UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Energy and protein requirements of ewes, and the use of non-protein nitrogen [sic] by ewes and early… Naseem, Muhammad Zafarullah 1970

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Notice for Google Chrome users:
If you are having trouble viewing or searching the PDF with Google Chrome, please download it here instead.

Item Metadata

Download

Media
831-UBC_1970_A6_7 N38.pdf [ 5.88MB ]
Metadata
JSON: 831-1.0102047.json
JSON-LD: 831-1.0102047-ld.json
RDF/XML (Pretty): 831-1.0102047-rdf.xml
RDF/JSON: 831-1.0102047-rdf.json
Turtle: 831-1.0102047-turtle.txt
N-Triples: 831-1.0102047-rdf-ntriples.txt
Original Record: 831-1.0102047-source.json
Full Text
831-1.0102047-fulltext.txt
Citation
831-1.0102047.ris

Full Text

ENERGY AND PROTEIN REQUIREMENTS OF EWES AND THE USE OF NON-PROTEIN NITROBEN BY EWES AND EARLY WEANED LAMBS tar MUHAMMAD ZAFARULLAH NASEEM M.Sc», West Pakistan Agricultural University, 1966 A THESIS SUBMITTED IN PARTIAL FULFIIMENT OF THE REQUIREMENTS FOR THE DEGREE OF M.SC. in the Department of Animal Science We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA April, 1970 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree tha permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department The University of British Columbia Vancouver 8, Canada ABSTRACT In order to investigate the n u t r i t i o n a l requirements of ewes during late pregnancy and early l a c t a t i o n , two groups of ewes were given 90 gms. D i g e s t i b l e Crude Protein (D.C.P.) during pregnancy and 225 gms. D.C.P./ head/day during early l a c t a t i o n . During the l a s t - s i x . weeks of pregnancy ewes i n Group II, provided with maintenance + 100%, requirement of D i g e s t i b l e Energy (D.E.) made s i g n i f i c a n t l y greater liveweight gains (P<0.01) than those i n Group I and fed maintenance + 50%, D.E. During early l a c t a t i o n ewes i n Group I, provided with maintenance + 150%, D.E. l o s t s i g n i f i c a n t l y less weight (P<0.05) than those i n Group I I which were given maintenance + 100%, D.E. There were no s i g n i f i c a n t differences i n milk y i e l d and milk composition between the two groups, however pre-weaning lamb growth i n Group I was s i g n i f i c a n t l y greater (P<0.05) than that i n Group I I . Average d a i l y gain of weaned lambs (weaned at 8 to 10 weeks of age) given p e l l e t e d rations containing 20%, protein was s i g n i f i c a n t l y greater (P<0.05) than those given 16%, protein but there were no s i g n i f i c a n t differences between lambs fed 20% or 13% and between 167<, or 13%, crude p r o t e i n . A higher proportion of single lambs i n the group given 137.. protein may have accounted i n part for the better gain of t h i s group. Results of the digestion t r i a l with these lambs indicated that there were no s i g n i f i c a n t differences (P<0.05) i n the dry matter d i g e s t i b i l i t y and the protein d i g e s t i o n c o e f f i c i e n t of the three types of p e l l e t s but the nitrogen retention was greatest i n the lambs fed the 20%, p r o t e i n . The r e s u l t s of the second experiment conducted, to study the e f f e c t of non-protein nitrogen i n the form of urea on milk y i e l d and milk composition of ewes indicated that there were no s i g n i f i c a n t differences i n milk y i e l d , milk composition and milk urea N l e v e l of the three groups of ewes fed equal amounts of supplemental nitrogen, during early l a c t a t i o n , as soybean, soybean + urea and urea alone. Ewes fed soybean or soybean + urea had s i g n i f i c a n t l y lower plasma urea nitrogen l e v e l s (P<0.05) than those supplemented with urea alone. There was no s i g n i f i c a n t difference between the plasma urea nitrogen l e v e l of the former two groups of ewes. There were no s i g n i f i c a n t differences i n the pre-weaning growth of lambs nursing ewes fed on p e l l e t s containing soybean + urea and urea alone but the lambs from ewes fed soybean made s i g n i f i c a n t l y slower (P<0.05) gain than those from the other two groups. .The reason for t h i s slower rate of gain i s d i f f i c u l t to explain. Results of the t r i a l conducted to investigate the use of urea nitrogen i n early weaned lambs indicated that the lambs fed on p e l l e t s containing soybean made s i g n i f i c a n t l y greater gains (P<0.05) than those on p e l l e t s containing urea as the sole source of supplemental nitrogen. There were however, no s i g n i f i c a n t differences i n weight gain of lambs fed on p e l l e t s containing soybean or soybean + urea and between soybean + urea or urea alone. There were no s i g n i f i c a n t differences between plasma urea nitrogen l e v e l of lambs fed on soybean or soybean + urea containing p e l l e t s and these lambs had s i g n i f i c a n t l y higher (P<0.05) l e v e l s of plasma urea nitrogen than those fed on p e l l e t s containing urea alone. The v a r i a t i o n i n the blood urea l e v e l of the lambs was thought to be due to v a r i a t i o n i n protein intake. Results of the dige s t i o n t r i a l with lambs showed that there were no s i g n i -f i c a n t differences i n the protein digestion c o e f f i c i e n t s and dry matter d i g e s t i b i l i t i e s of these types of r a t i o n s . P e l l e t s providing nitrogen from soybean r e s u l t e d i n greatest nitrogen re t e n t i o n . Results show that urea did not influence the milk y i e l d or milk composition of the.ewes but i t was a poor source of nitrogen for early weaned lambs. TABLE OF CONTENTS I Introduction Review of the Literature II Ewe Nutrition in Pregnancy and Early Lactation III Early Weaning and Feeding of Lambs IV Urea - Nutritional Importance as a Non-Protein Nitrogen Source V Effect of Feed Urea on Milk Yield and Milk Composition 37 ¥1 Experimental 46 Experiment No. I Animals. Used 46 Feeding 4.6 Energy Levels and Feed Supply 47 Milking of Ewes and Analysis of Milk Samples A8 Weaning of Iambs 49 Digestibility study 49 Experiment No. II Management 51 Milk Yield 51 Blood Analysis 52 Growth of Lambs 53 Digestion Trial 53 PAGE 1 3 3 17 23 TABLE OF CONTENTS (Continued) Page VTI Results and Discussion 54 Experiment I 54 Experiment II 69 VIII Literature Cited 87 IX Appendices ^ 2 LIST OF TABLES Experiment I  Table I II III IV V VI VII VIII IX X XI Experiment II  Table XII XIII XIV XV XVI XVII XVIII XIX XX XXI XXII XXIII Page Average Weight of Ewes 57 Ewes Average Daily Milk Yield 58 Single Lamb Growth (Pre-weaning) 59 Twin Lamb Growth (Pre-weaning) 59 Average fat Percentage of Milk 60 Average Protein Percentage of Milk 60 Average Lactose Percentage of Milk 60-A Post-weaning Lamb Growth 63 Feed Efficiency Ratio 66 Digestion Trial of Lambs -Dry Matter. Digestibility 67 Digestion Trial of Lambs -Nitrogen Digested and Retained 68 Ewes Average Daily Milk Yield 71 Average Fat Percentage of Milk 72 Average Protein Percentage of Milk 73 Average Lactose Percentage of Milk 73-A Average Total Solids Percentage of Milk 74. Ewes Average Milk Urea N 75 Ewes Average Plasma Urea N 77 Lamb Growth (Pre-weaning) 78 Lamb Growth Rate (Post-weaning) 81 Lambs Average Plasma Urea N 82 Digestion Trial of Lambs - Dry Matter Digestibility 83 Digestion Trial of Lambs - Nitrogen Digested 84. and Retained ACKNOWLEDGMENTS The write r wishes to thank Dr. M. T a i t for h i s encouragement and guidance throughout the course of t h i s study. Sincere thanks are also extended to Mr. T. Choa of the P r o v i n c i a l Government Dairy Branch Laboratory for analyzing milk samples. Further thanks are extended to Dr. W. D. K i t t s , Chairman of the Department of Animal Science, for the use of necessary f a c i l i t i e s for thi s study. 1. I. INTRODUCTION The short interval.from weaning to mating i n sheep production systems involving twice yearly lambing or three lamb crops i n twenty four months necessitates the r e a p p r a i s a l of the nutrient requirements of ewes. Normally i t i s considered that moderate feeding during l a t e pregnancy followed by high-energy feeds i n early l a c t a t i o n gives the best r e s u l t s i n terms of lambs production and economy. Such a system usually involves a loss of body weight by the ewe during l a c t a t i o n . This being accepted and compensated for p r i o r to rebreeding. I t i s proposed that good body condition may be attained by feeding at a higher l e v e l than normal during l a t e gestation ( i n excess of the ewes requirements for maintenance and pregnancy) and accepting body weight loss i n early l a c t a t i o n . The a l t e r n a t i v e Is to meet the energy and protein requirements i n early l a c t a t i o n by high grain feeding i n order to maintain body condition. This thesis presents the findings of an experiment which was so designed that one group of ewes received energy and p r o t e i n to meet the requirements of l a t e pregnancy and then as c l o s e l y as possible for l a c t a t i o n . The second group received the same t o t a l amount of energy during l a t e pregnancy and early l a c t a t i o n but evenly divided over the two periods. Since the lambs may have to be weaned early i n intensive production systems, the p r o t e i n requirements of early weaned lambs were also i n v e s t i -gated. There i s evidence that urea nitrogen can be u t i l i z e d by the l a c t a t i n g dairy cow without detrimental e f f e c t s on milk y i e l d and composition. Comparable work with sheep has not been c a r r i e d out. The r e s u l t s of a further experiment are presented which was conducted to study the e f f e c t of urea nitrogen on milk y i e l d and milk composition of ewes. Three groups of ewes were provided equal amounts of supplemental nitrogen, during early l a c t a t i o n , from three d i f f e r e n t r a t i o n s containing soybean, soybean + urea and urea alone. The use of urea nitrogen i n early weaned lambs was also investigated by feeding the above-mentioned rations for 16 weeks subsequent to weaning at eight weeks of age. REVIEW OF LITERATURE I I ' . EWE NUTRITION IN PREGNANCY AND EARLY LACTATION 3. C o n s i d e r a b l e i m p o r t a n c e h a s b e e n a t t a c h e d t o t h e f l u s h i n g o f ewes b e f o r e m a t i n g a n d t h i s h a s become common p r a c t i c e i n many c o u n t r i e s . F l u s h i n g h a s a s i g n i f i c a n t e f f e c t o n i n c r e a s i n g t h e number o f e g g s s h e d a n d h e n c e t h e number o f l a m b s p r o d u c e d ( C o o p , 1966) b u t t h e r e a r e o t h e r p e r i o d s w h e n t h e n u t r i t i o n a l s t a t u s o f t h e ewe i s i m p o r t a n t . The g e s t a t i o n p e r i o d o f t h e ewe i s n e a r l y 2 1 w e e k s , d u r i n g t h e f i r s t 10 w e e k s o f p r e g n a n c y f o e t a l w e i g h t i n c r e a s e i s s m a l l . A s t h e r e i s l i t t l e e x t r a demand f r o m t h e f o e t u s f o r n u t r i m e n t a t t h i s t i m e , o n l y a m a i n t e n a n c e r a t i o n i s r e q u i r e d f o r t h e e w e . De C l e e n e ( 1 9 6 8 ) s t a t e d t h a t i n t h e l a s t f o u r w e e k s b e f o r e l a m b i n g t h e f o e t u s n e a r l y d o u b l e s i t s w e i g h t . I t i s d u r i n g t h i s m o n t h t h a t t h e n u t r i t i o n o f t h e ewe i s i m p o r t a n t b e c a u s e i t c a n a f f e c t t h e s i z e o f t h e lamb b o r n . R a i s i n g t h e e w e ' s p l a n e o f n u t r i t i o n t o a h i g h l e v e l w o u l d mean a h e a v i e r l a m b a t b i r t h . T h i s c o u l d r e s u l t i n a n a l r e a d y l a r g e u n b o r n s i n g l e lamb i n i n c r e a s i n g i t s b i r t h w e i g h t by a n e x t r a p o u n d . The i n c r e a s e d w e i g h t c o u l d make t h e d i f f e r e n c e b e t w e e n a n e a s y a n d a d i f f i c u l t b i r t h a n d t h e r e f o r e a f f e c t t o t a l lamb l o s s e s . He f u r t h e r s t a t e d t h a t s u b j e c t i n g t h e ewe t o a l o w f e e d i n g l e v e l d u r i n g l a t e p r e g n a n c y , o n t h e o t h e r h a n d , a l s o s h o u l d b e a v o i d e d , a s t h i s w o u l d mean t h a t t h e lamb p r o d u c e d w o u l d b e l i g h t e r a t b i r t h . A s m a l l lamb may be t o o w e a k t o f e n d f o r i t s e l f a n d s u b s e q u e n t l y d i e . T h i s i s p a r t i c u l a r l y r e l e v a n t t o t w i n l a m b s . He s t a t e d t h a t a l t h o u g h a l a r g e p r o p o r t i o n o f l i g h t l a m b s s u r v i v e p a r t u r i t i o n , a g r e a t number o f t h e s e w i l l d i e i n t h e i r f i r s t w e e k . He p o i n t e d o u t t h a t f e e d i n g l e v e l s a l s o h a v e a n e f f e c t o n t h e ewe i n a d d i t i o n t o t h e e f f e c t o n t h e l a m b . E x c e s s f e e d i n g d u r i n g e a r l y p r e g n a n c y , when v e r y l i t t l e demand i s b e i n g made b y t h e f o e t u s o n t h e e w e , r e s u l t s i n a b u i l d u p o f e x c e s s b o d y f a t . T h i s i n t u r n l o w e r s t h e a n i m a l ' s g e n e r a l f i t n e s s . He s a i d t h a t d i f f i c u l t y at p a r t u r i t i o n i s p a r t l y a h e r i t a b l e t r a i t but the incidence i s higher i n animals carrying too much condition when approaching lambing. He further stated that pregnancy toxaemia i s a constant threat near the end of gestation when demands on the ewe are reaching a peak. I f the amount of carbohydrate the ewe requires i s greater than that a v a i l a b l e through feed intake, then body f a t reserves w i l l be catabolized. As a r e s u l t toxins (acetone, acetoacetic a c i d and B-hydroxybutyric acid) are produced i n l i v e r , rumen epithelium and mammary gland which may cause ewe's death from pregnancy toxaemia. He concluded that i t i s important to keep the ewes on maintenance rati o n s during early and mid-pregnancy with a gradually r i s i n g plane of n u t r i t i o n over the l a s t few:.weeks before lambing. During early pregnancy ewes should be fed to maintain a constant body weight. Coop (1962) stated that under confined conditions ( 4 f t . x 6 f t . enclosures) a 45 kg. (100 lb.) sheep requires 0.96 l b . T.D.N. (1920&calories D.E.) or 0.92 l b . d i g e s t i b l e organic matter to maintain a constant body weight. Langlands, Corbett, McDonald and Pu l l a r (1963) estimated that the maintenance requirement of a 100 l b . housed sheep was 0.82 l b . d i g e s t i b l e organic matter. Investigations into the e f f e c t of protein intake during the second h a l f of pregnancy on lamb b i r t h weights and ewe milk y i e l d during early l a c t a t i o n have given v a r i a b l e r e s u l t s . Slen and Whiting (1952) fed ewes i n d i v i d u a l l y during l a t e gestation and early l a c t a t i o n , rations containing 7, 10 and 137,, t o t a l p rotein (3.3, 6.3 and 8.1% d i g e s t i b l e crude protein) to study the influence of protein intake on body weight of ewes and b i r t h weight and growth of the lambs. Average d a i l y intakes of d i g e s t i b l e crude p r o t e i n and t o t a l d i g e s t i b l e nutrients for the three l e v e l s of protein during l a t e 5 . g gestation and early l a c t a t i o n were 0 . 1 3 l b . D.C.P. ( d i g e s t i b l e crude protein) and 1 . 7 l b . T.D.N, ( t o t a l d i g e s t i b l e n u t r i e n t s ) ; 0 . 2 3 l b . D.C.P. and 1 . 9 l b . T.D.N.; and 0 . 2 9 l b . D.C.P. and 1 . 9 l b . T.D.N. Results showed that the ewes receiving low protein ( 7 7 » ) r a t i o n did not gain as r a p i d l y as the two groups rec e i v i n g higher l e v e l s but there was no d i f f e r e n c e between groups receiving 1 0 7 o and 1 3 7 o t o t a l protein. Average body weights of the ewes 6 weeks before lamb ing were 1 5 4 , 1 6 0 and 1 6 0 l b . ; 2 weeks before lambing, 1 6 0 , 1 6 8 and 1 7 1 l b . ; and immediately a f t e r lambing, 1 3 5 , 1 5 0 and 1 5 2 l b . for 7 , 1 0 and 1 3 7 o t o t a l protein, r e s p e c t i v e l y . Both the single and twin lambs from the ewes re c e i v i n g the higher l e v e l s of protein were s i g n i f i c a n t l y heavier than the lambs from ewes receiving the low protein r a t i o n . There were no s i g n i f i -cant differences i n b i r t h weights of lambs from ewes receiving the two higher l e v e l s of protein i n d i c a t i n g that extra protein fed to ewes receiving the highest l e v e l of protein was of no a d d i t i o n a l value i n increasing these weights. Many of the lambs from the ewes on the low protein r a t i o n were weak at b i r t h , three ewes of the 2 4 lambing i n t h i s group had no milk and another s i x had i n s u f f i c i e n t milk to nurse one lamb and none had s u f f i c i e n t milk to r a i s e twin lambs. I t was evident from t h i s experiment that 0 . 1 3 l b . of d i g e s t i b l e crude protein d a i l y during pregnancy was not s u f f i c i e n t to produce a vigorous lamb or s u f f i c i e n t to produce milk for nursing lambs. The s i n g l e lambs and twin lambs raised as singles i n the two higher protein groups were heavier at six weeks of age and at weaning time than lambs raised i n low protein groups. A l l ewes receiving the two higher l e v e l s of protein had s u f f i c i e n t milk for one lamb and many had s u f f i c i e n t for twins. Klosterman, Bolin, Buchanan, B o l i n and Dinusson ( 1 9 5 3 ) experimented with ewes of about 1 2 0 l b . l i v e weight and found no s i g n i f i c a n t differences i n lamb b i r t h weights between intakes of 0 . 1 0 and 0 . 2 8 l b . d i g e s t i b l e crude protein per ewe d a i l y . However ewe mortality was higher on the lower protein intake and milk y i e l d as assessed by the growth of twin lambs was also adversely a f f e c t e d . P h i l l i p s o n (1959) concluded that 0.25 l b . d i g e s t i b l e crude protein per day should be adequate for the 140 l b . ewe during the l a s t s i x weeks of gestation. National Research Council (1968) recommended 0.20 l b . d i g e s t i b l e crude protein per day during the l a s t six weeks of gestation for a ewe of 140 l b . l i v e weight or more. Gardner and Hogue (1963) experimented with ewes to determine the T.D.N, ( t o t a l d i g e s t i b l e nutrients) requirements of pregnant and l a c t a t i n g ewes. The l e v e l " of T.D.N, used was that recommended by National Research Council (1957) for 130 l b . ewes during the l a s t 6 weeks of gestation (1.77 l b . T.D.N, per 100 lb.bd)%iwe^h'tr3)&n<i f ° r t n e f i r s t 8 to 10 weeks of l a c t a t i o n (2.3 l b . T.D.N, per 100 l b . body weight). The l e v e l of T.D.N, tested was as above or 75, 100 or 1257o of those values before or a f t e r lambing or throughout. The l e v e l of protein used was the same as that of N.R.C. (0.23 l b . d i g e s t i b l e crude p r o t e i n during l a s t six weeks of gestation and 0.3 l b . during l a c t a t i o n ) Their r e s u l t s showed that varying T.D.N, le v e l s for ewes during the l a s t s ix weeks of gestation did not a f f e c t single lamb b i r t h weights but feeding higher l e v e l s s i g n i f i c a n t l y increased twin b i r t h weights. Feeding higher T.D.N, l e v e l s during gestation s i g n i f i c a n t l y increased the average 90 day weight of twin lambs and feeding higher l a c t a t i o n l e v e l s to ewes increased the 90 day weights of both single and twin lambs. The r e s u l t s also showed that ewes with single lambs, approximately maintained th e i r body weight from si x weeks pre-parturn to one day post-partum and to 90 day post-partum when fed the present N.R.C. standard whereas ewes with twins required approxi-mately the 125% l e v e l . These data indicated that the present N.R.C. - T.D.N. standard was apparently s a t i s f a c t o r y for ewes pregnant with single lambs but increased l e v e l s for ewes pregnant with twin lambs seemed advisable. Wright, Pope, and P h i l l i p s (1964) stated that oat straw, maize cobs and low-quality hay as roughages each supplemented with minerals and protein given as p e l l e t s were s a t i s f a c t o r y for pregnant and lactating ewes. Various le v e l s of feed energy have been investigated during late pregnancy. Jordan (1966) reported that hay rations providing about 3000 K. c a l o r i e s and high concentrate rations providing 1800 K. c a l o r i e s of diges-t i b l e energy per ewe d a i l y during summer, nonpregnant dry period of four months resulted i n weight losses of about 1 and 5 Kg. r e s p e c t i v e l y . Weight changes were s i g n i f i c a n t l y d i f f e r e n t . During gestation about 3*®i0 and 3930 K. c a l o r i e s (D.E.) per ewe d a i l y were provided by hay and high concentrate r a t i o n s , r e s p e c t i v e l y . Results indicated that weight gains were not s i g n i f i c a n t l y d i f f e r e n t and averaged 18.8 and 16.5 Kg. per ewe, r e s p e c t i v e l y . He further stated that lamb weights taken at b i r t h and at 30 days of age were not aff e c t e d by the summer and gestation treatments of their dams, suggesting that a l l r a t i o n s were s u f f i c i e n t l y adequate to provide ample nutrients f o r the developing foetus and for milk production. I t has been shown that body weight of ewes markedly, a f f e c t s the weaning weight and to a lesser degree the b i r t h weight of lambs. Ray and Smith (1966) analyzed b i r t h and weaning weight records ofllambs. They declared that age of dam (from 2 to 7 years) did not s i g n i f i c a n t l y a f f e c t weight of lambs at b i r t h . Twin ram lambs were 0.59 Kg. heavier at b i r t h and 1.8 Kg. heavier at weaning (120 days of age) than twin ewe lambs. There was a 5«.63 Kg. increase i n weaning weight, when weaned at 120 days of age, with each kilogram increase i n b i r t h weight. The greatest response of weaning weight to increase i n b i r t h weight occurred i n single lambs. The body weight of the ewes markedly affected the weaning weight and to a lesser degree the b i r t h weight of lambs. They stated that s e l e c t i o n of heavy replacement ewe lambs for the breeding f l o c k would be desirable (depending upon the extra cost of feeding heavy ewes). As the body weight of ewes j. L. increased there was a s i g n i f i c a n t increase i n weaning weights of lambs. The heaviest ewes weighing 5 9 . 5 to 6 3 . 6 Kg. produced lambs that weighed 9 7 o and 2 0 7 o more at b i r t h and weaning res p e c t i v e l y , than ewes i n the l i g h t e s t group weighing 4 1 , ; 4 to 4 5 . 5 Kg. Nedkv£<tnena ( 1 9 6 7 ) conducted t r i a l s with ewes fed indoors on hay or s i l a g e or both from before mating to 2 to 3 weeks a f t e r lambing and i n the l a s t 2 or 8 weeks of pregnancy ewes got 0 . 2 Kg. concentrate d a i l y with 1 1 to 1 2 7 o d i g e s t i b l e crude protein. Results of the t r i a l showed that the ewes given s i l a g e alone or hay with si l a g e produced most o f f s p r i n g . On the whole the b i r t h weight of lambs was lower among ewes given hay alone than for others. Most deaths were among lambs with very low or high b i r t h weight. Weight gain from b i r t h to weaning was usually least with hay alone and concentrates given for 8 instead of 2 weeks improved b i r t h weight of twins only i n the group fed on hay alone. The addition of concentrate to hay or s i l a g e r e s u l t e d i n f u l f i l m e n t of the protein requirements during l a t e pregnancy. Pregnant ewes being fed on pasture alone should be given a supplement during l a t e gestation to meet the requirements of l a t e pregnancy and for better milk production. Pogodin ( 1 9 6 7 ) studied the e f f e c t of l e v e l of n u t r i t i o n of pregnant ewes, during 1 5 0 days of pregnancy fed on pasture alone or with a supple-ment of 0 . 5 Kg. barley meal, on weight changes and milk production. Results showed that the average loss of weight during pregnancy was greatest, 1 7 . 8 7 o i n ewes on pasture alone and least , 1 0 . 0 7 o i n those given barley meal through out. Those given the supplement for the l a s t 1 5 . 3 5 , 7 0 or 1 0 0 days l o s t 9. less weight than those given i t for the corresponding periods at the s t a r t . Average milk y i e l d s during 20 days at the s t a r t of l a c t a t i o n , from the t h i r d day a f t e r lambing when the lambs were removed, were s i g n i f i c a n t l y greater i n ewes given the supplement for the l a s t 15 to 100 days than.those given i t only for the f i r s t 50 days and than those given no supplement during gestation. I t has been shown that lamb b i r t h weights; are not affected by the source of protein i n the feed of t h e i r dams i f the dams are supplied with adequate p r o t e i n l e v e l during gestation. Forbes and Robinson (1967) studied the e f f e c t of source and l e v e l of d ietary p r o t e i n on the performance of ewes a f t e r 10 weeks of gestation. Grass meal was used as a s u b s t i t u t e for fresh grass and. soybean meal repre-senting a more conventional source of p r o t e i n was compared with i t . Both sources of p r o t e i n were included at two l e v e l s , providing a high (90 g. or 0.2 lb./day) and a low (45 g. or 0.1 lb./day) intake of d i g e s t i b l e crude pr o t e i n . The intake of d i g e s t i b l e energy was the same. The l e v e l of feeding adopted was 26.7 g. of d i g e s t i b l e organic matter per kilogram metabolic weight (W^*73)/day. This was equivalent to 100 k. c a l o r i e s of metabolizable energy/kg.(wP*^3) /day where W=live weight i n Kg. The dry matter d i g e s t i b i l i t y was not a f f e c t e d by stage of gestation. The percent dry matter d i g e s t i b i l i t y was 67.7% and 58.2% of intake for the diets contain-ing soybean meal and grass meal, r e s p e c t i v e l y . The differences were s i g n i -f i c a n t . Lower dry matter d i g e s t i b i l i t y i n d i e t s containing grass meal was ! i thought to be due to f i n e m i l l i n g . 'Lamb b i r t h weights were not s i g n i f i c a n t l y a ffected by source or l e v e l of d i e t a r y protein. Ewes weight gaiiis during 10. the l a s t 8 weeks of gestation were s i g n i f i c a n t l y affected by the l e v e l of dietary p r o t e i n . Live weight gains of the ewes were s i g n i f i c a n t l y b e t t e r on higher protein intakes. Source of protein did not have a s i g n i f i c a n t e f f e c t on l i v e weight gain of ewes. The low nitrogen retention rate was associated with lowest mean l i v e weight gain and the highest mean net body weight l o s s . This emphasized the capacity of the ewe to maintain f o e t a l growth during l a t e gestation. Gestation treatments had no e f f e c t on the performance of ewes or lambs during the f i r s t three weeks of l a c t a t i o n . Robinson and Forbes (1967) c a r r i e d out an experiment i n which protein u t i -l i z a t i o n i n the pregnant ewe was studied using the nitrogen balance technique. Eight diets supplying four d i f f e r e n t intakes of crude protein and two d i f f e r -ent intakes of energy were each offered to i n d i v i d u a l l y penned ewes. The 0 73 mean crude protein intakes per day were 7.2,5.5, 4.1 and 3.0 g./Kg.W (W=body weight i n Kg.) and the metabolizable energy intakes 134 and 113 0.73 K. calories/Kg.W * . Nitrogen balance was c a r r i e d out at 10 to 12, 14 to 16 and 18 to 20 weeks of gestation. Results showed that as pregnancy advanced there was a decrease i n the intake of metabolizable energy per unit metabolic body weight. This was due mainly to the f a c t that the intake was based.on the l i v e weights of ewes at s i x weeks of gestation and was not adjusted for increase i n body weight as pregnancy advanced. The decreased intake was more pronounced on the low-protein d i e t s . The weight of food l e f t uneaten expressed as a percentage of t o t a l food offered increased from under 1% on a l l diets at 10 to 12 weeks of gestation to 6.4% on the highest protein d i e t and to 1-3.0% on the lowest protein d i e t j u s t before p a r t u r i t i o n . The intakes of metabolizable energy with the low • protein diets were lower but were adequate. There was a s i g n i f i c a n t reduction 11. i n dry matter d i g e s t i b i l i t y with decreasing protein intake. The decrease was due to an associated decrease i n the numbers of rumen ba c t e r i a ! with low protein d i e t s . There was a s i g n i f i c a n t l y higher dry matter d i g e s t i b i l i t y on the high energy d i e t s . This was due to higher proportion of r e a d i l y fermen-table carbohydrate i n these d i e t s . With the higher energy intake and higher protein intakes the retention of nitrogen (digested) was s i g n i f i c a n t l y i n -creased at a l l stages of gestation. Retention of nitrogen was not aff e c t e d by the number of foetuses c a r r i e d . The mean l e v e l s of nitrogen retained on 0.73 the high and low energy d i e t s were 0.142 and 0.100 g./Kg.'W " re s p e c t i v e l y . The mean increase i n retention of digested nitrogen per K. c a l o r i e increase i n metabolizable energy intake was 2 mg. and varied from 1.3 mg. at 10 to 12 weeks of gestation to 2.5 mg. j u s t before p a r t u r i t i o n . This emphasized the importance of energy intake on nitrogen u t i l i z a t i o n . They suggested that energy intakes higher than -the generally accepted requirement of maintenance plus 25% f o r l a t e pregnancy may have a b e n e f i c i a l e f f e c t on nitrogen retention. The l e v e l s of nitrogen retained at mid pregnancy on intakes of 0.50 and 0.15 g. digested nitrogen/Kg.W^*73 p e r day were s i m i l a r to those obtained for non pregnant ewes on comparable intakes. This indicated that up to mid pregnancy the demand f o r nitrogen i s s i m i l a r to that of non pregnant animals. Nitrogen retention increased with advancing pregnancy and the retentions at 10 to 12, 14. to 16 and 18 to 20 weeks of gestation were 0.086, 0.114 and 0.163 g./Kg. 0.73 ' W " per day, r e s p e c t i v e l y . The increase i n nitrogen retention was accom-panied by a corresponding decrease i n urinary nitrogen output. I t i s c l e a r therefore that increased demand i s met by increased e f f i c i e n c y i n u t i l i z i n g absorbed nitrogen rather than by increased absorption. They suggested that t h i s e f f i c i e n c y with, which the pregnant animal u t i l i z e s digested nitrogen improves as pregnancy advances. The l e v e l s of nitrogen retained at maximum e f f i c i e n c y ( e f f i c i e n c y of u t i l i z a t i o n of digested nitrogen) were 0.235 and 0 73 0.202 g./Kg.W per day for the high and low energy intakes r e s p e c t i v e l y . Robinson and Forbes (1968) studied ewe n u t r i t i o n during l a t e pregnancy and early l a c t a t i o n . During pregnancy the high and low l e v e l s of energy 0 73 used were 150 and 125 K. c a l o r i e s metabolizable energy per Kg.W * per day where W=body weight i n Kg. and represented 150.and 125% res p e c t i v e l y of the maintenance requirement of non pregnant sheep. These l e v e l s were equi-valent to d a i l y intakes of 3270 and 2725 K. calories/150 l b . ewe. The prote i n l e v e l s used were 110, 82, 55, 27 g. or (0.24, 0.18, 0.12, 0.05 lb.) d i g e s t i b l e crude p r o t e i n daily/150 l b . ewe. The two higher l e v e l s of prote i n intake (0.24 and 0.18 lb.) were used i n one experiment and two lower l e v e l s (0.12 and 0.05 lb.) were used i n another experiment. During the f i r s t three weeks of l a c t a t i o n ewes were given a high energy 0 73 die t intended to supply 250 K. c a l o r i e s of metabolizable energy/Kg. W day (5450 K. calories/150 l b . ewe) or a low energy d i e t to supply 175 K. f\ ~7 O c a l o r i e s metabolizable energy/Kg.W (3815 K. calories/150 l b . ewe). Both these d i e t s also supplied a standard d i g e s t i b l e crude p r o t e i n (D.C.P.) intake of 8.8 g./Kg.W0"73' or 192 g. (0.42 lb.)/150 l b . ewe d a i l y . During gestation, r e s u l t s showed that with each energy l e v e l there was a small decrease i n dry matter intake with decreasing p r o t e i n intake. The decrease i n metabolizable energy intake was pronounced on the lower energy d i e t s . I t was 2825 and 2237 K. c a l o r i e s f o r the high and low energy d i e t s , r e s p e c t i v e l y . On each energy intake, crude p r o t e i n intake was 156.5 and 64.5 g/150 l b . ewe per day on the highest and lowest p r o t e i n d i e t s , r e s p e c t i v e l y . The d i f f e r e n c e between the rates of l i v e weight gain on the two energy l e v e l s was about 0.06 Kg./day i n favor of the higher l e v e l . The dif f e r e n c e 13. was s i g n i f i c a n t . There was a s i g n i f i c a n t i n t e r a c t i o n between protein and energy i n d i c a t i n g a difference i n response to protein intake on each energy intake. On the high energy intake there was no s i g n i f i c a n t difference between pr o t e i n l e v e l s (0.24 and 0.18 l b . D.C.P.) i n the f i r s t experiment during pregnancy but there was a s i g n i f i c a n t difference between protein l e v e l s (0.12 and 0.5 l b . D.C.P.) i n the second experiment. There was also a highly s i g n i f i c a n t difference between protein l e v e l s between experiments. There was a highly s i g n i f i c a n t c o r r e l a t i o n between the ewe weight loss at p a r t u r i t i o n and the number of lambs born. Ewes giving b i r t h to twins l o s t an average of 3.2 Kg. more body weight at p a r t u r i t i o n than those giving b i r t h to s i n g l e s . Although the mean weight los s on the lowest protein intake during pregnancy was 0.5 Kg. greater than on the highest protein intake, and the di f f e r e n c e due to energy intake was 1 Kg., these differences were not s i g n i f i c a n t . The net body weight change of the ewes was calculated from the gain i n body weight during the l a s t ten weeks of pregnancy minus the weight loss at p a r t u r i t i o n corrected to twin b i r t h s by covariance. There was a net body weight l o s s on a l l treatments except the two highest protein intakes with the higher energy intake. There was a highly s i g n i f i c a n t difference i n net body weight loss between the high and low energy intakes. There was no s i g n i f i c a n t protein x energy i n t e r a c t i o n s i n the mean b i r t h weights and no s i g n i f i c a n t difference due to energy intake. Although there were no s i g n i f i c a n t differences i n lamb b i r t h weights between protein intakes within experiments, the b i r t h weight of lambs born from ewes on the lower protein intakes were generally lower than those from higher protein intakes (3.98 and 3.51 vs. 4.61 and 4.59 Kg./lamb). As a r e s u l t the combined comparison of protein l e v e l s between experiments was s i g n i f i c a n t . 1 4 . There was a s i g n i f i c a n t c o r r e l a t i o n between the ewe weight change during the f i r s t three weeks of l a c t a t i o n and the number of lambs suckled. Ewes suckling twins l o s t an average 0 . 1 1 Kg. more body weight per day than those suckling s i n g l e s . There was a large v a r i a t i o n between ewes within treatments. There were no s i g n i f i c a n t i n t e r a c t i o n s between protein and energy intakes during pregnancy or between treatments during pregnancy and treatments during l a c t a t i o n . There was no s i g n i f i c a n t difference i n weight loss between the two energy intakes imposed during pregnancy. The mean losses were 0 . 1 5 and 0 . 1 6 Kg./day on high and low l e v e l s , r e s p e c t i v e l y . The difference i n loss of body weight between high and low energy treatments during l a c t a t i o n was not s i g n i f i c a n t . Ewes on the lower l e v e l s of protein intake during pregnancy i n each experiment tended to lose l e s s weight during l a c t a t i o n than those on the higher l e v e l s but the differences were not s i g n i f i c a n t . The diffe r e n c e between combined protein l e v e l s between experiments was s i g n i f i c a n t . Lambs born from ewes on lower protein intakes during pregnancy had on average a slower growth rate ( 0 . 2 6 and 0 . 2 3 versus 0 . 3 1 and 0 . 3 0 Kg./day growth rate f o r lower and higher protein l e v e l s , r e s p e c t i v e l y ) . The difference i n growth rate between protein intakes between the two experiments was s i g n i -f i c a n t . A summary of the re s u l t s indicates that ewe l i v e weight loss during early l a c t a t i o n , lamb growth rates from b i r t h to three weeks and ewe milk y i e l d at 3 weeks tended to decrease with drecreasing protein intake ( 1 5 6 , 1 1 9 , 90 and 65 g. D . C . P . / 1 5 0 l b . ewe daily) during pregnancy. There m s . : no s i g n i f i c a n t difference i n weight loss of ewes between the two energy intakes, imposed during pregnancy. Ewes suckling twins produced a greater amount of milk ( 0 . 6 0 Kg./day more) than those suckling s i n g l e s . There were 15. no s i g n i f i c a n t i n t e r a c t i o n s between protein and energy intakes during pregnancy or between pregnancy x l a c t a t i o n . Further work c a r r i e d out on ewe n u t r i t i o n during l a t e pregnancy and early l a c t a t i o n has indicated that lean ewes have a higher e f f i c i e n c y of food conversion to milk. Peart (1968) studied the e f f e c t s of l i v e weight on the milk production of Blackface ewes. Ewes were i n d i v i d u a l l y fed a p e l l e t e d feed consisting of d r i e d grass meal 66%, maize meal 18%, soybean meal 10%, and molasses 5%, with vitamin and mineral additions. The feed contained 66 g. d i g e s t i b l e organic matter (D.O.M.) per 100 g. as determined i n vivo and i n v i t r o . At s i x weeks ,x pre-partum the f i r s t and second group of ewes were given 14 g. D.O.M./Kg. l i v e weight. The t h i r d group received 9.2 g. D.O.M./Kg. During the l a s t 6 weeks of pregnancy the mean t o t a l d a i l y food intake of ewes i n the f i r s t and second group increased from 912 to 1182 g. D.O.M. and that of t h i r d group increased from 736 to 980 g. D.O.M. Immediately a f t e r p a r t u r i t i o n and throughout l a c t a t i o n feed was rationed to the ewes according to t h e i r i n d i -v i d u a l _p^st^p^r_tum l i v e weights. During l a c t a t i o n the ewes were fed 9.2 g. D.O.M./Kg. based on t h e i r immediate post-partum l i v e weights, plus an allow-ance f o r a predicted l e v e l of milk production. A l l groups of ewes make s i m i l a r l i v e weight gains i n l a t e pregnancy and mean b i r t h weights of the lambs were also s i m i l a r . Ewes i n the f i r s t and second group were fed 0.5 and ewes i n the t h i r d group 0.25 g. D.O.M./g. of predicted milk production. The ra t i o n was increased a f t e r f i r s t and second weeks of l a c t a t i o n , then maintained at a constant l e v e l f o r the remainder of l a c t a t i o n . The mean d a i l y milk produc-tion- of ewes i n f i r s t and t h i r d group was s i m i l a r and the y i e l d of each of these groups was s i g n i f i c a n t l y greater than that of ewes i n the second group. The mean t o t a l milk production of ewes, during 10 weeks of l a c t a t i o n , suckling 16. twin lambs was 127, 108, and 142 Kg. f o r the f i r s t , second and t h i r d group, r e s p e c t i v e l y . The mean l i v e weight changes of ewes i n the f i r s t and t h i r d group were s i m i l a r during l a c t a t i o n . The mean d a i l y l i v e weight gain of twin lambs i n the f i r s t , second and t h i r d group was 279, 275 and 284 g, and of s i n g l e s , 318, 300 and 319 g., r e s p e c t i v e l y . The evidence indicated that ewes i n lean body condition have a higher e f f i c i e n c y of food conversion to milk. There are breed differences iri milk production. Slen, Clark and Hironaka'(1963) made a comparison of milk production and i t s r e l a t i o n to lamb growth i n f i v e breeds of sheep namely Suffolk, Hampshire, Rambouillet,. Canadian Corriedale and Romnelet ewes. Their r e s u l t s indicated that ewes nursing twins y i e l d e d s i g n i f i c a n t l y more milk than those nursing singles and Suffolks y i e l d e d s i g n i f i c a n t l y more than other breeds. Of ewes nursing twins Suffolks and Corriedales y i e l d e d most. Single lambs gained more l i v e weight than twins and those gains were highly correlated with milk consumption. Pr o t e i n and f a t content did not d i f f e r between breeds. I I I . EARLY WEANING AND FEEDING OF LAMBS Clark (1954) stated that early weaning confers great f l e x i b i l i t y in stock management, e s p e c i a l l y i n respect to shearing, pasture u t i l i z a t i o n and weed c o n t r o l . Wardrop (1960) has shown that, at about 8 weeks of age, grazing lambs can digest forage with the e f f i c i e n c y of an adult. This indicated the minimum age at which lambs can be weaned on to pasture. Baird, McCampbell, N e v i l l e , C o i r d i a , Bizzelland S e l l (1960) found that most of the milk production of ewes had ceased by 15 weeks a f t e r lambing and Clark (1961) stated that for ewes nursing twins the milk production of the f i r s t week of l a c t a t i o n was approximately double the production of the eighth week. Dickson (1959) suggested that a f t e r two months of age, grass becomes the dominant factor in the lamb's feed. This also indicates that lambs can be weaned e a s i l y at 8 weeks of age but some workers have shown that early weaned lambs do not gain as much, when weaned on to pasture, as unweaned lambs. D i f f e r e n t responses to early weaning have been reported. Stage of maturity of the pasture i s an important factor for early weaning. Many workers have pointed out that lambs weaned at 8 to 10 weeks of age should have at least 12 to 14% crude protein i n t h e i r feed during f i r s t 3-4 weeks aft e r weaning. Baird e_t al_ (1960) weaned lambs at an average age of 76 days and an average weight of 45 l b . , on to winter temporary pastures of wheat and rye grass. E a r l y weaning d i d not stimulate forage consumption of lambs. Average d a i l y gain for unweaned and weaned lambs was 0.57 and 0.51 l b . , r e s p e c t i v e l y . So early weaned lambs made slower gains than the unweaned controls i n t h i s experiment. They also stated that early weaned lambs had 46% less worms 1 8 . at slaughter than the lambs weaned l a t e r (764 vs. 1407). Brothers and Whiteman (1961) studied the influence of early weaning on creep-fed milk lambs when weaned on weight or age b a s i s . A l l lambs and t h e i r dams;: were on wheat pasture and the lambs were creep-fed. In the f i r s t year the average weight of lambs at weaning was 54 l b s . and average weaning age was 76 days. The weaned lambs made an average d a i l y gain from weaning to market weight (90 lb.) of 0.52 l b . and lambs not weaned gained 0.54 lb./day. This difference was not s i g n i f i c a n t . In another experiment during the following year the average weight of lambs at weaning was 46 l b . and average weaning age was 62 days. The weaned lambs gained 0.47 l b . and the lambs not weaned, 0.52 lb./day. This dif f e r e n c e was s i g n i f i c a n t . This showed that e a r l y weaned lambs (about 9 weeks old) made slower gains than la t e weaned (about 11 weeks old) lambs. Cannon (1960) stated that fat lambs weaned at eight weeks of age may average a minimum of 2.5 l b . less in carcass weight than suckling lambs when both types have been under extremely good n u t r i t i o n a l conditions. Under such conditions grading was not affected by weaning. Wardrop (1960) reported that lambs weaned at 7, 10, 13 or 18 weeks of age and grazing high protein pastures grew equally well and there were no s i g n i f i c a n t differences between t h e i r carcass weights, grades and dressing percentages. However, when grazing pastures i n the pre-' flowering and flowering stages of growth, lambs weaned at 8 weeks of age did not grow as well as unweaned controls. Their carcass weights were also lower and i t was suggested that the differences were primarily due to an inadequate protein. They stated that stage of maturity of the pasture i s very important factor for early weaning. They pointed out that the milk intake of the 10-week old grazing lamb i s about 1.6 lb./day which i s equivalent to 2.3 l b . of S.E. (starch equivalent) and 0.6 l b . of d i g e s t i b l e crude protein (D.C.P.) 19. per week. Therefore i f a lamb i s weaned at 10 weeks of age and i s to gain as f a s t as unweaned lambs i t must obtain these a d d i t i o n a l amounts of S.E.' and D.C.P. from the pasture. Only about 22 lb./week of fresh young grass are required but at l e a s t twice as much w i l l be needed when the herbage i s i n the flowering stage. This large increase i n the a d d i t i o n a l herbage require-ment i s occasioned by the rapid decline i n pasture protein content. As the pasture intake of the lamb i s l i m i t e d , so when the lamb i s grazing a mature pasture i t i s impossible for the lamb to ingest enough herbage to meet i t s protein requirements and adequate energy to sustain s a t i s f a c t o r y growth. Cameron and Hamilton (1961) found that lambs weaned at 10 weeks of age had a lower dressing percentage than those weaned at 15 or 20 weeks of age. How-ever, age at weaning had no s i g n i f i c a n t e f f e c t on carcass scores. They also found the s i n g l e lambs heavier at market and having lower dressing percentage than twins. The lower dressing percentage f or s i n g l e lambs was associated with a younger average age at slaughter and s i g n i f i c a n t l y lower carcass score f or f i n i s h , and lower average scores for a l l other carcass character-i s t i c s than those f o r twin lambs. They pointed out that lambs weaned at 10 weeks of age made more rapid average gains i i i the f i r s t two weeks following than during the remainder of the study, i n d i c a t i n g that rumen function was developed s u f f i c i e n t l y f o r the dig e s t i o n of immature forage. They further stated that age at weaning had no e f f e c t on death losses. 1 Single lambs made fa s t e r gains than twins and wethers made more rapid gains than ewes. Fra n k l i n Q.965) weaned merino lambs at d i f f e r e n t ages on to a mixture of roughage and grain. Results showed that loss of lambs weaned at four weeks of age was s i g n i f i c a n t l y greater than i n those weaned at 6, 8, or 12 weeks and lambs which survived were s i g n i f i c a n t l y heavier at b i r t h and at weaning. Li v e weight at 22 weeks of age was not s i g n i f i c a n t l y affected by age at wean-ing. F i e l d observations, showed that lambs between 8 and 16 weeks- of age could 20. be weaned successfully under drought conditions on the roughage and concentrate provided they were closely confined until accustomed to their rations. Garrigus (1951) concluded that relatively simple creep rations were as effective in promoting rapid gains in early weaned lambs as more complicated grain mixes. Perry, Beeson, and Harper (1957) studied the value of fortified creep rations for single and twin suckling lambs. The creep ration containing 17$ crude protein was available from the third day of lamb's l i f e . Single lambs receiving creep pellets containing corn, soybean meal, salt, bone meal and vitamin 1,D"and"E grew as rapidly as lambs fed similar pellets but fortified with 10% sugar, B vitamins, ascorbic acid and trace minerals (super pellets). Twins which had access to "super pellets" grew as rapidly as single lambs not on "super pellets". Growth of twins was not as rapid as that of single lambs when both received "super pellets." Hinds, Mansfield and Lewis (1963) indicated' that the most rapid gains were obtained with lambs weaned at 10 weeks of age and receiving 12 percent protein. Ranhotra and Jordan (1966) conducted experiments to determine the optimum level of protein for lambs weaned at 6 to 8 weeks of age and to determine the energy requirements of such lambs as measured by digestion trials and growth studies. Their results revealed that apparent digesti-bility of both protein and energy were increased significantly due to increased protein and energy content of the ration. Protein content of the ration was without significant effect upon rate of gain or efficiency of feed conversion, when measured on the basis of either 8 or 9-week feeding periods. However, rations containing between 12 and 1L% protein resulted in 21. more rapid gains during the f i r s t 28 days following weaning than rations with lower protein l e v e l s . Rations containing 16.5 to 16.7% protein did not support more rapid or more e f f i c i e n t gains than rations containing 13.5 to 14% pr o t e i n . They further indicated that rations based on 75:25 concentrate to roughage r a t i o supported s i g n i f i c a n t l y greater and more e f f i c i e n t gains of lambs weaned at 7 weeks of age during the f i r s t 4 weeks than did rations based on a 55:45 concentrate to roughage r a t i o . Over the 8 week period gains were greater with the higher concentrate r a t i o n than with the lower concen-t r a t e r a t i o n . However, these differences were not s i g n i f i c a n t . Light (1966) indicated i n a free choice of d i f f e r e n t feeding s t u f f s that r o l l e d barley and oats were more r e a d i l y accepted than cracked maize by the lambs weaned at 5 weeks of age. He also stated that lambs selected a r a t i o n with 21% pr o t e i n . Coetzee and Vermeulen (1966) fed merino lambs, 10 weeks before and 6 weeks a f t e r weaning, creep feeds with 9, 15 or 20% crude pr o t e i n . Results pointed out that weight gain of creep-fed lambs was s i g n i f i c a n t l y greater than for the control group. A f t e r weaning gain of groups given 15 or 20% protein was s i g n i f i c a n t l y greater than those given 9% protein but r e s u l t s suggested that 9% protein before weaning and 15% protein afterwards would give best performance. Heated soybean meal has been used to cause greater nitrogen retention by many workers. Glimp, Karr, L i t t l e , Woolfolk, M i t c h e l l , J r . and Hudson (1967) reported that reduced protein s o l u b i l i t y resulted i n increased nitrogen retention and decreased ruminal degradation of feed p r o t e i n i n lambs. Hudson et a l . (1969) also experimented to determine the e f f e c t s of reducing protein s o l u -b i l i t y from 72 to 35% by dry heat and the e f f e c t of feeding three l e v e l s of 10, 12 and 14%, crude protein on rate and e f f i c i e n c y of gain and n u t r i e n t u t i l i z a t i o n of early weaned lambs. Results showed that growth rate was highest at the 14% protein l e v e l . Heating the soybean meal had an i n -consistent e f f e c t and feed e f f i c i e n c y was improved s i g n i f i c a n t l y . Results also showed that rumen ammonia concentrations increased with protein l e v e l and showed a s l i g h t depression due to heating the soybean meal. The bene-f i c i a l e f f e c t of proper treatment i s the r e s u l t of greater destruction of several thermo-labile growth impairing factors than of soya p r o t e i n i t s e l f . Fisher and Johnson (1958) a t t r i b u t e d the poor growth of animals on d i e t s containing raw soybean meal to an i n h i b i t i o n of i n t e s t i n a l p r o t e o l y s i s , haemagglutinin a c t i v i t y of some component of the beans and an inbalance of dietary amino acids. From the references given above i t i s c l e a r that lambs should have at l e a s t 12 to 14% crude protein i n t h e i r r a t i o n during the f i r s t few weeks, when weaned at 8 to 10 weeks of age and further that feeding the heated soybean meal by reducing i t s s o l u b i l i t y from 72 to 35% r e s u l t s i n greater nitrogen retention. 23. IV. UREA-NUTRITIONAL IMPORTANCE AS A NON-PROTEIN NITROGEN SOURCE The f i r s t purpose of adding non-protein nitrogen compounds to the r a t i o n of ruminants i s to supply nitrogen which can be incorporated into protein by the microbial population of the rumen or to provide other nitrogen containing molecules which can be used by the rumen micr o f l o r a . The basis of t h i s mechanism i s the r e a c t i o n : -Non-protein nitrogen-»microbial protein nitrogen Harris (1940) was one of the f i r s t to t e s t the theory that non-protein nitrogen could be used by rumen microorganisms to form protein useful to the host animal. He reported that lambs gained weight when they were kept on a low-protein, semipurified d i e t made up of starch, a l k a l i washed straw, inorganic s a l t s and urea. Wegner, Booth, Bohstedt and Hart (1940) were among the f i r s t to f i n d that the l e v e l of protein i n the r a t i o n influenced the conversion of non-protein nitrogen to protein and to f i n d that as the l e v e l of p r o t e i n i n the r a t i o n was increased, the amount and rate of conversion of urea to protein decreased. To discuss the above mentioned topic and the usefulness of urea as a NPN (non-protein nitrogen) source i t i s necessary to discuss b r i e f l y the fate of protein and urea. Annison (1956) stated that the amino acids produced by the hydrolysis of dietary protein are r a p i d l y deaminated by the ruminal b a c t e r i a . The rate of deamination i s only s l i g h t l y less than that of t h e i r production, so that the l e v e l of free amino acids i n rumen i s low (of the order of 1 mg. amino N per 100 ml ruminal f l u i d ) , except a f t e r feeding a p r o t e i n - r i c h r a t i o n , when i t may increase f i v e f o l d Co t e n f o l d for a short period. Blackburn (1965) indicated that the end products of i n d i v i d u a l amino acids i n most cases are ammonia, carbon dioxide and v o l a t i l e f a t t y acids. Abou Akkada and Blackburn (1963) have shown that l e s s e r amounts of ammonia 24. are also produced i n the rumen by the action of ami dases on glutamine and asparagine and the ami de groups of proteins. The production of ammonia from the above sources can r e s u l t i n very high l e v e l s i n the rumen, f o r example, Johns (1955) has reported upto 130 mg. ammonia nitrogen per 100 ml. of ruminal f l u i d i n sheep on high protein pastures but t h i s i s much higher than the ammonia l e v e l normally found i n the rumen when urea or other forms of supplementary N.P.N, are fed under p r a c t i c a l conditions. Endogenous urea enters the rumen with the s a l i v a and through the ruminal w a l l . In sheep, McDonald (1948) estimated that 0.5 g. urea N per day i s introduced i n t o the rumen with the s a l i v a . Houpt (1959) reported that 16 times as much urea passed d i r e c t l y from blood to rumen as moved with the s a l i v a but i n t h i s case the animal was not fed urea and the concentration of urea was greater i n the blood than i n the rumen so more urea passed from the blood to the rumen then was recycled with the §aliva Urea i s broken down very r a p i d l y to ammonia and carbon dioxide by the ureases of ruminal b a c t e r i a so that the urea l e v e l i n the rumen i s n e g l i g i b l e . The r e s u l t of the secretion and hydrolysis of endogenous urea i s that the animal i s able to maintain a low but s i g n i f i c a n t concentration of ammonia i n the rumen, even when i t i s starved. When urea i s given as a supplementary source of nitrogen, i t shares the fate of endogenous urea i n the rumen. The urease a c t i v i t y of the ruminal b a c t e r i a of animals on unsupplemented rations i s s u f f i c i e n t l y high to b r i n g about the breakdown of large amounts of added urea within a short time, and l i t t l e or no increase i n a c t i v i t y occurs when the animals are conditioned to being fed urea for long periods. Repp, Hale, Cheng and Burroughs (1955) stated that the entrance of large quantities of urea into the rumen i n starved or fasted animals or by rapid consumption of feeds containing urea by animals not previously fed such r a t i o n s , r e s u l t s i n the release of ammonia at a rate which does not 25. permit ef f i c i e n t u t i l i z a t i o n of nitrogen by the rumen micro-organisms for the synthesis of cellular protein. The hydrolysis of urea i n the rumen i s unrelated to the a b i l i t y of micro-organisms to u t i l i z e ammonia produced. Ammonia not u t i l i z e d by the rumen microflora i s rapidly absorbed into the bloodstream where i t may reach toxic levels. These workers further indicated that toxic symptoms appear i n sheep when bloodaamonia nitrogen level rises above 1 mg. %, Warren (1962) pointed out that the rate of ammonia transfer across the rumen wall not only depends on the concentration gradient but also on pH of the rumen liquor. He stated that ammonia i s most toxic i n conditions where the pH of the rumen liquor i s higher than 7.5, when unionized NH^  i s formed and most membranes are more permeable to the NH^  moiety than the ammonium ion (NH^+ ). Kammlade, Mitchell and Sleeter (1940) as cited by Briggs (1967) stated that up to one-third of the nitrogen i n a sheep ration could be safely replaced by urea. They also stated that the rate of conversion of urea into bacterial protein decreased as the total protein, excluding non-protein nitrogen, of the ration increased above 12% of dry matter. .They also showed that the urea above 12% protein level was not retained as ef f i c i e n t l y as casein and other protein sources, and that urea i n the ruminant ration exerted no adverse effect on flavor and non-protein nitrogen content of meat and milk. Although the use of urea as a protein substitute i n ruminant nutrition has become f a i r l y common i n North America, i t s use as the major or sole source of nitrogen i s limited due to danger of ammonia toxicity. 26. The adverse effects of urea may be eliminated partially through the use of more slowly hydrolyzed, less toxic non-protein nitrogen compounds. Biuret is a compound of interest. It was shown by Repp e_t al (1955) to be less toxic than urea. However Anderson, McLaren, Welch, Campbell and Smith (1959) stated that when pure biuret supplied 100% of the supplemental nitrogen instead of urea, nitrogen utilization was significantly depressed. They also stated that nitrogen digestibility was greater when purified soy-bean protein or a nitrogen equivalent mixture of urea and creatine replaced urea as the source of supplemental nitrogen. - In order to compare urea with other non-protein nitrogen sources Schaadt, Johnson and McClure (1966) investigated adaptation to urea, biuret and diammonium phosphate as non-protein nitrogen sources for sheep. The crude protein content of control and supplemented rations was 6.5 and 10.2% respectively on a dry matter basis. The results showed that percent diges-ti b i l i t y of nitrogen in the control animals, fed on chopped wheat straw, chopped timothy hay, ground shelled corn and corn starch, and given no supplementary non-protein nitrogen, was significantly lower than in any other group and in the group given urea i t was significantly higher than in a l l groups except that given urea with diammonium phosphate. Nitrogen balance was greatest with no supplement or with urea and diammonium phosphate. They also reported that as the t r i a l progressed there was an increase in nitrogen balance in the group given urea but not in other groups. It showed that rumen microorganisms became better adapted to feeding of urea for the synthesis of microbial protein as the t r i a l progressed but the biuret supplemented lambs failed to show the evidence of adaptation in nitrogen balance but they did show adaptation in the urinary biuret excreted because biuret excreted by the group given i t decreased during 27. the t r i a l . Schaadt e_t a l (1966) also studied the p a l a t a b i l i t y of four rations supplemented equally on a nitrogen basis with soybean meal (SBM), urea, diammonian phosphate (DAP) and diammonium phosphate + urea. Lambs used were previously adapted to the basal, urea or ADP + urea r a t i o n s . The design of the t r i a l was such that each lamb was exposed for a one week period to each possible combination of two supplemental feeds but to only two i n any one period. Animals ate ad-libitum and p a l a t a b i l i t y of the r a t i o n was c a l c u l a t e d by the amount of each r a t i o n eaten over a s i x week period. Results showed that the d a i l y intake f o r SBET or urea was 0.75 and 2.77 kg; for SBM or DAP, 1.14 and 0.40 kg; f o r SBM or DAP + urea, 1.06 and 0.52 kg; f o r urea or DAP, 1.19 and 0.26 kg, for urea or DAP + urea, 1.16 and 0.35 kg and f o r DAP + urea or DAP, 1.18 and 0.21 kg r e s p e c t i v e l y . Results revealed that both urea and soybean meal supplemented rations were equally preferred over diammonium phosphate (DAP) or DAP + Urea. Diammonium phosphate plus urea was preferred over diammonium phosphate. In a l l periods, diammonium phosphate was very unpalatable. Some workers have compared urea with melamine. Cronje and Coetzee (1966) determined the retention of nitrogen i n sheep given a control feed based on p e l l e t e d dried T. triandragrass. The sheep were i n negative nitrogen balance when rec e i v i n g t h i s grass. They were given 4.7 g. nitrogen d a i l y by stomach tube. This nitrogen was provided by 10 gi . urea or 7 gii. melamine d a i l y . The animals reverted to a p o s i t i v e balance when dosed with non-protein nitrogen. A s i g n i f i c a n t l y l a r g e r amount of nitrogen was excreted: i n the case of melamine and urea than i n the control animals. This ind i c a t e d that a considerable amount of nitrogen from these substances wasnot properly u t i l i z e d by sheep and excreted through the urine. The s i g n i f i c a n t l y higher nitrogen content of the 28. faeces of sheep receiving melamine indicated that part of melamine nitrogen was excreted through the faeces. Urea nitrogen, on the other hand, was not excreted i n the faeces. This i s i l l u s t r a t e d by the f a c t that faeces i n the urea group contained no more nitrogen than that of the c o n t r o l group. A l -though average nitrogen retention for urea was higher than for melamine, the d i f f e r e n c e was not s t a t i s t i c a l l y s i g n i f i c a n t . Daily retention of n i t r o -gen for urea, melamine and controls was +.50g., +0.94g. and -0.87g. Non protein nitrogen i n blood as urea nitrogen was not affected by melamine but i t increased s i g n i f i c a n t l y for eight hours a f t e r urea had been given. Adaptation of the animal i s important while feeding urea to avoid toxicity^;, - The l e v e l of r e a d i l y fermentable carbohydrate also has an e f f e c t on the l e v e l of absorbed nitrogen. Szabo (1965) stated that for wethers the amount of urea per head per day could be gradually increased from 15 to 40g. without the r i s k of poisoning but the increase must be gradual taking at least 30 days to reach the maximum. McLaren, Anderson, Tsai and Barth (1965) examined the influence of length of time of urea feeding and l e v e l of r e a d i l y fermentable carbohy-drates on the retention of absorbed nitrogen. Results showed that the retention of absorbed nitrogen by lambs, with i n i t i a l retention of 367„, was s i g n i f i c a n t l y improved by 3 percentage units with each 10 day period of urea feeding up to 45 days. During the l a s t 10 days the retention was constant. The retention of absorbed nitrogen was s i g n i f i c a n t l y improved by 2 percentage units for each 100 K. c a l o r i e s increase of r e a d i l y ferment-able carbohydrates i n the r a t i o n of the lambs. The intake of r e a d i l y fermentable carbohydrates ranged from 564 to 1178 K. calories/day. Average d a i l y dry matter intake was 725g. Improvement i n the retention of absorbed nitrogen due to the l e v e l of r e a d i l y fermentable carbohydrates was observed i n lambs regardless of the degree of the i r adaptation to urea feeding. Addition of r e a d i l y fermentable carbohydrate decreased the crude f i b e r d i g e s t i b i l i t y . When 5 6 4 K . calories/day of r e a d i l y fermentable carbohydrates were fed to 5 lambs the average crude f i b e r d i g e s t i b i l i t y was 4 5 . 6 7 o . When the l e v e l of r e a d i l y fermentable carbohydrate was increased to 1 1 7 3 K . c a l o r i e s for 5 lambs the average d i g e s t i b i l i t y of crude f i b e r was 4 3 . 2 7 » . McLaren e_t a_l ( 1 9 6 5 ) stated that sugars disappear too quickly from the rumen while c e l l u l o s e becomes a v a i l a b l e too slowly to s a t i s f y the energy needs of microorganisms. A mixture of r e a d i l y a v a i l a b l e and the more complex slowly a v a i l a b l e carbohydrates seems s a t i s f a c t o r y . When glucose or starch i s added, the uptake of ammonia by the microorganisms i s much more ra p i d than when roughage alone i s present. I t i s th i s which makes the addi t i o n of r e a d i l y fermentable carbohydrate desirable when non-protein nitrogen supplements are fed i n a form i n which large amounts of ammonia are r a p i d l y produced i n the rumen. By increasing the rate of u t i l i z a t i o n of ammonia so that i t more nearly matches the rate of forma-ti o n , the carbohydrate reduces the concentration of ammonia i n the ruminal f l u i d and so decreases the amount l o s t from the rumen and lessens the danger of toxicity/, to the animal. Some workers have fed urea as salt/urea blocks. Beames and Morris ( 1 9 6 5 ) studied the e f f e c t of salt/urea blocks on body-weight, body compos ti o n and wool production of merino wethers fed to appetite on low-protein pasture grass hay with a crude protein content of 3 . 5 7 o . The r e s u l t s indicated that the c o n t r o l group which did not have access to urea blocks 30. l o s t 20% of t h e i r i n i t i a l body weight, during the t r i a l . Groups given s a l t blocks containing 20% urea plus molasses l o s t 10% of t h e i r i n i t i a l body weight. Those given blocks containing 20% urea and no molasses l o s t 12% of t h e i r i n i t i a l body weight showing that r e a d i l y soluble sugars improve the u t i l i z a t i o n of urea. I t shows that molasses serves as a source of energy for the microorganisms and causes slow intake because of i t s s t i c k y syrupiness. Results also indicated that voluntary intake of hay and out-put of dry matter infaeces were increased by urea and weight of clean soured wool was greater but not s i g n i f i c a n t l y i n groups given urea. From comparative slaughter, energy reserves of the bodies of sheep given hay only were depleted to a greater extent than was indicated by body weight changes. Urea increases the net energy value of high f i b e r mixtures i n ruminant ra t i o n s . Colovos, Keener, Davis, Reddy and Reddy (1963) confirmed the above statement. They fed cows on two concentrate mixtures e i t h e r with a low l e v e l of f i b e r containing 5% f i b e r or a high f i b e r mixture containing 10% f i b e r along with early cut hay. These mixtures were fed alone or with a concentrate mixture containing 40 pounds/ton of urea.and supplying 35% of the protein of the concentrate mixture. Results showed that net energy values f o r low f i b e r and high f i b e r rations without the addition of urea were 1.739 and 1.507 K. c a l o r i e s per g. r e s p e c t i v e l y . When urea was added to these rations the respective values were 1.806 and 1.752 K. c a l o r i e s per g. There were no s i g n i f i c a n t differences i n net energy values obtained with or without the addition of urea. I t showed that a f t e r the addition of urea the r a t i o n containing high f i b e r was comparable to the one containing low f i b e r . It was thought to be due to a decrease i n the heat increment where urea was added i n the r a t i o n . Oestrogens have been shown to increase the urea nitrogen retention. B e l l , Taylor and Murphree (1957) investigated the e f f e c t s of d i e t h y l s t i l b e s t r o l on d i g e s t i b i l i t y and nutrient retention of a corn-urea mixture containing 13.57=, crude pro t e i n . This r a t i o n was fed to lambs at the l e v e l of 1.25 pounds per head d a i l y alone or with 4 mg. d i e t h y l s t i l b e s t r o l per head per day. Results showed that d i e t h y l s t i l b e s t r o l feeding had no s i g n i f i c a n t e f f e c t on the d i g e s t i b i l i t y of crude protein or other nutrients but feeding of d i e t h y l s t i l b e s t r o l s i g n i f i c a n t l y increased the d a i l y nitrogen retention and i t was 4.9g. and 3.3g. d a i l y for d i e t h y l s t i l b e s t r o l + urea and urea alone, r e s p e c t i v e l y . This increased retention of nitrogen was found to be due to a decrease i n the amount of nitrogen excreted i n the urine. D i e t h y l s t i l b e s t r o l feeding s i g n i f i c a n t l y increased phosphorus retention which increased from 0.3 to 1.3g. during the 7 days. I t was thought to be due to decreased excretion of phosphorus i n the faeces. Urea had no e f f e c t on the retention of either calcium or phosphorus. Karr, Garrigus, H a t f i e l d and Norton (1965) showed that lambs implanted with 3 mg. d i e t h y l s t i l b e s t r o l each i n t h e i r ear and fed on a r a t i o n contain-ing 1.57» urea with 13.17» crude p r o t e i n gained faster than the unimplanted lambs. There were no s i g n i f i c a n t d ifferences i n d a i l y feed intake. Lambs on r a t i o n with urea and implanted with the hormone gained 15 pounds i n 21 days with i n i t i a l weight of 60 pounds but i t took 54 days to gain the same weight by the lambs not implanted with d i e t h y l s t i l b e s t r o l and fed on r a t i o n with urea. This was thought to be due to increased nitrogen retention and d i e t h y l s t i l b e s t r o l also markedly reduced the adaptation period of lambs receiving urea nitrogen. 32. Some workers have investigated the r e l a t i o n s h i p of sulphur and urea. Thomas, L o o s l i , Williams and Maynard ( 1 9 5 1 ) stated that an adequate supply of sulphur i s required for incorporation of ammonia into methionine and cysteine. They fed lambs on p u r i f i e d d i e t s containing 4 7 « urea and sulphur as MgS0^(204g.) and MnS0^(3g.) or urea without sulphur. Their r e s u l t s showed that lambs did not eat p u r i f i e d d i e t s r e a d i l y and they a l l l o s t weight during the f i r s t 60 days of the t r i a l . Thereafter those fed urea + sulphate increased i n body weight and t h e i r average d a i l y gain was 34g. while those on sulphur d e f i c i e n t feed continued to lose weight and t h e i r d a i l y loss was 70g. Noble, Pope and Gallup ( 1 9 5 5 ) reported that methionine and urea added separately to a low protein ( 8 . 4 7 , crude protein) basal r a t i o n for fattening lambs f a i l e d to improve the rate of gain but when added i n combination they increased the d a i l y gain i n each t r i a l but the increases were not s t a t i s t i -c a l l y s i g n i f i c a n t . They further stated that soybean meal as a supplement to the basal r a t i o n c onsistently improved rate of gain and feed e f f i c i e n c y . Poor performance of lambs given urea alone to the basal r a t i o n was p a r t l y due to the deficiency of sulphur i n the basal r a t i o n which had a sulphur content of 0.1%. The nitrogen: sulphur r a t i o of the nitrogen supplements i n the urea r a t i o n was narrowed from 5 9 : 1 to 1 5 : 1 by the a d d i t i o n of methionine. This factor contributed to the improved d a i l y gain. Light, Dinusson, Richard and B o l i n ( 1 9 5 7 ) showed that soybean meal was a s i g n i f i c a n t l y better p r o t e i n supplement for lambs than urea when urea was fed at the rate of three percent of the concentrate mixture and supplying 4 1 7 o of nitrogen i n the r a t i o n , with poor q u a l i t y non-legume hay fed ad-libitum. 33. Soybean meal i s a better source of nitrogen than urea. D r o r i and L o o s l i (1961) conducted experiments with'sheep and showed that the d i e t with soybean meal gave better nitrogen retention and had a higher bio-l o g i c a l value than d i e t s with urea. This f i n d i n g was thought to be re l a t e d to the excretion of urea i n the urine. They also showed that urea nitrogen i n blood rose a f t e r d i e t s with urea and f e l l a f t e r d i e t s with soybean meal but the differences were not s i g n i f i c a n t . They further stated that blood urea l e v e l s i n t h i s study were not constant and the average l e v e l s of blood urea gave no clue to the value of protein i n the feed. They gave the reason that the data i n their experiment was not paired. They further showed that urea produced a sharp r i s e i n rumen ammonia only when given r a p i d l y through the f i s t u l a . Preston, Schnakenberg and Pfander (1965) conducted experiments to fi n d the e f f e c t of protein intake on blood urea nitrogen i n lambs fed to appetite on f i n i s h i n g r a t i o n s consisting of soybean meal and corn with d i f f e r e n t crude p r o t e i n contents (9.2, 11.5, 13.1, 16.5 and 22.0%). Results indicated that the d a i l y gain, feed intake, urea nitrogen i n blood and d i g e s t i b i l i t i e s of energy and protein increased when there was more protein i n the feed and e f f i c i e n c y of feed conversion improved a l s o . The r e s u l t s also showed that the v a r i a t i o n i n the pr o t e i n intake of the growing lamb re s u l t e d i n blood urea nitrogen (BUN) ranging from 2.7 to 3.29 S.mg./100 ml. They stated that the protein status of the lamb can be assessed p a r t i a l l y by the concentration of th i s blood constituent. In terms of protein adequacy a BUN value i n excess of lOmg./lOO ml. would in d i c a t e adequate protein intake with the type of rat i o n s fed i n these experiments. In another experiment urea was used as a supplemental source of nitrogen (47%, of t o t a l nitrogen) for lambs. They consumed 16g. protein/ . 34. W ° * ^ where W=live weight i n pounds. Their average BUN was 27.3 mg./lOO ml. This BUN i s higher than the l e v e l obtained with soybean meal and corn. They r e l a t e d t h i s to a lower b i o l o g i c a l value of urea, when fed at t h i s l e v e l . O livierand Cronje (1964) studied the e f f e c t of the rate of intake of urea upon the nitrogen retention of sheep. Special urea-containing p i l l s which released the urea gradually over a 24 hour period were developed. One group received a dose of 8 g. urea d a i l y , the other group received the p i l l containing 8 g. urea while the t h i r d group received no urea. The non-protein nitrogen content of the blood of sheep was determined 1.5, 3.5 and 8 hours a f t e r dosing. The group which received the urea i n p i l l form retained s i g n i f i c a n t l y more nitrogen than the group which received one normal dose of urea d a i l y . Urea supplementation had no e f f e c t on crude f i b e r digestion. Many workers have investigated the e f f e c t s of duodenally infused urea. Egan (1965) conducted various experiments to f i n d the fate of duo-denally infused casein (71 g.) and urea (22 g.) providing 10 g. of nitrogen i n sheep fed on oaten hay (including seeds), molasses and minerals contain-ing 9% crude protein. Results showed that the urea i n the blood and ammonia nitrogen i n rumen were increased by duodenally infused urea and casein. Both sources of nitrogen increased the rate of d i g e s t i o n of c e l l -lose (cotton thread) and the peak was reached e a r l i e r a f t e r urea than a f t e r casein., Peak values f o r both occured between the end of i n f u s i o n and s i x hours l a t e r . Of the nitrogen supd-ied by these sources more nitrogen was excreted i n the urine a f t e r urea than a f t e r casein. Results of t h i s i n v e s t i g a t i o n c l e a r l y demonstrated the return of nitrogen to rumen a f t e r i n f u s i o n per duodenum of s i n g l e doses of either casein or urea as both 35. ruminal ammonia nitrogen concentrations and the rate of c e l l u l o s e diges-t i o n (cotton thread) i n the rumen were increased. Return of nitrogen to the rumen a f t e r absorption rather than by back-flow from the duodenum through both abomasum and omasum was suggested by the following observa-t i o n s . 1) Maximum ruminal ammonia nitrogen concentrations were much lower when casein was given than when urea was given. 2) Ruminal ammonia nitrogen concentrations did not r i s e u n t i l a f t e r completion of the i n f u s i o n of casein. 3) The time and magnitude of ruminal ammonia nitrogen changes r e f l e c t e d the time and magnitude of changes i n blood urea nitrogen concentration. The blood urea nitrogen l e v e l increased r a p i d l y as urea was infused. A less rapid increase i n the blood urea nitrogen l e v e l was recorded when casein was given. A f t e r i n f u s i o n of casein neither the blood urea nitrogen l e v e l nor the ruminal ammonia nitrogen concentration were r a i s e d to the same extent as when urea was given which suggested that less nitrogen was returned to rumen a f t e r casein i n f u s i o n . Egan and Moir (1965) investigated the e f f e c t s of duodenally infused si n g l e doses of casein and urea (4.5g.N/day)on voluntary intake of a low-prot e i n roughage by sheep. Results showed that the casein and urea gave s i g n i f i c a n t but transient increases i n voluntary intake of feed, casein on the day i t was given and urea on the day a f t e r . Egan (1965) conducted another experiment to f i n d the influence of sustained duodenal infusions of casein or urea upon voluntary intake of low-protein roughages by sheep. The r e s u l t s revealed that with urea the mean d a i l y intake of dry matter was 12% and with casein 42%, greater than 36. that observed with the control group. It showed that when nitrogen balance was improved and the amount of amino acids absorbed was increased, the intake of dry matter increased, Results also showed that the apparent digestibility of dry matter was decreased consistently though not significantly by casein but urea had no consistent effect. The depressed digestibility of dry matter in case of casein was due to greater dry matter intake. It was also shown that the volume of rumen fluid was significantly increased by casein but urea had no effect. Nitrogen balance results showed that i t was negative in controls but became positive with either casein or urea. Nitrogen content of faeces was not affected but urea though consistently but not significantly increased excretion of nitrogen in the urine. V. EFFECT OF FEED UREA ON MILK YIELD AND MILK COMPOSITION Ef f e c t On Milk Production The problem of replacing proteins, as the main natural sourceof nitrogen i n feeding milk-producing ruminants, by the a d d i t i o n of urea to the feed of these animals, i s of i n t e r e s t not only from s c i e n t i f i c but also from the economic point of view. This i s because nitrogen i s much cheaper i f supplied i n the form of urea, while proteins are among the most expensive constituents of conventional r a t i o n s . The cost of milk production would be considerably lower i f at least some part of the neces-sary proteins could be replaced by a cheaper synthetic product l i k e urea. Urea and other non-protein compounds have been shown to be u t i l i z e d i n milk production. Schoenemann ( 1 9 4 6 ) and K i l i a n ( 1 9 4 8 ) c i t e d by Briggs ( 1 9 6 7 ) f i r s t pointed out that urea l a b e l l e d with N"*""* added to the feedstuff became a component of milk i n goats. Land and Virtanen ( 1 9 5 9 ) c i t e d by Briggs ( 1 9 6 7 ) used N ^ i n the form of ammonium s a l t s and found that 1 7 to 2 5 7 o of t h i s nitrogen appeared i n milk. They showed that the process of incorporation of l a b e l l e d ammonium nitrogen i s most intensive 1 4 hours a f t e r feeding, and a f f e c t s the amine nitrogen f r a c t i o n s of such amino acids as glutamic acid, asparagine and alanine. They further showed that after 2 4 hours the amino acids i n the milk protein are already more uniformly l a b e l l e d , except for h i s t i d i n e and cystine, which show a comparatively low percentage 1 5 of N . They also calculated that on the whole about 4 0 7 o of the l a b e l l e d nitrogen supplied i s taken up by the t i s s u e p r o t e i n . The e f f e c t of feed urea on milk production and milk composition has been mostly investigated i n dairy cows and l i t t l e work has been c a r r i e d out i n the case of sheep. 38. Rust, L a s s i t e r , Davis, Brown and Seath (1956) evaluated soybean meal, urea and dicyandiamide as nitrogen sources i n low protein (13.1%) concen-tr a t e mixture for dairy cows. Each nitrogen source supplied one t h i r d of the nitrogen i n the concentrate mixture and each cow received two pounds of medium q u a l i t y timothy hay per 100 l b . body weight d a i l y as the only rough-age. Differences i n milk production were observed on a l a c t a t i o n basis or during a comparison period of 196 days i n length beginning 30th day of l a c t a t i o n . The average d a i l y milk production at the beginning and end of 196 days period was 35.3 and 18.5, 35.9 and 14.4; and 36.2 and 15.5 l b . per cow d a i l y for soybean meal, urea and dicyandiamide r a t i o n s , r e s p e c t i v e l y . The differences were s i g n i f i c a n t . Minor differences i n feed consumption existed between groups. Hay consumption was 18.5, 18.0 and 16.8 lb./cow d a i l y and concentrate consumption was 11.9, 10.8 and 11.5 lb./cow d a i l y for the three groups, r e s p e c t i v e l y . Owen, Smith and Wright (1943) pointed out i n th e i r balance experiments on dairy cows that when urea and blood meal replaced 257, of the nitrogen i n a r a t i o n no differences i n milk production or i n nitrogen balance were shown for many weeks. They also indicated that when urea was withdrawn a decrease i n milk production occured immediately. Hastings (1944) replaced maize g l u t e i n i n a concentrate by urea which supplied 257, i n the beginning and 437. of the t o t a l nitrogen i n the end of the experiment i n the r a t i o n of dairy cows. The protein content of the concen-trate was 20.67.. Results showed that the average milk y i e l d when using t h i s urea r a t i o n was greater than i n c o n t r o l r a t i o n . Many workers have shown that urea i s poor for milk production as com-pared to soybean meal. 3 9 . Bartlettand Blaxter (1947) emphasized that any protein sparing e f f e c t of urea or other sources of non-protein nitrogen can only be determined i n animals fed protein d e f i c i e n t r a t i o n s . The addition of protein to such a r a t i o n by increasing the percentage of crude protein i n the r a t i o n from 12.9 to 17.9, resulted i n a s i g n i f i c a n t increase i n milk production. This confirmed the protein deficiency of the lowprotein r a t i o n . They stated that the add-i t i o n of s u f f i c i e n t urea to such a low protein r a t i o n to increase the crude protein to 1 7 . 9 7 o , that i s the ad d i t i o n of the same amount of nitrogen as urea as had been added as protein, r e s u l t e d i n no s i g n i f i c a n t mean change i n milk production. When urea was added to a normal protein r a t i o n (17.97° crude protein) a decline i n y i e l d occured. This was however not s t a t i s t i -c a l l y s i g n i f i c a n t . Ward, Huffman and Duncan (1955) fed cows a concentrate containing about 1 5 7 o of soybean meal or 2 7 o of urea besides basic feeds. Results showed that milk production i n F.C.M. ( f a f corrected milk) was not s i g n i f i c a n t l y d i f f e r -ent when cows were on concentrate with soybean meal or urea. F.C.M. produced was 27.6 and 28.2 lb./day for urea and soybean meal r a t i o n s , r e s p e c t i v e l y . Otagaki, Wayman, Morita and Iwanaga (1956) fed the cows a r a t i o n i n which 217., of nitrogen requirement was supplied by urea. Results showed that there was no s t a t i s t i c a l d i f f e r e n c e i n milk production between the c o n t r o l and the other group. E f f e c t of urea on milk production, fed as a spray on hay, has also been studied. Pallan and PejoVic (1965) fed sheep during winter on hay sprayed with urea so l u t i o n at the rate of 0.25kg. urea i n 2 l i t e r s of water on the days r a t i o n for 20 sheep. Results of th e i r experiment showed that the ewes given urea maintained th e i r body weight but milk y i e l d s f or the firs'tefl.O'eek period were poorer. The controls who ate 0 . 3 to 1.5kg. hay d a i l y without urea l o s t weight. 40. Some workers have compared urea with other NPN sources for milk pro-duction. Loskutov and Berkoric (1965) studied the e f f e c t of 257, of d i g e s t i b l e protein provided for prolonged periods by urea (90g. d a i l y ) and ammonia solution (225ml. d a i l y ) on milk production and milk composition of cows. Results showed that cows given urea had somewhat greater phagocytic a c t i v i t y of blood and higher g l o b u l i n values than the others and also gave more milk throughout the l a c t a t i o n period with higher contents of f a t , protein and casein. Waite, Castle, Watson and Drysdale (1968) conducted an experiment to compare the feeding value of concentrates for milk production i n which the nitrogen normally supplied by o i l cake was completely replaced by either b i u r e t or urea. Each cow had been milking for 70 days before the experi-ment started. Urea or b i u r e t contributed 527, of the t o t a l nitrogen i n the concentrates. Hay was fed as the sole roughage. Concentrates had 3.1% t o t a l nitrogen on dry matter ba s i s . Concentrates were fed at the rate of 4 lb./10 l b . milk. Results showed that milk production was 107> less on urea and b i u r e t treatments than on the c o n t r o l . M ilk y i e l d i n pounds/cow/ day was 25.5, 23.0 and 22.8 and l i v e weight change i n pounds/cow/day was -0.5,-0.6 and -0.5 for c o n t r o l , b i u r e t and urea r a t i o n s , r e s p e c t i v e l y . T o t a l dry matter intake (hay + concentrate) was 23.4, 23.1 and 22.4 lb./cow/day, re s p e c t i v e l y for the three treatments. Intake of the concentrates was 9.7, 9.5 and 9.0 lb./cow d a i l y for the three groups. The percentages of f a t and protein i n the milk from urea and b i u r e t treatments were higher than from the c o n t r o l . This was due to low milk y i e l d i n the former treatments. Percentage of f a t i n the milk was 4.05, 4.45 and 4.377. and that of crude protein was 3.10, 3.16 and 3.197, for c o n t r o l , b i u r e t and urea treatments, r e s p e c t i v e l y . 41. Urea has been fed separately along with s i l a g e . Some workers have used urea treated s i l a g e . Van Horn, Jacobson and Gradten (1969) fed cows on corn s i l a g e and ground shelled corn. One group was given added urea at the l e v e l of 423g. and the other group at the l e v e l of 81g. urea/cow d a i l y . Crude protein content of both the ra t i o n s was the same (13.57<> on dry matter b a s i s ) . Results showed that milk production and weight gains were lower on high urea than low urea r a t i o n . Feed intake for the low urea and high urea r a t i o n was 34.2 and 33.8kg. and milk production was 25.9 and 23.4kg. d a i l y , respec-t i v e l y . Van Horn, Hocraffer and Foreman (1969) conducted experiments to f i n d the milk production responses from urea treated corn s i l a g e . Results of the f i r s t experiment showed that l a c t a t i n g 'Holstein cows produced s i g n i f i -cantly l e s s milk when rec e i v i n g urea i n high-dry matter corn si l a g e at the l e v e l of 0.570 as compared to the production when cows received soybean meal as the only nitrogen supplement. No s i g n i f i c a n t differences were observed between respective dry matter intakes and f a t percentage. Milk y i e l d s i n Kg. per cow d a i l y for soybean meal and urea supplemented cows were 26.9 and 26.4 kg. for the preliminary period and 23.2 and 20.5kg. during the experimental period, r e s p e c t i v e l y . Body weight gains were 0.44 and 0.39kg./cow d a i l y for urea and soybean meal r a t i o n , r e s p e c t i v e l y . In another experiment l a c t a t i n g H o l s t e i n cows receiving 31.970 dry matter urea treated s i l a g e produced s i g n i f i c a n t l y more milk than cows rec e i v i n g 4 6 . 2 7 o dry matter urea treated s i l a g e . Their preliminary period milk y i e l d s were 26.7 and 26.8kg. and experimental period milk y i e l d s were 22.7 and 20.6 kg. per cow d a i l y , r e s p e c t i v e l y . They concluded that high dry matter urea treated s i l a g e i s not s a t i s f a c t o r y as lower dry matter urea treated si l a g e 42. for l a c t a t i n g dairy cows. The feed intake was similar i n both the cases. The d i g e s t i b i l i t y and retention of absorbed nitrogen was lower for the high dry matter urea treated s i l a g e which resu l t e d i n lower milk production. Solovev, Manenkova and Belova (1966) studied the e f f e c t of urea i n the feed of cows on,the qu a l i t y of milk who were given urea to replace 357, of the d i g e s t i b l e crude protein of the r a t i o n . Results indicated that urea i n milk increased but there was l i t t l e change i n t o t a l p r o t e i n . Van Horn, Foreman and Rodriguez (1967) fed cows a r a t i o n containing 14.97, crude p r o t e i n . Each cow was offered 4.6kg. hay, 18.2kg. corn s i l a g e and 18.2kg. of concentrate d a i l y . Addition of 2.77, urea to the concentrate mixture res u l t e d i n s i g n i f i c a n t depression of feed intake but there was no i n t e r a c t i o n between urea and corn s i l a g e . Depression i n milk production was thought to be due to depressed feed intake. The depressed feed intakes were 4.4kg. hay, 17.0kg. corn s i l a g e and 7.8kg. concentrate d a i l y . M ilk produc-t i o n with urea was 22.0kg./day as compared to 26.4kg./day without urea. Colovos, Holter, Davis and Urban,Jr. (1967) fed l a c t a t i n g cows on a r a t i o n containing 17.27, crude p r o t e i n . A concentrate mixture containing 0.0, 1.25, 2.0 or 2.57, urea (427, N) was fed i n place of an equivalent amount of plant p r o t e i n nitrogen, with good q u a l i t y timothy hay. There were no s i g n i f -icant differences i n milk production or composition or i n r a t i o n d i g e s t i b i l i t y . Protein balance was p o s i t i v e i n a l l treatments. Rohr (1962) as c i t e d by Briggs (1967) studied the influence of a high proportion of c e l l u l o s e i n dairy cow r a t i o n s . In h i s experiments i n vivo and i n v i t r o he found that a large amount of f i b e r i n the r a t i o n leads to a marked reduction i n the number of microorganisms i n the contents of the rumen. The mi c r o f l o r a o r i g i n a t i n g under these conditions, i n s p i t e of i t s lower number, has a greater urease a c t i v i t y than a more numerous micror organism population when given starch feedstuff. A large amout of f i b e r and 4 3 . the r e s u l t a n t easy and rapid decomposition of urea into ammonium nitrogen causes a r i s e i n the p'H i n the rumen which increases the permeability of the w a l l of the rumen. This consequently leads to an increase i n the los s of ammonium nitrogen as a r e s u l t of i t s entry into the blood c i r c u l a t i o n . However, he indicates further that urea w e l l mixed with the r a t i o n , ensur-ing a constant regular supply of urea to the rumen, leads to good urea u t i l i z a t i o n and maintains a high milk production even when the r a t i o n con-tains a r e l a t i v e l y large amount of crude f i b e r . He demonstrated t h i s by comparing the influence of an addition of soybean bran or urea to a r a t i o n d e f i c i e n t i n p r o t e i n . When cows were fed r a t i o n d e f i c i e n t i n protein with a large f i b e r content, the addition of urea w e l l mixed with the r a t i o n mass caused an increase i n the number of rumen microorganisms to the same degree as soybean bjran. This i n turn led to better digestion of the f i b e r , then to a c i d i t y of the rumen area, and by t h i s to an improvement i n the urea u t i l i z a t i o n i n the rumen. E f f e c t s of l e v e l s of f i b e r i n the concentrate mixture and the e f f e c t of urea, on milk production has been further investigated. Colovos et. a l (1967) used il£>lstein cows, i n the second through f i f t h months of their l a c t a t i o n , to study the e f f e c t of concentrate f i b e r and urea on r a t i o n u t i l i z a t i o n and production. Crude pr o t e i n content of the concentrate mixture was 16.77<». Body weight of the four animals used at the beginning of experiment ranged from 400 to 500kg.. and d a i l y milk production: was between 20 and 23kg. Concentrate mixtures containing corn meal, oat meal feed, brewer's grains, molasses, soybean meal and minerals were fed according to milk production. Levels of urea ( 4 2 7 o N) i n the concentrate mixture were 0 and 27« and the l e v e l s of f i b e r were 5 and 8 7 c F a i r q u a l i t y timothy hay was fed as the only forage at the rate of 27» of body weight. 44. Only minor differences occured i n ra t ion intake, protein d i g e s t i b i l i t y and milk production. The higher levels of concentrate f iber and urea s l i g h t l y depressed actual milk production. Average 47, FCM (fat corrected milk) production was 16.30 and 15.78kg. for 57, and 87, f iber and 16.3 and 15.75kg./ day for 0 and 2.07. urea, respec t ive ly . High levels of concentrate f iber and urea s i g n i f i c a n t l y depressed r a t ion d i g e s t i b i l i t y . Dry matter, energy and prote in intake were not s i g n i f i c a n t l y affected by treatments. Ration protein d i g e s t i b i l i t y was 66.6 and 65.47, wi th 5 and 87. f iber and 65.6 and 66.47, with 0 and 2.07. urea i n the concentrate, r espec t ive ly . Urea s i gn i f -i can t ly improved the d i g e s t i b i l i t y of f iber i n the ra t ion when included i n the low f iber concentrate mixture but had the opposite effect i n high f iber concentrate. They a t t r ibuted th i s to higher intake of f i be r . The l e v e l of urea i n milk under various conditions of feeding, has also been invest igated. The Nat ional Research Council (1953) indicated that cows normal milk contains from 10. to 60mg»n3?ea/lOOuml.i. Briggs and Hogg (1964) studied the effect of dietary urea on the l e v e l i n m i l k . One group of cows was fed a conventional r a t ion which included a protein supplement. The second group received a da i ly average of 3 l b . per head of urea feed (107, urea i n molasses with added minerals and v i tamins) . Individuals showed s ign i f i can t var ia t ions i n the milk urea l e v e l from day to day which were independent of milk y i e l d . In cows given urea the range i n milk urea was from 15 to 4S4)mg./100 ml . In cows fed the conventional r a t ion including prote in supplement the range was from 3j3; to 58 mg./100ml. The differences between the two groups were not s i g n i f i c a n t . Urea feeding has been shown to exert no influence on milk composition or f lavour . Vir tanen (1966) studied the effect of feeding urea on milk 4 5 . composition i n l a c t a t i n g cows. Results showed that the composition of the test milk was similar to that of normal milk. ^Fractionation, of casein and serum proteins of the test milk and normal milk by d i f f e r e n t methods showed the s i m i l a r i t y of the proteins of the two milks. He further stated that the flavours of the two milks was also s i m i l a r . 4 6 . VI. EXPERIMENTAL Experiment No. I  Animals Used T h i r t y bred ewes, belonging to The U n i v e r s i t y of B r i t i s h Columbia, were used for t h i s study during the session of 1967-68. Ewes were main-tained at the sheep u n i t . Ewes were divided equally into two groups on the basis of weight, breed and age. In Group I a l l ewes lambed. In Group II two ewes did not lamb. Feeding Both groups of ewes received the same amount of protein 90g.(0.21b.) d i g e s t i b l e crude protein (D.C.P.)/head/day) during the l a s t s i x weeks of pregnancy and 225g. (0.51b.) D.C.P. during l a c t a t i o n . Their D i g e s t i b l e Energy (D.E.) requirement was supplied as follows. During l a s t 6 weeks of pregnancy During l a c t a t i o n Group I Maintenance + 50% Maintenance + 150% Group II Maintenance + 100% Maintenance + 100% The above mentioned amount of protein and energy was supplied to both groups by various amounts of brome hay, a l f a l f a hay, beet pulp and, or dairy p e l l e t s , as indicated below! -47. Energy Levels and Feed Supply - Per Head Per Day ' Livie weight Required Brome hay Beet pulp Dairy pe! Group I (Kg) Di g e s t i b l e (Kg) (Kg) (Kg) (Pregnancy) Energy (K.Calories) 55 3000 1.36 60 3200 1.45 65 3400 1.54 X X 70 3600 1.63 75 3800 1.72 Group II (Pregnancy) 55 4100 0.72 0.81 60 4400 0.77 0.86 65 4700 0.81 0.90 70 4900 0.86 0.95 75 5100 0.90 1.00 Group I (Lactation) 55 5200 0.68 1.13 60 5700 0.77 1.22 65 6000 0.81 X 1.27 70 6200 . 0.86 1.31 75 .6500 0.90 1.36 Group II (Lactation) 55 .4100 1.40 0.31 60 . 4400 1.45 0.36 65 4700 1.50 X 0.40 70 4900 1.54 0.45 75 5100 1.59 0.50 48. The composition of the rations i s given i n Table A l . A l l ewes were weighed 7 weeks before p a r t u r i t i o n , p re-part urn, post-partum and then every week during l a c t a t i o n . M i l k i n g of Ewes and Analysis of Milk Samples Three ewes from each group were used f o r hand milki n g . Ewes were given an i n j e c t i o n of an oxytocinic preparation i n the morning and t h e i r udders were emptied by hand milking. The lambs were kept separate from the ewes i n the adjoining pen where ewes could see the lambs. A f t e r four hours the ewes were again given an i n j e c t i o n of the oxytocinic preparation and immediately hand milked a f t e r keeping them secure i n the metabolism cages. The quantity of milk obtained f o r four hours was measured and the t o t a l amount of milk produced during 24 hours was determined. Samples were obtained a f t e r thorough mixing of the milk and were retained f o r the analysis of f a t , prot e i n , l a c t o s e , t o t a l s o l i d s and ash. A l l samples were brought back to the laboratory and kept overnight under r e f r i g e r a t i o n . Samples were analyzed i n the morning i n the P r o v i n c i a l Government Dairy Branch Laboratory by i n f r a red milk analyzer f o r the determination of f a t , protein, and lactose percentage. For t o t a l s o l i d s determination 5mls. of milk were put i n t o an already weighed c r u c i b l e , weighed and then c r u c i b l e was placed i n a b o i l i n g water bath f o r 4 hours and then put i n the oven f o r 3 to 4 hours u n t i l constant weight was obtained. Crucibles were weighed again and the amount of t o t a l s o l i d s determined. For the determination of ash cruci b l e s containing t o t a l s o l i d s were weighed and put i n furnace f o r 2 hours at 500°C. Afterwards they were taken out of the oven at 100°C, cooled i n a desiccator and weighed again. The d i f f e r e n c e i n weight gave the amount of ash and then the percentage i n the o r i g i n a l 5 ml. of milk samples was determined. A l l determinations were done i n dup l i c a t e . 49 Weaning of Lambs Bir."bhweight of every lamb was recorded and they were weighed every week u n t i l weaning. Twenty-seven iambs from both the groups of ewes were weaned at 6 to 8 weeks of age and divided into three groups of nine lambs each on a weight b a s i s . Lambs i n Group I received hay + p e l l e t e d grain r a t i o n (20%.protein); Group II, hay + p e l l e t e d grain r a t i o n (16% protein) and Group III, hay + p e l l e t e d g r a i n r a t i o n (13%, p r o t e i n ) . Composition of the r a t i o n s i s given i n Table A^ 2'. P e l l e t s were fed to appetite and the amount being fed was increased gradually. The amount of hay given and refused was recorded and thus the amount of hay consumed d a i l y by each group was determined. The amount of p e l l e t s consumed by each group was also recorded d a i l y . Total amount of feed consumed during 10 weeks was also c a l c u l a t e d . A l l the groups received almost same amount of t o t a l p e l l e t s and hay during the 10 week period a f t e r weaning. Lambs were weighed every week. D i g e s t i b i l i t y Study Four male lambs from each of the three groups were used for t h i s study. They were kept i n metabolism cages and fed on hay and received the same p e l l e t s as t h e i r parent group. Water was a v a i l a b l e a l l the time. They were kept for 5 days during preliminary period and then the amount of hay and p e l l e t s consumed each day was recorded at the commencement of the study. The study lasted for 4 days for each animal during which the amount of faeces and urine produced was recorded d a i l y , 10 ml. of 10%, sulphuric a c i d was added d a i l y to the urine c o l l e c t i o n v e s s e l and 10 ml. of 2%, b o r i c a c i d to trap ammonia was also added to the faeces container. Representative samples of urine and faeces were obtained a f t e r thoroughly mixing each and were brought back to the laboratory where urine samples were put i n the freezer. 50. Faeces samples were put i n the preweighed p e t r i dishes, weighed and dried for 7 hours at 95°C and reweighed. So the amount of dry matter i n faeces was determined. Dried faeces samples were analyzed for nitrogen (on dry matter basis) by Kjeldahl's method. Later urine samples were also analyzed for nitrogen by the same method. Feed samples were also analyzed on a dry matter basis. A l l samples were analyzed for nitrogen i n duplicate. 51. Experiment No. II  Management Th i r t y l a c t a t i n g Dorset ewes, Dorset ewe lambs and crossbred ewes were used f o r t h i s study. They were divided equally into 3 groups, of 10 ewes each, on a weight bas i s . The groups of ewes were a l l o t t e d to three d i f f e r e n t rations which provided equal amount of nitrogen to a l l the three groups; Group I was provided nitrogen from p e l l e t s containing soybean meal; Group II from p e l l e t s containing soybean meal + urea and Group I I I from p e l l e t s containing urea alone. These p e l l e t s were analyzed for nitrogen by Kjeldahl's method. Urea percentage i n the p e l l e t s was determined by using p-dimethylaminobenzaldehyde (PDAB) and by using the basis of the method of Watt and Chrisp (1952). P e l l e t s were f i n e l y ground and a known amount of sample was extracted with water and f i l t e r e d into a Volumetric f l a s k and made up to the mark and mixed. This s o l u t i o n was d i l u t e d so that the concentration was 20 to 200 mg. %^0.2'ml. of t h i s s o l u -t i o n was added to 4 ml. of PDAB so l u t i o n , mixed thoroughly and read at 435 iip. against a blank made i n the same way by s u b s t i t u t i n g 0.2 ml. water f o r the sample. Sample values obtained t h i s way were read against a standard curve made using f r e s h l y prepared known urea solutions. Milk Y i e l d Three Dorset ewes from each group were taken for milk y i e l d determi-nation. The method used for the determination of milk y i e l d , c a r r i e d out once a week f o r 8 weeks, was the same as i n the f i r s t experiment except that an udder cover l i k e the one used by Owen (1957) was employed. The udder cover was applied a f t e r f i r s t hand milking i n the morning and the lambs remained, along with t h e i r dams in.the same pen. The udder cover was removed a f t e r 4 hours at the time of second milking. T o t a l y i e l d f o r 24 hours was determined. 52. Milk A n a l y s i s Milk samples were analyzed for f a t , protein, lactose, t o t a l s o l i d s and ash by the same method as i n the f i r s t experiment. Samples of milk were al s o freeze dried for l a t e r milk urea nitrogen determination. The freeze dried milk was reconstituted by the ad d i t i o n of water on thebasis of percentage of t o t a l s o l i d s i n each sample and analyzed by the method of Brown (1959) which i s described i n a l a t e r section. The method employed was s i m i l a r except that milk was Used instead of blood plasma and milk urea nitrogen l e v e l was determined. Blood Analysis Blood samples were taken from the 30 ewes once a week for 8 weeks for the determination of plasma urea nitrogen. Analysis was c a r r i e d out by the method of Bfe'own (1959). Whole blood was used for tikis determination and the values obtained were corrected on blood plasma.basis a f t e r finding the percentage of blood plasma i n the whole blood. The whole blood was used because i t was c o l l e c t e d i n heparinized tubes and then frozen. The blood hemolyzed and serum or plasma.could not be taken out of i t . Blood samples were also taken every, week from 5 lambs i n each group for a period of 4 weeks. Blood plasma was used for urea nitrogen determin-a t i o n by the method mentioned above (Brown, 1959). The procedure was as follows. One ml. of water (blank for standards), one ml. of urea-free plasma (obtained by adding 3 or 4 drops of urease preparation to f i v e ml. of pooled plasma and used as blank for unknowns), one ml. a l i q u o t s of the standards and one ml. a l i q u o t s of the unknown plasmas were pipetted into appropriately l a b e l l e d test tubes. Seven ml. of water was added to each tube and mixed. One ml. of zinc sulphate s o l u t i o n was added to each tube and mixed thoroughly' 53. One ml. of sodium hydroxide s o l u t i o n was then added to each tube and again mixed thoroughly. /The contents of the tubes were transferred to appro-p r i a t e l y c o l i a f o e O f h Q s l - tubes and centrifuged. Then two ml. aliquots of the clear portion of the centrifugate were transferred to appropriately l a b e l l e d cuvettes. Two mis. of the p-dimethylaminobenzaldehyde color reagent was added to each and mixed thoroughly. Cuvettes were allowed to stand f o r 10 minutes. Absorbance was measured i n a "Spectronic 20" spectrophotometer at 400 mu.., s e t t i n g the instrument at zero absorbance with the water blank for the standards and with the urea free plasma blank for the unknowns. A standard curve was prepared by p l o t t i n g the absorbances against the concen-tr a t i o n s of the standards. The concentrations of the unknowns was determined from the standard curve. Growth of Lambs Th i r t y lambs were weaned at 8 to 10 weeks of age and were divided equally on the basis of weight into three groups and were a l l o t t e d to three d i f f e r e n t rations providing equal amount of nitrogen from soybean, soybean + urea and urea p e l l e t s . Lambs were weighed weekly f o r 16 weeks. Digestion T r i a l A digestion t r i a l was c a r r i e d out with 2 male lambs from each group for 5 days a f t e r a preliminary period of 4 days. Water was a v a i l a b l e a l l the time. Lambs were given p e l l e t s up to appetite and the amount of p e l l e t s given and refused was recorded and the amount of p e l l e t s consumed was determined. Faeces and urine were c o l l e c t e d and analyzed as i n the f i r s t experiment. 54 VII. RESULTS AND DISCUSSION Experiment I Two groups of ewes were fed two rations providing different levels of energy. Maintenance requirement of Digestible Energy + 50$ and maintenance + 100$ was fed to Group I and Group II, respectively, during late pregnancy. Both the groups were fed 90g. (0.21b.) D.C.P./head/day during late pregnancy and 225g. (0.51b.) D.C.P./head/day during early lactation. During early lactation, maintenance requirement of energy + 150$ was fed to Group I and maintenance + 100$ was fed to Group II. Out of thirty ewes a l l but two (in the second group) were pregnant and lambed. Both groups gained weight during late pregnancy and lost weight during early lactation. The weight changes of the ewes are shown in Fig. I. Average weights of ewes during late pregnancy and early lactation are given in Table I. Weight gain by the ewes in Group II during late pregnancy was significantly greater (P<0.01) than that by ewes in Group I. Weight loss during early lactation was significantly lower (P<Q.05) in ewes of Group I as compared to ewes in Group II. Ewes average daily milk yield is given in Table II. There were no significant differences in milk production by the two groups of ewes. The protein supply of the ewes during pregnancy was in line with the National Research Council (1968) recommendation of 0.21b. Digestible Crude Protein during the last six weeks of gestation for a ewe of L40 lb. live weight or over. However, Phillipson (1959) has suggested 0.25 lb. D.C.P. for ewes of this weight range in the later stages of pregnancy. Robinson and Forbes (1968) supplied to their ewes a standard digestible crude protein intake of 8.8g/kg. W0"7^ (W=live weight in Kg.) or O.42 lb. D.C.P./150 lb. ewe daily during early lactation. This level of protein was fed in conjunction with a Metabolizable Energy intake of 125$ or 150$ of the maintenance requirement of non-pregnant ewes. They indicated that the difference between the rates of liveweight gain on the two energy levels was about 80-75» 7<W 65-60 Fig I  Experiment I Ewe Weights Group I Group II 55 50 45 7 weeks before Parturition Pre-partum and Pos1>partum weight U 5 Lactation Weeks 55. 0.06 kg./day i n favour of the higher l e v e l . The diff e r e n c e was s i g n i f i c a n t . In l i n e with Robinson and Forbes (1968) experiment the protein supplied during l a c t a t i o n i n t h i s t r i a l should have been adequate. Pre-weaning weekly weights of singles and twins from both the groups of ewes are shown gr a p h i c a l l y i n F i g . I I . During the eight weeks of the l a c t a t i o n s i n g l e lambs i n Group I weighed s i g n i f i c a n t l y heavier (P^0.05) than those i n Group I I . Single and twin lamb growth during the pre-weaning period i s shown i n Tables I I I and IV. Twins i n Group I were also s i g n i f i c a n t l y heavier (P<0.05) than those i n Group I I . Single lambs from ewes i n Group II were s i g n i f i c a n t l y heavier (P<0.05) than twins from the ewes i n Group I. As already indicated there were no s i g n i f i c a n t differences i n milk y i e l d by the two groups of the ewes. There were also no s i g n i f i c a n t differences i n f a t , protein and lactose percentage of milk from the two groups. Average d a i l y milk production of the ewes and f a t , protein and lactose percentage of the milk are shown graphically, i n Figs. I l l and IV a e£ad^Witi% 3Av.erage-'fa!b>, p'toteim <&nd t J f t C O t a S B L i c i * percentages i s given i n Tables V, VI and VII. Milk production i n both groups declined sharply at the end of the second week a f t e r which the decrease was gradual. The pattern of the curves for the percentages of protein and lactose was s i m i l a r i n both the groups during the 8 week period. Lactose content of the milk was f a i r l y constant i n both the groups. The protein content of the milk i n both the groups increased a f t e r the 3rd week when the milk y i e l d had declined but i t was almost the same from 4th week to the end of the 8 week period. Fat content of the milk decreased a f t e r the f i r s t three weeks of l a c t a t i o n and there was greater f l u c t u a t i o n during the f i r s t three or four weeks than during the l a t e r period. The milk composition as shown gr a p h i c a l l y indicated JJ-e. I l l ' • (k£.) :- §000 'Apoo •3000 Milk Yield (mis.) ;2000 3.900 ..." . Experiment I ; Avorafio M i l k y l o l d , ( i rd , . /24 h r ) —_ G r o u p I G r o u p I j 3 :K U e e k s A 4-000 ml. \^ 3000 ml. 0 \ Experiment I 1st group Milk Y i e l d and Composition = protein \ = lactose $ o . = f a t % 0 = milk y i e l d 2000 ml. 1000 ml. 13 "12 • • < 11 10 Percentage 9 8 \ \ \ \ 6 5 4 3 4 8 Milk Yield (mis) Percentage 4000 ml. h 3000 ml. U 13 12 11 10 9 8 7 6 j. 5 4 3 Fig.Iyt Experiment I Group II \ Milk Yield and Composition 4 \ 0 2000 ml. \ 1000 ml. = protein % = lactose % = fat % = milk yield \ \ \ \ / ' 3 4 Weeks 8 that the content of the above mentioned s o l i d s i n milk increased with a corresponding decrease i n milk y i e l d . Gardner and Hogue (1964) pointed out i n their experiment with ewes that f a t and protein values were higher at the beginning of l a c t a t i o n , declined to a minimum a f t e r 2 to 4 weeks, remained constant for next 3 to 4 weeks and then rose with.each successive week of l a c t a t i o n , during a t r i a l period of 12 weeks. Lactose values remained r e l a t i v e l y constant. TABLE I EXPERIMENT I Average weight of ewes (Kg.) Weight of ewes before p a r t u r i t i o n Weight of ewes during early l a c t a t i o n (Weeks) 3roup 7 weeks before partur-i t i o n weight Pre-partum weight Post-partum weight 1st 2nd 3rd 4th 5th 6th 7 th 8 th I 56.9 66.0 59.4 60.1 60.6 60.2 59.8 59.3 58.8 57.9 56.9 II 60.2 73.1 65.9 64.6 63.0 61.8 61.0 60.4 60.0 58.8 58.1 TABLE I I EXPERIMENT I Ewes A v e r a g e D a i l y M i l k Y i e l d ( m l s / 2 4 h r . ) Weeks o f l a c t a t i o n G r o u p 1 s t 2nd 3 r d . . 4 t h . 5 t h . 6 t h . . 7 t h . . 8 t h 1 s t G r o u p 4 5 0 0 2136 2316 2308 2 2 2 0 1840 1734 1645 2nd G r o u p 2940 1896 1656 1248 1380 1221 1227 1165 TABLE III EXPERIMENT I Single Lamb Growth (Pre-weaning) Average Weekly Weight (Kg.) Weeks a f t e r b i r t h Group Bi r t h Weight 1st - 2nd 3rd 4th 5th 6 th 7 th 8 th I .3.8 5.9 8.0 10.6 13.1 15.5 18.0 19.9 20.1 II 1 4.2 6.1 7.8 10.1 12.4 14.0 15.6 16.6 18.0 TABLE IV EXPERIMENT I Twin Lamb Growth (Pre-weaning) Average Weekly Weight (Kg.) Weeks a f t e r b i r t h Group B i r t h Weight 1st 2nd 3rd 4 th 5 th 6th 7 th 8 th I 3.4 4.6 6.1 7.7 9.2 12.3 13.2 14.7 15.7 II 3.1 4.5 6.4 7.5 9.1 10.1 11.3 12.5 13.2 TABLE V EXPERIMENT I Average Fat Percentage of Milk Week of Lactation 1st ; 2nd 3rd 4 th 5 th 6 th 7th 8th 1st Group - 13.33 13.33 10.66 ; 9 . i i 8.82 9.65 10.05 2nd Group - • 13.42 13.43 9.43 .11.41 11.65 10.75 11.54 TABLE VI -EXPERIMENT J . Average Protein Percentage of Milk Week of Lactation 1st : 2nd 3rd 4th 5th , 6th . 7 th 8 th 1st Group - 3.46 ! 3.46 .5.92 ,4.69 '• 5.09 ' 4.97 5.44 2nd Group - 3.53 3.53 6.52 4.55 • 5.34 5.28 : 5.88 TABLE VII EXPERIMENT I AVERAGE LACTOSE PERCENTAGE OF MILK Week of Lactation 1st 2nd 3rd 4th 5th 6th 7th 8th 1st Group - 5.49 5.48 5.80 5.17 6.03 5.51 5.37 2nd Group - 5.94 5.98 5.66 5.04 5.33 5.41 5.21 W a i t e e t a l ( 1 9 6 8 ) i n d i c a t e d i n t h e i r e x p e r i m e n t w i t h cows t h a t f a t a n d p r o t e i n c o n t e n t o f m i l k i n c r e a s e d w i t h a c o r r e s p o n d i n g d e c r e a s e i n m i l k y i e l d . The m i l k y i e l d w a s v e r y , h i g h f o r t h e f i r s t two o r t h r e e w e e k s a s c o m p a r e d t o t h e l a t e r 5 w e e k p e r i o d o f l a c t a t i o n . C l a r k ( 1 9 6 1 ) i n d i c a t e d t h a t f o r ewes n u r s i n g t w i n s t h e m i l k p r o d u c t i o n o f t h e f i r s t w e e k o f l a c t a t i o n w a s a b o u t d o u b l e t h e p r o d u c t i o n o f t h e e i g h t h w e e k . The m i l k y i e l d o b t a i n e d i n t h e e x p e r i m e n t d u r i n g t h e f i r s t w e e k w a s m o r e t h a n d o u b l e t h e p r o d u c t i o n o f t h e e i g h t h w e e k i n b o t h t h e g r o u p s . I t w a s 4 5 0 0 m l . a s c o m p a r e d t o 1645 m l . i n G r o u p I a n d 2 9 4 0 m l . a s c o m p a r e d t o 1165 i n G r o u p I I f o r t h e 1 s t a n d 8 t h w e e k , r e s p e c t i v e l y . The f o l l o w i n g c o n c l u s i o n s c a n b e d r a w n f r o m t h e a b o v e d i s c u s s i o n . 1 . S i n g l e l a m b s w e i g h e d h e a v i e r a t b i r t h a n d a t w e a n i n g t h a n t w i n s r e g a r d l e s s o f t h e e n e r g y l e v e l s i m p o s e d d u r i n g p r e g n a n c y a n d l a c t a t i o n i n t h i s e x p e r i m e n t . 2 . The w e i g h t o f t h e l a m b s a t b i r t h w a s a f f e c t e d b y t h e w e i g h t o f t h e i r dams d u r i n g l a t e p r e g n a n c y . I t shows t h a t h e a v i e r ewes p r o d u c e h e a v i e r l a m b s . R a y a n d S m i t h ( 1 9 6 6 ) a l s o i n d i c a t e d t h a t t h e h e a v i e s t ewes p r o d u c e d h e a v i e r l a m b s a t b i r t h a n d a t w e a n i n g t h a n d i d t h e l i g h t e r e w e s . 3 . M i l k y i e l d o f t h e ewes w a s g r e a t e s t d u r i n g f i r s t 2 o r 3 w e e k s a f t e r w h i c h i t d e c l i n e d . 4 . P r o t e i n a n d l a c t o s e w e r e t h e l e a s t f l u c t u a t i n g c o n s t i t u e n t s o f m i l k a n d w i t h a d e c r e a s e i n t h e m i l k y i e l d t h e r e w a s a c o r r e s p o n d i n g i n c r e a s e i n t h e s o l i d s . F a t c o n t e n t w a s m o r e v a r i a b l e d u r i n g t h e f i r s t f o u r w e e k s o f l a c t a t i o n b u t a f t e r t h i s p e r i o d t h e f l u c t u a t i o n w a s l e s s , a n d l a t e r t h e r e w a s a n i n c r e a s e w i t h a c o r r e s p o n d i n g d e c r e a s e i n m i l k y i e l d . Weaning of Lambs Twenty seven lambs were weaned at 8 to 1 0 weeks of age and divided into three groups. Their average weight at weaning was 1 7 . 7 , 1 9 . 3 and 1 9 . 3 kg. for Group I , Group I I and Group I I I , and they were fed p e l l e t s containing 2 0 , 1 6 and 1 3 7 o crude protein, r e s p e c t i v e l y . Average d a i l y gain by weaned lambs i s shown i n Table V I I I and F i g . V . TABLE VIII EXPERIMENT I Post-weaning Lamb Growth Average D a i l y Gain No. of Animals Average D a i l y Gain Ration (kg.) 1 0.25 2 0.24 3 0.23 4 0.21 20 7, Crude protein 5 0.17 6 0.14 7 0.23 8 0.20 9 0.16 Average ; 0.20 1 0.17 2 0.12 3 0.10 4 0.14 16.7, Crude protein 5 \ 0.18 6 0.14 7 0.09 8 0.16 -9 0.12 Average 0.15 1 0.19 2 0.13 3 0.18 4 0.12 137, Crude protein 5 0.16 6 0.20 7 0.16 8 0.17 9 0.09 Average 0.16 6*, R e s u l t s s h o w e d t h a t t h e r e w e r e s i g n i f i c a n t d i f f e r e n c e s ( P < 0 . 0 5 ) i n a v e r a g e d a i l y g a i n o f l a m b s f e d p e l l e t s c o n t a i n i n g 20% a n d 16% p r o t e i n , a n d t h e l a m b s f e d t h e p e l l e t s c o n t a i n i n g 207, c r u d e p r o t e i n a c h i e v e d t h e g r e a t e s t g a i n . T h e r e w e r e no s i g n i f i c a n t d i f f e r e n c e s b e t w e e n l a m b s f e d 207, o r 137> a n d b e t w e e n 167, o r 137> c r u d e p r o t e i n . T h e r e w e r e m i n o r d i f f e r e n c e s i n f e e d i n t a k e b y t h e t h r e e g r o u p s . The r e a s o n t h a t l a m b s f e d 137, p r o t e i n made b e t t e r g a i n s may n a v e t b e e h ; d u e c t . o ' .the. f a c t . t h a t - t h e r e h w a s a h i g h e r p r o p o r t i o n o f s i n g l e l a m b s i n t h i s g r o u p , c o m p a r e d . t o t h e o t h e r two g r o u p s . The f e e d e f f i c i e n c y r a t i o o f t h e s e l a m b s i s shown i n T a b l e I X . The f e e d e f f i c i e n c y r a t i o w a s 3 . 9 , 5 . 7 a n d 5 . 0 f o r 2 0 , 16 a n d 137, p r o t e i n , r e s p e c t i v e l y . D i c k s o n ( 1 9 5 9 ) s u g g e s t e d t h a t a f t e r two m o n t h s o f a g e g r a s s b e c o m e s t h e d o m i n a n t f a c t o r i n t h e l a m b ' s d i e t . R a n h o t r a a n d J o r d a n ( 1 9 6 6 ) r e p o r t e d t h a t r a t i o n s c o n t a i n i n g b e t w e e n 12 a n d 147, p r o t e i n r e s u l t e d i n m o r e r a p i d g a i n s d u r i n g t h e f i r s t 28 d a y s f o l l o w i n g w e a n i n g , w h e n w e a n e d a t 6 t o 8 w e e k s o f a g e , t h a n r a t i o n s w i t h a l o w e r p r o t e i n l e v e l . They a l s o r e p o r t e d t h a t r a t i o n s c o n t a i n i n g a p p r o x i m a t e l y 1 6 . 5 7 , p r o t e i n d i d n o t s u p p o r t m o r e e f f i c i e n t g a i n s t h a n r a t i o n s c o n t a i n i n g 1 3 . 5 t o 147, p r o t e i n . D i g e s t i o n T r i a l . D r y m a t t e r d i g e s t i b i l i t y i s shown i n T a b l e X a n d n i t r o g e n d i g e s t e d a n d r e t a i n e d i s g i v e n i n T a b l e X I . R e s u l t s o f t h e d i g e s t i o n t r i a l w i t h l a m b s i n d i c a t e t h a t t h e d i f f e r e n c e s i n t h e d r y m a t t e r d i g e s t i b i l i t y a n d p r o t e i n d i g e s t i o n c o e f f i c i e n t o f t h e t h r e e k i n d s o f p e l l e t s ( 2 0 , 16 a n d 137, C . P . ) w e r e n o t s t a t i s t i c a l l y s i g n i f i c a n t . Lambs f e d t h e 20% C . P . r a t i o n r e t a i n e d s i g n i f i c a n t l y ( P < 0 . 0 5 ) m o r e n i t r o g e n t h a n t h o s e f e d t h e 167, a n d 137, C . P . r a t i o n . N i t r o g e n r e t e n t i o n w a s n o t s i g n i f i c a n t l y d i f f e r e n t b e t w e e n l a m b s f e d t h e 16% a n d 13% r a t i o n . R e s u l t s o f t h e d i g e s t i o n t r i a l i n d i c a t e t h a t 20% C . P . r a t i o n w a s b e t t e r f o r t h e g r o w t h o f l a m b s , b u t 16% 65. CP. ration did not provide extra growth as compared to 13% CP. ration. TABLE IX EXPERIMENT I POST-WEANING LAMB GROWTH FEED EFFICIENCY RATIO 20% Crude Protein 16% Crude Protein 13% Crude Protein Total Weight Gain (kg) 130 89.5 102.2 Total Feed Consumed (kg) 510.4 512.2 511.3 Feed E f f i c i e n c y Ratio 3.9 5.7 5.0 TABLE X EXPERIMENT I DIGESTION TRIAL OF LAMBS DRY MATTER DIGESTIBILITY No. of Tota l 7o D.M. Animals D.M. Digested Ration Intake 8 1 2 1 7 5 7 2 . 3 2 2 0 3 7 7 2 . 6 2 0 7 o Crude 3 2 0 2 3 6 8 . 8 Protein 4 1 7 5 4 7 4 . 0 Average 1 9 9 7 7 1 . 9 1 1 8 8 8 6 2 . 2 2 1 9 0 5 7 5 . 4 1 6 7 o Crude 3 9 6 1 7 7 . 6 Protein 4 1 2 3 4 6 6 . 4 Average 1 4 9 7 7 0 . 4 1 2 1 1 5 6 5 . 1 2 1 9 6 9 7 6 . 0 1 3 7 o Crude 3 2 1 6 7 6 8 . 3 Protein 4 9 6 0 7 1 . 9 Average 1 8 0 2 7 0 . 3 TABLE XI EXPERIMENT I DIGESTION TRIAL OF LAMBS NITROGEN DIGESTED AND RETAINED No. of Tota l N Digestion c o e f f i c i e n t N Retained Animals Intake percent - % N Digested Ration g % 1 8 3 . 4 8 8 . 7 9 1 . 6 2 8 0 . 6 8 5 . 1 9 0 . 9 2 0 7 = 3 8 0 . 3 8 6 . 4 8 9 . 1 Crude 4 7 2 . 6 8 3 . 3 9 2 . 2 Protein Average 7 9 . 2 8 5 . 8 9 0 . 9 . 1 6 6 . 4 8 8 . 7 8 8 . 2 1 6 7 o 2 6 4 . 7 8 5 . 6 8 1 . 4 Crude 3 3 0 . 0 7 9 . 3 8 6 . 5 Protein 4 4 1 . 5 8 7 . 9 8 9 . 3 Average 5 0 . 6 8 5 . 3 8 6 . 3 1 6 0 . 1 8 2 . 6 8 5 . 7 2 5 7 . 2 8 4 . 7 8 0 . 6 1 3 7 o 3 6 1 . 2 8 0 . 5 8 5 . 5 Crude 4 2 8 . 9 6 7 . 1 8 6 . 5 Protein Average 5 1 . 8 7 8 . 7 8 4 . 5 EXPERIMENT II During early l a c t a t i o n , nitrogen was provided to ewes i n equal amounts . i n three d i f f e r e n t forms i n p e l l e t e d r a t i o n s containing supplemental nitrogen as soybean, + soybean + urea, and urea alone. Ewes average d a i l y milk y i e l d i s shown i n Table XII and F i g . VI. There were no s i g n i f i c a n t differences observed i n average d a i l y milk production of ewes fed these r a t i o n s . Ward et a l (1955) reported that milk production i n F.C.M. (f a t corrected milk) was not s i g n i f i c a n t l y d i f f e r e n t when cows were fed a concentrate with soybean meal or urea. Bartlettand Bl&xter (1947) emphasized that any protein sparing e f f e c t of urea can only be determined i n animals fed a protein d e f i c i e n t r a t i o n . The a d d i t i o n of protein to such a r a t i o n , by increasing the percentage of crude protein i n the r a t i o n from 12.9 to 1 7 . 9 7 c r e s u l t e d i n a s i g n i f i c a n t inanase i n milk production. This confirmed the protein d e f i c i e n c y of the low protein r a t i o n . They stated that the a d d i t i o n of s u f f i c i e n t urea to such a low protein r a t i o n to increase the crude protein to 1 7 . 9 7 , r e s u l t e d i n no s i g n i f i c a n t mean change i n milk production. When they added urea to a normal protein r a t i o n (177, crude protein) a decline i n milk y i e l d occured. This was however not s i g n i f i c a n t . Otagaki et a l (1956) also reported that there was no s t a t i s t i c a l d i f f e r e n c e i n milk production between con t r o l cows and a group of cows fed a r a t i o n i n which 2 1 7 , of nitrogen requirement was supplied by urea. There were no s i g n i f i c a n t differences i n f a t , protein and lactose percentage of milk from the three groups. In a l l the three groups of ewes, milk y i e l d started to decline a f t e r the 4th week. Average f a t , protein, lactose and t o t a l s o l i d s are given i n Tables XIII, XIV, >XV" and XVI, and F i g s . VII, VIII and IX. The milk y i e l d and s o l i d s ( f a t and p r o t e i n and lactose percentage) followed an almost s i m i l a r pattern to the f i r s t Fig VI' flLlk Y i e l d (Ml.) 3000 2 5 0 0 2 0 0 0 1 5 0 0 1 0 0 0 Experiment I I Milk Y i e l d = soybean - - = soybean & urea = urea 8 Weeks fepOO ml. Milk Y i e l d Percentage 12 11 10 9 8 7 6 .5 2000 ml. : o' 11000 ml. \ F i g . VII Experiment I I  Soybean Ration \ \ = protein % = lactose % = f a t % = milk y i e l d > • i 1 2 i r— 1— 6 7 8 Weeks 1-3000 ml. P i g . -VI-II-Expjrljient I I \ Urea & /-Soybean''ration Mil k Y i e l d h 1000 ml. 13 12 11 10 Percentage 8 7 6 5 4 / 2000 ml. \ = protein % = lactose $ = f a t % - milk y i e l d Weeks I 3000 ml. I 2000 ml. 12 11 10 9 8 Percentage 7 h 1000 ml. "Fig. 1X1: Experiment I I \ Urea ration \ \ = protein % = lactose % .. = fat % _____ = milk yield \ \ 70. experiment, that i s there was an increase i n the percentage of these s o l i d s with a corresponding decrease i n milk y i e l d . Ewes average milk urea N l e v e l i s shown i n Table XVII. There were no s i g n i f i c a n t differences i n ewes milk urea nitrogen l e v e l among the three groups but there was v a r i a t i o n within the groups which was independent of the milk y i e l d . The range i n milk urea nitrogen l e v e l was from 2.7 to 7.5, 0.2 to 5.7, and 0«3 to 5.3 mg/100 ml. for urea, urea + soybean and soybean containing p e l l e t s , r e s p e c t i v e l y . Briggs and Hogg (1964) reported that i n cows given urea the range i n milk urea l e v e l was from 15 to 44 mg/100 ml. In cows fed conventional r a t i o n s including protein supplements the range was from 33 to 58 mg/100 ml. but the differences were not s i g n i f i c a n t . I t seems that l e v e l s of urea i n milk of sheep i s lower than that i n cow's milk as indicated by th i s experiment. They also reported that these l e v e l s of urea d i d not a f f e c t the quality of cow's milk. Since the l e v e l of urea i n sheep milk i s far lower than that i n the cow's milk, as indicated by the r e s u l t s of the experiment, there i s less p o s s i b i l i t y of the qua l i t y of sheep milk being affected by the urea secretion i n milk. Briggs and Hogg (1964) also reported that milk urea excretion was 1.4 to lO.Og/day and 3.7 to l7.3g/day for urea supplemented and protein supplemented r a t i o n s , r e s p e c t i v e l y . Their work suggests that feeding urea to dairy cows has no s i g n i f i c a n t e f f e c t on the level or output of urea i n the milk. Ewes Blood A n a l y s i s . Ewes average plasma urea N l e v e l i s given i n Table XVIII. Results of the blood analysis showed that these were no s i g n i f i c a n t differences between plasma urea nitrogen l e v e l (during f i r s t 8 weeks of lac t a t i o n ) of ewes fed soybean or soybean + urea containing p e l l e t s . Ewes fed these p e l l e t s had s i g n i f i c a n t l y lower (P<0.05) plasma urea nitrogen l e v e l than 71. TABLE X I I EXPERIMENT I I EWES AVERAGE D A I L Y M I L K Y I E L D (mis/24 hr) WEEKS OF LACTATION j j >\ i \ i RATION 1st 2nd 3rd 4th 5th 6 th 7 th 8 th S o y b e a n 1880 2120 - 2360 2310 2340 1454 1813 S o y b e a n + Urea 1920 2430 - 2720 2320 2450 2260 2133 Urea 1813 2550 - 2880 2400 1965 2310 1786 TABLE XIII EXPERIMENT II AVERAGE FAT'PERCENTAGE OF MILK WEEKS OF LACTATION RATION 1st 2nd 3rd 4th 5 th 6 th 7 th 8th Urea 10.48 11.17 8.56 8.37 8.51 7.74 8.45 9.47 Urea + Soybean 12.18 11.01 11.84 8.12 9.86 9.74 10.36 10.17 Soybean 11.14 8.95 9.70 7.42 8.94 9.35 7.94 7.36 TABLE XIV EXPERIMENT II AVERAGE PROTEIN PERCENTAGE OF MILK WEEKS OF LACTATION RRATION 1st 2nd 3rd 4 th 5 th 6 th 7 th 8 th Urea 4.22 4.56 5.26 5.79 5.25 5.61 5.07 5.94 Urea + Soybean 4.39 4.40 4.58 5.31 4.91 5.11 5.17 5.45 Soybean 4.78 4.51 4.38 4.70 5.79 5.16 4.86 5.47 TABLE XV EXPERIMENT I I AVERAGE LACTOSE PERCENTAGE OF M I L K WEEKS OF LACTATION RATIONS 1 s t 2 n d 3 r d 4 t h 5 t h 6 t h 7 t h 8 t h U r e a 4 . 7 3 4 . 8 4 4 . 9 4 4 . 7 7 4 . 5 9 5 . 1 7 5 . 2 5 4 . 6 6 U r e a + S o y b e a n 4 . 5 9 4 . 8 6 5 . 0 2 5 . 2 1 4 . 7 4 4 . 2 1 4 . 8 5 4 . 7 4 S o y b e a n 4 . 7 8 5 . 3 2 5 . 3 2 5 . 1 8 4 . 6 8 4 . 8 9 5 . 1 6 5 . 0 6 TABLE XVI EXPERIMENT I I AVERAGE TOTAL SOLIDS PERCENTAGE OF MILK WEEKS OF LACTATION RATIONS 1st 2nd 3rd 4 th 5 th 6 th 7 th 8 th Urea 20.13 21.30 19.46 19.63 19.10 19.32 19.47 20.82 Urea + Soybean 21.92 21.07 22.24 19.47 20.34 19.89 21.20 21.16 Soybean 21.43 19.58 20.13 18.03 20.13 20.16 18.71 18.65 TABLE X V I I EXPERIMENT I I EWES AVERAGE M I L K UREA...N ( m g . . U r e a N / 1 0 0 m l . ) WEEKS OF LACTATION RATIONS 1 s t 2nd 3 r d 4 t h 5 t h 6 t h 7 t h 8 t h S o y b e a n 2 . 1 5 . 3 2 . 0 2 . 3 0 . 3 2 . 6 2 . 8 2 . 0 S o y b e a n + U r e a 0 . 2 4 . 8 3 . 8 0 . 8 1 . 3 2 . 2 4 . 5 6 . 1 U r e a 3 . 5 7 . 5 2 . 3 6 . 7 2 . 7 4 . 3 4 . 8 5 . 5 76. those f e d p e l l e t s containing urea alone. D r o r i and L o o s l i (1961) also reported that urea nitrogen i n blood of sheep rose a f t e r d i e t s with urea and f e l l a f t e r d i e t s with soybean meal but the differences were not s i g n i f i c a n t . The ewes plasma urea nitrogen l e v e l i n t h i s experiment v a r i e d from 19.0 to 30.5, 23.6 to 48.1 and 31.5 to 48.6 mg/100 ml., for soybean, soybean + urea and urea containing p e l l e t s , r e s p e c t i v e l y . Lamb Growth Average weekly weights of lambs during t h e - p r e - w e a n i n g i p e r i o d ' a T e n g i v e n i n Table XIX and gra p h i c a l l y i n F i g X. The growth curves of lambs nursing ewes fed on soybean + urea and urea containing p e l l e t s overlap eath other during the pre-weaning period, i n d i c a t i n g l i t t l e d i f f e r e n c e i n the growth of lambs suckling ewes fed on these type of p e l l e t s . Growth curves of the lambs nursing ewes fed soybean containing p e l l e t s showed slower growth by such lambs. S t a t i s t i c a l analysis showed that there were no s i g n i f i c a n t differences i n the pre-weaning growth of lambs nursing ewes fed on p e l l e t s containing soybean + urea, and urea alone, and those lambs from ewes fed on p e l l e t s containing soybean made s i g n i f i c a n t l y slower gain (P<0.05) than those from the other two groups. The reason for t h i s slower rate of gain i s d i f f i c u l t to explain. Average weekly weights of lambs during t'hetpostsweaningxperI<5d;.'ar@rtgiven i n Table XX and F i g . XI. During the post-weaning period of 16 weeks, lambs fed on p e l l e t s containing soybean gained s i g n i f i c a n t l y greater (P<0.05) than those on p e l l e t s containing urea alone, but theEe were no s i g n i f i c a n t differences i n the weight gain of lambs fed on p e l l e t s containing soybean or soybean + urea and soybean + urea or urea alone. This indicated that p e l l e t s containing soybean proved better for the growth of lambs than those containing urea alone. Fig. X Experiment II  Lamb Growth  (Pre-weaning) Weeks soybean soybean & urea urea 4 3 .Fig XI ' Experiment II  Lamb Growth Rate  (Post-weaning) = soybean - - - - - = soybean & urea • • = urea Weight . (Kg.) 3 8 3 3 28 2 3 18 , 0 ' 1 2 3 " 4 5 6 7 8 9 1 0 1 1 1 2 1 3 H 15 1 6 17 Weeks TABLE XVIII EXPERIMENT I I EWES AVERAGE PIASMA UREA N (mg. Urea N/100 ml) WEEKS OF LACTATION RATIONS . 1st 2nd 3rd 4th 5th 6 th 7 th 8 th Soybean 26.0 28.9 28.2 27.1 30.5 28.7 19.0 27.1 Soybean + Urea 23.7 29.2 27.7 25.3 45.0 27.8 27.0 33.6 Urea 30.7 33.4 35.8 33.9 47.2 32.8 33.9 39.1 TABLE XIX EXPERIMENT I I LAMB GROWTH (PRE-WEANING) AVERAGE WEEKLY WEIGHTS (kg) WEEKS AFTER BIRTH RATIONS BIRTH WEIGHT 1st 2nd 3rd 4th 5 th 6 th 7 th 8 th 9 th Soybean 4.7 5.7 7.2 8.6 10.5 13.5 14.7 17.3 19.8 21.5 Soybean + Urea 4.0 5.9 7.6 9.0 12.3 15.3 16.8 19.3 19.9 23.8 Urea 4.0 6.2 7.5 9.7 13.0 15.0 17.4 19.4 22.2 24.8 79, Feed conversion r a t i o s were 4 . 0 , 5*1 and 5*9 f o r soybean, soybean ^ urea and urea containing p e l l e t s , r e s p e c t i v e l y . Lambs plasma Urea N l e v e l i s indicated i n Table XXI. There were no s i g n i f i c a n t d i f f e r e n c e s between plasma urea nitrogen l e v e l of lambs fed on soybean or soybean £ urea containing p e l l e t s . Lambs fed these two types of p e l l e t s had s i g n i f i c a n t l y higher (P<0.05) plasma urea nitrogen l e v e l than those fed p e l l e t s containing urea alone. Plasma urea nitrogen l e v e l f o r lambs varied from 25.2 to 26.3, 19.6 to 28.1 and 20.0 t o 26.9 mg./lOO ml., for.soybean, soybean ^-urea and urea containing p e l l e t s , r e s p e c t i v e l y . The reason that the picture of the blood urea l e v e l was d i f f e r e n t i n the case of lambs compared to ewes could be due to v a r i a t i o n i n the protein intake of the growing lambs, which can cause greater v a r i a t i o n i n BUN l e v e l s . Preston et a l (1965) reported that the v a r i a t i o n i n the protein intake of the growing lamb resulted i n blood urea nitrogen ranging from 2.7 t o 32.9 mg./lOO ml. Digestion T r i a l of Lambs. Dry matter d i g e s t i b i l i t y and nitrogen retained and digested i s shown i n Tables XXII and XXIII. Results of the digestion t r i a l with lambs showed that although the protein d i g e s t i o n c o e f f i c i e n t and dry matter d i g e s t i b i l i t y was higher f o r p e l l e t s containing urea, the d i f f e r e n c e s between p e l l e t s containing soybean, soybean-4-urea and urea alone, were not s t a t i s t i c a l l y s i g n i f i c a n t . P e l l e t s providing nitrogen from soybean resulted i n greatest nitrogen retention. Nitrogen retained from p e l l e t s containing soybean urea was greater than that from p e l l e t s containing urea alone. The differences were s i g n i f i c a n t (P<0.05). Least nitrogen retention was obtained from p e l l e t s containing urea and was due to greater excretion of nitrogen i n the urine. D r o r i and L o o s l i ( l 9 6 l ) a l s o reported that d i e t s with soybean meal gave better nitrogen retention and had a higher b i o l o g i c a l value than d i e t s with urea. They indicated that t h i s was r e l a t e d to the excretion of urea i n the urine. TABLE XX EXPERIMENT II LAMB GROWTH RATE (POST-WEANING) AVERAGE WEEKLY WEIGHT (kg) WEEKS AFTER WEANING RATIONS 1st 2nd 3rd 4 th 5 th 6 th 7 th 8 th 9 th 10th 11th 12 th 13 th 14th 15 th 16 th Soybean 18.6 21.9 22.0 23.1 24.4 24.7 25.0 27.3 29.0 31.4 32.3 33.6 35.0 35.8 37.0 36.0 Soybean + Urea 23.9 25.3 26.1 27.0 28.1 29.1 30.3 31.5 32.9 34.1 35.5 36.5 37.7 37.3 38.6 38.7 Urea 23.7 24.8 26.1 27.0 27.1 29.3 31.0 32.7 34.0 34.9 36.5 38.0 36.4 36.8 37.1 37.3 TABLE XXI EXPERIMENT II LAMBS AVERAGE PLASMA UREA N (mg. Urea N/100 ml.) WEEKS DURING POST-WEANING PERIOD RATION 1 2 3 4 Soybean 26.3 32.2 32.5 27.2 Soybean + Urea 19.7 27.7 28.1 22.7 Urea 21.1 26.0 26.9 20.0 TABLE XXII EXPERIMENT II DIGESTION TRIAL OF LAMBS DRY MATTER DIGESTIBILITY NO. OF TOTAL D.M. % D.M. RATION ANIMALS INTAKE DIGESTED g* 1 4529 58.6 Soybean. 2 4329 60.9 AVERAGE 4429 59.7 1 4529 47.2 Soybean + Urea 2 4192 70.1 AVERAGE 4360 58.6 1 3264 60.0 Urea 2 4128 62.3 AVERAGE 3698 61.4 TABLE XXIII EXPERIMENT I I DIGESTION TRIAL OF LAMBS NITROGEN DIGESTED AND RETAINED NO. OF ANIMALS TOTAL N INTAKE g DIGESTION COEFFICIENT PERCENT X N RETAINED 7 N DIGESTED RATION 1 45.2 55.7 84.1 Soybean 2 43.2 62.2 80.7 AVERAGE 44.2 • 58.9 82.4 1 2 45.2 41.8 64.8 66.9 73.0 73.2 Soybean + Urea AVERAGE 43.5 65.8 73.1 1 32.5 83.3 62.3 Urea 2 41.2 75.4 64.9 AVERAGE 36.8 79.3 63.6 VIII LITERATURE CITED 1. Abou Akkada, A. R. and T. H. Blackburn. 1963. Some observations on the nitrogen metabolism of rumen proteolytic bacteria. J. Gen. Microbiol. 3J.:46l-469. 2. Anderson, G. C, G. A. McLaren, J. A. Welch, C. D. Campbell and G. S. Smith. 1959. The comparative effects of urea, uramite, biuret, soybean protein and creatine on digestion and nitrogen metabolism in lambs. J. Animal Sci. 18;134. 3. Annison, E. F. 1956. Nitrogen metabolism in sheep. Protein digestion in the rumen. Biochem. J. 5_7:400-405. 4. Baird, D. M., H. C. McCampbell, W. E. Neville, H. Coirdia, W. E. Bizzell and 0. E. Sell. I960. Milk and forage consumption, growth, carcass characteristics and parasitism of early - vs. late -weaned lambs on winter temporary pastures. J. Animal Sci., 1_:1302. 5. Bartlett, S. and K. L. Blaxter. 1947. The value of urea as a substitute for protein in the rations of dairy cattle. I. Field trials with dairy cows. J. Agric. Sci. 3/7:32-44. 6. Beames, R. M. and J. G. Morris. 1965* Effect of salt/urea blocks on body weight, body composition and wool production of sheep fed low-protein native grass hay. Queensland J. Agric. Animal Sci., 22: 369-379, 7. Bell, M. C, "j. R. Taylor and R. L. Murphree. 1957. Effect of feeding stilbestrol and urea on ration digestibility and on retention of calcium and phosphorus and nitrogen in lambs. J. Animal Sci. 16:821-827. 8. Blackburn, T. H. 1965. Nitrogen metabolism In the rumen. In, Physiology of Digestion in the Ruminant. Edited by R. W. Dougherty, Allen, Burroughs, Jacobson and McGilllard. 1965. Butterworths, Washington. 9. Briggs, M. H. 1967. Urea as a Protein Supplement. Pergamon Press Ltd., New York. 10. Briggs, M. H. and M. L. Hogg. I964. Studies on urea-fed cattle 6. Effect of dietary urea on the level of urea in milk. Life Sci. _5:1493-1496. 11. Brothers, D. G. and J. V. Whiteman. 1961. Influence of early weaning on creep-fed milk lambs when weaned on weight or age. J. Aaimal S c i , |9:12®?425. , 1 n . 86. 12. Brown, H. H. 1959. Determination of blood urea with p-dimethylaminobenz-aldehyde. Anal. Chem. 31;1844« 13. Cameron, C. D. T. and L. S. Hamilton. 1 9 6 1 . Effect of age at weaning of Shropshire Lambs on weight gains and carcass score. Can. J . Animal S c i . ^ 1:180-186. 14. Cannon, D. J. I960. Lamb weaning management. J . Dept. Agric. V i c t o r i a . 2 8 : 7 3 5 - 7 3 6 . 15. Clark, E. A. 1954. Early weaning of lambs on h i l l country. N.Z.J. Agric. §9_:471-476. 16. Coetzee, C. G. and E. J . Vermeulen. 1966. Creep feeding of lambs i s worthwhile. S. A f r . J . Agric. S c i . 8 :53-54. 17. Colovos, N. F., H. A. Keener, H. A. Davis, B. S. Reddy and P. P. Reddy. 1963. Nutritive value of the dairy c a t t l e ration as affected by different- l e v e l s of urea and quality of ingredients. J. Dairy S c i . 46:696-702. 18. Colovos, N. F., J . B. Holter, H. A. Davis and W. E. Urban, J r . 1967. Urea f o r l a c t a t i n g dairy ca t t l e II. Effect of various l e v e l s of concentrate urea on n u t r i t i v e value of the ration. J. Dairy S c i . 5_0:523-526. 19. Coop, I. E. 1962. The energy requirements of sheep f o r maintenance and gain. I. Pen fed sheep J. Agric. S c i . 5_8:179-188. 20. Coop, I . E. 1966. Effect of flushing on reproductive performance of ewes. J . A g r i . S c i . 62:305-323. 21. Cronje, P. J . and W. H. K. Coetzee. 1966. The value of melamine as a source of non-protein nitrogen f o r sheep. S. Afr. J . Agric. S c i . 2:101-106. 22. de Cleene, R. J . 1968. Ewe n u t r i t i o n i n l a t e pregnancy. N.Z. J. Agric. 116;29. 2 3 . Dickson, G. R. 1959. The more e f f i c i e n t grazing of ewes and lambs. J. B r i t . Grassland Soc. 14:172-176. 24. Drori, D. and J . K. L o o s l i . . 1961. Urea and carbohydrate versus plant protein f o r sheep. J. Animal S c i . 20:233-238. 2 5 . Egan, A. R. 1965. The fate and effects of duodenally infused casein and urea nitrogen i n sheep fed on a low protein roughage. Austr. J. Agric. Res. 16:169-177. 8 7 . 2 6 . Egan, A. R. and R. J. Moir. 1 9 6 5 . N u t r i t i o n a l status and intake regulation i n sheep. 3» Effects of duodenally infused single doses of casein, urea and propionate upon voluntary intake of a low-protein roughage by sheep. Austr. J. Agric. Res. 1 6 : 4 3 7 - 4 4 9 . 27. Fisher, H. and D. Johnson, J r . 1958. The effectiveness of essential amino acid supplementation i n overcoming the growth depression of unheated soybean meal. Arch. Biochem. Biophys. 77:124» 28. Forbes, T. J . and J . J . Robinson. 1967. The effect of source and l e v e l of dietary protein on the performance i n lamb ewes. Animal Prod. 9_: 5 2 1 - 5 3 0 . 29. Franklin, M. C. 1965. Early weaning of Merino lambs during drought. Nutr. Abstr. Rev. 3_5_:522. 30. Gardner, R. W. and D. E. Hogue. 1963« Studies on TDN requirements of pregnant and l a c t a t i n g ewes. J . Animal S c i . 22:410-417. 31. Gardner, R. W. and D. E. Hogue. 1964* Effects of energy intake and numbers of lambs suckled on milk y i e l d , milk composition and energetic e f f i c i e n c y of l a c t a t i n g ewes. J . Animal S c i . 23_: 935-942. 3 2 . Garrigus, W. P. 1 9 5 1 . Concentrates f o r creep-fed lambs. Ky. Agr. Exp. Sta . B u l l . 5 6 7 . 3 3 . Glimp, H. A., M. R. Karr, C. 0. L i t t l e , P. G. Woolfolk, G. E. M i t c h e l l , J r . and L. W. Hudson. 1967. The effect of reducing soybean protein s o l u b i l i t y by dry heat and of neomycin on the protein u t i l i z a t i o n of young lambs. J . Animal S c i . 26:858. 34« Harris, L. E. 1940. The quantitative u t i l i z a t i o n of urea nitrogen by mature and grazing sheep. Ph.D. Thesis Univ. I l l i n o i s . 1940. 35« Hastings, W. H. 1944* The use of urea i n commercial dairy feeds. J. Dairy S c i . 22:1015-1021. 3 6 . Hinds, F. C, M. E. Mansfield and J. M. Lewis, 1963. The influence of methionine, l y s i n e and the l e v e l of protein on the performance of early-weaned lambs. I I I . Agr. Exp. S t a . , Sheep Day Rpt., DS31. 37« Houpt, T. R. 1959. U t i l i z a t i o n of blood urea i n ruminants. Am. J . Physiol. 197:115-120. 38. Hudson, L. W., H. A. Glimp, C. 0. L i t t l e , and P. G. Woolfolk, 1 9 6 9 . Effect of l e v e l and s o l u b i l i t y of soybean protein on i t s u t i l i z a t i o n by young lambs. J . Animal S c i . 28:279-282. 3 9 . Johns, A?9T. 1955. Pasture quality and ruminant digestion. I I . Levels , i 6 f v o l a t i l e acids and ammonia i n the rumen of sheep on a high production pasture. N.Z. J. S c i . Technol. 3 7 A : 3 2 3 - 3 3 1 . 88. 40. Jordan, R. M. 1966. Effect of energy as supplied by hay or high concentrate rations and frequency of feeding on performance of ewes. J . Animal S c i . 25_: 624-629. 41. Kammlade, W. G., H.-H. M i t c h e l l and B. Sleeter. 1940. Urea as a source of protein f o r sheep. I I I . Univ. C o l l . Agr., Animal Husb. Dept. Sheep Div. Project 1123. 1940 - Cited by Briggs, M. H. 1967. 4 2 . Karr, M. R., U. S. Garrigus, E. E. Ha t f i e l d and H. W. Norton. 1965. Factors a f f e c t i n g the u t i l i z a t i o n of nitrogen from different sources by lambs. J . Animal S c i . 24:459-468. 43. K i l i a n , E. F. 1948. Amidfutterung, Arch. Tierernahr. 10:37 - Cited by Briggs, M. H. 1967. 44. KLosterman, E. W., D. W. B o l i n , M. L. Buchanan, F. M. B o l i n and W. E. Dinusson. 1953. Protein requirements of ewes during breeding and pregnancy. J. Animal S c i . 12:188-200. 45* Land, H. and A. I. Virtanen. 1959. Synthesis of amino acids and proteins from ammonium s a l t s by ruminants. Suam. Maataloust. Seur. Julk. 9_4jl — Cited by Briggs, M. H. 1967. 46. Langlands, J . P., Corbett, J. L., I . McDonald and J . P. P u l l a r . 1963. Estimates of energy required f o r maintenance by adult sheep. Animal Prod. £:l-9. 47. Light, M. R., W. E. Dinusson, R. M. Richard and D. W. B o l i n . 1957. Urea and s t i l b e s t r o l f o r fattening lambs. J. Animal S c i . 15:570-574. 48. Light,M. R. 1966. What baby lambs prefer to eat. Nutr. Abstr. Rev. 3.6:248. 49* Loskutov, A. M. and V. I. Berkovic. 1965• Prolonged feeding with urea and ammonia solution. Nutr. Abstr. Rev. 35:518. 50. McDonald, I . W., 1948. The absorption of ammonia from the rumen of the sheep. Biochem. J . 42:584-587. 51. McLaren, G. A., G. C. Anderson, L. I . Tsai and K. M. Barth. 1965. Level of readily fermentable carbohydrates and adaptation of lambs to a l l - u r e a supplemented rations. J. Nutr. 87:331-336. 52. National Research Council, U. S. A. 1953. B u l l . Nat. Res. Coun. No. 254. Washington, D. C. 53* National Research Council, U. S. A. 1957. Nutrient Requirements of Sheep. Pub. No. 504, Washington, 0. C. 54« National Research Council, U. S. A. 1968. Nutrient Requirements of sheep. Pub. No. 1693, Washington, D. C. 89. 55« Nedkvitne, J . J . 1967. Different winter feeding of ewes. Nutr. Abstr. Rev. 3_£:267. 56. Noble, R. L., L. S. Pope and W. D. Gallup. 1955* Urea and methionine i n f a t t e n i n g rations f o r lambs. J . Animal S c i . 14:132-136. 57. O l i v i e r , P. J . S. and P. J . Cronje. 1964. Theceffeet of the rate of intake of urea upon the nitrogen retention of sheep. S. A f r . J . A g r i c . S c i . 2:?71-778. 58. Otagaki, K. K., 0. Wayman, K. Morita and J . I. Iwanaga. 1956. Rations of mil k i n g cows under Hawaiian conditions. J . Dairy S c i . 39:1753-1758. 59. Owen, E. C , J . A. B. Smith and N. C. Wright. 1943. Urea as a p a r t i a l p r otein substitute i n the feeding of dairy c a t t l e . Biochem. J . 3J7:44. 60. Owen, E. C. 1957. A study of the l a c t a t i o n and growth of h i l l sheep i n t h e i r native environment and under low land conditions. J . A g r i c . S c i . 4J3: 387-412. 61. Pallan, B. and N. Pejovic. 1965. Feeding sheep on hay sprayed with urea. Nutr. Abstr. Rev. 3_5_:225. 62. Peart, J . N. 1968. Some e f f e c t s of l i v e weight and body condition on the milk production of Blackface ewes. J . A g r i c . S c i . 70:331-338. 63. Perry, T. W., W. M. Beeson and C. Harper. 1957. The value of f o r t i f i e d creep rations f o r si n g l e and twin suckling lambs. J . Animal S c i . 16:413. 64. P h i l l i p s o n , A. T. 1959. In, S c i e n t i f i c P r i n c i p l e s of Feeding Farm Livestock, Farmer and Stock Breeder Publications Ltd., London, pp. 105-123. 65. Pieterse, P. J . S., S. F. Lesch, F. J . Dosthuizen and D. P. Le Roux. 1967. The e f f e c t of various supplementary l e v e l s of urea and maize on nitrogen u t i l i z a t i o n by sheep fed poor q u a l i t y roughage. Nutr. Abstr. Rev. _7:6l2. 66. Pogodin, V. N. 1967. E f f e c t of l e v e l of n u t r i t i o n of pregnant Karakul ewes on t h e i r milk production. Nutr. Abstr. Rev. 37:272. 67. Preston, R. L., D. D. Schnakenberg and W. H. Pfander. 1965. Protein u t i l i z a t i o n i n ruminants. I . Blood urea nitrogen as a f f e c t e d by prot e i n intake. J . Nutr. 86:281-288. 68. Ranhotra, G. S. and R. M. Jordan. 1966. Protein and energy requirements of lambs, weaned at s i x t o eight weeks of age as determined by growth and d i g e s t i o n studies. J . Animal S c i . 25:630-635. 90. 69. Ray, E . E . and S. L . Smith. 1966. Effect of body weight of ewes on subsequent lamb production. J . Animal S c i . 25:1172-1175. 70. Repp, W. W., W. H. Hale and W. B . Burroughs, 1955* The value of several non-protein nitrogen compounds as protein substi tutes i n lamb fat tening ra t ions . J . Animal S c i . 14:901. 71. Robinson, J . J . and T. J . Forbes. 1967. A study of the protein requirements of the mature breeding ewe. 2 Protein u t i l i z a t i o n i n the pregnant ewe. B r i t . J . Nutr . 21:879-891. 72. Robinson, J . J . and T. J . Forbes. 1968. The effect of protein intake during gestation on ewe and lamb performance. Animal Prod. 10:297-309. 73. Rust, J . W., C. A. Las s i t e r , G. Davis, L . D. Brown and D. M. Seath. 1956. The u t i l i z a t i o n of dicyandiamide and urea by l a c t a t i n g dairy cows. J . Animal S c i . 15:113-1140. 74. Schaadt, H . J r . , R. R. Johnson and K. E . McClure. 1966. Adaptation to and p a l a t i b i l i t y of urea, b iuret and diammonium phosphate as NPN sources for ruminants. J . Animal S c i . 25:73-77. 75. Schoenemann, K. 1946. Amidfutterung, Arch. Tiercrnahr . 10:37 -Cited by Br iggs , M. H. 1967. 76. S len, S. B . , R. D. Clark and R. Hironaka. 1963. A comparison of milk production and i t s r e l a t i on to lamb growth i n f ive breeds of sheep. Can. J . Animal S c i . 43:16-21. 77. Slen, S. B . and F . Whiting. 1952. Lamb production as affected by l e v e l of protein i n the ra t ion of the mature ewe. J . Animal S c i . 11:166-173. 78. Solovev, L . , A . Manenkova and G. Belova. 1966. Effect of urea i n the feed of cows on the qua l i t y of fermented m i l k s . Nutr. Abs t r . Rev. 3_6:572. 79. Szabo, I . 1965. Farm t r i a l s with urea as a feed. Nutr. Abst r . Rev. 25_:1163. 80. Thomas, W. E . , J . K. L o o s l i , H. H. Will iams and L . A. Maynard. 1951. The u t i l i z a t i o n of inorganic sulfates and urea nitrogen by lambs. J . Nutr . 4J.:515~523. 81. Van Horn, H. H . , R. Hocraffer and C. F . Foreman. 1969. Further evaluation of mi lk production responses from urea treated corn s i l age . J . Dairy S c i . 52:1249-1252. 91. 82. Van Horn, H. H., D. R. Jacobson and A. P. Graden. 1969. Influence of l e v e l and source of nitrogen on milk production and blood components. J . Dairy S c i . 52:1395-1403. 83. Van Horn, H. H., C. F. Foreman and J . E. Rodriguez. 1967. Effect of high-urea supplementation on feed intake and milk production of dairy cows. J . Dairy S c i . 50:709-714. 84. Virtanen, A. I. 1966. Milk production of cows on protein-free feed. Studies of the use of urea and ammonium sa l t s as the sole nitrogen source open new important perspectives. Science 153 :l603 - l6l4. 85. Waite, R. M. E. Castle, J . N. Watson and A. D. Drysdale. 1968. Biuret and urea i n concentrates f o r milking cows. J. Dairy Res. 35: 191-202. 86. Ward, G. M., C. F. Huffman and C. W. Duncan. 1955. Urea as a protein extender f o r l a c t a t i n g cows. J . Dairy S c i . 38:298. 87. Wardrop, I. D. I960. An experimental study of the early weaning of lambs. J. Agric. S c i . __j:133-136. 88. Warren, K. S. 1962. Ammonia t o x i c i t y and pH. Nature. 195:47-49. 89. Watt, G. W. and J . D. Chrisp. 1952. A spectrophotometric method, f o r the . determination of hydrazine. Anal. Chem. 24:2006. 90. Wegner, M. I . , A. N. Booth, G. Bohstedt and E. B. Hart. 1940. J. Dairy S c i . The i n v i t r o conversion of inorganic nitrogen to protein by T'tiii Pro organisms from the cow's rumen. J . Dairy S c i . 23_:1123-1129. 91. Wright, P. L., A. L. Pope and P. H. P h i l l i p s . 1964. Pelleted roughages fo r gestating and l a c t a t i n g ewes. Nutr. Abstr. Rev. 34:254. 92. IX APPENDICES 93. TABLE EXPERIMENT I COMPOSITION OF RATIONS FOR EWES DURING LACTATION Feed No. of Crude % Ash Samples Proteins Grass hay 1 11.4-9 7.2 2 11.64 7.3 Average 11.56 7.2 Alfalfa hay 1 . 14.48 6.7 2 - 6.S Average 14.48 6.7 Beet pulp 1 10.72 7.8 2 10.51 3 9.95 4 9.86 Average 10.26 7.3 Dairy pellets 1 14.08 6.97 2 - 6.90 Average 14.08 6.93 TABLE 3X2 EXPERIMENT I RATION COMPOSITION (FOR WEANED LAMBS) Ration No. of Samples Crude Protein (Protein level) (after analysis) 2 0 % 1 18.9 2 19.7 3 1 9 . 8 16% 1 15.4 2 1 6 . 0 3 1 6 . 1 1 3 % 1 13.0 2 1 2 . 8 3 1 3 . 2 95 TABLE :  A-3. EXPERIMENT I WEIGHT OF EWES (Kg) GROUP I WEIGHT OF EWES BEFORE PARTURITION WEIGHT OF EWES DURING EARLY LACTATION (Weeks of lactation) 7 Weeks Before Pre- Post-No. of Parturition Partum Partum 1st 2nd 3rd 4th 5th 6th 7th 8th Ewes Weight Weight Weight .1 65 69 65 70 72 71 71 74 76 74 74 2 61 75 67 66 70 65 69 68 68 64 63 3 65 73 65 65 64 62 64 62 62 62 59 R •r\ 4 49 53 47 49 45 49 48 48 47 48 47 u U "D 5 60 75 68 67 65 64 62 64 65 66 66 r T 6 57 67 59 63 63 64 61 53 57 55 50 1 7 79 95 79 89 84 81 81 80 80 70 71 8 65 73 68 65 66 67 67 65 64 56 59 9 60 78 71 70 66 64 62 64 65 68 67 10 71 81 79 79 80 79 79 75 76 71 71 11 50 55 50 49 53 58 54 53 55 52 52 12 42 48 a 44 47 45 45 43 42 44 53 13 43 49 41 44 44 40 39 42 38 44 41 14 42 51 44 45 44 46 44 45 43 44 39 15 39 45 42 40 40 43 45 45 4 1 43 43 TABLE A-3 EXPERIMENT I WEIGHT OF EWES (Kg) GROUP I I WEIGHT OF EWES BEFORE PARTURITION 7 Weeks Before Pre- Post-No. of P a r t u r i t i o n Partum Partum Ewes Weight Weight Weight 1 65 76 68 2 56 72 66 3 69 80 74 4 46 55 50 5 42 60 48 6 69 83 76 7 65 80 75 8 85 98 89 9 65 78 73 10 69 82 76 11 43 49 92 12 42 51 46 13 61 80 62 WEIGHT OF EWES DURING EARLY LACTATION (Weeks of lactation) Lst 2nd 3rd 4th 5th 6th 7th 8th 65 62 62 59 59 60 61 57 65 64 62 60 62 66 61 60 70 72 70 70 72 75 74 73 48 4 8 a . 45 50 45 43 4 4 52 50 4 9 4 7 4 4 4 3 42 43 75 74 72 71 6 7 65 6 4 62 72 72 61 7 4 72 71 70 60 87 84 80 79 78 77 76 77 71 70 69 69 66 67 6 7 69 74 71 68 70 68 67 68 71 a 4 0 40 4 0 39 39 38 39 45 43 4 4 42 4 2 40 38 38 68 64 64 62 60 60 54 55 97. ' : • TABLE A-4 EXPERIMENT I SINGLE LAMB GROWTH (PRE-WEANING) WEEKLY WEIGHTS (Kg) l. OF ' BIRTH ANIMALS WEIGHT 1st 2nd 3rd 4th 5th 6th 7th 1 2.7 4.8 6.7 8.4 10.2 12.7 15.4 16.0 2 5.0 7.7 10.5 14.0 16.4 18.1 19.5 21.3^  3 4.0 5.6 7.0 9.3 12.7 16.3 19.0 20.0 4 5.1 7.7 10.9 13.5 15.9 18.6 21.3 22.7 5 4*2 6.5 9.0 11.7 14.5 16.8 20.4 23.1 6 3.7 6.0 •.=8.5 12.2 15.0 17.7 20.0 22.2 7 3.2 4.3 5.9 8.0 10.2 12.2 14.5 16.8 8 3.2 5.5 7.0 8.5 11.3 13.1 15.9 16.3 9 3.0 5.1 7.2 9.3 12.4 14.0 16.0 20.0 GROUP I 1 4 . 0 6.3 7.9 10.0 13.6 15.9 17.2 18.6 2 4.7 6 .0 7.4 11.3 13.2 14-.5 15.9 16.8 3 3.6 5.7 7.4 9.5 12.7 13.2 15.0 15.9 4 4 . 1 6.9 8.7 11.5 13.6 15.0 15.4 16.8 GROUP II 5 4-2 4-7 6.5 9.0 11.8 13.6 15.4 15*4 6 5.7 8.5 11.1 14.5 16.8 19.0 21.3 21.8 7 4 . 0 5.3 7.0 10.0 11.3 13.1 15.4 16.8 8 3.3 5.2 6.6 7.5 9.5 10.9 11.3 13.6 9 4.5 6.7 7.8 7.8 10.0 10.9 13.6 14.5 98. TABLE A-5 EXPERIMENT I TWIN LAMB GROWTH (PRE-WEANING) WEEKLY WEIGHTS (Kg. ) WEEKS NO. OF BIRTH ANIMALS WEIGHT 1 s t 1 2.7 4 . 3 2 2.9 4 . 8 3 4 . 0 4 . 7 4 3.8 4 . 9 1 3.2 4 . 4 2 2.5 3.5 3 3.2 4 . 8 4 3.7 5.5 AFTER BIRTH 2nd 3 r d 4 t h 5th 5.5 7.4 8,5 11.8 6 . 9 8.8 11.0 14.0 5.9 7.5 8.5 11.3 6.0 7.3 8.9 12.2 6.4 7.2 8.4 9.0 5.1 6.2 7.2 8.0 6.0 8.5 10.9 12.7 7.2 8.0 10.0 10.9 6th 7th 8th G 11.8 13.6 15.0 R 0 14-5 16.3 17.7 u p 12.7 14«0 14.0 I 13.8 15.0 16.3 10.6 11.8 11.8 9.3 10.9 11.8 G R 13.6 14.5 15.9 0 u 11.8 12.8 13.6 p I I 99 TABLE A-< EXPERIMENT DRY MATTER DIGESTIBILITY RATION TOTAL D.M. (PROTEIN NO. OF INTAKE FOR LEVEL) ANIMALS 4 DAYS g 20% 1 2175 2 2037 3 2023 4 1754 Average 1997 I OF WEANED LAMBS TOTAL D.M. TOTAL D.M. LOST FOR DIGESTED FOR %. D. M. 4 DAYS 4 DAYS DIGESTED g g 601 1574 72.3 558 1479 72.6 630 1393 68.8 455 1299 74.0 561 1436 71.9 16$ 1 1888 2 1905 3 961 4 1234 Average 1497 \ 13% 1 2115 2 1969 3 2167 4 960 Average 1802 713 1175 62.2 468 1437 75.4 215 746 77.6 414 820 66.4 452 1047 70.4 737 1378 65.1 471 1498 76.0 685 1482 68.3 269 691 71.9 540 1262 70.3 TABLE A-7 • EXPERIMENT I N. DIGESTED AND RETAINED BY WEANED LAMBS RATION (PROTEIN NO. OF LEVEL) ANIMALS 20$ 1 2 3 4 Average TOTAL N. INTAKE FOR •;• 4 DAYS g 83.4 80.6 80.3 72.6 79.2 TOTAL N. LOST IN FAECES FOR 4 DAYS g 9.2 12.0 10.9 12.1 11.0 TOTAL N. DIGESTED FOR 4 DAYS g 74.2 68.6 69.4 60.5 68.1 DIGESTION COEFFICIENT PERCENT 8 8 . 7 8 5 . 1 8 6 . 4 8 3 . 3 8 5 . 8 TOTAL N. TOTAL N. TOTAL N. LOST IN LOST FOR RETAINED N. RETAINED URINE FOR 4 DAYS FOR 4 DAYS (faeces & L DAYS urine) N. DIGESTED g 6 . 2 6 .2 7.5 4.7 6 . 1 g 15.4 18.2 18.4 16.8 17.2 6 8 . 0 6 2 . 4 6 1 . 9 55 .8 6 2 . 0 91.6 90.9 89.1 92.2 90.9 16$ 1 2 3 4 Average 6 6 . 4 6 4 . 7 30.5 41.5 50.6 7.5 9 . 3 6 . 2 5.0 7 . 0 58.9 55.4 23.8 36.5 43.6 88.7 85.6 79.3 87.9 85.3 6 . 9 10.3 3 . 2 3 . 9 6 . 0 14.4 19.6 9.4 8.9 1 3 . 0 52.0 4 5 . 1 2 0 . 6 3 2 . 6 37 .5 8 8 . 2 8 I . 4 86 .5 8 9 . 3 8 6 . 3 13$ 1 2 3 4 Average 60.1 57.2 61.2 28.9 51.8 10.4 8.7 11.9 9.5 10.1 49.7 48.5 49.3 19.4 41.7 82.6 84.7 80.5 67.1 78.7 7 .1 9 . 4 7 .1 2.6 6.5 17.5 18.1 19.0 12.1 16.6 42.6 39.1 42.2 16.8 35.1 85.7 80.6 85.5 86.5 84.5 101. TABLE A-8 EXPERIMENT II PERCENTAGE OF UREA IN RATIONS RATION NO. OF SAMPLES % UREA IN RATION Soybean 1 0.07 2 0.07 3 0.06 Average 0.06 Soybean 1 0.90 &' 2 1.00 Urea 3 0.80 Average 0.90 Urea 1 1.90 2 2.00 3 2.00 Average 1.96 102. TABLE A-9 EXPERIMENT II LAMB GROWTH (Pre-weaning) WEIGHTS IN KGS. SOYBEAN NO. OF BIRTH Weeks after birth _}MBS WEIGHT 1 2 3 4 5 6 7 8 9 1 3.8 6.5 8.4 10.9 34.0 15.9 16.8 19.0 21.3 24.5 2 4.3 6.3 8.4 10.4 15.4 16.3 18.1 22.7 26.8 27.2 3 3.8 5.6 7.9 9.7 11.3 15.9 17.2 19.0 21.3 23.1 4 4.1 5.9 7.5 10.9 13.1 15.0 18.1 20.9 20.9 20.9 5 5.0 7.7 7.9 8.8 10.0 13.1 14.1 18.1 20.9 23.6 6 4.3 5.4 6.1 6.8 8.4 11.3 11.3 16.8 16.8 18.3 7 2.5 4.3 5.4 6.5 7.5 10.4 11.8 13.1 15.9 17.5 8 3.6 5.2 7.5 7.2 8.8 14.0 14.0 14.5 17.2 20.0 9 3.2 5.4 5.4 9.0 10.6 15.0 15.4 17.2 21.8 23.6 10 4.6 6.3 7.2 7.7 8.8 11.8 12.7 15.0 17.5 18.1 11 3.7 4.3 5.2 7.2 8.6 11.8 12.7 14.0 16.8 18.1 Average 4.7 5.7 7.2 8.6 10.5 13.5 14.7 17.3 19.8 21.5 103 TABLE A-9 EXPERIMENT II LAMB GROWTH (Pre-weaning) WEIGHTS IN KGS. SOYBEAN AND UREA NO. OF LAMBS • BIRTH WEIGHT 1 2 3 4 after t 5 6 7 8 9 1 3.1 4.5 5.9 7.2 9.0 13.1 13.1 15.9 17.2 20.0 2 3.1 4.5 5.4 6.8 8.6 12.2 13.1 15.0 16.8 18.6 3 4 . 8 6.8 8.8 10.9 15.0 17.2 19.0 22.2 23.6 25.0 4 3.8 4.5 6.8 7.9 9.0 14.0 15.4 17.2 18.6 22.2 5 3.6 5.0 6.3 7.2 8.8 13.1 \ 14.5 16.3 17.5 19.0 6 4.7 7.9 9.3 12.2 15.9 18.1 19.0 20.9 22.2 24.5 7 4.8 6. 5 8.6 11.1 15.0 16.8 19.0 20.9 23.6 27.2 8 3.6 5.0 6.5 7.2 10.0 12.7 15.0 17.2 19.0 21.8 9 4 . 1 6.3 9.3 11.3 14.3 17.7 20.0 25.0 26.8 30.0 10 4 . 4 6.5 8.1 9.7 13.1 15.9 17.2 19.0 22.2 25.4 11 4.8 7.0 8.8 11.3 16.8 17.7 19.0 22.2 24.5 28.6 Average 4 . 0 5.9 7.6 9.0 12.3 15.3 16.8 19.3 19.9 23.8 TABLE A-9 EXPERIMENT II LAMB GROWTH (Pre-weaning) WEIGHTS IN KGS. UREA NO. OF BIRTH Weeks after birth-JAMBS WEIGHT 1 2 3 4 5 6 7 8 9 1 3.0 4.5 5.6 6.8 9.5 11.3 14.0 15.9 18.1 20.0 2 3.5 5.4 6.3 7.9 11.3 12.7 15.0 16.3 18.6 20.9 3 4.0 6.1 7.2 8.8 12.2 13.6 16.3 17.5 20.4 22.7 4 3.4 5.6 6.3 8.1 12.2 13.1 15.9 17.5 20.0 22.7 5 4.5 8.1 9.0 12.2 15.0 17.7 20.9 22.2 25.4 29.5 6 3.6 5.0 6.1 8.1 12.2 13-1 15.0 16.8 18.6 20.4 7 4.3 5.4 6.5 8.4 12.2 14.0 16.3 17.5 20.4 23.6 8 4.7 6.8 8.1 11.3 14.0 19.0 20.4 23.1 26.8 29.0 9 4.5 7.2 9.0 11.8 15.4 16.8 19.0 21.7 23.6 27.2 10 4.9 7.7 9.0 12.2 15.4 17.7 19.0 21.3 26.3 28.1 11 4.0 6.5 8.4 11.5 14.0 16.3 19.0 23.1 26.8 23.6 Average 4.0 6.2 7.5 9.7 13.0 15.0 17.4 19-4 22.2 24.8 105 TABLE A-10 EXPERIMENT II EWES PLASMA UREA N. (mg. urea N/100 ml.) UREA NO. OF • -r ANIMALS 1st 2nd 1 27.9 40.1 2 34.1 20.1 3 29.4 35.8 4 38.7 26.3 5 34-1 38.9 6 29.4 32.5 7 21.7 35.6 8 27.1 34.2 9 34.4 37.2 Weeks of Lac-3rd 4th 5th 34.5 20.1 41.8 33.3 34-1 24.8 31.1 38.7 62.0 39.5 4 4 . 9 62.0 28.2 23.2 26.3 36.4 37.2 46.8 39.3 37.2 "37.2 31.0 31.0 62.0 49.6 38.9 62.0 6th 7th 8th 15.5 27.9 35.6 18.6 34.1 41.8 38.4 34.3 35.6 35.6 43.4 46.5 49.6 38.7 44.9 33.3 31.0 39.3 39.3 32.5 31.3 27.1 30.2 35.6 38.4 33.3 41.8 Average 30.7 33.4 35.8 33.9 47.2 32.8 33.9 39.1 106 TABLE A-10 EXPERIMENT II EWES PLASMA UREA N. (mg. urea N/lOO ml.) SOYBEAN AND UREA . OF MAIS 1st 2nd 3rd Weeks 4th of Lactat 5th ion 6th 7th 8th 1 23,2 19.6 . 18.6 20.9 45.4 20.9 14.6 24.8 2 19.3 36.4 37.2 41.8 34.8 35.6 27.1 34.1 3 27.1 27.1 24.8 24.8 58.1 26.3 37.2 36.4 4 27.9 33.3 15.5 10.8 31.0 16.3 24.0 27.9 5 21.7 33.3 21.7 24.0 55.8 20.9 23.2 31.0 6 17.0 31.3 40.3 29.4 55.8 39.3 24.8 41.8 7 23.2 34.1 34.1 28.0 49.6 30.2 24.8 26.3 8 29.4 23.2 21.7 20.1 43.7 34.1 41.8 41.8 9 24.0 24.8 35.6 28.0 31.1 27.1 18.6 38.7 Average 23.7 29.2 27.7 25.3 45.0 27.8 27.0 33.6 107 TABLE A-10 EXPERIMENT II EWES PLASMA UREA N. (mg. urea N/lOO ml.) SOYBEAN . OF -Weeks of lactation-— — _ _ _ _ EMALS 1st 2nd 3rd 4 t h 5th 6 t h 7 t h 8 t h 1 27.9 31.0 28.0 31.0 31.0 31.0 19.6 25.7 2 24.0 31.0 21.7 24.6 31.0 24.8 13.9 24.8 3 26.3 31.0 24.8 17.8 31.0 31.0 , 21.7 30.0 4 29.7 28.0 31.0 31.0 31.0 26.6 18.6 26.3 5 23.2 27.9 27.9 23.2 31.0 31.0 21.7 27.0 6 21.7 23.2 27.9 29.4 27.2 27.4 24.8 29.4 7 30.2 31.0 31.0 31.0 31.0 31.0 18.4 29.4 8 20.1 24.8 31.0 31.0 31.0 24.8 15.5 24.8 9 31.0 ,31.0 31.0 25.1 31.0 31.0 17.0 26.3 Average 26.0 28.9 28.2 27.1 30.5 28.7 19.0 27.1 108 TABLE A-11 EXPERIMENT II EWES MILK UREA N (MG. UREA N/lOO ML.) Weeks of Lactation NO. OF ANIMALS 1 s t 2nd * 3 r d 4 t h 5th 6 t h 7 t h 8th RATION 1 5.1 10.0 1.0 5.0 1.1 5.0 3 . 0 2.5 2 1.1 0.8 3.2 0.0 0 . 0 3.0 4 . 0 1.5 Soybean . 3 0.1 5.3 2.0 2.1 0 . 0 0 . 0 1.6 2.2 Average 2.1 5.3 2.0 2.3 0.3 2.6 2.8 2.0 1 0 . 0 3.3 0.7 0.0 0.0 2.0 2.5 5.0 2 0.5 6,5 9.5 2.5 2.5 4.7 4.5 7.0 Soybean & . 3... 0.1 4 . 6 1.3 0.0 1.5 0 . 0 6.7 6.5 Urea Average 0.2 4 . 8 3.8 0.8 1.3 2.2 4 . 5 6.1 1 3.1 11.6 4 . 0 9.0 4 . 7 4 . 1 4 . 2 4 . 0 2 1.5 6.0 0.7 4.5 0.7 4.5 5.5 7.0 Urea 3 6.0 5.1 Dead Average 3.5 7.5 2.3 6.7 2.7 4 . 3 4 . 8 5.5 109 TABLE A12 EXPERIMENT II DRY MATTER DIGESTIBILITY OF WEANED LAMBS RATION NO. OF ANIMALS TOTAL D.M. INTAKE FOR 5 DAYS TOTAL D.M. OUTGO FOR •;; 5 DAYS TOTAL D.M. DIGESTED %. D. M. DIGESTED Soybean 1 2 Average 4529 4329 4429 1875 1692 1783 2654 2637 2645 58.6 60.9 59.7 Soybean & Urea 1 2 Average 4529 4192 4360 2390 1251 1820 2139 29a 2540 47.2 70.1 58.6 Urea 1 2 Average 3264 4128 3696 1284 1556 1420 1980 2572 2276 60.6 62.3 61.4 TABLE A-13 EXPERIMENT I I N. DIGESTED AND RETAINED BY WEANED LAMBS TOTAL Ni TOTAL N. DIGESTION TOTAL N. TOTAL N. TOTAL N. N. INTAKE LOST IN DIGESTED COEFFICIENT LOST IN LOST RETAINED NO. OF FOR FAECES FOR FOR PERCENT URINE FOR DURING FOR N. RETAINED RATION ANIMALS 5 DAYS 5 DAYS 5.DAYS 5 DAYS 5 DAYS 5 DAYS N.DIGESTED (faeces . % g ; V g g % g & g . . . . . urine) Soybean 1 45.2 20.0 25.2 55.7 4 . 0 24.0 21.2 84.1 2 43.2 16.3 26.9 62.2 5.0 21.3 21.9 80.7 Average 44.2 18.1 26.0 58.9 4 . 5 22.6 21.5 82.4 Soybean 1 45.2 15.9 29.3 64.8 7.9 23.8 21.4 73.0 Urea 2 41.8 13.8 28.0 66.9 7.5 21.3 20.5 73.2 Average 43.5 14.8 28.6 65.8 7.7 22.5 20.9 73.1 1 32.5 5.4 27.1 83.3 10.2 15.6 16.9 62.3 Urea 2 41.2 10.1 31.1 75.4 10.9 21.0 20.2 64.9 Average 36.8 7.7 29.1 79.3 10.5 18.3 18.5 63.6 TABLE A - H LAMBS PLASMA UREA B (MG i UREA K/lQQ ML,) KO. OF ANIMALS 1 2 1 15.9 26.0 2 41.0 41.5 3 20.0 28.0 4 23.0 25.9 5 32.6 40.0 Average 26.3 32.2 1 18.0 22*1 2 24.0 29.5 3 • 20.1 ,28.1 4 20.0 29.5 5 16.5 ,29.5 Average i.9.7 27.7 1 18.0 28.5 2 23.5 25.0 3 17.0 20.1 4 23.0 29.0 5 24.2 27.7 Average 21.1 26.6 3 , 4 RATION 27.0 38.0' 4380 24,0 Soybean 29.0 24.0 25.9 24.0 40.0 30.0 32,5 27.2 24.0 26.0 29,5 20.0, Soybean 29.0 , 21.5 . ' 28,5 24.0 Urea 29,5 4 22.0 28.1 22.7 29.0 20.0 28.0 20.0 20.0 20*0 Urea 30.0 20.1 27.9 20.1 26,9 20.0 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            data-media="{[{embed.selectedMedia}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
https://iiif.library.ubc.ca/presentation/dsp.831.1-0102047/manifest

Comment

Related Items