swine -- Feeding and feeds -- Florida   ( lcsh )
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (leaves 15-16).
Statement of Responsibility: by T.J. Cunha.
General Note: Caption title.
General Note: "Address given at the Salt Institute, Chicago, Illinois, on February 23, 1966."
 Record Information
Bibliographic ID: UF00072999
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 78788155

Table of Contents
    Mineral interrelationships
        Page 1
    Chelation
        Page 2 (MULTIPLE)
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
    Literature cited
        Page 15
        Page 16
Full Text



,) Recent Developments in !inerals for Beef Cattle and Swine

*s0 by
T. J. Cunha*
', L .' Department of Animal Science
University of Florida-


While many developments have occurred in the mineral nutrition field during the

past 25 years, it is apparent that only the surface has been scratched in determining

the mineral needs of beef cattle and swine. As one studies the available data, it

becomes apparent that many gaps exist in the present knowledge available.

Mineral Interrelationships

Until the many mineral interrelationships are understood, it will be difficult

to determine mineral needs on a very exact basis. The requirement for a specific

mineral element will, in many cases, be dependent on the level of other mineral

elements in the diet. For example, the zinc needs will be especially influenced by

the level of calcium and possibly other mineral elements in the ration. Interrela-

tionships exist between calcium, phosphorus and magnesium. Vitamin D also influences

this interrelationship. Excessive iron may influence phosphorus utilization. Copper

is needed for the utilization of iron. The level and kind of protein in the ration

influences copper toxicity as well as utilization. Molybdenum influences copper

utilization and needs and sulfur affects this interrelationship. There is some

interrelationship between zinc and copper. Many more such examples could be cited.

Suffice it to say that this is just a start on the many known mineral interrelation-

ships and undoubtedly there are still many which are undiscovered as yet.

Probably one of the most challenging areas of nutrition research lies ahead in

unraveling the many aspects of mineral interrelationships and interactions and their

affect on specific mineral needs of animals. The complexity of the problem is

obvious when one realizes that it involves intestinal absorption, enzyme activity,





*Address given at the Salt Institute, Chicago, Illinois, on February 23, 1966.




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metabolic function, blood and tissue functions and so many other essential body

activities. The old saying that "if a little is good, a little more is better" is

most likely to be false when dealing with minerals. A good balance of mineral ele-

ments is needed. Until more is learned about mineral interactions or interrelation-

ships, one should stay close to recommended levels of minerals in animal rations.

Chelation

The problem of mineral availability is complicated by organic and/or inorganic

chelates. Mineral elements may be chelated by a compound which will either increase

or decrease its availability. Much remains to be learned to determine which che-

lates are beneficial and which are not and what can be done to control their action.

Until chelates and chelation is thoroughly understood, it will be difficult to

understand and predict with real accuracy mineral needs and requirements with cer-

tain type rations since many chelates will vary in their content in different feeds.

Glycine, cysteine, oxalic acid and phytic acid are only a few examples of chelates

present in feeds which will effect the availability of certain mineral elements.

Swine mineral needs

Following are some recent developments on the mineral requirements of the pig.

Calcium and phosphorus

Probably the most interesting recent development is the finding by Cornell

workers (1) that atrophic rhinitis can be produced by feeding diets low in calcium

or by an imbalance of calcium and phosphorus. They found some atrophic rhinitis

when pigs were fed the NRC nationall Research Council) recommended levels of 0.8

per cent calcium in the ration (2). Their findings suggested that dietary calcium

for the growing-finishing pig should be increased above the level currently recom-

mended by the NRC since levels of 1.0 to 1.2 per cent calcium in the ration promoted

higher bone ash and better integrity of the nasal turbinates. It will be important

to follow further Cornell and other University research along this line in order to

determine the final outcome of these studies and what their effect will be on the

recommended levels of calcium and phosphorus in swine rations. If the Cornell





3 -

studies can be substantiated higher calcium levels right be recommended for swine

rations in the future. On the other hand, a few investigators have been able to use

lower levels of calcium than those recommended by NRC for the growing-finishing pig

with good results. The reason for this is not known. It is possible that the level

of calcium in the drinking water may have had some effect on the level needed in the

ration. It is important to determine the level of minerals in the drinking water

when studying mineral needs. This level can vary considerably and could have a big

influence on the minerals needed in the ration since pigs will consume from 2 to 4

pounds of water per pound of feed. It is important that proper calcium levels be

used since excess calcium increases the need for zinc, unidentified factors and

other nutrients.

Trace minerals

The information in table 1 shows the levels recommended by the National

Research Council (2). Included in this table is information on requirements,

tolerance level as well as the toxic level of minerals for the pig.


Table 1. Trace Minerals for Swine



Requirement Tolerance level Toxic level
Mineral Element mg./kg. feed mg./kg. feed mg./kg. feed3


Copper 101 100 250
Iron 801 1,000 4,000
Iodine 0.20 --
Magnesium 400 --
Manganese 40 80 500
Zinc 502 1,000 2,000
Selenium 0.10 -- 5


1Baby pig requirement.

2Higher levels may be needed if excess calcium is fed.

3Mg. per kg. is the same as ppm.





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Copper

The requirement for copper has been established as 10 ppm. The tolerance level

has been set at 100 ppm. This level could probably be safely increased to 125 ppm.

The toxic level has been set at 250 ppm. There is some disagreement on calling

this a toxic level. The use of copper sulfate at levels of 250 ppm. in the ration

has occasionally resulted in toxic effects at the Florida and lachigan Stations.

Other Experiment Stations in the U.S. and in England have not reported such a toxic

effect. There evidently is a reason for the differences involved. Research to

date indicates some interrelationship between the level and source of protein as

well as the zinc level and copper toxicity. This may account for the differences

obtained in the U.S. and England.

Most of the results obtained to date show that a favorable response to copper

feeding occurs during the early part of the growth period and this benefit tends to

disappear later on. This indicates that copper feeding might be limited to the early

growth period of the pig.

Research to date indicates that copper has bactericidal properties in addition

to being needed for hemoglobin formation and other metabolic processes in the body.

These bactericidal properties are the reason why there is considerable interest in

using copper at levels higher than 10 ppm. It is interesting to note that levels

of copper of 250 ppm. in the ration seems to always decrease the hemoglobin level

a little. This is something which almost all investigators have reported.

Since a level of 250 ppm will occasionally cause toxicity,the writer would

presently not recommend this level in swinerations. If occeaionlly -pi~- wvll

die, as occurred in the Florida and Michigan studies, it is logical to assume that

deaths may also occur elsewhere. Since almost the same results are obtained with

125 ppm of copper in the ration, the writer would recommend this level whenever

copper feeding is indicated.




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Iron

A great deal of work has been done on iron fumarate in recent years. It was

shown that pigs nursing sows receiving ferrous fumurate in their rations had higher

hemoglobin levels. However, it is now pretty well established that this was not

caused by an increase of iron in the sow's milk. The data indicate that the pigs

received the iron from the sow's feces or from her diet. Cornell workers (6) were

not able to increase the iron content of milk when they fed 1,984 ppm of ferrous

fumarate in the sow's ration. Thus, it appears that finding an iron compound which

will appreciably increase the level of iron in the sow's milk still eludes us.

Purdue (5) recently compared ferrous fumarate versus ferrous sulfate in a

creep ration for pigs from birth to three weeks of age. The pigs fed the ferrous

sulfate were slightly heavier (22 vs. 20 lbs.) and had a higher hemoglobin level

(11.4 vs. 9.7) at three weeks of age. Thus, the ferrous sulfate seemed to be at

least as good as ferrous fumarate and its cost is considerably less. The Illinois

Station (4) also showed that pigs receiving ferrous sulfate mixed with their Illinois

16 ration gained faster than the pigs on other iron treatments. Thus, present know-

ledge does not show any special advantage for ferrous fumarate over other iron com-

pounds which are effective sources of iron supplementation.

The iron requirement of the baby pig is somewhere between 60 to 125 ppm. The

National Research Council (2) has established 80 ppm as the requirement. English

workers (7) have shown that the young pig must retain 21 mg. of iron per kg. of live-

weight increase in order to maintain a satisfactory level of iron. Suitable iron

preparations, injected at levels of 150 to 200 mg. into baby pigs at 1 to 3 days

of age, will prevent anemia due to iron deficiency. Uith present knowledge there

should be no reason for iron deficiencies to occur. However, they are still being

found on many farms throughout the country.

Zinc

Parakeratosis or dermatosis can be prevented or cured by zinc. High levels of

calcium increase the need for zinc in some manner as yet unknown. The data in





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table 1 show the zinc requirements to be 50 ppm in the ration. If excess calcium

is used, then higher levels of zinc may be needed. Studies at Yichigan (8) showed

that when the calcium becomes too excessive (1.5 to 2.0 per cent in the ration) the

use of zinc at 100 ppm will not always completely prevent the growth depression and

poor feed conversion associated with parakeratosis, although it will prevent the

typical skin lesions. Since so many pigs still receive more calcium than they need,

it is recommended that levels of at least 100 ppm of zinc be used in swine rations.

This level might be even increased to 125 to 150 ppm if for some reason the level

of calcium used may be too high.

The writer recently spoke at a conference in Indiana attended by over 100

practicing veterinarians. Over one-third of them indicated they were still seeing

parakeratosis on swine farms in various Midwest states. This indicates that we must

make an even greater effort to control this disease which can be easily done with

proper levels of zinc.

There is some interrelationship between the copper and zinc needs. Under

certain conditions copper will alleviate some of the symptoms of parakeratosis in

the pig.

Purdue workers (9) showed that the zinc in soybean protein is less available

than that in casein. This is due to the phytic acid in soybean protein forming a

complex (chelation) which makes the zinc less available. This is a good example

to point out the fact that a chemical analysis of a feed is only a guide as to the

availability of that nutrient to the animal. There is a difference between the avail-

ability of a nutrient as determined by a chemical analysis or a microbiological

assay and as determined by the use the pig will make of it. Thus, the only sure way

to know whether a ration lacks a certain nutrient is to add it to the ration and

determine whether or not the addition is beneficial. This does not mean that feed

analyses are not valuable. They definitely are. It does point out, however, that






-7-


they should be used as a guide and not as the final answer always.

Selenium

In the past, selenium has been thought of only as a toxic substance. Then it

was found to prevent a yellowish-brown discoloration of the body fat, necrosis of

the liver and death in the young pig. Of considerable importance is the fact that

both selenium and vitamin E prevented these symptoms which indicates an interrelation-

ship between the two in this syndrome. One must be very careful in using selenium,

however, since 1/10 ppm is beneficial, whereas 5 to 10 ppm will cause some toxic

effects.

New Zealand workers (10) have reported that selenium has been helpful in at

least 20 piggeries. Except where complicating factors have occurred, their losses

have been stopped by giving the pigs an oral dose of 5 mg. of selenium.

Magnesium

The magnesium requirements are shown in table 1. As far as is known, however,

there is still no need to supplement practical rations with magnesium since they

contain adequate amounts.

Iodine

The best way to supply it is through the use of iodized salt which has been

stabilized to protect the iodine from destruction. Florida studies have shown that

excess iodine is harmful to rabbits, hamsters and rats (25). Swine were not affected

by levels which were toxic to rabbits and rats. Since excess iodine, even for short

periods of time can be toxic, these studies indicate that caution should be used in

avoiding excesses. It should be pointed out, however, that levels of hundreds of

times the required amount were needed to get harmful effects.

Cobalt

It is doubtful if cobalt needs to be added to swine rations if they contain

adequate amounts of vitamin B12.




-8-


Manganese

The exact level of manganese needed in swine rations is not known. The levels

shown in table 1 can be used as a guide. Excess manganese is toxic, however, and

caution should be used in feeding too high a level. There are indications that

excess calcium and phosphorus will increase the need for manganese. This is an area

which needs more study with the pig.

Beef cattle mineral needs

Following are some recent developments on the mineral requirements of beef

cattle.

Copper

Copper deficiencies have been encountered in Florida, California, Nevada and

other areas. They can be found where the soil is low in copper or where excess

molybdenum is present. Excess molybdenum in the forage increases the need for

copper. In Florida, where it is assumed that cattle will consume from 35 to 40

pounds yearly of a complete mineral mixture, the copper is added to the complete

mineral mixture as follows:

(1) For organic (muck) soils 0.75% copper (or 3.0% copper sulfate)

(2) For mineral (sandy) soils 0.15% copper (or 0.6% copper sulfate)

These recommended levels of copper should be adjusted up or down if the rate

of mineral consumption varies much from 35 to 40 pounds per animal yearly. The

higher level of copper recommended for the organic soils is to counteract the effect

of excess molybdenum in those soils.

A recent Florida study showed that the toxicity of copper sulfate is related to

the manner in which it is given to cattle. Levels as high as 8.0 grams of copper

sulfate per animal daily were administered in a dry form to steers for 12 months,

followed by 12.0 grams to the same steers for the next 12 months with no toxic effect.

Twelve grams a day given in a water drench, however, was lethal to two animals





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within 65 days. These levels compare to the recommended minimum average daily in-

take of copper of 1/8 of a gram (or 1/2 gram of copper sulfate) per animal in the

organic soil pastures in Florida.

The best means of diagnosing copper deficiency in cattle is to chemically

analyze a sample of liver tissue. The values in table 2 indicate when a deficiency

exists.

Molybdenum

Areas with excess molybdenum have been shown to occur in Florida, California,

Nevada and elsewhere. Excess molybdenum increases the need for copper. Supplementa-

tion with copper will counteract excess molybdenum. It is necessary, however, to

have adequate sulfate present to control molybdenum toxicity by copper in the ration.

The copper requirements of cattle appear to be between 4 to 8 ppm in the total

ration. With good fertilization practices the copper content of forages seldom

exceeds 9 to 12 ppm. This level of copper will not prevent molybdenum toxicity

when the forage contains above 4 to 6 ppm of molybdenum. Molybdenum levels in

forage from the organic (muck) soils in Florida varies from 3 to 20 ppm. These

figures emphasize the need for continuous supplementation with extra copper in the

mineral mixtures in excess molybdenum soil areas in Florida. Copper deficiencies

will usually occur when the level of molybdenum exceeds 3 ppm and the copper level

is below 5 ppm in the feed.

Molybdenum is most readily available to plants under alkaline conditions of

the soil which also reduces the availability of copper. Therefore, molybdenum

toxicity is more a problem of alkaline than of acid soils.

Cobalt

Cobalt is an essential part of vitamin B12 and the normal requirements

of this vitamin are met by rumen synthesis if adequate cobalt is available in

the ration. Vitamin B12 injection will also relieve a cobalt deficiency. Many

grazing areas in Florida are deficient in cobalt. Cobalt deficiencies have





- 10 -


also been shown to occur in Michigan, Wisconsin, l ew Hampshire, ;New York, North

Carolina and Western Canada. Other areas of the U.S. are also thought to be

deficient in cobalt.

In Florida it is recommended that complete mineral mixtures should contain

0.03 per cent cobalt (0.12 per cent cobalt sulfate). This will satisfy cobalt

needs if the cattle consume 35 to 40 pounds of the complete mineral mixture annually.

This recommended level of cobalt should be adjusted up or down if the rate of min-

eral consumption varies much from 35 to 40 pounds per animal yearly.

Cobalt deficiency is often difficult to diagnose. Liver values shown in table

2 can be used as a guide as to when a deficiency exists. Cattle respond quickly

to cobalt treatment so this is a good indicator of a deficiency.

Iron

Recent Florida data (13) showed that iron oxide is very poorly available to

the animal. When iron sulfate was assigned a value of 100, the relative avail-

ability of iron oxide was only 4 per cent. On the other hand, when both sources

of iron were applied to the soil and then fed via St. Augustine grass, the iron oxide

availability was increased to 80 per cent that of iron sulfate. This is a good

example to show that a plant, through its own metabolism, can change the availability

of a mineral element for the animal.

The use of supplementary iron is recommended in Florida because some sandy soils

are low in iron and many cattle carry a heavy internal and external parasite load.

A number of investigators have tried iron injections with cattle to see if it

would benefit them. Negative results have been obtained to date. The Arizona

Station (18) actually showed that reduced gains were obtained when iron injections

(1 and 3 gram levels) were given 364 pound calves fed for 169 days in dry lot.

The Purdue Station (26) also showed that the injection of 1 gram of iron at the

beginning and on the 119th day of an experiment decreased rate of gain of fattening

steers.






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Zinc

Zinc has been shown to be a dietary essential for cattle. The Purdue Station

(14) has shown increased gains in fattening cattle with zinc supplementation. Aver-

age daily gains were increased 0.2 of a pound when zinc oxide was added at either

138 or 235 ppm of zinc in the total ration. Workers in Finland (24) have reported

an itch, hair licking, alopecia and general unthriftiness with cattle which occurred

due to a deficiency of zinc if the copper level is low and the calcium level is

high. More studies are needed with beef cattle to more clearly define its need

under U.S. conditions. Preliminary indications are that it will be needed under

certain conditions.

Magnesium

Grass tetany has become a serious problem in the last few years in South

Georgia and Alabama and parts of North Florida (16). It has occurred with small

grain (oats and rye) pastures during the winter and spring. Dr. Poitevint (17)

reported that practicing veterinarians have also experienced isolated cases of grass

tetany on millet and other temporary grazing crops during the summer and early fall

in South Georgia and Alabama. These cattle show very low serum magnesium levels of

0.5 to 1.0 mg. per cent. A complete mineral mixture containing 14 per cent magnes-

ium has been effective in preventing the condition. The cattle need to get about

15 grams of magnesium daily.

Grass tetany also occurs in other areas of the country. A condition referred

to as wheat poisoning has been reported with cattle in the Texas panhandle and

adjacent areas. In many cases, what is referred to as grass tetany is not just a

simple magnesium deficiency but may be a complicated problem involving other fac-

tors.

The magnesium problem is not a simple one to understand. Research is needed

to provide information necessary to fully understand this syndrome.





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Manganese

Washington Station workers (15) recently reported that a deficiency of manganese

in the cow caused the birth of calves with enlarged joints, stiffness, twisted legs

and a general physical weakness. The deficient cows, although exhibiting regular

estrous cycles, required an average of four services per conception as compared to

two for the controls. Rate of gain, feed efficiency and feed consumption of the

cow was not affected by the manganese deficiency. The control ration contained

25.1 ppm of manganese. Manganese deficiency symptoms were obtained with manganese

levels of 15.8 and 16.9 ppm. Thus, a level of 25.1 ppm was adequate for reproduc-

tion, but the exact level needed is not known.

Selenium

The Purdue Station obtained increased rate of gain and feed efficiency by

feeding 1 mg. of selenium per steer daily in 1964 but not in 1965 (20,21). The

Iowa Station (22) likewise reported a benefit from using selenium at 0.1 ppm in the

ration of fattening steers in 1962 and 1963 but not in 1964. The year differences

in response could be due to the ration containing enough selenium during the years

when no response was obtained although the reason could be more complicated than

this.

Some reports have occurred of selenium deficiency occurring under natural feed-

ing conditions in Florida, Oregon and other Western States. Selenium has been

helpful with white muscle disease in calves. In Florida, the condition has occurred

occasionally with calves from beef cows on good clover pastures.

The selenium story is now starting to unfold. This mineral element needs care-

ful study and observation to determine its importance and role in supplementing

animal rations.

Sulfur

A recent trial by Iowa Station workers (19) showed that feeding sulfur (0.03

lb. of sulfur per animal daily as sodium sulfate) increased gains 6 per cent and





- 13 -


feed efficiency 3 per cent and decreased cost of gain by 3 per cent. The sulfur

was added to a steer fattening ration containing high level of urea. The Iowa

workers caution that additional trials are needed to verify this preliminary finding.

As urea is used as a larger part of the ration, there is the possibility that

sulfur may be lacking with certain types of rations. The rumen bacteria can utilize

the sulfur to build the sulfur containing amino acids. Without sulfur these amino

acids cannot be synthesized by the rumen microorganisms. A complete ration should

contain a ratio of 15 parts of nitrogen to 1 part of sulfur.

Potassium

As high concentrate and low roughage rations increase in use for finishing

cattle, the possible need for potassium supplementation with certain rations should

be investigated. The grains are lower in potassium than roughages and as the rough-

age content of rations decreases or is even eliminated in some cases, the possibility

of a potassium deficiency could occur.

Guide on blood and liver mineral levels

Table 2 gives values which the Florida Station (23) has established as a guide

on the approximate normal level of mineral elements in the blood and liver. Infor-

mation is also given on the approximate level below which a deficiency begins and

below which an extreme deficiency exists. These figures can be used as a guide by

those working with cattle.






- 14 -


Table 2. Blood* and Liver** Values of Minerals in Cattle
to Use As a Guide


Approximate
Approximate level at
level below which an
Approximate which a extreme
Mineral normal deficiency deficiency
Element level begins exists


Calcium
Blood plasma

Phosphorus
Blood plasma

Copper
Blood, whole
Liver


Cobalt
Blood, whole
Liver

Iron
Blood hemoglobin
Liver

Potassium
Blood, whole

Sodium
Blood, whole

Magnesium
Blood, whole

Manganese
Blood, whole


Zinc
Blood, whole


10-12 mg.


5-8 mg.


0.75-1.00 ppm.
100-300


0.0004 ppm.
0.2


10-13 gm.
200-300


66 mrg.


256 mg.


2.04 mg.


0.002 mg.


0.88 mg.


*All blood values are per 100 ml. of blood.
**All liver values are in ppm. on a dry matter basis.


8 mg.


5 mg.


6 mg.


2-3 mg.


0.07


0.25 ppm.
25


0.04
0.04


6-8


52


244


0.1-0.4


----





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Literature Cited

1. Crock, L., W. G. Pond and U. R. Brown. 1965. Proceedings of Cornell Nutrition
Conference. Page 18.

2. Beeson, W. 11., D. E. Becker, E. U. Crampton, T. J. Cunha, N. R. Ellis and R. U.
Luecke. 1964. National Research Council Publication 1192. Washington, D. C.

3. Veum, T. L., J. T. Gallo, a. G. Pond, L. D. Van Vleck and J. K. Loosli. 1965.
J. Animal Sci. 24:1169.

4. Harmon, B. G., H. F. Nickelson, A. H. Jensen and D. E. Becker. 1965. Illinois
Agr. Exp. Sta. AS-623.

5. Froseth, J. A., R. A. Pickett, W. Pt. Beeson and AI. P. Plumlee. 1965. Purdue
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6. Pond, W. G., T. L. Veum and V. A. Lazar. 1965. J. Animal Sci. 24:668.

7. Braude, R., A. G. Chamberlain, i. Kotarbinska and K. G. iHitchell. 1962. British
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8. Luecke, R. 1957. Abstracts of Texas Nutrition Conference.

9. Smith, W. H., M. P. Plumlee and W. H. Beeson. 1961. J. Animal Sci. 20:128.

10. Hartley, TT. J. and :. Grant. 1U61. Federation Proceedings. 20:679.

11. Smith, D. L. T. 1957. Amer. J. Vet. Res. 18:825.

12. Chapman, H. L., Jr. and R. W. Kidder. 1964. Florida Agr. Exp. Sta. Bul. 674.

12. Ammerman, C. B. 1965. Feedstuffs 37:18.

14. Smith, U. H., W. M. Beeson, T. H. Perry, P. B. Harrington and Y. T. MIohler.
1963. Purdue Agr. Exp. Sta. Feeders Day Rep.

15. Rojas, M. A., I. A. Dyer and W. A. Cassatt. 1965. J. Animal Sci. 24:664.

16. Miller, J. G. 1965. Proceedings of Georgia Nutrition Conference. Page 1.

17. Poitevint, L. 1965. Proceedings of Florida Nutrition Conference. Page 28.

18. Hale, W. H., B. Taylor, F. Hubbert, Jr., and W. J. Saba. 1964. Arizona
Cattle Feeders Day Rep. Page 15.

19. Burroughs, W., W. Kuhl, D. Wolf, J. Shively and A. Trenkle. 1965. Iowa Agr.
Exp. Station AS Leaflet R71.

20. Beeson, 1. M., M. T. Mohler and T. U. Perry. 1964. Purdue Agr. Exp. Sta.
Cattle Feeders Day Rep.

21. Smith, W. P., W. N. Beeson, 1i. T. l1ohler, R. B. Harrington and T. W. Perry.
1965. Purdue Agr. Exp. Sta. Cattle Feeders Day Rep.





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22. Burroughs, W., R. Kohlmeier, R. Barringer, J. Shively, A. Mukhtar and A. Trenkle.
1964. Iowa Agr. Exp. Sta. Cattle Feeders Day Rep.

23. Cunha, T. J., R. L. Shirley, H. L. Chapman, Jr., C. B. Ammerman, G. K. Davis,
W. G. Kirk and J. F. Hentges, Jr. 1964. Florida Agr. :xp. Sta. Bul. 683.

24. Haaranen, S. 1965. Uord Vet. Hed. 17:36.

25. Arrington, L. R., R. N. Taylor, Jr., C. B. Ammerman and R. L. Shirley. 1965.
J. Nutrition 87:394.

?6. Smith, U. I., T. W. Perry, M. T. Mohler, H. E. Parker and U. n. Beeson. 1963.
J. Animal Sci. 22:1131.










































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