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Efficiency of protein utilization by growing chinchilla fed two levels of protein. Rogier, John Charles 1971

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EFFICIENCY OF PROTEIN UTILIZATION BY GROWING CHINCHILLA FED TWO LEVELS OF PROTEIN  by JOHN CHARLES ROGIER B.Sc, University of British Columbia, 1965  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in the Department of Animal Science  We accept this thesis as conforming to the required standard  THE UNIVERSITY OF BRITISH COLUMBIA October, 1971  In p r e s e n t i n g  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the requirements f o r  an advanced degree a t t h e U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y  a v a i l a b l e f o r r e f e r e n c e and study.  I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e  copying of t h i s  thesis  f o r s c h o l a r l y purposes may be g r a n t e d by t h e Head o f my Department o r by h i s r e p r e s e n t a t i v e s .  I t i s understood that copying o r p u b l i c a t i o n  of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my written permission.  Department o f  /A /Vwwi  J k  The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada  Date  iii  ABSTRACT Six male and six female chinchilla (Chinchilla lanigera) in the late phase of growth were used to study the effects of sex, crude protein level in the ration and duration of experiment on body weight gains, digestibility of energy, dry matter, organic matter and protein and efficiency of protein u t i l i z a t i o n , as measured by biological value and net protein u t i l i z a t i o n . Two isocaloric rations of differing crude protein content (16.25% and 19.56%) were supplied ad libitum for three one-week experimental periods. The results showed that female chinchilla had significantly (P<0.05) greater body weight gains than males after adjustment for i n i t i a l body weight and feed intake. There was a significant (P<0.05) effect of ration on the digestibility coefficients studied.  The mean apparent digestibility  coefficients for energy, dry matter, organic matter and protein for ration 1 (16.25% crude protein) were 65.09, 66.44, 67.73 and 62.83%, respectively; while for ration 2 (19.56% crude protein) the values were 67.32, 68.52, 70.21 and 73.23%, respectively.  On the other hand, sex  had no significant (P<0.05) effect on digestibility. There was a significant (P<0.05) effect of ration on the protein u t i l i z a t i o n indices studied.  Biological value was not significantly  (P<0.05) different for the two rations.  The mean values for biological  iv  value and net protein u t i l i z a t i o n f o r r a t i o n 1 (16.25% crude protein) were 66.38 and 42.02%, respectively; while f o r r a t i o n 2 (19.56% crude protein) the values were 66.96 and 48.17%, respectively.  On the other  hand, sex had no s i g n i f i c a n t (P<0.05) e f f e c t on protein u t i l i z a t i o n . The  s e n s i t i v i t y of growing c h i n c h i l l a to protein q u a l i t y suggests  a major r o l e f o r prececal digestion and absorption  although t h i s does  not preclude the synthesis and subsequent breakdown of microbial protein i n the postcecal part of the gut.  TABLE OF CONTENTS Page TITLE PAGE  i  ABSTRACT  i i i  TABLE OF CONTENTS  v  LIST OF TABLES  vii  LIST OF FIGURES  viii  ACKNOWLEDGMENTS  ix  I. II.  INTRODUCTION  1  LITERATURE REVIEW  2  A. The Animal: Chinchilla lanigera 1.  B.  General  2 2  2. Nutritional Physiology  2  Protein Utilization i n the Whole Animal  4  1. Physiological State and Protein Reserves . . .  5  2.  5  Caloric Intake a. b. c.  The Effects of Constant Protein Levels with Varying Energy Intake .  6  The Effects of Constant Energy Levels with Varying Protein Intake  6  The Effects of Carbohydrate and Fat on Protein Utilization  7  3.  Essential Amino Acid and Total Nitrogen Intake  7  4.  Amino Acid Imbalance  8  C. Methodology of Evaluation of Protein Utilization . 1. Weight Gain Method 2. Nitrogen Balance  9 9 10  vi Page III.  EXPERIMENTAL A. Object of Research . . . . . . . . .  11  B. Experimental Approach  11  C. Experimental Design  12  D.  Materials  12  1. Animals  12  2. Housing  14  3. Rations  14  Methods  16  1. Data Collections  16  2. Chemical Analysis  17  3. Statistical Analysis  17  Calculations  19  1. Apparent Digestibility . . . .  19  2.  20  E.  F.  G.  V. VI.  Biological Value  3. Net Protein Utilization  21  Results and Discussion  21  1. Formulation and Chemical Composition of Rations  21  2. Body Weight Gains  21  3. Digestibility Coefficients  25  4. IV.  11  Biological Value, Net Protein Utilization  CONCLUSIONS BIBLIOGRAPHY APPENDIX  . .  27 32  .  33 39  vii LIST OF TABLES Table  Page  1  Design of Experiment  13  2  Formulation of Experimental Rations  22  3  Chemical Composition of Experimental Rations  23  4  Least Squares Means of Weekly Body Weight Gains Adjusted for I n i t i a l Body Weight and Type of Nutrient Intake  24  Least Squares Means of Digestibility Coefficients Adjusted for Nutrient Intake and I n i t i a l Body Weight  26  Least Squares Means of Protein Utilization Indices Adjusted for Protein Intake and I n i t i a l Body Weight  28  5  6  viii LIST OF FIGURES Figure 1  Page Photograph of a Digestibility Cage  15  ix  ACKNOWLEDGMENTS  During this study I became indebted to a number of people. Dr. R. M. Beames, Department of Animal Science, directed the project. Dr. W. D. Kitts, Department of Animal Science, provided financial support and allowed the use of the necessary f a c i l i t i e s . Dr. R. C. Fitzsimmons, Department of Poultry Science, Dr. L. E. Lowe, Department of Soil Science, Drs. W. D. Kitts and C. R. Krishnamurti, Department of Animal Science, offered many helpful suggestions during the preparation of the manuscript. Dr. R. G. Peterson and Mr. C. J. Williams of the Department of Animal Science assisted with the s t a t i s t i c a l analysis of the data.  EFFICIENCY OF PROTEIN UTILIZATION BY GROWING CHINCHILLA FED TWO LEVELS OF PROTEIN  I.  INTRODUCTION  Information on the biology of the chinchilla i s scarce. To date, chinchilla research has been focussed on studies of metabolic rate (13), reproductive physiology (22) and the biochemistry of digestion (52).  A few nutritional investigations have been reported  (28, 31, 32). Nutritional requirements duction are unknown.  for maintenance, growth and repro-  At the present time i t i s standard commercial  practice to feed the same diet to a l l animals regardless of their stage i n production.  In particular, information on protein nutrition  i s lacking (32). The purpose of this study i s to measure the efficiency of protein u t i l i z a t i o n and to establish the protein requirements of chinchilla i n the late phase of growth.  II.  A.  1.  LITERATURE REVIEW  The Animal:  C h i n c h i l l a lanigera  General C h i n c h i l l a were introduced into North America about f i f t y years  ago.  Since then, there has been a rapid increase i n t h e i r numbers due  to t h e i r importance as a luxury f u r animal.  At present there are  approximately 16,000 animals i n B r i t i s h Columbia  (17).  B i c k e l (3) measured the growth curve of C h i n c h i l l a lanigera. The average weight of adult males on a ranch d i e t i s about 475 g, with females weighing approximately 50 g more (3, 28).  Most animals reach  mature weights at approximately nine to eleven months of age (53). 2.  N u t r i t i o n a l Physiology The c h i n c h i l l a i s a nonruminant herbivore with a large cecum.  The r o l e of the cecum as a possible s i t e of fermentation, digestion and absorption i n the c h i n c h i l l a and other nonruminant herbivores, such as the rabbit and the horse, was, u n t i l recently, poorly defined. Smith (52) found that i n c h i n c h i l l a the main s i t e s of c e l l u l o s e breakdown were the cecum and the large i n t e s t i n e .  Although low l e v e l s of  v o l a t i l e f a t t y acids were found i n the stomach and small i n t e s t i n e , these have been attributed to coprophagy (52).  It i s generally assumed  3  that i n the r a b b i t , feces-eating i n conjunction with fermentation i n the l a r g e i n t e s t i n e probably provides insurance against e s s e n t i a l amino acid d e f i c i e n c y and may permit further d i g e s t i o n of f i b e r and other n u t r i e n t s by a second passage through the d i g e s t i v e t r a c t (54). To date, the importance of the cecum i n the p r o t e i n n u t r i t i o n of the nonruminant herbivore has been studied only i n the horse (24, 44).  Although some r e s u l t s suggest that the major s i t e of p r o t e i n  d i g e s t i o n i s prececal they also demonstrate  that there i s a s i g n i f i c a n t  amount of n i t r o g e n absorbed from the lower gut.  I f the major s i t e of  p r o t e i n d i g e s t i o n i s the small i n t e s t i n e , the p r o t e i n q u a l i t y of the d i e t would be an important consideration f o r the growth of young f o a l s . On the other hand, i f the major s i t e of protein d i g e s t i o n i s the cecum the q u a l i t y of the d i e t a r y p r o t e i n would be of l e s s  importance.  The f a c t that mature rabbits (26), horses (24) and c h i n c h i l l a (17, 25) have been maintained on low q u a l i t y forages would i n d i c a t e that the q u a l i t y of dietary p r o t e i n i s not of great importance f o r maintenance.  Growing animals, however, are found to be more responsive  to p r o t e i n q u a l i t y than adults because the amino acid requirements f o r growth are much greater than those f o r maintenance (43).  For example,  Hintz et a l . (23) found that young horses fed d i e t s containing milk products, a good source of amino acids, grew much f a s t e r than animals fed d i e t s containing poorer q u a l i t y proteins.  On the other hand, i t  i s p o s s i b l e that the maintenance requirements of amino acids i n the nonruminant herbivore can be met by b a c t e r i a l synthesis followed by enzymatic degradation and absorption of amino acids i n the lower gut (24,54).  4 Commercial chinchilla diets normally consist of pellets supplemented with hay or a l f a l f a (25).  The ingredients of the pellets are  usually cereal grains, a l f a l f a and a source of good quality protein (25).  Brickel (3) recommended the use of hay as a source of roughage  in addition to pellets.  This combination was reported to reduce the  incidence of digestive upsets observed when only pelleted rations were fed.  On the other hand, Farmer (14) reported that animals per-  formed satisfactorily when fed pellets only.  B.  Protein Utilization i n the Whole Animal  Since there are no reports on work specifically designed to evaluate the u t i l i z a t i o n of protein by chinchilla, this topic w i l l be discussed i n terms of work done with other animals. The requirement for protein i s not for protein as such, but for specific amounts and proportions of the essential and nonessential amino acids (43).  The animal synthesizes proteins and other nitrogenous  compounds from the amino acids.  However, protein synthesis can take  place only i f energy needs are met; i f they are not, dietary protein is used to meet the primary need of the body which is for energy. The technique most commonly employed to evaluate specific amino acid and total nitrogen requirements i s the nitrogen balance (43). Several interacting factors affect the interpretation of nitrogen balance data.  Among the most important of these factors are physiological  state, protein reserves, caloric value of the diet and the levels of essential and nonessential amino acids in the diet.  5 1.  Physiological State and Protein Reserves A positive nitrogen balance is characteristic of a growing  animal.  It i s an indication of the degree of protein synthesis  occurring i n the animal (11).  Increased nitrogen retention i s also  exhibited during protein repletion of animals depleted of labile protein (56).  In this latter case, the extent of positive balance  reflects the extent of protein depletion (1).  In the case of animals  in a negative nitrogen balance the reverse pattern is exhibited. 2.  Caloric Intake The effect of caloric intake on nitrogen balance has been widely  reported (1).  If energy intake i s reduced below a c r i t i c a l level,  caloric intake rather than nitrogen intake becomes the limiting factor in nitrogen balance.  The u t i l i z a t i o n of protein for energy purposes  is indicated by an increased nitrogen excretion (58).  This means that  the primary function of protein, which i s , tissue synthesis, can take place only i f the energy needs of the animal are met.  Conversely, i f  nitrogen excretion i s reduced when energy intake i s increased then protein previously used to meet energy requirements i s now used for protein synthesis (40). Several workers have studied the relationship between protein u t i l i z a t i o n and energy intake in rats and man (4, 5, 7, 8, 9). The effects of constant protein levels with varying energy intake and the effects of constant energy levels with varying protein intake were investigated, as well as the effects of carbohydrate and fat on protein utilization.  6 (a)  The Effects of Constant Protein Levels with Varying Energy Intake  As caloric intake increases, with protein intake held constant, protein u t i l i z a t i o n as measured by carcass analysis increases to a maximum, beyond which no additional protein utilization occurs (7). On the other hand,animals restricted in energy intake below the maintenance level f a l l into a negative nitrogen balance.  The extent of the  negative balance i s related to the degree of caloric restriction (9). Any increase in nitrogen excretion on an energy-deficient diet is the result of the breakdown of dietary and labile protein to meet energy demands. If the degree of caloric restriction i s limited, the i n i t i a l loss of body nitrogen w i l l diminish indicating an adaptation to caloric restriction through a reduction of metabolic activity (38). For example, Bosshardt (4) found that in growing rats a 34% decrease in energy intake resulted in a 14% decrease in energy expenditure.  It  would appear that an animal can regulate nitrogen balance by adjusting metabolism. (b)  The Effects of Constant Energy Levels with Varying Protein Intake As protein intake increases with caloric intake held constant,  protein utilization increases to a maximum rate after which the rise becomes progressively smaller (43). i s t i c for each protein (38).  The rate of decrease is character-  Calloway and Spector (9) have shown that  the nitrogen utilization in rats diminished from approximately 55% to 17% when the level of dietary nitrogen increased from 75 mg to 604 mg daily.  7 (c)  The E f f e c t s of Carbohydrate and Fat on P r o t e i n U t i l i z a t i o n Carbohydrate has an e f f e c t on protein u t i l i z a t i o n which i s  d i s t i n c t from i t s c a l o r i g e n i c function (43). e f f e c t which cannot be taken by f a t .  It has a protein-sparing  In d i e t s adequate i n p r o t e i n and  energy, the replacement of carbohydrate c a l o r i e s by f a t c a l o r i e s r e s u l t s i n an increase i n nitrogen excretion (55).  Thomson and Munro  (55)  suggest that t h i s i s due to the removal of carbohydrate rather than to an adverse e f f e c t of feeding f a t with the p r o t e i n . According  to Munro, evt _al. (39),  the mechanism through which  carbohydrate has an e f f e c t on p r o t e i n u t i l i z a t i o n may  be r e l a t e d to  the f a c t that carbohydrate, but not f a t , i s responsible f o r a temporary drop i n plasma amino acids with the amino acids being deposited i n muscle.  They suggested that the agent causing the s h i f t of amino  acids i n t o muscle i s i n s u l i n ,  whether the i n s u l i n has a protein-sparing  e f f e c t by increasing the permeability of the muscle c e l l membrane to amino acids or whether the hormone has an e f f e c t on polypeptide t h e s i s w i t h i n the c e l l has not been elucidated 3.  syn-  (33).  E s s e n t i a l Amino Acid and T o t a l Nitrogen Intake If energy and other nutrient intakes are adequate, nitrogen  balance i s dependent p r i m a r i l y on (i)  the amounts and proportions of e s s e n t i a l amino acids supplied by the d i e t ,  (ii) The  (43):  and  the t o t a l nitrogen intake.  i n t e r r e l a t i o n s h i p between amino acid composition  of the d i e t  and  8 t o t a l nitrogen intake was i l l u s t r a t e d i n early studies by Sherman (50). He showed that replacement of 10% of the protein i n a c e r e a l d i e t by milk r e s u l t e d i n a marked decrease i n the t o t a l nitrogen requirement necessary to maintain nitrogen equilibrium.  Evidence of the importance  of amino a c i d composition, expressed as b i o l o g i c a l value, on the t o t a l p r o t e i n requirement was also presented by Bricker (6). The requirement f o r the e s s e n t i a l amino acids i s generally considered (6).  the main f a c t o r i n the determination  of p r o t e i n requirement  I t i s becoming i n c r e a s i n g l y obvious that nonessential amino acids  also play an important r o l e . r e l a t i v e proportions  Several studies (50, 53) suggest that the  of e s s e n t i a l and nonessential amino acids i n the  d i e t are more important than has been supposed.  4.  Amino Acid Imbalance In p r o t e i n n u t r i t i o n i t i s important to d i s t i n g u i s h between amino  acid d e f i c i e n c y and amino acid imbalance.  Amino acid d e f i c i e n c y r e f e r s  to a p r o t e i n of low b i o l o g i c a l value which can be improved by the addition of one or more of the l i m i t i n g amino acids.  On the other hand, amino a c i d  imbalance (20) r e f e r s to an already d e f i c i e n t protein which i s made even more d e f i c i e n t by the addition of one or more amino acids. The s i g n i f i c a n c e of amino a c i d imbalance i n p r o t e i n n u t r i t i o n i s somewhat vague (43).  I t seems p o s s i b l e that supplementing an already  poor p r o t e i n with c e r t a i n amino acids or proteins could have detrimental effects.  The e f f e c t s of feeding a combination of low q u a l i t y proteins, as  i s the case i n many human and animal d i e t s , require further i n v e s t i g a t i o n .  9  C.  Methodology of the Evaluation of Protein Utilization  The relative usefulness of the protein of a particular feed i n meeting the animal's protein needs is often referred to as i t s quality (12).  Methods for the evaluation of protein quality in foods have  been reviewed frequently (37, 40).  It i s generally accepted that  biological evaluation, as distinct from chemical and microbiological evaluation, is the most reliable method for determining protein quality since i t i s the ability of a protein to support maintenance and growth that determines i t s ultimate value (43). Many methods are available for the biological evaluation of proteins.  No attempt w i l l be made to discuss a l l methods which have  been reported.  This review w i l l be concerned with some of the more  common methods for assessing the efficiency of protein utilization (10, 35, 43). 1.  Weight Gain Method The rate of growth of an animal under defined conditions provides  a relatively simple way of measuring the value of dietary protein (43). If the diet contains insufficient amounts of one or more of the essential amino acids or i f i t i s lacking in total nitrogen, growth w i l l be severely reduced.  Thus growth i s a sensitive index of the amount and proportions  of amino acids assuming that a l l other nutrients are adequately supplied. Although the weight gain method or feeding t r i a l requires a relatively long period of time and provides l i t t l e information on the metabolism of  10 protein (10), i t is s t i l l the most useful way of obtaining results which have a direct application to feeding practice (34). 2.  Nitrogen Balance A determination of the nitrogen in the food and excreta under  controlled conditions provides a quantitative measure of the protein metabolism and specifically shows whether the body i s gaining or losing protein (34).  A nitrogen-balance experiment involves a record of  nitrogen consumed and nitrogen voided in the feces and urine.  The  nitrogen-balance method is used to determine the protein requirements for various body functions and to study the efficiency of protein utilization by the animal. The results of the nitrogen balance are used to calculate nutritional indices that provide a measure of protein utilization.  The more  commonly used indices are biological value and net protein utilization (43, 35).  Biological value i s a measure of nitrogen retained for growth  or maintenance and is expressed as nitrogen retained divided by nitrogen absorbed (36).  Net protein utilization is a measure of both the  digestibility of the food protein and the biological value of the amino acid mixture absorbed from food (43).  Net protein utilization represents  the proportion of food nitrogen retained, whereas biological value represents the proportion of absorbed nitrogen retained.  III.  A.  EXPERIMENTAL  Object of Research  The efficiency of utilization of dietary protein in nonruminant herbivores depends on the site of protein digestion and (23, 46).  absorption  If the protein is digested and absorbed i n the small intes-  tine, the protein quality of the diet would be as important for the growth of the chinchilla as any other monogast.  On the other hand, i f  a significant amount of nitrogen reaches the cecum and is subjected to the degradative and synthetic action of cecal microorganisms the i n gested nitrogen can be converted into microbial protein prior to possible proteolytic digestion in the lower gut (45).  In that case the  chinchilla would be similar to the ruminant and not dependent on the diet for essential amino acids. The object of this research is to measure the efficiency of protein utilization and to establish the protein requirements of chinc h i l l a in the late phase of growth.  B.  Experimental Approach  Practical feeding experiments and nitrogen balance studies are common methods for assessing the efficiency of protein utilization (10,  12 35, 43).  In this study a feeding t r i a l was run during which digesti-  b i l i t y and nitrogen balance measurements were taken on male and female chinchilla in the late phase of growth.  To investigate the suitability  of the rations and other experimental conditions the experiment was conducted over three consecutive one-week periods.  C.  Experimental Design  The experiment was designed as a 2 x 2 x 3 factorial.  The  effects of sex, two levels of crude protein (16.25% and 19.56%) and time (3 consecutive one-week experimental periods) on protein u t i l i z a tion i n chinchilla during the late phase of growth were investigated. Three individually-caged animals were allocated per treatment.  The  treatments are described in Table 1. The following performance traits were calculated and analyzed by the least squares method of Harvey (21): body weight gains, digestib i l i t y coefficients (energy, dry matter, organic matter and protein), biological value and net protein utilization.  D. 1.  Materials  Animals The animals used were Chinchilla lanigera born and raised at The  University of British Columbia Chinchilla Unit.  Twelve young adult  chinchilla with mean body weight of 460 g at start of feeding were  Table 1 Design of Experiment Treatments^ Sex Female  Rations  Periods  16.25% protein  Week 1  II  II  Week 2  II  II  Week 3  Female  19.56% protein  Week 1  ti  II  Week 2  ti  II  Week 3  Male  16.25% protein  Week 1  it  it  Week 2  ii  II  Week 3  Male  19.56% protein  Week 1  II  II  Week 2  II  it  Week 3  Three individually-caged animals per treatment  14 randomly assigned to two rations with three males and three females per ration.  A l l animals were between 6 and 8 months of age and kept  under the same conditions of feeding and housing prior to experimentation.  A l l animals were i n good health throughout the experimental  period. The experiment proper was started after a ten day acclimation period during which time the animals became accustomed to routine experimental procedures. 2.  Housing Animals were randomly and individually allocated to galvanized  wire mesh cages (15" x 18" x 12") with 1/2" mesh spacing. A l l cages were equipped with a stainless steel urine-feces collecting funnel. An extra fine (6 mesh per cm) wire screen was placed on top of the funnel to ensure the separation of feces and urine. one of the digestibility cages i s shown i n Figure 1.  A photograph of A dustbath, con-  sisting of pulverized rock, was provided twice a week for fur-cleansing purposes.  Small blocks of f i r for gnawing and fresh drinking water were  available at a l l times.  The animals were kept at The University of  British Columbia Chinchilla Unit i n a temperature-controlled room (20°C ± 1°C) and i n natural illumination. 3. Rations The experimental rations were fed i n pelleted form ad libitum. The two rations were isocaloric but of differing crude protein content.  The control ration consisted of a commercial chinchilla feed  Figure 1  Photograph of a d i g e s t i b i l i t y cage  16 (National Feeds Ltd., Abbotsford, British Columbia) which was ground and repelleted.  The other ration was formulated by replacing one-tenth  of the control ration with fat-extracted soybean meal (48.5% protein). Soybean meal was used as the protein supplement because i t i s an excellent source of amino acids for nonruminants herbivores (23). The composition and proximate analysis of the test rations are given in Table 2 and Table 3, respectively.  E. 1.  Water was supplied ad libitum.  Methods  Data Collections (a)  Body Weights  A l l animals were weighed at the beginning and end of each of the three one-week experimental periods. (b)  Feed Intake  Individual food consumption was measured every day and totalled for each week. No appreciable food wastage occurred. (c)  Feces Feces were collected daily from the fine wire screen described  in the section on housing, a i r dried, and stored at room temperature. The weekly output was pooled for each animal.' (d)  Urine  Urine was collected under a toluene layer (3 drops per 250 ml erlenmeyer flask) to prevent interaction between the urine and the  17  atmosphere).  Sulphuric acid (1 ml of 50% H^SO^) was added to the  collection flask as a preservative.  Daily collections were stored i n  a freezer (-11°C) and the weekly output was pooled for each animal. 2.  Chemical Analysis (a)  Dry Matter Feed and fecal dry matter were determined on samples of air-dry  material which were ground and mixed prior to drying at 85-90°C to a constant weight. (b) Gross Energy Gross energy values of feed and feces were obtained by combustion in a Gallenkamp^" adiabatic oxygen bomb calorimeter (18). (c)  Crude Protein Crude protein content determinations were made on feed, feces and  urine samples using the o f f i c i a l A.O.A.C. procedure (2). Nitrogen content was converted to crude protein by multiplying by 6.25 (34). (d) Ash Ash determinations were done on oven dry feed and feces by dry ashing samples according to the o f f i c i a l A.O.A.C. procedure (2). 3.  Statistical Analysis A least squares analysis developed by Harvey (21) was used to  estimate the effects of sex, ration and time and a l l interactions on the performance traits mentioned earlier (see III. C. Experimental Design).  Gallenkamp, London, E.C. 2.  18 I n i t i a l body weight and feed intake were used as covariables to adjust performance traits studied for differences due to these factors. The linear mathematical model assumed was:  Y  ijkl  =  °  +  b  S  B  i  +  r  ijkl  j  \  +  +  f  F  +  ( s r  ijkl  >ij  +  e  +  ( 8 t )  ik  +  ( r t )  jk  +  ( 8 r t )  ijk  +  ijkl'  where: Y., ijkl  = The observed value of the various performance traits under study of the l*"* animal of the i*"* sex on the j*"* ration 1  1  1  til during the k a s. x  week of the experiment,  :  = The population mean for the trait under study. til = The effect of the i sex. th = The effect of the j ration. = The effect of the k*"* week.  (sr).. ij  til til = The joint effect of the i sex on the j ration when the  r.J t, k  1  effects of sex and ration are held constant. (st)_j^  =  The joint effect of the i  t  b  sex during the k ^ week when  the effects of sex and time are held constant. (rt)., jk  = The joint effect of the j ^ ration during the k*"** week f c  when the effects of ration and time are held constant. (srt) .  til til = The joint effect of the i sex on the j ration during the k ^ week when the effects of sex, ration and time are held constant. = The partial regression coefficient of Y. ., . on B. ., ,. i j k l  i j k l  19  Bi.j kl  th = The i n i t i a l body weight associated with the 1 animal of the i*"* sex on the j "* ration during the k*"* month. 1  1  1  1  f  = The partial regression coefficient of ^^jj.-^  F,.., ijkl  = The feed intake associated with the l*"* animal of the i * " *  o  n  1  1  sex on the j*"* ration during the k ^ month. 1  e.., ijkl  = The random effect associated with the l ' * animal of the 1  i*"* sex on the j " ration during the 1  1  week, which i s  assumed to be independent and normally distributed with mean equal zero and variance a^. A l l effects i n the model except  were regarded as fixed.  The level of significance was 0.05. A l l significant effects were tested by Duncan's new multiple range test, as modified by Kramer (30).  F. 1.  Calculations  Apparent Digestibility The apparent digestion of energy, dry matter, organic matter and  protein was calculated as the difference between nutrient intake and feces excretion, expressed as a per cent of nutrient intake.  Since no  corrections were made for fecal components of endogenous origin, i t was assumed that the feces represented residues of dietary origin only, and thus the term apparent digestibility would describe a l l such coefficients calculated i n this experiment. late digestibility:  The following formula was used to calcu-  20 % Digestibility  _ (F x A ) - (F x o  o  F  where,  F A  o o  x  o  A l  )  x 100  xA o  grams of feed consumed. per cent "nutrient" content of feed: energy, dry matter, organic matter or protein.  F  1  grams of feces excreted. per cent "nutrient" content of feces: energy, dry matter, organic matter or protein.  2. Biological Value Biological value (BV) i s a measure of dietary nitrogen retained for growth or maintenance and i s expressed as nitrogen retained divided by nitrogen absorbed. experiment.  Such data can be obtained from a nitrogen balance  The calculation i s as follows:  N Intake - (Fecal N + Urinary N) x 100 = Biological Value N Intake - Fecal N and i s called the Thomas equation for apparent biological value (43). The Thomas equation was later modified by Mitchell (36) to correct for metabolic fecal losses and endogenous urinary losses. Since both of these fractions are d i f f i c u l t to measure this latter method was not used. 3. Net Protein Utilization Since the overall usefulness of a given source of protein depends on i t s digestibility as well as on the biological value of the  21 absorbed fraction, net protein utilization i s expressed as follows (34): Net Protein Utilization = Biological Value x Protein Digestibility Net protein utilization (NPU) represents the proportion of food nitrogen retained, whereas biological value represents the proportion of absorbed nitrogen retained (43).  Since apparent digestibility and apparent  biological value were used only apparent net protein utilization values are reported.  G. 1.  Results and Discussion  Formulation and Chemical Composition of Rations The ingredients of the test rations are given i n Table 2.  The  average chemical compositions of the test rations are presented i n Table 3.  Both rations are essentially isocaloric with gross energy  values of about 4.45 kcal/g. The crude protein content of ration 1 and ration 2 was 16.25 and 19.56%, respectively.  The ash content of  ration 1 was higher (9.4%) than that of ration 2 (8.9%). A l l analyses were performed on oven-dried material.  Both rations  contained 89.9% dry matter. 2.  Body Weight Gains Body weight gains were analyzed and the least squares means for  the main effects presented in Table 4.  A record of i n i t i a l and final  body weights and body weight gains i s shown in Appendix Table I.  22 Table 2 Formulation of Experimental Rations Ingredients  Ration 2 Ration 1 (16.25% crude protein) (19.56% crude protein) %  %  Ground wheat  15.0  13.5  Ground corn  5.0  4.5  Ground barley  5.0  4.5  Soybean meal (48.5% crude protein)  13.5  22.1  Sun-cured a l f a l f a  30.0  27.0  5.0  4.5  10.0  9.0  Defluorinated phosphate  2.5  2.25  Dried whey  0.8  0.75  Iodized salt  0.5  0.45  10.0  9.0  Durabond"'"  2.5  2.25  Vitamin-mineral-antibiotic premix^  0.25  0.25  Ground beet pulp D i s t i l l e r ' s solubles  Molasses  Durabond i s a commercial lignin sulphate product which has the ability to "harden" the pellets. It i s manufactured by Georgia-Pacific Co. Ltd., Bellingham, Washington. 'Contributed the following amounts of vitamins, minerals and antibiotics per kg. of complete diet: vitamin A, 4410 I.U.; vitamin D3, 1100 I.U.; vitamin E, 5.5 I.U.; riboflavin 4.4 mg.; calcium pantothenate 8.8 mg.; niacin, 19.8 mg.; vitamin B12, 6.6 meg.; choline chloride, 250 mg.; D-L methionine, 610 mg.; vitamin K, 1 mg.; oleandomycin, 2 mg.; zinc oxide, 66 mg.; potassium iodide, 0.5 mg.; manganese oxide, 88 mg.  23  Table 3 Chemical Composition of Experimental Rations Ration 1  Gross Energy (kcal/g) % Crude Protein % Ash  Ration 2  (16.25% crude protein)  (19.56% crude protein)  Mean ± S.D.  Mean ± S.D.  4.45 ± .05  4.44 ± .03  16.25 ± .07  19.56 ± .08  9.40 ± .02  8.90 ± .06  A l l values are means of triplicate determinations.  24  Table 4 Least Squares Means of Weekly Body Weight Gains Adjusted for I n i t i a l Body Weight and Type of Nutrient Intake Comparison Groups  Type of Nutrient Intake Energy  Dry Matter  (g)  (g)  Female  13.l  a  13.0  a  Organic Matter (g)  Protein  12. 7  13. l  a  (g) a  Male  1.5  - 0.6  - 0.2  0.9  Ration 1 (16.25% crude protein)  8.6  8.5  8.4  10.6  Ration 2 (19.56% crude protein)  6.0  4.1  Week 1  6.3  Week 2  2.3  Week 3  13.3  b  a  a  a  Mean I n i t i a l Body Weight (g)  456  Mean Nutrient Intake (g/week)  645  1  a  a  b  a  b  a  b  a  4.1  a  5.3  4.2  a  2.7  a  3.5  2.4  2.9  a  2.0  a  12.5  a  13.1  456  456  144.5  125.5  3  a  a  13. l  a  a  456  25.84  Within comparison groups, values not having a common superscript are significantly different (P<0.05). Given i n kcal/week.  a  25 Individual nutrient intakes of energy, dry matter, organic matter and protein are given in Appendix Table II. Sex was a significant source of variation on body weight gains. Females had better gains and better feed utilization than males. Whether this finding can be attributed to greater rate of gains i n females or earlier mature weights in males i s not known. Rations and time were not significant effects; also, none of the interactions was significant.  The effects of the two covariables, i n i t i a l body weight  and feed intake, were a significant source of variation. 3.  Digestibility Coefficients Table 5 summarizes the results of the least squares analyses on  the  apparent digestibilities of energy, dry matter, organic matter and  protein.  A complete record of the derivation of the four categories  of digestibility coefficients i s presented in Appendix Tables III, IV, V and VI, respectively. The females had significantly greater apparent digestibilities of energy, dry matter and organic matter than the males.  Although there  was no significant effect of sex on apparent protein digestibility, females tended to have higher values than males.  The greater apparent  digestibility of energy by the females may have contributed to greater gains in the feeding t r i a l . Rations were a significant source of variation.  Ration 2 (19.56%  crude protein) was more digestible than ration 1 (16.25% crude protein) for a l l four digestibility coefficients.  However, there was no s i g n i f i -  cant effect of ration on body weight gains. It could be that the greater  26  Table 5 Least Squares Means of Digestibility Coefficients Adjusted for Nutrient Intake and I n i t i a l Body Weight Digestibility Coefficients Comparison Groups  Apparent Digestible Energy (%)  Apparent Digestible Dry Matter (%)  Apparent Digestible Organic Matter (%)  Apparent Digestible Protein (%)  Female  67.80  3  69.01  3  70.79  3  69.16  Male  64.46  b  65.95  b  67.15  b  66.90  3  3  Ration 1 (16/25% crude protein)  65.09  3  66.44  a  67.73  a  62.83  Ration 2 (19.56% crude protein)  67.32  b  68.52  b  70.21  b  73.23  Week 1  68.71°  67.18  69.95  69.80  Week 2  65.43°  70.18  71.24  72.14  Week 3  64.26  65.08  65.72  62.16  C  C  C  d  C  C  d  a  b  C  C  Within the sex and ration comparison groups, values not having a common superscript are significantly different (P<0.05). ^Within the period comparison group, values not having a common superscript are significantly different (P<0.05) from each other by Duncan's new multiple range test as modified by Kramer (30).  d  27 digestibility of ration 2 was not large enough to result in significantly greater body weight gains. Time was also a significant source of variation for a l l digestib i l i t y coefficients except apparent digestible energy.  During the third  week of the experiment the apparent digestibility of dry matter, organic matter and protein was significantly lower than for the f i r s t and second weeks.  A similar trend was observed for the apparent d i g e s t i b i l i t y of  energy.  However, the drop in digestibility during the third week had  no significant effect on body weight gains. None of the interactions had a significant effect on digestibility. The two covariables, i n i t i a l body weight and feed intake, had no significant effect on the digestibility coefficients studied. A comparison between the apparent d i g e s t i b i l i t y of energy and dry matter indicated that, as i s the case with cattle and sheep (19), these values are very close.  Therefore, a reliable estimate of  apparent digestible energy can be obtained from apparent digestible dry matter. 4.  Bomb calorimetry of feces should thus seldom be necessary.  Biological Value and Net Protein Utilization A summary of the least squares means of the nutritional indices  derived from the nitrogen balance i s shown in Table 6. Least squares means for the main effects are listed for biological value and net protein u t i l i z a t i o n . A complete record of input and output parameters of the nitrogen balance i s given i n Appendix Table VII.  28  Table 6 Least Squares Means of Protein Utilization Indices Adjusted for Protein Intake and I n i t i a l Body Weight Protein Utilization Indices Comparison Groups  Biological Value (%)  Net Protein Utilization (%)  Female  68.40  3  46.90  Male  64.94  a  43.28  Ration 1 (16.25% crude protein)  66.38  42.02  Ration 2 (19.56% crude protein)  66.96  48.17  Week 1  67.24  46.08  Week 2  67.38  48.53  Week 3  65.39  40.67  a  a  C  c  d  a  a  a  b  C  C  d  Within the sex and ration comparison groups, values not having a common superscript are significantly different (P<0.05). ^Within the periods comparison group, values not having a common superscript are significantly different (P<0.05) from each other by Duncan's new multiple range test as modified by Kramer (30).  29 Sex was not a significant source of variation for any of the two protein utilization indices studied.  Consequently better protein  utilization by females did not account for their greater body weight gains.  However, better feed utilization, as indicated by greater  apparent digestibility of energy, dry matter and organic matter, contributed towards the larger gains by females. Ration 2 (19.56% crude protein) showed a significantly greater net protein utilization than ration 1 (16.25% crude protein).  Differ-  ences i n biological value for rations were not significant; however, ration 2 tended to have a greater biological value than ration 1. This would mean that the animals utilized efficiently supplemental protein of high quality. Time was a significant source of variation for both protein utilization indices studied.  During the third week of the experiment  there was a decrease i n the utilization of the protein.  The lower  values for the digestibility coefficients and protein u t i l i z a t i o n indices were, however, not large enough to result i n any significant decrease in body weight gains. It i s possible that during repelleting, the experimental rations became deficient in one or more essential nutrients and that this deficiency only became manifest during the third week of the experiment.  Another possible explanation i s the  absence of unpelleted hay or a l f a l f a from the ration.  However, no  signs of digestive upsets were observed throughout the experiment.  The  effect of a source of roughage on the physiology of the digestive system remains to be investigated.  30 None of the interactions had a significant effect on protein utilization. The two covariables, i n i t i a l body weight and protein intake, had no significant effect on the protein utilization indices studied. Although i t has been suggested that the large intestine i s the main site of digestion and absorption in the horse (29), rabbit (26) and, possibly, chinchilla (52), information concerning the relative importance of different segments of the digestive tract in protein nutrition i s not available.  Recent studies by Reitnour et a l . (44)  and Hintz et_ a l . (24) indicated that in the equine the major site of protein digestion i s prececal although there is a significant disappearance of nitrogen from the lower gut.  According to Hintz jet a l . (23)  the site of digestion of a component of the feed was not influenced by the diet.  For instance, they found that the major site of fibre  digestion was the cecum and colon whereas the major site of available carbohydrate and protein digestion was prececal regardless of the hay : grain ratio.  These results suggest a major role of prececal protein  digestion and absorption in the equine, and i t appears that protein digestion and absorption in this species more closely resemble those functions reported for the chick (46) and the pig (47) than for cattle (41). The results of the protein utilization study suggest that the animals on the higher protein ration utilized the protein more efficiently than the animals on the lower protein ration. This could be attributed to a greater utilization of the higher quality protein supplement over  31 the lower quality protein of the basal ration.  The sensitivity of  the growing chinchilla to protein quality suggests a major role for prececal protein digestion and absorption although this does not necessarily preclude the synthesis of microbial protein in the lower gut.  Identification of digestive products and quantification of their  absorption i s needed before the contribution of different parts of the alimentary canal to the protein nutrition of the chinchilla can be fully evaluated.  32  IV.  CONCLUSIONS  Female chinchilla utilized feeds more efficiently than male chinchilla during the late phase of growth as indicated by greater body weight gains for females after adjustment for i n i t i a l body weight and feed intake.  These gains were not the result of better protein  u t i l i z a t i o n but of a better energy utilization. The growing chinchilla utilized the protein in the 19.56% crude protein ration approximately 9% more efficiently than in the 16.25% crude protein ration.  The efficient utilization of high  quality protein suggests a considerable amount of prececal digestion and absorption. Apparent digestible dry matter i s a reliable estimate of apparent digestible energy. 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The influence of nonprotein nitrogen and protein quality on the nitrogen rentention of adult mares. J_. Ariim. Sci. 30: 753-760.  52.  Smith, D.C. (1970). Carbohydrate digestion i n the chinchilla. M. Sc. Thesis, The University of British Columbia.  53.  Stucki, W. P. and A. E. Harper (1962). Effects of altering the ratio of indispensible to dispensible amino acids i n diets for rats. J. Nutr. 78: 278-286.  54.  Thompson, H. W., and A. N. Worden (1956). The Rabbit. Wellmer Bros, and Co. Ltd., London and Glasgow, pp. 26-31.  55.  Thompson, W. S. T. and H. N. Munro (1955). The relationship of carbohydrate metabolism to protein metabolism. IV. The effect of substituting fat for dietary carbohydrate. J. Nutr. 56: 139-150.  56.  Whipple, C. H. (1948). Hemoglobin, plasma protein and c e l l protein. Charles C. Thomas, Springfield, 111.  57.  White, M. C. (1964). Chinchilla Research. A bibliography. NCBA Research Bulletin No. 41, Middletown, New York.  58.  Young, C. M., E. L. Empey, V. U. Serraon, and Z. H. Pierce (1957). Weight reduction i n obese young men. Metabolic studies. J. Nutr. 61: 437.  VI. APPENDIX  TABLE I I n i t i a l and Final Body Weights TREATMENTS Sex  Animal No.  Ration  16.25% crude protein Female  19.56% crude protein  16.25% crude protein Male  19.56% crude protein  I n i t i a l Final Weight Weight (g) (g)  Week 3  Week 2  Week 1 Weight Gain (g)  I n i t i a l Final Weight Weight (g) (g)  Weight Gain (g)  I n i t i a l Final Weight Weight (g) (g)  Weight Gain (g)  1  464  452  -12  452  470  18  470  482  12  2  454  460  6  460  467  7  467  464  - 3  3  443  476  33  476  470  - 6  470  484  14  4  468  495  27  495  497  2  497  504  7  5  549  556  7  556  542  -14  542  545  3  6  468  464  - 4  464  459  - 5  459  470  11  7  466  460  - 6  460  465  5  465  475  10  8  467  461  - 6  461  465  4  465  486  21  9  406  430  24  430  455  25  455  461  6  10  403  417  14  417  421  4  421  430  9  11  414  395  -19  395  424  29  424  410  -14  12  413  411  - 2  411  411  0  411  428  17 o  TABLE II Nutrient Intakes TREATMENTS Sex  Animal No.  Ration  1 16.25% crude protein Female 19.56% crude protein  16.25% crude protein Male 19.56% crude protein  Week 1  Week 2  Week 3  Energy Dry Organic Protein Energy Dry Organic Protein Organic Protein Energy Dry Intake Matter Matter Intake Intake Matter Matter Intake Intake Matter Matter Intake Intake Intake Intake Intake Intake Intake (kcal) (kcal) (g) (kcal) (g) (g) (g) (g) (g) (g) (g) (g) 332 17.4 581 75 68 12.2 475 107 97 131 119 21.3  2  584  132  120  21.5  710  160  145  26.0  484  109  99  17.7  3  775  175  159  28.4  879  198  179  32.0  519  117  106  19.0  4  667  151  138  29.5  730  164  149  32.1  494  111  101  21.7  5  871  196  179  38.3  538  121  110  23.7  445  100  91  19.6  6  553  125  114  24.5  556  125  114  24.5  356  80  73  15.6  7  523  118  107  19.2  520  116  105  18.9  298  67  61  10.9  8  669  151  137  24.5  821  185  168  30.1  618  139  126  22.6  9  758  171  155  27.8  955  215  195  34.9  670  151  137  24.5  10  827  187  170  36.6  707  159  145  31.1  450  101  92  19.8  11  508  115  105  22.5  725  163  148  31.9  570  128  117  25.0  12  636  144  131  28.2  734  165  150  32.3  538  121  110  23.7 4>  Table III Apparent Digestible Energy Data TREATMENTS Sex  Animal Total ene cgy No. consumed(ccal)  Ration 16.25% crude protein  Female 19.56% crude protein  16.25% crude protein Male 19.56% crude protein  Total feces excreted (gm)  Caloric density feces (kcal/gm)  Total fecal energy (kcal)  3  Percent digestible energy  Wk.l Wk.2 Wk.3 Wk.l  Wk.2  Wk.3  Wk.l  Wk.2  Wk.3  Wk.l Wk.2 Wk.3 Wk.l  Wk.2  Wk.3  1  332  475  581  27.4  37.4  54.2  4.32  4.33  4.26  118  185  231  64.5  62.1  60.3  2  584  710  484  47.7  46.9  44.3  4.23  4.26  4.16  202  227  184  65.5  68.0  62.0  3  775  879  519  55.3  51.9  38.9  4.14  4.36  4.08  229  259  159  70.5  70.5  69.6  4  667  730  494  46.6  46.9  43.7  4.37  4.49  4.20  204  241  184  69.4  67.0  62.8  5  871  538  445  54.7  41.3  34.5  4.23  4.18  4.10  232  197  142  73.3  63.4  68.1  6  553  556  356  36.7  36.4  26.0  4.20  4.21  4.07  154  175  106  72.2  68.5  70.3  7  523  520  298  36.4  37.4  35.2  4.12  4.29  4.04  150  183  142  71.3  65.0  53.4  8  669  821  618  54.0  61.2  55.8  4.14  4.20  4.14  224  294  231  66.5  64.2  62.6  9  758  955  670  56.6  63.8  64.3  4.32  4.30  4.22  245  313  271  67.7  67.3  60.0  10  827  707  450  57.7  51.2  43.4  4.21 4.34  4.30  243  254  187  70.6  64.1  58.5  11  508  725  570  40.4  52.5  45.6  4.13 4.19  4.15  167  251  189  67.1  65.4  66.9  12  636  734  538  50.4  48.5  43.9  4.32  4.33  218  236  190  65.7  68.9  64.7  A l l yalues are means of duplicate determinations.  4.25  Table IV Apparent Dry Matter Digestibility Data TREATMENTS Sex  Animal No.  Feed Intake (g)  D.M. Intake (g)  D.M. Fecal Output (g)  Percent Dry Matter Digestibi!Lity  Week 1 Week 2 Week 3 Week 1 Week 2 Week 3 Week 1 Week 2 Week 3 Week 1 Week 2 Week 3  Ration 1  84  120  147  75  107  131  27.4  37.4  54.2  63.5  67.5  61.3  2  148  180  123  132  160  109  47.7  46.7  44.3  63.9  72.4  62.5  3  197  222  131  175  198  117  55.3  51.9  38.9  68.4  74.8  68.9  4  170  184  125  151  164  111  46.6  46.9  43.7  69.1  72.9  63.6  5  221  136  112  196  121  100  54.7  41.3  34.5  72.2  68.2  68.4  6  140  140  90  125  125  80  36.7  36.5  26.0  70.6  72.8  70.8  7  133  130  75  118  116  67  36.4  37.4  35.2  69.2  70.1  60.5  8  170  208  156  151  185  139  54.1  61.2  55.8  64.3  68.5  62.3  9  193  242  170  171  215  151  56.6  63.8  64.3  67.1  71.5  60.0  10  210  179  114  187  154  101  57.7  51.2  43.4  69.2  69.5  60.5  11  129  183  144  115  163  128  40.4  52.5  45.6  64.9  69.5  66.8  12  162  185  136  144  165  121  50.4  48.5  43.9  65.0  72.1  66.3  16.25%  crude protein u' _m *_ 1 a r cmcixc  19.56%  crude protein  ,  16.25%  crude protein Mai a  naj-e 19.56%  crude protein  Table V Apparent Organic Matter Digestibility Data TREATMENTS Sex  Animal No.  O.M. intake (g)  Wk.l Wk.2 Wk.3 Wk.l  Ration  Percent fecal ash  Fecal D.M. (g)  a  Fecal O.M. (g)  Percent O.M. digestibility  Wk.2  Wk.3  Wk.l  Wk.2  Wk.3  Wk.l Wk.2 Wk.3 Wk.l  Wk.2  Wk.3  1  68  47  119  27.4  37.4  54.2  15.5  17.9  16.2  23.2  30.7  45.4  65.9  68.4  61.9  2  120  145  99  47.7  46.7  44.3  17.0  17.9  17.8  39.6  38.3  36.4  67.0  73.6  63.3  3  159  179  106  55.3  51.9  38.9  18.0  19.5  19.2  45.3  41.8  31.4  71.5  76.6  70.4  4  138  149  101  46.6  46.9  43.7  18.0  17.6  17.7  38.2  38.6  36.0  72.3  74.1  64.4  5  179  110  91  54.7  41.3  34.5  19.0  18.9  18.8  44.3  33.5  28.0  75.3  69.6  69.2  6  114  114  73  36.7  36.5  26.0  19.5  19.2  19.5  29.5  29.5  20.9  74.1  74.1  71.4  7  107  105  61  36.4  37.4  35.2  19.5  18.2  19.1  29.3  30.6  28.5  72.6  70.9  53.3  8  137  168  126  54.1  61.2  55.8  18.5  17.9  16.5  44.1  50.2  46.6  67.8  70.1  63.0  9  155  195  137  56.6  63.8  64.3  17.0  17.4  16.9  47.0  52.7  53.4  69.7  73.0  61.0  10  170  145  92  57.7  51.2  43.4  17.0  17.4  16.7  47.9  42.3  36.2  71.8  70.9  60.7  11  105  148  117  40.4  52.5  45.6  17.5  17.7  17.8  33.3  43.2  37.5  68.3  70.8  67.9  12  131  150  110  50.4  48.5  43.9  17.0  17.8  16.6  41.8  39.9  36.6  68.1  73.4  66.7  16.25%  crude protein L i s*\ m A 1  1 y—  remaxe 19.56%  crude protein  16.25%  crude protein M ^ l _»  _iaxe 19.56%  crude protein  A l l values are means of duplicate determinations.  Table VI Apparent Digestible Protein Data TREATMENTS Sex  Animal Total protein intake (g) No.  Female 19.56% crude protein  16.25% crude protein Mo "1  riaxe 19.56% crude protein  Percent fecal protein  Wk.l Wk.2 Wk.3 Wk.l  Wk.2  Wk.3  Wk.l  Wk.2  Wk.3  1  12.2 17.4 21.3 27.4  37.4  54.2  17.6  15.7  20.7  2  21.5 26.0 17.7 47.7  46.7  44.3  14.6  17.2  3  28.4 32.2 19.0 55.3  51.9  38.9  17.6  4  29.5 32.1 21.7 46.6  46.9  43.7  5  38.3 23.7 19.6 54.7  41.3  6  24.5 24.5 15.6 36.7  7  Total fecal protein (g)  Percent digestible protein  Wk.l Wk.2 Wk.3 Wk.l  Wk.2  Wk.3  4.8  5.9 11.2 60.7  66.1  48.5  16.4  7.0  8.0  7.3 67.4  69.3  58.8  13.9  15.5  9.7  7.2  6.0 65.9  77.6  68.4  13.3  15.7  15.0  6.2  7.4  6.6 79.0  77.0  69.6  34.5  18.8  17.6  17.0  10.3  7.3  5.9 73.1  69.2  69.9  36.4  26.0  17.0  17.0  15.2  6.2  6.2  4.0 74.7  74.7  74.3  19.2 18.9 10.9 36.4  37.4  35.2  13.0  12.8  11.1  4.7  4.8  3.9 75.5  74.6  64.3  8  24.5 30.1 22.6 54.0  61.2  55.8  17.6  19.1  19.4  9.5 11.7 10.8 61.3  61.1  52.2  9  27.8 34.9 24.5 56.6  63.8  64.3  18.0  18.7  20.3  10.2 11.9 13.0 63.3  66.0  47.0  10  36.6 31.1 19.8 57.7  51.2  43.4  17.8  16.7  14.3  10.3  8.6  6.2 71.9  72.3  68.7  11  22.5 31.9 25.0 40.4  52.5  45.6  13.0  14.3  18.0  5.2  7.5  6.8 76.9  76.5  72.8  12  28.2 32.3 23.7 50.4  48.5  43.9  18.0  19.4  20.3  9.0  9.4  8.9 68.1  70.9  62.5  Ration 16.25% crude protein  Total D.M. Fecal output (g)  A l l values are means of duplicate determinations.  Table VII Protein Utilization Indices TREATMENTS  Sex  Female 19.56% crude protein  16.25% crude protein 1  *a  riaxe  19.56% crude protein  N Intake (mg)  Fecal N (mg)  Urinary N (mg) Apparent Biological Value %  Apparent Net Protein utilization %  Wk.3  Wk.l  Wk.2  Wk.3 Wk.l Wk.2 Wk.3 Wk.l Wk.2 Wk.3  938 1,794  356  535  569 69.8 71.0 64.7 42.1 47.0 30.6  2  3,432 4,160 2,834 1,116 1,284 1,161  658  938  534 71.3 67.4 68.1 48.3 46.6 40.2  3  4,550 5,148 3,042 1,559 1,152  965 1,035 1,227  790 65.4 69.3 62.0 43.0 53.8 42.3  4  4,723 5,133 3,474  993 1,177 1,049 1,078 1,088  732 71.1 72.5 69.8 56.2 55.9 48.7  5  6,135 3,787 3,130 1,685 1,165  938 1,571  975  728 64.7 62.8 66.8 46.9 43.5 46.7  6  3,913 3,913 2,504  998  993  632  936  899  747 67.9 69.2 60.1 50.6 51.6 44.9  7  3,068 3,016 1,742  757  767  627  825  762  391 64.3 66.1 65.0 48.4 49.3 41.6  8  3,926 4,810 3,614 1,526 1,873 1,769  896 1,075  756 62.7 63.4 59.0 38.3 38.7 30.1  9  4,446 5,590 3,926 1,630 1,908 2,089  811 1,256  625 71.2 65.9 66.0 45.1 43.4 30.9  994 1,317 1,075  737 68.7 70.2 66.0 49.7 50.9 45.2  Wk.3  Wk.l  1  1,950 2,782 3,406  773  Ration 16.25% crude protein  Mo  Animal No.  Wk.l  Wk.2  Wk.2  10  5,853 4,976 3,161 1,644 1,367  11  3,600 5,101 4,006  12  4,507 5,164 3,787 1,451 1,537 1,427  840 1,202 1,094 1,041 1,525 1,025 62.3 60.9 64.8 47.8 46.5 47.1 914 1,005  767 70.1 72.3 67.5 47.5 50.8 42.1  

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