Non-protein nitrogen, phosphorus and magnesium in ruminant nutrition

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Non-protein nitrogen, phosphorus and magnesium in ruminant nutrition
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Hillis, William Gordon, 1944-
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Table of Contents
    Title Page
        Page i
    Acknowledgement
        Page ii
        Page iii
    Table of Contents
        Page iv
        Page v
    List of Tables
        Page vi
        Page vii
        Page viii
        Page ix
        Page x
        Page xi
    List of Figures
        Page xii
        Page xiii
    Abstract
        Page xiv
        Page xv
        Page xvi
    Chapter 1. Introduction
        Page 1
        Page 2
    Chapter 2. Literature review
        Page 3
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    Chapter 3. Effect of levels and sources of supplemental nitrogen on voluntary feed intake, average daily gain and blood urea-N in steers
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    Chapter 4. Nitrogen source and rumen ammonia, pH and blood urea-N
        Page 46
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    Chapter 5. The phosphorus availability in monoammonium and monosodium phosphates for growing lambs
        Page 70
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    Chapter 6. Effect of age and dietary level of magnesium on magnesium utilization by sheep
        Page 80
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    Chapter 7. General summary
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    Appendix
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    Bibliography
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Full Text












Non-protein Nitrogen, Phosphorus and
Magnesium, in Ruminant Nutrition












by

WILLIAM GORDON HILLIS


A DISSERTATION PRfTJj,-':0 .) TO THE GRADUATE COUNCIL OF
THE UNIVERSITY OF FLORIDA IN PARTIAL
FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY






UNIVERSITY OF FLORIDA
1971















A.- i.:: ;.:LEDGU1.tTS


Sincere appreciation is extended to Dr. C. B.

Ammerman, Chairman of the Supervisory Committee, for his

support and guidance throughout the academic program and

experimental investigations; and also to Drs. J. E. Moore,

J. A. Himes, R. H. Harms and C. M. Alien, Jr. for serving

as members of the supervisory committee and for giving

freely of their time and knowledge toward the completion of

this work.

The author is grateful for the assistance given him

by many of the graduate students, particularly Larry T.

Watson and Karl R. Fick. Sincere appreciation is also

expressed for the technical assistance of Mrs. Sarah Miller,

Mr. John F. Easley and other members of the staff of the

.litrition Laboratory. The assistance provided by Mr. Phil

H[licks in caring for experimental animals is acknowledged.

Special appreciation is expressed to International

Minerals and Chemical Corporation, Skokie, Illinois, and

the National Feed Ingredients Association, Des Moines, Iowa,

for providing financial assistance for this work. The

provision of experimental supplies by Charles Pfizer and

Co., Inc., Terre Haute, Indiana, American Cyanamid Company,

Princeton, New Jersey and Monsanto Chemical Co., St. Louis,

Missouri is acknowledged.









Sincere appreciation is extended to Mrs. Ella Mae

Huber for typing this manuscript.

The author is especially grateful to his wife, Wilma,

for her help and inspiration during this period of academic

endeavor. To her this work is dedicated.


iii
















TABLE OF COii'ENTS


Pige
AC.. I J OWLEDGMEiNTS . . . . . . . . . ii

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

LIST OF FIGURES . . . . . . . . .. xii

ABSTRACT . . . . . o. . . . . xiv

CHAPTER
I INTRODUCTION . . . . . . . . .1

II LITERATURE RVIEW . . . . . . 3

Non-protein Nitrogen Utilization by
Ruminants . . . .................. 3
Inorganic Phosphate Supplements for
Ruminants . . . .................. 9
Effect of Age on Magnesium Utilization. . 14
Magnesium Requirement and Availability. . 17

IIi EFFECT OF LEVELS AND SOURCES OF SUPPLEMENTAL
NITROGEN ON VOL:j:'A-\,' FEED INTAKE, AVERAGE
DAILY GAIN AND BLOOD UREA-N IN STEERS . 28

Procedure and Results . . . . .. 29

ExperiAcnt 1---Effect of Supplemental
Nitrogen as Soybean Meal, DAP, Urea and
DAP Plus Urea on Voluntary Feed Intake
and Average Daily Gain in Steers. .. 29
Experiment 2 --.Effect of Supplemental
Nitrogen as Soybean Meal, DAP and Two
Levels of MLAP on Voluntary Feed Intake,
Average Daily Gain and Blood Urea-N in
Steers . . . . . 31
Experiment 3---Effect of Supplemental
Nitrogen as Soybean Meal, DAP and Two
Levels of MAP on Voluntary Feed Intake,
Average Daily Gain and Blood Urea-N in
Steers . . . . . . . .. .37













Experiment 4--Effect of Supplemental
Nitrogen as Soybean Meal, DAP and
Two Levels of MAP on Voluntary Feed
Intake, Average Daily Gain and Blood
Urea-N in Steers . . . . ... .40

Discussion . . . . . . . . 44

IV NITROGEN SOURCE AND RUMEN AMMONIA, pH AND
BLOOD UREA-N . . . . . . ... 46

Procedure and Results . . . . .. 46

Experiment 1--Effect of Nitrogen Source
on Rumen Ammonia, pH and Blood Urea-N 46
Experiment 2--Effect of Nitrogen Source
and Supplemental Acid or Base on Rumen
Ammonia, pH and Blood Urea-N ..... 57

Discussion . . . . . . . .. .64

V THE PHOSPHORUS AVAILABILITY IN :iON,:.t14ONfUMJ
AND MONOSODIUM PHOSPHATES FOR GRCI.UG G LAMBS 70

Procedure and Results . . . . .. 70
Discussion . . . . . . . .. .78

VI EFFECT OF AGE AND DIETARY LEVEL OF MAGNESIUM
ON MAGNESIUM UTILIZATION BY SHEEP ... . 80

Procedure and .Results . . . . .. 80
Discussion . . . ... . . . . 108

VII GENERAL SUMMARY . . . . . . .. 115

Influence of Non-protein Nitrogen Source
on Feed Intake, Animal Performance and
Blood Urea-N . .. ........ . . 115
Effect of Nitrogen Source on Certain
Blood and Ruminal Fluid Constituents, 116
Relative Availability of Phosphorus in
Two Inorganic Phosphorus Sources. .. 117
Influence of Age and Dietary Magnesium
Level on Magnesium Utilization ..... 117

APPENDIX . . . . . . . . . . . 120

BIBLIOGRAPHY . . . . . . . . . . 159

BIOGRAPHICAL SKETCH . . . . . . . .. 168


Page


CHAPTER
















LIST OF TABLES


TABLE Page

1 COMPOSITION OF DIETS . . . . . .. 30

2 EFFECT OF SOURCE OF NITROGEN ON FEED
CONSUMPTION AND AVERAGE WEIGHT GAIN ..... 32

3 COMPOSITION OF DIETS . . . . . .. 34

4 EFFECT OF SOURCE OF NITROGEN ON FEED
CONSUMPTION, AVERAGE WEIGHT GAIN AND BLOOD
UREA-N (BUN) . . . . . . . . 35

5 COMPOSITION OF DIETS . . . . . .. 38

6 EFFECT OF SOURCE OF NITROGEN ON FEED
CONSUMPTION, AVERAGE WEIGHT GAIN AND BLOOD
UREA-N (BUN) . . . . . . . . 39

7 COMPOSITION OF DIETS . . . . . .. 41

8 EFFECT OF SOURCE OF NITROGEN ON FEED
CONSUMPTION, AVERAGE WEIGHT GAIN AND BLOOD
UREA-N (BUN) . . . . . . . . 43

9 COMPOSITION OF DIET... . . . . . . 48

10 EFFECT OF A SINGLE DOSE OF SOYBEAN MEAL, UREA,
DIAMMONIUM PHOSPHATE OR MONO.MMTONIUM
PHOSPHATE ON RUMEN pH . . . . ... 49

11 EFFECT OF A SINGLE DOSE OF SOYBEAN MEAL, UREA,
DI \!?Y1TI.'M PHOSPHATE OR MONOAMMONIUM
PHOSPHATE ON RUMEN AMMONIA-N . . . .. 52

12 EFFECT OF A SINGLE DOSE OF SOYBEAN MEAL, UREA,
DIAflMO2IUM PHOSPHATE OR MONOAMMONIUM
PHOSPHATE ON BLOOD UREA-N . . . .. 55

13 EFFECT OF A SINGLE DOSE OF UREA, UREA PLUS
PHOSPHORIC ACID, MOWING NOMIUM PHOSPHATE, OR
MONOAMMONIUM PHOSPHATE PLUS SODIUM CARBONATE
ON RUMEN pH . . . . . . . .. .59















14 EFFECT OF A SiMG. DOSE OF UREA, UREA PLUS
PHOSPHORIC ACID, MONOAMMONIUM PHOSPHATE,
OR MONO-'iO-!:I JUM PHOSPHATE PLUS SODIUM
CARBONATE ON RUMEN A: '!ONiA-N . . ... 62

15 EFFECT OF A SINGLE DOSE OF UREA, UREA PLUS
PHOSPHORIC ACID, MONO'TIMOHTIUM PHOSPHATE,
OR MONOAMMONIUM PHOSPHATE PLUS SODIUM
CARBONATE ON BLOOD UREA-N . . . .. 65

16 COMPOSITION OF DIETS . . . . . .. 71

17 AVERAGE INITIAL AND FINAL WEIGHT, DAILY GAIN,
FEED INTAKE AND FEED EFFICIENCY OF LAMBS
FED DIl'Fl-RElT SOURCES AND LEVELS OF
PHOSPHORUS DURING A 9-WEEK GROWTH TRIAL . 74

18 AVERAGE PHOSPHORUS, CALCIUM AND MAGNESIUM
LEVELS IN PLASMA OF LAMBS FED DIFFERENT
SOURCES AND LEVELS OF PHOSPHORUS DURING A
9-WEEK GROWTH TRIAL . . . . . .. 76

19 AVERAGE MEASUREMENTS AND MINERAL CONCENTRA-
TIONS OF THE RIGHT FEMUR OF LAMBS FED
DIFFERENT SOURCES AND LEVELS OF PHOSPHORUS
DURING A 9-WEEK GROWTH TRIAL . . ... 77

20 COMPOSITION OF EXPERIMENTAL DIET .. ...... 82

21 AGE SPECIFICATIONS, BODY WEIGHTS AND FEED
OFFERED . . . . . . . . .. 83

22 EFFECT OF AGE AND DIETARY MAGNESIUM ON
APPARENT ABSORPTION OF MAGNESIUM, CALCIUM
AND PHOSPHORUS IN SHEEP . . . . . 86

23 EFFECT OF AGE AND DIETARY MAGNESIUMM ON NET
RETENTION OF MAGNESIUM, CALCIUM AND
PHOSPHORUS IN SHEEP . . . . . .. 88

24 EFFECT OF AGE AND DIETARY MAGNESIUM ON
URINARY EXCRETION AS PERCENT OF INTAKE OF
MLA-'i'SIUM, CALCIUM AND PHOSPHORUS IN SHEEP. 90

25 EFFECT OF AGE AND DIETARY MAGNESIUM ON
PLASMA LEVELS OF MAGNESIUM, CALCIUM AND
PHOSPHORUS IN SHEEP . . . . . .. 91


vii


Page


TABLE














26 INDIVIDUAL DATA ON EFFECT OF NITROGEN ON
FEED CONSUiPTION AND AVERAGE WEIGHT GAIN. 121

27 INDIVIDUAL DATA ON EFFECT OF SOURCE OF
NITROGEN ON FEED CONSUMPTION, AVERAGE
WEIGHT GAIN AND BLOOD UREA-N (BUN) .... 122

28 INDIVIDUAL DATA ON EFFECT OF SOURCE OF
NITROGEN ON FEED CONSUMPTION, AVERAGE
WEIGHT GAIN AND BLOOD UREA-N (BUN) .. . 123

29 INDIVIDUAL DATA ON EFFECT OF SOURCE OF
NITROGEN ON FEED CONSUMPTION, AVERAGE
WEIGHT GAIN AND BLOOD UREA-N (BUN) ... .. .124

30 INDIVIDUAL DATA ON RUMEN pH OF SHEEP DOSED
WITH SOYBEAN MEAL, UREA, DIAMMONIUM
PHOSPHATE OR MONOAMMONIUM PHOSPHATE . . 125

31 INDIVIDUAL DATA ON RU.'-ME AMMONIA-N OF SHEEP
WITH SOYBEAN MEAL, UREA, DIAII-,0;IIUM
PHOSPHATE OR MONOAMMONIUM PHOSPHATE . . 126

32 INDIVIDUAL DATA ON BLOOD UREA-N OF SHEEP
DOSED WITH SOYBEAN MEAL, UREA, DIAMMONIUM
PHOSPHATE OR MONOAMMONIUM PHOSPHATE . .. 127

33 INDIVIDUAL DATA ON RUMEN pH OF SHEEP DOSED
WITH UREA, UREA PLUS PHOSPHORIC ACID,
MONOAMMONIUM PHOSPHATE OR MONOAMMONIUM
PHOSPHATE PLUS SODIUM CARBONATE . . .. .128

34 INDIVIDUAL DATA ON RUMEN AIIMONIA-N OF SHEEP
DOSED WITH UREA, UREA PLUS PHOSPHORIC
ACID, MONOAMMONIUM PHOSPHATE AND
:1IONOAMMIONIUM PHOSPHATE PLUS SODIUM
CARBONATE . . . . . . . . 129

35 INDIVIDUAL DATA ON BLOOD UREA-N OF SHEEP
DOSED WITH UREA, UREA PLUS PHOSPHORIC
ACID, MONOAMMONIUM PHOSPHATE OR
MONOAMMONIUM PHOSPHATE PLUS SODIUM
CARBONATE . . . . . . . .. 130

36 INDIVIDUAL DATA ON DAILY GAIN, FEED INTAKE
AND FEED EFFICIENCY OF LAMBS FED DIFFERENT
SOURCES AND LEVELS OF PHOSPHORUS DURING A
9-WEEK GROWTH TRIAL . . . . . .. 131


viii


Page


TABLE














37 INDIVIDUAL DATA ON PHOSPHORUS LEVEL IN
PLASMA OF LAMBS FED DIFFERENT SOURCES
AND LEVELS OF PHOSPHORUS DURING A 9-
WEEK GROWTH TRIAL . . . . . .. 132

38 INDIVIDUAL DATA ON CALCIUM LEVEL IN PLASMA
OF LAMIS FED DIFFERENT SOURCES AND LEVELS
OF PHOSPHORUS DURING A 9-WEEK GROWTH TRIAL. 133

39 INDIVIDUAL DATA ON MAGNESIUM LEVEL IN
PLASMA OF LAMBS FED DIFFERENT SOURCES AND
LEVELS OF PHOSPHORUS DURING A 9-WEEK GROWTH
TRIAL . . . . . . . . .. 134

40 INDIVIDUAL DATA ON MEASURE-IE:.:NTS AND MINERAL
CONCENTRATIONS OF THE RIGHT FEMUR OF LAMBS
FED DIFFERENT SOURCES AND LEVELS OF
PHOSPHORUS DURING A 9-WEEK GROWTH TRIAL . 135

41 INDIVIDUAL DATA ON MEASUREMENT AND MINERAL
CO?4CZNT2RATIONS OF THE RIGHT FEMUR OF LAMBS
FED DIFFERENT SOURCES AND LEVELS OF
PHOSPHORUS DURING A 9-WEEK GROWTH TRIAL . 136

42 INDIVIDUAL DATA ON EFFECT OF MAGNESIUM
INiTAKE BY LAMBS ON PERCENT APPARENT
ABSORPTION OF :*L\:;iwSIUM, CALCIUM AND
PHOSPHiORUS . . . . . . . . 137

43 INDIVIDUAL DATA ON EFFECT OF MAGNESIUM
INTAKE BY YEARLINGS ON PERCENT APPARENT
ABSORPTION OF MAGNESIUM, CALCIUM AND
PHOSPHORUS . . . . . . . .. 138

44 INDIVIDUAL DATA ON EFFECT OF MAGNESIUM
INTAKE BY ADULTS ON PERCENT APPARENT
ABSORPTION OF MAGNESIUM, CALCIUM AND
PHOSPHORUS . . . . . . . .. 139

45 INDIVIDUAL DATA ON EFFECT OF MAGNESIUM
INTAKE BY LAMBS ON PERCENT NET RETENTION
OF MAGNESIUM, CALCIUM AND PHOSPHORUS ... 140

46 INDIVIDUAL DATA ON EFFECT OF MAGNESIUM
INTAKE BY YEARLINGS ON PERCENT NET
RETENTION OF MAGNESIUM, CALCIUM AND
PHOSPHORUS . . . . . . . .. 141


Page


TABLE














47 INDIVIDUAL DATA ON EFFECT OF MAGNESIUM
IiT'l -KF BY ADULTS ON PERCENT NET
RETENTION OF MAC1'-.SIUM, CALCIUM AND
PHOSPHORUS . . . . . . . .. 142

48 INDIVIDUAL DATA ON EFFECT OF MAGNESIUM
IfYTAIRE BY LAMBS ON URINARY EXCRETION OF
7AG:ESIUM, CALCIUM AND PHOSPHORUS, % OF
INTAKE . . . . . . . . .. 143

49 INDIVIDUAL DATA ON EFFECT OF MAGNESIUM
I;JTA?:E BY YEARLINGS ON URINARY
EXCRETION OF MAGNESIUM, CALCIUM AND
PHOSPHORUS, % OF INTAKE . . . . .. .144

50 INDIVIDUAL DATA ON EFFECT OF MAGNESIUM
I-'TAKE BY ADULTS ON URINARY EXCRETION OF
MAGNESIUM, CALCIUM AND PHOSPHORUS, % OF
INTAKE . . . . . . . . .. 145

51 INDIVIDUAL DATA ON EFFECT OF MAGNESIUM
INTAKE BY LAMBS ON PLASr-A LEVELS OF
MAGNESIUM, CALCIUM AND PHOSPHORUS
(MG/100 ML) . . . . . . . . 146

52 INDIVIDUAL DATA ON EFFECT OF MAGNESIUM
I;TTAKE BY YEARLINGS ON PLASMA LEVELS OF
MAGNESIUM, CALCIUM AND PHOSPHORUS (MG/100
ML) . . . . . . . . .. 147

53 INDIVIDUAL DATA ON EFFECT OF MAGNESIUM
INTAKE BY ADULTS ON PLASMA LEVELS OF
MAGNESIUM, CALCIUM AND PHOSPHORUS
(MG/100 ML) . . . . . . .. 148

54 INDIVIDUAL DATA ON RELATION OF FECAL
MAGNESIUM TO MAG"JESIUM INTAKE PER 1,000
KILOCALORIES OF METABOLIZABLE ENERGY
INTAKE PER DAY . . . . . . ... 149

55 INDIVIDUAL DATA ON RELATION OF FECAL
.MAGrESIL'il TOp MAGNESIUM INTAKE PER
KILOGRAM0"75 BODY WEIGHT PER DAY ..... 150

56 INDIVIDUAL DATA ON RELATION OF FECAL
MAGNESIUM TO MAGNESIUM INTAKE PER
KILOGRAM BODY WEIGHT PER DAY . . ... 151


Page


TABLE












TABLE


57 INDIVIDUAL DATA ON RELATION OF URINARY
%.AGIESIU[* TO MAGNESIUM INTAKE PER
1,000 KILOCALORIES OF METABOLIZABLE
ENERGY INTAKE PER DAY . . . . .. 152

58 INDIVIDUAL DATA ON RELATION OF URINARY
MAGNESIUM TO MAGNESIUM INTAKE PER
KILOGRAM0"75 BODY WEIGHT PER DAY ..... 153

59 INDIVIDUAL DATA ON RELATION OF URLihARY
MAGNFSTUM TO MAGNESIUM INTAKE PER
KILOGRAM BODY WEIGHT PER DAY . . ... 154

60 INDIVIDUAL DATA ON RELATION OF MAGNESIUM
OUTPUT (FECAL PLUS URINARY) TO MAGNESIUM
INTAKE PER 1,000 KILOCALORIES OF
METABOLIZABLE ENERGY INTAKE PER DAY . . 155

61 INDIVIDUAL DATA ON RELATION OF MAGNESIUM
OUTPUT (FECAL PLUS URINARY) TO MAGCIESIUM
INTAKE PER KILOGRAM0-75 BODY WEIGHT PER
DAY . . . . . . . . . .. 156

62 INDIVIDUAL DATA ON RELATION OF MAGNESIUM
OUTPUT (FECAL PLUS URINARY) TO MAGNESIUM
INTAKE PER KILOGRAM BODY WEIGHT PER DAY . 157

63 INDIVIDUAL DATA ON RELATION OF URINARY
MAGNESIUM TO PLASMA MAGNESIUM. . ..... 158


Page















LIST OF FIGURES


FIGURE Page

1 EFFECT OF TREATMENTS ON RUMEN pH . . .. 50

2 EFFECT OF TREATMENTS ON RUMEN AMO .1IIA-N . 53

3 EFFECT OF TREATMENTS ON BLOOD UREA-N . . 56

4 EFFECT OF TREATMENTS ON RUMEN pH . . ... 60

5 EFFECT OF TREATMENTS ON RUMEN A2U1O1iA-N . 63

6 EFFECT OF TREATMENTS ON BLOOD UREA-N .. . 66

7 RELATION OF FECAL MAGNESIUM TO MAGNESIUM
INTAKE PER 1,000 KILOCALORIES OF
METABOLIZABLE ENERGY INTAKE PER DAY . . 93

3 RELATION OF FECAL MAGNESIUM TO MAGNESIUM
INTAKE PER KILOGRAM0.75 BODY WEIGHT PER
DAY . . . . . . . . . .. .95

9 RELATION OF FECAL MAGNESIUM TO MAGNESIUM
INTAKE PER KILOGRAM BODY WEIGHT PER DAY . 96

10 RELATION OF URINARY MAGNESIUM TO MAGNESIUM
INTAKE PER 1,000 KILOCALORIES OF
METABOLIZABLE ENERGY INTAKE PER DAY . . 97

11 RELATION OF URINARY MAGNESIUM TO MAGNESIUM
INTAKE PER KILOGRAM0"75 BODY WEIGHT PER DAY 99

12 RELATION OF URINARY MAGNESIUM TO MAGNESIUM
INTAKE PER KILOGRAM BODY WEIGHT PER DAY . 100

13 RELATION OF MAGNESIUM OUTPUT (FECAL PLUS
URINARY) TO MAGNESIUM TI-TAKE PER 1,000
KILOCALORIES OF METABOLIZABLE ENERGY
INTAKE PER DAY . . . . . . ... 102

14 RELATION OF MAGNESIUM OUTPUT (FECAL PLUS
URINARY) TO MAGNESIUM INTAKE PER
KILOGRAM0"75 BODY WEIGHT PER DAY ..... 104


xii












15 RELATION OF :iYrFSIUM OUTPUT- (FECAL PLUS
URINARY) TO MAGNESIUM INTAKE PER
KILOGRAM BODY WEIGHT PER DAY . . ... 106

16 RELATION OF URI:AR'l MAGIW]-SIU'I TO PLASMA
M4AGNESIUM . . . . . . . .. 107


xiii


Page


FIGURE










Abstract of Dissertation Presented to th3 Graduate Council
of the Uriversity of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy-

NON--PROTEIN NITROGEN, PHOSPHORUS AND
MAGNESIUM IN RUMINANT NUTRITION

By

William Gordon Hillis

August, 1971


Chairman: Dr. C. B. Ammerman
Major Department: Animal Science

Studies were conducted to obtain information on

certain nutritional aspects of non-protein nitrogen, phos--

phorus and magnesium in steers and sheep.

Four Latin square designed experiments were conducted

with steers to examine the effects of urea, diammonium

phosphate (DAP) and monoammonium phosphate (MAP) on feed

consumption, average daily gain and blood urea-N. In

Experiments 1 and 3 voluntary feed intakes were significantly

(P< .05) reduced with diets containing 1.5% DAP and in Ex-

periment 2 with a diet containing 2.3% MAP. Treatment diets

containing MAP consistently resulted in the lowest average

daily gains. At the end of each experimental period steers

were fasted 12 hours followed by 2 hours ad libitum con-

sumption of their respective treatment diets. The increase

in blood urea-N fol1cwing the 2-hour feedi ig period was

greater for treatments containing isonitrogenous levels of

non-protein nitrogen (1.5% DAP and 2.3% MAP) except in Ex-

periment 2 where 0.75% MAP resulted in the greatest blood

urea-N increase.
xiv









Two Latin square designed experiments were conducted

with fistulated sheep to study the effects of non-protein

nitrogen sources upon rumen ammonia-N, pH and blood urea-N.

All nitrogen sources were administered intraruminaliy as

10 gm of nitrogen per 45.4 kg body weight and rumen fluid

and jugular blood samples were taken at periodic intervals

thereafter. In the first experiment urea resulted in the

greatest (P <.05) increase in rumen pH, the least (P< .05)

increase in rumen ammonia-N concentration and the greatest

(P <.05) increase in blood urea-N. Converse responses

resulted with MAP and DAP was intermediate in effect.

Treatments in the second experiment consisted of urea, urea

plus H3PO4, MAP and MAP plus Na2CO3. Effects of alkali and

acid additions on rumen pH were of short duration. Blood

urea-N values for the urea and urea plus H PO treatments
3~ 4
were similar throughout the sampling period and values for

the treatments MAP and 4A'P plus Na 2CO3 were similar.

A balance trial was conducted with sheep of three

ages (lambs, yearlings and adults) receiving three dietary

levels of magnesium and a computed maintenance level of

energy intake. With increasing age, the retention of

calcium aid phosphorus decreased, apparent absorption of

calcium decreased, plasma inorganic phosphorus decreased

and excretion of phosphorus in urine increased. With in-

creasing intakes of dietary magnesium, there vzaw a decreased

retention of phosphorus and calcium, increased excretion of

calcium in urine and increased apparent absorption,

xv









retention, urinary excretion and.Llasma levels of magnesium.

By use of regression analysis (fecal magnesium on magnesium

intake) the theoretical values for metabolic fecal magnesium

were calculated for lamb.3, yearlings and adults to be:

170.91, 122.25 and 118.44 mg per 1,000 kilocalories of

metabolizable energy (ME) intake per day, respectively;

16.87, 13.95 and 12.30 mg per kg075 body weight per day,

respectively; 7.26, 5.48 and 4.25 mg per kg body weight per

day, respectively. From the regression equations of fecal

plus urinary magnesium on magnesium intake for each age

group the calculated minimum dietary requirements to replace

endogenous losses for lambs, yearlings and adults were:

261.07, 235.20 and 176.46 mg per 1,000 kilocalories of ME

intake per day, respectively; 28.84, 26.40 and 20.46 mg per

kg0.75 body weight per day, respectively; 12.56, 10.50 and

6.75 mg per kg body weight per day. respectively. These

values would be specific for the Lemi-purified diet fed

with supplemental magnesium provided as the carbonate. The

regressions of urinary magnesium on plasma magnesium gave

renal threshold values for lambs, yearlings and adults of:

1.38, 1.42 and 1.21 mg per 100 ml of plasma, respectively.


xvi















CHAPTER I


INTRODUCTION'


Maximum efficiency in animal production is dependent

upon providing o)timum quantities of all essential nutrients.

To obtain such efficiency, knowledge must be present of the

relative availabilities of nutrients in the various feed

ingredients and as wel1 the a:-ceptability to the aniraal of

the nutrient sources.

Although it has been adequately demonstrated that the

protein ne;ds of ruminants can be met by supplementing lheir

diets with non-prot-(in nitrogen, a p2:oblem still re.vains as

to the source of this form of nitrogen most desirable to use.

Certain forms of non-protein nitrogen have been found less

toxic tian the conrmonI y used compound, urea. How.vr, soae

of these less toxic forms, such as diammnionium phosphate,

have been repor,,d less acceptable to anirials than urea. An

advantage of using such compounds as disani-oniuri phos Lhate or

inonouinion-um phospiate is tlieir property of bcJ -.* a soun'ce

of both nci-protein nitrogen and sup'.-cep: ieta y pjho;p-usa.

A problem comIon to a"'. sources o s on-- prote

nitrogen is tLhir rapid reilca. e ol cd' : i:. i, th r:I :



contribute Lo the efficie11cy of its utili taUtion .i: the;

I









ru:men by prolonging .its availability to the rumen riccrobes

*for pro f n syn heis. Suppyi.ng Lhospate wth th<; ,orces

of 0_on-protein nit1,oge s tojht to buffer :tue p! nd

reduce a nonia atborptioi and nitrogen wast age.

Magnesium, which is only one of many minerals known

to be essential for maximum production efficiency, has been

the subject of considerable research in recent years. The

objective of a.any of the studies was to elucidate the role

of nmagnesium in hypomagnesaemtc tetany. It has been suggested

that the older animal is oore susceptible to this disease due

to a decreased abili.:y to mobilize skeletal magnesium with

age. Thus the older animal may be almost entirely dependent

on daily supplies of magnesium to maintain normal metabolism.

This research was conducted to evaluate several non-

protein nitroge-.n sources, and,as well, to investigate the

effect cf age on --agnesium utilization in ruminants. Urea,

dianmulonium phoshate and monouammonitm phosphate were

evaluated with respect to their relative acceptab- lities

by steer:- and their utilizations by steers and sheep. A

lamb growth and slaughter study was also conducted to

determine the availability of phosphorus from monoamnoniurm

phosphate. The effect of age on dietary magnesium utiliza-

tion was i'.amined in a balance study involving three age

levels of sheep.















CIHAPTER II


LITERATURE REVIEW


The literature dealing with non-protein nitrogen,

phosphorus and magnesium as they relate to animal nutri-

tion is extensive. Only those articles having a direct

relationship to the work conducted by the author and

giving a basic knowledge of the related areas will be

reviewed.


Non-protein Nitrogen Utilization by Ruminants


The protein needs of the world's expanding popula-

tion continue to receive the attention of nutritionists.

Protein supplements, which in the past have been used

routinely for supplementing ruminant rations, are now find-

ing new roles as protein sources for human nutrition. Such

uses may result in prices that will prohibit their use in

ruminant diets in the future. For this and other reasons

considerable research has been conducted on the use of non-

protein nitrogen sources as substitutes for natural protein

suppi ements./

Early work conducted by HIart et al. (1939) demonstrated

that dairy heifers could. utilize the nitrogen of urea for

growth and that adding soluble sugars to the diet improved









this utilization. Since that time much research has been

directed toward finding optimal conditions for efficient

utilization of non-protein nitrogen.

A major problems resulting in inefficient utilization

of urea is the rapid release of ammonia. Bloomfield,

Garner and Muhrer (1960) indicated that urea hydrolysis

occurred four times faster in the rumen than uptake of the

liberated ammonia by the microorganisms. The need for

adequate levels of readily-available carbohydrate for better

utilization of urea and other non-protein nitrogen com-

pounds has been well demonstrated (Arias et al., 1951;

Belasco, 1956; Bloomfield, Muhrer and Pfander, 1958;

Bloomfield, Wilson and Thompson, 1964; McLaren et al., 1965).

Rumen ammonia concentration, either singly or togeth-

er with other parameters, has often been used as a measure

of the hydrolyzability of nitrogen supplements or of the

relative mricrobial protein synthesis from such supplements.

It should be pointed out, however, that armmoni.a concentra-

tion in the rumen, just like that of any other rumen

metabolite, is dependent upon the following forces as

enumerated by Annison and Lewis (1959): rate of production,

rate of utilization by microbes, rate of absorption through

the rumen wall, dilution by saliva and water, and passage

to the omasum.

McDonald (1948), working with sheep, found much of

the excess ammonia which the microbes are not able to

utilize is absorbed from the rumen with some ammonia






5


absorption occurring in the omasum, lower part of the small

intestine and cecum.. Amrioinia absorption is governed by

both concentration gradient and pH. Lewis (1957) demonstrat-

ed that the portal blood ammonia concentration increased as

a curvilinear function of rumen ammonia content. Hogan

(1961), working with anesthetized sheep, also demonstrated

ammonia absorption to be dependent on the concentration

gradient when the rumen contents were maintained at a pH of

6.5, but ammonia loss was nil at pH 4.5. Bloomfield et al.

(1963), working with fistulated sheep, reported a reduction

in absorption of ammonia from 26 to 0 mM/L/hour when the

rumen pH1 was reduced from 7.55 to 6.21. Since ammonia is

a weak base with a pKa of 8.8 at 40WC, the increased

absorption of ammonia at a higher pH is probably the result

of an increase in the amount of the neutral and smaller

ammonia molecule, in relation to ammonium ion, which may

more readily penetrate the lipid layers of the rumen mucosa

(Coombe, Tribe and Morrison,' 1960; Hogan, 1961; Bloomfield

et al., 1963; Visek, 1968). Unfortunately, the alkaline

buffering capacity of rumen fluid is not as great as its

acid buffering capacity (Clark and Lombard, 1951; Ammerman

and Thomas, 1955; Bloomfield et al., 1966). Thus, condi-

tions in the rumen from urea feeding are conducive not only

to rapid production but also to increased absorption of

ammonia.

The use of non-protein nitrogen sources as partial

substitutes for natural protein has been limited by their










toxic effec..s in rumi .nants. Repp, Hale and _--.Ii.-'roughs (L955)

crnitically studJid rce and fu r oth r non-protei.n nitrogen

compounds for their, rel!;-tive oxicities to lambs Adminis-

tration of irea, ariuionium forrlate, ammoninim ace tate and

ammonium popionate at a level of about 40 gm urea equi-

valent per 45.4 kg of body weight resulted in fatal

toxicity. In all cases toxicity was associated with large

increases in blood ammonia nitrogen, with the critical

level being about 1 mg per 100 ml of blood.

Clark and Lomabard (1951) reported that sheep which

were adapted to a ration of lucerne hay were less suscep-

tible to urea toxicity than the ones adapted to a poor

quality grass hay diet. They observed a decrease or entire

cessation of ruminal motility as a result of the high rumen

pH caused by high ammonia concentration. Coombe et al. (1960)

observed a marked decrease in rumination time spent by sheep

when urea was added to their diets suggesting an inhibitory

effect on rumen motility. Like Clark and Lombard (1951)

they found that rumen pH had a large influence on this.

When sheep were fed hay before being drenched with 25 gm

urea, rumen pH did not exceed 6.3 and although the rurien

ammonia--N reached 91 mg per 100 ml, rumen movements were

not inhibited. HowIever, when fasted for 16 hours before

drenching, a dose of 10 gma urea resulted in a rise in runen

pH to 7.3 and complete cessation of rumen movements. W.en

17 gm ammonium h1ilori de were given instead of urea, the









rumen aruaonia-N level rose to an even higher value (132 mg

per 100 ml) buL the pH did not rise above 7.0 and rumen

movements were normal.

Russell, Hale and Huhbert, Jr. (1962), in toxicity

studies with lambs, found that a much higher level of

nitrogen from diamnonium phosphate (DAP) was necessary to

cause toxicity compared to urea. At a dose level of 15 to

20 units of compound (i.e., 15 to 20 gm urea or urea-

equivalent per 45.4 kg body weight), rumen pH of lambs rose

from 6.8 to 8.1 in one-half hour with urea and from 6.8 to

7.2 in the case of DAP. In steers dosed with 12 units of

either compound, the average blood ammonia-N levels rose

from an initial value of 0.13 mg per 100 ml to a peak in

one-half hour of 0.71 mg per 100 ml with urea as compared

to a rise from an initial level of 0.14 mg per 100 ml to

a peak in one-half hour of 0.25 mrg per 100 ml with DAP.

The above results indicate the influence of the buffering

action of phosphate on rumen pH and the absorption rate of

ammonia. This influence was demonstrated also by Perez,

Warner and Loosli (1967) when fistulated sheep were dosed

with urea, urea-phosphate and urea-plus phosphoric acid in

single doses of 20 units (20 gm urea or its equivalent in

nitrogen per 45.4 kg body weight). The amount of phosphoric

acid added to urea was calculated to provide the same

amount of phosphate as would be in 20 units of urea-

phosphate. The rumen pH rose from an initial value of 7.35

to a peak in 3 hours of 8.30 with the urea treatment. The









urea-phosphafte and urea-plus phosphoric acid treatments

had essentially identical pH trends with each dropping from

their initial values of 7.25 and 7.35 to pH 5.9 and 6.35,

respectively, at one-half hour postdosing. The urea treat-

ment, which had the highest rumen pH, resulted in the

lowest rumen ammonia-N and highest blood ammonia-N values

when compared with the two phosphate treatments.

The use of ammoniated phosphates has received in-

creased attention in recent years. Their chemical make-up

gives them a dual role as a source of both nitrogen and

phosphorus. One such compound is DAP. Russell et al. (1962)

found no significant difference in nitrogen retention be-

tween urea and DAP in balance trials -with lambs when each

source provided 31% of the total dietary nitrogen. However,

when 60% of the total dietary nitrogen of sheep rations was

supplied by urea or DAP, Oltjen et al. (1963) reported less

efficient utilization of the nitrogen from diammonium

phosphate. These workers also found rations containing DAP

to be less palatable to sheep during three growth trials.

They indicated that possibly saliva, coming in contact with

the feed, resulted in ammonia being released and the feed

being refused by the animals. Problems with palatability

were reported by Lassiter, Brown and Keyser (1962) when DAP

at levels greater than 2% was incorporated into the grain

rations of dairy cows. Similar palatability problems were

reported by Hale et al. (1962) when 1% of the ration for

steers was DAP.









Another ammoniated phosphate which has received only

limited attention is monoammonium phosphate (MAP). The

only study reported on this compound was that of Reaves,

Bush and Stout (1966). They reported that the voluntary

feed consumption by nonlactating dairy cows was not signifi-

cantly different for rations containing no non-protein

nitrogen supplement, 1.5% of a mixture of MAP and DAP plus

urea (M DAP + U), 3% M DAP + U, or 3% DAP. They also

measured the amount of ammonia released from reagent-grade

DAP, feed-grade DAP, and the M DAP + U upon contact with

bovine saliva for 1 minute with the relative amounts re-

leased being 333, 126 and 16 ug/gm, respectively. With

respect to each of the materials, there was a definite trend

toward increased ammonia release as the pH of the saliva

increased.


Inorganic Phosphate Supplements for Ruminants


Phosphorus has long been recognized as an important

mineral constituent of living organisms. It is found in

every cell of the body with about 80% of the total phosphorus

combined with calcium in bones and teeth. Its roles in bone

mineralization, buffering systems and intermediary metabo-

lism have prompted extensive research with phosphorus in

recent decades. Iluch of this research resulted in part from

its inadequacy under many feeding conditions and its cost

when it must be added as a supplement.









The re are several inorganic phosphat-s which are

i' enG ally 'icd as suppla.emental p'osphors sources AorJ

si.ants. The ava.ahiabl1ity of these various fos Is has

iaenf the basis of consider rable research. Early. wor' con-

ducted by Knox and Neale (1937) revealed no differences in

growth or reproducti, n of three groups of thirty grade

Hereford heifers each receiving either bone meal, mono-

calcium or dicalcium phosphate until they were 4-year-old

cows. Beckeor et al. (1944) reported satisfactory results

with either defluorinated superphosphate or bone meal as

a phosphorus supplement for cattle. They indicated that

the superphosphate had to be provided in a salt mixture to

insure adequate consumption.

Amri.erman et al. (1957), by working with steers and

using phosphorus balance and inorganic bloAod-phosphorus

levels as criteria, demonstrated that two commercial di-

calcium phsphates, two calcined def.1uorinated phosphates,

anId one sample each of bone meal, soft phosphate, and

Curacao Island phosphate were of equal ;value in promoting

phosphorus retention and maintaining b].ood phosphorus

levels. The same authors, using lazwbs, found that di-

calcium -hosphate and Curacao IslanM phosphate were well

utili but soft phosopate anr)d -. calcined defluorinated

phosphate were poorly u5 ilized. Similar results were

reported by Arrington etaa]. (1962) when dicalc.iumin phosphate,

Curacao Island phosphate and defluorinated phosphate were

compared in a depletion-repletion type balance study with









dairy calves. Wise, Wentworth and Smith (1961), by working

with growing calves, and using feed intake, weight gain and

bone concentration of phosphorus as test criteria, found

the phosphorus in defluorinated rock phosphate, Curacao

Island phosphate and dicalcium phosphate to be similar in

availabilities, with soft phosphate being the least

satisfactory supplement used.

Long et al. (1957) conducted two feeding trials with

steers to compare the effects of different levels of mono-

sodium phosphate, which is known to be a highly available

source of phosphorus, upon certain criteria used as measures

of phosphorus nutrition, and to evaluate the relative

phosphorus availabilities of steamed bone meal, Curacao

Island phosphate and dicalcium phosphate. By using feed

intake, weight gain and plasma phosphorus as measures of

phosphorus nutrition, these authors reported that no

statistically significant differences were found among the

different sources of phosphorus, indicating equal avail-

ability of phosphorus in the three sources. Lofgreen (1960),

by working with mature wethers and the isotope dilution

method, found the true digestibilities of phosphorus in

dicalcium phosphate, bone meal, soft phosphate and calcium

phytate to be 50, 46, 12 and 33%, respectively.

Phosphoric acid as a source of supplemental phos-

phorus has also bc-en studied. Richardson et al. (1957)

indicated that the phosphorus of phosphoric acid was as

effective as that of steamed bone meal when the criteria









were weight gaims and plasma phosphorus levels of heifers

maintained on range. Tillman and Brethour (1958a), by

working with young steers and using phosphorus balance and

digestibility data as criteria, reported the availability

of phosphorus supplied by phosphoric acid to be in the same

order of magnitude as that supplied by dicalcium phosphate.

The formation of meta- and pyrophosphates during the

production of defluorinated phosphate was a problem during

the early production of this material. Chicco et al. (1965)

compared the utilization of inorganic ortho-, meta-, and

pyrophosphates using lambs and in vitro techniques. Based

on both in vivo and in vitro studies, calcium orthophosphate,

sodium orthophosphate and sodium metaphosphate appeared to

be equally valuable as sources of phosphorus. Sodium pyro-

phosphate was somewhat lower than those mentioned in

apparent absorption value but equal in solubility and

tissue deposition of 32P. Calcium pyrophosphate and calcium

inetaphosphate were rated low and intermediate, respectively,

as sources of available phosphorus.

Tillman and Brethour (1958b) compared the avail-

ability of vitreous sodium metaphosphate, acid sodium pyro-

phosphate and monosodium phosphate for lambs using apparent

digestibilities, net retentions, fecal endogenous excretions

and true digestibilities of phosphorus as criteria. Acid '

sodium pyrophosphate was equally as available as monosodium

phosphate. The data indicate that the phosphorus of

vitreous sodium metaphosphate was absorbed, but was









inefficiently utilized and excreted in the feces. Research

conducted by _-T1r!'-,rv et al. (1957) indicated that the'

phosphorus of gamma calcium pyrophosphate was almost totally

unavailable to sheep while that supplied by vitreous calcium

metaphosphate appeared to be about 50% as available as that

of monocalcium phosphate. The data indicated that the gamma

calcium pyrophosphate was absorbed and increased the plasma

inorganic phosphorus, but it was inefficiently utilized and

subsequently excreted.

Hall, Baxter and Hobbs (1961) used washed suspensions

of rumen microorganisms in a series of studies to determine

the effects of adding various levels of phosphorus in

different chemical forms upon cellulose digestion. Mono-

sodium orthophosphate, vitreous sodium metaphosphate, acid

sodium pyrophosphate and calcium phytate were used. Marked

increases in cellulose digestion occurred when levels of 20

to 100 mg of phosphorus per ml of medium from each source

were added. Phosphorus in all of the chemical forms studied

appeared to be well utilized by rumen bacteria.

Ammerman et al. (1965) compared the utilization of

inorganic monocalcium orthophosphate, feed grade dicalcium

phosphate, defluorinated phosphate and soft phosphate using

absorption studies with calves and in vitro techniques.

Based on in vitro studies, monocalcium phosphate was the

most available, dicalcium phosphate and defluorinated

phosphate were equally available, and soft phosphate was

essentially unavailable to rumen microorganisms. In vivo









results indicated apparent absorption of phosphorus was

simi.]ar Cor (Wai1_'OiraW d ana dial-cJi 1)i(>osphate
being greater than that for soft phosphate

Diamonium phosph':te is a calcium-f-ree source of

phosphorus which also supplies non-protein nitrogen. Its

value as a possible ource of phosphorus was studied by

Oltjen et al. (1963). Extensive metabolism and growth

trials with sheep and cattle were conducted by these

workers in which diammoniumn phosphate was incorporated

into numerous types of rations to examine its value as a

source of nitrogen and phosphorus. In all studies it was

found to be a satisfactory source of phosphorus.

Kercher and Paules (1967) working with steers,

found no differences Letween dicalcium phosphate, anmnonium

polyphosphate, sodium tripolyphosphate and diammonium

phosphate as sources of supplemental phosphorus for steer

finishing rations. Similar results were reported by Hillis

(1963) when no difference was found between diammonium

phosphate and monosodium phosphate as a source of supple-

mental phosphorus for finishing steers and fattening lambs.


Effect of Age on Magnesium Utilization


The development of hypomagnesaemia in calves to the

stage at which tetanic convulsions occur has beein shown

experimentally by Blaxter, Rook and MacDonald (1954) to be

a comparatively slow process. In contrast, hypomagnesaemic

tetany can develop in the dairy cow and lact.-ting ewe with









great rapidity (Rook and Balch, 1958; L'Estrange and Axford,

1963). Wilson (196.0) suggested that the increased speed of

development of the condition in mature animals may be partly

due to its inability to mobilize reserves of magnesium from

bone as readily as the young animal.

At critically low levels of magnesium intake the

serum magnesium concentration in a mature lactating cow can

be rapidly affected by small changes in intake (Rook, 1961).

Rook and Storry (1962) stated that in an adult sheep only

about 2% of its bone magnesium is available to satisfy

physiological needs. In calves maintained on magnesium-

deficient diets, Blaxter and Rook (1954) found bone magnesium

values of 30% or more below normal but found no measurable

decrease in the magnesium concentration in soft tissues.

Further support for the concept that skeletal

magnesium in younger animals is mobilized more efficiently

than in mature animals is provided by the work of Chicco

(1966). Three age levels of sheep (lambs, yearlings and

2-3-year olds) were fed a magnesium-adequate diet which was

suddenly replaced by a diet deficient in magnesium. In-

appetance appeared more rapidly in the adult animals and

the change in feed consumption was shown to be correlated

with plasma magnesium concentration.

Smith and Field (1963) reported that after 18 days on

a magnesium-deficient diet the mean concentration of

magnesium in the femur and mandible had decreased by 9.5

and 13.4%, respectively, in adult rats and 28.2 and 33.3%









in young rats. Hartindale and Heaton (1964) found adult

rats fed a magnesium deficient diet had a net loss of

magnesium from the femur of 17%. They concluded that the

skeleton acts as a magnesium reserve but the fraction

mobilized in adult rats during magnesium deficiency is

smaller than in weanling rats.

Smith (1959b)and Thomas (1959) demonstrated that the

percent of bone magnesium in milk-fed calves decreased with

age. But it is questionable whether the total reduction of

bone magnesium concentration is due to mobilization from

the bone or to formation of new bone tissue during a period

when the plasma concentration of magnesium is low. Duckworth

and Godden (1941) considered that, where the rate of bone

growth was maintained, most of the decrease in bone magnesium

concentration was attributable to deposition of magnesium-

poor bone rather than to net reabsorption of magnesium.

The apparently greater degree of exchange exhibited

by the young animal has been related by Robinson and Watson

(1955) to the smaller size of the mineral crystals, while

Forbes (1959) attributed it to the greater water content of

the young bone, which might make magnesium more accessible

to circulating body fluids.

The effect of age on magnesium utilization was ex-

amined recently by Garces and Evans (1971) with steers

ranging in age from 10 to 88 months. They reported

magnesium absorption and retention were significantly

correlated with magnesium intake and magnesium utilization

was similar for all ages.









h ,e. nc r eas sn sceptibi .ity t o grass te ta -nv with

aye has of-L. .. .. ait-ibut-ed o an appirW.ri- reduction in

t r e a d ily a i.1a b] e ....... ., ...... r VG-s of na9ne i u Field (1967),

by working n.ih tvwo age groups of ;hp whi ch were 2-and 7-

years old, respectively, reported a significantly iower dry

matter intake by the older group. These results suggest

that a reduction with age of the intake of magnesium by

grazing animals may be an additional factor contributing

to the higher frequency of grass tetany in aged animals.


Magne sium Requirement and Availability


Present estimates indicate about 70% of the total

magnesium of the body is present in the skeleton and the

normal calcium:magnesium ratio in bones is about 55:1. The

magnesium content of bone, muscle and nervous tissue is

estimated to be 2 g, 190 mg and 100 mg magnesium/kg fresh

weight, respectively (Agricultural Research Council, 1965).

The normal level of magnesium in the blood plasma is given

as 1.8 mg/100 ml and above,with an upper limit of 3.8 mrg/100

ml (Rook and Storry, 1962).

The assessment of dietary requirements of magnesium

for maintenance is complicated by the difficulty of esti-

mating the endogenous losses of magnesium from the body.

Many -esearchers have endeavored to estimate these losses

by measuring magnesium balance on varying intakes. Walser

(1967) states that the basic premises of such a.n approach

are first, that the organism will have the wisdom to reject









any magnesium beyond its needs, and second, that negative

balance indicates that intake is less than the requirement.

However, there is a distinct possibility that no homeostatic

mechanism exists in the organism with the primary responsi-

bility of regulating magnesium metabolism. An excessive

intake might therefore result in continued positive balance

until toxic manifestations ensue. Furthermore, the intake

of magnesium is so small in relation to the amount in the

body that, if excretion were always proportional to the

body content, the establishment of a new steady state

following a change in intake would require many months. He

further states that negative balance persisting for many

weeks following a reduction in intake cannot be accepted as

evidence that intake is too low; the preceding intake may

have been too high.

Magnesium is lost from the body by three main routes--

in the milk, feces and urine. A mean value of 126 mg

magnesium/kg has been given'as representative for milk

(Agricultural Research Council, 1965). Rook and Storry

(1962) report a range of published values from 70 to 180

mg/kg, and indicate that no significant fall in the magnesium

content of milk occurs when intake of feed or of magnesium is

reduced.

Fecal magnesium consists of the unabsorbed portion of

the intake and the endogenous magnesium which enters the

alimentary tract in the-saliva and other digestive secretions.

Simesen et al. (1962) measured the endogenous excretion of









miagnesium- in :milk-fed cil
cervals usi inraenos i e:;.o o; ._:c. ."Can vaU s

of 3.5 mg ad 1.5 -'jb/kg "ody weight p- da' were found or

calves and coA:s, repcti.ely. A Lracecr study conducted

by MacDonald and Care (1959) utilizing a 20-month-old

wether resulted in au, estimate of 5 mg/kg body weight per

day for endogenous fecal magnesium. Field (1959) reported

a value of 205 mrag per animal per day in sheep by using

tracer techniques.

Estimates of endogenous fecal magnesium have also

resulted from numerous balance studies. Working with calves

Smith (1959a) reported a value of 0.5 mg and 1.2 mg/kg body

weight per day for calves 2--to 5-weeks old and 3-months old,

respectively. Other values reported are 2 to 4 img/kg body

weight per (day in calves (Blaxter and Rook, 1954) and 3 to

5 mg/kg body weight per day in cows (Blaxter and McGill,

1956). Working with 6-month-old lambs Chicco (1966) cal-

culated a value of 2.33 mg/kg body weight per day by

extrapolation from the regression of fecal magnesium ex-

cretion on imagnesium intake.

Urinary excretion of magnesium may be reduced to

minimal levels following a decrease in the plasma magnesium

concentration. Wilson (1960) suggested that magnesium

behaves as a threshold sub'-tance appearing in th] urine only

when the magnesium load filtered by the glomeruli exceeds

that reabsorbed by the tubules, Numerous threshold values

for blood plasma have been estimated. Storr"; and Rook (1963)










reported threshold values in two cows of 1.5 and 1.8 mg/100

ml of plasma, respectively. Similar values of 1.37 and 1.90

mg/100 ml of plasma were obtained in two lactating ewes by

L'Estrange and Axford (1964) by progressively decreasing

their magnesium intake 40 mg per day. More recently Chicco

(1966), by conducting balance studies with lambs receiving

varying levels of dietary magnesium, calculated renal

threshold values of between 1.5 mg and 1.6 mg/100 ml of

plasma.

Much of the variation in the reported values in the

literature of endogenous fecal and urinary magnesium is due

partly to the inadequate analytical methods in the past for

the quantitative determination of magnesium in biological

materials. However, with the recent advent of such analytical

methods as atomic absorption spectrophotometry and flame

emission spectrophotometry large analytical errors should

now be rare.

Although the magnesium requirement of ruminants under

various production conditions are still uncertain, there are

estimates reported in the literature. Blaxter and McGill

(1956) calculated the requirement of an adult cow for

maintenance to be about 1.8 gm of magnesium per day, and for

production 0.5 to 0.6 gm per 10 lb milk secreted. Assuming

an average availability of-dietary magnesium of 33%, this

indicated a minimum daily requirement of 9 to 11 gm for cows

producing 20-30 lb milk daily.









Duncan, Huffman and Robinson (1S35) estimated 30 to

40 -/kg b.dy It. I-)p r 727 =C c" `-5a r co Ji tc in '-3 n,:) l

pl.a{ma raaginsium conaicentlration of milk-fed calves Then given

various lvels of magnesium salts. A similar valun- of 40

ri../kg body weight was reported for growing calves receiving

magnesium salts (Blaxter and Rook, 1954). When the source of

dietary magnesium was natural feedingstuffs, however, an

intake of 1-2 to 15 mg/kg body weight was sufficient (Huffman

et al., 1941). Thomas (1959) revie-wed the available

literature and reported a range of from 13 to 46 mg maCgnesium

per kg body weight as being the daily magnesium requirement

of calves for maintenance of normal serum or bone magnesium

concentrations. Chicco (1966), by feeding various levels of

inmagnesium in the oxide form to 6-month-old lambs, calculated

a minimum daily requirement of 4 mg/kg body weight to replace

the estimated endogenous magnesium losses from the body. A

dietary level of 8 to 10 ir.g/kg body weight was required,

however, to prevent inappetance in yearling sheep (Chicco,

1966).

In estimating the dietary magnesium requirement of an

animal consideration must be given to the availability of

the dietary magnesium to the animal. It has been shown that

availability varies considerably and may be very low in some

types of feeds. Field, 4cCollum and Butler (1958) found the

efficiency with which two sheep could utilize the magnesium

present in an herbage was 13 and 26%, respectively. Using

tracer techniques, McDonald and Care (1959) a-ad Field (1959)









found the availability of magnesium in hay for sheep was

26.3 and 25.8%, respectively. The Agricultural Research

Council (1965) reported estimates of availability of

dietary magnesiurL for cattle of different ages to be 70% up

to 5 weeks, 40% from 5 weeks to 5 months and 20% over 5

months of age.

The absorptive efficiency of magnesium has also been

shown to be affected by the magnesium status of the animal.

McAleese, Bell and Forbes (1961) found control lambs had

apparent absorption values of 28Mg as the chloride of 40 to

50% whereas magnesium deficient lambs had values of 70 to 75%.

Magnesium deficient lambs were considered those with serum

magnesium values of about 1 mg/100 ml of serum whereas the

controls had serum magnesium concentrations of 2 to 2.5 mg/100

ml.

The nutritional relationship between calcium, phosphorus

and magnesium in animals has been the object of numerous

scientific studies with the'exact role each of these ions

plays in the metabolism of the other two ions still remaining

uncertain. Most of the research on their interactions has

been conducted with laboratory animals. However, there is

no reason to suppose that the absorption of minerals from

the ruminant's intestine should differ basically from that

of the non-ruminants. Smith (1969) states that special

factors peculiar to ruminants are most likely to be found in

the nature of their diet and the modifying effects of the

alimentary tract before the abomasum on that diet.









Recent work (Clark and Belanger, 1967) with adult

rats receiving adequate dietary levels of calcium and

phosphorus and increasing levels of magnesium resulted in

increasing absorption, balance and retention of calcium,

phosphorus and magnesium with the increasing magnesium in-

take. Urinary and skeletal content of calcium and magnesium

also increased whereas their content of phosphorus decreased.

A similar study (Clark, 1968) with adult rats resulted in an

increased absorption of calcium with increasing levels of

dietary magnesium only when the diet was adequate in calcium

content. Urinary calcium was increased, however, irrespective

of the dietary level of calcium. The increasing levels of

dietary magnesium resulted in increased absorption of phos-

phorus only when the dietary phosphorus was adequate and the

calcium to phosphorus ratio low. Urinary phosphorus was

decreased with increasing magnesium intake. Forbes (1963) and

Toothill (1963) both reported decreased absorption and serum

concentration of magnesium in rats fed high levels of calcium

in the diet. An excessive intake of phosphorus has been

shown to depress serum magnesium in the guinea pig and rat

(O'Dell, Morris and Regan, 1960) and the dog (Bunce,

Chiemchaisri and Phillips, 1962).

The interrelationship of calcium, phosphorus and

magnesium in rumii..ants has been examined to a limited extent.

A series of such studies was conducted by Chicco (1966) with

wether lambs. Increasing levels of dietary calcium resulted

in decreased utilization of dietary magnesium when the










criteria considered were fecal excretion, bone and serum

manesi. Converse] there .c round to be decreased

ca lcium util i z .-Lion ;i th i cairt a.ng diLJ'L.y levels of

magnesium when the criteria considered vere fecal excretion

and plasma calcium. Bone calcium was not affected by dietary

level cf magnesium. An increase in calcium intake augmented

the urinary loss of magnesium when the lowest level of

dietary magnesium was fed, whereas supplemental magnesium

lowered the urinary excretion of calcium regardless of the

dietary calcium level. Dietary phosphorus appeared to have

little effect on magnesium utilization. The '"ecal excretion

of magnesium was slightly increased by supplemental phosphorus,

while bone and serum magnesium were not altered. Hjerpe (1968)

conducted a balance study with adult wethers receiving a

semi-purified diet (by placing in the rumen via a ruminal

fistula) supplemented with 0, 0.98 and 9.82 gm of magnesium

per animal daily. Wethers receiving supplemental magnesium

excreted significantly more urinary calcium and significantly

less urinary phosphorus than the non-supplemented controls.

The apparent absorption of calcium was slightly decreased by

supplemental magnesium whereas apparent absorption of phos-

phorus was significantly reduced. Wethers receiving either

0.15 or 0.26% dietary magnesium (Dutton and Fontenot, 1967)

wera found to not differ in calcium balance or serum

magnesium concentration. Serum phosphorus levels were found

to be less in the wethers fed the low level of magnesium.









J isae, Ordcoveza and BarrickI (1963) reported a

significant redct.n in sr-um ',,sium of calves by in-

creasing the dietary phosphorus in the presence of low

dietary calcium. The lowest magnesium level occurred at a

-alcium to -!.osphorus ratio of 0.4:1 and the highest with

the 14.3:1 ratio. Extensive statistical analyses were

conducted by Lomba et al. (1.968) on data collected from

balance studies conduIted with 55 different rations fed to

162 dry and lactating cows. 1Magnesium absorption was found

to be enhanced by increasing magnesium and calcium intakes.

Ilea] effluent samples from milk-fed, stall-r-ed and

grazing calves had ranges of 34 to 74% of the magnesium and

63 to 93% of the calcium existing in a bound form as

measured by it being non-ultrafilterable (Smith and McAllan,

1966). The binding was due to at least two processes; one

appeared due to the presence of binding material which

appeared to be characteristic of ruminating calves ir-

respective of diet consumed. This led the authors to conclude

that it may have been of microbial origin. The other binding

process was believed to be phosphate-dependent. it was later

shown by the same authors (Smith and McAllan, 1967), by

working with simple inorganic solutions and in vitro tech-

niques, that precipitation of magnesium with phosphate can

occur with high concentrations of phosphate in the presence

of minimal concentrations of both calcium and ammonia. This

precipitation was specifically pH--dependent occurring only at

pH of 6.5 and above, which h is a characteristic pH11 of the

distal ileium.









The effect-s of numerous other dietary factors on the

availability of magnesium have been studied. The sudden

increase in potassium intake which occurs when ruminants

first graze spring grass has been considered as a possible

contributing factor to the development of hypomagnesaemic

tetany. Suttle and Field (1967) found that apparent avail-

ability of magnesium to wethers was markedly reduced when

the potassium of a hay and concentrate diet was raised to a

level found in pastures where tetany had occurred. A

similar study was conducted by the same authors (Suttle and

Field, 1969) in which ewes fed a diet containing 0.05%

magnesium and 4.44% potassium exhibited hypomagnesaemic

tetany. This level of potassium had a depressing effect on

the concentration of serum magnesium by reducing its

apparent absorption and as well by possibly exerting a

direct depressing effect on the circulating level of

magnesium. High potassium intake in association with high

intake levels of trans-aconitic acid, which has been found

high in certain spring forages, resulted in experimentally

induced grass tetany in cattle and the tetany did not occur

if either potassium or the acid were received separately

(Bohman et al., 1969). Lomba et al. (1968) reported no

significant correlation, however, between the potassium in-

take, digestibility or utilization, and the fate of dietary

magnesium in numerous balance studies conducted with dry and

lactating cows. These authors did report a highly significant

correlation between fecal magnesium and nitrogen intake with






27


constant magnesium intake. Spring pastures are routinely

high in nitrogen content which has long been considered

as a contributing factor to the high incidence of hypo-

magnesaemic tetany in grazing animals during the spring.

The binding of magnesium in the ileal effluent samples

studied by Smith and McAllan (1966) was increased with

increasing concentrations of ammonia when the samples had

pH values of 6.5 and above.
















CHAPTER IiI


EFFECT OF LEVELS AND SOURCES OF SUPPLEI-'Y, i'.\'L NITROGEN
ON VOt'.'I. ".L' FEED :'.TAKE, AVERAGE DAILY GAIN
AND BLOOD UREA-N IN STEERS


The use of non-protein nitrogen in ruminant t-ations

increases eve-y year with urea continuing to be the major

source. 7> cn though feed formulations have now been dIevised

with which urea may .1- used safely in relatively high pro-

portions, researchers continue to look for other scur:ces of

non-protein nitrogen which may be less toxic and more

economical than urea.

One such source of non -protein nitrogen which may be

economically competitive with urea is diammonium phosphate

(DAP). Interest in DAP was stimulated by its property of

being a source of both non-protein nitrogen ana supplementary

p1osphorus. However, problems of voluntary consumption have

been repor-ted when DAP is used (Hale et al., 1962; Oltjen

et al., 1963; Schaedt et a 1., 1966; Hillis, 1968). Another

dual purpose compound which has recently received attention

is monoammonium phosphate (MAP). MAP contains approximately

12' N and 24% P whereas ;AP co:-ains approximately 18% N and

21% P. The possibility of .NMAP being xorue alatable than DAP

has been suggested.









The follow ing four experii;.->n' we.re conducted to

c.pare t'e e of ure1a, cAP and o lo'/els or A en

fcd co. s.,i n and blood Area- in s eers


Procedure nd Results


Rxeerimc t _1---iEffect of Suppliemental Nitrogen as Soybean
S -1 iT 1 t -* 1i -, -. ii



Eiglit steers, four llerefords and four Angus--Hereford

crossbreds, were randomly assigned according to breed to

four pens of two steers each. Average initial weights of

the four outcome groups in kg were 461, 455, 470 and 440.

The experimental design was a 4 x 4 Latin square balanced

for carry-over effects.

The diets used in this study are chon i.n Table 1.

All diets were calculated to contain the same level of

supplemental calcium (0.37%) and no attempt was made to

equalize supplemental phosphorus. The diets contained

11.8% crude protein. All steers received the basal diet

(diet A) for 8 days at the beginning of each of the four

periods to prevent a carry-over effect of treatment.

Diets i;.i.re fed once daily in amounts to give about a 10%

weigh back. Experimental diets were fed for 8 days at the

end of eachIL period with individual steer weights taken at

the beginning and end of the 8-day e-perimental feeding

period.
The data were analyzed statistically by analysis of

variance and significant differences between means were















TABLE 1. COMPOSITION OF DIETS


__ _--Diet sI __
DAP
Soybean +
Meal DAP Urea Urea
Ingredient (A) (B) (C) (D)
Snapped corn, ground 69.9 72.75 78.13 77.68

Cottonseed hulls 10.0 10.0 10.0 10.0

Alfalfa meal (17%
protein) 3.0 3.0 3.0 3.0

Sugarcane molasses 5.0 5.0 5.0 5.0

Soybean meal (50%
protein) 10.0 -6.19 0.27 0.36

Salt, trace-mineralized2 0.6 0.6 0.6 0.6

Calcium phosphate;
17.5% Ca, 23% P 1.0 1.0 -

Diammonium phosphate 1.5 1.5

Urea 281 1.5 0.9

Ground limestone 0.5 0.96 0.5 0.96

Vitamins A & D3 + + + +

100.00 100.00 100.00 100.00

Diet A provided all supplemental protein as soybean meal;
diet B provided 0.269% non-protein nitrogen (NPN) as DAP;
diet C provided 0.674% NPN as urea; diet D provided 0.269%
NPN as DAP and 0.405% NPN as urea (0.674% total NPN).
2
Listed mini'Tnum analysis in percent: Fe, 0.30; Mn, 0.20;
Cu, 0.08; Co, 0.01; Zn, 1.00; I, 0.01; and NaCi, 95.0.

3Vitamins added per kg of diet: 2,200 IU vitamin A
palmitate and 440 IU vitamin D2.









determined using Duncan's New Multiple Range Test (Steel

and Torrie, 1960).

The average daily feed conSui.i:.tion and average daily

gain of steers on the four treatments are shown according

to treatment in Table 2. The individual data are presented

in Appendix Table 26. Diet C (1.5% urea) was similar to

diet A (soybean meal) in acceptability as measured by

average daily feed intake (13.97 and 14.38 kg, respectively).

The consumption of both diets, however, was significantly

greater (P <.05) than the average daily feed intakes of

12.02 and 12.52 kg for diets B (1.5% DAP) and D (1.5% DAP

plus 0.9% urea), respectively. There were no significant

differences in average daily gain among treatments. The

large variability that was observed within treatments in

average daily gain makes the usefulness of this measurement

questionable in such short-term feeding periods.


Experiment 2--Effect of Supplemental Nitrogen as Soybean
Meal, DAP and Two Levels of NAP on Voluntary Feed Intake,
Average Daily Gain and Blood Urea-N in Steers


Eight steers of British breeding were randomly

assigned to four pens of two steers each. The c.-:primental

design was a 4 x 4 Latin square balanced for carry-over

effects. Two steers were removed from the experCiment during

the preliminary period due to digestive coriplications which

resulted in two pens having only one steer each. The

average initial weight of the six steers used was 312 kg.
















TABLE 2. EFFECT OF SOURCE OF NITROGEN ON FEED
CC:,SULMiPTION AND AVERAGE WEIGHT GAIN


Treatment
DAP


Soybean
Meal


DAP


Urea


+
Urea


Item ____(A) (B) (C) (D)

Daily feed intake, kg 14.38 a 12.02b 13.97a 12.52b

Daily gain, kg 0.96 0.96 0.16 0.34

ab Means in the same line bearing different superscript are
significantly (P < .05) different.









The diets used in this study are shown in Table 3.

All diets were calculated to contain 0.56% supplemental

calcium and phosphorus. The diets contained 11.8% crude

protein. All steers received the basal diet (diet A) for

8 days at the beginning of each of the four periods to

prevent a carry-over effect of treatment. The experimental

diets were fed for 8 days at the end of each period. The

diets were fed once daily in amounts to give about a 10%

weigh back with individual steer weights taken at the

beginning and end of the 8-day experimental feeding periods.

At the conclusion of each period the steers were fasted for

12 hours and then allowed to consume ad libitum their re-

spective treatment diets for a period of 2 hours. Blood

samples were taken by jugular puncture before feeding and

again at the end of the 2-hour period for determination of

blood urea-N. The amount of feed consumed by each steer

during this 2-hour period was also recorded.

Blood urea-N was determined by the method of Ormsby

(1942) with refinements suggested by Richter and Lapoinie

(1962). The data were analyzed statistically by analysis

of variance and significant differences between means were

determined using Duncan's New Multiple Range Test (Steel

and Torrie, 1960).

The average daily feed consumption and average daily

gain of steers on the four treatments as well as the blood

urea-N data are summarized in Table 4. The individual data

are presented in Appendix Table 27.















TABLE 3. COMPOSITION OF DIETS


Ingredient
Snapped corn, ground

Cottonseed hulls

Alfalfa meal (17%
protein)

Sugarcane molasses

Soybean meal (50%
protein)
2
Salt, trace-mineralized

Monosodium phosphate

Monoammonium phosphate

Diarmonium phosphate

Ground limestone

Vitamins A & D


Soybean
Meal
(A)
67.34

10.00


3.00

5.00


10.39

0.60

2.21





1.46

+

100.00


Diets1
1.50% 0.75%
DAP MAP
(B) (C)
71.04 68.59

10.00 10.00


3.00

5.00


6.45

0.60

0.95



1.50

1.46

+

100.00


3.00

5.00


9.10

0.60

1.50

0.75



1.46

+

100.00


'Diet A provided all supplemental protein as soybean meal;
diet B provided 0.269% non-protein nitrogen (NPN) as
dianmonium phosphate (DAP); diet C provided 0.088% NPN as
monoamfonium phosphate (MAP); diet D provided 0.269% NPN
as MAP.

2Listed minimum analysis in percent: Mn, 0.23; I, 0.007;
Fe, 0.425; Cu, 0.03; Co, 0.01; S, 0.05; Zn, 0.008; and
NaCl, 97.5.

3Vitamins added per kg o.f diet: 2,200 IU vitamin A
palmitate and 440 IU vitamin D2.


2.30%
MAP
(D)
71.21

10.00


3.00

5.00


6.43

0.60



2.30



1.46



100.00















TABLE 4. E0F1CT 0' SOURCE OF NITROGEN ON F' 0'
CC' :,- P`ION, AVERAGE WEIGCHT (.i AND
BLOOL UiAEA-N (B([1")


Treatment
Soybean 1.50% 0.75% 2.30%
Meal DAP MAP I-AP
Item (A) (B) (C) (D)


Daily feed intake, kg

Daily gain, kg


14. 49a

1.79a


Feed intake, 2 hours (kg) 4.02

Initial BUNd 17.00

BUN change, 2 hours 0.36


13.99a 13.55b 12.441('


2.98)

3.65

14.93


1.69a ].33a


4.06


3.96


-5.46 15.96


0.77ab 2.32c 1.17b


BUN change/kg feed
consumed


0.12a


0.20a


0.58b 0.29a


a'bCMeans on the same lines bearing different superscript
are significantly (P< .05) different.
dBUN concentration expressed as mg per 100 ml of whole
blood.









Diet 13 1.5'% DAP) was similar to di3t A (soybean meal)

.n = a r.;r 1red bay ...- d- feeId :itake

(13.99 and 11.49 k, res,..ctively). The aver-age daily feed

intake of 13.55 kg for diet C (0.75% MAP) was significantly

less (P < .05) than diet A. Diet D, which contained 2.3%

It, resulted in an average daily feed intake of 12.44 kg

which was significantly less (P< .05) than all other treat-

ment diets. Average daily gain during the 8-day experimental

periods was significantly greater (P <.05) for treatment

B (1.50% DAP). Here again the large variability that was

observed within treatments makes the usefulness of average

daily gain questionable in such short-term feeding periods.

The 12-hour fast at the end of each period followed

by ad libitum consumption for 2 hours of their respective

treatment diets resulted in similar feed intakes. The blood

urea-N concentrations just prior to the 2-hour feeding

period were likewise similar. The resulting changes in

blood urea-N concentrations following the 2-hour period

were similar for diets A (soybean meal) and B (1.5% DAP).

The change resulting with diet D (2.3% MAP), however, was

significantly greater (P< .05) than diet A and the change

with diet C (0.75% MAP) was significantly greater (P< .05)

than with all other treatment diets. When the change in

blood urea-N concentration was expressed per kg of reed

consumed during the 2-hour period treatment C was signifi-

cantly greater (P < .05) than all other treatments.









x,,.) e r itrnt 11:ipY-iCCe-. '-'- Nitroqen as Soybean
? : ' ; ^ . 7 .. .:*. .... . .. . V o ..... . . . .. ..'
.' ........ -a, G., n 3l (].Ocd T'ci'. -i' a in Si ;(.er-s

or te present e er- a 4 x 4 Latin sure
a 4~ x 4- Lat~ Si
design was ag-ain utilizeu. Foui-r H[ereford steers, having an

initial average weight of 336 kg, were fed the dints shown

in Table 5. The diets used in this experiment were to be

replicates of those used in Experiment 2. However, it was

not possible to obtain ground snapped corn at the time of

this experiment and corn meal alonq with an increased level

of cottonseed hulls were substituted in its place. All

other ingredients were the same. This experiment was con-

ducted and analyzed the same as described for Experiment 2.

The average daily feed consumption and average daily

gain of steers on the four treatments as well as the blood

urea-N data are summarized in Table 6. The individual data

are presented in Appendix Table 28. Treatment A (soybean

meal), C (0.75% MAP) and D (2.3% ".i?) did not differ in

acceptability as measured by average daily feed intake.

Treatment B, which contained 1.5% diammonium phosphate, was

consumed significantly less (P <.05) than any other treat-

ment. There were no significant differences in average

daily gain among treatments. The 12-hour fast of the steers

at the end of each period folo,,owed by ad libitum consumption

for 2 hours of their respective t-reatment diets resulted in

no differences in feed intake between treatments A, C and D.

Treatment B]3, which contained 1.5` diamir.onium phosphate, was

consumed significantly less (P < .05) than treatments C and D















TABLE 5. COMPOSITION OF DIETS


Diets1_____
Soybean 1.50% 0.75% 2.30%
Meal DAP MAP MAP
Ingredient (A) (B) (C) (D)
Corn meal 51.81 55.57 53.09 55.76

Cottonseed hulls 25.00 25.00 25.00 25.00

Alfalfa meal (17%
protein) 3.00 3.00 3.00 3.00

Sugarcane molasses 5.00 5.00 5.00 5.00

Soybean meal (50%
protein) 10.92 6.92 9.60 6.88

Salt, trace-mineralized2 0.60 0.60 0.60 0.60

ionosodiumr phosphate 2.21 0.95 1.50 -

Monoammonium phosphate 0.75 2.30

Diainmnonium phosphate 1.50 -

Calcium carbonate 1.46 1.46 1.46 1.46

Vitamins A & D3 + + + +

100.00 100.00 100.00 100.00


1Diet A provided all supplemental


protein as soybean meal;


diet B provided 0.269% non-protein nitrogen (NPN) as
diammonium phosphate (DAP); diet C provided 0.088% NPN as
monoaiamonium phosphate (MAP); diet D provided 0.269% NPN
as MAP.

2Listed minimum analysis in percent: Mn, 0.23; I, 0.007;
Fe, 0.425; Cu, 0.03; Co, 0.01; S, 0.05; Zn, 0.008; and
NaCl, 97.5

3Vitamins added per kg of diet: 2,200 IU vitamin A
palmitate and 440 IU vitamin D2.















TABLE 6. EFFECT OF SOURCE OF NITROGEN ON FEED
CCQISii'PTION, AV:.,0.GF WEIGHT GAIN AND
BLOOD UREA-N (BUN)


Item
Daily feed intake, kg

Daily gain, kg

Feed intake, 2 hours

Initial BUNc

BUN change, 2 hours

BUN change/kg feed
consumedc


Soybean
Meal
(A)
8.43a

1.36

2.96ab

13.31

0.09ab


Treatment
1.50% 0.75%
DAP MAP
(B) (C)
7.01b 8.71a

0.57 0.37

2.20b 3.58a

11.56 12.81

1.25a 0.06b


0.61b 0.00a


abMeans on the same lines bearing different superscript are
significantly (P <.05) different.
CBUN concentration expressed as mg per 100 ml of whole
blood.


2.30%
MAP
(D)
8.39a

0.37

3.47a

12.21

1.25a


0.35ab









during this 2-hour. period. The blood li.ea-N concent-ation
D:riCor to :he 2- -"our feeding period .as --:i]ar Ior. all

treat-n-s a.nd 4' he resulting chanuFce in blood urea--N con-

centration ,,ast1 found :-o be similar for treatments A, B and

D. Treatment C, which contained 0.75% IMAP, actually showed

an average decrease in BUN concentration, and this was

significantly less (P <.05) than treatments B and D. When

the change in BUN concentration was expressed per kg of

feed consumed during the 2-hour period treatments A, C and

D were similar. Treatment B, which contained 1..5% DAP,

resulted in a significantly greater change (P < .05) than

treatments A and C, which contained supplemental soybean

meal and the lowest level of MAP, respectively.


Experiment 4--Effect of Supplerremental Nitroqen as Soybean

A \ : r ._? > n '-i l.; i ..- .: i U '.-,- '. .,:-.",-:i i-n -c, ", .-s


The four Hereford steers used in Experiment 3 were

again utilized in the present experiment. Following the

previous experiment the steers were fed a corn-soybean meal

based diet for a period of 9 weeks and had an average weight

of 436 kg at the beginning of this experiment. The experi-

mental design was again a 4 x 4 Latin square with the steers

receiving the diets shown in Table 7. Diets used in this

experiment were mixed weekly whereas diets for the previous

experiments were mixed at the beginning of each experiment

in adequate quantities for the entire experimental period.

The frequent mixing more closely approximates actual feedlot















TABLE 7. COMPOSITION OF DIETS


-__ -Diets1_____
Soybean 1.50% 0.75% 2.30%
Meal DAP MAP MAP
Ingredient (A) (B) (C) (D)
Corn meal 54.36 58.12 55.63 58.29

Cottonseed hulls 25.00 25.00 25.00 25.00

Alfalfa meal (17%
protein) 3.00 3.00 3.00 3.00

Corn oil 2.00 2.00 2.00 2.00

Soybean meal (50%
protein) 11.37 7.37 10.06 7.35

Salt, trace-mineralized2 0.60 0.60 0.60 0.60

Monosodium phosphate 2.21 0.95 1.50 -

Monoammonium phosphate 0.75 2.30

Diammonium phosphate 1.50 -

Calcium carbonate 1.46 1.46 1.46 1.46

Vitamins A & D3 + + + +

100.00 100.00 100.00 100.00

IDiet A provided all supplemental protein as soybean meal;
diet B provided 0.269% non-protein nitrogen (NPN) as
diammonium phosphate (DAP); diet C provided 0.088% NPN as
monoammonium phosphate (MAP); diet D provided 0.269% NPN
as MAP.
2.
Listed minimum analysis in percent: Mn, 0.23; I, 0.007;
Fe, 0.425; Cu, 0.03; Co, 0.01; S, 0.05; Zn, 0.008; and
NaCI, 97.5.
Vitamins added per kg of diet: 2,200 IU vitamin A
palmitate and 440 IU vitamin D2.









conditions where fresh feed is often mixed daily. Corn oil

at a level of 2% of the diets was substituted for the 5%

molasses previously used due to the convenience of corn oil

under the mixing conditions available. All other ingredients

were the same. This experiment was conducted and analyzed

the same as described for Experiment 2.

The average daily feed consumption and average daily

gain of steers on the four treatments as well as the blood

urea-N data are summarized in Table 8. The individual data

are presented in Appendix Table 29. There were no signifi-

cant differences in average daily feed intake among treat-

ments. Treatments C and D (0.75 and 2.3% MAP, respectively)

resulted in significantly less (P <.Q5) average daily gain

than treatment A (soybean meal). The 12-hour fast at the

end of each period followed by ad libitum consumption for

2 hours of their respective treatment diets resulted in

similar feed intakes for all diets. The blood urea-N

concentrations prior to the .2-hour feeding period were

similar for all treatments and the resulting changes follow-

ing this 2-hour period were found to be similar for treat-

ments A and C. The change with treatment diet D was

significantly greater (P <.05) than with diets A and C and

treatment B resulted in a change significantly greater

(P <.05) than treatment A. When the change in blood urea-N

concentrations were expressed per kg of feed consumed during

the 2-hour period treatments A and C were significantly

less (P <.05) than treatments B and D.















TABLE 8. EFFECT OF SOURCE OF NITROGEN ON FEED
CONSUMPTION, AVERAGE ';I:TGHT GAIN AND
BLOOD I..i:FA-N (BUN)


____ Treatment
Soybean 1.50% 0.75% 2.30%
Meal DAP MAP MAP
Item (A) (B) (C) (D)
Daily feed intake, kg 8.66 8.93 9.23 8.46

Daily gain, kg 1.60a 0.77ab 0.33b -0.06b

Feed intake, 2 hours 2.44 1.76 2.56 2.56

Initial BUNc 14.28 13.51 15.63 13.54

BUN change, 2 hours 0.31a 1.05bc 0.46ab 1.34c

'UNl change/kg feed
consumed 0.15a 0.60 0.11a 0.58

abMeans on the same lines bearing different superscript are
significantly (P <.05) different.
CBUN concentration expressed as mg per 100 ml of whole
blood.









Discussion


Diammonium phosphate supplementation has been re-

ported to decrease diet acceptability (Hale et al., 1962;

Oltjen et al., 1963; Schaadt et al., 1966; Hillis, 1968).

In Experiments 1 and 3 of this series of studies, diets

containing 1.5% diammonium phosphate (DAP) were consumed

significantly less (P <.05) than diets supplemented with

soybean meal, urea, or monoammonium phosphate (MAP). This

level of DAP, however, did not significantly reduce feed

consumption in Experiments 2 and 4.

Levels of 0.75 and 2.3% MAP in Experiments 2, 3 and

4 did not affect feed consumption except in Experiment 2

when the diet containing 2.3% MAP was consumed signifi-

cantly less (P < .05) than the soybean meal and DAP

supplemented diets. Reaves et al. (1966) found no

appreciable differences in voluntary feed consumption by

nonlactating dairy cows when fed rations supplemented with

a combination of MAP, DAP and urea or DAP alone.

Although average daily gain was highly variable

within treatments and the value of gains recorded on such

short-term periods is questionable, it was found that the

inclusion of MAP into the experimental diets consistently

resulted in a decreased average daily gain.

The amount of feed consumed in a 2-hour period

following a 12-hour fast was consistently greater for diets

containing MAP compared to those containing 1.5% DAP. The

resulting change in blood urea-N was consistently greater









for the treatments containing isonitrogenous levels of non-

protein nitrogen (1.5% DAP and 2.3% MAP) except in Experi-

ment 2 where the 0.75% MAAP treatment resulted in the

greatest change in BUN. The same trends existed when the

blood urea-N changes were expressed per kg of feed

consumed.

A possible contributing factor to the variable

results between experiments is the time of year in which

each experiment was conducted. Experiments 1, 2, 3 and 4

were conducted during the winter, spring, summer and fall,

respectively. Mean rainfall (mm) and mean temperature (C)

for the area during the experimental periods were: (1) 82,

14; (2) 67, 25; (3) 156, 28; (4) 35,.15 (Climatological

Data National Summary, 1969-1971). It is possible that the

large variations in rainfall and temperatures between

experimental periods may have affected the animal perform-

ances and the relative outcomes of the separate experiments.















CHAPTER IV


NITROCE'!J SOURCE AND RiUlIW1 AMMONIA,
pH AND BLOOD UREA-N


A major problem resulting in inefficient utilization

of non-protein nitrogen sources by ruminants is the rapid

release of ammonia. It has been well established that a

limiting factor in the utilization of urea is its rapid

hydrolysis in the rumen. A reduction in the rate of

absorption of the released ammonia would contribute to

the efficiency of its utilization by the rumen microbes.

Phosphate is thought to buffer rumen pH during urea

hydrolysis and therefore minimize ammonia absorption

and ammonia wastage.

The following two experiments were conducted to

compare the relative rates of release and absorption of

ammonia of natural and non-protein nitrogen sources in

fistulated wethers.


Procedure and Results


Experiment 1--Effect of Nitrogen Source on Rumen Ammonia,
pH and Blood Urea-N


Four fistulated mature wethers ranging in weight

from 51.2 to 57.6 kg were utilized in a 4 x 4 Latin square

designed experiment balanced for carry-over effects. The









sheep were housed in metal metabolism cages and fed the hay-

corn based diet shown in Table 9. One kg of this diet was

fed once daily and water was supplied ad libitum.

The treatments used in this study consisted of each

animal receiving intraruminally 10 gm of nitrogen per 45.4

kg body weight from either soybean meal, urea, diammonium

phosphate (DAP) or monoammonium phosphate (MAP). An interval

of 6 days between each of the four treatment periods was

allowed for the sheep to readjust. On treatment mornings,

the nitrogen sources were given in dry form via the fistula

approximately 2 hours following consumption of their corn-
f
hay diet. Rumen fluid and jugular blood samples were taken

immediately before dosing and at periodic intervals there-

after for dletermination of rumen pH, rumen ammonia and

blood urea. The pH of rumen fluid was determined using a

Sargent Model DR pH meter within 1 minute after sampling.

Rumen ammonia-N was determined by the phenol nitroprusside-

alkaline hypochlorite method of Kaplan et al. (1965).

Blood urea-N was determined by the method of Ormsby (1942)

with refinements suggested by Richter and Lapoinie (1962).

The data were analyzed statistically by analysis of variance

and significant differences between means were determined

using Duncan's New Multiple Range Test (Steel and Torrie,

1960).

The effect of the four treatments on rumen pH is

presented in Table 10 and is presented graphically in

Figure 1. The individual data are presented in Appendix






48







TABLE 9. COMPOSITION 0'? DIET



Ingredient %

Bermudagrass hay, ground 70.4

Corn meal 25.0

Corn oil1 3.0

Defluorinated phosphate 1.0

Salt, trace-maineralized2 0.6

Vitamins A and D +

100.0

1Stabilized with ethoxyquin.
2
Listed minimum analysis in percent: Zn, 1.00; Fe, 0.30;
Mn, 0.20; S, 0.10; Cu, 0.08; Co, 0.01; and NaCI, 95.00.

32,200 IU vitamin A palmitate and 440 IU vitamin D2 added
per kg of diet.















TABLE 10. EFFECT OF A SINGLE DOSE OF SOYBEAN NIFAT,,
UREA, DIAMMONIUM PHOSPHATE OR MONO.-'ION I UM
PHOSPHATE ON RUMEN pHa


Hours
After Dosing
0

0.5

1

2

3

4

6

9

12

24


Soybean
Meal
6.82

6.68b

6.66b

6.56bd

6.52b

6.50b

6.42b

6.39bc

6.48bc

6.85b


Urea
6.73

7.20c

7.48c

7.34c

7.22c

7.13c

6.98c

6.71c

6.54c

6.74 b


DAP
6.70

6.94d

6.90d

6.79d

6.64b
6.62b3


6 6 2hb
6.51 b

6.34bc

6.18bd

6.40c


All values are means of four


periods per treatment.


b' cde' Means on the same line bearing different superscripts
are significantly (P <.05) different.


MAP
6.77

6.43e

6.45e

6.42b

6.41b

6.36b

6.12b

6.19b

6.13d

6.34c














7 .50


7 25-[1 g -
S5 ...-. Soybean meal

7.00- --_" DAP
i,. ~MAP



6.50- 1 *".... ."-
--- -- *"^ ^ ......-
.5- -.. ..........

6.0-
a)
6 25-j'

.0 jj I _ _ _ _I


0.5 1 2 3 4 6 9 12 24
Hours after dosing

FIGURE 1. EFFECT OF TREATMENTS ON RUMEN pH









Table 30. No significant differences between treatments

in predosing ruminal pH were observed. The rumen pH for

the urea treatment rose sharply during the first hour to a

value of 7.48 and then gradually declined until the twelfth

hour to a value slightly lower than the predosing value.

The DAP treatment resulted in an initial increase in pH with

a maximum value of 6.94 observed at one-half hour postdosing

followed by a gradual decline to 6.18 at hour twelve. The

MAP treatment resulted in a sharp decrease in pH during the

initial 30 minutes followed by a gradual decline to a low

of 6.12 at 6 hours postdosing. The DAP treatment remained

intermediate to the other two non-protein nitrogen treat-

ments throughout the 24-hour experimental period. The pH

in the rumen of sheep receiving soybean meal fell slightly

as the day progressed.

Statistical analysis of the rumen pH values at the

individual hours revealed a significant (P <.05) difference

between all treatments at one-half and one hour postdosing.

This difference continued between the non-protein nitrogen

treatments through hour two. The urea treatment had

significantly (P <.05) higher values of rumen pH than the

DAP and MAP treatments for all hours observed except the

twelfth.

The effect of treatment on rumen amn.on.a-N is pre-

sented in Table 11 and Figure 2. The individual data are

presented in Appendix Table 31. No significant differences

existed between treatments in predosing rumen ammonia-N















TABLE 11. EFFECT OF A SINGLE DOSE OF SOYBEAN MEAL,
UREA, DIAMMONTUM PHOSPHATE OR MONC.1'D.rIONIUM
PHOSPHATE ON RUMEN AMMONIA-N


Mg/100 M1
Hours Soybean
After Dosing Meal Urea DAP MAP
0 15.5 12.8 15.0 16.0

0.5 18.6b 77.5bc 95.9bc 148.4c

1 24.2b 87.3bc 88.5bc 118.0c

2 26.8b 80.2c 93.7c 107.7c

3 29.7b 74.2c 88.5c 93.5c

4 34.0b 68.2c 85.0c 93.3c

6 29.9b 71.9c 89.9c 78.1C

9 23.7b 55.4c 64.7c 64.8c

12 22.7b 35.7c 55.1d 56.8d

24 20.4b 16.6b 39.8c 42.4c

All values are means of four periods per treatment.

bi'CdMeans on the same line bearing different superscripts
are significantly (P <.05) different.


















175-,-


-150-1


0






o I


50- ..

N

25 ).


0


MAP

DAP

Urea

Soybean meal


-4..-

.-. a * 2


i'^.,. .J ., ,'L L'T; L .:.. J ., ,;'*7 [ L .f ." .. ... .... .'L, ,- . ,t '..."
0.51 2 3 4 6 9 12
Hours after dosing

FIGURE 2. EFFECT OF TREATMENTS ON RUMEN AMMONIA-N


......s .1-.'r....









concentrations. The highest concentration of ammonia-N

(148.4 mg/100 ml) was observed with the MAP treatment at

one-half hour postdosing. The DAP treatment had a peak

concentration of 95.9 mg/ml also at one-half hour post-

dosing but changed very little in concentration through

hour six. The urea treatment had a peak concentration

of 87.3 mg/ml at one hour and exhibited a gradual decline

for the remainder of the experimental period. As

could be expected, the least change in rumen ammonia-N

concentration occurred with the soybean meal treatment.

Statistical analysis of the ammonia-N values at the

individual hours revealed no differences between the MAP

and DAP treatments and they differed significantly (P <.05)

from the urea treatment only at hours twelve and twenty-

four.

The effect of treatment on blood urea-N is presented

in Table 12 and Figure 3. The individual data are presented

in Appendix Table 32. No significant difference existed

between treatments in predosing blood urea-N concentrations.

The urea treatment resulted in the greatest increase in

blood urea-N with all non-protein nitrogen treatments

reaching a peak concentration at nine hours postdosing.

The DAP treatment had a consistently greater concentration

of blood urea-N than the MAP treatment from the third hour

through the remainder of the sampling period. However,

these treatments were not found to be significantly

different. The urea treai-tment had a significantly (P <.05)















TABLE 12. EFFECT OF A SINGLE DOSE OF SOYBEAN MEAL,
UREA, DI .'-kUIO)NIUM PHOSPHATE OR MONOC-JU11,OIUM
PHOSPHATE ON BLOOD UREA-Na


Mg/100 Ml
Hours Soybean
After Dosing Meal Urea DAP MAP
0 16.5 15.0 14.4 15.0

1 17.6b 20.5c 17.3b 17.5b

2 18.0b 22.3c 19.8b 20.4bc

3 19.5b 24.8d 22.5cd 21.9bc

4 20.0b 26.8d 23.7c 23.3c

6 22.0b 31.5d 27.3c 25.0c

9 23.0b 34.8d 30.3c 27.0c

12 23.1 33.0c 27.4b 26.3b

24 27.3 26.8 25.9 26.0
aAll values are means of four periods per treatment.

b'C/dMeans on the same line'bearing different superscripts
are significantly (P <.05) different.























-i /,.. *. -.-

........... DA..P..
-0-
b Urea
-,DAP
MAP
S.-..-. Soybean meal

U1i1 11 1 I I .. ___J
1 2 3 4 6 9 1.2 24
Hours after dosing
FIGURE 3. EFFECT OF TREATMENTS ON BLOOD UREA-N









greater concentration of blood ure..-N than either MAP or

DAP ?or hous four through twelve. N:o ne of the tr-eatnmenhs

differed significantly at hour L;enty-four of the s ampli ng

period.


Experiment 2--Effect of Nitrogen Source and Supplemental
Acid or Base on Rurien .'-' .onia, pH and Blood Urea-N


The four fistulated wethers used in Experiment 1

were utilized again in the present Latin square experiment.

A period of six months was allowed between experiments.

The conditions and basal diet for this experiment were the

same as those described for Experiment 1. The treatments

were urea, urea plus phosphoric acid, monoammonium phosphate

(MAP), and MAP plus sodium carbonate. The amount of

nitrogen supplied by each treatment was again 10 gm per 45.4

kg body weight.

A preliminary study was conducted with two extra

fistulated wethers to determine the amount of phosphoric

acid that, when administered simultaneously with 10 gmi of

nitrogen as urea, would effect a change in rumen pH similar

to that which occurs following 10 gm of nitrogen as MAP.

This amount of MAP supplies 20.4 gm of phosphorus. However,

supplying 20.4 gm of phosphorus as reagent grade phosphoric

acid resulted in a reduction in rumen pH to unphysiological

levels. It was found that supplying 10 gm of phosphorus

as phosphoric acid per 45.4 kg body weight would reduce the

tumen pH similar to the reduction with MAP. Similarly, a

preliminary study indicated that 21 gm of reagent grade









sodium carbonate when administered simultaneously with 10

gm of nitrogen in the form of NAP would affect the rumen

pH similar to that which occurs following 10 gm of nitrogen

as urea. The designated amounts of phosphoric acid and

sodium carbonate were diluted with water to 400 ml for

dosing. The treatments receiving only urea or MAP also

received 400 ml of water per 45.4 kg body weight. The

sampling procedures, chemical and statistical analyses

were the same as those described for Experiment 1.

The effect of the four treatments on rumen pH is

presented in Table 13 and is presented graphically in

Figure 4. The individual data are presented in Appendix

Table 33. No significant differences between treatments

in predosing ruminal pH were observed. The urea and MAP

plus sodium carbonate treatments had pronounced initial

increases in rumen pH. The urea treatment reached a peak

of 7.52 at one hour postdosing and then gradually declined

until the twelfth hour to a value slightly lower than the

predosing value. The MAP plus sodium carbonate treatment

reached a peak of 7.19 at one-half hour postdosing followed

by a fall in pH to 6.78 after only one hour.

The MAP and urea plus phosphoric acid treatments

resulted in initial decreases in pH. The urea plus acid

treatment reached a value of 5.20 at one-half hour followed

by a precipitous rise to a value above the predosing value

by the fourth hour. The YAP treatment exhibited a sharp

decrease during the initial 30 minutes followed by a















TABLE 13. EFFECT OF A SINGLE DOSE OF UREA, UREA PLUS
PHOSPHORIC ACID, '21OrOAMMONIUM PHOSPHATE, OR
MONOAMIMONIUM PHOSPHATE PLUS SODIUM CARBONATE
ON FU-1IEN pHa


Urea MAP
+ +
Hours Phosphoric Sodium
After Dosing Urea Acid MAP Carbonate
0 6.57 6.54 6.43 6.40

0.5 7.06b 5.20c 6.03c 7.19b

1 7.52b 5.83c 5.99c 6.78b

2 7.40 6.25 6.02 6.67

3 7.07b 6.43bc 5.90c 6.69b

4 6.77b 6.62b 5.87c 6.62b

6 6.66b 6.53b 5.87c 6.54b

9 6.56b 6.41b 5.86c 6.38b

12 6.55b 6.11cd 5.76d 6.27bc

24 6.80 6.13c 6.04c 6.31bc
aAll values are means for four periods per treatment.

bcdMeans on the same line bearing different superscripts
are significantly (P <.05) different.

















8 C-
Urea
;." .- ... U r ea
7.5- i -^_............. P Base
SA Bas

S \ ... Urea + Acid
7 :,. \
7 : \ MAP

)46.5
!; \t --- ---- A-",^-AP
-- ^ ; a ^.p. -- '. .-

S/ ......................................................
!, /

C) *
6 0


1 *
5.0"}-
?1

.-. J 1-,- -- -.. - .-- .""-'.-..-. -
0.5 1 2 3 4 6 9 12 24
Hours after dosing

FIGURE 4. EFFECT OF TR-EAT,-.lS ON RUMEN p11









gradual decline to a low of 5.76 at twelve hours postdosing.

The MAP plus base and urea plus acid treatments showed

similar changes in rumen pH from hour four through the

remainder of the sampling period.

Statistical analysis of the rumen pH values at the

individual hours revealed the urea and MAP plus sodium

carbonate treatments to have significantly (P <.05) greater

pH values than the MAP and urea plus phosphoric acid treat-

ments at one-half and one hour postdosing. The MAP plus

base treatment continued significantly (P< .05) different

from the MAP treatment for hours three through twelve.

The urea treatment resulted in a significantly (P < .05)

higher rumen pH than the MAP treatment for all hours post-

dosing except the second. This is similar to the results

reported in Experiment 1 for the urea and MAP treatments.

The effect of treatment on rumen ammonia-N is

presented in Table 14 and Figure 5. The individual data are

presented in Appendix Table '34. No significant differences

existed between treatments in predosing rumen ammonia-N

concentrations. The MAP and MAP plus sodium carbonate

treatments exhibited an almost identical pattern in con-

centration throughout the sampling period. The urea

treatment attained its peak concentration earlier than the

urea plus phosphoiic acid treatment with the latter treat-

ment sustaining a higher concentration throughout the

remainder of the sampling period.















TABLE 14. EFFECT OF A SINGLE DOSE OF UREA, UREA PLUS
PHOSPHORIC ACTD, MONOA'-L'IO..' IU PHOSPHATE, OR
MONOAMMONIUM PHOSPHATE PLUS SODIUM CARBONATE
ON RUPIN AMMONIA-Na


Mg -l


Hours
After Dosing
0

0.5

1

2

3

4

6

9

12

24


Urea
9.7

70.7 b

99.2b

112.7b

87.7b

73.7 b

59.0

30.5b

19.2b

11.0b


Urea
+
Phosphoric
Acid
10.7

34.0 b

57. 5d

90.5b

103.2bc

106.7bc

95.7

75,2c

57.7c

26. 0bc


MAP
11.0

277.5c

200.7c

166.5c

138.2c

121.2c

96.7

82.7c

63.2c

40.2c


MAP
+
Sodium
Carbonate
14.7

246.5c

193.5c

158.5c

139.7c

119.7c

95.0

70.7bc

62.0c

40.0c


aAll values are means for four periods per treatment.

b''CdMeans on the same line bearing different superscripts
are significantly (P <.05) different.


















MAP

M................ AP + Base

.-.... -Urea + Acid

.....Urea


) .................
f.~ I J' I I'-- I I ______,-,=:?',,--? -


0.5 1 2 3 4 6 9 12 24
Hours after dosing


FIGURE 5. EFFECT OF TREATMENTS ON RUMEN AMMONIA-N


- 30
rC

0
0
25



S20
1



ci
1d

S10









Statistical analysis of the ammonia-N values at the

individual hours revealed no differences (P <.05) between

the MAP and MAP plus sodium carbonate treatments. Signifi-

cant (P <.05) differences existed between the urea and urea

plus phosphoric acid treatments at hours one, nine and

twelve postdosing. The urea and MAP treatments differed

significantly (P <.05) at all hours postdosing except hour

six. Again, this is similar to the results reported in

Experiment 1 for the urea and MAP treatments.

The effect of treatment on blood urea-N is presented

in Table 15 and Figure 6. The individual data are presented

in Appendix Table 35. No significant differences existed

between treatments in predosing blood urea-N concentrations.

The MAP plus phosphoric acid treatment had a consistently

greater concentration of blood urea-N than the urea treat-

ment throughout the sampling period. However, these

treatments were not found to differ significantly. The MAP

and MAP plus sodium carbonate treatments exhibited similar

changes in blood urea-N concentrations. The urea plus

phosphoric acid treatment had significantly (P <.05) greater

concentrations of blood urea-N than the MAP and MAP plus

sodium carbonate treatments at hours one, two, four and six

postdosing.


Discussion


The results of Experiment 1 suggest that pH of the

rumen contents is a controlling factor in the rate of















TABLE 15. EFFECT OF A SINGLE DOSE OF UREA, UREA PLUS
PHOSPHORIC ACID, MONOAi[ !(!IU:-1 PHOSPHATE, OR
MWj'O'AMMONIUM PHOSPHATE PLUS SODIUM CARBONATE
ON BLOOD UREA-Na


Mg/100 Ml
Urea MAP
+ +
Hours Phosphoric Sodium
After Dosing Urea Acid MAP Carbonate
0 11.2 12.5 11.0 11.0

1 15.2bc 17.8b 13.8c 12.8c

2 16.7bc 19.6b 14.6c 14.3

3 18.8 20.7 17.1 15.6
4 0bc b c c
4 20.2c 21.9 17.1 16.6

6 21.83bc 23.6c 18.5b 18.5b

9 22.5 24.6 19.5 20.1

12 21.7 23.9 20.0 20.3

24 18.9 21.3 18.8 20.6

All values are means for four periods per treatment.

',cMeans on the same line bearing different superscripts
are significantly (P <.05) different.
























*. ,.... ... . : I .. ......... .-o . . . -
- -~m


I.. ... ... .


Urea + Acid
Urea
MAP + Base
MAP


iL .j- -'j-=L==_ = = J ....... 1 ... -= --= ^ .= = ^ i
1 2 3 4 6 9 12 2'
Hours after dosing

FIGURE 6. EFFECT OF TREATMENTS ON BLOOD UREA-N


30-


25-?
II
2o~i
S20-


z 15-


t

0
0u


0 _
ro 5-









ammonia absorption. Of the non-protein nitrogen treatments,

urea resulted in the greatest increase in rumen pH, the least

increase in rumen ammonia-N concentration, and the greatest

increase in blood urea-N. Converse responses resulted with

the monoammonium phosphate (MAP) treatment whereas the

diammonium phosphate (DAP) treatment was intermediate to the

urea and MAP treatments. Urea is hydrolyzed in the rumen

to ammonia and carbon dioxide. However, adding 10 gm of

nitrogen per 45.5 kg body weight in the form of MAP is also

providing the rumen with 20.4 gm of phosphorus, and an

isonitrogenous dose of DAP adds 11.5 gm of phosphorus.

It is possible to explain theoretically the signifi-

cance of rumen pH changes in the absorption of ammonia from

the rumen. It is well recognized that the speed of entry

of any compound into a cell depends largely upon its

molecular volume and its lipoid solubility. It is pre-

sumably for these reasons that ammonia (NH3) enters cells

readily and the ammonium ion' (NH4+) slowly. The proportion

of NH3 to NH4+ present in the rumen contents may be pre-

dicted from the Henderson-Hasselbach equation, with the

appropriate substitution of the pKa value of NH at a
3
temperature of 40C:
NH3
pH = 8.8 + log NH3
-4

From this equation it can be calculated that the propor-

tion of NH3 in the rumen will increase rapidly with a rise

in pH, and that the proportion of NH3 to NH4 + will increase









tenfold for a rise of one unit in the pH level. It is

therefore to be expected that as the pH rises the rate of

absorption of ammonia-N will also rise. Studies supporting

this theory have been reported (Coombe et al., 1960; Hogan,

1961; Bloomfield et al., 1963). All studies showed an

increased rate of absorption from the rumen of ammonia-N

following an increase in rumen pH.

Experiment 2 was designed to examine further the

effect of pH on amnuonia-N absorption from the rumen. The

MAP plus sodium carbonate treatment resulted in rumen pH

values significantly (P< .05) greater than the MAP treat-

ment for all samples taken postdosing except for those at

hours two and twenty-four. The changes in rumen ammonia-N

and blood urea-N concentrations due to these two treatments,

however, were essentially identical throughout the sampling

period.

The urea plus phosphoric acid treatment resulted in

rumen pH values significantly (P< .05) less than the urea

treatment only for hours one-half, one, twelve and twenty-

four postdosing. The difference in pH which occurred early

in the period apparently had some effect on rate of ammonia-

N absorption from the rumen. The urea plus phosphoric acid

treatment had a significantly (P< .05) lower rumen ammonia-N

concentration at one hour postdosing, and throughout the

sampling period exhibited a consistently greater blood urea-N

concentration than the urea treatment. This is the reverse

of the response that would be expected if the rate of









anmionria-N absorption from the rumen were due to rumen pH

per se.

These results are contrary to those reported by

Perez et al. (1]967) when fistulated sheep which had been

fasted 24 hours were dosed per 45.4 kg body weightC with

either 9.3 gm of nitrogen as urea plus 10.7 g-t of phosphorus

as phosphoric acid, or with only 9.3 gm of nitrogen as urea.

They reported that the urea plus phosphoric acid treatment

resulted in a significantly (P <.01) lower rumen pH, a

significantly (P < .05) greater rumen ammonia-N concentra-

tion, and a similar trend in blood urea-N concentration.

Although the results of the treatments involving

phosphoric acid and sodium bicarbonate do not support the

theory that pH is a controlling factor in the rate of

ammonia absorption, support is found by comparing the

results of the urea and MAP treatments. The urea treat-

ment resulted in a significantly (P < .05) higher rumen pH,

a significantly (P< .05) lower rumen ammonia-N concentra-

tion, and a consistently higher blood urea-N concentration

than the MAP treatment.
















C '. -":. I: V


THE PHOSPFI.R!US AVAILA'\BITITY iN .>C' A& *i. :7j AND
_ONOSODYUH PHiOSPItATES FOR G.( T:':G LA:iBS


As previously mentioned in the introduction to Chapter

III, considerable interest has been generated in amfioniated

phosphates due to their property of being both a source of

non-protein nitrogen and phosphorus. The present experiment

was conducted to compare the relative biological avail-

abilities of phosphorus in mono(1atmonium and monosodium

phosphates in growing lambs.


Procedure and Results


Twenty ewe lambs were used in the present experiment.

All lambs were wormed three weeks prior to receiving a

phosphorus depletion type diet containing 0.09% phosphorus

and 1.64% calcium. This diet differed from the basal diet

(Table 16) only by the replacement of 1% corn starch with

calcium carbonate. Venous blood samples were taken at the

beginning and end of a 2-week period on this low-phosphorus,

high-calcium diet. Average initial concentration of plasma

phosphorus was 6.5 mg/100 ml and had dropped to an average

of 3.5 mg/100 ml at the end of this 2-week phosphorus-

depletion period.








TABLE 16. COMPOSITION O DIETS


T treatment
Monoamronium


Ingredient
Dried citrus pulp
Corn starch
Bermuda grass hay, ground
Gelatin
Corn oill1
Dehydrated alfalfa (17%
protein)
Urea (281% protein
equivalent)
Monoammonium phosphate2
Monosodium phosphate2
Salt, trace-mineralized3
Vitamins A and D4


Basal
0.11% P
60.00
13.40
13.00
4.00
4.00

3.00

2.00


0.60
+
100.00


Phosphate
0.15% ~P 0.19% P
60.00 60.00
13.23 13.06
13.00 13.00
4.00 4.00
4.00 4.00


3.00

2.00
0.17

0.60
+
100.00


3.00

2.00
0.34

0.60

100.00


Mono soa Lun
Phosphate
0.15% P 0.17 P
60.00 6 .
13.24 13.08
13.00 13.0
4.00 4.00
4.00 4.00


3.00

2.00

0.16
0.60
+
100.00


3.00
3J 0 iJ

2.00

0.32
0 .0

100.00
O Uk)^
7iY. ( o


FPercent of Diet-


Chemical analysis5
Phosphorus
Ca ci urmn


Magne sium
Crude protein


0.11
1.27
0.11
14.24


0.15
1.28
0.11
14.94


0.19
1.26
0.11
14.50


0.15
1.25
0.11
14.72


1Stabilized with ethoxyquin.

2Upon analysis, monoammonium phosphate and monosodium phosphate contained
25.29% phosphorus, respectively.


0.1.
1.29
G 11.



24.47 an62
24.47 ana


3 Listed minimum analysis in percent: Zn, 1.00; Fe, 0.30; Mn, 0.20; S, 0.10; Cu, C.3:
Co, 0.01; and NaCi, 95.00.
4
2,200 IU vitamin A palmitate and 440 IU vitamin D2 added per kg of concentrate.

All values expressed on as-fed basis.









'The 1as wrCe r,:.:. :-,ily allotted according to weight

~Kand .< a '.i'"'. : 'oosohor),,s con c :ftp-c" -r o the :'i,,

teatme det.- shown in Table 16. The 1anbs e -re housed

individritall.y in elevated p.:n3. A seedless variety of citrus

was used as the source of dried citrus pulp and gelatin was

used as a source of preformed protein low in phosphorus.

Based on the work of Beeson et al. (1944) and Preston and

Pfander (1964), it was felt that a phosphorus level in the

supplemented diets of 0.13% would be below the phosphorus

requirement for these lambs and a level of 0.17% would be

marginal to their requirement. Based upon the analysis of the

depletion diet (0.09% P) adequate supplemental phosphorus

was added at the expense of corn starch to provide these

levels. However, after the experimental diets were mixed

the basal diet contained 0.11% total phosphorus and the

supplemented diets contained 0.15 and 0.19% phosphorus.

Phosphorus, calcium, magnesium and crude protein values for

the diets that were obtained by chemical analyses are also

shown. in Table 16. The high calcium content of these diets

resulted from the addition of calcium containing compounds

during the proc :ssing of the citrus pulp.

The d[, Lti were fed once daily in amounts to give

about a 10? weigh back. The lambs were weighed every 2

weeks and venous blood samples were obtained weekly. At

the end of 9 weeks on the experimirental diets all lambs

were slaughtered and the right ferur removed for analysis.

Following drying aid ether extraction the volume of each









bone was determined by measuring the amount of water dis-

placed by the total bone.

Phosphorus content of feed, plasma and bone was

determined by the colorimetric method outlined by Fiske and

Subbarow (1925) and determinations for calcium and magnesium

were made by atomic absorption spectrophotometry according

to the methods recommended by the manufacturer (Anonymous,

1964). The data were analyzed statistically by analysis of

variance and significant differences between means were

determined using Duncan's New Multiple Range Test (Steel

and Torrie, 1960).

The total weight gains, daily feed intake and feed

efficiency of lambs on the five treatments are presented in

Table 17. Individual data are presented in Appendix Table

36. Two lambs on the 0.19% monosodium phosphate treatment

lost 2.5 and 4.5 kg, respectively, during the 9-week experi-

mental period and were excluded from the data analyses.

The total weight gain's on the 0.19% phosphorus-

monoammonium phosphate diet were significantly (P <.05)

greater than those on the 0.15% phosphorus-monosodium phos-

phate diet and the basal diet. There was an apparent trend

of increasing weight gain and feed consumption with increas-

ing levels of total dietary phosphorus and the greatest

increases occurred with the monoammonium phosphate supplemented

diets.

The level of inorganic phosphorus in plasma is widely

used as an index of the state of phosphorus nutrition of an










TABLE 17. AVERAGE INITIAL AND FINAL WEIGHT, DAILY GAIN, FEED
INTAKE AND FEED EFFICIENCY OF LAMBS FED DIFFERENT SOURCES
AND LEVELS OF PHOSPHORUS DURING A 9-WEEK GROWTH TRIAL


Treatment
Monoammonium Monosodium
Basal Phosphate Phosphate
Item 0.11% P 0.15% P 0.19% P 0.15% P 0.19% P

Number of animals 4 4 4 4 2

Initial weight, kg 25.96 26.30 26.87 26.64 26.08

Final weight, kg 28.17 30.21 32.99 29.02 31.18

aab b a ab
Weight gain, kg 2.21 3.91 6.12 2.38 5.10

Daily feed intake, kg 0.62 0.73 0.80 0.66 0.74

Feed/unit gain, kg 16.58c 12.45 8.47 23.08c 9.38

abMeans on the same line bearing different superscripts are significantly (P <.05)
different.
CNo analysis of variance of feed efficiency values was conducted because one animal
in each of these treatment groups only maintained its weight.









animal. Table 18 summarizes the plasma phosphorus, calcium

and magnesium levels at regular times during the course of

the experiment. Individual data for inorganic plasma phos-

phorus, calcium and magnesium are presented in Appendix

Tables 37-39. Lambs receiving Lhe basal diet had lower

plasma phosphorus levels throughout the experiment than

lambs receiving supplemental phosphorus. There were no

significant differences in plasma phosphorus levels between

supplemental phosphorus sources or levels. There was a

tendency for plasma calcium levels of lambs receiving supple-

mental phosphorus to decrease following the third week of

the experiment. Plasma levels of all minerals analyzed

tended to decrease during the final 2 weeks. However, none

of these changes were significant.

Table 19 summarizes the data collected from the femurs

of lambs on the five treatments. Individual data are pre-

sented in Appendix Tables 40-41. There were no significant

differences between treatments in weight of dry, fat-free

bone nor in bone ash content. These values were numerically

greater, however, in the bones of lambs having received the

highest supplemental levels of phosphorus. The percent

phosphorus of bone ash was highest for lambs having received

supplemental phosphorus with the difference between the basal

treatment and the treatment containing the highest level of

monoammonium phosphate being significant (P< .05). The

percent calcium and magnesium of bone ash was likewise

numerically higher for lambs having received supplemental












TABLE 18. AVERAGE PHOSPHORUS, CALCIUM AND MAGNESIUM LEVELS
IN PIA.S A OF LAMBS FED DIFFERE iT SOURCES AND LEVELS
OF PHOSPHORUS DURING A 9-WEEK GROWTH TRIAL


Phosphorus Weeks on Trialab
Source Percent 0 3 6 9 Rc
Phosphorus (mg/100 ml plasma)
Basal 0.11 3.60 4.09 4.99 4.54 4.54
Monoammonium 0.15 3.20 4.90 5.92 4.88 5.23
Monoammonium 0.19 3.56 4.90 6.37 5.19 5.49
Monosodium 0.15 3.37 5.50 5.94 5.47 5.64
Monosodium 0.19 4.05 5.79 6.86 4.80 5.82

Average 3.56 5.04 6.02 4.98


Calcium (mg/100 ml plasma)
Basal 0.11 9.53 10.99 11.27 9.92 10.73
Monoanmmonium 0.15 10.30 10.85 10.70 9.56 10.37
Monoammnonium 0.19 10.38 10.12 10.17 9.39 9.89
Monosodium 0.15 11.04 10.55 9.75 9.50 9.93
Monosodium 0.19 11.01 11.54 10.65 9.59 10.59

Average 10.45 10.81 10.51 9.59


Magnesium (mg/100 ml plasma)
Basal 0.11 1.95 2.13 2.41 2.27 2.27
Monoammonium 0.15 1.67 2.07 2.22 2.11 2.13
Monoanmonium 0.19 1.79 2.05 2.26 2.12 2.14
Monosodium 0.15 1.79 2.08 2.14 2.02 2.08
Monosodium 0.19 2.07 2.47 2.48 2.24 2.40

Average 1.85 2.16 2.30 2.15

aEach value under weeks 3, 6 and 9 is the average of three
weekly sampling periods.
bStatistical analyses were conducted on the changes in
plasma mineral concentrations between the initial con-
centrations and the averages of every 3 consecutive weeks.
COverall mean of the nine weekly sampling periods.
Overall mean of the nine weekly sampling periods.










TABLE 19. AVERAGE MEASUREMENTS AND MINERAL CONCENTRATIONS OF
THE RIGHT FEMUR OF LAMBS FED DIFFERENT SOURCES AND LEVELS
OF PHOSPHORUS DURING A 9-WEEK GROWTH TRIAL


Treatment
Monoammonium Monosodium
Basal Phosphate Phosphate
item 0.11.% P 0.15% P 0.19% P 0.15% P 0.19% P
Number of animals 4 4 4 4 2
Weight of dry, fat-free
bone, gm 45.27 44.38 47.31 44.61 45.93
Ash, % of dry, fat-free
bone 64.23 63.79 66.06 65.88 66.28
Phosphorus, % of ash 15.86a 16.39ab 16.56b 16.49ab 16.30ab
Calcium, % of ash 35.42 35.74 35.78 34.79 35.53
Magnesium, % of ash 0.108a 0.733a 0.723a 0.750a 0.859b
Volume of dry, fat-free
bone, ccc 59.96 57.86 61.20 59.09 56.43
Dry, fa--free weight
mg/cc0 755 767 773 755 814
Ash weight, mg/cce 469 490 506 498 540


a,' Means on the same line
different.


bearing different superscripts are significantly (P< .05)


cThe volume of water displaced by the total, dry-fat-free bone.

Ratio of the total dry-fat-free weight in mg to the volume of water displaced by
the total dry-fat-free bone.
Ratio of the total ash weight in mg to the volume of water displaced by the total
dry-fat-free bone









phosphorus. The 0.19% rmonosodium phosphate treatment group,
Which consitC.d of to. lambs, resuI. .d in signiFica.nty

(P <.05) greater bone ash concentrations of -magnesiumi than

the other treatment groups. Expressing the dry, fat-free

weights and the ash weights of the bones as mg per cc

resulted in the general trend of increasing vLlues with

increasing levels of phosphorus.


Discussion


The relative availabilities of the phosphorus in

many inorganic phosphorus sources have been evaluated for

ruminants using animal growth studies (Long et al., 1957;

Wise et al., 1961; Perez et al., 1967). Parameters often

measured in such studies are rate of gain, feed6 intake,

inorganic blood phosphorus, and various bone measurements.

The present study was designed to include three

levels of phosphorus; two were to be inadequate for normal

growth and performance and the third level was to be

marginal. All treatment diets used, however, analyzed 0.02%

higher in total phosphorus than anticipated. The lowest

supplemental phosphorus treatment, which contained 0.15%

total phosphorus, was probably marginal with respect to

the level of phosphorus needed for normal lamb growth.

Beeson et al. (1944) foun;id diets containing 0.15% total

phosphorus to be adequate for supporting good rate of gain,

efficient feed utilization and normal blood phosphorus

levels in fattening lambs.









In the present r ..'iment, treatment groups receiving

sui'ppe:r. .!a], p osphorus as monoi Gfow' pI.u'A }hosphate had

numerically gre(.er average daily fe-ed intakes and gains

than groups receiving diets supp.eented with monosodium

phosphate. The plasma and bone analyses, however, did not

show consistent trends for either sources of organicnc

phosphorus.

Both the 0.15 and 0.19% total phosphorus levels in

the supplemented diets were apparently adequate to support

normal bone metabolism and a normal serum phosphorus level

in the growing lambs. Long et al. (1957) reported linear

increases in feed intake, weight gains and serum inorganic

phosphorus levels with steers receiving 0.07, 0.11 and

0.15% total dietary phosphorus, whereas a phosphorus level

of 0.19% gave results similar to the 0.15% phosphorus

treatment.

In spite of the limitation of the present experiment

of higher than desired experimental levels of phosphorus in

the diets, it can be concluded that the phosphorus in

mono aimionium phosphate was as well utilized by the growing

lambs as that from monosodium phosphate. This result is

consistent with studies in which diammonium phosphate

(Oltjen et al,, 1963; Hillis, 1968), urea-phosphate (Perez

et al., 1967), and phosplhoric acid (Richardson et al., 1957;

Tillman and Brethour, 19580) have been found to be readily

available sources of phospho-.us to ruminants.
















CHAPTER VI


EFFECT OF AGE AND DIETARY LEVEL OF MAGNESIUM
ON MAGNESIUM UTILIZATION BY SHEEP


The availabilities of magnesium stores in the body

for mobilization during periods of stress or magnesium

deficiency are believed to decrease with age. Wilson (1960)

suggested that the greater frequency of hypomagnesaemic

tetany in mature animals may be partly due to their de-

creased ability to mobilize reserves of magnesium from

bone as readily as the young animal.

In the present experiment the effect of age on

magnesium utilization by sheep was determined using

balance techniques and estimates were made of the dietary

magnesium requirements for maintenance of the different

age groups.


Procedure and Results


Thirty-six Florida native wethers (12 lambs, 12

yearlings and 12 adult sheep) were randomly assigned, within

age groups, to three dietary levels of magnesium. The

levels were calculated to be 330, 660 and 990 ppm magnesium

but the diets fed were found to contain 400, 650 and 950 ppm

magnesium, respectively. The supplemental magnesium was

supplied as the carbonate by addition of the desired levels

80









to a seai -pur.1ied diet (Table 20) at the expense of corn

starch. Te dit cotaied 0.20! phosphors, 0.22- cral cium

and 11.6% crude p-otein nup. analysis.

All anima.s had received a coin-hay based diet for

the previous 66 days and had been treated twice for in-

testinal parasites. The animals were housed individuallyy

in raised metabolism crates and fed once daily their

respective treatment diet at a computed maintenance level,

Thiis level was calculated by first determining the amount

of metabolizable energy (ME) each sheep would need for

maintenance by the formula:

1.33 x 70 (kg0.75) kilocalories

where 70 kg 07is an estimate of the energy needed for

basal metabolism and the factor 1.33 is an estimate of the

unavoidable daily activity of an animal. Values of ME for

all ingredients were not available and estimates were made

for these. The estimated ME content of the diet was 2.125

kilocalories per kilogram of dry matter and the intake of

this diet needed for maintenance was calculated to be 50 gm
0.75
daily per kg of metabolic body weight (kg ) as illustrated

in Table 21. This computed maintenance level proved

approximately accurate, based upon an average initial weight

(41.4 kg) and average final weight (41.8 kg) at the end of

31 days in the metabolism crates. Tap water was provided

ad libhitum.

A 21-day preliminary feeding period was followed by

a 7-day collection period. During the collection period











TABLE 20. COMPOSITION OF EXPERIMENTAL DIET


Ingredient
Corn cobs and shucks, ground
Pure soy protein1
Urea
Cerelose
Corn starch
Corn oil2
Trace mineral mixture
Salt
Calcium carbonate (40% calcium)
Monosodium phosphate (25% phosphorus)
Vitamins4
Variables


35.50
7.50
1.50
18.00
31.62
3.00
0.24
0.60
0.57
0.47
+
1.00
100.00


iPure soy protein C-l--Skidmore Enterprises, Cincinnati,

Ohio.

2Stabilized with ethoxyquin.


Ingredients
Sulfur (Na2 SO4)
Iron (FeSO4)
Zinc (ZnCO3)
Manganese (MnCO3)

Copper (CuSO4)
Iodine (KI)
Cobalt (CoCO3)


% of Mixture
81.37
11.13
3.93
2.14


Mineral added to diet, ppm
450
100


1.00
0.27
0.16
1i00.00


42,200 IU vitamin A palmitate, 440 IU vitamin D2 and 11 mg
DL alpha tocopherol added per kg of diet.

Variable levels of MgCO3; corn starch was added or removed
to adjust to 100%.













TABLE 21. AGE SPECIFICATIONS, BODY WEIGHTS AND FEED OFFERED


No. Age


Age
Specifications

Lambs (6-12 mos.)

Yearlings (1-2 yrs.)

Adult sheep (2-3 yrs.)


Average Weight, kg 0.75
Initial Final W

28.8 29.0 12.4

44.0 44.7 17.2

50.5 50.9 18.9


Feed
Daily Feed Offered
(gm) (gm/WO-75)

620 50

860 50

945- 50


Group

I

II

III


No.
Animals

11

13

12









t;l f *-cc-'.] Anid urinary co]llict 'i* s .:0-e made at '24-ho.ur

>2 S (9 (.9(fl

a rcxi,)7-]'a& l I ,. 00 ml of a 2 -. ,A I .ti.lo'i and 1- 0 li of

toluene. had b,'-n added. [rine volumes c-ee recordJ daily

and a 10% aliquot was saved forx chemical analysis. (eces

were collected daily using fecal collection b-,gs. Blood

samples were obtained by jugular puncture for 3 consecutive

days at the end of the collection period, and the plasma; was

obtained for each sample for the det.rination of ;anesium,

calcium and phosphorus.

The 7-day fecal collections 7ere pooled, thoroughly

mixed, and dried to a constant weight in a forced air oven

at approximately 60C. The dried excreta were allowed to

gain moisture from the atmosphere for 72 hours, after which

they were weighed, ground finely, iand an aliquot saved for

gross energy, magnesium, calcium and phosphorus determinations.

A sample of the urine as collected was saved for gross

energy determinations. The remainder was filtered i:hrough

Whatman No. 42 filter paper and approximately 100 ml kept

for magnesium, calcium and phosphorus determinations.

Energy content of diets, feces and urine was deter-

mined by combustion in a Parr oxygen bomb adiabatic calori-

meter. Urine samples were prep cd by --atur:ating a tared

cellulose pellet in a coT.bustion capsule with 5 i1; of urine

and dying in a vacuum des'.ccator. Tata .Iare corrected for

energy value. cif the %cel]i]o oe used .i!-h rv.eh samela portiion.

Acid and sulfur corrections (aarr i-anual No. 130, -1.960) were