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A model to predict pig growth based on Western Canadian production conditions Dyble, David Leslie 1990

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THE UNIVERSITY OF BRITISH COLUMBIA FACULTY OF GRADUATE STUDIES The undersigned c e r t i f y t h a t they have read, and recommended to the F a c u l t y of Graduate S t u d i e s f o r acceptance, a MSc. t h e s i s e n t i t l e d : A MODEL TO PREDICT PIG GROWTH BASED ON WESTERN CANADIAN PRODUCTION CONDITIONS Submitted by: DAVID L. DYBLE i n p a r t i a l f u l f i l m e n t of the requirements f o r the MSc. Degree A d v i s o r Date of O r a l Examination: The Student has s a t i s f a c t o r i l y completed and passed the MSc O r a l Examination. A d v i s o r A MODEL TO PREDICT PIG GROWTH BASED ON WESTERN CANADIAN PRODUCTION CONDITIONS By David L e s l i e Dyble B.SC., The U n i v e r s i t y of B r i t i s h Columbia, 1983 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES Department of Animal Science The U n i v e r s i t y of B r i t i s h Columbia Vancouver, B.C. THE UNIVERSITY OF BRITISH COLUMBIA December, 1990 (c) David L e s l i e Dyble, 1990 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 that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of QsnxsTKeS Science-The University of British Columbia Vancouver, Canada Date DE-6 (2/88) ABSTRACT An i n t e g r a t e d p i g growth model s p e c i f i c to the d i e t a r y f o r m u l a t i o n s , g e n e t i c q u a l i t y and environmental c o n d i t i o n s of western Canada has been developed. A computer program was designed to simulate growth of p i g s between 20 kgs and 100 kgs l i v e weight. A spreadsheet format -Lotus 123 - was used to allow programming steps to be understood by a l l us e r s , i n c l u d i n g those who do not possess a high degree of programming s k i l l . A l i n e a r programming system was a l s o i n c o r p o r a t e d through the use of an a l g o r i t h m - Optimal S o l u t i o n s . A u s e f u l method of a v o i d i n g c i r c u l a r e r r o r s , through an i n i t i a l p r e d i c t i o n of growth, was developed through the use of a 'Gompertz' s t y l e equation which d e s c r i b e s growth; B.W. = A exp (-B exp ( - k ( t ) ) ) where B.W. i s body weight (kg), A i s mature body weight [estimate based on NRC(1988):164 kg], B i s a r a t e constant [4.46], k i s a r a t e constant [range from 0.01 to 0.015] and t i s the time i n days. A model of n u t r i e n t flow was developed with components which i n c l u d e , [1] body composition at the s t a r t of growth, [2] energy and amino a c i d i n t a k e , [3] the u t i l i z a t i o n of i n g e s t e d amino a c i d s , [4] the upper l i m i t to d a i l y p r o t e i n r e t e n t i o n , [5] The i n t e r a c t i o n between m e t a b o l i z a b l e energy and p r o t e i n as a p r o p o r t i o n of the d e p o s i t i o n of body l i p i d and p r o t e i n , and [6] equations which a s s i s t i n the p r e d i c t i o n of performance f a c t o r s . A model proof was undertaken through a study of p i g performance across 4 d i e t s v a r y i n g i n p r o t e i n l e v e l . P i g performance i n d i c a t o r s i n c l u d e d ; feed i n t a k e , feed e f f i c i e n c y , c a r c a s s index and c a r c a s s y i e l d . A s i g n i f i c a n t c o r r e l a t i o n (p<0.05) was shown between model p r e d i c t i o n s of market age and t r i a l r e s u l t s . P i g r e a r i n g c o n d i t i o n s d i f f e r i n western Canada, compared to the r e s t of North America, due to the i n f l u e n c e of B r i t i s h breeding companies and the common use of b a r l e y as a key i n g r e d i e n t of swine d i e t s . The growth model developed was found to be a good p r e d i c t o r of performance of p i g s being grown i n western Canada. Feed intake and the g e n e t i c p o t e n t i a l f o r p r o t e i n d e p o s i t i o n were found to be the most important p r e d i c t o r s of p i g performance. i i i ACKNOWLEDGEMENTS I would l i k e to thank my a d v i s o r , Dr. R.M. Beames f o r h i s support, guidance and e s p e c i a l l y h i s p a t i e n c e i n enduring my enthusiasm f o r the p i g m o d e l l i n g concepts. Committee members, e s p e c i a l l y Drs. Kozak and Steve Mason, made unique c o n t r i b u t i o n s which are g r a t e f u l l y accepted. Support from East C h i l l i w a c k Co-op was important f i n a n c i a l l y through t i m e - s h a r i n g between work and s c h o o l . Mary-lou S w i f t ' s a s s i s t a n c e s t a r t e d with her MSc. work i n b r o i l e r growth mod e l l i n g and continued through m o t i v a t i o n a l and s c h o l a s t i c a s s i s t a n c e with the c u r r e n t p r o j e c t . The most important c o n t r i b u t e r s to t h i s t h e s i s were my wife, Margot and my c h i l d r e n , Adam and Shannon, who u n c o n d i t i o n a l l y endured many hours of i s o l a t i o n when my p a r t i c i p a t i o n was w i t h h e l d as I t o i l e d on t h i s p r o j e c t . i v TABLE OF CONTENTS A b s t r a c t i i i Acknowlegements i v L i s t of t a b l e s v i i L i s t of f i g u r e s i x Equation format x i (I) I n t r o d u c t i o n 1 (II) S t r a t e g y 3 ( I I I ) L i t e r a t u r e Review 4 1) E m p i r i c a l models 4 2) Requirement models 4 3) I n t e g r a t e d models 5 4) Feed in t a k e of swine 7 5) Important mod e l l i n g concepts 11 a) U t i l i z a t i o n of i n g e s t e d amino a c i d s 11 b) Upper l i m i t to d a i l y p r o t e i n r e t e n t i o n 15 c) Energy m o d e l l i n g concepts 23 (IV) P i g Model Development 30 1) Feed i n t a k e s e c t i o n 33 2) I n i t i a l body composition s e c t i o n 42 3) P r o t e i n s e c t i o n 50 4) Energy s e c t i o n 56 (V) M o d e l l i n g the P i g 69 (VI) Model D i s c u s s i o n 72 (VII) Model V e r i f i c a t i o n Study 83 1) M a t e r i a l s and methods 83 2) Data a n a l y s i s 87 v 3) R e s u l t s 89 a) Feed i n t a k e a n a l y s i s 96 b) E f f e c t of d i e t on f e e d e f f i c i e n c y 100 c) E f f e c t of d i e t on days t o market 101 d) E f f e c t of d i e t on c a r c a s s i n d e x 102 e) E f f e c t of d i e t on c a r c a s s y i e l d 103 f ) E f f e c t of d i e t on average d a i l y g a i n 104 ( V I I I ) Model V e r i f i c a t i o n D i s c u s s i o n 106 (IX) C o n c l u s i o n 114 (**) F o o t n o t e s 118 (X) R e f e r e n c e s 119 Appendix 1 - Key t o terms used i n the t h e s i s 126 Appendix 2 - Example of model i n p u t / o u t p u t 129 v i LIST OF TABLES Table 1. Amino a c i d p a t t e r n s of i d e a l p r o t e i n r e l a t i v e to tryptophan. Table 2. Amino a c i d p a t t e r n of i d e a l p r o t e i n f o r growing p i g s (g/kg i d e a l p r o t e i n ) . Table 3. Values f o r the maximum r a t e of p r o t e i n d e p o s i t i o n (Pr") i n White Breeds and s t r a i n s of p i g s used f o r the p r o d u c t i o n of meat i n kgs/day. Table 4. Values f o r the parameters t h a t d e f i n e the rate of growth and composition of the body f o r d i f f e r e n t genotypes. Table 5. A comparison of the c a l c u l a t i o n s of Van Es (1980) and Armstrong (1969) f o r the energy c o s t of p r o t e i n d e p o s i t i o n . Table 6. Values f o r the minimum r a t i o of f a t gain to p r o t e i n gain (Lr to Pr) i n White Breeds and s t r a i n s of p i g s used f o r the p r o d u c t i o n of meat. Table 7. Values f o r Ve and VI f o r use i n c a l c u l a t i n g the e f f e c t i v e environmental temperatures (temp) i n the equation temp = temp * Ve * VI. Table 8. D i e t composition and estimated n u t r i e n t a n a l y s i s ( a i r - d r y b a s i s ) . Table 9. Estimated i n g r e d i e n t composition. Table 10. Crude p r o t e i n (N * 6.25) of t r i a l d i e t s by a n a l y s i s (g/100 g as fed) [10 composite samples f o r each d i e t c r e a t e d from 165 samples c o l l e c t e d ] . v i i Table 11. E f f e c t s of d i e t and sex on performance c h a r a c t e r i s t i c s of swine with ANOVA summary. 90 Table 12. P i g performance on t r i a l d i e t s (males). 93 Table 13. P i g performance on t r i a l d i e t s (females). 94 Table 14. L i v e weight (kg) and c a r c a s s weight (kg) at market f o r t r i a l d i e t s . 95 Table 15. D a i l y feed i n t a k e by week, a c t u a l vs. model. 96 Table 16. Feed c o n v e r s i o n on t r i a l d i e t s . 100 Table 17. E f f e c t of d i e t p r o t e i n on days to market. 101 Table 18. E f f e c t of d i e t on c a r c a s s index (males). 103 Table 19. E f f e c t of d i e t on c a r c a s s y i e l d c l a s s (males). 104 Table 20. E f f e c t of d i e t on average d a i l y g a i n (males). 105 Table 21. Comparison of model p r e d i c t i o n and the a c t u a l performance f o r days to market and feed useage (kg). Data r e p r e s e n t combined data f o r males and females. 110 v i i i LIST OF FIGURES Page F i g u r e 1. P o t e n t i a l p r o t e i n d e p o s i t i o n as a f u n c t i o n of body weight. Case 1 sugests a maximum at 40 to 50% of mature weight (Black et a l . , 1986). Case 2 suggests a p l e a t e a u a t t a i n a b l e e a r l y i n l i f e (Whittemore et a l . , 1976) 22 F i g u r e 2. A comparison between a 'Gompertz f u n c t i o n ' and a growth curve c o l l e c t e d over a wide range of genotypes and environmental c o n d i t i o n s . 35 F i g u r e 3. Graph of a 'Gompertz f u n c t i o n ' designed to r e p r e s e n t growth curves from b i r t h to 100 kgs f o r market ages ranging from 147 to 220 days to market. 36 F i g u r e 4. Graph of a 'Gompertz f u n c t i o n ' designed to r e p r e s e n t growth curves from b i r t h to a year of age f o r market ages ranging from 147 to 220 days to market. 37 F i g u r e 5. Graph of a 'Gompertz f u n c t i o n ' designed to r e p r e s e n t growth curves from b i r t h to 70 days of age f o r market ages ranging from 147 to 220 days to market. 38 F i g u r e 6. Comparisons between Tess et a l . l o g a r i t h m i c r e p r e s e n t a t i o n of body p r o t e i n (PT), l i p i d (LT), ash (AT) and water (YT) and model p r e d i c t i o n s . ( B e l t s v i l l e high f a t g e n e t i c s t r a i n s ) . 45 F i g u r e 7. Comparisons between Tess et a l . l o g a r i t h m i c r e p r e s e n t a t i o n of body p r o t e i n (PT), l i p i d (LT), ash (AT) and water (YT) and model p r e d i c t i o n s . ( B e l t s v i l l e low f a t g e n e t i c s t r a i n s ) . 46 i x F i g u r e 8. Comparisons between Tess et a l . l o g a r i t h m i c r e p r e s e n t a t i o n of body p r o t e i n (PT), l i p i d (LT), ash (AT) and water (YT) and model p r e d i c t i o n s . (Hampshire * Large White commercial s t r a i n ) . F i g u r e 9. Flow diagram s i m u l a t i n g n u t r i e n t u t i l i z a t i o n by the growing p i g combining concepts of Moughan et a l . (1988) and Whittemore (1987). F i g u r e 10. Graph of a model d e r i v e d comparison of d i e t a r y crude p r o t e i n a v a i l a b l e to be u t i l i s e d , d i g e s t i b l e crude p r o t e i n a v a i l a b l e f o r p r o t e i n a c c r e t i o n and p r o t e i n a c t u a l l y r e t a i n e d due to genotype and phenotype l i m i t a t i o n s . F i g u r e 11. A comparison between model d e r i v e d feed i n t a k e and the feed intake observed on t r i a l . F i g u r e 12. A " t " t e s t comparison between model d e r i v e d feed intake and the feed i n t a k e observed on t r i a l . F i g u r e 13. Growth curves developed by weekly p i g weights on the fo u r t e s t d i e t s . F i g u r e 14. Feed i n t a k e s achieved on the fo u r t e s t d i e t s over 13 weeks on t r i a l . F i g u r e 15. Comparison of feed useage, model p r e d i c t i o n vs. t r i a l (25 -100 kgs). F i g u r e 16. Comparison of age, model p r e d i c t i o n vs. t r i a l (age to 100 kgs). Equation Format Equations i n t h i s t h e s i s are presented assuming an order of precedence as f o l l o w s : Operator Operation Precedence number A e x p o n e n t i a t i o n 1 - or + i d e n t i f y as negative or 2 p o s i t i v e * or / m u l t i p l i c a t i o n or 3 d i v i s i o n + or - a d d i t i o n or s u b t r a c t i o n 4 An o v e r r i d i n g order of precedence occurs by e n c l o s i n g o p e r a t i o n s i n parentheses. The o p e r a t i o n s i n s i d e the parentheses are performed f i r s t . Within each set of parentheses, precedence numbers apply. The precedence system i s i d e n t i c a l to t h a t used by Lotus 123 ( c ) . (c) Copyright 1986,1989 Lotus Development C o r p o r a t i o n 55 Cambridge Parkway Cambridge, MA 02142 The term 'exp' i s used i n the t h e s i s to r e p r e s e n t the number e (e = base of the system of n a t u r a l logarithms having the approximate numerical value of 2.71828) r a i s e d to a s p e c i f i c power. Exp (x) c a l c u l a t e s the value of e (2.71828) r a i s e d to the power x. x i PIG GROWTH MODEL page 1 I. INTRODUCTION T h i s t h e s i s p r o v i d e s a d e s c r i p t i o n of a model s i m u l a t i n g growth i n a p i g between approximately 20 kgs and 100 kgs l i v e weight. The computer model i s designed to produce a c o n t i n u o u s l y updated r e p r e s e n t a t i o n of the p i g s being grown i n western Canada through the s i m u l a t i o n of n u t r i t i o n , environment, g e n e t i c s and other g r o w t h - a l t e r i n g parameters which can be represented mathematically. The growth model has been developed on a popular spreadsheet program c a l l e d 'Lotus 123' 1. Lotus i s a u s e f u l program f o r mode l l i n g because the methodical use of the rows and columns of the spreadsheet allows the values d e r i v e d f o r each equation used i n the model to be observed and t e s t e d f o r i t s a p p l i c a b i l i t y . A b e t t e r computer language f o r model use by a d v i s o r s and educators c o u l d then be chosen, and the Lotus program r e w r i t t e n i n t o the new language with r e l a t i v e ease. A l i n e a r programming system i s a l s o i n c o r p o r a t e d i n t o the m o d e l l i n g package through the use of an a l g o r i t h m -Optimal S o l u t i o n s ^ . The l i n e a r programming system i s necessary, as some of the parameters used to d e s c r i b e f e e d s t u f f s i n the model ( e . g . b i o l o g i c a l value) are not PIG GROWTH MODEL page 2 normally i n c l u d e d i n commercially a v a i l a b l e l i n e a r programming systems. A d e s c r i p t i o n of the equations which e s t a b l i s h the p i g model as unique to western Canada are i n c l u d e d i n the t h e s i s . Feed i n t a k e i s i d e n t i f i e d as a parameter which has a l a r g e e f f e c t on modelled outcome. A t r i a l was e s t a b l i s h e d to compare feed intake estimated by the model with a c t u a l feed i n t a k e s . The t r i a l was a l s o used as a method of t e s t i n g the v a l i d i t y of the model. PIG GROWTH MODEL page 3 I I ) STRATEGY The t h e s i s has been s p l i t i n t o s e c t i o n s deemed a p p r o p r i a t e f o r the development of the p i g model. A l i t e r a t u r e review ( s e c t i o n I I I ) i s i n c l u d e d to develop the concepts needed f o r model c o n s t r u c t i o n . A p i g model development s e c t i o n (IV) i s i n c l u d e d to i l l u s t r a t e the equations chosen f o r the t h e s i s model of pi g s i n western Canada. S e c t i o n V demonstrates the techniques used to model the p i g through the accumulation of p r o t e i n , l i p i d , ash and water. A model d i s c u s s i o n ( s e c t i o n VI) suggests how important model components (as d i s c u s s e d by Moughan et a l . , 1988) are d e a l t with by the t h e s i s model. A model v e r i f i c a t i o n study ( s e c t i o n VII) i s i n c l u d e d to v e r i f y model output, with the r e s u l t s d i s c u s s e d i n s e c t i o n V I I I . A guide to important terms used i n the t h e s i s has been i n c l u d e d i n appendix 1. An example of the t h e s i s model in p u t / o u t p u t screens i s shown i n appendix 2. A review of appendix 1 and 2 (before the t h e s i s i s read) may a s s i s t i n the comprehension of the many concepts developed i n the t h e s i s . PIG GROWTH MODEL page 4 I I I ) LITERATURE REVIEW There are three types of growth models; (1) e m p i r i c a l models, (2) requirement models, and (3) i n t e g r a t e d models. A shor t d e s c r i p t i o n of each model type i s i n c l u d e d below. (1) E m p i r i c a l models E m p i r i c a l or response models are based on the s t a t i s t i c a l a n a l y s i s of experimental r e s u l t s i n c l u d i n g growth, feed i n t a k e and c a r c a s s composition. The models can be e a s i l y i n c o r p o r a t e d i n t o l i n e a r programming systems which are commonly used i n r a t i o n f o r m u l a t i o n . P o t t e r and McCarthy (1985) have developed such a model f o r tu r k e y s . The disadvantage of e m p i r i c a l l y d e r i v e d models i s t h a t they are s p e c i f i c to the data from which they were d e r i v e d and are t h e r e f o r e very d i f f i c u l t to apply to new and d i f f e r e n t s i t u a t i o n s . (2) Requirement models The second type of model has been c a l l e d the requirement model. Such a model i s b i o l o g i c a l l y d e s c r i p t i v e and p a r t i t i o n s the animal i n t o i t s components. The Hurwitz model (Hurwitz et a l . , 1978) of b r o i l e r growth i s a good example of a requirement model which p a r t i t i o n s the d i e t a r y requirements f o r amino a c i d s i n t o maintenance and the growth PIG GROWTH MODEL page 5 of f e a t h e r s and other body components. D. H i c k l i n g (1988), i n h i s paper presented to the 1988 Western N u t r i t i o n Conference i n Winnipeg, d e s c r i b e d a model f o r b r o i l e r s developed by Talpaz (1986) which was a refinement of the Hurwitz et al.(1978) model. Ta l p a z ' s model was used by t h i s author when developing a requirement model f o r b r o i l e r s i n e a r l y 1989 which r e p r e s e n t s the growth of b r o i l e r s found i n the F r a s e r V a l l e y (Dyble, 1989 unpublished). The advantage of requirement models i s t h a t they are r e l a t i v e l y easy to understand and develop i n c o n t r a s t to i n t e g r a t e d models. (3) I n t e g r a t e d models In t e g r a t e d models are b i o l o g i c a l l y - b a s e d models which s p l i t growth i n t o i t s components i n c l u d i n g p r o t e i n , ash, f a t and v^ater. These components are then s p l i t again. For example, f a t i s s p l i t i n t o the minimum amount of l i p i d a s s o c i a t e d with normal growth and the storage l i p i d which i s above the minimum. I n t e g r a t e d models i n c l u d e the r e l a t i o n s h i p between the animal and i t s environment. The b i o l o g i c a l b a s i s of these models allows them to be responsive to sub-maximal l e v e l s of growth. PIG GROWTH MODEL page 6 The f i r s t models of animal growth r e l a t i n g body weight to age were produced by Brody (1945). Whittemore and Fawcett (1976) and Whittemore (1976) were the f i r s t to demonstrate that data from many d i s c i p l i n e s c o u l d be s i m u l t a n e o u s l y s o l v e d through the use of computers to d e s c r i b e the growth of a p i g . T h i s was the f i r s t i n t e g r a t e d growth model. Whittemore subsequently developed a computer program (which was marketed i n the U.K. i n the e a r l y 1980's) c a l l e d the Edinburgh Micromodel P i g , which was used as p a r t of an a d v i s o r y s e r v i c e to simulate the outcome of changes i n p r o d u c t i o n systems. Emmans (1981) wrote about h i s 'work i n p r o g r e s s ' with a d e s c r i p t i o n of a model of the growth and feed i n t a k e of p o u l t r y , showing t h a t the same modelling concepts developed f o r p i g s c o u l d be used f o r p o u l t r y . Emman's model was w r i t t e n i n t o a FORTRAN program c a l l e d the 'Edinburgh Growth Model' which was l a t e r renamed the 'Edinburgh Model f o r B r o i l e r s ' . Development of i n t e g r a t e d models f o r swine i s proceeding at v a r i o u s r e s e a r c h c e n t r e s throughout the world (Moughan, 1987; Ewan et a l . , 1988; Black et a l . , 1986). I n t e r e s t i n mo d e l l i n g has developed to the p o i n t where the Wageningen A g r i c u l t u r a l U n i v e r s i t y i n the Netherlands, with the help of P.J. Moughan from Massey U n i v e r s i t y i n New PIG GROWTH MODEL page 7 Zealand, have sponsored a l e c t u r e course on growth modelling (Moughan et a l . , 1988). Other types of b i o l o g i c a l growth models have been developed which d e s c r i b e n u t r i e n t p a r t i t i o n i n g at the c e l l u l a r l e v e l and i n c l u d e complex b i o c h e m i c a l d e t a i l s (Stombaugh et a l . , 1980). Although these models may be v a l u a b l e , they were co n s i d e r e d by the author to be unduly complex f o r the needs of p r o d u c t i o n a g r i c u l t u r e . (4) Feed Intake of Swine A common f e a t u r e of t h e o r i e s of feed intake r e g u l a t i o n i s the c o n t r o l l i n g e f f e c t of blood c o n c e n t r a t i o n s of v a r i o u s compounds, i n c l u d i n g n u t r i e n t s , t h a t r e f l e c t the v u n d e p o s i t e d ' energy s t a t u s . The response mechanism may be de s c r i b e d as short-term ( i . e . meals) or long-term ( i . e . s e v e r a l days) depending on i t s c h r o n o l o g i c a l e f f e c t s . The complexity of systems which are hypothesized f o r feed intake r e g u l a t i o n suggests t h a t no one f a c t o r has a dominant c o n t r o l over f e e d i n g behaviour. The p h y s i o l o g i c a l c o n t r o l of feed intake has not been e x t e n s i v e l y s t u d i e d i n swine, but a review of feed intake of swine by Houpt (1983) o f f e r s an i n s i g h t i n t o hypotheses r e g a r d i n g short-term c o n t r o l . PIG GROWTH MODEL page 8 Glucostatic controls: Studies with i n s u l i n (Houpt et a l . , 1982) have shown that animals respond to deprivation of glucose by an increase in feed intake, but the mechanism i s thought to be an emergency control with l i t t l e role in the determination of meal size. Osmoreceptive controls: Studies reviewed by Houpt (1983) showed that hypertonic sugar solutions delivered d i r e c t l y to the duodenum produced a feedback reduction of feed intake. Cholecystokinin control: Administration of cholecystokinin has been e f f e c t i v e in reducing feed intake (Anika et a l . , 1981), thereby leading to the hypothesis that cholecystokinin released from the i n t e s t i n a l mucosa during meals acts as a negative feedback control. Gastrointestinal distention control: The idea of g a s t r o i n t e s t i n a l distention as an important stimulus for satiety feedback signals i s probably the oldest hypothesis known. On t h i s reasoning, i t could be hypothesized that swine feed, based on barley rather than less bulky corn, could reduce energy intake. Diets based on barley usually contain a lower energy concentration than corn-based diets because of the differences between the grains in energy content and the r e l a t i v e expense of fat sources which would be necessary to raise the energy content of the barley-based PIG GROWTH MODEL page 9 d i e t s . The improvements i n average d a i l y gain due to in c r e a s e d d a i l y energy i n t a k e a s s o c i a t e d with swine fed corn-based d i e t s are l i k e l y a s s o c i a t e d with the i n c r e a s e d energy content of these d i e t s r a t h e r than d i f f e r e n c e s i n dry matter i n t a k e . P o t e n t i a l d i f f e r e n c e s i n feed i n t a k e between d i e t s based on corn and d i e t s based on b a r l e y make feed i n t a k e estimates d e r i v e d from corn-based d i e t s d i f f i c u l t to e x t r a p o l a t e to p i g s r e c e i v i n g b a r l e y based d i e t s due to p o t e n t i a l e f f e c t s of g a s t r o i n t e s t i n a l d i s t e n t i o n on the c o n t r o l of feed i n t a k e . The e l u c i d a t i o n of long-term mechanisms of feed i n t a k e r e g u l a t i o n i s d i f f i c u l t because i n t e r a c t i o n s or modulation of c o n t r o l mechanisms i n the long-term make an i n t e r p r e t a t i o n necessary. The dominant theory r e g a r d i n g long-term c o n t r o l i s t h a t , a f t e r p e r i o d s of r e s t r i c t i o n or ov e r f e e d i n g , there i s a time when feed intake i s adjus t e d u n t i l body f a t r e t u r n s to the l e v e l preceding the i n i t i a l change (Martin et a l . , 1989). L i p o s t a t i c c o n t r o l : The l i p o s t a t i c theory has been reviewed by Ma r t i n et a l . (1989). The c e n t r a l premise of the theory r e v o l v e s around the concept t h a t feed intake i s r e g u l a t e d by the a b i l i t y of c i r c u l a t i n g s u b s t r a t e s to be i n c o r p o r a t e d i n t o adipose t i s s u e . S u b s t r a t e s i n c l u d e glucose, f a t t y a c i d s and other adipose t i s s u e m e t a b o l i t e s . PIG GROWTH MODEL page 10 Non-ruminant a d u l t animals are able to c o n t r o l feed intake or metabolic e f f i c i e n c y almost completely so t h a t a constant p r o p o r t i o n of body l i p i d i s maintained (Bray, 1984). The r e l a t i o n s h i p between d i e t a r y energy c o n c e n t r a t i o n and feed i n t a k e i s recognized by most feed i n t a k e equations which r e l a t e body weight and body weight gain to an expected intake of d i g e s t i b l e energy. The NRC p u b l i c a t i o n e n t i t l e d ' P r e d i c t i n g Food Intake of Food Producing Animals (1987)' d e t a i l s a number of equations which have been developed to estimate i n t a k e of d i g e s t i b l e energy from body weight. Ewan (1983) summarized data from 62 experiments i n v o l v i n g 8072 o b s e r v a t i o n s of 1490 pens of p i g s fed n u t r i t i o n a l l y adequate corn-soybean meal d i e t s under i d e a l c o n d i t i o n s and produced the equation DEi ( d i g e s t i b l e energy intake i n k c a l s per day) = 13162 (1 - (exp (-0.0176 B.W.))). NRC (1987) does not produce separate equations f o r barley-based intake and i t i s t h e r e f o r e assumed by NRC t h a t the corn-based equations w i l l h o l d true f o r other types of d i e t s . The form of the equation use by Ewan and others assumes an asymptote where feed intake i n c r e a s e s to a maximum l e v e l and then stays at t h a t l e v e l . The asymptote i s u s u a l l y not achieved u n t i l p i g s reach about 120 kgs body weight. PIG GROWTH MODEL page 11 There have been a number of papers r e p o r t i n g a maximum i n d a i l y i n t a k e b e i n g reached b e f o r e 120 kgs body weight and a d e c l i n e t h e r e a f t e r . The r e p o r t of G i l e s e t a l . (1981) shows a d e c l i n e i n d a i l y i n t a k e above 60 kgs body weight. I t i s u n c l e a r i f t h i s d e c l i n e i n f e e d i n t a k e was a s s o c i a t e d w i t h a poor h e a l t h s t a t u s or whether i t o c c u r e d as a r e s u l t of a d i e t - r e l a t e d p h y s i o l o g i c a l c o n t r o l . (5) I m p o r t a n t M o d e l l i n g Concepts (a) The U t i l i z a t i o n of Ingested Amino A c i d s The major p o r t i o n of i n g e s t e d amino a c i d s i s absorbed i n t o the p o r t a l b l o o d of the growing p i g and i s t r a n s p o r t e d t o the s i t e s of body p r o t e i n s y n t h e s i s . The p a t t e r n of absorbed amino a c i d s i n r e l a t i o n t o a p a t t e r n r e q u i r e d f o r the combined p r o c e s s e s of r e s y n t h e s i z i n g l o s t p r o t e i n and s y n t h e s i z i n g new p r o t e i n i n the body c e l l s i g n i f i c a n t l y a f f e c t s p r o t e i n a c c r e t i o n . The d i r e c t i o n p r o t e i n can f l o w would i n c l u d e the f o l l o w i n g : a f r a c t i o n of the amino a c i d s absorbed from the gut w i l l be u n a v a i l a b l e f o r p r o t e i n s y n t h e s i s because of s h o r t d u r a t i o n imbalances a t the c e l l u l a r l e v e l . These amino a c i d s w i l l be deaminated i n the l i v e r and the n i t r o g e n o u s component e x c r e t e d as u r i n a r y PIG GROWTH MODEL page 12 urea. The remaining balanced p r o t e i n w i l l be used to cover the c e l l ' s requirement f o r p r o t e i n maintenance, with the remainder being a v a i l a b l e f o r new body p r o t e i n s y n t h e s i s . Methods to d e f i n e p r o t e i n q u a l i t y i n terms of amino a c i d composition are a d e s i r a b l e component of model development. One such p r o t e i n e v a l u a t i o n method i s known as b i o l o g i c a l value. B i o l o g i c a l value was d e f i n e d by Whittemore et a l . (1979) as "... a s i n g l e numerical value a s c r i b e d to a p r o t e i n which giv e s an estimate of the r e l a t i o n s h i p between the e s s e n t i a l amino a c i d balance of the d i e t p r o t e i n and the e s s e n t i a l amino a c i d needs of the p i g " . The concept of an i d e a l (balanced) p r o t e i n becomes an i n t e g r a l p a r t of the concept of b i o l o g i c a l value; thus a d e f i n i t i o n i s warranted. An i d e a l p r o t e i n (or an i d e a l l y balanced p r o t e i n ) i s d e f i n e d as one that c o n t a i n s an i d e a l balance of both the i n d i v i d u a l e s s e n t i a l and the t o t a l ( e s s e n t i a l plus n o n e s s e n t i a l ) amino a c i d s needed f o r optimal growth of the animal. The i d e a l balance of amino a c i d s i s the p a t t e r n t h a t leads to the h i g h e s t u t i l i z a t i o n of the d i e t a r y p r o t e i n s as measured by a value such as b i o l o g i c a l v alue. The c l a s s i c a l d e f i n i t i o n of b i o l o g i c a l value i s the p r o p o r t i o n of absorbed n i t r o g e n t h a t i s r e t a i n e d by the body. B i o l o g i c a l value can be expressed by the PIG GROWTH MODEL page 13 Thomas-Mitchell equation (Lloyd et al.,1978) which i s as f o l l o w s : N i n -[(N feces - Met N) + (N u r i n e - Endog. N)] %B.V. = 100 • N intake - (N feces - Met N) Where N i n = n i t r o g e n intake N feces = f e c a l n i t r o g e n Met N = metabolic f e c a l n i t r o g e n (N l o s s on an N-free d i e t ) N u r i n e = u r i n a r y n i t r o g e n Endog. N = endogenous u r i n a r y n i t r o g e n (N l o s s on an N-free d i e t ) There are two d i f f e r e n t s c hools of thought r e g a r d i n g the best method f o r d e r i v i n g the p a t t e r n of an i d e a l p r o t e i n f o r p i g s . The ARC (1981) placed primary emphasis on the p a t t e r n of amino a c i d s i n p i g t i s s u e s and sow's milk. The NRC (1988) co n s i d e r e d these sources but placed primary emphasis on the data from many e m p i r i c a l experiments designed to determine amino a c i d requirements (Lewis, 1988). However, the amino a c i d p a t t e r n s d e r i v e d by the two groups are s i m i l a r , but not i d e n t i c a l , as shown i n Table 1. The i d e a l p r o t e i n f o r growing pigs which i s used to develop models a l s o d i f f e r s between model developers, as i n d i c a t e d by the comparison between two models i l l u s t r a t e d i n Table 2. PIG GROWTH MODEL page 14 Table 1. Amino A c i d P a t t e r n s of I d e a l P r o t e i n R e l a t i v e to Tryptophan NRC (1988) ARC (1981) A r g i n i n e 3.0 to 1.0 H i s t i d i n e 1. 8 2 . 3 I s o l e u c i n e 3.8 3.8 Leucine 5.0 7.0 Ly s i n e 7.0 to 6.0 7.0 Methionine & C y s t i n e 3.4 3.5 Ph e n y l a l a n i n e & T y r o s i n e 5. 5 6.7 Threonine 4.0 4.2 Tryptophan 1.0 1.0 V a l i n e 4.0 4.9 Table 2. Amino A c i d P a t t e r n of I d e a l P r o t e i n f o r Growing Pigs (g/kg i d e a l p r o t e i n ) Whittemore,1978 Massey (see Moughan et a l . , 1988) H i s t i d i n e 25 27 I s o l e u c i n e 40 36 . 7 Leucine 80 70. 3 Ly s i n e 70 79. 4 Methionine & C y s t i n e 40 43. 2 Ty r o s i n e & Phenylalanine 70 80 Threonine 40 47 Tryptophan 10 10 V a l i n e 50 52 . 5 T o t a l E s s e n t i a l Amino A c i d s 425 446 . 1 T o t a l N o n - e s s e n t i a l Amino Acids 575 553. 9 PIG GROWTH MODEL page 15 The p i g model i n the present paper i n c l u d e s a separate l i n e a r programming system (Optimal S o l u t i o n s 3 ) c o n t a i n i n g a r o u t i n e which c a l c u l a t e s the b i o l o g i c a l value of a f e e d s t u f f . The i d e a l p r o t e i n concept i s e x p l a i n e d below to show how the t o t a l i d e a l p r o t e i n intake i s used to c a l c u l a t e d the p r o t e i n r e t a i n e d by the p i g (which i s needed i n the model). I P t = IPm + IPr where I Pt = t o t a l i d e a l p r o t e i n intake IPm = i d e a l p r o t e i n of maintenance (0.004 T o t a l Body P r o t e i n ) IPr = i d e a l p r o t e i n of r e t e n t i o n (growth) IPt = IPm + IPr can be r e w r i t t e n as IPr = IPt - IPm which i s equal to Pr where Pr i s the t o t a l p r o t e i n r e t a i n e d . I P r = I P t - IPm = Pr (b) The Upper L i m i t to D a i l y P r o t e i n R e t e n t i o n The concept of maximum p r o t e i n d e p o s i t i o n i s a l s o very important to model development. The p r o t e i n a v a i l a b l e f o r r e t e n t i o n (where energy i s not l i m i t i n g ) can be u t i l i z e d up to the p o i n t of maximum p o t e n t i a l p r o t e i n d e p o s i t i o n , which i s dependent upon the g e n e t i c m a t e r i a l and the sex of the animal. The growth models of Whittemore et a l . (1976), Whittemore (1983), Moughan (1987) and Black et a l . (1986), PIG GROWTH MODEL page 16 a l l use values f o r maximum p r o t e i n d e p o s i t i o n per day. The maximum p r o t e i n d e p o s i t i o n i s represented by the symbol P r A . Excess p r o t e i n above the maximum p r o t e i n d e p o s i t i o n per day must be deaminated, with the n i t r o g e n excreted i n the u r i n e . The energy d e r i v e d from p r o t e i n deaminated i s i d e n t i f i e d i n the model and c a l l e d Qd. I t i s c a l c u l a t e d from the d i f f e r e n c e between the sum of the energy expended f o r urea s y n t h e s i s and the energy i n the ur i n e s u b t r a c t e d from the gross energy content of p r o t e i n . Thorbek (1975) and Carr et a l . (1977) have d e r i v e d the r e l a t i o n s h i p between P r A and l i v e weight and have d e f i n e d a r e l a t i o n s h i p where P r A i n c r e a s e s r a p i d l y during e a r l y l i f e , p l a t e a u s during the grower f i n i s h e r stages and then decreases towards zero at maturi t y . The p r o t e i n a v a i l a b l e f o r r e t e n t i o n w i l l be u t i l i z e d up to the p o i n t of maximum p r o t e i n d e p o s i t i o n , which i s e s t a b l i s h e d by the modeller, depending on an assessment of the g e n e t i c m a t e r i a l being modelled. Values f o r the maximum ra t e of p r o t e i n d e p o s i t i o n ( P r A ) d i f f e r between g e n e t i c types of pi g s and these have been q u a n t i f i e d i n Table 3. PIG GROWTH MODEL page 17 Table 3. Values f o r the maximum r a t e of p r o t e i n d e p o s i t i o n ( P r A ) i n White Breeds and s t r a i n s of p i g s used f o r the p r o d u c t i o n of meat i n Kgs/day (from Elements of Pi g Science by C o l i n Whittemore (1987)). E n t i r e Males Females C a s t r a t e s Grandparent breeding stocks 0.18 Improved h y b r i d s 0.14 Commercial c r o s s e s 0.13 U t i l i t y s t r a i n s 0.12 0.16 0. 12 0. 11 0. 10 0. 11 0. 10 0. 09 Values f o r P r A have been d e r i v e d by Whittemore (1987) but the equations developed by Black et a l . (1986) demand f u r t h e r a n a l y s i s . S i m i l a r equations f o r western Canada should be sought as '...a l a c k of s u i t a b l e data on Pr, i n e v i t a b l y hampers a p p l i c a t i o n of a growth model i n p r a c t i c e ' (Moughan et a l . , 1988). The equations of Black et a l . (1986) f o r the p o t e n t i a l r a t e of energy and n i t r o g e n r e t e n t i o n f o r p i g s are as f o l l o w s : G AEB = kE ( WAaE ( (E AB - EB)/E AB)) GANB = kN ( WAaN ((N AB - NB)/N AB)) where; G AEB= P o t e n t i a l energy d e p o s i t i o n i n the body (MJ/day) GANB= P o t e n t i a l n i t r o g e n gain i n the body (g/day) kE = Constant f o r r a t e of gain i n body energy (MJ/day/W AaE) kN = Rate of gain of body n i t r o g e n constant (kg/day/W AaE) E AB = Energy content of the body at ma t u r i t y (MJ) PIG GROWTH MODEL page 18 N AB = Ni t r o g e n content of the body at m a t u r i t y (kg) EB = Amount of body energy at weight W (MJ) NB = Weight of body n i t r o g e n at weight W (kg) aE = Constant f o r c a l c u l a t i o n of p o t e n t i a l energy gain aN = Constant f o r p o t e n t i a l body n i t r o g e n gain. Values f o r kE, aE, kN, aN, and N AB are r e q u i r e d f o r each genotype. Black et a l . (1986) developed values f o r genotypes r e p r e s e n t i n g f a s t growing, lean pigs from the l a r g e commercial p i g g e r i e s i n A u s t r a l i a and f o r slower growing, f a t t e r genotypes t y p i c a l of s m a l l e r commercial p i g g e r i e s as shown i n Table 4. Table 4. Values f o r the parameters t h a t d e f i n e the rate of of growth and composition of the body f o r d i f f e r e n t genotypes Parameter Boars G i l t C a s t r a t e PIGS FROM LARGE COMMERCIAL PIGGERIES (aE = 0.6, aN = 0.5) kE (MJ/day/W AaE) 1.95 1.90 2.00 E A B (MJ) 3800 4000 4000 kN (g/day/W AaN) 0.0042 0.0042 0.0038 N AB (kg) 5.76 4.65 4.65 PIGS FROM SMALL COMMERCIAL PIGGERIES (aE = 0.4, aN = 0.2) kE (MJ/day/W*aE) 4 . 10 4. 00 4 . 20 E"B (MJ) 3800 4000 4000 kN (g/day/W*aN) 0.0119 0. 0119 0. 0108 N AB (kg) 4. 20 3. 40 3. 40 PIG GROWTH MODEL page 19 The concepts of p r o t e i n d e p o s i t i o n have been mo d i f i e d s i n c e Whittemore and Fawcett (1976) f i r s t proposed t h e i r model, with the model of Black et a l . (1986) d i f f e r i n g c o n c e p t u a l l y from the former, as reviewed by Campbell (1987). Whittemore and Fawcett (1976) proposed t h a t d a i l y p r o t e i n d e p o s i t i o n by p i g s r e c e i v i n g a protein-adequate d i e t responded l i n e a r l y to energy intake up to a maximum p o i n t at which i t plateaued. T h i s premise has been reco g n i z e d as an o v e r s i m p l i f i c a t i o n , with the ARC (1981) suggesting t h a t as i d e a l p r o t e i n intake i n c r e a s e s , the e f f i c i e n c y of u t i l i z a t i o n of i d e a l p r o t e i n f o r p r o t e i n d e p o s i t i o n i n the p i g decreases i n a c u r v i l i n e a r manner. Pigs l e s s than 50 kgs are g e n e r a l l y unable to consume s u f f i c i e n t energy, even when o f f e r e d d i e t s of high energy c o n c e n t r a t i o n , to reach the p l a t e a u f o r p r o t e i n growth. With such p i g s , an i n c r e a s e i n energy i n t a k e leads to an i n c r e a s e d r a t e of d e p o s i t i o n of p r o t e i n , water, f a t and ash and thus growth r a t e . I t has been suggested by Whittemore and Fawcett (1976) and Whittemore (1986) t h a t f o r p i g s of the same sex and genotype, the slope of the l i n e a r component of the r e l a t i o n s h i p between energy intake and p r o t e i n d e p o s i t i o n and the p l a t e a u , are l a r g e l y independent of l i v e weight. PIG GROWTH MODEL page 20 T h i s p r o p o s i t i o n i s i n c o n s i s t e n t with the d e c l i n e i n the r a t e and e f f i c i e n c y of growth and i n c r e a s e i n c a r c a s s f a t n e s s which commonly accompany i n c r e a s e s i n l i v e weight i n p i g s given the same l e v e l of energy i n t a k e , even a f t e r d i f f e r e n c e s i n maintenance energy requirements have been allowed f o r . The c u r r e n t theory of p r o t e i n d e p o s i t i o n when energy i s not l i m i t i n g ( i . e . when there i s not an e x c e s s i v e deamination of amino a c i d s f o r the purpose of energy p r o d u c t i o n ) , i s t h a t with i n c r e a s i n g d i e t a r y p r o t e i n , there i s an i n e v i t a b l e l o s s of amino a c i d s to deaminative pathways. The t h e o r i e s used to prove the e x i s t e n c e of t h i s l o s s i n c l u d e the theory of enzyme s a t u r a t i o n k i n e t i c s and the law of mass a c t i o n . The expected l o s s i n the e f f i c i e n c y of u t i l i z a t i o n of p r o t e i n y i e l d s a c u r v i l i n e a r response to i n c r e a s e d d i e t a r y p r o t e i n as P r A i s approached. Whittemore (1983) i n t r o d u c e d an e f f i c i e n c y f a c t o r , a (a = 0.85 to 0.90) by which he decreased p r o t e i n d e p o s i t i o n when P r A i s approached as a s i m p l i f i e d method of d e a l i n g with the i n e f f i c i e n c y . P r A has been d i f f i c u l t to demonstrate e x p e r i m e n t a l l y but Campbell (1987) has been able to show d i f f e r e n c e s i n P r A f o r g i l t s and boars, with boars a c h i e v i n g a higher p r o t e i n d e p o s i t i o n before the p l a t e a u i s reached. He a l s o PIG GROWTH MODEL page 21 demonstrated t h a t improved genotypes had a higher p l a t e a u as w e l l as an i n c r e a s e d slope of the l i n e a r response phase of p r o t e i n growth. The i n t e r e s t i n g comparison between Whittemore's model and B l a c k ' s model can be made with regards to the r e l a t i o n s h i p between l i v e weight and p o t e n t i a l p r o t e i n and energy r e t e n t i o n (see F i g u r e 1). There are c u r r e n t l y two schools of thought concerning the form of the r e l a t i o n s h i p between l i v e weight and p o t e n t i a l p r o t e i n and energy a c c r e t i o n . The f i r s t presumes t h a t the responses are q u a d r a t i c i n nature with maximum p r o t e i n d e p o s i t i o n o c c u r r i n g at 70 to 90 kg depending on genotype and sex and then g r a d u a l l y f a l l i n g to zero when mature s i z e i s a t t a i n e d (Black et a l . , 1986). The second a l s o assume t h a t p r o t e i n d e p o s i t i o n i n c r e a s e s from b i r t h but reaches a maximum r e l a t i v e l y e a r l y i n l i f e (20 to 40 kgs) and remains constant over a wide range of l i v e weights (up to 120 kgs depending on sex and genotype) before f a l l i n g to zero at m a t u r i t y (Whittemore et a l . , 1976). The descending side of the response curve needs values f o r mature body s i z e and mature body composition before the best estimate f o r P r A can be de s c r i b e d . p a g e 22 Figure 1 POTENTIAL PROTEIN DEPOSITION AS A FUNCTION OF BODY WEIGHT. C A S E © SUGGESTS A MAXIMUM AT 40 TO 50% OF MATURE WEIGHT (Black et al., 1986). CASE © SUGGESTS A PLATEAU ATTAINABLE EARLY IN LIFE (Whittemore et al., 1976). Daily lean growth Proportion of mature weight Case CpBlack et al., 1986. C a s e @ Whittemore et al., 1976. PIG GROWTH MODEL page 23 (c) Energy M o d e l l i n g Concepts An understanding of energy i n metabolism i s necessary f o r development of model equations. M e t a b o l i z a b l e energy i s e i t h e r r e t a i n e d i n p r o t e i n or f a t t y t i s s u e s , used f o r the work of c r e a t i n g those t i s s u e s (and bone), or used f o r the work of maintenance (Em) and c o l d thermogenesis. A l l work energy f i n a l l y leaves the body as heat. As the p i g grows, the energy used f o r maintenance i n c r e a s e s with the s i z e of the animal. In the i n i t i a l stages of growth, p r o t e i n d e p o s i t i o n may i n c r e a s e and the energy content of the p r o t e i n d e p o s i t i o n i n c r e a s e s a c c o r d i n g l y . A f t e r a body weight of about 40 kgs (depending on when P r A i s ac h i e v e d ) , the amount of energy going d a i l y i n t o new body p r o t e i n remains f a i r l y s t a b l e . Conversely, the energy which i s d e p o s i t e d d a i l y i n new f a t i n c r e a s e s as the p i g grows and eats more. The s y n t h e s i s of p r o t e i n r e q u i r e s about three times the energy t h a t f a t does (45 vs 14 MJ/kg). T h i s i s because the r e s t r u c t u r i n g which i s necessary to achieve the c o r r e c t balance of amino a c i d s from the mixture s u p p l i e d by the d i e t r e q u i r e s energy i n a d d i t i o n to the energy r e q u i r e d f o r l i n k i n g amino a c i d s together (about 7.3 MJ ME/kg new p r o t e i n formed). Another energy PIG GROWTH MODEL page 24 c o s t i n p r o t e i n s y n t h e s i s r e l a t e s to the energy c o s t of p r o t e i n r e c y c l i n g . The expenditure of 7.3 MJ ME/kg f o r forming new p r o t e i n can r e a d i l y be r a i s e d at l e a s t s i x f o l d to 45 MJ or more when the energy expended i n p r o t e i n s y n t h e s i s and r e c y c l i n g i s i n c l u d e d (Whittemore et a l . , 1979). Armstrong (1969) presented a b i o c h e m i c a l a n a l y s i s of the energy c o s t of p r o t e i n a c c r e t i o n . Armstrong c a l c u l a t e d t h a t 8 - 1 2 moles of adenosine t r i p h o s p h a t e (ATP) are r e q u i r e d to l i n k t o gether one mole of amino a c i d s . I f 50 KJ/mole ATP i s allowed and an e f f i c i e n c y of formation of 60% assumed, each mole of ATP r e q u i r e s 83.7 KJ ME. Given t h a t the average molecular weight of the amino a c i d s i n p i g p r o t e i n i s 110 to 120, then the energy used to form 1 kg of p r o t e i n would be 5.6 to 9.1 MJ, with an average of 7.3 MJ. S t a t i s t i c a l a n a l y s i s of data r e l a t i n g to body composition and n u t r i e n t i n t a k e {Kielanowski, 1975) suggests t h a t the energy r e q u i r e d f o r p r o t e i n a c c r e t i o n during growth i s c o n s i d e r a b l y h i g h e r than the b i o c h e m i c a l estimate of about 7.3 MJ/kg f o r p r o t e i n s y n t h e s i s . A flow c h a r t of Armstrong's c a l c u l a t i o n s i s shown below: (a) Weight of one mole of amino a c i d s = 110-120 gms. PIG GROWTH MODEL page 25 (b) Moles per kg amino a c i d s = 1000/110=9.09 , 1000/115=8.69 1000/120=8.33 moles/kg. (c) Energy i n each mole amino a c i d s = 83.7 KJ ME. (d) Energy to l i n k amino a c i d s = 8-12 moles ATP/mole amino a c i d s . Energy to form 1 kg p r o t e i n = b (c (d)) = 9.09 ( 83.7 ( 8 to 12)) = 5.6 to 9.1 MJ Therefore the energy used to form one kg of p r o t e i n ranges from 5.6 to 9.1 MJ with an average of 7.3 MJ as o u t l i n e d by Armstrong (1969). Van Es (1980) used a d i f f e r e n t method of d i r e c t l y e s t i m a t i n g energy c o s t s of p r o t e i n a c c r e t i o n . He c a l c u l a t e d t h a t the complete o x i d a t i o n of 1 mole of glucose (heat of combustion 2814 kJ/mole) i s considered to y i e l d 38 moles of ATP. T h e r e f o r e , the s y n t h e s i s of 1 mole of ATP r e q u i r e s (2814/38) 74 kJ. He f u r t h e r c a l c u l a t e s the t h e o r e t i c a l ME c o s t of p r o t e i n s y n t h e s i s of 100 gms of average p r o t e i n c o n t a i n i n g 2400 kJ as 3.2 MJ ME. Van Es's c a l c u l a t i o n f o r the s y n t h e s i s of 100 gms of average p r o t e i n i s shown i n Table 5. Armstrongs (1969) numbers f o r the s e c t i o n s of Van Es's c a l c u l a t i o n s have been i n c l u d e d f o r comparison purposes. PIG GROWTH MODEL page 26 Table 5. A Comparison of the C a l c u l a t i o n s of Van Es (1980) and Armstrong (1969) f o r the Energy Cost of P r o t e i n D e p o s i t i o n Van Es 1980 (Armstrong j | 1969 Moles ATP f o r s y n t h e s i s of 1 of p e p t i d e s from amino a c i d s mole 5 | 8 - 1 2 | Conversion to 100 grams from weight of 115 grams/mole mole 100 / 115 | 100 / 110 |115 or 120 Energy c o s t of s y n t h e s i s of of ATP (KJ ME) 1 mole 74 | 83.7 | MJ ME to form 1 kg p r o t e i n 3.2 | 5.6 - 9.1 The c a l c u l a t i o n above i s used to i n d i c a t e t h a t although the methods used by Van Es (1980) and Armstrong (1969) f o r c a l c u l a t i n g the energy c o s t of p r o t e i n formation d i f f e r e d , when they are converted i n t o a s i m i l a r method of a n a l y s i s , a c o r r e l a t i o n i s found between the two methods. The l a r g e d i f f e r e n c e i n t h e i r d e r i v e d energy c o s t s of p r o t e i n formation stems from d i f f e r e n c e s i n t h e i r estimates of the number of moles of ATP used f o r the s y n t h e s i s of 1 mole of p e p t i d e s . These b i o c h e m i c a l c a l c u l a t i o n s of the energy c o s t of p r o t e i n d e p o s i t i o n d i f f e r from estimates o u t l i n e d by Whittemore (1976) as f o l l o w s : The energy content of p r o t e i n , PIG GROWTH MODEL page 27 as measured by c a l o r i m e t r y , i s 23 - 24 MJ per kg. Whittemore suggests the t o t a l energy c o s t of p r o t e i n d e p o s i t i o n to be 69 MJ/kg with p r o t e i n c o n t a i n i n g 23 - 24 MJ/kg. Accor d i n g to these c a l c u l a t i o n s , the energy c o s t of forming p r o t e i n by d i f f e r e n c e i s about 45 MJ's/kg. The b i o c h e m i c a l estimates of the energy c o s t s of peptide bond formation o u t l i n e d by Armstrong (1969) and Van Es (1980) range from 3.2 - 9.1 MJ with Whittemore (1987) suggesting a value of 5 MJ as a p p r o p r i a t e . The d i f f e r e n c e between 5 MJ by c a l c u l a t i o n and the 45 MJ suggested by animal t r i a l s as a p p r o p r i a t e , i s the energy used f o r p r o t e i n turnover. As o u t l i n e d above, Whittemore (1987) suggests a value f o r the energy c o s t of peptide bond formation of 5 MJ with the remainder of the energy used f o r p r o t e i n formation t i e d up i n p r o t e i n turnover. The r a t i o s of new p r o t e i n a c c r e t e d to t o t a l p r o t e i n turnover i s suggested to range from 1 : 5 i n 20 kg animals to 1 : 8 i n 100 kg animals. The study p u b l i s h e d by P u l l a r and Webster (1977) fol l o w e d Whittemore's (1976) o r i g i n a l work on growth models and suggests some d i f f e r e n c e s i n energy c o s t s of p r o t e i n and f a t d e p o s i t i o n . Whittemore's (1976) values f o r p r o t e i n and f a t d e p o s i t i o n are 69 and 54 MJ/kg r e s p e c t i v e l y while P u l l a r and Webster (1977) developed e x p e r i m e n t a l l y a value of approximately 54 MJ/kg f o r both p r o t e i n and f a t . PIG GROWTH MODEL page 28 The energy c o s t s of p r o t e i n and f a t d e p o s i t i o n used i n the i n t e g r a t e d growth models developed to date are d e r i v e d from e m p i r i c a l estimates. In the case of f a t d e p o s i t i o n , energy val u e s are q u i t e c o n s i s t e n t while e m p i r i c a l l y d e r i v e d estimates of p r o t e i n d e p o s i t i o n c o s t vary widely (Tess, 1981). The d i s c r e p a n c i e s between t h e o r e t i c a l and e m p i r i c a l values of the energy c o s t s of p r o t e i n d e p o s i t i o n were demonstrated by the work of Van Es (1980) and by P u l l a r and Webster (1977) as mentioned e a r l i e r . The e m p i r i c a l methods of P u l l a r and Webster (1977) use the s t a t i s t i c a l a p p o r t i o n i n g of m e t a b o l i z a b l e energy intake to maintenance, p r o t e i n r e t e n t i o n and l i p i d r e t e n t i o n . The p o s s i b l e shortcomings of t h i s procedure (Moughan et a l . , 1988) i n c l u d e d ; (a) a l l three r e t e n t i o n c o s t s are h i g h l y c o r r e l a t e d , (b) the energy r e t a i n e d as p r o t e i n i s a small f r a c t i o n of t o t a l m e t a b o l i z a b l e energy, (c) the values of p r o t e i n and f a t d e p o s i t i o n are a f f e c t e d by d i e t composition and (d) estimates of p r o t e i n d e p o s i t i o n c o s t s may vary with age, l i v e w e i g h t and r a t e of gain. The estimates of p r o t e i n d e p o s i t i o n c o s t s are c a l c u l a t e d by r e g r e s s i o n and are l i k e l y to c o n t a i n p a r t of the c o s t of p r o t e i n turnover. New m o d e l l i n g procedures are l i k e l y to i n c l u d e the energy c o s t s of p r o t e i n turnover as p a r t of the maintenance energy and then base the energy c o s t s of p r o t e i n d e p o s i t i o n on a PIG GROWTH MODEL page 29 t h e o r e t i c a l approach s i m i l a r to t h a t used by Armstrong (1969) and Van Es (1980). The l a r g e d i s c r e p a n c i e s c u r r e n t l y e x i s t i n g i n the t h e o r e t i c a l approach, with estimates of the energy c o s t p r o t e i n formation v a r y i n g from 3.2 to 9.1 MJ/kg p r o t e i n formed, make estimates based on these a n a l y s i s f a r l e s s accurate than the e m p i r i c a l work of P u l l a r and Webster ( 1977 ) . PIG GROWTH MODEL page 30 (IV) PIG MODEL DEVELOPMENT The p i g growth model o u t l i n e d below i s an i n t e g r a t e d model which has been developed w i t h components d e r i v e d m a i n l y from the papers of Whittemore and Fawcet t (1976), Whittemore (1987), B l a c k e t a l . (1986) and Ewan (1988). One of the problems w i t h i n t e g r a t e d models i s the tendency t o use d a t a d e v e l o p e d by the model i n l a t e r c a l c u l a t i o n s . T h i s c r e a t e s c i r c u l a r t y pe e r r o r s where e q u a t i o n s can i n c l u d e t h e i r own o u t p u t as p a r t of the i n p u t . A u s e f u l method of a v o i d i n g c i r c u l a r e r r o r s has been deve l o p e d t h r o u g h the use of a f i r s t a p p r o x i m a t i o n of growth as d e s c r i b e d by a s e r i e s of 'Gompertz E q u a t i o n s ' (Gompertz ( 1 8 2 5 ) ) . A Gompertz f u n c t i o n i s an e q u a t i o n of the form; B.W. = exp (-exp [-k ( t - t ' ) ] ) where B.W. i s body weight ( k g s ) , k i s a c o n s t a n t and t and t ' are time v a r i a b l e s . The Gompertz f u n c t i o n was f i r s t used f o r a c t u a r i a l purposes and was not used as a growth f u n c t i o n u n t i l much l a t e r (Windsor ( 1 9 3 2 ) ) . W i l s o n (1977) reworked Gompertz's e q u a t i o n s i n t o a form (as f o l l o w s ) ; B.W. = A exp (-B exp ( - k ( t ) ) ) where B.W. = body weight (kgs) A = mature body weight (kgs) PIG GROWTH MODEL page 31 B = rate constant k = rate constant t = time (days) The Gompertz f u n c t i o n i n f l e c t s at B.W. = A/e. Moore (1985) has d e s c r i b e d the d e r i v a t i o n of curves which can be used to d e s c r i b e animal growth from embryo to a d u l t . The curves are s p l i t i n t o Type A and Type B curves, depending on the complexity and t h e r e f o r e f l e x i b i l i t y of the necessary curves. Type A curves are curves which take the shape of the growth of 'normal' ad l i b . fed p i g s and are r e l a t i v e l y i n f l e x i b l e , with a s i n g l e p o i n t of i n f l e c t i o n . Type B curves are d e s c r i b e d as more f l e x i b l e curves which would allow f o r m u l t i p l e i n f l e c t i o n s depending on such c o n t r i b u t o r y f a c t o r s as compensatory g a i n . The curves d e s c r i b e d by Moore (1985) are i n t e r e s t i n g because they are d e r i v e d from very simple assumptions of growth which can f i t any growing animal where age and mature weight are s p e c i f i e d . He s t a r t s with two parameters, u and q, which are s c a l e d s i z e and age v a r i a b l e s . The parameter u r e p r e s e n t s a degree of m a t u r i t y , c a l c u l a t e d as body weight d i v i d e d by mature weight. The parameter q r e p r e s e n t s metabolic age (day/kg A0.27) as a f r a c t i o n of mature age (mature age = 1) c a l c u l a t e d as q = ( t - 3.5)/A A0.27 (A=Mature weight). T h i s equation w i l l have a f i r s t and second d e r i v a t i v e where the f i r s t d e r i v a t i v e (du/dq) PIG GROWTH MODEL page 32 r e p r e s e n t s growth r a t e and the second d e r i v a t i v e (d A2u/d A2q) r e p r e s e n t s growth a c c e l e r a t i o n . The second d e r i v a t i v e needs to have three zeros at u = 0 ( c o n c e p t i o n ) , u = 1 ( f u l l m a turity) and u = u l where u l i s the degree of m a t u r i t y at maximum growth r a t e (or the p o i n t of i n f l e x i o n ) which i s s a t i s f i e d by the f o l l o w i n g equation: d A2u/d A2q = (u ) (1 - u) ( u l - u) (2k A2 ) I n t e g r a t i n g the f u n c t i o n with r e s p e c t to q y i e l d s a q u a d r a t i c equation r e p r e s e n t i n g growth r a t e : du/dq = (u )•(1 - u) (k ) T h i s equation has zeros at u = 0 and u = 1, but o n l y i f u l i s f i x e d at u l = 0.5 i n d A2u/d A2q (an i n f l e x i o n a t the midpoint of the c u r v e ) . A second i n t e g r a t i o n with r e s p e c t to q y i e l d s a s t a n d a r d i z e d growth equation which i s a simple l o g i s t i c f u n c t i o n : u = [ 1 + e x p ( ( - k ) ( q ) ) ] A - 1 T h i s i s the d e r i v a t i o n of a simple growth f u n c t i o n which has been shown to h o l d across most domestic animals i n c l u d i n g c a t t l e , p i g s and chickens and t h i s i n d i c a t e s a commonality of growth amongst s p e c i e s modelled. The d e r i v a t i o n of the growth curves d e s c r i b e d by Moore (1985) i s probably s i m i l a r to the d e r i v a t i o n used by Gompertz when he PIG GROWTH MODEL page 33 developed h i s curves. The curves developed by Moore (1985) c o u l d be used as an a l t e r n a t i v e to the Gompertz type curves i f a b e t t e r f i t with observed data was found. (1) Feed Intake Section A 'Gompertz Equation' of the type d e s c r i b e d by Wilson (1977) was developed f o r the t h e s i s growth model i n the form; B.W. = A exp (-B exp ( - k ( t ) ) ) where B.W. = Body weight (kg) A = Mature Body Weight = 164 kg (estimate based on NRC (1988) mature sow weight). B = Rate constant = 4.46 k = Rate constant = 0.015 to 0.010 t = Time i n days An equation which f i t growth data c o l l e c t e d by t h i s author (Dyble, 1989 unpublished) on F r a s e r V a l l e y farms (with v a r i e d genotypes and environments) was as f o l l o w s : B.W. = 164 (exp ( -4.46 exp (-0.014 ( t ) ) ) ) A comparison between the 'Gompertz e x p o n e n t i a l f u n c t i o n ' and growth curves c o l l e c t e d by t h i s author i n the F r a s e r V a l l e y over a range of genotypes and environmental c o n d i t i o n s i s i l l u s t r a t e d by F i g u r e 2. I t was d i s c o v e r e d t h a t by m a n i p u l a t i n g the r a t e constant (k) from the 0.014 i n the equation above, a range of growth curves c o u l d be PIG GROWTH MODEL page 34 cr e a t e d with the corresponding days to market (~100 kgs) as f o l l o w s : k = = 0 .015 days to market = 147 k = = 0 .014 days to market = 158 k = = 0 .013 days to market = 169 k = = 0 .012 days to market = 182 k = = 0 .011 days to market = 201 k = • 0 .010 days to market = 220 F i g u r e 3 r e p r e s e n t s the growth curves d e s c r i b e d above with days to 100 kgs ranging from 147 to 220. F i g u r e 4 i l l u s t r a t e s those same growth curves as they approach mature body weight e x t r a p o l a t e d to a one year p e r i o d . F i g u r e 5 d e p i c t s the f i r s t 10 weeks of growth. The f i r s t 10 weeks of growth are important to i d e n t i f y as they u s u a l l y r e p r e s e n t the p e r i o d when growth r a t e can be economically manipulated to improve age to market through n u t r i t i o n a l means. The growth curve i s of a general sigmoid shape with the f i r s t p a r t of the curve o f t e n c a l l e d the a c c e l e r a t i o n phase, the more l i n e a r middle c a l l e d the c r u i s i n g phase and the end of the curve c a l l e d the d e c e l e r a t i o n phase. At about ten weeks of age, pi g s g e n e r a l l y leave the a c c e l e r a t i o n phase and ent e r the c r u i s i n g phase, which g e n e r a l l y c a r r i e s through to market weight. The c r u i s i n g phase i s an area of constant growth where the g e n e t i c a l l y d e s c r i b e d upper l i m i t of d a i l y p r o t e i n d e p o s i t i o n u s u a l l y c o n t r o l s growth. During the a c c e l e r a t i o n phase, d a i l y growth r a t e i s u s u a l l y not l i m i t e d F i g u r e 2: H Comparison Between a 'Gonpertz f u n c t i o n ' and a Growth Curve C o l l e c t e d Over a Hide Range of" Genotypes and Environmental Con d i t i o n s F i g u r e 3: Graph of a "Gompertz f u n c t i o n ' Designed to Represent Grouth Curves from B i r t h t o 100 kgs f o r Market Ages Ranging from 147 to 220 Dags to Market F i g u r e 4: Graph af a 'Gompertz f u n c t i o n ' Designed to Represent Growth Curves from B i r t h to a Year of Rge f o r Market Ages Ranging from 147 to 220 Days t o Market 170 DAYS OF AGE • 147 + 1 5 8 O 169 A 182 X 201 V 2 2 0 gure 5: Graph of a 'Gompertz f u n c t i o n " Designed t o Represent Growth Curves from B i r t h to 70 Dags of Rge f o r Market flgss Ranging from 147 t o 220 Dags t o Market PIG GROWTH MODEL page 39 by maximum p o s s i b l e d a i l y p r o t e i n d e p o s i t i o n . The a c c e l e r a t i o n phase i s important when manipulating p i g pr o d u c t i o n , as the growth rate to market can be economically and p h y s i o l o g i c a l l y changed through supplementation of p r o t e i n d u r i n g t h i s p e r i o d before the upper g e n e t i c l i m i t to d a i l y p r o t e i n d e p o s i t i o n c o n t r o l s p r o t e i n a c c r e t i o n . During the a c c e l e r a t i o n phase, energy intake r a t h e r than g e n e t i c l i m i t a t i o n c o n t r o l s any improvement i n growth r a t e s and p r o t e i n a c c r e t i o n . T h i s allows manipulations of p r o t e i n or energy d e n s i t i e s of d i e t s by n u t r i t i o n i s t s to improve economics of gain. The Gompertz equation can be solv e d f o r k as f o l l o w s so t h a t an estimated age to 100 kgs can be a s c e r t a i n e d , k = In [(In((B.W.)/A)) ( ( l / - B ) ) / t ] where B.W. 4 i s 100 kgs and t i s the age (days) a t which 100 kgs i s expected to be reached. Equations which f o l l o w t h a t are separated from the t e x t by l i n e s above and below, are the equations used i n the p i g model developed i n t h i s t h e s i s . PIG GROWTH MODEL page 40 The f i r s t approximation of the feed i n t a k e equation: Feed intake (kg/pig/day) [Ewan, 1986] =• 13162 (l-(exp(-0.017 6(B.W.))))/(DE) (Where B.W. i s d e r i v e d from the Gompertz (1825) equation and DE re p r e s e n t s the d i g e s t i b l e energy value of the feed i n k c a l per kg.) D a i l y v o l u n t a r y feed intake of growing p i g s i s p r e d i c t e d by e s t i m a t i n g D.E. consumption under thermoneutral c o n d i t i o n s (Ewan, 1986) and then modifying the int a k e ; acc o r d i n g to the c o n d i t i o n s being modelled. The equation above r e p r e s e n t s intake between 10 and 120 kgs under thermoneutral c o n d i t i o n s . The above equation i s based on equal numbers of barrows and g i l t s . C o r r e c t i o n s f o r d e v i a t i o n s from equal numbers of barrows and g i l t s can be made by the f o l l o w i n g equation: Percent d e v i a t i o n = (0.2142 B.W.) - (0.00133 B.W.A2) - 4.42 The percent d e v i a t i o n i s added f o r barrows and s u b t r a c t e d f o r g i l t s . PIG GROWTH MODEL page 41 P i g s per pen adjustment c o r r e c t i o n : Adjustment (kg/day) = [(pigs/pen) - 5 ] (-0.0025) [ f o r p i g s l e s s than 50 k i l o s ] The equation was developed (R. Ewan, pe r s o n a l communication) f o r pigs l e s s than 50 kgs where every p i g per pen over 5 decreases intake per p i g by 0.25 %. A f t e r 50 kgs body weight, the equation (R. Ewan, pe r s o n a l communication) i s as f o l l o w s : Adjustment (kg/pig/day) = [(pigs/pen) - 4 ] (0.0032) where p i g s per pen g r e a t e r than f o u r i n c r e a s e s i n t a k e per p i g by 0.32 % up to a maximum of t h i r t y p i g s per pen where i t p l a t e a u s . P e l l e t e d feed equation: A 3.1 % r e d u c t i o n (R. Ewan, pers o n a l communication) i n feed i n t a k e occurs when feed i s p e l l e t e d . Space per p i g and EAT adjustment(%) equation: equation 1: (0.4293(space/pig) - (02 0 2 5 ( ( s p a c e / p i g ) A 2 ) ) + 0.7725)(EAT) and equation 2: ((0. 7 ( s p a c e / p i g ) ) - ( 0 . 3 2 ( ( s p a c e / p i g ) A 2 ) ) + 0.6165)(EAT) Note : EAT = e f f e c t i v e ambient temperature. Equation 1 i s used when body weight i s l e s s than 50 kgs and equation 2 i s PIG GROWTH MODEL page 42 used over 50 kgs body weight. Space/pig r e p r e s e n t s the space per p i g i n square meters per p i g (Appendix 2, page 5). Adjustment f o r temperature r e q u i r e s c a l c u l a t i o n of the EAT as d e s c r i b e d by Bruce and C l a r k (1979) as f o l l o w s : EAT i s c a l c u l a t e d by a d j u s t i n g ambient temperature f o r a i r speed and f l o o r i n g type. These values range from a ten degree c e l s i u s decrease i n e f f e c t i v e temperature a s s o c i a t e d with an a i r speed of 1.5 meters per second to an in c r e a s e i n e f f e c t i v e temperature of fou r degrees c e l s i u s with deep straw bedding. A value f o r To (EAT a s s o c i a t e d c r i t i c a l temperature) i s needed (NRC, 1987) and c a l c u l a t e d from the f o l l o w i n g r e l a t i o n s h i p ; To = 26 - (0.0614 B.W.) Within the EAT range of 5 to 30 degrees C, adjustments to a feed intake p r e d i c t i o n f o r temperature would be as f o l l o w s : Percent change = 0.0165 (To - EAT) (2) I n i t i a l B o d y C o m p o s i t i o n S e c t i o n I n i t i a l b o d y c o m p o s i t i o n e q u a t i o n s : Pigs normally enter the g r o w i n g - f i n i s h i n g p r o d u c t i o n stage at 20 to 25 kgs l i v e weight. A model to p r e d i c t growth r e q u i r e s an estimate of i n i t i a l body composition f o r PIG GROWTH MODEL page 43 the p e r i o d under i n v e s t i g a t i o n . Body f a t content of weaners v a r i e s depending on the c o n d i t i o n s under which the pigs have been grown. Whittemore (1983) approached the problem by g i v i n g a value f o r f a t content of weaners based on a v i s u a l a p p r a i s a l . Whittemore's values f o r f a t are as f o l l o w s ; t h i n p i g s = 0.07 B.W.; average p i g s = 0.10 B.W.; and well-rounded p i g s = 0.15 B.W.. The values f o r the other empty body components used by Whittemore are as f o l l o w s ; Po (empty body p r o t e i n ) = 0.134 (We - L t ) A 1 . 1 2 0 [We = empty body weight and L t = weight of body f a t ] ; Ao (empty body ash) = 0.03 B.W.; and We (empty body weight) = 0.95 B.W.. Wood and Groves (1965) analyzed body composition of Canadian p i g s i n r e l a t i o n to age and weight. The p i g s now grown i n Canada have changed s i n c e Wood and Groves d i d t h e i r work, so Whittemore's numbers may be more a p p r o p r i a t e . An i n t e r e s t i n g comparison between g e n e t i c type and the growth of p r o t e i n , l i p i d , ash and water was p u b l i s h e d by Tess et a l . i n 1986. F i g u r e s 6, 7 and 8 o u t l i n e a comparison between d i s s e c t e d growth of the three g e n e t i c s t r a i n s and growth f o r PIG GROWTH MODEL page 44 a f a s t growing p i g as estimated by the model d e s c r i b e d i n t h i s t h e s i s . F i g u r e 6 compares a l o g f u n c t i o n d e s c r i b i n g body composition of a h i g h - f a t g e n e t i c s t r a i n (Tess et a l . , 1986) with a body composition of modelled commericial p i g s (as d e s c r i b e d by the model developed i n t h i s t h e s i s ) . The f a t content of the h i g h - f a t s t r a i n was more than double the model-predicted f a t content of the commercial p i g s ( t h e s i s model) at a market weight of 100 kgs. The low f a t g e n e t i c s t r a i n (see Fi g u r e 7) a l s o produced a high e r f a t content at market weight (100 kgs) than the t h e s i s model p r e d i c t i o n . The Hampshire * Large White commercial s t r a i n shown i n f i g u r e 8 compared f a v o u r a b l y to t h e s i s model p r e d i c t i o n s . The weaner composition of the Hampshire * Large White commercial s t r a i n demonstrated i n Fi g u r e 8 could be entered d i r e c t l y as a p r e d i c t i o n of weaner body composition when model l i n g . The equation r e p r e s e n t i n g body p r o t e i n of a weaner p r e f e r r e d by Wood and Groves (1965) i s as f o l l o w s : body p r o t e i n (kg) = (0.154 B.W.) - 0.212. Whittemore's (1983) p r e f e r r e d equation f o r body p r o t e i n of a weaner of 0.16 B.W. does not s i g n i f i c a n t l y d i f f e r from the Wood and Groves (1965) equation which has been used i n the model i n the t h e s i s . p a g e 4^-5 Figure 6 COMPARISONS BETWEEN TESS et al.(1986) LOGARITHMIC REPRESENTATION OF BODY PROTEIN (PT), LIPID (LT). ASH (AT), WATER (YT) AND EMPTY BODY WEIGHT (WE) AND THESIS MODEL PREDICTIONS (MOD represents the thesis model and Tess represents the Tess et al.(1986) model). BELTSVILLE HIGH FAT GENETIC STRAINS AGE DAYS MOD WE Tess WE MOD PT Tess PT MOD LT Tess LT MOD AT Tess AT MOD YT Tess YT 49 17.0 16.3 2.8 2.5 2.0 3.2 0 5 0.5 11.6 10.1 56 20.7 3.1 3.2 4.8 0.7 o.e 12.1 63 27.3 25.4 4.4 3.7 4.5 6.9 1.0 0.8 17.4 14.1 70 32.9 30.6 5.3 4.3 5 9 9.4 1.2 0.9 20.5 16.1 77 38.8 36.1 6.3 4.9 7.4 12.3 !ii;5:;; 1.0 23.6 18.0 84 40.4 7.0 5.3 8.5 14.6 1.6 1.1 26.0 19.4 91 45.8 8.0 5.8 9.8 17.7 1.2 28.9 21.1 98 54.1 51.7 8.9 6.3 11.3 21.2 2.0 1.3 31.9 22.8 105 59.9 57.S 10 0 6.9 12.8 25.1 2.2 1.5 :|;34:;9:i: 24.5 112 65.9 64.5 11.0 7.4 14.4 29.3 2.5 1.6 i38:j|;i 26.2 119 71.9 71.3 WW£ 7.9 16.0 33.9 2.7 1.7 41.2 27.8 126 77.9 78.2 13.1 8.4 17.6 38.6 i:ii!!i;2^9;;; 1.8 29.4 133 83.7 85.2 14.2 8.9 19.2 43.5 1.9 47.2 30.9 3.2 140 89.4 92.3 15.2 9.4 20.7 48.5 3.4 2.0 50 2 32.4 147 95.0 99.4 16.2 9.9 22.2 53.5 2.1 33.8 154 100.5 106.4 17.2 10.3 23.7 58.7 3.9 2.2 35.1 161 105.8 113.4 18 1 10.8 25.1 63.9 wmm 2.3 36.4 168 110.9' 120.3 11.2 69.0 2.4 '61.0 37.7 175 115.8 127.1 20.0 11.6 27.9 74.1 4.6 2.5 63.4 38.8 182 120 6 133.7 20.9 12.0 29.2 79.2 4.8 2.6 65 8 39.9 189 125.2 140.2 12.3 30.4 84.2 5.1 2.7 68.0 41.0 196 129.6 146.6 22.5 12.7 31.7 89.2 5.3 2.8 42.0 203 133.8 152.7 23.3 13.0 32.8 94.0 5.5 2.8 43.0 210 137.8 158.7 24.0 13.3 33.9 98.7 b./ 2.9 74.2 43.9 217 141.7 164.5 24.71 13.6 35.0 103.2 6.0 3.0 76.0 44.7 224 145.3 170.1 25.4 13.9 36.0 107.6 6.2 3.1 45.5 Tess et al. equations are represented above as Tess PT.LT,AT,YT. Tess PT (protein) = 0.266*BW~0.794 WE = PT + LT + AT + YT Tess LT (lipid) = 0.03*BW~1.644 Tess AT (ash) = 0.048*BW~0.834 Tess YT (water) = 1.388*BW~0.701 p a g e 46 Figure 7 COMPARISONS BETWEEN TESS et al.(1986) LOGARITHMIC REPRESENTATION OF BODY PROTEIN (PT), LIPID (LT), ASH (AT), WATER (YT) AND EMPTY BODY WEIGHT (WE) AND THESIS MODEL PREDICTIONS (MOD represents the thesis model and Tess represents the Tess et al.(1986) model). BELTSVILLE LOW FAT GENETIC STRAINS AGE MOD Tess MOD Tess MOD Tess MOD Tess MOD Tess DAYS WE WE l l i i l l PT l l i i l l LT AT AT YT YT 49 17,0 16.5 2.6 lllii 1.9 0.5 0.6 llflll 11.5 56 /:22.p:r 21.1 wwmm 3.4 WWM 2.9 0.7 0.7 14.2 63 ;.;'27'3:!: 26.1 WWmm 4.2 i l l p i i l 4.1 1.0 0.9 wwm 17.0 70 32.9 31.4 wwmm 5.0 WWsiM 5.6 HiHiiiiii! 1.1 20,5 19.8 77 38 8 37.0 wwmm 5.8 wwmm 7.3 i i i i i i i 1.3 lliiil 22.6 84 43.1 41.2 mwmm 6.5 l l s i l 8.7 WWWm 1.4 :26.Q: 24.6 91 48.5 46.5 wwmm 7.2 filial 10.6 1.8 1.6 llsil 27.1 98 54.1 52.2 8.9 8.1 Wmm 12.7 : \ -2:0 1.7 WWM 29.7 105 59.9 58.2 10,0 8.9 12.8 15.1 2.2 1.9 34.9 32.3 112 65.9 64.4 11.0 9.8 14.4 17.6 2.5 2.1 38.1 34.9 119 71 9 70.8 12 1 10.6 16.0 20.4 mmm 2.3 l l i i l l 37.5 126 77.9 77.2 WMM 11.5 liliil 23.2 2.9 2.5 i§£il 40.1 133 83 7 83.6 wmm 12.3 WMM 26.2 wmm 2.6 :-.47j2-=: 42.5 140 89.4 90.0 "-15:2: 13.1 20.7 29.2 : 3.4: 2.8 50.2 44.9 147 95,0 96.4 wrn^i 13.9 Hill 32.3 :3,6 3.0 llpll 47.2 154 100 5 102.7 WMM 14.7 23.7 35.5 : 3.9 3.1 Hill 49.4 161 105 8 108.9 18.1 15.4 liilif 38.6 WMM 3.3 58 4 51.5 168 110.9 114.9 wmw% 16.1 26.5 41.8 wmm 3.4 61.0 53.6 175 115.8 120.8 lllg&l 16.8 27.9 44.9 wmm 3.6 63 4 55.5 182 120 6 126.6 20.9 17.5 29.2 48.0 4.8 3.7 65.8 57.4 189 125 2 132.3 w®WM 18.1 30.4 51.1 l i i i i i 3.9 68.0 59.2 196 129.6 137.7 wwM 18.8 l i i i l 54.1 : :5.3 4.0 wmm 60.9 203 133,8 143.0 19.4 32.8 57.0 wwm 4.1 WWM 62.5 210 137.8 148.1 24.0 19.9 33.9 59.9 wwm 4.2 wwmw 64.0 217 141.7 153.0 20.4 35.0 62.7 6.0 4.4 76,0 65.5 224 145.3 157.7 25.4 21.0 36.0 65.4 4.5 l l i i : 66.9 ===== ==== = ===== = = = = ===== = = = = Tess et al. equations are represented above as Tess PT,LT,AT,YT,WE Tess PT (protein) = 0.17*BW~0.967 WE = PT + LT + AT + YT Tess LT (lipid) = 0.17*BW~1.658 Tess AT (ash) = 0.038*BW~0.957 Tess YT (water) = 1.122*BW*0.821 page k7 Figure 8 COMPARISONS BETWEEN TESS et al.(1986) LOGARITHMIC REPRESENTATION OF BODY PROTEIN (PT), LIPID (LT), ASH (AT), WATER (YT) AND EMPTY BODY WEIGHT (WE) AND THESIS MODEL PREDICTIONS (MOD represents the thesis model and Tess represents the Tess et al.(1986) model). HAMPSHIRE*LARGE WHITE COMMERCIAL STRAIN AGE MOD Tess MOD Tess MOD Tess MOD Tess MOD Tess DAYS III!!! WE PT PT l l t t l i LT AT AT Iiiiiiii YT 49 mmM 16.6 l i i i i 2.7 WWMM 1.6 iiiiiiii&lii 0.6 iiiii&iii 11.8 56 fiiiiii 21.2 3.5 wwWM 2.4 0.7 tiiiiii 14.7 63 i i i i i i i i 26.2 iiiiiiii4l4l 4.3 wwmii 3.4 0.8 i i i i i i i i 17.6 70 32.9 31.4 WWWi 5.1 mwm 4.6 iiiiiiiiil2l 1.0 20.5 20.7 77 : 38;8v 36.9 wmm 6.0 iiiiiiiiliii 6.0 iiliiiiiiiii 1.1 iiiii&iii 23.7 84 l l l l i 41.0 wmm 6.6 iiiiiffli 7.2 i i i i i i i i 1.3 l i i i i 26.0 91 46.1 iiiiiiii 7.4 fwMM 8.7 iiiiiiiii 1.4 WWM 28.7 98 54 J 51.6 ;•>;:: :8V9l 8.2 WMM 10.4 W$2M 1.5 31.9 31.5 105 :i:69.9 57.3 10,0 9.1 12.8: 12.2 WMm 1.7 i l s i i i 34.4 112 l i i i i 63.2 11.0 9.9 iKiMmMiu 14.3 2.5 1.8 I l i S ! 37.2 119 l i i l l l 69.3 12.1 10.8 wmM 16.4 2,7 2.0 liiiiii 40.1 126 75 . a W*z*W 11.6 WMMM ia.7 iiiiiiiiiai&iii 2.1 WMWWi 42.Q 133 83.7 81.3 12.5 19.2 21.0 i l i l l i i i 2.2 47.2 45.6 140 89.4 87.3 13.3 ;:20^ 7:;; 23.4 iiilliiil 2.4 50.2 48.2 147 93.2 14.1 iiiiiiii! 25.8 2.5 53.0 50.8 154 100.5 99.0 wmM 14.9 .ii: 23:71-. 28.3 WWM 2.6 55.7 53.3 161 105,8 104.7 I i i i i i i i 15.6 30.7 WWMW 2.7 58.4 55.6 168 110.9 110.3 iHiiiii 16.4 ; 26.5, 33.2 liiiiiiiii 2.9 iliioli 57.9 175 115.8 115.7 20.0 17.0 :;:?7;9;; 35.6 wwMm 3.0 63.4 60.1 182 120.6 121.0 20.9 17.7 l i i i i 38.0 3.1 65.8 62.2 189 Will: 126.1 i p i l l | i 18.4 40.4 i i i i l l i i i 3.2 68.0 64.2 196 129.6 131.1 22.5 19.0 42.7 iniiiiii 3.3 70.2 66.1 203 135.8 wmm 19.6 32,8 45.0 3.4 72 2 67.9 210 137.8 140.4 wmm 20.1 33.9 47.2 iiiiiiiiiii 3.4 liilili 69.6 217 I l l i 144.8 WWM 20.7 135:0 49.4 i i i i i i i i 3.5 i i i i i i i i 71.3 224 145 3 149.1 25.4 21.2 36.0 51.4 l l i i i i i 3.6 iiiiiiii 72.8 Tess et al. equations are represented above as Tess PT, LT, AT, YT, WE Tess PT (protein) = 0.178*BW"0.96 WE = PT + LT + AT + YT Tess LT (lipid) = 0.016*BW~0.622 Tess AT (ash) = 0.047*BW~0.872 Tess YT (water) = 1.068*BW~0.848 PIG GROWTH MODEL page 48 I n i t i a l p r e d i c t i o n of body f a t content equation: Body f a t (kg) = (0.192 B.W.) - 0.288 Thi s equation i s p r e f e r r e d by Wood and Groves (1965) but the high f a t content probably does not hold f o r the improved g e n e t i c m a t e r i a l now common i n Western Canada. The value p r e f e r r e d by Whittemore (1983) i s 0.07 - 0.15 B.W. as d e f i n e d e a r l i e r . T h i s p r e d i c t s a body f a t content of a 20 kg p i g of between 1.4 and 3.0 kgs. The equation of Wood and Groves (1965) p r o v i d e s a f a t content of 3.55 kgs which i s higher than Whittemore's estimate. The d i f f e r e n c e probably r e p r e s e n t s the changes i n g e n e t i c m a t e r i a l which have taken p l a c e s i n c e 1965, but, the Canadian nature of Wood and Groves work has i t c u r r e n t l y i n c l u d e d i n the model as a f i r s t approximation, although any a l t e r n a t i v e equation c o u l d be chosen by the modeller. I t i s a l s o p o s s i b l e to ent e r an a c t u a l amount of f a t r a t h e r than an equation l i n k i n g f a t to another parameter. PIG GROWTH MODEL page 49 I n i t i a l body ash equation: I n i t i a l body ash (kg) = (0.032 B.W.) - 0.073 Th i s equation f o r ash content does not d i f f e r s u b s t a n t i a l l y between r e s e a r c h e r s so the Wood and Groves (1965) equation was used. I n i t i a l empty body weight equation: I n i t i a l empty body weight (kg) = 0.952 B.W. The equation of Wood and Groves (1965) f o r empty body weight was chosen, as a comparison with the work of Tess et a l . (1986) f o r commercial p i g s would suggest t h a t the equation i s s t i l l v a l i d . I n i t i a l body energy content equation: I n i t i a l body energy (kcal) = (5640 (body p r o t e i n ) ) + (9400 (body f a t ) ) The energy content of the body was estimated a c c o r d i n g to an equation provided by Ewan (personal communication) and was i n c l u d e d only f o r i n t e r e s t at t h i s time. PIG GROWTH MODEL page 50 (3) PROTEIN SECTION T o t a l i d e a l d i e t a r y p r o t e i n equation: T o t a l i d e a l p r o t e i n (kgs) = (true d i g e s t i b i l i t y [ c o r r e c t e d f o r metabolic f e c a l l o s s ] ) ( d i e t a r y crude p r o t e i n c o n c e n t r a t i o n ) (B.V.) (feed intake (kg)) The t o t a l i d e a l p r o t e i n i n g e s t e d by the model p i g per day i s needed f o r f u t u r e c a l c u l a t i o n s and i s represented by the above equation. The d i g e s t i b i l i t y of the feed i n g e s t e d i s estimated to be approximately 85% (0.85), depending on the feed i n g r e d i e n t s . The p r o t e i n d i g e s t i b i l i t y can be c a l c u l a t e d from p u b l i s h e d values of i t s component i n g r e d i e n t s w i t h i n a l i n e a r programming system. The crude p r o t e i n of the feed i n g e s t e d i s expressed as grams of p r o t e i n per kg of feed i n t a k e . The term b i o l o g i c a l value was d e f i n e d e a r l i e r and can a l s o be d e r i v e d by a l i n e a r programming system. NRC (1988) amino a c i d requirements: The r e l a t i o n s h i p s are: Lys i n e i n t a k e , grams/day = 2.128 B.W.A0.50 Tryptophan i n t a k e , grams/day = 0.288 B.W."0.55 Threonine i n t a k e , grams/day = 1.153 B.W."0.55 PIG GROWTH MODEL page 51 P r o t e i n i n t a k e , grams/day = 33.0 B.W.A0.58 The requirements f o r l y s i n e , tryptophan, threonine (the three most commonly l i m i t i n g amino a c i d s ) and p r o t e i n were taken from the NRC (1988) values and were expressed as a f u n c t i o n of body weight (R.C. Ewan, p e r s o n a l communication). From the above, the l y s i n e l e v e l r e q u i r e d i n the feed ( i n percent) can be c a l c u l a t e d from the l y s i n e i n t a k e necessary per day (g/day) by simply d i v i d i n g the amino a c i d i n take needed by the feed a c t u a l l y eaten. T o t a l p r o t e i n mass equation [ P t ] : Pt = (0.16 B.W.) An e s t i m a t i o n of the t o t a l p r o t e i n mass i n the body (Pt) can be d e r i v e d from the Gompertz equation used to estimate body weight. The equation used was d e s c r i b e d by Whittemore (1987) but d i f f e r s from t h a t given i n h i s e a r l i e r work (Whittemore, 1976). Whittemore's e a r l i e r work d e s c r i b e d a Pt of 0.15 B.W. at 20 kgs de c r e a s i n g to 0.14 B.W. at 100 kgs body weight. In g e n e r a l , Pt i s accumulated i n the model and i s u s u a l l y s e l f generated, c r e a t i n g an unavoidable c i r c u l a r type e r r o r . PIG GROWTH MODEL page 52 Mature t o t a l p r o t e i n mass estimate [ P t A ] : P t A = 35 kg An e s t i m a t i o n of the mature t o t a l p r o t e i n mass i s used i n l a t e r c a l c u l a t i o n s . Whittemore (1987) commented on how d i f f i c u l t i t was to q u a n t i f y Pt", as few experiments take p i g s through to t h e i r mature body s i z e f o r an e s t i m a t i o n of p r o t e i n mass, but he suggested values between 30 kgs and 40 kgs. Whittemore (1976) used 35 kg as h i s estimate f o r mature body p r o t e i n ; consequently t h i s value was accepted f o r m o d e l l i n g purposes. P r o t e i n r e t e n t i o n equation [ P r ] ( k g ) : Pr = ((IPt)/1000)-(0.004 ( d i g e s t i b l e crude p r o t e i n ) ) (0.9) An e s t i m a t i o n of p r o t e i n r e t a i n e d (Pr) can be d e r i v e d from the d i f f e r e n c e between the t o t a l i d e a l p r o t e i n intake and the i d e a l p r o t e i n used f o r maintenance. In the l i t e r a t u r e review, the concept of i d e a l p r o t e i n and the equation IPt = IPm + IPr were d i s c u s s e d . T h i s equation was manipulated to y i e l d IPr = IPt - IPm = Pr which d e r i v e s the p r o t e i n r e t a i n e d f o r growth. An equation i s used to c a l c u l a t e the t o t a l i d e a l p r o t e i n intake of the growing p i g . The second h a l f of the p r o t e i n r e t e n t i o n equation i s the d e r i v a t i o n of the i d e a l p r o t e i n r e q u i r e d f o r PIG GROWTH MODEL page 53 maintenance. Carr et a l . (1977) developed values f o r the p r o t e i n requirement f o r maintenance from n i t r o g e n r e t e n t i o n s t u d i e s u s i n g the i n t e r c e p t s of the n i t r o g e n intake a x i s ( n i t r o g e n r e t e n t i o n = 0) as the b a s i s . Whittemore (1983) i n t e r p o l a t e d the n i t r o g e n data to an i d e a l p r o t e i n of maintenance equation as f o l l o w s ; IPm (kgs) = 0.94 B.W."0.75. In an e a r l i e r p u b l i c a t i o n , Whittemore et a l . (1976) had proposed a higher estimate d e r i v e d from assumptions concerning p r o t e i n turnover at maintenance y i e l d i n g the f o l l o w i n g ; IPm (kgs) = 0.0040 Pt. A n a l y s i s of the c u r r e n t model and pr o d u c t i o n data from western Canada suggested t h a t the higher value proposed by Whittemore et a l . (1976) should be used. The ARC (1981), i n t h e i r review of p r o t e i n and amino a c i d requirements, suggested t h a t a c o e f f i c i e n t should be added to the equation above to represent m a t e r i a l i n e f f i c i e n c y . The ARC d e r i v e d an equation to d e s c r i b e t h i s i n e f f i c i e n c y when lower l e v e l s of intake are used; a2 = 1.02 (exp (-0.039 (feed i n t a k e ) ) ) . I t i s estimated t h a t the i n e f f i c i e n c y l i e s between 0.85 and 1. The value 0.9 was chosen as a s t a r t i n g value but a b e t t e r estimate might be d e r i v e d i n the fu t u r e through a study r e b u i l d i n g the ARC (1981) equations. PIG GROWTH MODEL page 54 Maximum p r o t e i n d e p o s i t i o n equation [ P r A ] : IF statement : Pr < P r A then use Pr, other wise use P r A The p r o t e i n a v a i l a b l e f o r r e t e n t i o n (where energy i s not l i m i t i n g ) w i l l be u t i l i z e d up to the p o i n t of maximum p r o t e i n d e p o s i t i o n , which i s dependent upon the g e n e t i c composition and sex of the animal. The growth models of Whittemore et a l . (1976), Whittemore (1983), Moughan (1987) and Black et a l . (1986), a l l use values f o r maximum p r o t e i n d e p o s i t i o n per day. The maximum p r o t e i n d e p o s i t i o n i s represented by the symbol P r A . The Black et a l . (1986) p r o t e i n d e p o s i t i o n model i s used i n the present growth model. Body p r o t e i n t u rnover equation [PRTPX] (R.C. Ewan, pe r s o n a l communication) -. PRTPX = (0.23 ( ( P t A ) - (Pt) )') / ( P t A ) The d a i l y r a t e of body p r o t e i n turnover i s an important p a r t of any equation d e r i v i n g the energy c o s t of p r o t e i n r e t e n t i o n . Whittemore (1987) assumed t h a t p r o t e i n turnover i s some f u n c t i o n of the degree of maturi t y . Ewan (personal communication) d e r i v e d an equation he c a l l e d PRTPX which r e l a t e s p r o t e i n r e t e n t i o n to p r o t e i n s y n t h e s i s . The equation PRTPX = (0.23 ( P t A - P t ) / P t A ) can then be used to estimate p r o t e i n turned over during the day (Px) as f o l l o w s : PIG GROWTH MODEL page 55 Px = P r / ( 0 . 2 3 ( P t A - P t ) / P t A ) as d e f i n e d by Whittemore (1987 ) . Equation f o r the second method of d e s c r i b i n g maximum p r o t e i n r e t e n t i o n [ P r A I I ] (R.C. Ewan, p e r s o n a l communication): P r A I I = [ ( p r o t e i n i n t a k e ) ( d i g e s t i b i l i t y ) ( B i o l o g i c a l v a l u e ) ] /[0.94+(0.06/(PRTPX))]/1000 Ewan ( p e r s o n a l communication) d e r i v e d a second method of e s t i m a t i n g p r o t e i n r e t e n t i o n which can be compared t o the method used e a r l i e r . Ewan's e q u a t i o n was as f o l l o w s ; P r = [ ( P I ) (V) (D)]/[0.94 + (0.06/PRTPX)] where PI = p r o t e i n i n t a k e , V = b i o l o g i c a l v a l u e of the feed as e s t i m a t e d by the model, D = d i g e s t i b i l i t y of the f e e d s t u f f , PRTPX = a v a l u e d e r i v e d e a r l i e r . T h i s e q u a t i o n i s o n l y i n c l u d e d so t h a t i t s p r e d i c t e d e s t i m a t e d maximum p r o t e i n d e p o s i t i o n can be compared t o o t h e r models of p r o t e i n d e p o s i t i o n . Equation f o r minimum p r o t e i n turnover [Px(min)]: Px(min) = (0.05 Pt) Whittemore (1987) d e r i v e d a min i m a l v a l u e f o r p r o t e i n t u r n o v e r r e p r e s e n t e d as Px(min) = 0.05 P t which i s i n c o r p o r a t e d i n t o the model t o a s s u r e t h a t p r o t e i n t u r n o v e r i s never l e s s than t h i s v a l u e . PIG GROWTH MODEL page 56 E q u a t i o n d e s c r i b i n g p r o t e i n r e t e n t i o n as a f u n c t i o n of p r o t e i n t u r n o v e r : Px = ( P r A ) / ( P r t P x ) The t o t a l mass of p r o t e i n turned over i n the day (Px) was d e f i n e d as Px = P r A / ( 0 . 2 3 ( P T A - P t ) / P t ) by Whittemore (1987). I t remains c o n t e n t i o u s as to whether Px i s a l s o r e l a t e d i n some p r o p o r t i o n a l way to Pr such t h a t higher d a i l y r a t e s of p r o t e i n r e t e n t i o n are a s s o c i a t e d with higher d a i l y r a t e s of p r o t e i n turnover. (4) ENERGY SECTION Energy of maintenance equation [Em](MJ/day): Em = 0.719 (B.W.A0.63) "Me t a b o l i z a b l e energy i s e i t h e r r e t a i n e d i n p r o t e i n or f a t t y t i s s u e s , used f o r the work of c r e a t i n g these t i s s u e s (and bone), or used f o r the work of maintenance (Em) and c o l d thermogenesis (Whittemore, 1987)." The energy r e q u i r e d f o r maintenance i s l i k e l y a s s o c i a t e d with the turnover of p r o t e i n t i s s u e s , so Whittemore p r e f e r s the equation developed from the work of Stant et a l . (1968): Em (MJ/day) = 1.85 Pt A0.78 The equation used i n the model i s the equation developed by the ARC working party; PIG GROWTH MODEL page 57 Em (MJ/day) = 0.719 B.W.A0.63 which i s c a l c u l a t e d from body weight (ARC, 1981). The energy of maintenance c a l c u l a t i o n should be changed to Whittemore's c a l c u l a t i o n when an acceptable t o t a l body p r o t e i n (Pt) i s obtained f o r p i g s i n western Canada because of the r o l e t h a t body p r o t e i n p l a y s i n maintenance energy requirements. The value f o r t o t a l mass of p r o t e i n turned over i n one day (Px) was c a l c u l a t e d e a r l i e r , and t h i s value was then i n c o r p o r a t e d i n t o Whittemore's (1987) equation f o r the energy c o s t bf p r o t e i n r e t e n t i o n , as o u t l i n e d below. Equation for the energy cost of protein retention [Epr] (MJ/day): Epr - (5 (Px))+(23 (Px)) The energy c o s t of p r o t e i n r e t e n t i o n (Epr) has been d i s c u s s e d i n the l i t e r a t u r e review. Whittemore's (1987) equation f o r Epr i s as f o l l o w s : Epr = 5 Px + 23 Pr where Px and Pr were c a l c u l a t e d e a r l i e r . Equation for the amount of l i p i d retained per day [Lr](Kg): L r = [ MEt - ( Em + EPr + EHl)]/53.5 The c a l c u l a t i o n of the amount of l i p i d r e t a i n e d per day (Lr) r e q u i r e s a s e r i e s of equations which are u t i l i z e d i n many of the equations which f o l l o w . L r i s a c t u a l l y d e r i v e d by d i f f e r e n c e based on an assumed p r i o r i t y f o r energy PIG GROWTH MODEL page 58 u t i l i z a t i o n i n the body. MEt i s a v a r i a b l e c a l c u l a t e d l a t e r i n the model and r e p r e s e n t s the energy a v a i l a b l e f o r work and f o r energy storage i n t i s s u e s but excludes energy l o s t i n u r i n e or used f o r deamination. The equations used i n t h i s p a r t of the energy s e c t i o n are mainly d e r i v e d from two of Whittemore's (1983, 1987) papers. The energy s e c t i o n s of these two papers d i f f e r i n methods of c a l c u l a t i o n . Where p o s s i b l e , a comparison of the two methods i s shown. The d e r i v a t i o n of L r , as mentioned e a r l i e r , i s based on an assumed p r i o r i t y as f o l l o w s ; Em, EH1, Epr, ELr where; Em r e p r e s e n t s the energy used dur i n g the work of maintenance (MJ/day), EH1 r e p r e s e n t s the energy c o s t of c o l d thermogenesis (MJ/day), Epr r e p r e s e n t s the energy cost of p r o t e i n r e t e n t i o n (MJ/kg), and ELr r e p r e s e n t s the energy c o s t of f a t growth (MJ/kg). T h e r e f o r e , MEt = Em + EH1 + EPr + ELr which has a l r e a d y been ad j u s t e d f o r deamination l o s s e s , can be r e w r i t t e n as L r (kg) = [MEt - (Em + EPr + EHl)]/53.5. ELr/53.5 = L r because 53.5 i s the energy r e q u i r e d to d e p o s i t f a t (kg) PIG GROWTH MODEL page 59 where ELr = 14Lr + 39Lr = 53Lr. T h i s equation i s d e r i v e d from the assumption t h a t i t r e q u i r e s 14 MJ of energy to form 1 kg of f a t , with f a t having an energy value of 39 MJ. The assumption of the equation d e f i n e d e a r l i e r i s t h a t normal growth may proceed i n the form of p r o t e i n - c o n t a i n i n g t i s s u e s only, as p r o t e i n i s the n u t r i e n t which d r i v e s a l l the equations contained i n the L r equation. During n u t r i e n t - l i m i t e d growth (growth before Pr = P r A ) , there i s always some f a t l a i d down i n the course of p h y s i o l o g i c a l l y normal gains. To overcome t h i s flaw i n the l i p i d equation, a minimum l e v e l of f a t t h a t may be expected to be de p o s i t e d per day i n r e l a t i o n to p r o t e i n d e p o s i t e d , must be i n s e r t e d by the modeller. Whittemore (1987) suggested minimum values of f a t to gain which are presented i n Table 6. Table 6. Values f o r the minimum r a t i o of f a t gain to p r o t e i n gain (Lr to Pr) i n White b r e e d s 5 and s t r a i n s of p i g s used f o r the p r o d u c t i o n of meat, (kg l i p i d : kg p r o t e i n ) E n t i r e males Females C a s t r a t e s Grandparent breeding stock 0.4 Improved h y b r i d s 0.5 Commercial c r o s s e s 0.7 U t i l i t y s t r a i n s 0.9 0. 6 0.7 0. 9 1. 1 0. 8 1. 0 1. 2 PIG GROWTH MODEL page 60 To accommodate a minimal l e v e l of f a t being d e p o s i t e d dur i n g n u t r i e n t l i m i t e d growth, a l o g i c a l argument d e f i n i n g a minimum l e v e l of f a t to p r o t e i n must be i n c l u d e d . The 1 IF' statement l o g i c i s as f o l l o w s ; i f the value L r i s l e s s than the value P r A ( p r o t e i n deposited) times the minimum l e v e l of f a t to p r o t e i n , then the value L r i s used, otherwise the value L r times the minimum f a t to p r o t e i n i s used. Equations d e s c r i b i n g t o t a l energy a v a i l a b l e f o r work and energy storage [MEt]: A value f o r MEt has been d e f i n e d by two d i f f e r e n t methods which w i l l be o u t l i n e d below. As d e s c r i b e d e a r l i e r , MEt (which has a l r e a d y been adj u s t e d f o r deamination l o s s e s ) , i s p a r t i t i o n e d i n t o maintenance, p r o t e i n r e t e n t i o n , f a t r e t e n t i o n , and c o l d thermogenesis. Whittemore (1983) d e f i n e d a d i f f e r e n c e between c l a s s i c a l ME and h i s MEt (which more approximates an Net Energy (NE) system) which should be b e t t e r understood to f o l l o w h i s d e r i v a t i o n . Whittemore's d e f i n i t i o n of ME i s the d i f f e r e n c e between energy d i g e s t e d and energy excreted i n the u r i n e . T h i s assumes t h a t there i s no l o s s of energy as gaseous l o s s e s and f a i l s to take i n t o account the energy expended i n urea s y n t h e s i s , which Whittemore (1983) suggests i s about 5 MJ per kg p r o t e i n deaminated. The amount of PIG GROWTH MODEL page 61 energy y i e l d e d from 1 gram of d i e t p r o t e i n i s l e s s than the amount of energy y i e l d e d from 1 gram of d i e t carbohydrate ( i f the energy i s not used f o r p r o t e i n d e p o s i t i o n ) . T h i s means t h a t the g r e a t e r the amount of p r o t e i n deaminated, the lower the y i e l d of ME from DE. The e f f e c t i v e ME or MEt i s t h e r e f o r e d e r i v e d from the intake of a p p a r e n t l y d i g e s t e d d i e t energy (DE) by the f o l l o w i n g equations (Whittemore, 1983); EPf = DE - (23 DCP) where EPf i s p r o t e i n - f r e e d i g e s t i b l e energy, and DCP i s the d i e t a r y a p p a r e n t l y d i g e s t i b l e crude p r o t e i n with an assumed energy content of 23 MJ/kg. T h i s assumes t h a t a l l n i t r o g e n present i s amino-nitrogen which Whittemore (1983) suggested was an over estimate. More recent models (Moughan and Verstegen, 1988) have continued with the concept of accounting f o r energy i n t a k e as p r o t e i n - f r e e energy intake so t h a t the energy a v a i l a b l e from p r o t e i n can be c a l c u l a t e d by d i f f e r e n c e from d i g e s t i b l e crude p r o t e i n and p r o t e i n r e t a i n e d , as shown below. A measure of p r o t e i n deaminated (Pm) i s made by the d i f f e r e n c e between DCP and p r o t e i n r e t a i n e d ( P r ) . Then a measure of the energy from p r o t e i n deaminated (Qd) i s made from the f o l l o w i n g equation: Qd = 23 Pm - [(7 Pm) + (5 Pm)] PIG GROWTH MODEL page 62 The numbers i n the Qd equation r e l a t e to the f o l l o w i n g ; 23 (MJ/kg) i s the gross energy content of p r o t e i n , 7 i s the energy contained i n u r i n e per kg of p r o t e i n deaminated, and 5 i s the work energy expended i n urea s y n t h e s i s . MEt can then be c a l c u l a t e d (Whittemore, 1983) as; MEt = Qd + 23 Pr + EPf which i s the f i r s t method of c a l c u l a t i n g MEt d e f i n e d e a r l i e r . E q uation f o r p r o t e i n deaminated [Pm](Kgs): Pm = ( ( d i g e s t i b l e crude p r o t e i n ) - ((Pr~)/1000)) As suggested e a r l i e r , Pm ( p r o t e i n deaminated) i s c a l c u l a t e d by s u b t r a c t i n g the p r o t e i n r e t a i n e d from the d i g e s t i b l e crude p r o t e i n . Equation f o r energy from p r o t e i n deaminated [Qd](Kgs): Qd = (23 Pm) - [(7 Pm) + (5 Pm)] The energy from p r o t e i n deamination (Qd) i s c a l c u l a t e d by the d i f f e r e n c e between the gross energy content of p r o t e i n and the sum of the energy expended f o r urea s y n t h e s i s and the energy i n the u r i n e . PIG GROWTH MODEL page 63 Equation f o r p r o t e i n - f r e e d i g e s t i b l e energy [Epf](MJ/Kg): Epf = [(D.M.) (D.E.) (feed i n t a k e ) ] - [(23 D.C.P.) + (0.05 ((D.M.) (D.E.) (feed i n t a k e ) ) ) ] [where D.M. i s dry matter and D.E. i s d i g e s t i b l e energy] A measure of the p r o t e i n - f r e e d i g e s t i b l e energy (EPf) can be c a l c u l a t e d as f o l l o w s (Whittemore, 1987); EPf = D.E.I. - [(23 D.C.P.) + (0.05 D.E.)] where D.E.I, i s the d i g e s t i b l e energy i n t a k e . Equation f o r e f f e c t i v e m e t a b o l i z a b l e energy [MEt](MJ): MEt = (Qd) + (23 P r A ) + (Epf) A measure of the e f f e c t i v e m e t a b o l i z a b l e energy (MEt) i s c a l c u l a t e d as; MEt = Qd + 23 Pr + EPf T h i s value f o r m e t a b o l i z a b l e energy does not make any allowances f o r energy l o s s as gaseous escapes, but these l o s s e s are assumed to be near zero with c o n v e n t i o n a l p i g feeds and only become s i g n i f i c a n t when d i e t s with very high f i b r e l e v e l s are fed. Equation f o r e f f e c t i v e m e t a b o l i z a b l e energy (choice 2)[MEt](MJ): MEt(II) = (Em) + (Epr) + (53.5 Lr) + (EH1) A second method f o r d e r i v i n g m e t a b o l i z a b l e energy a v a i l a b l e to the energy system i s to add up parameters r e p r e s e n t i n g the energy of maintenance, p r o t e i n r e t e n t i o n , PIG GROWTH MODEL page 64 f a t r e t e n t i o n , and c o l d thermogenesis. The f i r s t three parameters have been d e f i n e d but the energy used f o r c o l d thermogenesis w i l l not be d e r i v e d u n t i l l a t e r . The two methods f o r d e f i n i n g MEt should have s i m i l a r sums and these equations are compared f o r any d i s c r e p a n c y . Equation f o r heat l o s s (Close et a l . , 1978a) [H] (KJ/Kg A 0 .75): H = 979.8 - [50.33 (temp)] + [0.9187 (temp A2)] + [0.1366 ( ( ( f e e d intake) (14020))/(B.W. A0.75))] + [0.0077 ( ( ( f e e d intake) (14020))/(B.W. A0.75))] [temp] Feeding l e v e l and environmental temperature have a s i g n i f i c a n t e f f e c t on the rate of heat l o s s from the growing p i g (Close et a l . , 1978a). The lower c r i t i c a l temperature, d e f i n e d as the temperature at the lower end of the zone of t h e r m o n e u t r a l i t y , i s of p a r t i c u l a r i n t e r e s t as i t i s the lowest environmental temperature at which the animal's heat l o s s i s minimal and consequently at which energy r e t e n t i o n f o r p r o d u c t i o n i s maximal. An upper c r i t i c a l temperature a l s o e x i s t s but i t i s not being c o n s i d e r e d at the c u r r e n t time, but would become important i f pigs were housed i n hot c l i m a t e s . The energy c o s t of c o l d thermogenesis (EH1) m o d i f i e s the energy of maintenance (Em) when the ambient temperature (T) i s lower than the lower c r i t i c a l temperature (Tc) (Whittemore, 1983). Tc i s dependent on the weight and feed PIG GROWTH MODEL page 65 in t a k e of the p i g which i n turn i n f l u e n c e s the g e n e r a l l e v e l of heat output (H). The equations which f o l l o w are designed to e s t a b l i s h the energy c o s t of c o l d thermogenesis (EH1). Close et a l . ' s (1978a) H i s used to e s t a b l i s h a general l e v e l of heat output (H) used i n the c a l c u l a t i o n of EH1. The equation i s d e r i v e d from the work of Close et a l . (1978a) who e s t a b l i s h e d the equation: H = 979.8 - 50.33(T) + 0.9187(T A2) + 0.1366(ME) + 0.0077 (ME)(T) where T i s the environmental temperature i n degrees (C) e s t a b l i s h e d i n the model, and ME i s m e t a b o l i z a b l e energy i n t a k e (kJ/kg A0.75 per day). Equation f o r lower c r i t i c a l temperature [Tc] P a r t 1: Tc ( I ) = 63 - (0.06 B.W.) - (0.067 H ) For the c a l c u l a t i o n of the lower c r i t i c a l temperature (T c ) , ARC (1981) d e r i v e d two equations which are added together to y i e l d Tc. The f i r s t equation used by the ARC (1981) i n c l u d e s H i n the c a l c u l a t i o n as f o l l o w s : Tc = 63.0 - (0.06 B.W.) - (0.067 H) Equation f o r lower c r i t i c a l temperature [Tc] P a r t 2 (degrees C): T c ( I I ) = 38.2 - (0.07 B.W.) - (0.018 [ ( ( f e e d intake) (14020)]/(B.W. A0.75) PIG GROWTH MODEL page 66 The second h a l f of the equation f o r Tc l i n k s the lower c r i t i c a l temperature to ME i n t a k e . The equation i s modified from t h a t presented by Whittemore (1983) by the work of Close et a l . (II) (1978b) as ME (kJ) must be expressed as a f u n c t i o n of B.W.A0.75. Equation f o r lower c r i t i c a l temperature [Tc](degrees C): Tc + Tc(I) + T c ( I I ) Lower c r i t i c a l temperature i s d e r i v e d from the a d d i t i o n of the two equations. Whittemore (1983) suggests t h a t the values d e r i v e d by Close et a l . (1978a,b) seem to under-estimate the lower c r i t i c a l temperature as these equations would show a 20 kg p i g to have a Tc of only about 18 degrees C and grower p i g s a Tc of about 10 degrees C. Whittemore suggests t h a t these equations may be too o p t i m i s t i c under p r a c t i c a l p i g r e a r i n g c o n d i t i o n s . Whittemore and Fawcett (1976) i n t h e i r o r i g i n a l work on modelling suggested the use of the equations e s t a b l i s h e d by Verstegen (1971). Verstegen i n d i c a t e d t h a t f o r pigs i n groups, Tc f a l l s by 0.1 - 0.15 degrees C f o r each 1 kg i n c r e a s e i n l i v e weight. The r e l a t i o n s h i p between Tc and B.W. was t h e r e f o r e expressed as; Tc = 23.8 - (0.15 B.W.). The d e r i v a t i o n of Tc from H fol l o w e d as Tc = 26.6 - (0.59 H). PIG GROWTH MODEL page 67 Whittemore (1983) suggested some r e d u c t i o n s i n the constants of the e a r l i e r work and produced new equations which he used i n h i s 1988 paper (Whittemore, 1988). These equations are shown below and have been added to the model and compared to the work of Close et a l . (1978). Tc = 23 - (0.6 H) and Tc = 23 - (0.4 ME) Equation f o r e f f e c t i v e temperature [EH1] (degrees C): EH1 = [(0.00131 B.W.) + 0.095] [Tc - temp] Given Tc, the extent of c o l d s t r e s s may be c a l c u l a t e d as Tc - temp (Whittemore, 1983). I f the d i f f e r e n c e i s neg a t i v e , there i s assumed to be no d e t r i m e n t a l e f f e c t of ambient temperatures i n excess of Tc ( t h i s i s true only to the extent t h a t e x c e s s i v e l y hot c l i m a t e s are i g n o r e d ) . An i f statement i s added to the equation to allow Tc - temp to be used only when the value i s g r e a t e r than zero. The ARC (1981) added another r o u t i n e to the c a l c u l a t i o n of c r i t i c a l temperature which i s added to the model. The equations which use temp (temperature) can have temp mo d i f i e d a c c o r d i n g to the t y p i c a l c o n d i t i o n s under which the p i g s are housed. An equation f o r the d e r i v a t i o n of temp i s as f o l l o w s (Whittemore, 1988); temp = (temp) (Ve) (VI) Where Ve and VI are taken from Table 7. PIG GROWTH MODEL page 68 Table 7. Scores f o r Ve and VI f o r use i n c a l c u l a t i n g the e f f e c t i v e environmental temperature (temp) i n the equation temp = (temp)(Ve)(VI). RATE OF AIR MOVEMENT AND DEGREE OF INSULATION Ve I n s u l a t e d , not draughty 1.0 Not i n s u l a t e d , not draughty 0.9 I n s u l a t e d , s l i g h t l y draughty 0. 8 I n s u l a t e d , draughty 0.7 Not i n s u l a t e d , draughty 0.6 FLOOR TYPE IN LYING AREA VI Deep straw bed 1. 4 Shallow straw bed 1. 2 No bedding on i n s u l a t e d f l o o r s 1. 0 S l a t t e d f l o o r s with no draughts 1.0 No bedding on u n i n s u l a t e d f l o o r 0.9 S l a t t e d f l o o r with draughts under 0 . 8 No bedding on wet, u n i n s u l a t e d f l o o r 0.7 There i s a second d e r i v a t i o n of the equation EH1 which appeared l a t e r i n Whittemore's (1988) work which has been compared to the c u r r e n t v e r s i o n of EH1. The equation i s as f o l l o w s ; EH1 = 0.012 (B.W.A0.75) (Tc - T) The f i r s t equation seemed to be s a t i s f a c t o r y f o r e s t i m a t i n g EH1 so i t has been r e t a i n e d i n the model. PIG GROWTH MODEL page 69 V MODELLING THE PIG An example of the input and output of the t h e s i s model i s shown i n Appendix 2, pages 1 to 12. The modelled p i g i s c r e a t e d by adding p r o t e i n , f a t , ash and water to a weaner ca r c a s s e s t a b l i s h e d by the modeller. During the e a r l i e r d i s c u s s i o n (page 42), i n i t i a l body compositions f o r p r o t e i n , ash, f a t and water was e s t a b l i s h e d . The 'Edinburgh P i g Model' d e s c r i b e d by Whittemore (1988), allowed f o r a c o n d i t i o n score of weaners which ranged from t h i n to w e l l rounded, with the score being i n c l u d e d i n the equation d e s c r i b i n g i n i t i a l body f a t content. T h i s type of a system i s avoided by a l l o w i n g a d i r e c t i n put of weaner body composition i f i t d i f f e r s from the composition d e s c r i b e d e a r l i e r . P r o t e i n content of the p i g at the s t a r t of the m o d e l l i n g process i s e s t a b l i s h e d a c c o r d i n g to the work of Wood and Groves (1965), Tess et a l . (1986) or numbers e s t a b l i s h e d through s t u d i e s by the modeller. During the c r e a t i o n of the modelled p i g , the equations f o l l o w the sequence below; (1) the i n i t i a l body composition i s set at the i n i t i a l weight and days which are c a l c u l a t e d a c c o r d i n g to the PIG GROWTH MODEL page 70 Gompertz equations e s t a b l i s h e d e a r l i e r . T h i s value i s f i x e d i n the c e l l of the spreadsheet. (2) For the next week, seven times the d a i l y p r o t e i n d e p o s i t i o n c a l c u l a t e d by the model i s then added to the i n i t i a l body composition. (3) The process i s repeated u n t i l market weight i s reached. The i n i t i a l body f a t used i n t h i s model i s e s t a b l i s h e d by Wood and Groves (1965). A value of 0.11 B.W., which r e p r e s e n t s s l i g h t l y b e t t e r than average p i g s o u t l i n e d by Whittemore (1983), or a number e s t a b l i s h e d by the modeller can be used f o r i n i t i a l body f a t c a l c u l a t i o n s . The sequence f o r p r o t e i n a d d i t i o n on a d a i l y b a s i s i s a l s o used f o r f a t . The ash content i s c a l c u l a t e d i n a way s i m i l a r to t h a t used f o r f a t and p r o t e i n , with ash added a c c o r d i n g to the equation of Whittemore (1988); At = At + 0.21 (Pr) [At = t o t a l body ash] The c a r c a s s water content i s d e s c r i b e d by the equation of Whittemore (1983) where; Yt (c a r c a s s water) = 4.9 ((Pt) A0.855) The whole body empty of gut contents (We) i s t h e r e f o r e ; We = Pt + L t + At + Yt Gut contents ( i n g e s t a , d i g e s t a and l a r g e i n t e s t i n a l waste) u s u a l l y comprise about 5 per cent of the l i v e weight, t h e r e f o r e ; PIG GROWTH MODEL page 71 B.W. = 1.05 We From the chemical and p h y s i c a l growth generated i n t h i s s e c t i o n of the model, other p r o d u c t i o n c h a r a c t e r i s t i c s can be generated. U n f o r t u n a t e l y , the P2 measurement of b a c k f a t d e s c r i b e d by most models i s not used i n North America, so a r e l a t i o n s h i p between t o t a l body f a t and back f a t should be found. Ewan (personal communication) suggests the f o l l o w i n g equation which he i s using i n h i s model (USA); Backfat (mm) = 0.91(FAT) + 0.5 where FAT i s t o t a l body f a t (kg). T h i s equation was repo r t e d by Whittemore (1983) and a t t r i b u t e d to Henderson (1982) and i s d e s c r i b e d as a measurement of P2(s) (s standing f o r s e l e c t e d P2). Note: The P2 s i t e i s 65 mm from the m i d - l i n e at the head of the l a s t r i b . T h i s equation could be adapted but the search f o r a b e t t e r r e l a t i o n s h i p should be continued. PIG GROWTH MODEL page 72 VI MODEL DISCUSSION A r e c e n t paper w r i t t e n by Moughan et a l . (1988) f o l l o w i n g a l e c t u r e course on mode l l i n g given at Wageningen U n i v e r s i t y , e s t a b l i s h e d a l i s t of important model components. The paper suggested the components of a growth model co u l d be s p l i t i n t o s i x s e c t i o n s i n c l u d i n g ; (1) Body composition at the s t a r t of growth, (2) Energy and amino a c i d i n t a k e , (3) The u t i l i z a t i o n of in g e s t e d amino a c i d s , (4) The upper l i m i t to d a i l y p r o t e i n r e t e n t i o n , (5) The i n t e r a c t i o n between me t a b o l i z a b l e energy and p r o t e i n i n the d e p o s i t i o n of body l i p i d and p r o t e i n , and (6) P r e d i c t i o n of performance f a c t o r s . The d i s c u s s i o n w i l l i n c l u d e a b r i e f d e s c r i p t i o n of how each of these components was d e a l t with by the model. (1) Body composition at the s t a r t of growth. The modeller e s t a b l i s h e s the body composition at the s t a r t of growth. Survey s t u d i e s i n v o l v i n g the chemical d i s s e c t i o n of young pigs were used to e s t a b l i s h p r o t e i n , l i p i d , ash and water content. The search f o r more data on Canadian p i g s w i l l b e t t e r e s t a b l i s h these parameters but u n t i l then, a mixture of Canadian and European data w i l l be used. PIG GROWTH MODEL page 73 (2) Energy and amino a c i d i n t a k e . An accurate measure of feed intake i s c r u c i a l to the e s t a b l i s h m e n t of an accurate model. The 'Gompertz equations' developed around the growth of F r a s e r V a l l e y p i g s i s a u s e f u l i n n o v a t i o n i n e s t a b l i s h i n g feed i n t a k e f o r ad l i b i t u m - f e d p i g s . B e t t e r measurement of feed intake and growth w i l l be e s t a b l i s h e d over time. Accurate measures of d i g e s t i b i l i t i e s of i n g r e d i e n t s c o u l d i n c l u d e such techniques as rat-based r a p i d assays f o r d i g e s t i b l e energy or the i n c o r p o r a t i o n of near i n f r a r e d t e c h n o l o g i e s f o r feed a n a l y s i s . (3 ) The u t i l i z a t i o n of i n g e s t e d amino a c i d s . S e p a r a t i n g i n g e s t e d amino a c i d s i n t o those needed f o r maintenance and those a v a i l a b l e f o r growth i s p a r t of the mechanics of the model. I l e a l d i g e s t i b i l i t y of each i n d i v i d u a l amino a c i d i s the p r e f e r r e d way of measuring amino a c i d d i g e s t i b i l i t y . Moughan et a l . (1988) suggested t h a t a standard c o e f f i c i e n t f o r p r o t e i n d i g e s t i b i l i t y of 0.85 be used but accurate measures by i l e a l d i g e s t i b i l i t i e s should be used, to avoid l a r g e d i s c r e p a n c i e s i n the p r e d i c t i o n of absorbed amino a c i d s . PIG GROWTH MODEL page 74 (4) The upper l i m i t to d a i l y p r o t e i n r e t e n t i o n . The e stablishment of a maximum l e v e l of d a i l y p r o t e i n d e p o s i t i o n f o r the p a r t i c u l a r genotype and sex of p i g being modelled i s an important parameter c o n t r i b u t i n g to model accuracy. Campbell (1983, 1984, 1987) has c l e a r l y demonstrated t h a t P r A i s an important c o n s i d e r a t i o n when mo d e l l i n g , and has demonstrated the p l a t e a u to d a i l y p r o t e i n d e p o s i t i o n . (5) The i n t e r a c t i o n between the p a r t i t i o n i n g of me t a b o l i z a b l e energy and p r o t e i n i n t a k e and d e p o s i t i o n of body l i p i d and p r o t e i n . The f a c t t h a t p r o t e i n s y n t h e s i s r e q u i r e s energy expenditure while p r o t e i n can a l s o be used as a source of a v a i l a b l e energy means t h a t there i s an i n t e r a c t i o n between p r o t e i n and energy. Whittemore (1983) modelled the i n t e r a c t i o n by c r e a t i n g the parameter Qd which r e p r e s e n t s the energy from deaminated p r o t e i n . Qd i s d e r i v e d from the d i f f e r e n c e between d i g e s t i b l e crude p r o t e i n and the p r o t e i n r e t a i n e d . The sum of the e n e r g e t i c c o s t of maintenance and of p r o t e i n d e p o s i t i o n are connected, because Em i s a f u n c t i o n of metabolic l i v e weight. A l a r g e p a r t of Em i s a s s o c i a t e d with p r o t e i n turnover (perhaps almost a l l ) . Animals which PIG GROWTH MODEL page 75 are growing f a s t e r are d e p o s i t i n g more p r o t e i n at a given body p r o t e i n mass and are t h e r e f o r e expected to have higher r a t e s of p r o t e i n turnover and thus higher Em (Black et a l . , 1986). Whittemore (1987) developed an equation l i n k i n g Em to t o t a l body p r o t e i n , so h i s equation c o u l d be used i n the model r a t h e r than the c u r r e n t equation which r e l a t e s to l i v e weight. The work of P u l l a r and Webster (1977) with groups of lean and c o n g e n i t a l l y obese Zucker r a t s a l s o showed t h a t maintenance energy (Em) i s c l o s e l y r e l a t e d to body p r o t e i n content ( t o t a l body p r o t e i n A0.75). Energy i s used f o r maintenance, l i p i d and p r o t e i n d e p o s i t i o n . The theory of energy being used f i r s t f o r maintenance and then f o r growth i s modified by Whittemore (1983) to i n c l u d e a minimum l e v e l of d a i l y l i p i d d e p o s i t i o n which w i l l t r i g g e r the deamination of p r o t e i n to supply energy f o r l i p i d s y n t h e s i s , but t h i s occurs only during s t a r v a t i o n . (6) P r e d i c t i o n of performance f a c t o r s . The u s e f u l n e s s of a model r e s t s on the a b i l i t y to use the p r e d i c t i o n of performance f a c t o r s to economic advantage. The amount of use gained from the p r e d i c t i o n s w i l l probably depend on the t r u s t placed i n the p r e d i c t i o n s of the model. PIG GROWTH MODEL page 76 Thus, model proof becomes an important step i n model development. A b e t t e r equation r e l a t i n g t o t a l body f a t to b a c k f a t and thus grading index needs to be obtained and added to the model. The t e x t of t h i s t h e s i s suggested the use of an equation d e s c r i b e d by Whittemore (1983) r e f l e c t i n g the work of Henderson (1982) but an equation obtained from Canadian sources would be a v a l u a b l e a s s e t . Many changes have taken pl a c e i n the Canadian p i g c a r c a s s grading system s i n c e the i n t r o d u c t i o n of the e l e c t r o n i c grading probes on March 31, 1986 ( F o r t i n , 1989). The e l e c t r o n i c grading i n c l u d e s an estimated lean y i e l d which i s d e r i v e d from f a t t h i c k n e s s and muscle depth measured on the l e f t side of the c a r c a s s at the 3/4 l a s t r i b s , 7 cm l a t e r a l to the exposed s u r f a c e of the s p l i t c a r c a s s . For modelling purposes, a c o r r e l a t i o n between t o t a l body f a t and f a t t h i c k n e s s as w e l l as a c o r r e l a t i o n between t o t a l body p r o t e i n and muscle depth i s necessary f o r an accurate estimate of grading index. A study d e f i n i n g the r e l a t i o n s h i p s mentioned above would improve model p r e d i c t i v e performance. Such a study with Canadian pigs and the new Canadian grading system could not be found. A model of n u t r i e n t flow i s a l s o a very u s e f u l way of demonstrating model mechanics. The flow developed by PIG GROWTH MODEL page 77 Moughan et a l . (1988) and Whittemore (1987) have been adapted to the c u r r e n t model and i s demonstrated by Fi g u r e 9. The p a r t i t i o n i n g of energy i n t o p r o t e i n - f r e e d i g e s t i b l e energy i s shown i n the flow c h a r t . I n t e r a c t i o n s between energy of maintenance and p r o t e i n deaminated, l i p i d r e t a i n e d and p r o t e i n r e t a i n e d , t o t a l body l i p i d and t o t a l body p r o t e i n , and t o t a l body p r o t e i n and t o t a l body water are a l s o shown i n F i g u r e 9. The importance of these parameters have been p r e v i o u s l y d i s c u s s e d i n the t h e s i s . An i n t e g r a t e d p i g model i s more responsive to changes i n p r o d u c t i o n e f f i c i e n c y brought about by growth and compounds which change the t i s s u e composition of growth than e m p i r i c a l or requirement type models. Reviews of the e f f e c t of somatotropin and be t a - a g o n i s t s (Beermann, 1988) i n d i c a t e g r e a t e r e f f e c t s on feed e f f i c i e n c y , average d a i l y gain and ca r c a s s composition than those made by n u t r i t i o n and g e n e t i c s i n the l a s t ten years. Somatotropin i s a n a t u r a l l y o c c u r r i n g hormone s e c r e t e d by the p i t u i t a r y gland, while b e t a - a g o n i s t s are s y n t h e t i c hormone-like compounds which are s t r u c t u r a l l y s i m i l a r to epinephrine and norepinephrine. These compounds are a l l i n v o l v e d with growth and allow a marked r e p a r t i t i o n i n g of n u t r i e n t s towards g r e a t e r muscle p a g e 7 8 Figure 9. Flow diagram simulating nutrient utilization by the growing pig combining concepts of Moughan et al. (1988) and Whittemore (1987). FEED f DCP — Pm 1 IPt-IPm IPr - • P x 11 1 DE 1 Epf T MEt-*—? - Qd Em We LT + PT + AT + YT 1 DCP Digestible Crude Protein DE Digestible Energy Epf Protein-free Digestible Energy Px Protein Turnover Pr~ Maximum Protein Retention IPt Total Ideal Protein Ingested IPm Ideal Protein of Maintenance IPr Ideal Protein Retained MEt Effective Metabolizable Energy Pm Protein Deaminated Qd Energy Derived from Protein H Heat Output Deaminated Lr Lipid Retained Em Energy of Maintenance LT Total Lipid, Mature We Mature Empty Body Weight AT Total Ash, Mature PT Total Protein, Mature YT Total Body Water, Mature 1,2,3 , 4 : interactions PIG GROWTH MODEL page 79 growth and l e s s f a t d e p o s i t i o n . The i n t e g r a t e d model i s probably b e t t e r able to handle estimates of the e f f e c t of these products and w i l l probably b e t t e r adapt to changes brought about by these products. P r o d u c t i o n s t u d i e s with these compounds al r e a d y p r e d i c t e f f e c t s of changes i n body water, f a t , p r o t e i n and ash, which are the b a s i s f o r the i n t e g r a t e d models (Beerman, 1988). A very important aspect of model use i s the a b i l i t y to develop and t e s t changes i n c u r r e n t management or f e e d i n g p r a c t i c e s t h a t c o u l d lead to an economic improvement. Model mechanics can be used to i n d i c a t e n u t r i e n t changes t h a t can be expected to improve performance. P r o t e i n d e p o s i t i o n i s an example of a model component which can be i n v e s t i g a t e d i n order to improve performance. D i g e s t i b i l i t y i s a measure of the d i f f e r e n c e between the feed eaten and the feed e x p e l l e d i n the f e c e s ; i n other words, the feed p a s s i n g the i n t e s t i n a l mucosa of the d i g e s t i v e t r a c t . The d i g e s t i b l e m a t e r i a l i s what i s absorbed by the animal. For p r o t e i n , t h i s has been represented g r a p h i c a l l y as l i n e A of F i g u r e 10 which forms p a r t of the growth model output. Once the amino a c i d s ( p r o t e i n components) have been absorbed, f u r t h e r l o s s e s occur. The f i r s t l o s s i s the PIG GROWTH MODEL page 80 p r o t e i n used f o r maintenance as d i s t i n c t from growth needs. Although, to a l a r g e p a r t , t h i s l o s s i s a ba s a l b i o l o g i c a l c o s t , poor environment and s t r e s s can i n c r e a s e the p r o p o r t i o n of p r o t e i n which i s used f o r maintenance. The second l o s s i s probably one of the more important l o s s e s which can be manipulated by the n u t r i t i o n i s t . T h i s l o s s i s a f f e c t e d by ' b i o l o g i c a l v a l u e ' (B.V.) which compares the amino a c i d composition of d i e t p r o t e i n to the ' i d e a l ' composition r e q u i r e d by the animal. The l e v e l of d e p o s i t i o n of d i g e s t i b l e crude p r o t e i n i n the car c a s s i s a f f e c t e d by both the maintenance p r o t e i n c o s t and the B.V. of the in g e s t e d p r o t e i n . The p r o t e i n a v a i l a b l e f o r growth i s represented by l i n e B i n Figu r e 10. The p r o t e i n which i s a v a i l a b l e to be r e t a i n e d w i l l not n e c e s s a r i l y be r e t a i n e d . R e t e n t i o n i s dependent on the g e n e t i c a b i l i t y of the animal to d e p o s i t p r o t e i n ( P r A ) (See L i t e r a t u r e Review, Important M o d e l l i n g Concepts). Pr" i s shown i n F i g u r e 10 by l i n e C. The dip t h a t occurs i n a l l three l i n e s at p o i n t D i s merely a r e f l e c t i o n of a change i n crude p r o t e i n i n t a k e , which r e l a t e s to a change i n the l e v e l of d i e t a r y p r o t e i n when t r a n s f e r r i n g from a s t a r t e r to grower d i e t . The example feeding program demonstrated i n Figu r e 10 i n d i c a t e s to the modeller an area where p i g growth could be improved. When l i n e B drops below l i n e C, p r o t e i n PIG GROWTH MODEL page 81 d e p o s i t i o n decreases below i t s t h e o r e t i c a l maximum, thereby d e p r e s s i n g growth. A change i n d i e t a r y p r o t e i n intake d u r i n g the p e r i o d t h a t the two l i n e s c r o s s , could l e a d to an improvement i n p i g growth. F i g u r e lO: Graph of a Model Derived Comparison of" D i e t a r y Crude Pro t e i n A v a i l a b l e t o be U t i l i s e d , D i g e s t i b l e Crude P r o t e i n A v a i l a b l e f o r P r o t e i n A c c r e t i o n and the Pro t e i n A c t u a l l y Retained due t o Genotype and Phenotype L i m i t a t i o n s . co cu > < a \ w Y. Z UJ I-o IT CL 49 | 63 | 77 | 91 | 105 56 70 84 98 1 AGE (DAYS) PROTEIN AVAILABLE + PROTEIN RETAINED 126 140 154 168 O DIG. CRUDE PROTEIN PIG GROWTH MODEL page 83 V I I MODEL V E R I F I C A T I O N S T U D Y (1) M A T E R I A L S AND METHODS Model proof i s an important p a r t of model development. Computer-based l i q u i d f e e d i n g systems have been i n t r o d u c e d l o c a l l y and provide an accurate measure of feed dry matter i n t a k e . A n a l y s i s of feed i n t a k e s on l i q u i d f e e d i n g systems had i n d i c a t e d t h a t t r a d i t i o n a l estimates (eg. NRC, 1988) of feed i n t a k e may not a c c u r a t e l y r e p r e s e n t feed i n t a k e s a c t u a l l y achieved i n the f i e l d . In the present study, the only f a c i l i t i e s a v a i l a b l e f o r accurate measurements of growth r a t e and feed intake were l o c a t e d at the U.B.C. Swine U n i t . Consequently, a t r i a l was c a r r i e d out i n t h i s f a c i l i t y . Four d i e t s were formulated to bracket the 16 % crude p r o t e i n d i e t recommended by the Swine NRC (1988) Group, with crude p r o t e i n ranging from s l i g h t l y higher to s l i g h t l y lower than recommended. The d i f f e r e n c e s i n d i e t a r y energy c o n c e n t r a t i o n between a barley-soybean meal d i e t and a corn-soybean meal d i e t (on which the NRC requirements are based) means t h a t d i f f e r e n t p r o t e i n to d i g e s t i b l e energy and l y s i n e PIG GROWTH MODEL page 84 to d i g e s t i b l e energy r a t i o s w i l l e x i s t . The d i e t composition and estimated a n a l y s i s i s shown i n Table 8: Table 8. D i e t Composition and Estimate N u t r i e n t A n a l y s i s ( a i r - d r y b a s i s ) DIET NUMBER 1 2 3 4 B a r l e y 80. 26 83. 13 84. 61 88 . 44 Soybean Meal 16 . 8 13. 9 12 . 4 9 . 53 Di c a l c i u m Phosphate 0.71 0. 74 0 . 76 0. 79 Limestone 1. 23 1. 23 1 . 23 1. 24 TM-Vitamin Mix 0. 5 0. 5 0. 5 0.5 I o d i z e d S a l t 0. 5 0. 5 0. 5 0. 5 ESTIMATED COMPOSITION Crude P r o t e i n 17 . 0 16. 0 15.5 14 . 5 Calcium 0.7 0. 7 0 . 7 0.7 Phosphorus 0. 6 0. 6 0. 6 0.6 Ly s i n e 0.77 0. 70 0.66 0. 58 A l l f o u r d i e t s were prepared at the A g r i c u l t u r e Canada Research S t a t i o n at A g a s s i z , B.C. and were shipped by t r u c k to the Department of Animal Science Farm, U.B.C. The premix was s u p p l i e d by U.B.C. Estimates of the composition of d i e t a r y components on which d i e t f o r m u l a t i o n s were based are presented i n Table 9. Premix composition i s a l s o presented i n Table 9. PIG GROWTH MODEL page 85 Table 9. Estimated I n g r e d i e n t Composition B a r l e y Soybean Meal D i c a l c i u m Phosphate Limestone C P . 11. 5 46 .0 Ca 0.08 0. 32 P 0 . 42 0.67 L y s i n e 0.35 2 . 90 25 38 20 TM -Vitamin mix c o n t a i n s the f o l l o w i n g c o n c e n t r a t i o n per kg: Vitamin A 825,000 IU: Vitamin D 55,000 IU; Vitamin E 2,700 IU: Vitamin K 0.4 g; Thiamin 0.1g; R i b o f l a v i n 0.8 g ; N i a c i n 4.0 g ; Ca pantothenate(45%) 6.0 g; B 12 2.5 mg,- Choline 50.0 g; Copper Sulphate 3.0 g; Zinc Sulphate 25.0 g; Manganese Sulphate 7.0 g; Sodium S e l e n i t e 15.7 mg. Each of the fou r d i e t s were o f f e r e d to group-fed p i g s i n p a r t i a l l y - s l a t t e d pens (1.8 by 2.4 meter). The pigs were fed twice d a i l y with the feed l e v e l a d j u s t e d at each f e e d i n g . I f feed remained approximately one hour a f t e r f e e d i n g , feed was decreased at the next f e e d i n g . I f no feed remained i n the feeder one hour a f t e r f e e d i n g , feed l e v e l was i n c r e a s e d , to t e s t i f more feed would be consumed. Each pen contained e i t h e r 6 male c a s t r a t e or 6 female p i g s . A l l p i g s were placed on t r i a l at approximately 25 kgs body weight and were weighed weekly. As each p i g obtained a body weight of 100 kgs, i t was sent to market. When the PIG GROWTH MODEL page 86 second l a s t p i g obtained t h i s weight, the l i g h t e s t p i g , even i f l e s s than 100 kgs, was a l s o sent to market. In t o t a l , 73 pens were i n v o l v e d i n the experiment. D i e t 1 was fed to 10 pens of barrows and 11 pens of g i l t s ; d i e t s 2 and 3 were each provided to 9 pens of barrows and 8 pens of g i l t s ; d i e t 4 was provided to 8 pens of barrows and 10 pens of g i l t s . From the t o t a l data c o l l e c t e d , problems with the feed intake data l e d to the i n c l u s i o n of 5 pens f o r data a n a l y s i s f o r each of the t r i a l d i e t s and sexes. Information on car c a s s weight and grade were r e c e i v e d from the packing p l a n t . In t o t a l , 165 samples were taken from a l l the d i e t s at d i f f e r e n t dates and were combined to form ten samples per d i e t . The samples were ground i n a hammer m i l l and st o r e d i n a deep f r e e z e . They were then analyzed f o r moisture and crude p r o t e i n content. Crude p r o t e i n was estimated as n i t r o g e n times 6.25. The samples were d i g e s t e d i n a mixture of hydrogen peroxide and s u l p h u r i c a c i d with a selenium c a t a l y s t . The n i t r o g e n was measured c o l o u r i m e t r i c a l l y i n an aut o a n a l y s e r , u s i n g the method of Fukumoto and Chang (1982). PIG GROWTH MODEL page 87 (2) Data A n a l y s i s The data from 414 p i g s were c o l l e c t e d with the data from 240 i n c l u d e d i n the feed intake p o r t i o n of the study. The data from 368 p i g s were used f o r the weekly growth summaries. The data from fewer p i g s were used f o r a n a l y s i s because of d e f i c i e n c i e s i n the data c o l l e c t e d (such as mis s i n g data from a s i n g l e weighing due to t e c h n i c i a n time c o n s t r a i n t s ) . Any pigs with missing data were dropped from t h a t p o r t i o n of the study. The experimental design was completely randomized with f a c t o r i a l a l l o c a t i o n of treatments. Data were analyzed through a data management system devised f o r Lotus 123 which produced summaries of means, standard d e v i a t i o n and v a r i a n c e . A n a l y s i s of Variance (two-way c l a s s i f i c a t i o n with i n t e r a c t i o n [p<0.05 unless otherwise i n d i c a t e d ] ) , t t e s t s , r e g r e s s i o n s and Duncan's M u l t i p l e Range t e s t s were c a r r i e d out where necessary a c c o r d i n g to the methods o u t l i n e d i n ' I n t r o d u c t i o n to S t a t i s t i c s ' (Walpole, 1982). Feed intake data was c o l l e c t e d from 69 pens (from an average s t a r t i n g p i g weight of 24.59 kgs) but the data from o n l y 40 pens was i n c l u d e d i n the data a n a l y s i s due to data l o s s . Although data were c o l l e c t e d u n t i l a l l p i g s were marketed, a n a l y s i s ceased as soon as any p i g s were removed PIG GROWTH MODEL page 88 from a pen. Intake data a n a l y s i s was stopped at t h i s p o i n t because of the p o s s i b l e e f f e c t of changes i n s t o c k i n g d e n s i t y on feed intake and the r e d u c t i o n i n mean performance of the more slo w l y growing remaining p i g s . Data a n a l y s i s i n c l u d e d the t w e l f t h week from the t r i a l s t a r t but the 26 pens i n which p i g s remained at the end of week 13, were thought to be inadequate f o r a n a l y s i s . The p i g s were graded by A g r i c u l t u r e Canada i n s p e c t o r s u s i n g the 'Hog Carcass Grading R e g u l a t i o n s , 1986 (Canada Gazette P a r t I I , V o l . 120, No. 8 ) ' , at an approved s l a u g h t e r f a c i l i t y . P i g c a r c a s s e s were evaluated using the weight of the c a r c a s s and the lean y i e l d of the c a r c a s s . Lean y i e l d i s estimated from the f a t t h i c k n e s s and muscle depth measured at a l o c a t i o n between the 3rd and 4th l a s t r i b s and 7 cm l a t e r a l to the m i d - l i n e . According to De Boer's d e f i n i t i o n of c l a s s i f i c a t i o n systems and grading, the system has elements of both a c l a s s i f i c a t i o n system and a grading scheme (De Boer, 1984). The c l a s s i f i c a t i o n p o r t i o n r e l a t e s to establishment of lean y i e l d and c a r c a s s weight while the grading system r e l a t e s to an assignment of a y i e l d c l a s s value and weight c l a s s value. The c l a s s values are used to d e r i v e an index r e p r e s e n t i n g the p r o p o r t i o n of the b i d p r i c e r e c e i v e d f o r a c a r c a s s . PIG GROWTH MODEL page 89 (3) RESULTS The a n a l y s i s of the a c t u a l crude p r o t e i n l e v e l i n the four experimental d i e t s i s demonstrated i n Table 10 with a comparison to the p r e d i c t e d crude p r o t e i n . The d i f f e r e n c e between p r o j e c t e d and a c t u a l crude p r o t e i n i n d i e t s 1 and 3 i n d i c a t e s p o s s i b l e mixing e r r o r s which c o u l d have improved performance on d i e t 1 while h i n d e r i n g performance on d i e t 3 Table 10. Crude P r o t e i n (N(6.25))of T r i a l D i e t s by A n a l y s i s (g/100 g as fed) [10 composite samples f o r each d i e t c r e a t e d from 165 samples c o l l e c t e d ] i ! D i e t % Crude P r o t e i n S.D. i P r o j e c t e d C P . ! ! 1 17.91 0.54 17.0 ! ! 2 16.54 0.65 16.0 ! ! 3 14.69 1.61 15.5 ! ! 4 14.60 1.05 14.5 ! S.D.= standard d e v i a t i o n Table 11 i n d i c a t e s the e f f e c t of d i e t treatments on performance c h a r a c t e r i s t i c s of swine and i n c l u d e s a ANOVA summary. An a n a l y s i s of va r i a n c e of the l i v e weight at sh i p p i n g and ca r c a s s weight at s l a u g h t e r d i d i n d i c a t e a s i g n i f i c a n t d i f f e r e n c e between sexes f o r d i e t treatment (p<.05). Tables 12 and 13 are i n c l u d e d to separate d i f f e r e n t means i n t o subsets of homogenous means. page 90 page 91 D Ul D If H* 8% S S 8 2 S \fl f\J w v v ro u -\1 O I I I ! [*} u s s S 8 a ^ Q \D (0 v w /^ 0 CO to I 1 i3 in s y s H 2 ISJ u w v O M "M A • ( I • fo U $ Ul 5 Q Ul ff> in o B 8 A 8 31 2! j 8 O D D H- H' H-O 3- 8- $ * A (0 M N p\ 0\ Ul iii b H io ~\J \D ~\l ~\l Ul £ Ul £ 8 sd 3! ft 8 8 2 2 k fa fa (0 in 8 8 2 8 6 * 1 k Ul r H' i s Be 8 8 8 9 i{| 8 21 3! 21 58 8 j 8 ID Table 11 Ccent. 5 E f f e c t s of Diet, arid Sew or. Pter-fotnroanc© Char-soter-i s t i e s o f Swire with FMDMH sumnary CM ON I Variable i 1 rt—jg t o Kler-taet 1 SI S2 iDiet 1 1 1 166.63 165. t^E: 1 IDiot 2 1 1 1ST". 91 16S.66 IDiot 3 I 1 167.OO 171. 09 i i 1 168.83 174.31 • ISEM 1 I 11. 5? 1 Sex I nean • • IMale 1 167. 59 1 ! Female i i . . . • .. 169. 8? IHNQVfl SLTMHRY 1 ! Scxrce of 1 1 V a r i a t i o n Cdf ) 1 * • 1 ... IDiefc 1 1 C35 365.56 X * 1 ISGC< 1 1 C15 363. *43 1 !Di©<t by Seo< ! 1 C3> 163.39 1 i 1 C2723 141.80 i !Total 1 C27"95 51 = males S2 = females SEM = standard e m o r of the moan X P < D . 0 5 *3* p<D. lO PIG GROWTH MODEL page 93 Table 12. P i g Performance on T r i a l D i e t s (Males) j i 1 DIET 2 NUMBER 3 4 ; Mean ! ! f e e d / p i g (kg) 217.75 220.13 219.45 239.06 224.10 ! ! feed/ g a i n 2 . 86a 3.01b 3.01b 3. 16c 3.01 ! ! A.D.G. (gms) 810a 791ab 748c 772bc 7 80 ! ! days to market ! (p<.10) 166.63a 167.91a 167.00a 168.83a 167.59 ! ! index 107.51a 106.34b 106.57b 104.74c 106.29 ! ! y i e l d c l a s s 5 . 97a 6 . 17a 6 . 09a 7 . 37b 6 . 40 ! Note: Means w i t h i n a row with no common s u p e r s c r i p t l e t t e r s are s i g n i f i c a n t l y d i f f e r e n t (p<.05) ac c o r d i n g to Duncan's m u l t i p l e range t e s t . PIG GROWTH MODEL page 94 Table 13. P i g Performance on T r i a l D i e t s (Females) ! 1 D i e t 2 Number 3 4 i mean ! ! f e e d / p i g (kg) 211.90 221.15 226.33 249.55 227.23 ! ! feed / g a i n 2 . 78a 2 . 88b 3.02c 3. 20d 2. 97 ! ! A.D.G. (gms) 787 789 721 706 751 ! ! days to market ! (p<0.10) 165.43a 168.66b 171.09c 174.31d 169.87 ! ! index 109.06 107.11 109.49 107.77 108.35 ! ! y i e l d c l a s s 4. 86 5 . 74 4 . 97 5 . 83 5.35 ! Note: Means w i t h i n a row with no common s u p e r s c r i p t l e t t e r s are s i g n i f i c a n t l y d i f f e r e n t (p<.05) ac c o r d i n g to Duncan's m u l t i p l e range t e s t (unless otherwise i n d i c a t e d ) . An a n a l y s i s of v a r i a n c e of the l i v e weight at s h i p p i n g and c a r c a s s weight at s l a u g h t e r d i d i n d i c a t e a s i g n i f i c a n t d i f f e r e n c e between d i e t treatments f o r both sexes (p<0.05). PIG GROWTH MODEL page 95 Table 14. L i v e Weight(kg) f o r T r i a l D i e t s and Carcass Weight(kg) at Market ; D i e t Number i i 1 2 3 4 ! ! l i v e weight (males) 101 23a 101 23a 102 63b 103 . 14b ! ! l i v e weight (females)102 17ab 101 74a 103 46c 102 . 60b ! ! c a r c a s s (males) 79 37a 77 89c 79 89ab 80 . 09b ! ! c a r c a s s (females) 79 60a 78 23b 79 83a 80 . 89c ! Note: Means w i t h i n a row with no common s u p e r s c r i p t l e t t e r s are s i g n i f i c a n t l y d i f f e r e n t ( p < . 0 5 ) according to Duncan's m u l t i p l e range t e s t . Table 14 shows t h a t s h i p p i n g weights were g e n e r a l l y h e a v i e r on d i e t s 3 and 4 than on d i e t s 1 and 2. T h i s c o u l d e x p l a i n the trend to longer days to market with d e c r e a s i n g d i e t p r o t e i n . PIG GROWTH MODEL page 96 (a) Feed Intake A n a l y s i s The f o l l o w i n g t a b l e r e p r e s e n t s the d a i l y feed intake across a l l d i e t s and a model p r e d i c t i o n of feed i n t a k e ; Table 15. D a i l y Feed Intake by Week, A c t u a l Vs. Model ! Week n Mean S. D. model p r e d i c t i o n ! ! 1 69 0 84 0. 583 1 463 ! ! 2 69 1 52 0. 185 1 794 ! • 3 69 1 75 0 234 1 980 ! ! 4 69 1 96 0. 264 2 156 ! ! 5 69 2 17 0 270 2 318 ! ! 6 69 2 36 0 270 2 468 ! ! 7 69 2 48 0 253 2 616 ! ! 8 69 2 59 0 284 2 750 ! ! 9 69 2 70 0 294 2 872 ! ! 10 68 2 75 0 257 2 981 ! ! 11 65 2 78 0 268 3 078 ! ! 12 52 2 80 0 271 3 164 ! Fi g u r e 11 compares the model-derived feed intake and the a c t u a l feed intake as w e l l as the standard d e v i a t i o n and a confidence i n t e r v a l f o r the t r i a l feed i n t a k e . In order to i n d i c a t e mathematically the r e l a t i o n s h i p between the feed i n t a k e data c o l l e c t e d and the model-derived feed intake p r e d i c t i o n , the f o l l o w i n g a n a l y s i s was c a r r i e d out; A polynomial r e g r e s s i o n was c a l c u l a t e d using the model Figure 11: fl Comparison Between Model Derived Feed Intake and the Feed Intake Observed on T r i a l ON CD cd ft (0 "0 '5 a 3.4 3.2 3 2.8 2.6 2.4 2.2 2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 •< * [__ -s R -E •—• * ! * 3 ; h I i i . //ll /// > < /// i WK1 WK2 WK3 WK4 WK5 WK6 WK7 WK8 WK9 WK10 WK1 1 WK12 • TRIAL DATA WEEKS FROM START OF TRIAL + MODEL PREDICTION J + / - 1 S.D. V + 95% Confid. level X - 95% Confid. level PIG GROWTH MODEL page 98 p r e d i c t i o n and the a c t u a l data. The equation d e r i v e d was as f o l l o w s : Y = -2.7392 + 2.9037 (X) - 2.460 (X A2) - 0.0379 (X A3) where Y r e p r e s e n t s the a c t u a l feed intake and X, the model p r e d i c t e d feed i n t a k e . The c o e f f i c i e n t of d e t e r m i n a t i o n was estimated as r A 2 = 0.9978. The value i n d i c a t e s a s i m i l a r i t y i n shape between the p r e d i c t e d and a c t u a l curves but does not i n d i c a t e the d i s t a n c e between the curves. A t t e s t was c a r r i e d out f o r the feed intake at each week i n order to t e s t i f the two p o i n t s were s t a t i s t i c a l l y d i f f e r e n t . The t t e s t i n d i c a t e d t h a t the two curves were s i g n i f i c a n t l y d i f f e r e n t , with the s i m i l a r i t y being c l o s e s t around week 6 and f a r t h e s t at each end of the t r i a l . T h i s i s demonstrated by F i g u r e 12 showing a comparison of t values i n r e l a t i o n to the s i g n i f i c a n t value of 2.000. The feed i n t a k e a n a l y s i s demonstrated a phenomenon widely observed i n the f i e l d , which has been r e f e r r e d to as the "pneumonia s t a l l - o u t " . The U.B.C. swine herd was repopulated with s p e c i f i c pathogen f r e e (SPF) breeding stock i n 1979 but s i n c e t h a t time, e n z o o t i c pneumonia has been i d e n t i f i e d i n the herd. The feed intake i n c r e a s e d as expected u n t i l the pigs reached about week 9 of the t r i a l , at which time feed intake l e v e l l e d o f f . T h i s r e d u c t i o n i n the i n c r e a s e i n feed intake can have a s i g n i f i c a n t e f f e c t on page 99 T VALUE OBTAINED PIG GROWTH MODEL page 100 d i e t recommendations i f the r e d u c t i o n i s severe enough. In cases of s u b s t a n t i a l pneumonia problems, feed intake can a c t u a l l y reduce and l e v e l o f f a t / o r below approximately 2.5 kgs per day. With body weight c o n t i n u i n g to i n c r e a s e and t h e r e f o r e maintenance requirements c o n t i n u i n g to i n c r e a s e , a p r o t e i n d e f i c i e n c y can be induced. (b) E f f e c t of D i e t Composition on Feed E f f i c i e n c y The e f f e c t of d i e t on feed e f f i c i e n c y i s shown below; Table 16 Feed Conversion of T r i a l D i e t s ! Males ! D i e t Feed Conversion ! (g feed/g gain) S.D. ! Females ! Feed Conversion S.D. ! (g feed/g gain) ! ! 1 2.86 a 0 . 03 ! 2.78 a 0.03 ! ! 2 3.01 b 0 .11 ! 2.88 b 0.11 ! ! 3 3.01 b 0 .05 ! 3.02 c 0.07 ! ! 4 3. 1 6 c 0 .11 ! 3.20 d 0.06 ! Note: Means w i t h i n a column with no common s u p e r s c r i p t l e t t e r s are s i g n i f i c a n t l y d i f f e r e n t ( p < . 0 5 ) a c c o r d i n g to Duncan's m u l t i p l e range t e s t . The data i n d i c a t e t h a t feed c o n v e r s i o n s can be improved with i n c r e a s e d d i e t a r y p r o t e i n . The a n a l y s i s of v a r i a n c e f o r f eed/gain by sex d i d not i n d i c a t e a s t a t i s t i c a l PIG GROWTH MODEL page 101 d i f f e r e n c e (p<0.05) with a mean of 3.01 f o r the males (sex 1) and a mean of 2.97 f o r the females (sex 2). (c) E f f e c t of D i e t on Days to Market The r e l a t i o n s h i p between d i e t and days from b i r t h to market i s shown i n Table 17: Table 17 E f f e c t of D i e t P r o t e i n on Days to Market ! D i e t Males ! days ( b i r t h S.D. ! to market) ! Females ! days ( b i r t h S.D. ! to market) ! ! 1 166.63 a 9.221 ! 165.43a 6.925 ! ! 2 167.91 a 11.054 ! 168.66 b 12.622 ! ! 3 167.00 a 14.730 ! 171.09 c 11.108 ! ! 4 168.83 a 11.443 ! 174.31 d 15.475 ! Note: Means w i t h i n a column with no common s u p e r s c r i p t l e t t e r s are s i g n i f i c a n t l y d i f f e r e n t ( p < . 0 5 ) a c c o r d i n g to Duncan's m u l t i p l e range t e s t . The data i n d i c a t e d a s i g n i f i c a n t improvement i n days to market with i n c r e a s i n g d i e t a r y p r o t e i n f o r the females but d i d not i n d i c a t e a s i m i l a r improvement f o r the males. The l e v e l of s i g n i f i c a n c e i n t h i s t e s t was s e t to 0.10. PIG GROWTH MODEL page 102 The a n a l y s i s of v a r i a n c e procedure i s not very s e n s i t i v e to departures from the assumption of equal v a r i a n c e s between treatments but a B a r t l e t t ' s t e s t was run to t e s t the homogeneity of the d i e t v a r i a n c e s (Walpole, 1982). The d i s t r i b u t i o n of the data f o r the females produced v a r i a n c e s which were not determined to be equal suggesting the data may not come from a homogeneous p o p u l a t i o n . More data was c o l l e c t e d f o r females than males and when the a d d i t i o n a l data was i n c l u d e d f o r the B a r t l e t t ' s t e s t , the v a r i a n c e s became homogenous so the data was co n s i d e r e d adequate f o r model p r e d i c t i o n a n a l y s i s . The data f o r the males and females was pooled f o r the model p r e d i c t i o n a n a l y s i s (see Table 20). (d) E f f e c t of D i e t on Carcass Index The e f f e c t of d i e t on c a r c a s s index f o r the males i s demonstrated i n Table 18. The data f o r the females was not i n c l u d e d as a n a l y s i s of p o p u l a t i o n v a r i a n c e s with the B a r t l e t t ' s t e s t i n d i c a t e d t h a t the v a r i a n c e s a s s o c i a t e d with d i e t treatments c o u l d not be considered homogenous. The ANOVA summary i n Table 11 i n d i c a t e d the presence of an i n t e r a c t i o n which could mask s i g n i f i c a n t d i f f e r e n c e s between d i e t and sex i f they had not a l s o been i n d i c a t e d (Walpole, 1982). PIG GROWTH MODEL page 103 Table 18 E f f e c t of D i e t on Carcass Index (Males) ! D i e t 1 S.D.! D i e t 2 S.D.! D i e t 3 S.D. ! D i e t 4 S.D.! ! 107.51 ; i 2.08! 106.34 3.06! i i 106.57 2.61 ! 104.74 2.64 ! | | ! a ! b ! ; j b ! c ! i i Note: Means w i t h i n a row with s i g n i f i c a n t l y d i f f e r e n t ( p < . 0 5 m u l t i p l e range t e s t . no common l e t t e r s are ) acc o r d i n g to Duncan's The data i n d i c a t e a general improvement i n car c a s s index with i n c r e a s i n g d i e t a r y p r o t e i n . (e) E f f e c t of D i e t on Carcass Y i e l d The e f f e c t of d i e t on ca r c a s s y i e l d f o r the males i s demonstrated i n Table 19. The data f o r the females was not i n c l u d e d as a n a l y s i s of p o p u l a t i o n v a r i a n c e s with the B a r t l e t t ' s t e s t i n d i c a t e d t h a t the v a r i a n c e s a s s o c i a t e d with d i e t treatments c o u l d not be con s i d e r e d homogenous. Using a l o g a r i t h m i c t r a n s f o r m a t i o n , the B a r t l e t t ' s t e s t (Walpole, 1977) d i d not change the v a r i a n c e a n a l y s i s . PIG GROWTH MODEL page 104 Table 19. E f f e c t of D i e t on Carcass Y i e l d Class(males) j ! D i e t 1 S.D. ! ! ! ! D i e t 2 S.D.! D i e t 3 S.D. ! D i e t 4 S. j D. ! i ! 5.97 1 i ! a . 21 ! ! ! ! 6.17 1.54 ! 6.09 1.59 ! 7.37 1. i i i • a ! a ! b t 38 ! i ; Note: Means w i t h i n a row with no common l e t t e r s are s i g n i f i c a n t l y d i f f e r e n t ( p < . 0 5 ) a c c o r d i n g to Duncan's m u l t i p l e range t e s t . The i n c r e a s e i n l i v e w e i g h t at s h i p p i n g could have a f f e c t e d the c a r c a s s y i e l d c l a s s and index. The index system c e n t r e s around a p r e f e r r e d c a r c a s s weight which corresponds to a l i v e weight of 100 kgs. The h e a v i e r marketing weights ( d i e t s 3 and 4 (p <0.05)) could have a f f e c t e d the c a r c a s s index and y i e l d r e s u l t s , s l i g h t l y lowering the index on d i e t s 3 and 4. (f) E f f e c t of D i e t on Average D a i l y Gain The e f f e c t of d i e t on average d a i l y gain i s demonstrated i n Table 20. As with the data f o r days to market, c a r c a s s index and c a r c a s s y i e l d , the average d a i l y g a i n f o r the females i s not i n c l u d e d i n Table 20 as a n a l y s i s of p o p u l a t i o n v a r i a n c e s with the B a r t l e t t ' s t e s t i n d i c a t e d PIG GROWTH MODEL page 105 th a t the v a r i a n c e s a s s o c i a t e d with d i e t treatments could not be c o n s i d e r e d homogenous. Table 20. E f f e c t of D i e t on Average D a i l y Gain [gms] (Males) ! D i e t 1 S.D. ! D i e t 2 S.D. ! D i e t 3 S.D. ! D i e t 4 S.D.! 810 32.1 791 54.4 ab 748 71.9 772 27.3 be Note: Means w i t h i n a row with no common l e t t e r s are s i g n i f i c a n t l y d i f f e r e n t ( p < . 0 5 ) a c c o r d i n g to Duncan's m u l t i p l e range t e s t . The h e a v i e r marketing weights ( d i e t s 3 and 4 (p<0.05)) would be expected to have l e s s e f f e c t on average d a i l y gain than on other performance i n d i c a t o r s such as days to market. The b e t t e r r a t e s of gain i n d i c a t e d with the higher p r o t e i n d i e t s was an expected r e s u l t . The analysed p r o t e i n of d i e t s 3 and 4 were 14.7% and 14.6% i n s t e a d of the c a l c u l a t e d 15.5% and 14.5% which could e x p l a i n the s i m i l a r performance between those two d i e t s . PIG GROWTH MODEL page 106 V I I I MODEL VERIFICATION DISCUSSION F i g u r e 13 demonstrates the growth curves developed f o r the four d i e t s u s i n g the weekly p i g weights. The growth curves tended to improve as d i e t p r o t e i n i n c r e a s e d . These curves are the b a s i s f o r a comparison between model-derived p r e d i c t i o n s of performance and those observed on t r i a l . Simple ' t ' t e s t s are performed to determine i f observed performance i s s t a t i s t i c a l l y d i f f e r e n t from performance p r e d i c t e d by the model. Feed intake a l s o v a r i e d between d i e t s on t r i a l . A tendency f o r a h i g h e r intake with i n c r e a s e d p r o t e i n i s demonstrated by F i g u r e 14, although t h i s could be a random e f f e c t r e s u l t i n g from the low numbers of p i g s on each d i e t . Ad l i b i t u m feed intake i s b e l i e v e d to be p r i m a r i l y c o n t r o l l e d by the energy c o n c e n t r a t i o n of the d i e t (Martin et a l . , 1989). A l l four d i e t s had very s i m i l a r d i g e s t i b l e energy c o n c e n t r a t i o n s (estimated at 3100 k c a l / k g u s i n g NRC (1988) values) although an i n c r e a s e i n the l e v e l of soybean meal would give a s l i g h t advantage to the higher p r o t e i n d i e t s . The constant d i e t a r y energy should y i e l d feed i n t a k e s which are expected to show l i t t l e v a r i a t i o n between d i e t s . Feed intake data were pooled ( i . e . barrows and g i l t s ) a c r o s s d i e t s to give a b e t t e r estimate of feed i n t a k e F i g u r e 13: Growth Curves Developed by Weekly P i g Heights on the Four T e s t D i e t s page 1 0 8 F e e d I n t a k e ( k g s ) PIG GROWTH MODEL page 109 due to i n c r e a s e d numbers of p i g s represented. The pooled data were used to estimate feed intake i n the growth model. Table 21 compares model p r e d i c t e d feed intake and days to market with feed intake and days to market obtained. A ' t ' t e s t was used f o r s t a t i s t i c a l s i g n i f i c a n c e . F i g u r e 15 and 16 are used to g r a p h i c a l l y compare age and feed useage. The v a r i a t i o n seen i n the comparison between p r e d i c t e d and a c t u a l feed intake can be a t t r i b u t e d to a number of the assumptions which were made. The feed i n t a k e used i n the model was not the ad l i b i t u m feed intake generated by the model i t s e l f but the average feed intake observed across the f o u r d i e t s . T h i s means t h a t d i f f e r e n c e s between the feed i n t a k e s of the v a r i o u s d i e t s were not accounted f o r by the model. The feed intake used when mode l l i n g was a l s o skewed to b e t t e r r e p r e s e n t a normal feed intake by i g n o r i n g the r e d u c t i o n i n i n t a k e seen on the f i r s t week of the t r i a l . The ad l i b i t u m feed intake generated by the model was not used because i t overestimated intake as shown e a r l i e r ( F i gure 11). The observed decrease i n feed i n t a k e , when compared to modelled i n t a k e , probably r e l a t e s to the adverse e f f e c t of disease s t a t u s and d a i l y environment, n e i t h e r of which can be e a s i l y modelled. The feed intake generated i n the study may not have been t r u l y ad l i b i t u m due to Table 21 Compor-ison o f Model P r e d i c t i o n and the Actual Performance f o r Days t o Market and Feed Useage Cl<g5. Data Represents Combined Data f o r Males and Females. Treatment 1 n 1 T r i a l 1 Mean 1 Days 1 Model 1 Mean 1 Days IS 11 i g . d i f f . 1 p<O.OS = 1 1.699 1 n 1 T r i a l 1 Mean 1 Feed Ckg) 1 Model Mean Feed Ckg) ISig. d i f f . It p<0.05 1 1.812 1 1 It = O.176 1 1 11 = 3. 15 Diet 1 1 70 1 16S.03 1 166.2 i N. S. 1 lO 1 21-4.83 221 . 7 [ S.D. I 1 It = 0.226 1 1 It — 1.705 Diet 2 1 ?o 1 163.28 1 168.6 It N. S. 1 •.615 1 lO 1 220.64 [ 229. 3 11 N.S. 1.64 Diet 3 1 TO 1 169.05 1 170.0 11 _ N.S. 1 0.603 1 lO 1 222.89 233. l It N.S. 2.40 Diet 1 1 1 171.57 1 170-6 j N.S- 1 lO 1 2*14.31 ! 231. 7 j S. D. Figure 15- Comparison of Feed Useage Model Prediction vs. Trial Results 260 I Diet 1 Diet 2 Diet 3 Diet 4 %gx3 Trial Results Model Prediction Figure 16: Comparison of Age Model Prediction vs. Trial Results Diet 1 Diet 2 Diet 3 Diet 4 Trial Results Model Prediction PIG GROWTH MODEL page 113 d i f f i c u l t i e s a s s o c i a t e d with feed d i s p e n s i n g . In an attempt to minimize feed wastage, the amount added to the trough twice each day was probably below t h a t which would have been achieved with c l o s e r o b s e r v a t i o n . Feed intake s t u d i e s (unpublished) c a r r i e d out i n the f i e l d by the author, with high h e a l t h breeding herds, have shown e x c e l l e n t c o r r e l a t i o n with model p r e d i c t e d feed i n t a k e s . The e f f e c t of h e a l t h s t a t u s on feed i n t a k e , however, i s d i f f i c u l t to p r e d i c t . Page 2 of Appendix 2 (feed intake adjustment area) has been added so t h a t feed i n t a k e s can be adjusted. F i e l d s t u d i e s w i l l be continued i n order to attempt to l i n k a feed intake r e s t r i c t i o n with lung scores obtained through the B.C. P r o v i n c i a l Herd Health Program. Lung scores are t e s t s c a r r i e d out by v e t e r i n a r i a n s at the s l a u g h t e r p l a n t to measure the extent of pneumonic l e s i o n s on the lung. A c o r r e l a t i o n between lung scores and an expected decrease i n feed i n t a k e has been attempted by v e t e r i n a r i a n s with the P r o v i n c i a l Herd Health Program as w e l l as by a N a t i o n a l survey of lung scores c a r r i e d out by Elanco (a d i v i s i o n of E l i L i l y ) . S t u d i e s ( T i e l e n , 1987) are c o n t i n u i n g i n an attempt to e s t a b l i s h b e t t e r c o r r e l a t i o n s between lung scores and feed i n t a k e r e d u c t i o n s . PIG GROWTH MODEL page 114 IX CONCLUSION In t e g r a t e d models have been developed f o r swine by a number of s c i e n t i s t s eg. Whittemore (1976) and Black et a l . (1986). Aspects of the swine i n d u s t r y i n western Canada make a model unique to western Canadian c o n d i t i o n s u s e f u l . The p r o j e c t undertaken i n t h i s t h e s i s was an attempt to b u i l d a model to simulate growth between 20 and 100 kgs l i v e weight, f o r pi g s grown i n western Canada. The western Canadian nature of the model i s important because of d i e t a r y , g e n e t i c and grading c o n d i t i o n s which d i f f e r from the r e s t of North America. Model v a l i d a t i o n i s an important p a r t of model development and a study was undertaken to t e s t the p i g growth model which was developed. The model v a l i d a t i o n study i n d i c a t e s t h a t the t h e s i s model i s capable of a c c u r a t e l y p r e d i c t i n g growth between 20 and 100 kgs but i s not capable of a c c u r a t e l y p r e d i c t i n g feed intake (see f i g u r e 11) as i n d i c a t e d by the s e r i e s of % t ' t e s t s . The accurate growth p r e d i c t i o n , without an accurate feed i n t a k e p r e d i c t i o n , i s an a t t r i b u t e of a model which uses p r o t e i n d e p o s i t i o n as the key to growth. As long as feed i n t a k e i s s l i g h t l y o v e r p r e d i c t e d , the model w i l l f u n c t i o n a c c u r a t e l y as the excess p r o t e i n intake i s simply PIG GROWTH MODEL page 115 deaminated and excreted or turned i n t o f a t (an i n e f f i c i e n t p r o c e s s ) . T h i s model b i a s i s probably b i o l o g i c a l l y d e s c r i p t i v e as the same c h a r a c t e r i s t i c s would be expected i n a l i v e animal. The o v e r e s t i m a t i o n of feed intake does, however, e f f e c t model economics. The p e r i o d of growth between 20 and 100 kgs l i v e weight was chosen f o r modelling because the growth of the p i g i s con s i d e r e d to be most constant d u r i n g t h a t p e r i o d . The p e r i o d between b i r t h and 20 kgs i s a d i f f i c u l t p e r i o d to model because growth can be a c c e l e r a t e d and slowed q u i c k l y and i s very s u s c e p t i b l e to environmental e f f e c t s . The p r e d i c t i o n s of the Whittemore model are i n c l o s e agreement with experimental r e s u l t s f o r pi g s over 20 kgs (Whittemore, 1976), but have not f u n c t i o n e d w e l l f o r e a r l y weaned p i g s (from 12 to 20 kgs). The i n t e g r a t e d models are p r i m a r i l y concerned with p r o t e i n and l i p i d a c c r e t i o n and take i n t o account the p i g ' s c r i t i c a l temperature when c a l c u l a t i n g energy use during c o l d c o n d i t i o n s . The heat t r a n s f e r model i n c o r p o r a t e d i n t o the c u r r e n t growth model was developed by Bruce and C l a r k (1979). A new r e v i s i o n to the Whittemore model has been developed f o r pigs from 5 to 25 kgs body weight (Jackobson et a l . , 1989) by r e p l a c i n g the environmental components with a heat t r a n s f e r model. The heat t r a n s f e r model p a r t i t i o n s l a t e n t heat l o s s between the PIG GROWTH MODEL page 116 s k i n and lungs, adding a thermal r e s i s t a n c e f o r h a i r coat, and i n c r e a s i n g t i s s u e thermal r e s i s t a n c e . The r e v i s e d model has proven to c o r r e l a t e w e l l with t r i a l data of p i g l e t growth and heat output. The growth model developed i n t h i s t h e s i s c o u l d be r e f i n e d with the Jackobson et a l . (1989) m o d i f i c a t i o n and reworked to r e p r e s e n t p i g s from 5 kgs to 100 kgs l i v e weight. "An animal w i l l move, over time, towards a f i n a l e q u i l i b r i u m s t a t e , p r o v i d i n g t h a t i t has the means of doing so" (Emmans and Oldham, 1988). The e q u i l i b r i u m s t a t e adds a new dimension to animal models because growth i s o b v i o u s l y not the only c o n s i d e r a t i o n f o r models of animals at m a t u r i t y . Sow models o f f e r i n t e r e s t i n g parameters, such as milk p r o d u c t i o n and p i g l e t p r o d u c t i o n , to add to a model. A sow model has been attempted by Black et a l . (1986) as w e l l as by P e t t i g r e w et a l . ( 1 9 8 8 ) . The importance of m o d e l l i n g l a c t a t i n g sows i s paramount because i t may a i d i n the understanding of the p h y s i o l o g i c a l connections between d i e t and r e p r o d u c t i v e performance. The development of these complex models i s the obvious d i r e c t i o n f o r the f u t u r e with the growth models developed to date c o n t r i b u t i n g as components. The o b j e c t i v e s of model development have been d i s c u s s e d by Moughan and Verstegen (1988) and i n c l u d e the f o l l o w i n g : PIG GROWTH MODEL page 117 (1) To allow an economic a n a l y s i s of a l t e r n a t i v e f e e d i n g regimes f o r growing p i g s . (2) To allow comparisons of a c t u a l l y recorded on-farm p i g growth performance with ' p o t e n t i a l ' performance to i n d i c a t e the extent of management/pig h e a l t h problems. (3) To demonstrate the r e l a t i v e economic consequences of adopting a l t e r n a t i v e farm-management s t r a t e g i e s . (4) To a i d c a l c u l a t i o n of the r e l a t i v e economic values of u n i t improvement i n g e n e t i c s e l e c t i o n t r a i t s . (5) To provide i n f o r m a t i o n on the p h y s i o l o g i c a l consequences of g e n e t i c improvement and to a f f o r d a n a l y s i s of the e f f e c t s on animal performance from g e n e t i c improvement or e x t e r n a l manipulation of b a s i c p h y s i o l o g i c a l t r a i t s . (6) To a i d i n the design and i n t e r p r e t a t i o n of n u t r i t i o n a l experiments. (7) To demonstrate the p r i n c i p l e s of n u t r i e n t u t i l i z a t i o n and animal growth i n the t e a c h i n g of n u t r i t i o n . (8) To i d e n t i f y areas w i t h i n the growth process where t h e o r e t i c a l / e m p i r i c a l i n f o r m a t i o n i s l a c k i n g - - i . e . to provide a b l u e p r i n t f o r f u t u r e r e s e a r c h . The u s e f u l n e s s of growth models f o r p i g s w i l l probably l i e i n the areas o u t l i n e d by Moughan and Verstegen (1988) above. Growth models should never a c t u a l l y be c o n s i d e r e d f i n i s h e d because, at best, they are simply an ordered c o l l e c t i o n of the r e s e a r c h t h a t e x i s t s to date. As b e t t e r understandings of the u n d e r l y i n g chemistry of growth becomes a v a i l a b l e , models should be updated to recognize the new understanding. PIG GROWTH MODEL page 11B FOOT NOTES -'•Lotus 123, c o p y r i g h t 1983, 1986, Lotus Development C o r p o r a t i o n . 2 O p t i m a l S o l u t i o n s , c o p y r i g h t 1987, E n f i n Software C o r p o r a t i o n . •^Optimal S o l u t i o n s , c o p y r i g h t 1987, E n f i n Software C o r p o r a t i o n . ^throughout the t h e s i s , B.W. represents body weight i n kgs. 5These values are ap p r o p r i a t e f o r Large White and Landrace breeds, and f o r t h e i r c r o s s e s . Values f o r the b l o c k i e r breeds and f o r American breeds are l i k e l y to be higher. 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The energy c o s t of f a t and p r o t e i n d e p o s i t i o n i n the r a t . B r i t i s h J o u r n a l of N u t r i t i o n , 37, pp. 355 - 363. S h i e l d s , R.G., Mahan, D.C. and Graham, P.L. 1983. Changes i n swine body composition from b i r t h to 145 kg. J o u r n a l of Animal Science, 57, pp. 42. Stant, E.G. J r , M a r t i n , T.G., Judge, M.D., and H a r r i n g t o n , R.B. 1968. J o u r n a l of Animal Sci e n c e , 27, pp. 636 . Stombaugh, D.P. and Oko, A.. 1980. S i m u l a t i o n of n u t r i t i o n a l - e n v i r o n m e n t a l i n t e r a c t i o n s i n growing swine, In: 'Energy Metabolism' (ed. Mount, L.E.), Butterworths, London, pp. 209-215. Talpaz, H. 1986. Dynamic O p t i m i z a t i o n Model f o r Feeding of B r o i l e r s . A g r i c u l t u r a l Systems, 20, pp. 121-132. Tess, M.W. 1981. Simulated e f f e c t s of g e n e t i c change upon l i f e - c y c l e p r o d u c t i o n e f f i c i e n c y i n swine and the e f f e c t s of body composition upon energy u t i l i z a t i o n i n the growing p i g . Ph.D. t h e s i s , U n i v e r s i t y of Nebraska, Nebraska, USA, 315 pp. Tess, M.W., D i c e r s o n , G.E., Nienaber, J.A. and F e r r e l l , C.L. 1986. Growth development and body composition i n three g e n e t i c stocks of swine. J o u r n a l of Animal Science, 62, pp. 968. PIG GROWTH MODEL page 124 Throbek, G. 1975. Stu d i e s on energy metabolism i n growing p i g s . B e r e t n i n g f r a statens Husdyrbrugs f o r s o g , 424, Coppenhagen (copy i s i n E n g l i s h ) . T i e l e n , M.J.M. 1987. R e p i r a t o r y d i s e a s e s i n p i g s : i n c i d e n c e , economic l o s s e s and pr e v e n t i o n i n the Netherlands. In Energy Metabolism i n Farm Animals (Ed. Verstegen, M.W.A. and Henken, A.M.), Martinus N i j h o f f P u b l i s h e r s , pp. 321. Van Es, A.J.H. 1980. Energy c o s t of p r o t e i n d e p o s i t i o n , In 'P r o t e i n D e p o s i t i o n i n Animals', (ed P.J. B u t t e r y and D.B. Lindsay, Butterworths, London. Versetgen, M.W.A. 1971. In f l u e n c e of environmental temperature on energy metabolism of growing p i g s housed i n d i v i d u a l l y and i n groups. Meded. LandbHoogesch. Wageningen, No. 2. Walpole, R.E. 1977. I n t r o d u c t i o n to S t a t i s t i c s (second e d i t i o n ) . MacMillan P u b l i s h e r s , New York. pp. 275. Walpole, R.E. 1982. I n t r o d u c t i o n to S t a t i s t i c s ( t h i r d e d i t i o n ) . Macmillan P u b l i s h e r s , New York. pp. 521. Whittemore, C.T. and Fawcett, R.. 1976. T h e o r e t i c a l aspects of a f l e x i b l e model to simulate p r o t e i n and l i p i d growth i n p i g s . Animal P r o d u c t i o n , 22, pp. 87-96. Whittmore, C.T.. 1976. A study of growth responses to n u t r i e n t i n p u t s by modelling. Proceedings of the N u t r i t i o n S o c i e t y , 35, pp. 383-391. Whittemore, C.T. and E l s l e y , F.W.H. 1979. ' P r a c t i c a l P i g N u t r i t i o n ' , Farming Press L t d , S u f f o l k , pp. 50. Whittemore, C.T. 1983. Development of recommended energy and p r o t e i n allowances f o r growing p i g s . A g r i c u l t u r a l Systems I I , pp. 159 - 186. Whittemore, C.T.. 1987. Elements of P i g Science. Longman S c i e n t i f i c and T e c h n i c a l , Essex, England, pp. 140-175. PIG GROWTH MODEL page 125 Wilson, B.J.. 1977. Growth curves: T h e i r a n a l y s i s and use, In; 'Growth and P o u l t r y Meat P r o d u c t i o n ' (ed. Boorman, K.N. and Wilson, B . J . ) . B r i t i s h P o u l t r y Science L t d , Edinburgh, pp. 89-115. Windsor, C P . 1932. The Gompertz curve as a growth curve. Proceedings of the N a t i o n a l Academy of Science, 18, pp. 1 - 8. Wood, A.J. and Groves, T.D.D.. 1965. Body composition s t u d i e s on the s u c k l i n g p i g . 1. Moisture, c h e m i c a l f a t , t o t a l p r o t e i n and t o t a l ash i n r e l a t i o n to age and body weight. Canadian J o u r n a l of Animal Science, 45, pp. 8-13. PIG GROWTH MODEL page 126 Appendix 1 Key f o r Terms Used i n the Th e s i s a = E f f i c i e n c y f a c t o r by which p r o t e i n d e p o s i t i o n i s decreased as P r A i s approached (Whittemore, 1983) a2 = ARC parameter used to d e s c r i b e i n e f f i c i e n c y i n the c a l c u l a t i o n of IPm A = Mature body weight used i n Gompertz f u n c t i o n (kg) aE = Constant f o r c a l c u l a t i o n of p o t e n t i a l energy gain aN = Constant f o r c a l c u l a t i o n of p o t e n t i a l body n i t r o g e n gain Ao = Empty body ash (kg) At = T o t a l c a r c a s s ash a t 100 kg market weight AT = T o t a l body ash at m a t u r i t y (kg) b = Rate constant used i n Gompertz f u n c t i o n B.V. = B i o l o g i c a l value i s the p r o p o r t i o n of absorbed n i t r o g e n t h a t i s r e t a i n e d by the body B.W. = Body weight (kg) D = D i g e s t i b l i t y of a f e e d s t u f f (estimate) D.C.P.= D i g e s t i b l e crude p r o t e i n (kg) DE = D i g e s t i b l e energy (MJ/kg) EAT = E f f e c t i v e ambient temperature (Bruce and C l a r k , 1979 ) E AB = Energy content of the body at m a t u r i t y (MJ/kg) EH1 = Energy c o s t of c o l d thermogenesis (MJ/kg) Em = Energy of maintenance (MJ) ELr = Energy c o s t of f a t growth (MJ/kg) Epf = P r o t e i n f r e e d i g e s t i b l e energy (MJ/kg) PIG GROWTH MODEL page 127 Epr = Energy c o s t of p r o t e i n r e t e n t i o n (MJ/day) G AEB = P o t e n t i a l energy deposited i n the body (MJ/day) GANB = P o t e n t i a l n i t r o g e n gain i n the body (g/day) H = Heat output from the body (KJ/kg A0.75 ) IPm = I d e a l p r o t e i n of maintenance (kg) IPr = I d e a l p r o t e i n r e t a i n e d (kg) IPt = T o t a l i d e a l p r o t e i n i n g e s t e d (kg) k = Constant used i n Gompertz f u n c t i o n kE = Constant f o r rate of gain of body energy (MJ/day/W AaE) kN = Constant f o r rate of gain of body n i t r o g e n (kg/day/W AaE) Lo = empty body l i p i d (kg) Lr = L i p i d r e t a i n e d (kg) Lt = T o t a l c a r c a s s l i p i d at 100 kg market weight (kg) LT = T o t a l body l i p i d at mat u r i t y (kg) MEt = E f f e c t i v e m e t a b o l i z a b l e energy (MJ) NB = Weight of body n i t r o g e n at weight W (kg) Pm = P r o t e i n deaminated (kg) Po = Empty body p r o t e i n (kg) Pr = P r o t e i n r e t a i n e d (kg) P r A = Maximum p r o t e i n r e t e n t i o n (kg) PRTPX = Ewan's (personal communication) equation r e l a t i n g p r o t e i n r e t e n t i o n to p r o t e i n s y n t h e s i s ( p r o t e i n turnover) (kg/day) Pt = T o t a l p r o t e i n mass i n the body estimate (kg) PIG GROWTH MODEL page 128 P t A = Mature t o t a l p r o t e i n mass estimate (kg) PT = T o t a l body p r o t e i n at 100 kg market weight (kg) Px = P r o t e i n turnover (kg/day) q = M e t a b o l i c age (day/kg A0.27) as a f r a c t i o n of mature age c a l c u l a t e d as q = ( t - 3.5)/A A0.27 Qd = Energy d e r i v e d from p r o t e i n deaminated (MJ/kg) t = time t ' = time v a r i a b l e used i n Gompertz f u n c t i o n T = Ambient temperature (degrees C) Tc = Lower c r i t i c a l temperature (degrees C) To = EAT a s s o c i a t e d c r i t i c a l temperature (degrees C) u = Degree of ma t u r i t y (body weight/mature weight) u l = M a t u r i t y a t maximum growth rate V = Ewan's (personal communication) estimate of b i o l o g i c a l value of a f e e d s t u f f Ve = Rate of a i r movement and degree of i n s u l a t i o n adjustment parameter VI = F l o o r type i n l y i n g area adjustment parameter W = Body weight (Black, 1986) (kg) We = Empty body weight at 100 kg market weight (kg) Yo = Empty body water (kg) Yt = Carcass water content at 100 kg market weight (kg) YT = T o t a l body water at ma t u r i t y (kg) page 129 APENDIX 2 EXAMPLE MODEL INPUT-OUTPUT Twelve pages of model i n p u t and output f o r the western Canadian p i g model Page 1 A M O D E L T O PREDICT PIG GROWTH version 1 (89) Developed by David L. Dyble U.B.C. Department of Animal Science Graduate Student 42208785 East Chilliwack Agricultural Cooperative m s e s t s c s a e s B t a i s a K S S e s a s m o s s e s ; a s s s e a s s s s a s s s s s S S C S S Z S S S B E S C S C S B B C S E S E S C S E to rmxfef ad lib. intake, an estlrriated rate of growth to necessary. The Ave curves developed below represent growth rates al 147,188,160, 182,201,220 days m market. z o U J GOMPERTZ GROWTH 0 I 28 I 55 I 84 I 112 I 140 I 168 I 196 I 224 14 42 70 98 126 154 182 210 ACE (DAYS) 0 147 + 158 o 169 * 182 * 201 ' 2 2 0 164 * exp ( - 4.46 exp (-0.014 * (t))) k - In ((In (( B.W.)/A)) * (1/-B))/t BOBBBBB E 3 S 3 E 5 3 3 S Z S 5 E S 5 ENTER CHOICE 168.38 S 3 S 3 C S C S S 3 S B S S AGE 0 1,90 7 2.80 14 4.00 21 5.S3 2a 35 9.74 42 12,46 49 16.61 56 10,1? 63 23.13 70 27.44 77 l l l i i i i c i i l i 84 37.00 91 42,14 98 47.46 105 52.88 112 58.37 110 126 3fc37 133 74.79 140 mM 147 86.27 154 90,20 161 96.12 168 09,76 175 104.18 182 i 108,30 189 112.39 196 116.10 203 l i i i i l l l i 210 123,06 217 126.18 224 120.10 Page 2 FEED INTAKE ADJUSTMENT AREA Feed intake can be generated by the model based on an ad lib prediction or can be generated where know intake exist. The effect of disease is often on feed intake and this can be added to the model through reductions in ad lib intake or calculated known intakes WHERE FEED INTAKE IS KNOWN, THIS DATA CAN BE ENTERED DIRECTLY INK COLUMN I BE SURE NOT TO SAVE AS YOU WILL LOSE THE EQUATIONS. TO ADLIB FEED % FEED INTAKE DETACH INTAKE (kg/d) REDUCTION OR ENTER MODEL DERIVED INCREASE 0 ASSOCIATED TO DIRECT FEED WITH INVOKE INTAKE ENTERB PNEUMONIA ENTER DAYS HERE (kg/d) OR OTHER 1 49 0.917 3 0 56 1.089 3 0 63 1.267 3 0 70 1.300 3 0 77 1.520 3 0 84 1.750 3 0 91 1.960 3 0 98 2.170 3 0 105 2.360 5 0 112 2.480 5 0 119 2.590 10 0 126 2.700 10 llilllllls 133 2.750 10 0 140 2.780 10 0 147 2.750 10 0 154 2.720 10 0 161 2.700 10 0 168 2.680 10 0 175 2.680 10 o 182 2.680 10 0 189 2.680 10 0 196 2.680 10 0 203 2.680 10 0 210 2.680 10 0 217 2.680 10 0 224 2.680 10 0! F E E D SECTION DIGESTIBILITY: Calculated from tables and exoressed as a decimal CRUDE PROTEIN: Expressed as grams per kilo of feed. BIOLOG. VALUE: Calculated from ideal protein, expressed as a decimal ENERGY (D.E.): Mega Joules digestible energy per kilo (kcals calc'd) DRY MATTER : Percent dry matter expressed as a decimal STORE PIGMODL3 Digest CP BV DE KCAL DM AGE(days) n 7 14 21 28 35 42 49 0.8 214.7 0.782 14.37 3433 0.8801 56 0.8 214.7 0.782 14.37 3433 0.8801 63 0.8 214.7 0.782 14.37 3433 0.8801 70 0.76 151 0.71 12.98 3101 0.895 77 0.76 151 0.71 12.98 3101 0.895 84 0.76 151 0.71 12.98 3101 0.895 91 0.76 151 0.71 12.98 3101 0.895 98 0.76 151 0.71 12.98 3101 0.895 105 0.76 151 0.71 12.98 3101 0.895 112 0.76 151 0.71 12.98 3101 0.895 119 0.76 151 0.71 12.98 3101 0.895 126 0.76 151 0.71 12.98 3101 0.895 133 0.76 151 0.71 12.98 3101 0.895 140 0.76 151 0.71 12.98 3101 0.895 147 0.76 151 0.71 12.98 3101 0.895 154 0.76 151 0.71 12.98 3101 0.895 161 0.76 151 0.71 12.98 3101 0.895 168 0.76 151 0.71 12.98 3101 0.895 175 0.76 151 0.71 12.98 3101 0.895 182 0.76 151 0.71 12.98 3101 0.895 189 0.76 151 0.71 12.98 3101 0.895 196 0.76 151 0.71 12.98 3101 0.895 203 0.76 151 0.71 12.98 3101 0.895 210 0.76 151 0.71 12.98 3101 0.895 217 0.76 151 0.71 12.98 3101 0.895 224 0.76 151 0.71 12 .98 3101 0 .805 Page 4 GENETICS SECTION Black et al, 1986 Values for maximum protein deposition are outlined in the table below: Boar Gilt Castrate ENTER CHOICE Pigs from large Commercial Piggeries (aE <= 0.6, aN = 0.5) aN 0.2 kN (g/dayAATaN) 0.0042 0.0042 0.0038 0.0119 N~B(kg) 5.76 4.65 4.65 4.2 Pigs from small Commercial Piggeries (aE = 0.4, aN = 0.2) kN (g/day/V\TaN) 0.0119 0.0119 0.0108 N'B (kg) 4.2 3.4 3.4 A minimum fat to protein deposition must be established to represent the genetic material to be modelled. The method of feeding has an effect on the fat to protein deposition. The ratio should correspond to the expected index. The data of Henderson, Tuilis, Whittemore and Black has been used to generate the following chart. Ad Ub feeding Commercial pigs 2.1:1 Improved pigs 1.5:1  ENTER CHOICE 2.1 Generous but restricted Commercial pigs 1,6:1 Improved pigs 1.6:1 Restricted feeding Commercial pigs 1.03:1 Improved pigs 0.89:1 ,**Note that the choice is the first number of the ratio E N V I R O N M E N T S E C T I O N Page 5 VE Insulated, not draughty iiliiiiii Not insulated, not draughty iiiijip Insulated, slightly draughty l l l l l i l l Insulated, draughty Not insulated, draughty vt Deep straw bed llllllilil Shallow straw bed illjllii! No bedding on insulated floors Iltlllll Slatted floors with no draughts 1 No bedding on uninsulated floors lllllllil Slatted floors with draughts under lllllliil No bedding on wet, uninsulated floor lillliliil ENTER CHOICE VE 0.9 VL 0.9 Effootiv© Ambiont T©mp©ratur© EAT Airmovement M/Sec EAT C EAT C 0 0 Straw bed 4 0.2 -4 Concrete slat -5 0.5 -7 Wet surface -5 to-10 1.5 -10 (Sum a choice) Enter the temperature average for the modelled period ENTER CHOICE Pigs per pen greater than 5 18 ENTER -CHOICE If pelleted feed then use 0.031 0.031 Space per pig when less than 50 kgs body weight (M~2) 0.929 Space per pig greater than 50 kgs body weight (M'2) 0.929 The NRC equation used to derive feed intake are based on the assumption that gilts and barrows are mixed 50:50. If not 50:50. deviations are calculated as follows: 60:40 mix (barrows) would require the number +0.2 because 10>50 is 20% or 0.2. All barrows or gilts is indicated by +/- 1.  ENTER CHOICE M O D E L OUTPUT SECTION Page 6 FT Total body protein (kg) LT Total body lipid (kg) AT Total body ash (kg) YT Total body water (kg) STORE PIGMODL1 TOTAL We Empty body weight (kg) (-gut contents) TOTAL W Total body weight (kg) AGE(days) 0 7 14 21 28 35 West PT LT AT YT GROWTH COMPOSITION TOTAL We TOTAL i l l l l 49 15.61 2.19 1.65 0.43 9.59 13.86 llllliSI 56 19.17 3.04 3.43 0.60 12.66 19.73 20.72 63 23.13 3.89 5.22 0.81 15.66 25.58 26.86 70 27.44 4.49 6.49 0.93 17.71 29.62 31.10 77 32.08 5.20 7.97 1.08 20.06 34.31 36.02 84 37.00 6.01 9.67 1.24 22.71 39.63 41.62 91 42.14 6.84 11.42 1.43 25.37 45.06 i i i i l t l l i 9 8 47.4B 7.66 13.13 1.63 37.93 50.36 l l l l i l l l l 105 52.88 8.45 14.80 1.85 30.40 55.51 58.29 112 58.37 9.23 16.43 2.08 32.76 60.51 63.53 1 1 9 63.89 9.98 18.01 2.32 35.03 05.34 0 8 . 0 1 126 69.37 10.71 19.54 2.57 37.21 70.02 73.52 133 74.79 11.41 21.02 2.81 39.29 74.53 l l l l l l l l 140 80.10 12.09 22.44 3.06 41.28 78.87 &ZM 147 85.27 12.75 23.82 3.30 43.18 83.04 87.10 154 90.29 13.38 25.14 3.53 45.00 87.05 O1.40 161 95.12 13.98 26.41 3.77 46.74 90.89 95.44 168 99.75 14.56 27.63 3.99 48.39 94.58 90.31 175 104.18 15.12 28.80 4.21 49.97 98.11 103.02 182 108.39 15.66 29.93 4.43 51.48 101.50 108.57 189 112.39 16.17 31.00 4.65 52.92 104.74 109.97 196 116.16 16.66 32.03 4.87 54.28 107.84 113,23 203 119.71 17.13 33.01 5.08 55.59 110.80 116.34 210 123.05 17.57 33.95 5.29 56.83 113.64 119,32 217 126.18 18.00 34.85 5.49 58.01 116.35 122.17 224 129.10 18.41 35.71 5.70 69.13 118.96 ••••••• U S * * * M O D E L OUTPUT - B A C K F A T Page 7 \ The backfat can be ascertained from the chart or is derived from the age be ow 100 kgs. BACKFAT AT AGE TO <102 KGS 28.76 INDEX 107 Backfat adjusted normal Yield Class Guide Backfat distribution AGE(days) 0 7 14 21 28 35 INDEX INDEX 42 Yield Class WT (KG) WT (KG) 49 2.52 FROM mm TO mm 96 -102.3 1022.4-109 56 4.31 4.32 1 19.1434 <19.1434 114 113 63 6.13 6.08 2 19.1935 21.6591 113 112 70 7.40 7.43 3 21.6592 24.1748 112 111 77 8.90 8.92 4 24.1749 26.6906 110 109 84 10.62 10.62 5 26.6907 29.2063 108 107 91 12.38 12.38 6 29.2064 31.722 107 106 98 14.11 14.11 7 31.7221 34.2377 105 104 105 15.80 15.79 8 34.2378 36.7534 103 102 112 17.44 17.44 9 36.7535 39.269 102 101 119 19.03 19.03 10 39.2691 41.7847 100 99 126 20.58 20.57 11 41.7848 44.3003 98 97 133 22.07 22.06 12 44.3004 46.816 97 , 9 6 140 23.51 23.50 13 46.8161 49.3316 95 94 147 24.90 24.89 14 49.3317 51.8473 91 90 154 26.23 26.23 15 51.8474 54.363 89 88 161 27.52 27.51 168 28.75 28.74 175 29.93 29.93 182 31.06 31.06 189 32.15 32.14 196 33.19 33.18 203 34.18 34.18 210 35.13 35.13 217 36.04 36.03 224 36.90 M O D E L OUTPUT - F E E D Page 8 | Feed used per week per pig Feed cost expressed as dollars per kilo Cummuiated feed use per pig Feed cost in dollars per pig per week Cummuiated feed cost per pig FEED COST $63.41 FEED USEj 269.38 KGS + WASTE 282.85 KGS j 593.89 LBS 623.58 LBS (KG) DAILY FEED DAYS F D / W K FD COST CUM FD/W W K F D $ CUM FD $ INTAKE 49 6.42 0.390 6.42 2.50 2.50 0.92 56 7.63 0.390 14.05 2.97 5.48 1.09 63 8.87 0.390 22.91 3.46 8.94 1.27 70 9.10 0.221 32.01 2.01 10.95 1.30 77 10.64 0.221 42.65 2.35 13.30 1.52 84 12.25 0.221 54.90 2.71 16.01 1.75 91 13.72 0.221 68.62 3.03 19.04 1.96 98 15.19 0.221 83.81 3.36 22.40 2.17 105 16.52 0.221 100.33 3.65 26.05 2.36 112 17.36 0.221 117.69 3.84 29.88 2.48 119 18.13 0.221 135.82 4.01 33.80 2.60 126 18.90 0.221 154.72 4.18 38.07 2.70 133 19.25 0.221 173.97 4.25 42.32 2.75 140 19.46 0.221 193.43 4.30 46.62 2.78 147 19.25 0.221 212.68 4.25 50.88 2.75 154 19.04 0.221 231.72 4.21 55.08 2.72 161 18.90 0.221 250.62 4.18 59.26 2.70 168 18.76 0.221 269.38 4.15 63.41 2.68 175 18.76 0.221 288.14 4.15 67.55 2.68 182 18.76 0.221 306.90 4.15 71.70 2.68 189 18.76 0.221 325.66 4.15 75.84 2.68 196 18.76 0.221 344.42 4.15 79.99 2.68 203 18.76 0.221 363.18 4.15 84.14 2.68 210 18.76 0.221 381.94 4.15 88.28 2.68 217 18.76 0.221 400.70 4.15 92.43 2.68 224 18.76 0.221 419.46 4.15 96.57 2.68 p a g e 138 Page 9 | MODEL OUTPUT - NRC PROTEIN AND AMINO ACID REQUIREMENTS Feed protein requirements derived from NRC equations (EWAN) Feed protein levels of diet Feed Lysine requirements derived from NRC equations (EWAN) Feed Tryptophan requirements derived from NRC equations (EWAN) Feed Threonine requirements derived from NRC equations (EWAN) FEED FEED FEED FEED FEED PROTEIN PROTEIN LYSINE TRYPTO. THREON. NRC DIET DAYS 49 0.177 0.2147 0.0089 0.00137 0.00548 56 0.168 0.2147 0.0089 0.00140 0.00561 63 0.161 0.2147 0.0087 0.00139 0.00556 70 0.173 0.151 0.0091 0.00147 0.00587 77 0.162 0.151 0.0084 0.00136 0.00545 84 0.153 0.151 0.0078 0.00128 0.00512 91 0.147 0.151 0.0075 0.00123 0.00491 98 0.143 0.151 0.0071 0.00118 0.00471 105 0.140 0.151 0.0069 0.00114 0.00457 112 0.141 0.151 0.0068 0.00114 0.00456 119 0.14Z 0.101 0 .0008 0.00114 0 .00400 126 0.143 0.151 0.0068 0.00113 0.00454 133 0.147 0.151 0.0068 0.00115 0.00461 140 0.151 0.151 0.0070 0.00118 0.00471 147 0.158 0.151 0.0072 0.00122 0.00490 154 0.165 0.151 0.0075 0.00127 0.00508 161 0.172 0.151 0.0077 0.00131 0.00524 168 0.178 0.151 0.0079 0.00135 0.00540 175 0.182 0.151 0.0081 0.00138 0.00551 182 0.187 0.151 0.0082 0.00140 0.00561 189 196 203 210 217 224 Page 10 MODEL REGRESSION SECTION USED TO ESTIMATE DAILY GAIN Polynomial regression analysis allows curves to be developed that represent model growth output which allows analysis of growth on any particular day. TO USE THIS SECTION, YOU MUST IMPLEMENT A MACRO CALLED ALT R AFTER EACH CHANGE TO THE MODEL. EQUATION USED T O REPRESENT GROWTH AT ANY POLYNOMIAL PARTICULAR DAY DAYS REGRESSION ENTER 49 14.60769 A G E (DAYS) WEIGHTOCG) 148 87.55472 56 20.27367 63 25.89259 70 31.45698 77 36.95935 84 42.39223 91 47.74814 98 53.01962 105 58.19917 112 63.27934 119 68.25263 126 73.11158 133 77.84871 140 82.45654 147 86.92760 154 91.25440 161 95.42948 168 99.44536 175 103.2945 182 106.9696 189 110.4630 196 113.7673 203 116.8750 210 119.7787 217 122.4708 224 124.9440 • PROTEIN AVAILABLE + PROTEIN RETAINED 0 DIG. CRUDE PROTEIN D PT + LT 0 AT A YT x We v Wt 

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