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Factors influencing the assessment of rate and feed efficiency of growth in Yorkshire swine : the influence… Waldern, Donald Ernest 1954

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FACTORS INFLUENCING THE ASSESSMENT OF RATE AND FEED EFFICIENCY OF GROWTH IN YORKSHIRE SWINE THE INFLUENCE OF ENERGY LIMITATIONS AND HYPOFERROUS ANEMIA ON PRE-WEANING AND POST-WEANING GROWTH RATE POST-WEANING GROWTH RATE AND EFFICIENCY OF FEED CONVERSION by DONALD ERNEST WALDERN A thesis Submitted i n P a r t i a l Fulfilment of the Requirements f o r the Degree of Master of Science i n Agriculture i n the Department of Animal Husbandry We accept th i s thesis as conforming to the standard required from candidates for the degree of MASTER OF SCIENCE IN AGRICULTURE Members of the Department of Animal Husbandry THE UNIVERSITY OF BRITISH COLUMBIA APRIL, 1954-ABSTRACT The present thesis i s a study of the factors that a f f e c t the assessment of rate and e f f i c i e n c y of gain i n Yorkshire swine i n the pre and post-weaning stages of growth. Calculations from metabolism data f o r growing swine and measurement of the milk production of Yorkshire sows were used to demonstrate the i n a b i l i t y of a sow to produce s u f f i c i e n t milk (energy) f o r her suckling young about 12 to 20 days post-farrowing. A well balanced high energy creep r a t i o n was used i n a commercial swine herd to overcome the energy debt to suckling p i g l e t s and provide for attainment of maximum growth, and hence, reduce the time required by them to reach 200 pounds. The a f f e c t of subnormal hemoglobin l e v e l s on pre-weaning growth rates and weaning weights of suckling p i g l e t s was i n v e s t i -gated. The need of a continuous supply of i r o n and energy (creep ration) for suckling p i g l e t s to produce normal hemoglobin l e v e l s and to permit them to grow at t h e i r genetic pot e n t i a l was demon-strated. Energy content of gain and resting energy metabolism data were used to calculate post-weaning feed requirements of four experimental l i t t e r s that were 12-^  percent inbred. The post-weaning growth studies show uniformity of l i t t e r averages f o r several economic characters of swine, but variations within l i t t e r s were high as shown by large standard deviations. The rela t i o n s h i p between post-weaning rate of gain, feed e f f i c i e n c y and dressed carcass i s discussed. The r e s u l t s demonstrate the p o s s i b i l i t y of rapidly im-proving rate and e f f i c i e n c y of gain i n swine i f s e l e c t i o n i s based on the performance of i n d i v i d u a l animals. ACKNOWLEDGMENT The writer wishes to thank Professor H.M. King, Head of the Department of Animal Husbandry, f o r providing f a c i l i t i e s to conduct part of the experimental work; Dr. A.J. Wood, Associate Professor i n the Department of Animal Husbandry, for his many he l p f u l suggestions, d i r e c t i o n and c r i t i c i s m s . The writer i s indebted to Dr. H.R. MacMillan f o r f i n a n c i a l assistance to undertake a program of swine research, and for permitting the use of his swine herd at Arrowsmith Farms fo r n u t r i t i o n studies. Special thanks are due Mr. B. Bailey, recent swine herdsman at Arrowsmith Farms, for his e f f o r t s and assistance i n the c o l l e c t i o n of experimental data at that farm. Thanks are also due to those who assisted i n the experimental work at the Animal N u t r i t i o n Laboratory, University of B r i t i s h Columbia and others for t h e i r f i n a n c i a l assistance. TABLE OF CONTENTS Page No. I . INTRODUCTION 1 I I . THE INFLUENCE OF ENERGY LIMITATIONS AND HYPO-FERROUS ANEMIA ON PRE-WEANING AND POST-WEAN-ING GROWTH RATE OF YORKSHIRE SWINE 7 A. Energy Limitations 7 1. Introduction 7 2. Review of Literature 9 (1) Milk Production by Sows 10 (2) Composition of Sows Milk 17 (3) Energy Requirements of Suckling P i g l e t s . . . . 19 (4) Relation of B i r t h Weight to Weaning Weights 20 3 . A Theoretical Calculation of Energy Production by the Sow, and Energy Requirements of the L i t t e r 23 (1) Milk Production of Experimental Sows 27 4. Experimental Procedure,.... 30 5. Results 31 6. Discussion 44 7. Summary and Conclusions...... 48 B. Hypoferrous Anemia. 50 1. Introduction 50 2. Review of Literature 53 3 . Experimental Procedure 57 4. Results 59 5. Discussion of Results 76 6. Summary and Conclusions 81 TABLE OF CONTENTS - Cont'd. Page No. I I I . POST-WEANING GROWTH RATE AND EFFICIENCY OF FEED CONVERSION OF YORKSHIRE SWINE. 83 1. Introduction 83 2. Review of Literature , 86 (1) Heredity and Selection 86 1. H e r i t a b i l i t y Estimates for Swine 86 2. The Effect of Selection i n Improving Carcass Charac-ters,Feed E f f i c i e n c y and Rate of Gain 89 3 . Recent H e r i t a b i l i t y Estim-ates of Certain Performance T r a i t s i n Canadian York-shire Swine 92 (2) Growth and Metabolism 100 1. A Mathematical Expression of Growth. • • 100 2. The Relationship of Metabol-i c Rate to Growth Rate 106 3 . Endocrine Secretions and Their Effect on Growth Rate. 107 4. Sex Difference arid Growth Rate 109 5. The Normal Growth Pattern of the Hog 109 (3) Carcass Composition 110 1. Carcass Composition i n Rela-t i o n to Body Gain 110 2. The Effect of Fat Content of the Diet on Carcass Composi-t i o n 113 (4) Feed U t i l i z a t i o n 115 1. Preliminary Investigations on Feed E f f i c i e n c y of York-shire Hogs 115 2. Method of Expressing Feed E f f i c i e n c y 116 3 . Inheritance as a Factors In-fluencing the E f f i c i e n c y of Food U t i l i z a t i o n 117 TABLE OF CONTENTS-Cont'd. Page No. 3 . Experimental Procedure , :.jL23. 4. Results 129 5. Discussion of Results 144 6. Summary and Conclusions 157 IV. GENERAL SUMMARY 162 V. APPENDICES 165 I . A Review of the Basic Facts of Blood Composition, Iron-Hemoglobin Relation-ships and Types of Anemia Affecting Pre and Post-Weaning Growth Rate i n Yorkshire Swine 165 II. A r i t h - l o e Plots of Weekly Weight Data of the 28 Experimental Pigs from B i r t h to 200 Pounds 173 I I I . The Calculation of Growth Constants or K Values of Yorkshire Hogs By Use of The Method of Least Squares for Smooth-ing Data. 174 IV. (a) Inbreeding of Experimental Pigs... 176 (b) Pedigree of Experimental Pigs 177 VI. BIBLIOGRAPHY 178 - 1 -I. INTRODUCTION In recent years theie has been a great demand for quantitative technical data on the e f f i c i e n c y of animals i n converting feed to body gain. A good method of assessing the feed e f f i c i e n c y of animals presents a problem fo r research workers because the basis of feed e f f i c i e n c y i s rate of growth and the composition of the gain, two items that are d i f f i c u l t to measure. Any factor a f f e c t i n g the rate of growth during the entire period from b i r t h up to the time the actual measurement of feed e f f i c i e n c y i s taken, w i l l e f f e c t the feed e f f i c i e n c y during the period i t i s measured. During the pre-weaning ex-istence of the pig, two factors are of c r i t i c a l concern to i t s growth and development. The f i r s t factor i s possibly an energy d e f i c i t . Even the casual observer of suckling p i g l e t s notes that at ten days to three weeks post-farrowing, suckling p i g l e t s appear t h i n , starry-coated and f a i l to grow. I f weekly weights are recorded, It i s noted that the p i g l e t s a c t u a l l y stop gaining between the second and fourth week post-farrowing. This i s believed to be caused by i n s u f f i c i e n t milk (Energy) production by the sow to meet the requirements of the suckling l i t t e r . The r e s u l t of an energy d e f i c i t would mean an average weaning weight fo r a l i t t e r of eight pigs of 28 pounds at eight weeks, a value close to the Canadian average. In contrast to t h i s , the genetic maximum weaning weight of suckling p i g l e t s i s probably more of the order of 45 pounds for a l i t t e r of eight i f n u t r i t i o n a l demands are supplied. The second c r i t i c a l factor a f f e c t i n g the pre-weaning growth rate of the suckling pig i s that of a subnormal hemoglobin - 2 -l e v e l , which arises from chronic i r o n deprivation. Sow's milk i s very low i n i r o n and since t h i s i s the only source available to suckling pigs unless otherwise supplemented, they develop an i r o n deficiency which manifests i t s e l f i n the form of hypoferrous anemia. A hemoglobin l e v e l of 6 to 9 grams of hemoglobin per 100 cubic centimeters of blood (6 to 9 grams per cent) for suckling p i g l e t s has been ,;be//evedi3 adequate to permit them to grow at a normal rate. The normal hemoglobin l e v e l of suckling p i g l e t s i s 12 to 14 grams per cent. I f a high-energy creep r a t i o n i s supplied to suckling pigs, then i t hardly seems possible that they can achieve an Individual weaning weight of 40 pounds or better i f hemoglobin lev e l s are 25 to 35 per cent below normal. During the period from b i r t h to weaning the suckling pig can gain at the average rate of 25 to 30 per cent of i t s body weight per week i f its n u t r i t i v e requirements are supplied. This rate i s double the average rate of the post-weaning period. This means that metabolic events are occurring twice as r a p i d l y before weaning af t e r weaning, therefore, abnormal n u t r i t i o n i n the pre-weaning stage of growth would probably a f f e c t ultimate development more than abnormal n u t r i t i o n i n the post-weaning period. The weight attained by a suckling p i g l e t at eight weeks w i l l considerably affect the weight i t attains at s i x months. A p i g l e t that weighs 45 pounds at eight weeks would be expected to weigh about 200 pounds at 160 days. This i s opposed to a p i g l e t that weighs 28 pounds at weaning at eight weeks and achieves 200 pounds by 190 days. The heavier weaning pig gained - 3 -17 pounds before weaning when i t required about 1.5 pounds of feed per pound of gain, while the l i g h t e r weaning pig gained the 17 pounds throughout the post-weaning period when i t required about 4 pounds of feed per pound of gain and hence needed nearly 3 0 days longer to reach a 200 pound market weight. Thus, the slower growing pig would need nearly 6 8 pounds of feed just to make up the difference i n gain. The method used to measure growth can have considerable effect on the results obtained and on the int e r p r e t a t i o n of r e s u l t s . The standard method of measuring rate of gain i s to calculate the change i n body weight over a s p e c i f i c i n t e r v a l of time. The standard method of expressing feed e f f i c i e n c y i s to measure the feed consumed over the same time i n t e r v a l that body gain was measured, then divide the t o t a l feed consumed by the t o t a l gain. The standard method of expressing growth has been replaced i n studies with small animals by methods u t i l i z i n g quantitative expressions for growth. The normal expression for rate of gain, the increase i n body weight per unit of time over a prolonged i n t e r v a l of time, i s not sound (Brody 1945). For, i n terms of the physiologist, the expression implies that there i s a d e f i n i t e relationship between rate of metabolism and chronological time. For example, the average d a i l y gain of a hog at a body weight of 80 pounds, then 6 0 days l a t e r at a weight of 160 pounds i s 1.4 pounds per day by the conventional method. But t h i s i s not reasonable because for every unit increase i n body weight there i s only a .7 increase i n basal metabolism (Brody 1945). As basal metabolic rate i s related to the active protoplasmic mass, one would then expect growth rate to be - 4 -related to the body mass available f o r active metabolism. This would suggest that the most accurate evaluation of body gain would be made i f growth measurements were taken against the body weight of the animal at the time of the measurement of the gain. P r a c t i c a l l y t h i s would seem quite impossible, but Brody (1945) has made use of the calculus to integrate the series of i n f i -n i t e l y small gains r e l a t i v e to the weight of the animal at the time the gains are made, and he has expressed the rate of growth as: K = In W2 - In w l f where K i s the Instantaneous t 2 - t ! Relative Growth rate, or percentage growth rate when mul t i p l i e d by 100. Ln w2 i s the natural logarithm of the body weight at time " t 2 n and Ln w^  i s the natural logarithm of the body weight at time " t ^ " . The expression implies that an a r i t h - l o g regression of body weight against time should y i e l d a l i n e a r r e l a t i o n s h i p i f the animal grows at a constant rate. The slope of the l i n e , which would be represented by K i n the equation, has the d e f i n i t e meaning of r e l a t i v e gain per unit of time at any selected body weight. Therefore, i f the growth data of any pig from b i r t h to 200 pounds i s regressed against time on an a r i t h - l o g g r i d , d e f i n i t e phases of l i n e a r i t y are obtained, and by use of the equation the growth constants are calculated. The growth constants of boar No. 204 and boar No. 205> as found i n Appendix I I , taken over the fourth phase of l i n e a r i t y , which i s between 80 and 140 pounds, shows boar No. 204 with a d a i l y percentage growth rate of 1.75> while boar No. 205 has a d a i l y percentage growth rate - 5 -of 1.43. Now a comparison of the two boars at an equal body-weight of 110 pounds, shows that boar No. 204 was gaining at 1 . 7 5 per cent x 110 » 1.91 pounds per day while boar No. 205 was gaining at 1.43 per cent x 110 = 1 .57 pounds per day. A difference of .34 pounds per day at equal body weight. The regression of weekly body weights of pigs against time on an ar i t h - l o g g r i d shows f i v e d i s t i n c t phases of l i n e a r i t y during the growing period, and that the growth constant for each phase i s reduced by one-half i n each succeeding stage of l i n e a r i t y . Similar results have been obtained by Williams (1952) who has plotted growth data on an a r i t h - l o g g r i d of Hereford beef c a t t l e , Wistar white r a t s , the Labrador r e t r i e v e r , and B l a c k t a i l deer and demonstrated the existence of d e f i n i t e phases of l i n e a r i t y i n the growth pattern. He has also calculated the.growth constants f o r the phases of l i n e a r i t y and discussed t h e i r significance. There are several factors that may affe c t the assessment of e f f i c i e n c y of gain of animals i n the post-weaning period of development. Growth rate and feed e f f i c i e n c y are dependent on the composition of the gain and hence feed e f f i c i e n c y i s related to the rate of gain. The method used to measure feed e f f i c i e n c y and the standardization of feeding procedures w i l l a ffect the degree of expression of feed e f f i c i e n c y between l i t t e r mates. One of the most accurate methods of feeding so that maximum differences i n rate and e f f i c i e n c y of gain can be obtained i s that of Isoc a l o r i c Intake at Equal Body Weights. The method was f i r s t used by Dunlop (1935) to demonstrate wide differences i n live-weight gain between pigs. Dunlop showed from actual metabolism and fa t measurements on swine that the most s i g n i f i c a n t explanation for differences i n l i v e weight gain was based on the - 6 -actual energy stored as body gain. He pointed out that the storage of 1 gram of f a t resulted i n the retention of 9 c a l o r i e s while the storage of 1 gram of protein with i t s associated water represented the retention of 1 c a l o r i e . Dunlop's measurements fo r back-fat thickness on fast and slow growing pigs of his basal metabolism studies showed that during the growth phase the rapid-gaining animal had 2 . 9 cm. of back- f a t while the slow gaining animal had 3.1 cm. When Dunlop corrected the f i n a l weights of the two pigs for differences i n c a l o r i c content by back-fat. measurements, i t was shown that the gains could be calculated on an equal energy basis and the f i n a l corrected weights consequently varied only to a s l i g h t degree for i n d i -viduals on one treatment. Factors other than the composition of the gain, such as s p e c i f i c dynamic action, b i o l o g i c a l value of the protein i n the r a t i o n , and d i g e s t i b i l i t y of the ra t i o n may a f f e c t the rate and the e f f i c i e n c y of the gain, but i t i s l o g i c a l that the major factor must be the nature of the gain made by the animal. Therefore, the rate of gain i s probably a good i n d i c a t i o n of the nature of gain, and thus probably c l o s e l y related to the e f f i c i e n c y of the gain. If the considerations previously outlined can be confirmed by experimental evidence, i t would seem that a clearer understanding of the normal growth pattern of the hog might be forthcoming. Thus, the present study i s an attempt to evaluate the importance of s p e c i f i c factors that are known to influence the assessment of rate and e f f i c i e n c y of gain i n Yorkshire Swine i n the pre-weaning and post-weaning stages of growth. - 7 -FACTORS INFLUENCING THE ASSESSMENT OF RATE AND FEED EFFICIENCY OF GROWTH IN YORKSHIRE SWINE. THE INFLUENCE OF ENERGY LIMITATIONS AND HYPOFERROUS  ANEMIA ON PRE-WEANING AND POST-WEANING GROWTH RATES OF YORKSHIRE SWINE. A. ENERGY LIMITATIONS 1. Introduction The present work was an attempt to study the i n t e r -a c t i o n of two d i f f e r e n t factors known to af f e c t the growth rate of suckling p i g l e t s . The two factors were examined separately. Part A was a study of the a v a i l a b i l i t y of energy to the suckling p i g l e t s during the pre-weaning growth period. An attempt was made to determine i f the average sow was able to provide suf-f i c i e n t energy (food) to permit maximum growth of her suckling young. The effe c t of the limited available energy on the growth rate of the l i t t e r during the suckling period and during the post-weaning period was explored. The existence of an energy d e f i c i t to the suckling p i g l e t s was expected and i t was deemed essential to provide them with a high energy creep r a t i o n . Such a creep ra t i o n was formulated and tested. Proof of i t s adequacy i n supplying the n u t r i t i o n a l demands of a rapidly growing l i t t e r before weaning was demonstrated. In Part B, the creep ra t i o n , (U.B.C. Ration No. 18) was used to eliminate as far as possible the eff e c t s of the energy deficiency to the suckling p i g l e t s and hence permit a - 8 -study of the influence on growth rate of various prophylactic treatments for n u t r i t i o n a l anemia. - 9 -2 • Review of Literature In the production of market pigs a rapid rate of growth i s overlooked by most commercial swine farmers. The foremost thought should be, the faster the gain, the less feed required per unit gain i n weight. Therefore, when a hog reaches market weight ra p i d l y , there w i l l be a greater saving on t o t a l feed and overhead costs. I f a hog i s to reach market weight by 160 days, i t must a t t a i n maximum growth i n the pre-weaning phase. This simple basic fact i s often overlooked i n a l l aspects of swine selection, breeding and n u t r i t i o n . In order to have complete expression of genotypic differences i n animals when selecting for growth and e f f i c i e n c y of growth, the non-genetic v a r i a t i o n must be at a minimum. Thus selection for growth rate at any stage of development, whether pre-weaning or post-weaning, w i l l be most successful when a l l animals receive the required energy and protein to permit maxi-mum growth. If the required energy and protein i s supplied, then maximum growth rate should be attained and the genetic potential of the p i g l e t w i l l be exhibited. With the attainment of maximum growth, as i s a c t u a l l y achieved by some 4 per cent of the Ca-nadian Swine population, the p i g l e t w i l l show a steady weekly increase (actually daily) i n the increments of absolute body gain from b i r t h u n t i l puberty as demonstrated by the data of Waldern and Wood ( 1 9 5 1 ) . Existing data on the pre-weaning growth phase of the hog have shown that t h i s absolute increase i n body gain from b i r t h to weaning has not yet been attained i n most l i t t e r s . Many investigators working on the various phases of - 10 -swine production have t r i e d to explain t h i s discrepancy i n rate of growth between the upper 4 per cent of the population and the remaining 96 per cent. (1) Milk Production by Sowst Donald (1937)} working on the milk secreting a b i l i t y of sows, found that d i f f e r e n t mammary gland sections of the udder may secrete very d i f f e r e n t quantities of milk. He also noted as did Bonsma and Oosthuizen (1935) and Carlyle ( 1 9 0 3 ) , that i n general, each pig nurses the same teat throughout the suckling period. Considering the above points, Donald con-cluded that differences i n n u t r i t i o n a l opportunity are the source of many of the variations i n the weight of pigs at both three and eight weeks, consequently weight differences at these ages are a poor i n d i c a t i o n of differences i n genotype for growth. This would also tend to explain the low h e r i t a b i l i t y estimates of weaning weight and the poor c o r r e l a t i o n between pre-weaning growth rate and subsequent age-to-market as found by many workers doing h e r i t a b i l i t y and c o r r e l a t i o n studies with swine. Donald (1937) has suggested that the growth variations may be due to inherent differences i n appetite stimulus. Support for t h i s contention i s provided by J o l l i f e (1950) with his proposal that human appetite i s controlled by the "appestat" center, of the p i t u i t a r y . One of the most obvious explanations for the f a i l u r e of growth rates to increase i n suckling p i g l e t s (an increase i n the absolute sense) from week to week as expected was pre-sented by Smith ( 1 9 3 9 ) . In a study of eleven sows, he reported an average d a i l y milk flow i n pounds by week of l a c t a t i o n as follows: - 11 -Week of Lactation Pounds of Milk Per Day 1 5.01 2 7.46 3 8.40 4 7.80 5 5 . 7 2 6 5 . 7 7 7 4 . 6 5 8 3.24 The data of Smith (1939) and of other workers indicates an absolute decrease i n milk secretion a f t e r the t h i r d week; co-incident with t h i s i s the decline i n growth rate and a l e v e l l i n g of the growth curve of the l i t t e r as exhibited i n the following data of Comstock et a l . (1942). Their data were collected from d i f f e r e n t sub-stations of the Minnesota Regional Swine Breeding Laboratory and represent weekly weighings of some 200 pigs from b i r t h to weaning during the years 1939 - 1940 i n c l u s i v e . Mean Weight Increment for Week Number (Comstock et a l . 1942) 1 ! 1 ± 1 £ Z & 2 . 3 2 l b s . 2.99 3 .23 3.01 2.48 2.84 3.64 5.92 A l l pigs were creep-fed either corn and skim milk or corn and dry rendered tankage. Their creep rations were inadequate to permit maximum growth of the suckling young, hence the observed decrease i n body gain at the fourth week from b i r t h . Ashton et a l . (1943) studying growth rates i n York-shire nursing pigs, noted a decrease i n average d a i l y gain between the second and fourth week from b i r t h . - 12 -Age i n Weeks Average Weight Average D a i l y Gain (Ashton et a l . 194-3) B i r t h 2 . 7 .42 1 5.3 .46 2 8.5 .46 3 1 1 . 9 .47 4 1 5 . 1 .45 5 .18.3 .48 6 21.9 .53 7 2 5 . 8 .61 8 3 0 . 5 .73 P i g l e t s were not creep-fed but were allowed to s t e a l feed from the r a t i o n a l l o t t e d to the sow. A t o t a l of 140 pigs were repre-sented i n the study. The above trend has been well demonstrated by Waldern and Wood ( 1 9 5 D where data were collected from some 2 0 0 York-shire pigs at a commercial swine establishment. Weighings were taken weekly from b i r t h to a market weight of 2 0 0 pounds. Figure 1 (Page 3 2 ) demonstrates the c h a r a c t e r i s t i c slowing of growth rate of i n d i v i d u a l Yorkshire p i g l e t s as taken from t h i s report. Results reported by Bonsma and Oosthuizen ( 1 9 3 5 )> and other data cited by them agree very well with Smith's ( 1 9 3 9 ) data. Later, Smith ( 1 9 5 2 ) measured the milk production of f i v e Berkshire sows over th e i r f i r s t three l a c t a t i o n s . His data indicated a trend similar to that of Smith ( 1 9 3 9 ) with - 13 -the exception that the peak of l a c t a t i o n was i n the f i f t h week instead of the t h i r d week Figure IV (Page3 2a). The precise l o c a t i o n of t h i s peak i n l a c t a t i o n i s probably controlled by n u t r i t i o n a l and genetic f a c t o r s . The milk production data f o r Smith's (1952) sows are presented below: Week of Lactation Pounds of Milk Per Day 1 9 2 1 2 . 9 3 14 .5 4 1 6 . 6 5 1 7 . 5 6 1 7 . 0 7 1 5 . 2 8 1 2 . 5 The increase i n milk production reported by Smith (1952) over that reported by Smith (1939) was primarily due to a higher plane of n u t r i t i o n for the sows i n the more recent publication, and secondly due to differences i n genetic a b i l i t y of the animals tested to produce milk. Smith (1952) also attributes -. the higher t o t a l y i e l d of milk to the use of d i f f e r e n t suckling i n t e r v a l s when l a c t a t i o n a l performance was measured. For ex-ample, sows suckled on a one hour frequency gave approximately one-third more milk than those on a two hour frequency. The higher weekly milk production and hence i n -creased t o t a l milk production i s r e f l e c t e d i n a s h i f t of the point of growth delay, as shown by the data of Smith ( 1 9 5 2 ) , from the t h i r d to the f i f t h week. The weekly weight gains at - 14 -the f i f t h , s i x t h and seventh weeks are not lower than those of the previous weeks, a trend also shown by Comstock's data where the gain drops from 3 . 2 3 pounds at three weeks to 3 . 0 1 pounds at four weeks and 2.48 pounds at f i v e weeks, then r i s e s again from the sixth week onward to weaning at eight weeks. The following three tables are taken from the data on Smith ( 1 9 5 2 ) . Table I indicates the eff e c t of successive lactations i n increasing the milk production of the sow. Table II shows the weekly weight-gains of p i g l e t s from b i r t h to wean-ing as affected by subsequent l a c t a t i o n periods i n the same sow. Table III presents comparative data on the milk y i e l d of sows, as considerable v a r i a t i o n exists between breeds, i t i s suspected that plane of n u t r i t i o n and method of analysis probably exerts the greatest ef f e c t on the results obtained. Noteworthy i n Table I i s the marked difference i n t o t a l milk production between the f i r s t and t h i r d l a c t a t i o n , a difference of 3 5 0 pounds. This could represent an increase of 4 pounds per pig weaned at eight weeks of age for a l i t t e r of 7 pigs. This computed estimate i s i n agreement with data i n Table I I , where the increase i n weekly gains and higher weaning weight of p i g l e t s from sows i n the i r t h i r d l a c t a t i o n i s compared to p i g l e t s from sows i n the i r f i r s t l a c t a t i o n . Every sow was fed on the same ra t i o n and a l l p i g l e t s had a dry creep feed and skim milk before them from four weeks post-farrowing. Table I I : AVERAGE WEEKLY WEIGHT-GAINS PER LITTER AND PER PIG OVER THREE LACTATIONS (SMITH 1952). Lactation Weight Gain Weeks In Lactation Totals Per Week 1 2 2L i 1 £ Z 8 (1) Per l i t t e r (lbs.) 16.6 19.2 22.9 26.7 26.9 33.2 43.9 41.9 231.3 " pig (lbs.) 2.37 2.74 3.27 3.81 3.84 4.74 6.27 5.98 33.02 (2) Per l i t t e r (lbs.) 18.2 24.3 26.4 29.5 33.4- 34-.1 41.3 4-5.5 252.7 pig (lbs.) 2.6 3.4-7 3.78 4.21 4.78 4.87 5.9 6.5 36.11 (3) Per l i t t e r (lbs.) 23.7 30.6 28.5 33-7 36.0 45.4 55.7 59.4 313.0 " pig (lbs.) 2.89 3.73 3.4-7 4-.12 4.39 5.53 6.79 7.24 38.16 H Table I I I : COMPARATIVE DATA. ON MILK YIELD FROM ELEVEN INVESTIGATIONS AUTHORITY C a r l i s l e (1903) Schmidt & Lau-precht (1926) Hampel (1928) Schneider (1934) Olofsson & Larsen (1930) Hughes & Hart ( 1935) Bonsma & Oosthuisen (1935) Wel l s , Beeson & Brady (1939) Smith (1952) Logan (1950) Waldern (1952) BREED Berkshire Poland China Razorback Landschwein Number of Average Average D a i l y Pro- Average T o t a l Pro-Lactat ions L i t t e r Size duct ion Per Sow ( l b . ) d u c t i o n Per Sow ( lbs . ) Edelschwein Yorkshire Large Black Poland China & Duroc Jersey Berkshire Yorkshire Yorkshire 4 4 4 26 22 22 4 2 52 43 15 2 10 7 . 7 7 . 5 6 . 3 8 . 3 8 . 3 8 . 5 7 . 9 6 . 6 7 7 . 4 10 10 6.31 4.86 5 .17 $.9 7 . 3 5 7.16 10.34 6.8 6 .55 11.7 14.4 10 .5 20.1 3 5 4 . 4 3 7 2 . 2 2 8 9 . 5 3 8 8 . 2 411 .6 401 .2 1 5 0 8 . 5 k& S 1 413 .2 3 6 6 . 7 655 808 532 1126 k Average for period between 2nd and 8 t h week. rS T o t a l for 7 weeks. - 17 -Table I: MEAN WEEKLY MILK PRODUCTION IN POUNDS PER SOW  OVER THREE LACTATIONS (SMITH 1 9 5 2 ) . Weeks of Lactation Lactation 1 2 1 1 1 6 £ 8 Totals 1 s t Lactation 44 5 8 7 0 8 2 9 0 9 7 8 9 7 1 6 0 1 ( 3 5 p i g l e t s ) 2 n d Lactation 6 7 9 9 1 1 2 124 1 2 8 124 1 1 7 9 5 8 6 6 ( 3 5 Piglets) 3 r d Lactation 7 7 114 124 1 4 3 149 1 3 7 1 1 5 9 8 9 5 7 ( 3 5 p i g l e t s ) Average of 3 6 2 . 6 9 0 . 3 1 0 2 1 1 6 . 3 1 2 2 . 3 1 1 9 . 3 1 0 7 8 8 8 0 7 . 8 Lactations Feed consumption data presented by Smith (1952)show a marked increase i n dry feed consumption by the suckling pig-l e t s i n the s i x t h , seventh and eighth weeks, which coincides with the f a l l i n y i e l d of sows' milk. ( 2) Composition of Sow's Milk. Knowledge of changes i n the composition of the sow's milk over the entire l a c t a t i o n period i s e s s e n t i a l to an under-standing of variations i n l i t t e r growth. To date, a l l data published on the composition of sow's milk show considerable v a r i a t i o n i n content of f a t , protein, lactose and t o t a l s o l i d s . W i l l e t et a l . ( 1 9 4 6 ) have presented evidence that the fat content of sow's milk can be influenced by the type of feed. They fed three mixes of varying f a t l e v e l s to t h e i r sows and obtained the following r e s u l t s : - 18 -FEED FAT TEST OF SOWS' MILK - Per cent Grain alone (containing 2.8% fat) 6.1 Grain + Garbage 7.8 Garbage (containing 27% fat) 9.6 They also stated that there was no s i g n i f i c a n t increase i n the weaning weight of the p i g l e t s from each group. the f a t content of sow's milk from the time of farrowing u n t i l the t h i r d day when the l e v e l had increased to 9 per cent, i t then f e l l sharply u n t i l the second or t h i r d week, at which point i t l e v e l l e d o f f at 6.5 to 7 per cent and slowly declined to the end of the l a c t a t i o n period at eight weeks. As with the dairy cow, the fat content was found to be higher when sows were fed i n dry l o t than when fed on pasture. Bowland et a l . (194-9) also noted a decided decline i n a l l milk constituents to the t h i r d week, followed by a s l i g h t increase and a l e v e l l i n g o f f to the end of the l a c t a t i o n period. They postulated that the t h i r d to fourth week was a c r i t i c a l period i n the l i f e of the suckling p i g l e t . Smith (1952) on milk production and composition of sow's milk, are very s i m i l a r to those of Bowland (1949). Table IV presents a summary of analyses reported f o r sows' milk. Bowland et a l . (194-9) have reported a sharp r i s e i n The r e s u l t s of Braude (194-7), (1950), (195D and - 19 -Table IV: COMPARATIVE ANALYSES OF SOWS' MILK FROM TEN INVESTIGATIONS Authority Percentage Content of Constituents Total Solids Fat Protein Lactose Braude et a l . (194-7) 1 9 , 9 8 . 2 5 . 8 4 . 8 Braude et a l . ( 1 9 5 D 1 9 . 3 7.6 5.6 5 . 1 Wells et a l . (1939) 16.4 5 . 3 4 . 9 5 . 3 Albig 1 8 . 8 7 . 0 - -Newlander & Jones 2 5 . 1 1 1 . 8 - -Hughes & Hart ( 1 9 3 5 ) 1 7 . 8 5 . 3 6.3 -McMeekan (194-3) 1 9 . 2 5 . 9 7 . 0 5.4 Bowland et a l . (194-9) 20.6 7 . 2 7.4 5 . 1 Heidebrecht et a l . ( 1 9 5 D 19.0 8 . 0 5 . 0 -Smith ( 1 9 5 2 ) 1 9 . 8 7 . 7 6.2 5 . 0 (3) Energy Requirements of Suckling P i g l e t s . After perusing the l i t e r a t u r e further, there remained two other major factors relevant to the growth of the pig i n i t s pre-weaning existence. The f i r s t of the two i s introduced by the work of Ritzman et a l . (1941), who conducted basal metabolism measurements on Chester White pigs from ten days to one year of age. Ritzman's data indicated a high rate of metabolism u n t i l about two weeks af t e r b i r t h with a r e l a t i v e l y rapid decline thereafter. He concludes that t h i s i s a t y p i c a l b i o l o g i c a l trend of the metabolic function; a similar decline also t y p i f i e s growth rate i n goats and sheep. This trend i n basal metabolism may help to explain the break i n the growth curve (plotted on - 20 -a r i t h - l o g paper) of the suckling p i g l e t , at or about 14 days, re-gardless of the plane of n u t r i t i o n of the sow and l i t t e r . £4) Relation of B i r t h Weight to Weaning Weight. The second factor relevant to both pre-weaning and post-weaning growth of the p i g l e t and affected by the sow i s the d i r e c t relationship between b i r t h weight and weaning weight, and between weaning weight and age-to-market. Weaver et a l . (1943) present data on some 600 Poland China p i g l e t s demonstrat-ing a d i r e c t relationship between b i r t h weight and weaning weight. Following t h i s trend, he goes on to show that pigs with heavy weaning weights had an added advantage at 180 days of age, since they made more rapid gains i n the feed l o t a f t e r weaning. Some of Weaver's data i s presented i n Tables V and VI. The relationship between heavy b i r t h weight and heavy weaning weight can be read i l y explained by use of the basic con-cepts of reaction rate; i . e . a reaction whether i t be organic or inorganic w i l l proceed at a d e f i n i t e rate; the rate being controlled by the concentration of the l i m i t i n g constituent. In terms of animal growth th i s means that the amount of growth occurring at any given instant i s proportional to the active metabolic mass. - 21 -Table V: INFLUENCE OF BIRTH WEIGHT OF PIGS UPON GAIN  IN WEIGHT AND WEANING WEIGHT (WEAVER 194-3). Gain i n Weight Groups Pigs Weight @ 56 Days to 56 Days Below 2.5 l b s . 81 Pounds 2.2 Pounds 25.7 Pounds 23.6 2.5 - 3.0 159 2.7 28.9 26.2 3.0 - 3.5 206 3.2 32.9 29.7 3.5 + 150 3.8 37.0 33.2 Table VI: INFLUENCE OF WEIGHT OF PIG AT WEANING UPON FUTURE FEED LOT PERFORMANCE (WEAVER 1943). Weaning Weight Groups No. , of Pigs Percent Mean Weaning of Total Weight Weight at 180 Days Pounds Pounds Pounds 15 - 20 14 4.2 16.9 189 20 - 25 40 11.9 22.2 196 25 - 30 90 26.8 27.2 202 30 - 35 78 23.2 32.1 208 35 - 40 58 17.3 36.7 218 40 - 45 26 7.7 41.7 228 4 5 - 50 22 6.5 46.8 234 50 - 55 7 2.1 52.9 254 The data of Weaver et a l . are i n close agreement with that of Waldern and Wood (1952) where growth data from b i r t h to weaning were collected on 350 Yorkshire p i g l e t s . Part of t h i s data i s presented i n Table VII. - 22 -Table VII: INFLUENCE OF BIRTH WEIGHT OF YORKSHIRE  PIGLETS UPON GAIN IN WEIGHT AND WEANING  WEIGHT (WALDERN AND WOOD 1 9 5 2 ) . ( 5 6 Days) B i r t h Weight No. of Pigs Percent Mean B i r t h Mean Wean- Tota l of Total Weight ing Weight Gain ~~ Pounds Pounds , Pounds Below 2 . 5 l b s . 6 3 1 7 . 9 $ 2.13' 3 0 . 5 2 8 . 4 2 . 5 - 3 . 0 1 0 7 ' 3 0 . 5 2 . 7 5 3 4 . 6 3 1 . 9 3 . 1 - 3 . 5 1 1 0 3 1 . 4 3 . 2 6 3 7 . 2 3 4 3 . 6 + 7 1 2 0 . 2 3 . 9 5 41 .2 3 7 . 3 - 25 -3• A. Theoretical Calculation of Energy Production by the Sow, and Energy Requirements of the L i t t e r . After surveying the l i t e r a t u r e and observing our own data, the following facts are outstanding. 1. The milk supply of the sow becomes l i m i t i n g for maximum growth of the l i t t e r i n the second, t h i r d or fourth week of l a c t a t i o n , depending on the sow's milk production. 2 . Low b i r t h weights have a marked a f f e c t on sub-sequent weaning weights. 3. Low weaning weights increase age- to-market and hence post-weaning e f f i c i e n c y of feed conversion. In addition to the previous facts one must consider the physiological scale of time i n the l i f e of the pig. In the pre-weaning stage an excellent' pig w i l l probably grow at the following three rates to weaning: 10 per cent per day u n t i l 1 5 days, 5 per cent per day u n t i l 42 days and 2 . 5 per cent per day u n t i l $6 days or a f t e r . In the post-weaning phase, which i s some 1 5 0 days, the rates decrease from 1 . 2 0 per cent to . 0 5 per cent per day. Thus i n the f i r s t one t h i r d of the post-natal l i f e of the pig, physiological events are occurring f i v e times as fas t as they are i n the post-weaning stages, hence n u t r i t i o n must be optimum during t h i s period to meet a l l demands for rapid growth. To substantiate the l a s t statement one need only consider the work of McMeekan (1941) where carcasses of groups of hogs on d i f f e r e n t l e v e l s of n u t r i t i o n were examined p e r i o d i -c a l l y from b i r t h to market for growth rates of constituent parts, (bone, muscle, f a t , and a l l other e s s e n t i a l organs and t i s s u e s ) . He showed that n u t r i t i o n did not a f f e c t a l l parts - 24 -of the body or a l l tissues equally, but rather i n a selective or d i f f e r e n t i a l manner. An underfed or retarded hog was complete-l y d i f f e r e n t i n conformation and composition from a well-fed one. This was because n u t r i t i o n modified the normal growth rates of bone, muscle and f a t . In early l i f e n u t r i t i o n a l demands of bone were greatest, so that bone growth continued i n an under-fed animal even when i t was losing weight. Hammond (1944) has i l l u s t r a t e d the p a r t i t i o n i n g of nutrients schematically: STORAGE FAT Hammond vis u a l i z e d the scheme thus: When the nutrient l e v e l of the blood drops, the amount supplied to each tissue decreases, but the co n t r o l l i n g tissues of the body (brain, central nervous system) have the top p r i o r i t y for available nutrients thus non-^ functional constituents of the body are the f i r s t to be deprived (eg. storage fat and tissue f a t ) . McMeekan (1941) found a f t e r analysing hog carcasses that poor early n u t r i t i o n tended to retard bone and muscleJewe/o/»»»«*t. The degree of recovery from poor early n u t r i t i o n was limited - 25 -because the kind of growth made when n u t r i t i o n became adequate again was d i f f e r e n t from that which would have occurred had stunting not taken place, hence a retardation of growth was shown very well by the growth curve. Thus, McMeekan stated that the shape of the growth curve i s a major factor governing both conformation and composition of the hog. As pointed out by Brody (194-5) a unit of time on the physiological clock i s a much longer period i n the early chronological or physical age of an animal than i t i s at a l a t e r stage of growth, hence an interru p t i o n of growth due to a n u t r i t i o n a l deficiency at an early chronological age i s f a r more c r i t i c a l to the ultimate development of the i n d i v i d u a l than a similar i n t e r r u p t i o n l a t e r i n the growth period. The following calculations have been made i n an attempt to explain mathematically the energy relationship causing limited growth i n suckling piglets.(Table VIII Page 2 6 ) . The growth data used i n Table VIII were compiled by the author from a commercial swine operation (Arrowsmith Farms ( 1 9 5 D ) . The pig used as an example was one of a l i t t e r of 1 1 , with a mean weaning weight for the l i t t e r of 40 pounds at eight weeks. The i n d i v i d u a l weight d i s t r i b u t i o n of the l i t t e r was between 3 2 and 44 pounds. Growth curves of the l i t t e r indicate a marked decline i n growth rate at 1 5 days for the l i g h t e r and at 2 8 to 3 5 days for the heavier weaning p i g l e t s . Table VIII: THE DAILY CALORIC REQUIREMENTS OF A PIG THAT ATTAINED A WEANING WEIGHT OF 40 POUNDS AT EIGHT WEEKS. AND THE MILK PRODUCTION NECESSARY FROM A SOW TO PRODUCE A LITTER OF TEN SUCH PIGS. & " " f t * ftftft Age i n Body Weight Metabolizable Energy Cals. /Day Growth Require- Cals. /Day Sows Milk Required Days Requirements Calories /IO Pigs ments Cals. /Day /IO Pigs Lbs. /Day / L i t t e r /Day /Pig . . / P i g - of 10 Pigs Kg_s. Pounds (Mitchell) (Brody) B i r t h 1.13 2.5 330 3,300 308 3,080 5.04 4.70 5 1.90 4.2 570 5,700 450 4,500 8.71 6.88 10 3.04 6.7 810 8,100 635 6,350 12.38 9.70 15 4.18 9.2 1030 10,300 801 8,010 15.74 12.24 20 5.45 12 1250 12,500 972 9,720 19.11 14 . 86^ cn 17.32 , 25 6.72 14.8 1460 14,600 1133 11,330 22.32 30 8.18 18 1680 16,800 1307 13,070 25.68 19.98 35 9.77 21.5 1900 19,000 1488 14,880 29.05 22.75 40 11.36 25 2110 21,100 1662 16,620 32.26 25.41 45 13.27 29.2 2330 23,300 1861 18,610 35.62 28.45 50 15.45 34 2540 25,400 2080 20,800 38.83 31.80 56 18.18 40.0 2800 28,000 2342 23,420 42.81 35.81 0 Data from a commercial swine operation. * A f t e r M i t c h e l l and K e l l y (1938). M A f t e r Brody (1945) on the assumption that growth requirements - 4x basal energy requirements. er Hughes and Hart (1935), that 1 pound of sows milk i s equivalent to 654 C a l o r i - 27 -(1) Milk Production of Experimental Sows. Table IX presents the milk production of 10 Yorkshire sows as measured by the method of Bonsma and Oosthuizen (1935) at the commercial swine farm. A l l l a c t a t i n g animals were fed f o r maximum intake on a standard conforming to National Research Council Recommendations for lactating sows. The r a t i o n was formulated and analysed at the Animal N u t r i t i o n Laboratory, Department of Animal Husbandry, University of B r i t i s h Columbia. The growth curves of i n d i v i d u a l p i g l e t s weaning from these 10 l i t t e r s are s i m i l a r to those discussed above under Table V I I I . Table IX: MILK PRODUCTION OF TEN ARROWSMITH YORKSHIRE SOWS AT VARIOUS STAGES OF LACTATION. Sow No. No. of Pigs. Age of L i t t e r Milk i n Days Production 3 7 8 E 1 2 2 1 8 . 1 l b s . 5 9 3 D 1 2 6 1 8 . 6 5 9 B 9 13 1 7 . 9 3 8 3 E 1 1 1 5 29.4 1 3 6 B 1 1 1 6 27 . 6 5 9 6 D 12 24 2 2 . 3 4 1 5 F 8 3 6 1 7 . 8 3 5 0 E 9 3 9 21.0 1 1 9 B 6 40 1 2 . 5 2 8 6 F 1 1 4 8 1 6 The milk production indicated above i s of the same order i n the l a s t three weeks of the l a c t a t i o n period as that reported - 28 -by Smith ( 1 9 5 2 ) , but the f i r s t four weeks production of the York-shire i s far greater than the Berkshires. Figure IV presents the l a c t a t i o n curves of sows taken from three investigations. This increase i n production p a r t i a l l y accounts for the heavier weaning l i t t e r s attained with the Yorkshire sows over those of the Berkshire sows as reported by Smith ( 1 9 5 2 ) , but another important factor explaining the increased milk production i s the increase i n number of piglets weaned. The Yorkshires weaned an average of 10 p i g l e t s as compared with 7 for the Berkshires. Looking at Table VIII, we see that the t o t a l metabo-l i z a b l e energy requirements for the pig represented, i s 1680 Calories at 30 days of age. For a l i t t e r of ten such pigs (the pig repre-sented i n Table VIII, as indicated e a r l i e r , i s from a l i t t e r of 11 pigs that averaged 40 pounds at weaning) the sow must supply i n her milk 16,800 Calories. Using the data of Hughes and Hart (1935)? that one pound of sows milk i s equivalent to 654 Calories, then to supply 16,800 Calories the sow must produce 2 5 . 7 pounds of milk. Referring to our own measurements of milk production i n Table IX, we see that at 34 days the sow could only produce 2 2 . 3 pounds of milk for a l i t t e r of 12 p i g l e t s . In the data of Smith (1952) the milk production of the sow was l i m i t i n g nearly ten days e a r l i e r for maximum growth of a l i t t e r of ten pigs wean-ing at .40 pounds. Now assuming a requirement of 2 5 . 7 pounds of milk for the l i t t e r of ten at t h i r t y days there i s some doubt as to the physical a b i l i t y of the sow to consume s u f f i c i e n t ration to produce the volume of milk at increasing increments required by an ever growing l i t t e r . Assuming that the sow has an energetic e f f i c i e n c y of milk production equivalent to an excellent dairy - 29 -cow (35%)j i t can be shown that the sow must consume 42 pounds of feed to produce 2 5 . 7 pounds of milk. Gross E f f i c i e n c y = milk c a l o r i e s produced of Milk Production feed (including maintenance) calories consumed .35 - 25.7 x 654 1 ( * ** 1814 x (T.D.N, lbs.) iSS ^ • 42 Pounds of Feed k Ration contains 80 per cent Total Digestible Nutrients. kk Metabolizable energy i s 80 per cent available f o r milk production. Obviously i t i s impossible f o r the sow to consume 42 pounds of feed per day, an upper l i m i t would be nearer 24 pounds. Energy for production of milk above the l a t t e r l e v e l of feed intake must come from body stores, but these are also l i m i t i n g . From these calculations.and what has gone before i t i s apparent that further supplementation of the suckling pigs feed intake i s necessary. It was i n t h i s l i g h t that experimental work was carried out to determine the influence of an adequate creep r a t i o n on the pre and post-weaning growth rate of suckling York-shire piglets.-- 30 -4. Experimental A creep r a t i o n , (U.B.C. Ration No. 1 8 ) was formulated at the Animal N u t r i t i o n Laboratory, University of B r i t i s h Columbia and tested at a commercial swine unit (Arrowsmith Farms ( 1 9 5 D ) . The requirements followed i n compiling t h i s r a t i o n were, as set f o r t h for the pig, by the United States National Research Council Committee on Swine N u t r i t i o n . The composition of t h i s r a t i o n and a l l other rations used i n Part A and Part B of t h i s thesis are presented In Table X. Protein, f a t , f i b r e , moisture and other l e v e l s of nutrients of the rations of Table X are given i n Table XI. . A l l l i t t e r s were offered the creep feed i n small self-feeders from b i r t h . The other rations, with the exception of the Sow rations, were s e l f - f e d over the weight range as i n -dicated i n Table X. A l l animals were weighed weekly from b i r t h to a market weight of 200 pounds. - 31 -5 . Results As the experiment was conducted at a commercial swine farm, the influence of the creep rat i o n can only be compared against a commercial weaner rati o n that was used i n previous years as a supplement for the suckling p i g l e t s . Table XII pre-sents the results of the previous treatment using commercial rations against the present formulated rations for 15 selected sows over two successive l a c t a t i o n s . In Table XIII the d i s t r i b u t i o n of p i g l e t s i n d i f f e r e n t weight groups at weaning for the years 1949 and 1951-B i s pre-sented (1951-B refers to l i t t e r s weaned i n the F a l l of that year). Table XIV presents the c o l l e c t i v e data f o r 1951-B and 1952-A. where a l l animals were on U.B.C. rations 18 to 24 i n c l u s i v e (1951-B refers to F a l l weaned p i g l e t s and 1952—A. refers to Spring weaned p i g l e t s i n those respective years). This table demonstrates the eff e c t of heavier weaning weight upon weight at f i v e months and age at 200 pounds. Figure II i s an a r i t h - l o g plot demonstrating the effect of a heavier weaning weight on subsequent growth rate of the Yorkshire hog. - 3 2 -20 30 AGE IN DATS 60 80 100 AGE IK DAIS 10 20 30 40 50 AGE IH DAZS - 33 -SWINE RESEARCH PROJECT 1951-53 SPECIAL ANIMAL RATIONS Table X a: U.B.C. Ration No. 18-52 Swine Creep Ration Revised June 26, 1952. Ingredient Pounds per Ton Hulled Oats 1000 Ground Wheat 525 F i s h Meal 225 Meat Scraps 75 Skim Milk Powder 50 A l f a l f a Leaf Meal... 100 Steamed Bone Meal 20 S a l t % 2000 Supplement with: R i b o f l a v i n 20 grams (Riboflavin Supplement... 560 grams) Pantothenic Acid 15 grams CuS0 4 11 grams F e 2 (S0 4 )3 225 grams - 34 -SWINE RESEARCH PROJECT 1951-53 SPECIAL ANIMAL RATIONS Table X b: U.B.C. Ration No. 2 0 - 5 2 Swine Weaner Ration (To 70 lbs.) Ingredient Pounds per Ton Ground Wheat 800 Ground Barley 800 F i s h Meal 175 Meat Scraps 75 Skim Milk Powder 25 A l f a l f a Leaf Meal 100 Steamed Bone Meal 20 Salt £ 2000 - 35 -SWINE RESEARCH PROJECT 1 9 5 1 - 5 3 SPECIAL ANIMAL RATIONS Table X c: U.B.C. Ration No. 2 2 - 5 2 Swine Grower Ration (To 1 2 5 l b s . ) . Ingredient Pounds per Ton Ground Oats 2 5 0 Ground Wheat 7 0 0 Ground Barley 7 0 0 F i s h Meal 1 2 5 Meat Scraps 5 0 Linseed Meal 5 0 A l f a l f a Leaf Meal 1 0 0 Steamed Bone. Meal 2 0 Salt £ 2 0 0 0 - 56 -SWINE RESEARCH PROJECT 1951-53 SPECIAL ANIMAL RATIONS Table X d: U.B.C. Ration No. 24 Swine Fattener Ration (To Market). Ingredient Pounds per Ton Ground Oats 400 Ground Wheat 275 Ground Barley 1100 F i s h Meal 30 Meat Scraps 30 Linseed Meal 40 A l f a l f a Leaf Meal 100 Steamed Bone Meal 12 Ground Limestone 8 S a l t £ 2000 - 57 -SWINE RESEARCH PROJECT 1 9 5 1 - 5 3 SPECIAL ANIMAL RATIONS Table X e: U.B.C. Ration No. 2 6 Sow Ration (Nursing and Dry). Ingredient Pounds per Ton Ground Whole Oats 400 Ground Wheat 2 7 5 Ground Barley 1 0 7 5 F i s h Meal 40 Meat Scraps 40 Linseed Meal 4 5 A l f a l f a Leaf Meal 1 0 0 Steamed Bone Meal....... 1 2 Ground Limestone 8 S a l t 1 2000 - 38 -SWINE RESEARCH PROJECT 1 9 5 1 - 5 3 SPECIAL ANIMAL RATIONS Table X f: U.B.C. Ration No. 28 Farrowing Ration, Ingredient Pounds per Ton Ground Whole Oats 300 Ground Wheat 200 Ground Barley 8 5 0 Wheat Bran 4-00 F i s h Meal 40 Meat Scraps 40 Linseed Meal. 4 5 A l f a l f a Leaf Meal 1 0 0 Steamed Bone Meal 1 2 Ground Limestone 8 S a l t __£ 2 0 0 0 Table XI a: NUTRIENT LEVELS OF EXPERIMENTAL SWINE RATIONS U.B.C. Ration No. 18 INGREDIENT Creep Feed to 8 Weeks. Percent Estimated Required by Analysis T.D.N.-/lb. CRUDE PROTEIN Computed (Nx6 .26) CALCIUM-gm/lb. Computed PHOSPHORUS-gm/lb. Computed CAROTENE-mg/lb. THIAMINE-mg/lb. RIBOFLAVIN-rag/lb. NlACIN-mg/lb. PANTOTHENIC ACID-mg/lb. TRYPTOPHANE-gm/lb. LYSINE-gm/lb. METHIONINE-gm/lb. FIBRE FAT MOISTURE 19.4-4 2 1 . 0 0 0 . 9 9 1 .23 0.48 0 . 9 5 2.97% 3.90% 1 0 . 2 1 $ 1 l b . Ration . 8 0 .21 5 . 6 4 . 3 4 . 0 5 2 . 7 1 . 8 8 14 .3 6 . 9 1 . 0 8 4 . 6 2.24 1 l b . N.R.C.. . 7 5 .18 3.0 2.0 . 75 . 5 0 .80 5.0 4 . 5 .90 4 . 6 2 . 7 U.B.C. Ration No^gO Weaner Ration Fed to 60 l b s . Percent Estimated Required by Analysis 2 0 . 3 6 2 0 . 0 0 1 .10 1 .21 0 . 5 9 0 . 9 0 3 . 3 1 3 . 1 3 1 0 . 0 3 1 l b . Ration .76 .20 5 . 5 4.1 4.14 2.46 1 .77 20.8 5.8 1.02 4.0 2.08 1 l b . N.R.C. . 7 5 .18 3 . 0 2 . 0 . 7 5 . 5 0 . 8 0 5 . 0 4 . 5 . 9 0 4 . 6 2 . 7 Table XI b: NUTRIENT LEVELS OF EXPERIMENTAL SWINE RATIONS. INGREDIENT T.D.N.-/lb. CRUDE PROTEIN Computed (Nx6.25) CALCIUM-gm/lb. Computed PHOSPHORUS-gm/lb. Computed U.B.C. Ration No. 22  Grower Feed to 125 l b s . U.B.C. Ration No. 24 Finisher Feed to Market U.B.C. Ration No. 26 Sow Ration Percent Estimated Required Percent Estimated Required Percent Estimated Required by 1 l b . 1 l b . by 1 l b . 1 l b . by 1 l b . 1 l b . Analysis Ration N.R.C. Analysis Ration N.R.C. Analysis Ration JL.R.C. 19.00 17.00 1.46 0.93 0.49 0.77 CAROTENE-mg/lb. THIAMINE-mg/lb. RIBOFLAVIN-mg/lb. NIACIN-mg/lb. PANTOTHENIC ACID-mg/lb. TRYPT©PHANE-gm/lb. LYSINE-gm/lb. METHIONINE-gm/lb. FIBRE 4.11 FAT 2.60 MOISTURE 10.2^7 .72 .17 4.2 3.5 4.15 2.46 1.49 23.6 5.6 .91 3.14 1.75 .75 .16 2.5 1.5 1.00 .50 .80 5.0 4 .5 .80 4.1 2.5 15.17 13.00 0.99 0.67 0.41 0.56 5.80 2.50 10.19 .66 .13 3.06 2.5 4.20 2.58 1.13 22.1 4.9 .70 1.86 1.41 .75 .14 2.5 1.5 1.00 .50 .80 5.0 4 .5 .70 3.6 2.0 14.80 13.90 0.83 0.74 O.36 0.58 6.38 2.70 10.14 .66 .14 3.35 2.6 4 .20 2,56 1.17 22.0 4.9 .72 2.02 1.45 .75 .15 2.50 1.5 3.00 .50 .80 5.0 4.5 .60 2 .4 2.0 o - 41 -Table No. XI I : A COMPARISON OF THE MEAN WEANING WEIGHTS OF LITTERS CREEP FED ON A COMMERCIAL SWINE  WEANER RATION WITH THOSE CREEP FED ON RATION NQ.18 SOW NO. Mean Weaning Weight at 5 6 Mean Weaning Weight at Days Using a Commercial Swine 5 6 Days Using Ration Weaner Ration as a Creep Feed No. 18 as a Creep Feed 1 3 6 B 31 .5 40.0 5 9 B 28.4 41 . 8 183D 27.0 3 6 . 3 60B 3 3 . 3 46.0 189E 2 5 . 7 48.4 264C 2 6 . 5 3 6 . 9 148C 3 0.0 40.0 183D 27.0 3 6.0 107B 31 . 5 40.0 3 4 3 E 3 4 . 7 50.0 119B 28.0 41.0 593D 28 .7 3 7.0 390E 31 . 5 37.0 591D 28 .7 3 8.4 2 0 0 c 3 4 . 7 40.0 Mean 2 9 . 8 40 . 5 - 42 -Table X I I I : COMPARISON OF WEANING WEIGHTS AS DISTRIBUTED  AT FIVE POUND INTERVALS FROM UNDER 16 POUNDS TO 60 POUNDS AS AFFECTED BY TWO RATIONS. 194-9 - Using a commercial weaner rati o n as a creep r a t i o n . 1 9 5 1-B - Using the formulated creep rat i o n - U.B.C. Ration No. 1 8 . Weight Group Under 16 l b s . 1 6 - 2 0 2 1 - 2 5 2 6 - 3 0 3 1 - 3 5 3 6 - 40 41 - 4 5 4 6 - 5 0 5 1 - 5 5 5 6 - 6 0 mi Per Cent of Hogs at Weight . 8 8 5 . 9 1 2 2 . 5 4 2 7 . 5 7 2 8 . 2 2 8 . 7 5 3 . 7 2 2.41 1951-B Per Cent of Hogs at Weight 1 . 3 2 1 . 3 2 6 . 3 1 1 1 . 3 0 1 9 . 2 7 3 2 . 2 3 1 6 . 2 8 8 . 3 1 3 . 0 0 . 6 6 No. of Hogs Mean Weaning Weight 4 5 7 2 9 . 4 5 lbs, 3 0 1 3 6 . 5 6 l b s . Weight Group Under 3 6 l b s . 3 6 l b s . and over 1949 Per Cent 85.12 14 . 8 8 1951-B Per Cent 3 9 . 5 2 6 0 . 4 8 - 43 -Table XIV: THE INFLUENCE OF A HEAVIER WEANING WEIGHT ON SUBSEQUENT GROWTH RATE; WEIGHT AT FIVE  MONTHS AND AGE AT 200 POUNDS. Weaning Weight No. of Mean Weaning Group Weight Per Cent Weight at Age at of Total 5 Months 200 Pounds Pounds Pounds . Pounds Days 15 - 20 2 20 .4 124 196 21 - 25 28 23.4 5.4 1 3 8 . 6 . 1 9 0 . 5 26 - 30 46 2 8 . 8 . 8 . 9 143 .5 1 8 6 . 9 31 - 35 111 3 3 . 1 2 1 . 4 1 5 9 . 5 1 7 6 . 5 36 - 40 169 3 7 . 8 3 2 . 6 1 6 3 . 3 172 41 - 45 96 42 .8 1 8 . 5 1 7 2 . 2 1 6 7 . 6 46 - 50 50 4 7 . 4 9 . 6 1 7 9 . 7 165 51 - 55 _16 5 2 . 3 3 . 2 1 8 3 . 5 162 518 6 . 44 -Discussion After postulating that an energy debt existed for the suckling p i g l e t at two to f i v e weeks of age, i t has been shown by calculations, from metabolism studies and from milk production l e v e l s of sows that t h i s energy shortage i s quite r e a l and that the growth rate of the suckling p i g l e t i s retarded during t h i s period. Following t h i s , the primary objective of the experi-mental work was to determine the degree of growth rate increase to be gained i n the suckling p i g l e t by use of an adequate creep r a t i o n . The mean weaning weight at 56 days was raised from 2 9 . 5 to 3 6 . 5 pounds, an increase of seven pounds or 24 per cent over the previous mean weaning weight. These improvements also apply to the data of Ashton et a l . (1943) where mean weaning .weights of Yorkshire p i g l e t s were reported at 30 pounds at eight weeks. The eff e c t of heavier weaning weights on subsequent growth rate, and hence age at 200 pounds, i s p r a c t i c a l l y s e l f explanatory. For the mean weaning weight of 37 pounds, the corresponding age to market was 172 days; for the mean weaning weight of 29 pounds the subsequent age-to-market was 187 days, an increase of 15 days for the l i g h t e r weaning pig to reach market. From the economic standpoint of returns to the hog producer, which i s the ultimate c r i t e r i o n of growth rate studies, the extra 15 days at an average cost of 6 . 5 pounds of feed per pig per day would resu l t i n a t o t a l additional feed consumption of 97o5 pounds. At the current price of $ 6 8 . 0 0 per ton of rat i o n t h i s represents a saving of $ 3 . 3 0 per hog. In a large - 45 -commercial herd such as the one where this experiment was con-ducted, the saving on feed alone on some 8 0 0 hogs marketed would amount to $ 2 , 6 4 0 . 0 0 . Corresponding to an increase i n time required to reach market weight by the l i g h t e r weaning p i g l e t , w i l l be the lower e f f i c i e n c y of feed conversion. Part B of t h i s thesis w i l l demon-strate the rela t i o n s h i p between rates of growth and e f f i c i e n c y of feed conversion i n the post-weaning phase; but the r e l a t i o n -ship between adequate pre-weaning n u t r i t i o n , as influenced by the sow and supplemental creep rati o n , and subsequent post-wean-ing growth rate, has been profoundly demonstrated i n t h i s experi-ment . The experiment has also demonstrated the f e a s i b i l i t y of r a i s i n g l i t t e r s of ten p i g l e t s or more having mean weaning weights greater than 40 pounds. From Table XIV i t can be shown that 3 1 . 3 per cent of the 5 1 8 p i g l e t s weaned were i n the range of 40 pounds plus at eight weeks. Figure III presents an achievable growth curve for the Canadian Yorkshire to weaning at 5 6 days. It was stated that i n order to have complete expression of genotypic differences i n animals when selecting for growth and e f f i c i e n c y of growth, the non-genetic v a r i a t i o n must be at a minimum. Since the greatest portion of non-genetic v a r i a t i o n i s environmental and the major factor of environment a f f e c t i n g the rate of growth i s the plane of n u t r i t i o n , then under the experimental conditions which were established to permit maximum growth, weaning weights of the p i g l e t s of each l i t t e r represented i n the data should be approximately at th e i r genetic maximum. - 46 -By following the post-weaning growth curves of i n d i v i d u a l pig-l e t s , the data indicate that those animals which weaned at eight weeks at a r e l a t i v e l y low weight (30 pounds or less) also tended to grow slowly i n the post-weaning phase. Hence h e r i t a b i l i t y estimates for weaning weight under conditions of optimum n u t r i t i o n are probably higher than reported by most investigators. There-fore, i n order to establish consistency i n h e r i t a b i l i t y estimates for rate of gain i n the pre-weaning phase and weaning weight, n u t r i t i o n a l demands of the suckling young must be met. A regression of the age at 2 0 0 pounds against the weaning weight for the " 5 1 8 pigs found i n Table XIV, on a log-log grid provides a l i n e a r r e l a t i o n s h i p . After f i t t i n g the equation Y » aX^ to the data by the method of least squares, the following equation f o r the l i n e was calculated: Y r 3 6 7 X ~ ' 2 0 7 where Y i s the number of days required by a hog to reach 2 0 0 pounds when i t s weaning weight i s X. For example a pig that weighed 3 0 pounds at weaning would be expected to reach 2 0 0 pounds at: Y = 3 6 7 ( 3 0 ) " - 2 0 7 log Y n log 3 6 7 - . 2 0 7 log 3 0 log Y = 2 . 2 6 8 0 1 ... Y = 1 8 5 . 4 days i f n u t r i t i o n a l requirements f o r maximum growth were supplied, and i f the genetic potential for growth rate of the pig was not l i m i t i n g . By a similar c a l c u l a t i o n i t can be shown that a pig that weighs 4 5 pounds at weaning should reach 2 0 0 pounds by 1 6 6 . 9 days provided the same conditions hold as mentioned - 47 -above. Thus a difference of 15 pounds i n weaning weight represents a difference of 1 8 . 5 days required by a hog to reach 200 pounds. This would mean that for every pound gained at meaning there would be a reduction of 1 .23 days i n the time required to reach 200 pounds for the population studied. Q'48 -7. Summary and Conclusions It was postulated that energy was the l i m i t i n g factor a f f e c t i n g growth of the suckling p i g l e t . A retardation of growth at or about the tenth day onward was evident from studies of growth curves of suckling p i g l e t s . Calculations from metabolism studies of growing p i g l e t s and milk output of sows demonstrated p o s i t i v e l y that the milk production of the sow was l i m i t i n g the genetic growth p o t e n t i a l of the ra p i d l y growing suckling young. The necessity of supplying a high-energy, well-balanced creep r a t i o n at the c r i t i c a l period when milk supply i s i n s u f f i c i e n t , was foreseen. The formulation and subsequent testing of t h i s r a t i o n i n the laboratory and i n a commercial swine herd provides the basic experimental work f o r t h i s part of the present t h e s i s . The tested r a t i o n provided f o r a mean weaning weight of 37 pounds and with a subsequent mean market weight of 200 pounds at 172 days. These values f o r Yorkshire swine are con-siderably i n advance of values reported i n the l i t e r a t u r e , or by the Canadian Government hog testing program, Record of Per-formance and Advanced Registry. The tested r a t i o n provided the above mean weaning weight, but higher values are attainable and considerable work i s s t i l l required on pre-weaning n u t r i t i o n of the baby pig. The influence of adequate pre-weaning n u t r i t i o n of the suckling p i g l e t on post-weaning growth rate has been well demon-strated; but, the importance of the pre-weaning stage of de-velopment of the p i g l e t , where events In the phys i o l o g i c a l sense are happening very rapidly, cannot be over-emphasized, An i n t e r -- 49 -ruption due to any deficiency at th i s time thus more c r i t i c a l l y concerns development than an interruption at a l a t e r time when the active physiological mass per unit body mass has decreased and consequently growth rate has decreased. - 50 -THE INFLUENCE OF ENERGY LIMITATIONS AND HYPOFERROUS  ANEMIA ON PRE-WEANING AND POST-WEANING GROWTH RATES  OF YORKSHIRE SWINE. B. HYPOFERROUS ANEMIA 1. Introduction The normal hemoglobin l e v e l of suckling p i g l e t s i s 12 grams of hemoglobin per 100 cubic centimeters of blood. Studies on swine anemia indicate that l i t t e r s of suckling p i g l e t s main-t a i n good growth and wean at an average of 28 pounds per l i t t e r at eight weeks post-farrowing when hemoglobin l e v e l s are 6 to 9 grams per 100 cubic centimeters of blood (6 to 9 grams per cent). The chief objective of thi s section has been to demon-strate that suckling p i g l e t s with hemoglobin l e v e l s below 8 grams per cent cannot grow normally and a t t a i n t h e i r maximum genetic weaning weight at eight weeks, which i s the order of 48 pounds not 28 pounds, unless both s u f f i c i e n t i r o n and energy are a v a i l -able. A review of previous experimental work on hypoferrous anemia i n suckling p i g l e t s leads to the hypotheses that unless the suckling l i t t e r s were creep-fed on a ra t i o n that would pro-vide maximum expression of the l i t t e r s ' genetic pot e n t i a l to grow, any treatment f o r anemia could not be evaluated adequately. Secondly, the investigation suggests that i f the n u t r i t i o n a l demands of a l i t t e r i n the pre-weaning phase of growth are pro-vided for as far as present day n u t r i t i o n a l requirements of the - 51 -baby pig are known, then a hemoglobin l e v e l of 6 to 9 grams per cent i s not s u f f i c i e n t to permit the attainment of the maximum genetic growth potential of the l i t t e r . The present study w i l l be an attempt to demonstrate the v a l i d i t y of the above hypotheses and show that by feeding a well-balanced creep r a t i o n and supply-ing requirements for i r o n and copper, the genetic growth potential of any suckling p i g l e t can be achieved. Iron anemia i s a c r i t i c a l problem where p i g l e t s are raised i n dry-lot without access to s o i l or other i r o n supple-ments. The foremost reason why ferrous anemia i s such a c r i t i c a l problem under these conditions i s that the sow i s only able to metabolize very minute amounts of i r o n across the mammary gland, hence the i r o n content of the mother's milk i s very low. Since sow's milk i s the sole source of i r o n and energy available to suckling p i g l e t s i n dry-lot for the f i r s t four to f i v e weeks u n t i l some form of creep feeding i s begun, there r e s u l t s a severe ferrous anemia arid hence a retardation of growth about the tenth day from b i r t h . Even i f the suckling p i g l e t s are provided with s u f f i c i e n t energy i n the form of a well-balanced creep ration at this period, they are unable to maintain d i -gestive and metabolic processes at a rate commensurate with the inherent growth stimulus. This can be explained quite l o g i c a l l y as i r o n Is an essential component of hemoglobin which ca r r i e s oxygen to the tissues from the lungs for c e l l u l a r metabo-lism and thus i n d i r e c t l y controls the rate of energy u t i l i z a t i o n . In order to have a precise understanding of the metabo-lism of i r o n and the part i r o n plays as a constituent of hemo-globin i n the erythrocytes, certain r e l a t i v e texts were consulted. - 52 -A summary of the present knowledge of hematopoiesis i s presented i n Appendix I . - 53 -2 . R e v i e w o f L i t e r a t u r e I n r e v i e w i n g t h e l i t e r a t u r e o n l y t h e b a s i c p a p e r s o n s w i n e f e r r o u s a n e m i a , a s r e l a t e d t o g r o w t h r a t e s o f s u c k l i n g l i t t e r s , w i l l be c o n s i d e r e d . One o f t h e f i r s t p a p e r s p u b l i s h e d o n s w i n e a n e m i a was t h a t o f McGowan a n d C r i c h t o n ( 1 9 2 3 , 1 9 2 4 ) . L i t t l e t h a t i s new h a s b e e n a d d e d t o t h e s e b a s i c d i s c o v e r i e s i n s u b s e q u e n t s t u d i e s . T h e r e c e n t r e p o r t s o n s w i n e a n e m i a h a v e s i m p l y s u p p l i e d m o r e q u a n t i t a t i v e d a t a . The o r i g i n a l p a p e r s p r o p o s e d t h a t a n i r o n d e f i c i e n c y was t h e c a u s e o f a d i s e a s e k n o w n a s " t h u m p s " , common-l y f o u n d i n s u c k l i n g p i g l e t s . P i g l e t s c o n f i n e d i n d o o r s w i t h o u t a c c e s s t o f r e s h s o i l w e r e n o t e d t o be e x t r e m e l y s u s c e p t i b l e . I n 1 9 2 9 D o y l e e t a l . showed t h a t t h e c o m p o s i t i o n o f t h e sows r a t i o n had no a f f e c t on t h e a n e m i a o f t h e s u c k l i n g p i g l e t s . H a r t e t a l . ( 1 9 3 0 ) , c o n f i r m e d D o y l e ' s ( 1 9 2 9 ) e a r l i e r w o r k , t h a t a d d i t i o n o f l a r g e a m o u n t s o f i r o n a n d c o p p e r t o t h e sows r a t i o n d i d n o t p r e v e n t a n e m i a i n t h e s u c k l i n g p i g l e t s . T h e y showed f u r t h e r t h a t i r o n was a l s o r e q u i r e d i n t h e c o w s ' m i l k t h a t was g i v e n l a t e r a s a s u p p l e m e n t t o t h e s e same p i g l e t s . T h a t m i n u t e q u a n t i t i e s o f c o p p e r a r e r e q u i r e d f o r t h e t r a n s f o r m a t i o n o f i r o n i n t o h e m o g l o b i n was d e m o n s t r a t e d b y E l v e h j e m ( 1 9 2 5 ) , H a m i l t o n e t a l . ( 1 9 3 3 ) a n d o t h e r s . G u b l e r L a h e y e t a l . (1952) p r o v e d t h a t a c o p p e r d e f i c i e n c y i n p i g s w a s i n d i s t i n g u i s h a b l e f r o m a n i r o n d e f i c i e n c y a n d a s h a s b e e n shown b e f o r e , no l e v e l o f a d m i n i s t e r e d i r o n w o u l d p r e v e n t t h e a n e m i a . T h e w o r k o f S i n c l a i r ( 1 9 4 7 ) , d e m o n s t r a t e d t h a t b y a d m i n i s t e r i n g c o p p e r a n d i r o n s a l t s t o s u c k l i n g p i g s , h e m o g l o b i n - 54 -l e v e l s of 8 to 10 grams per cent could be establ ished and anemia prevented. This treatment resul ted i n a weaning weight of 28 pounds at 8 weeks post- farrowing. Draper et a l . (1949) demonstrated the e s s e n t i a l i t y of copper i n r a i s i n g hemoglobin l eve l s i n suckling p i g l e t s ; and, perhaps of greater importance, recognized that ear ly treatment with i r o n and copper was e s sent ia l to prevent the onset of anemia Draper a lso noted, as d id Braude (1949), that hemoglobin l eve l s were far higher where suckling p i g l e t s had access to fresh s o i l than under any experimental treatment. Work with the rat by Hauk et a l . (1946) has p a r t i a l l y explained the demand by the hematopoietic system for copper over that of i r o n , for i t appears that th i s system i s able to r e t a i n greater quant i t i e s of absorbed i r o n . On the basis of the foregoing review i t i s evident that c e r t a i n de f i c i enc i e s exist i n published f indings on the inf luence of anemia on maximum growth r a t e . The de f i c i enc i e s i n these f indings have a r i s e n from the experimental designs i n which: (1) Hemoglobin determinations were conducted on ex-perimental l i t t e r s but weekly weight data on these same l i t t e r s were not recorded, (2) Growth data "of experimental suckl ing p i g l e t s were recorded from b i r t h to 56 days, a creep r a t i o n was before the l i t t e r at 3 weeks post-farrowing and hemoglobin l eve l s of 6 to 8 grams per cent were es tabl i shed . These hemoglobin l eve l s were bel ieved to allow experimental l i t t e r s to a t t a i n maximum growth r a t e . - 55 -( 3 ) Hemoglobin levels of 14 grams per cent were es-tablished i n the suckling l i t t e r s , weekly weight data of these l i t t e r s was recorded, and a creep feed of some sort was provided at b i r t h . In most cases these animals f a i l e d to reach their genetic potential for maximum growth rate because the creep feed was low i n energy or protein per unit weight and thus did not meet the requirements demanded for a rapid gain. That the second experimental design i s i n v a l i d was well demonstrated by the writer under conditions of commercial'.swine production where hemoglobin l e v e l s were taken i n the f i e l d on numerous l i t t e r s subjected to two di f f e r e n t anemia treatments (Waldern and Wood ( 1 9 5 D ) . The f i r s t treatment i n 1951-A was the administration of iro n pyrites every t h i r d day per os to suckling p i g l e t s u n t i l four weeks a f t e r b i r t h followed by a l i b e r a l sprinkling of the pyrites on the creep feed u n t i l wean-ing. The second treatment, 1 9 5 1-B, was the administration per os every t h i r d day, for 3 3 days, of 1 cubic centimeter of an iron-copper sulfate solution containing 40 mgms. of ir o n and 8 mgms. of copper. The resul t i n g growth differences are shown i n Table XV. The second treatment, where hemoglobin l e v e l s reached 1 2 to 14 grams per cent as compared to the f i r s t treatment where le v e l s ranged from 4 to 8 grams per cent, resulted i n an increase of nearly 6 pounds at weaning.* k Hemoglobin l e v e l s were measured with a Dare Hemoglobinometer. - 56 -Table XV: A COMPARISON OF WEANING WEIGHT OBTAINED WITH TWO DIFFERENT ANEMIA TREATMENTS (WALDERN AND WOOD 1951). Weight Group 1951/A 1951-B i n Pounds Per Cent of' Per Cent of Hogs at Weight Hogs at Weight Under 16 1 .32 16 - 20 4 . 9 6 1 . 3 2 21 - 25 1 5 . 6 0 6 . 3 1 26 - 30 3 1 . 2 2 1 1 . 3 0 31 - 35 24 .11 1 9 . 2 7 36 - 40 1 6 . 3 1 3 2 . 2 3 41 - 45 5 . 6 7 1 6 . 2 8 46 - 50 .71 8 . 3 1 51 - 55 1.42 3 . 0 0 56 - 60 . 6 6 No,.of Hogs - 141 301 Mean Weaning Weight 30.74 l b s . 3 6 . 5 6 l b s . Weight Group 1951-A 1951-B Under 36 l b s . 75.89 3 9 . 5 2 36 lbs. & over 24.11 60.48 100 100 The above considerations provided incentive for further investigation of p i g l e t hypoferrous anemia when thi s condition was the l i m i t i n g factor to growth. - 57 -3 • Experimental Procedure A t o t a l of 51 p i g l e t s , representing six d i f f e r e n t l i t t e r s were submitted to various anemia treatments. The f i r s t l i t t e r of ten pigs represented a preliminary inve s t i g a t i o n to permit f a m i l i a r i z a t i o n with hematological techniques. While i t may have been desirable to keep a l l i n d i v i d u -als of a l i t t e r on the same treatment, and then compare the re-sults of d i f f e r e n t treatments for a number of l i t t e r s s t a t i s t i -c a l l y , i t was not possible since the number of animals and f a c i l i t i e s available were quite l i m i t e d . Hemoglobin leve l s were determined by the a l k a l i n e hematin spectrophotometric method of King (194-7). Both Beckman and Coleman spectrophotometers were used. The l i t t e r s were treated at b i r t h as follows: ( 1 ) Experimental L i t t e r No. 1 , of seven pigs, was divided into three groups: (a) Three p i g l e t s received 1 c.c. of an iron-copper solution containing 2 0 mgm. of ir o n and 4 mgm. of copper per c.c. by mouth d a i l y . (b) One p i g l e t served as a control and received no treatment, (c) Three p i g l e t s were implanted subcutaneously just below the ear with p e l l e t s containing 1 7 5 mgms. of i r o n . ( 2 ) L i t t e r No. 2 of 6 p i g l e t s , L i t t e r No. 3 , of 8 p i g l e t s and L i t t e r No. 4 of 8 p i g l e t s were each divided into equal l o t s and treated as follows: (a) Two pigl e t s received no treatment. - 58 -(b) Two pi g l e t s were given 1 c.c. by mouth d a i l y of an ir o n and copper solution as mentioned i n (la) above. (c) Two pi g l e t s received 1 c.c. of the same solution as i n (2b) by mouth at the t h i r d day only. (d) Two pig l e t s were given an intramuscular i n j e c t i o n i n each hind leg of \ c.c. doses of iron suspended i n peanut o i l with aluminum monostearate as base. The amount of iro n i n each cubic centimeter administered i n the i n j e c t i o n varied between l i t t e r s . L i t t e r No. 2 received 300 mgms. of ir o n per cubic centimeter i n each i n j e c t i o n . L i t t e r No. 3 received 250 mgms. of i r o n plus 15 mgms. of copper. L i t t e r No. 4 received 250 mgms. of iron and only . 7 mgms. of copper. (3) The f i f t h l i t t e r of ten pigs were a l l given i r o n and copper o r a l l y from b i r t h d a i l y . A. high energy creep rat i o n was before the pig l e t s of a l l groups from two weeks onward. Hemoglobin values were determined weekly from b i r t h u n t i l weaning at eight weeks, while red c e l l counts were de-termined weekly only u n t i l the end of the fourth week. Complete data as to preparation of solutions, hemo-globin and red c e l l techniques, have been covered i n f u l l i n the undergraduate essay of Winteringham ( 1 9 5 3 ) . - 59 -4. Results. Complete weight data for the f i v e experimental l i t t e r s , from b i r t h to weaning are presented i n Tables XVI to XX. Weighing procedures, care of p i g l e t s , etc. of the l a s t four l i t t e r s plus relevant growth data have been presented i n the undergraduate essay of Bouwman (1953). Growth rate constants to weaning as calculated by the method of Brody (1945) are presented i n Table XXVI and Table XXVII. The s u i t a b i l i t y of t h i s method of growth rate expression w i l l be discussed i n Part II of t h i s t h e s i s . Hemoglobin levels and red c e l l counts are presented i n Table XXI to XXV. Figures VII to XI represent the results graphically. A r i t h - l o g growth curves of pigs number 200 to 249 are presented i n Appendix I I . Table XVI: WEIGHT IN POUNDS OF UTTER NO. 1 FROM BIRTH TO 54 DAYS, PIG TREATMENT AGE IN DAYS NO. 1 1 6 2 12 15 1 8 21 *L 30 33 36 32 42 hi 79 Pelleted 3.6 3.6 5.2 7.2 9.3 9.7 10.6 10.7 11.2 11.9 13.5 13.7 13.6 16.3 18.0 20.5 26.0 32.0 8 0 Pelleted 3.6 3.6 h.9 6.6 8.7 9.2 9.7 9.5 9.1* 10.5 12.2 13.5 13.2 16.1 18.6 19.1 25.5 30.0 81 Pelleted 3.8 3.8 lu7 6.1 7.8 8.9 9.9 10.1 10.8 11.8 13.5 15.3 15.6 16.4 18.0 20.2 29.0 35.5 82 Iron & Copper oral - daily 3.3 2.8 h.k 6.3 8.8 9.0 10.6 11. U 13a 1UJ. 15.8 18.0 17.6 17.0 19.3 21.5 28.5 35.0 83 Iron & Copper oral - dally 3.5 3.7 5.2 6.0 7.0 7.6 8.9 10.0 11.1 12.9 1 W 16.0 16.9 18.7 a„5 22.5 28.5 35.0 8U Iron & Copper oral - daily 3.7 luO 5.1 6.0 7.8 8.0 9.5 10.5 12J. 13.3 14.5 17.0 17.4- 20.4 23.2 25.7 32.0 36.0 85 Control 3.5 3.6 lw8 6.9 9.0 10.0 10.9 11.2 12.0 13.0 15.0 16.0 17.9 20.0 — 24.0 30.0 32.0 Table XVII: WEIGHT IN POUNDS OF LITTER HO. 2 FROM BIRTH TO 57 DAYS. PIG TREATMENT AGE IN DAYS NO.  Birth 3 6 9 1 £ l £ l 8 a _ 2 5 2 j > 3 3 3 2 . & U5 kg. 53 200 Iron & Copper 1.6 2.2 3.U 3.8 U.6 5.U 6.3 7.2 :8.ii 9.U 10.U 11.2 12.0 13.8 16.8 16.5 18.1 once orally 201 Intramuscular 2.L 3.0 L.3 5.1 6.1 7.0 7.9 9.1 10.7 12.2 lh.0 15.5 16.3) 18.8 2L.5 21.5 23.5 Injection 20U Iron & Copper 2.6 3.3 U.6 U.3 5.5 6.3 7.0 6.U 6.6 7.5 8 .9 11.0 12.2 15.7 19.7 20.0 23.5 once orally 205 Iron & Copper 2.6 3.1 U*2 U.5 5.1 5.7 6.6 7.9 9.7 10.8 12.8 15.3 17*2 a .7 26.3 25.2 27.3 oral daily 206 Control 2.1 3.1 U.7 5.U 6.5 6.6 7.7 8.5 8.7 9.8 12.3 15.2 17.7 21.8 26.0 25.0 27.3 207 Iron & Copper 2.U 3.1 U.U U.8 5.9 6.5 7.7 9.3 11.2 12.5 llu9 17.8 20.L 25.0 29.0 32.5 3U.0 oral daily Table XVIII: WEIGHT IN POUNDS OF LITTER NO. 3 FROM BIRTH TO 57 DAYS. PIG TREATMENT AGE IN DAYS NO. .  Birth 3 6 ^ 1 2 l 5 l 8 a 2 5 ^ 3 3 3 ? | | i g l £ 2 3 a 211 Iron & Copper 2.5 3.6 5.1 6.7 8.7 10.1 ll.U 12.6 13.8 lh.5 15.8 17.3 17*5 18.0 20.5 23.0 25.6 once orally 212 Control 2.0 2.8 3.2 3.6 li.8 5.7 6.7 8.0 9.U 9.8 10.ii 13.0 13.0 lU.O 16.1 17.9 20.5 213 Intramuscular 2.8 U.2 5.6 6.9 9.2 10.6 12.U 1U.0 16.1 17.6 20.0 22.6 23.3 23.5 27.0 30.0 32.6 1 Injection ON 21U Iron & Copper 2.2 3.2 3.7 5.U 7.0 8.U 9.7 11.2 12.8 13.6 15.5 18.3 18.5 19.3 23.0 25.0 27.6 ' once orally 215 Iron & Copper 2.6 3.9 5.6 7.6 10.0 11.6 13.5 15.3 17.7 20.0 22.9 27.0 27.5 29.5 33.6 32.5 U2.2 oral - daily 218 Iron & Copper 2.8 lu3 5.9 7.5 9.6 11.3 13.3 1U.9 17.U 20.U 23.0 2k.O 26.0 27.3 30.5 33.5 36.9 oral daily 220 Intramuscular 2.5 3.7 U.8 5.7 7.2 8.6 9.9 11.7 13.1* 15.U 17.2 18.7 19.0 2T.0 23.0 25.5 27.U Injection 221 Iron & Copper 2.3 3.7 5.0 6.3 7.8 8.7 10.7 10.9 12.2 12.7 lU.0 15.7 16.0 17.0 20.5 23.5 25.8 once orally Table XIX: WEIGHT IN POUNDS OF LITTER NO., It FROM BIRTH TO 57 DAYS. PIG TREATMENT NO. Birth 3 6 £ 12 1 2 18 230 Control 2.0 2.9 3.3 U.3 5.9 7.3 7.6 231 Iron & Copper once orally 1.3 1.8 2.U 3.6 U.9 6 a 7.0 232 Intramuscular Injection 2.5 3.5 li.lt 5.9 7.3 9.2 10.0 23U Iron & Copper oral - daily 2.0 2.8 3.5 ii.9 6.0 7.5 9 a 236 Iron & Copper oral daily 1.6 2.0 2.7 3.k lu5 6.0 237 Control 3.2 U.3 5.6 7.5 9.0 $0.8 11.6 238 Iron St Copper once orally 2.7 3.5 U.8 5.3 6.7 7.9 8.7 239 Intramuscular Injection l i 8 2.7 3.6 5.0 6.5 8.0 8.8 AGE IN DAYS 21 2£ 29_ 33 3Z i i 53 7.7 9.0 10.0 11.0 13.0 15.5 19.0 a.6 25.0 27.5 8.0 9.1 10.0 9.6 10.8 10.9 llu9 16.6 19.0 a .6 10.6 12.9 llu3 15.5 17.5 19.5 23.5 25.7 29.0 32.5 10.8 12.9 15.U 15.6 16.9 16.1 21.7 25.8 29.0 32.5 8.5 9.0 9.6 10.1 10,6 10.5 12.2 1U.3 18.5 13.0 15.0 16.5 17.5 19.6 22.0 27.6 31.U 35.0 38.5 9.8 10.1 10.U 10.5 l l . l i 12.0 16.3 19.0 22.5 2U.6 9.3 10.9 11.2 10.1; 10.6 10.7 13.5 llu9 17.0 19.5 Table XX: WEIGHT IN POUNDS OF LITTER NO. 5 FROM BIRTH TO 57 DAYS. PIG TREATMENT AGE IN DAYS NO. ' 2 4 0 t H 21*3 " 21*1* 21*5 21*6 fl) 21*7 | 21*8 * 2U9 & Birth 3_ 6 2 12 18 21 & 22 32 32 1*2 a 2.6 3.2 3.1* h.h 5.8 7.1* 9.0 10.0 12.8 15.1* 17.5 18.0 21.0 2l*.0 26.0 29.0 32.0 3.3 1*.2 6.1 8.0 10.0 11.8 13.5 1U.5 17.0 20.1* 22.0 21*.0 26.0 29.0 32.0 31.0 35.0 3.2 3.8 6.0 6.1* 7.1* 9.1 11.0 12.5 15.0 18.1 a . 5 22.0 26.0 29.0 32.0 33.0 36.0 3.0 3.8 5.0 6.6 8.2 9.6 12.3 12.6 15.1* 18.5 21.5 23.0 26.0 29.0 31.0 33.0 38.0 3.1* l*.l 5.9 7.3 9.0 10.8 12.5 •13.6 15.8 18.0 21.0 22.0 25.0 28.0 32.0 33.0 37.0 3.3 ii.2 6.2 8.1 9.9 11.7 13.0 1U.U 17.5 20.6 25.0 2U.0 27.0 30.0 33.0 32.0 38.0 3.3 3.8 5.1* 7.2 8.8 10.5 12.2 13.0 15.3 17.5 19.5 22.0 21*.0 27.0 30.0 30.0 35.0 2.5 2.7 1*.0 5.3 6.7 8.1 9.6 10.5 12.5 ll*.6 17.0 18.0 19.0 20.0 23.0 25.0 27.0 3.0 3.7 U.8 5.5 7.0 8.3 9.6 10.1* 12.8 15.0 18.0 18.0 20.0 2lu0 26.0 25.0 28.0 2.1 2.5 l * .o 5.3 6.7 8.1* 10.0 11.0 1U.0 17.7 20.5 23.0 25.0 30.0 33.0 33.0 38.0 ON Table XXI: ERYTHROCYTE COUNTS AND HEMOGLOBIN LEVELS LITTER NO.l PIG TREATMENT DAYS NO. 7 12 1£ 28 31 RBC~ Hb iRBC Hb RBC Hb RBC Hb _Hb _ 79 Pelleted U.08 3.70 3.79 U.ll 7.5 U.7 U.8 7.3 12.1 7.9 80 Pelleted 3.90 U.00 U.13 6.03 7.2 5.5 U.0 7.9 13.U 7.9 . 81 Pelleted U.35 . U.26 U.31 . 5.30 8.0 5.3 5.3 8.3! 11.0 6.U 82 Iron & Copper 3.52 U.20 5.70 6.20 oral - daily 9.3 8.U 9.5 U . 8 12.1 8.5 83 Iron & Copper U.29 U.70 5.30 5.10 oral - daily 10.3 8.3 8.6 11.8 13.U 9.1 8U Iron & Copper 3.U9 5.20 5.82 5.16 oral - daily 9.1 ,'; 9.U 8.6 10.2 ,13.U 6.8 85 Control U.OU 3.UU 3.85 U.6U , 9.1 U.0 U.7 5.5 7.7 5.2 RBC - Number of red blood cells expressed in millions of cells per cubic millimeter. (10" cells per mm.3) Hb - Grams of hemoglobin expressed as grams per 100 cubic centimeters of blood, (gms per 100 cc.) ON Table XXII: ERYTHROCYTE COUNTS AND HEMOGLOBIN LEVELS LITTER NO, 2 PIG TREATMENT DAYS NO, • 1 3 6 13 20 22 & k2 k3 $2 & RBC RBC Hb RBC Hb BBC Hb Hb 5E Hb Hb 200 Iron & Copper 2.90 3.22 2.L8 2.20 a once orally U.7 3.7 5.8 U.8 3.8 £ 7.8 12.k -p 201 Intramuscular 3.38 L.30 3.25 3.26 £ Injection 5.0 lu9 7.5 5.7 h.3 .2 7.8 9.1* 20U Iron & Copper 3.58 U.U8 3.78 h.80 M once orally 6.2 5.1 11.6 9.3 8.7 * 12.8 12.U 205 Iron & Copper 3.56 U.18 U.91 3.68 S 9 oral daily 6.3 7.1 1U.5 13.5 13.9 h * H . 7 13.5 P. 206 Control 3,kk 3.78 3.38 3.32 & U.5 3.6 8.2 9.9 l l . U ° 12.8 1U.U <* 207 Iron & Copper 3.52 U.58 U.92 5.U6 § oral r daily 6.U 6.9 16.2 13.3 13.3 A 12.8 13.5 ON ON Table XXIII: ERYTHROCYTE COUNTS AND HEMOGLOBIN LEVELS LITTER NO. 3 PIG TREATMENT DAYS  NO.  1 3 7 1U a 28 31 31 ^ | M RBC" Hb RBC Hb RBC Hb RBC Hb Hb Hb Hb Hb 211 Iron & Copper 3.U8 2.12 2.20 3.05 * once orally U.7 8.2 5.9 5.0U g # 6.2 8.1* 11.0 12.0 a) ro 212 Control U.28 3.56 3.IU 3.08 * 5.2 9.5 6.7 U.3 cS 10.2 11.7 11.7 13.6. -p r>-213 Intramuscular 3.98 2.8U U.0U . U.02 '£© Injection 5.0 10.6 8.2 10.0 ^ 10.2 10.0 l l . U 13.6 •H ZLU Iron & Copper U.26 ' 2.70 3.06 3.18 § once orally 5.2 8.5 5.7 6.2 | 10.2 12.8 11.0 11.7 21$ Iron & Copper 3.82 3.72 3.00 U.26 oral - daily 5.2 15.1 15.9 13.2 * 13.6 13.6 l l . U 12.0 a8 Iron & Copper U.28 U.2U 5.U6 , U.92 £ oral daily 6.2 15.1 15.6 13.6 J 15.6 1U.8 11.U 12.0 220 Intramuscular 3.98 3.18 3.92 3.78 % Injection U.6 12.1 l l . U 9.U | 12.8 12.8 l l . U 12.8 2a Iron & Copper 3.50 2.9U 2.U3 2.62 once orally U.7 7.5 6.9 5.7 jf 8.U 10.7 11.0 12.0 Table XXIV: ERYTHROCYTE COUNTS AND HEMOGLOBIN LEVELS LITTER NO. U PIG TREATMENT DAYS NO.  1 3 6 13 20 29 30 38 ]i£ 2^ |9 — ~ RB(T Hb RBC Hb RBC Hb RBC Hb Hb Hb Hb | 230 Control 3.18 2.80 2.72 U.08 8.U 6.U U.7 3.7 5.0 10.0 10.0 10.2 231 Iron & Copper 3.8U 2.58 2.20 3.98 once orally 10.0 7.8 U.7 3.7 U.7 10.0 10.9 12.U 232 Intramuscular 2.90 2.58 2.6U U.01 Injection 8.U 7.5 6.U U.3 ^ 5.0 9.3 9.3 9.6 3 23U Iron & Copper 3.78 U.78 U.62 U.56 a oral daily 10.6 lU.8 12.U lU.8 " 15.3 1U.U 1U.0 lU.8 236 Iron & Copper 3.60 U.26 U.32 U.U2 §3 oral daily 9.6 11*3 11.3 lU.8 3 15.3 1U.U 12.U 12.0 •8 237 Control 3.56 3.38 3.1iU 2.92 g 10.0 8.1 5.5 3.9 £ 5.0 9.3 8.7 10.9 238 Iron & Copper 3.05 2.92 2.62 U.06 once orally 8.U 6.9 5.5 U.1 6.2 10.0 11.3 12.U 239 Intramuscular 3*52 3.0U 2.86 3.22 Injection 10.2 8.1 6.U 5.3 5.3 7.8 8.1 9.6 ON 00 Table XXV: ERYTHROCYTE COUNTS AND HEMOGLOBIN LEVELS LITTER NO. 5 TREATMENT DAYS 1 J_ l i 22 22 3 6 3 ! U U 2 0 2 7 _ RBC Hb RBC Hb RBC Hb RB£ Hb Hb Hb Hb Hb_ 3.86 4.26 4.Wi 4.68 13.2 14.0 13.2 14.0 13.2 13.2 13.2 13.2 9 3.44 3.70 4.62 4.42 « 11.3 11.6 1U.0 13.5 10.2 g 12.8 13.2 14.0 • 3 g 3.62 3.60 4.20 5.10 g £ 12.0 11.6 13.2 14.0 11.6 g 12.8 lluO 13.5 •g 3.72 3.82 4.32 4.80 11.3 10.6 12.8 lluO 12.8 § 13.2 14.8 14.0 I 3.56 3.84 3.90 4.96 . 11.3 12.0 12.8 15.3 12.4 £ 13.2 ik.k 14.0 ° 3.20 3.66 4.18 4.28 * 10.0 11.3 13.5 ' 14.0 11.6 & 13.5 lh.h 14.0 JLU.U J-L.J XU.U J.X.O £3.92 3.72 4.92 4.62 6 8 12.4 12.0 15.3 14.Q 11.6 g 12.4 12.8 13.5 o 2 3.62 3.92 4.64 4.02 M 11.3 13.2 • 14.0 14.8 12.4 13.2 14.0 14.0 3.76 4.22 4.84 4.32 12.0 13.5 14.0 14.4 11.6 13.2 13.5 lli.0 3.58 3.64 3.96 4.64 9.0 10.6 12.8 12.4 11.6 11.6 11.3 12.0 ON VO - 70 -Table XXVI: GROWTH RATE CONSTANTS LITTER NO. 1 PIG NO. TREATMENT ft K - l ft K-2 ft K-3 79 Pelleted 10.545 1.704 4.598 80 Pelleted 9.804 1.737 4.561 81 Pelleted 7.990 2.787 5 . 6 5 0 82 Iron & Copper or a l - d a i l y 12.724 3.851 4.814 83 Iron & Copper o r a l - d a i l y 6 . 3 0 1 4.136 4.045 84 Iron & Copper or a l - d a i l y 7.420 4.188 4.039 85 Control 10.181 2.772 3.227 K - Instantaneous percentage r e l a t i v e growth rate per day. ft - The growth constants K - l , K-2 and K-3, for the p i g l e t s 79 to 85 apply over nearly i d e n t i c a l chronological time i n t e r v a l s . K - l o 0 to 10 days post-farrowing. K-2 - 11 " 25 •» " " K-3 - 26 » 56 1 1 " " im'.ri *»" mr* »" i - 76 -5 . Discussion of Results. Prom the graphs and tables i t i s possible to obtain a clear picture of the hematopoietic response a f f e c t i n g growth rate under the d i f f e r e n t treatments. The trend exhibited by those animals receiving iron and copper d a i l y by mouth was a sharp r i s e i n hemoglobin concen-t r a t i o n to 14 grams per cent for the f i r s t f i f t e e n days, followed by a s l i g h t decline, then a l e v e l l i n g off to a constant value of 1 2 to 13 grams per cent. This trend may be because hematopoietic mechanisms are f u n c t i o n a l l y at a maximum by the f i f t e e n t h day while the blood volume continues to increase; thus the hemato- . p o i e t i c mechanisms cannot keep pace. Of the p i g l e t s receiving a d a i l y supply of iron and copper Numbers 2 3 6 and 247, non-anemic animals, exhibited very slow growth rates to weaning at 5 6 days post-farrowing, which were probably very close to t h e i r actual genetic p o t e n t i a l . I f energy had been a l i m i t i n g factor, the post-weaning growth curves as plotted on semi-log paper would have shown a sharp increase when these animals were put on s e l f - f e e d . In other words the growth rate as represented by the growth constant K would have been greater following weaning than before weaning. This was well demonstrated by other animals i n t h i s experiment who were anemic, e.g. Pig Numbers 2 0 0 , 2 2 1 , 2 3 1 and 2 3 8 . For a l l other treatments, even though there was a delay i n the onset of anemia, there was a d e f i n i t e effect causing suppression of maximum growth rate. The suppression was not evident u n t i l the tenth day or thereafter. In t h i s same period energy was not a l i m i t i n g factor i n most cases as - 77 -a proven creep ra t i o n was before the p i g l e t s from two weeks onward. Thus i n the absence of i r o n the p i g l e t was unable to u t i l i z e available food, whether i t was sow's milk or creep feed. Not u n t i l the fourth week or onward, when the p i g l e t s were ph y s i o l o g i c a l l y able to consume s u f f i c i e n t creep feed, supple-mented with i r o n , or when ir o n and copper were administered by mouth, did the hematopoietic system respond with increased hemoglobin l e v e l s . This response was followed by a sharp i n -crease i n feed consumption and hence i n growth rate, r e s u l t i n g i n breaks i n the growth curves giving r i s e to growth constants or K values which were greater than those of the iron-copper deficiency period. The increased growth rate tended to return the p i g l e t to i t s normal or genetic growth p o t e n t i a l . This phenomenon Is well i l l u s t r a t e d by the following p i g l e t s : Number 7 9 , 8 0 , 8 1 , ' 8 5 , 2 0 0 , 2 0 1 , 2 1 1 and to a lesser extent by others. Though the tendency was to return the p i g l e t to i t s genetic growth p o t e n t i a l , i t was impossible for the animal to wean at eight weeks near a maximal l e v e l of 4 5 pounds due to the lag i n growth at the onset of anemia. A. weaning weight of 4 5 pounds at eight weeks from b i r t h i s quite possible under i d e a l con-d i t i o n s of feeding and management provided the upper genetic l i m i t for weight at t h i s age i s not a suppressing f a c t o r . The oral administration of i r o n and copper at the t h i r d day only, had l i t t l e a f f e c t i n warding o f f anemia, but the return of hemoglobin l e v e l s to normal when i r o n and copper was administered by mouth at 2 8 days was faster than f o r those p i g l e t s that received no supplementation whatsoever. The above was well demonstrated by the pelleted p i g l e t s , Numbers 7 9 ? 8 0 , - 78 -8 1 ; when they began to consume creep rati o n i n s u f f i c i e n t quantities to supply the required i r o n and copper, the hemoglobin l e v e l s rapidly returned to normal. The pigs injected i n t r a -muscularly also f i t t e d the above pattern. Thus one would suggest that the hematopoietic system did gain i n some way from the prophylactic treatments. The use of an intramuscular i n j e c t i o n of complex iron-copper monostearate as a source of iro n and copper for hemoglobin formation warrants some note as indicated by the data of Figure IX. Figure VIII shows, as might have been ex-pected, that l i t t l e hematopoietic response resulted from the intramuscular i n j e c t i o n of ir o n , but i n L i t t e r No. 3 (Figure IX) where 1 5 mgms. of copper was introduced with the iron, considerable hematopoietic a c t i v i t y was shown, i n the form of higher hemoglobin l e v e l s . Severe atrophy of one leg of two of the pigs i n L i t t e r No. 3 occurred when copper was injected with the i r o n at the 1 5 mgm. l e v e l . The precise cause of the i n i t i a l inflammatory reaction and the subsequent necrosis and atrophy cannot be stated. It may have been due to an excess of copper ions, f a u l t y asepsis at the s i t e of i n j e c t i o n or to physical trauma r e s u l t i n g from the loc a t i o n at which the mixture was inje c t e d . It i s l i k e l y that a l l three factors were involved. When the amount of copper to be injected with i r o n was reduced to . 7 mgms. for the 4 L i t t e r (Figure X), the hemato-p o i e t i c response was nearly i d e n t i c a l with that of L i t t e r No. 2 (Figure VIII). Thus the additional copper must have been re-quired for increased hemoglobin synthesis. Even though s u f f i c i e n t i r o n and copper was given by - 79 -intramuscular i n j e c t i o n to meet growth requirements for the f i r s t 2 0 days (Venn et a l . 194-7), a sa t i s f a c t o r y hematopoietic response was not obtained and hence i t must be concluded that the injected i r o n and copper was not u t i l i z e d or metabolized at a s u f f i c i e n t rate to meet growth demands. L i t t e r No. 5 , which received i r o n and copper o r a l l y d a i l y to seven weeks, did not show a response i n the form of an increased growth rate when i t became dependent upon the creep feed as did the anemic p i g l e t s of other l i t t e r s . Instead, a steadily decreasing growth rate from b i r t h onward was noted and indicated by a decreasing K value or growth constant. This i s the normal pattern of growth for any animal or organism which has not been limited i n i t s rate of growth by the action of an e a r l i e r i n i m i c a l event. The hematological examination of the blood of the normal and anemic p i g l e t s demonstrated several points that have already been noted by other authors. The erythrocytes of the anemic p i g l e t s were f r a g i l e and hemolyzed re a d i l y , and were t y p i c a l l y microcytic and hypochromic. Another important fact has been demonstrated by the experiment; not a l l pigs that become anemic have a slow growth rate. Pig Number 2 3 7 i n l i t t e r four had no ir o n and copper supplementation yet he maintained a high growth rate showing only a s l i g h t set back i n growth. At one point his hemoglobin l e v e l dropped to 3 . 8 grams per cent yet he weaned at 5 7 days at 3 8 . 5 pounds. Just why. "he grew at a rapid rate i n the absence of s u f f i c i e n t hemoglobin cannot be explained. A s i g n i f i c a n t p r a c t i c a l result of the anemia treatments, - 80 -where the d a i l y i r o n and copper supplemented p i g l e t s are compared to the non-supplemented p i g l e t s , i s the difference i n average weaning weight at eight weeks. The former weighed 34 .5 pounds as compared to the l a t t e r at 2 5 . 9 pounds at eight weeks—an increase of nearly 10 pounds. This w i l l represent a decrease i n market age of two weeks or more when the same two groups reach 200 pounds. - 81 -6. Summary and Conclusions The problems posed were: (1) that maximum growth rate of suckling p i g l e t s could not be attained even when a high energy creep ration was availa b l e , i f hemoglobin lev e l s were below 12 to 14 grams per cent; (2) that maximum growth rate of suckling p i g l e t s or maximum response to any treatment for hypoferrous anemia i s not attainable unless a high energy creep rat i o n i s present; (3) that growth i s the ultimate c r i t e r i o n of any treatment for hypoferrous anemia. In the review of l i t e r a t u r e the above points have been overlooked by most workers doing research on hypoferrous anemia i n suckling p i g l e t s . The present experiment had ade-quately demonstrated that a l l three of the above points are important i n a study of thi s type. Of the various prophylactic measures used, a d a i l y administration of copper and ir o n produced the most s a t i s f a c t o r y growth response, further supplementing the work of e a r l i e r investigators that a constant supply of i r o n and copper i s es s e n t i a l . The experiment also indicates that intramuscular i n -jections may have promise for the control of anemia but con-siderable research i s s t i l l required on thi s problem before the method could be used i n practice. Of major interest are the weaning weights at eight weeks as affected by the various prophylactic measures. From - 82 -these weights one can r e a d i l y see the necessity of supplying a constant source of i r o n and copper to the suckling p i g l e t . With heavier weaners, age-to-market w i l l be reduced and feed and over-head costs i n the post-weaning period w i l l be lowered. The investigation also shows that further study of the pre-weaning n u t r i t i o n a l requirements of the baby pig i s ess e n t i a l to explain c e r t a i n anomalies a r i s i n g from a study of t h i s type. Treatment of hogs i n the pre-weaning phase of growth has been erroneously overlooked by investigators doing post-weaning growth studies, but the necessity of providing for maximum growth throughout the entire l i f e cycle of the hog can-not be over-emphasized, esp e c i a l l y since i n Canada, the" main problem i s to breed a bacon hog that meets a given set of hog carcass q u a l i f i c a t i o n s . Only through a complete analysis of growth and factors a f f e c t i n g growth throughout the entire l i f e cycle of the hog, can the commercial producer hope to produce an animal that w i l l meet present market standards. To j u s t i f y these claims Part II of this t h e s i s ' w i l l consider the factors that influence growth and e f f i c i e n c y of feed u t i l i z a t i o n i n Yorkshire swine i n the post-weaning period of growth. - 83 -I I I . POST-WEANING GROWTH RATE AND  EFFICIENCY OF FEED CONVERSION  OF YORKSHIRE SWINE. 1. Introduction The post-weaning growth of animals has been widely studied i n experimental designs which permitted the use of groups of animals. One of the few experiments related to in d i v i d u a l feed consumption and growth rate of the Yorkshire hog, was conducted by Crampton i n 1928. The basic finding of t h i s early work was the discovery of a difference of 40 per cent i n feed e f f i c i e n c y between individuals i n a small group. This difference was very s t a r t l i n g and c e r t a i n l y warrants further i n v e s t i g a t i o n i n the l i g h t of more recent n u t r i t i o n a l standards for the pig . Selection of breeding stock on the basis of type and weight increase alone, from group feeding t r i a l s , does not assure the selector that any chosen animal has gained e f f i c i e n t l y or economically. This method of selection may help to explain the lack of improvement i n rate and e f f i c i e n c y of gain of American and Canadian swine populations over the past f i f t e e n years, when data from d i f f e r e n t groups at Regional Swine Breeding Stations and Canadian Advanced Registry Stations, were subjected to h e r i t a b i l i t y and cor r e l a t i o n studies. At present, i n Canada, there exists a d e f i n i t e set of standards for grading market hogs. In order that the commercial hog farmer may produce market stock that w i l l meet these carcass standards, growth, feed consumption, breeding and sele c t i o n studies must be carried out on i n d i v i d u a l hogs, not on groups of animals. The f i n a l section of the present thesis involved a study of post-weaning growth rates and e f f i c i e n c y of feed con-version with Yorkshire pigs. The main objects of the f i n a l experimental studies were: (1) To study post-weaning growth rates of Yorkshire swine under more recent n u t r i t i o n a l standards. (2) To further present-day knowledge of the existence of variations i n feed e f f i c i e n c y i n a cl o s e l y r e-lated swine population where one t h i r d of the animals were fed according to t h e i r i n d i v i d u a l growth rates and two thirds were fed i n d i v i d u a l l y under conditions of i s o c a l o r i c feed intake at equal body weight. A l l pigs received the same rations over similar weight ranges. (3) To v e r i f y as f a r as possible, using metabolism and energy content of gain data for swine, Brody 1s (194-5) concepts of pre-pubertal growth; that i s to determine to some extent the v a l i d i t y of the Instantaneous Relative Growth Rate Equation K s In W2 -/hWx over the phases of l i n e a r i t y t2 " t i i n the growth pattern when body weight i s regressed against time on an a r i t h - l o g g r i d . - 85 -D e f i n i t i o n s of the following terms would c l a r i f y the discussion: (1) H e r i t a b i l i t y - A p r a c t i c a l d e f i n i t i o n of h e r i t a b i l i t y may best be given by considering the causes of differences between two animals f o r any p a r t i c u l a r t r a i t , e.g. weight for age i n swine. Differences i n t h i s t r a i t may be caused by environment (feeding, management, disease, etc.) or by inherent differences a r i s i n g from t h e i r difference i n parentage. The f r a c t i o n due to the l a t t e r source, since i t i s caused by genetic differences, i s termed the h e r i t a b i l i t y of that t r a i t (Fredeen 1952). (2) Selection D i f f e r e n t i a l - The selection d i f f e r e n t i a l i s the difference between the average merit of the animals selected for breeding and the average merit of the entire group from which they were chosen. - 86 -2. Review of Literature Prom the l i t e r a t u r e , considerable data pertinent to the present study of post-weaning growth and e f f i c i e n c y of feed conversion i n the Yorkshire hog has been c o l l e c t e d . In order to present t h i s information c l e a r l y , the subject matter has been sub-divided under the following headings: (1) Heredity and Selection (2) Growth and Metabolism (3) Carcass Composition (4) Feed U t i l i z a t i o n In some cases l i t e r a t u r e reviewed under the above headings may overlap, but t h i s i s necessary f o r the continuity of the thought and development of the discussion. (1) Heredity and Selection 1. H e r i t a b i l i t y Estimates f o r Swine: The effectiveness of s e l e c t i o n f o r more rapid growth rate depends la r g e l y upon the extent to which the observed d i f f e r -ences i n growth rate are a c t u a l l y h e r i t a b l e , i n the sense that the offspring w i l l exhibit part of the su p e r i o r i t y or i n f e r i o r i t y i n growth rate which th e i r parents exhibited. I t i s expected that mass sel e c t i o n w i l l cause the mean of any population to increase i n each generation by an amount equal to the s e l e c t i o n d i f f e r e n t i a l times the h e r i t a b i l i t y . There i s common b e l i e f (Lush 195D (Dickerson 195D that many populations do not change t h i s r a p i d l y . Lush (1951) has pre-sented three possible explanations: 1. The actual h e r i t a b i l i t i e s are not as high as calculated. - 87 -2 . The inaccuracy of measuring the improvement that takes place. 3 . Actual selection pressures are lower than believed. Number two and three are believed to be the major causes of lack of improvement i n animal populations. I t i s hoped that the following discussion of the l i t e r a t u r e w i l l present some explanation of these problems as related to swine selection for rate and e f f i c i e n c y of gain from weaning to slaughter. Table XXXV presents the c o l l e c t i v e data of several investigations on h e r i t a b i l i t y estimates f o r d i f f e r e n t character-i s t i c s i n swine and other farm animals. Part of Table XXXV Is a f t e r Williams ( 1 9 5 2 ) . Lush ( 1 9 3 D » pointed out that biometrical studies of data from group feeding experiments with farm animals have generally shown a large amount of v a r i a t i o n i n the response of d i f f e r e n t animals i n the same l o t to what were supposed to be the same conditions of feed, housing and care. C o - e f f i c i e n t s of v a r i a b i l i t y of i n d i v i d u a l gains were found to average 17 per cent for swine and c a t t l e and 2 1 per cent for sheep. In t h i s same work, the r e l a t i v e gains of i n d i v i d u a l pigs and steers used i n regular feeding experiments were estimated at the be-ginning of a series of experiments by Lush and the members of the s t a f f of the Texas A g r i c u l t u r a l and Mechanical College and the A g r i c u l t u r a l Experimental Station. The most impressive finding i n these experiments was the large amount of v a r i a t i o n i n gain and also i n f i n a l estimated value of the animals that had not been foreseen by trained men who spent much time i n close study - 88 -of the experimental animals. Studies of the association between c e r t a i n r e l a t i v e s f o r growth rate i n swine indicate that the heritable portion of i n d i v i d u a l differences i n weight i s small at b i r t h but i n -creases s t e a d i l y with age, and reaches a maximum of 1/4 to 1/3 at f i v e months of age. Prom weaning to 200 pounds, the h e r i t a b i l i t y of rate of gain has been calculated to be 24 per cent by Lush (1936) using Danish progeny testing data. The Danish data, as used by Lush, records Improvements i n carcass c h a r a c t e r i s t i c s over the past 30 years by use of the performance testing programs. Length of carcass has increased from 35 to 36.8 inches and average thickness of back f a t has decreased from 1.61 to 1.34 inches. Marked changes i n rate and economy of gain have also been re-corded i n Lush's review of the Danish progeny testing data. Average d a i l y gain increased from 1.20 to 1.48 pounds and feed required per pound of gain decreased from 3.60 to 3.15» Berge (1936) determined h e r i t a b i l i t y i n Norwegian pig testing data f o r rate of gain as 52 per cent f o r Yorkshires and 20 per cent f o r Landrace. Average h e r i t a b i l i t i e s were given as: 6 per cent for weights from b i r t h to weaning, 14 per cent f o r weights at 84 and 112 days and 25 per cent f o r weights at 168 or 180 days. Improvement i n carcass c h a r a c t e r i s t i c s comparable to those reported i n Lush's (1936) data were reported. Comstock et a l . (1942) using i n t r a - s i r e regression, obtained estimates of h e r i t a b i l i t y of 0 f o r weaning weight and 14 per cent f o r 180 day weight. From an analysis of v a r i a t i o n due to s i r e and l i n e differences, Baker et a l . (1943) estimated - 89 -the h e r i t a b i l i t y of weight at b i r t h , 21, 56, 84, 112, 140 and 168 days to be 0, 4, 15, 26, 28, 19 and 25 per cent r e s p e c t i v e l y . A s i m i l a r analysis of growth data on Landrace and Chester White swine by Hetzer (1942) gave h e r i t a b i l i t y estimates f o r weight at b i r t h , 21, 56, 98, 140 and 182 days of 16, 10, 0, 33, 39 and 24 per cent respectively. A study by Nordskog et a l . (1944) for p a r t i a l l y inbred l i n e s yielded h e r i t a b i l i t y estimates f o r weight at d i f f e r e n t ages of 0 at 112 days or e a r l i e r and 21 and 27 per cent at 140 and 168 days respectively.. Similar estimates f o r rate of gain from b i r t h and from weaning to 200 pounds were respectively 21 and 40 per cent. In Whatley's (1942) study on Poland China hogs, h e r i t a b i l i t y f o r weight at 180 days was at least 30 or 40 per cent. His lowest estimate of 20 per cent was based on the f r a c t i o n of the v a r i a t i o n a r i s i n g from differences among s i r e s and his highest estimate of 62 per cent was obtained from the i n t r a - s i r e regression of progeny on dam. By averaging r e s u l t s from these same two methods, Whatley and Nelson (1942), using data on Duroc Jerseys, calculated the h e r i t a b i l i t y of 180 day weight at 23 per cent. 2. The E f f e c t of Selection i n Improving Carcass Characters. Feed E f f i c i e n c y and Bate of Gain: Krider (1946), working at the I l l i n o i s A g r i c u l t u r a l Experimental Station, selected f o r rapid growth i n one l i n e and slow growth i n another l i n e of Hampshire swine. The r e s u l t s from his s e l e c t i o n experiments indicate that differences i n - 90 -weight at 5 or 6 months of age among pigs farrowed i n the same season and from the same l i n e s of breeding are about 1/6 or 1/5 h e r i t a b l e . Heritable differences increased s t e a d i l y from 5 per cent at b i r t h to 24 per cent at 180 days, whereas the per cent of variance due to non-heritable differences between l i t t e r s decreased from 40 at b i r t h to 14 at 180 days. The non-heritable differences among l i t t e r mates accounted f o r 46 to 62 per cent of the variance i n weight at a l l ages. Actual differences i n weight between the rapid and slow l i n e at 180 days gave 23 pounds difference i n favor of the rapid l i n e . At the end of eight generations the difference was more than doubled. Substantial increase i n l i t t e r size and b i r t h weight i n favor of the rapid l i n e was obtained. Much of the l i n e difference created by the se l e c t i o n was reported as resu l t i n g from reduced performance of the slow l i n e rather than an increase i n the high l i n e . Blunn et a l . (1947) studied carcass data of Duroc Jersey swine to determine the r e l a t i v e importance of heredity and environmental factors which a f f e c t depth of back f a t , length of hind l e g , ham circumference and average d a i l y gain from,wean-ing to slaughter. The feeding period was divided i n t o two portions so that the r e l a t i o n between gain and the other characters could be studied during the growing as opposed to the fattening period. Their r e s u l t s indicated that hereditary factors accounted for 12 per cent of the variance for length of the hind l e g . Genetic correlations were not s i g n i f i c a n t but indicated, a nega-t i v e c o r r e l a t i o n between gain and depth of back f a t and length of hind l e g , and a po s i t i v e genetic c o r r e l a t i o n between gain and ham circumference. The o v e r a l l r e s u l t s indicated less genetic - 91 -but more environmental association between rapid gains and fatness. The forgoing may be true only i n cases where the animals are self fed. Dickerson (194-7) studied the genetic association of carcass character with rate and economy of gain. He concluded that differences i n rate of gain to 225 pounds due to the pigs own genes were more largely in fat deposition than i n bone and muscle growth. Rapid fat deposition and low feed requirements tended to be caused by the same genes, as evidenced by strong correlations of the sires. A combination of less activity and larger appetite was tentatively considered responsible for the hereditary association of lower feed requirements with more rapid fat deposition. Dickerson (1947) also suggested that a tendency for poorer suckling a b i l i t y was caused by the same genes responsible for rapid fat deposition on low feed requirements. The heritable portion of the variation among pigs was estimated from correlations between paternal half-sibs as about 33 per cent for weight at 180 days of age and for daily gain after weaning, and over 50 per cent for feed consumed per pound of gain. For carcass traits the estimates varied from 33 per cent for yield of lean cuts to 50 per cent for the measure of fatness and to nearly 75 per cent for the length of carcass. Dickerson et a l . (194-7) present data on two strains of Duroc Swine that had been selected for high and low individual feed requirements per pound of gain. A l l animals had been f u l l -fed a standard ration i n individual pens with concrete floors from 72 days of age to 225 pounds. To minimize inbreeding, one boar and one g i l t were selected from each of 8 l i t t e r s i n each - 92 -s t r a i n every year and sib matings were avoided. Selection i n t h e i r work was based l a r g e l y on differences between l i t t e r mates. The differences were found to be about 24 per cent h e r i t a b l e . The r e s u l t s indicated that s e l e c t i o n based on rate of gain from weaning to market weight would be nearly as e f f e c t i v e In improving economy as s e l e c t i o n based d i r e c t l y on i n d i v i d u a l feed requirements. The genetic factors that lowered feed requirements without i n -creasing rate of gain, also apparently impaired the suckling a b i l i t y of the sows. This was said to increase, i n d i r e c t l y , the post-weaning feed requirements enough to of f s e t the extra re-duction i n the pigs own inherent feed requirements. Dickerson also stated that s e l e c t i o n based on i n d i v i d u a l and l i t t e r weights at weaning would be moderately e f f e c t i v e In improving the suckling a b i l i t y of sows but r e l a t i v e l y i n e f f e c t i v e i n increasing the rate and e f f i c i e n c y of post-weaning gains. Selection rates diverged the feed e f f i c i e n c y by 25 pounds per 100 pounds of gain between the most e f f i c i e n t and least e f f i c i e n t l i n e s . The f a i l u r e of present methods of s e l e c t i o n to. improve Canadian hog carcass standards over the past f i f t e e n years has been pointed out by Fredeen (1952). The average measurements of hogs tested i n 1937 were p r a c t i c a l l y i d e n t i c a l to those tested i n recent years. 3. Recent H e r i t a b i l i t y Estimates of Certain Performance T r a i t s  i n Canadian Yorkshire Swine: H e r i t a b i l i t y of c e r t a i n performance t r a i t s i n the Canadian Yorkshire have recently been computed from the records of Advanced Registry by Fredeen (1952). The more important of - 9 3 -these, expressed as a percentage of the total variation found between l i t t e r mates, are: Age at 200 pounds live weight 55 per cent Feed per 100 pounds carcass gain 30 " " Length of carcass 40 11 " Thickness of Back Fat 40 " " Area of l o i n muscle 66 " " Total carcass score 35 " " Relative to the present study we see that age at 200 pounds liy e weight i s estimated to be 55 per cent heritable (Fredeen 1952) and feed per pound of gain to be 30 per cent heritable. By testing animals on an individual basis for feed efficiency, rate of gain, and age at 200 pounds, and starting with h e r i t a b i l i t y figures quoted as averages, i t i s believed that the he r i t a b i l i t y estimates could be raised considerably (Hammond 1950). It has been shown by Fredeen (1952) and stated by others (Lush and Dickerson 195D that present methods of selection change population trends very slowly, i f at a l l . If variations exist i n h e r i t a b i l i t y estimates for most measurable character-i s t i c s In swine as shown by Table XXXV, then why have geneti-ci s t s , nutritionists and others tried to improve age-to-market, carcass characters and feed per 100 pounds of gain by use of group experiments? It i s hoped that the present study w i l l point out some of the extreme fluctuations of heritable charac-ters (body weight, body gain and feed efficiency) i n a closely related swine population. Heritability estimates eould be higher for the measured characters i f an individual's growth - 94 -rates could be determined accurately under conditions of optimum n u t r i t i o n . I t i s believed that by use of accurate growth and feed consumption data from i n d i v i d u a l animals plus use of newer methods of measurement f o r f a t and protein i n the Intact animal to obtain composition data, that s e l e c t i o n pressures can and w i l l improve the market hog. Table XXXV: HERITABILITY ESTIMATES Cha r a c t e r i s t i c H e r i t a b i l i t y (Per Cent) Species and/or Breed Authority Rate of Gain 24 Danish Landrace Lush (1936) Rate of Gain 52 Yorkshire Berge (1936) Rate of Gain 20 Danish Landrace II Weight From B i r t h to Weaning 6 Yorkshire n Weight at 84- Days and 112 Days 14 II ti Weight at 168 or 180 Days 25 II it Weaning Weight 0 Poland China Comstock et a l . (1942) 180 Day Weight 14 n it B i r t h Weight 0 n Baker et a l . (1943) Weight at 21 Days 84 112 140 168 4 11 28 19 25 it it it ti n it ti ' tt it n it it Weight at B i r t h 21 Days 56 98 140 182 16 10 0 33 39 24 Danish Landrace and Chester White tt it it tt Hetzer (1942) tt it it II ti Table XXXV: HERITABILITY ESTIMATES Char a c t e r i s t i c Gains at 28 Days 56 84 112 Rate of Gain: B i r t h to 200 l b s . Weaning to 200 lbs, Weight at 180 Days B i r t h Weight 180 Day Weight Depth of Back Fat Length of Hind Leg Ham Circumference Average Da i l y Gain Weaning to Slaughter Body Weight at 180 Days Da i l y Gain a f t e r Weaning Feed/lb. Gain H e r i t a b i l i t y (Per Cent) 18 28 39 45 21 40 30 62 23 5 24 12 23 12-23 12-23 33 33 50 Species and/or Breed Poland China it tt it ti tt ti ti Duroc Jersey Hampshire ti Duroc Jersey tt Poland China, Danish Landrace, PC x DL PC x DL Authority Nordskog et a l . (1944) ti ti it ii it Whatley (1942) Whatley & Nelson (1942) Krider (1946) tt Blunn et a l . (1947) Dickerson (1947) Table XXXV: HERITABILITY ESTIMATES Char a c t e r i s t i c Peed/100 l b . Gain Length of Peed Period 72 Days-225 Pounds Weight at 72 Days Weight at B i r t h Y i e l d of Lean Cuts Fatness Length of Carcass Age at 200 l b s . Live Weight Feed per 100 l b s . Carcass Gain Length of Carcass Thickness of Back Fat Area of Loin Muscle T o t a l Carcass Score Overall Weaning Score Thickness Score Lowness Score H e r i t a b i l i t y (Per Cent) 26 47 9 23 33 50 75 55 30 40 40 66 35 50 15 46 Species and/or Breed Duroc Swine 11 Poland China, Danish Landrace, PC x DL 11 Yorkshire 11 it it Aberdeen-Angus Authority Dickerson and Grimes (1947) Dickerson (1947) CO -<2 Fredeen (1952) it tt Koger and Knox (1952) it C h a r a c t e r i s t i c Smoothness Score Overall Weaning Score Thickness Score Lowness Score Smoothness Score Feed Lot Gain Weaning Score Dairy Type ti II Butter Fat Percentage Live Weight at Weaning At one Year Rate of Gain 6- 9 months 9 - 1 2 12 - 15 Body Weight at 6 months it Table XXXV: HERITABILITY ESTIMATES H e r i t a b i l i t y (Per cent) 15 30 10 13 18 70 31 16 14 30 36 28 80-/99 Species and/or Breed Aberdeen-Angus it it Hereford ti Jersey II Aryshlre Jersey Progeny of Hereford Bulls n Authority Koger and Knox (1952) Knapp and Clark (195D CO 0 0 Rennie (195D Harvey (1949) T y l e r and Hyatt (1948) Rennie (1951) Knapp and Woodward (195D 10 54 84 0 5 it ii it II tt tt Dawson, Vernon, Baker and Warwick (195D Table XXXV: HERITABILITY ESTIMATES Cha r a c t e r i s t i c H e r i t a b i l i t y Species and/or Breed Authority (Per Cent) Body Weight at 6 months 15 Progeny of Hereford Bulls Dawson, Vernon, Baker and Warwick (195D B i r t h Weight 29 Shorthorn Dawson (1947) u n II t i i CO CO I - 100 -(2) Growth and Metabolism 1. A Mathematical Expression of Growth: Growth has been termed as an i r r e v e r s i b l e time change i n magnitude of the measured dimension or function (Brody 194-5). The present study w i l l not attempt an elaborate d i s -cussion or review of growth as such, as t h i s has been covered recently i n the thesis of Williams (1952), but some attempt w i l l be made to substantiate the method chosen to express growth i n the present t h e s i s , which Is that summarized by Brody (194-5). In 1922 Hammond undertook an in v e s t i g a t i o n on the r e l a t i v e growth and development of various breeds and crosses of pigs from records of the Smithfield Club's Fat Stock show. He rea l i z e d that differences i n metabolism existed between breeds and that v a r i a t i o n i n the rates of growth were due to differences i n the u t i l i z a t i o n rather than the absorption of food. Hammond stated that the growth curve was i n r e a l i t y a combined curve of the growth of various organs, each reaching a maximum at a d i f f e r -ent time. This was believed to account f o r variations i n the form of growth curves of d i f f e r e n t animals as these animals had maximum growth rates early or l a t e i n the chronological time calendar. Numerous mathematical equations have been derived by ba c t e r i o l o g i s t s , physiologists and b i o l o g i s t s to express growth i n d i f f e r e n t organisms, but Davenport (1934) has stated that growth cannot be expressed adequately by any simple equation, and presents data i n his c r i t i q u e to substantiate h i s claims. In the same year Wilson (1934) pointed out that a t h e o r e t i c a l expression i s necessary to develop a quantitative concept of - 101 -such a diverse phenomenon as growth. Asmundsen et a l . (1934), studying comparative rates of growth i n Leghorn and Barred Rock chickens, have divided the growth curve into phases, where growth rate tends to be constant, and then used any single phase as a period of consideration. They have calculated percentage growth rate from the formula: R = W2 - Wx 1 Q 0 1/2 (W2 + WX) The above equation may be c r i t i c i z e d for three reasons: (1) Weight increments i n t h i s equation are added on at discontinuous time i n t e r v a l s . (2) The denominator of the equation (1/2 (W2 + Wj)) assumes that growth i s l i n e a r throughout the entire l i f e span. (3) Time i n t e r v a l s over which the weights W2 - Wx are measured are not equivalent to phy s i o l o g i c a l time i n t e r v a l s i n the development of the animal. Another expression commonly used to express growth i s the average growth rate equation: • Average Growth Rate » W2 - Wx t 2 " t i This expression assumes that a l l animals grow at a constant rate from b i r t h to maturity which Is absurd since the composition of the gain changes as growth progresses from one of protein to one of f a t . Lerner et a l . (1938) have used equations f o r growth by e a r l i e r a u t h o r i t i e s i n establishing genetic growth constants i n domestic fowl. - 102 -I. Q s K (At - t ) : when rate of growth i s considered proportional to the time remaining for completion of growth. II. Q s K (Aw - w): when rate of growth i s proportional to the weight to be gained. III. Q = K; when rate of growth i s inversely proportional t to the elapsed time. IV. Q = K: when rate of growth i s inversely proportional w to the weight already attained. Where: K - constant t = time w = body weight At - time for completion of growth Aw = f i n a l weight Q a growth rate Brody fs collective data on growth has been presented in f u l l i n his text "Bioenergetics and Growth." (1945) The equation proposed by Brody to represent growth from birth to puberty and used in this thesis for measurement of growth rates i n Yorkshire swine has been termed the "Instantane-ous Relative Growth Rate Equation" and i s based on reaction rates. The equation has been developed quite logically, as i t i s well known that growth in general i s a series of biochemical reactions obeying the principle of mass action for a f i r s t order reaction. This means that the speed of growth or the speed of a chemical reaction i s directly proportional to the mass or the number of available units entering Into the reaction at any given instant. - 103 -In terms of the physiologist, growth rate i s d i r e c t l y proportional to the active protoplasmic mass of the animal body. I t must also be remembered that growth rate decreases from the moment of con-ception due to a decrease In active metabolic mass r e l a t i v e to t o t a l mass, thus the value of any derived growth rate constant i s ever decreasing, since growth has been calculated as an ex-ponential function. Now i t has been demonstrated that the rate of growth of an organism or an animal i s d i r e c t l y proportional to the concentration at any given instant, but the concentration i s ever changing and i n the next instant has increased by a d e f i n i t e increment. In order that these i n f i n i t e s i m a l i n c r e -ments be measured, use i s made of the calculus: dw - Kw or K = dw dt dt w Where dw i s the i n f i n i t e s i m a l change i n body weight (w), and dt i s the i n f i n i t e s i m a l period of time (t) over which the I n f i n i t e s i m a l change i n body weight occurred. K i s the instantaneous r e l a t i v e growth, that i s , r e l a t i v e to the body weight (w). K dt - dw w Now to evaluate the expression we integrate between the l i m i t s A and w, where; A = weight at time 0 (conception) w = weight at time t ft K dt = J dw / t 0 /Aw Kt = In w - In A K - In w - In A t - 104 -Where t Is the time i n t e r v a l designated as t 2 - t x . For purposes of c a l c u l a t i o n the equation i s better expressed as: K s In w2 - In wx t£ = t i or K = 2.303 (log w2 - log wx) tr\ - t j By using napierian logarithms the value of the Instantaneous Relative Growth Rate Constant "K" when multi p l i e d by 100 reads as percentage growth. By removal of napierian logarithms from the following equation; lnw - E t t In A, whieh i s e s s e n t i a l l y the equation Kt, for the straight l i n e : y = a x-hb, i t becomes: w • Ae which also represents the equation f o r a monomolecular reaction. Kt As pointed out by the preceeding equation, the equation W s Ae represents a straight l i n e when time i s regressed against concen-t r a t i o n on an a r i t h - l o g g r i d . Therefore, any growth reaction which w i l l give a straight l i n e when plotted on an a r i t h - l o g g r i d w i l l have the reaction rate K r In w2 - In wx. Since *2 " t x the active metabolic mass per unit of body weight of any animal i s continually decreasing due to changes i n body composition, one would expect d e f i n i t e phases of l i n e a r i t y i n the growth curve when plotted on a r i t h - l o g paper. Williams (1952) has plotted growth data of Hereford b u l l s , the Labrador r e t r i e v e r , B l a c k t a i l deer, Wistar White rats and Yorkshire swine on a r i t h - l o g paper and established the ex-istence of phases of l i n e a r i t y i n the growth curves of these species. From these growth data, Williams has calculated the - 105 -instantaneous r e l a t i v e growth constants f o r the phases of l i n e -a r i t y from the equation K r In W2 - In w^  and by the nu-t£ 1 ti merical values obtained he has established, to some extent, the v a l i d i t y of Brody*s equation. Zucker et a l . (1942), i n a c r i t i c a l review of growth, present growth equations of thirteen investigators. Most of these equations were found to be inadequate for an i d e a l expression of growth. Brody*s equation f o r growth i s c r i t i c ! s i z e d on the basis that post-weaning growth, as they measured i t i n the r a t , when plotted on a log-log g r i d gave a straight l i n e throughout the entire post-weaning period. They present the equation t l n w : -K^ + l n A 1 or w = Ae - K^, where: w a weight t r age from b i r t h A = f i n a l weight K = growth constant which was found to f i t the growth pattern of well-nourished rats from weaning to mature weight. Murphy et a l . (194-8) and Mayer (1948) have studied growth rates i n the r a t . Growth data from both investigations plotted on a log-log g r i d have shown that use of Zuckers equation for growth as presented i n 1942 does not r e s u l t i n one growth constant, but that the data as plotted gave four cycles or phases of growth f o r each r a t , and each phase of growth had a constant whose : numerical value was less than the one preceeding. These findings tend to substantiate the equation for growth as presented by Brody and also provide further proof of his hypothesis that - 106 -animal growth i s progressively modified from time of conception, tending to be c y c l i c or phasic i n nature. 2. The Relationship of Metabolic Rate to Growth Rate: Dunlop (1935) presents a comprehensive explanation f o r v a r i a t i o n i n gains i n animal n u t r i t i o n studies. He demon-strated that a f a s t growing animal did not have a lower basal metabolism than a slow growing animal at equal body weight i n the growing period, but that the basal metabolic rate was higher f o r the r a p i d l y gaining animal. D i g e s t i b i l i t y t r i a l s conducted by Dunlop demonstrated that the percentage of food digested from the same ra t i o n by the two experimental animals was nearly equal and could not account f o r v a r i a t i o n In l i v e weight gains. The most s i g n i f i c a n t explanation f o r differences In live-weight gain was based on the actual energy stored as body gain. Dunlop pointed out that retention of 1 gram of f a t gave the body 9 Calories while the retention of 1 gram of protein with i t s associated water represents the storage of 1 C a l o r i e . Measure-ments f o r back f a t thickness on fast-and slow-growing pigs from h i s basal metabolism studies showed that during the growth phase the rapid-gaining animals had 2.9 cm. of back f a t while the slow-gaining animals had 3.1 cm. This, stated Dunlop, explained the higher basal metabolism per unit weight of the rapid growing animal due to a greater active protoplasmic mass, to which basal metabolism i s relate d . During the fattening period, 104 to 178 pounds, l i v e weight increase only d i f f e r e d by two pounds between the fast-and slow-growing l i n e s and basal metabolism measurements were nearly i d e n t i c a l , thus f a t and protein must have been l a i d down at nearly the same rate i n the two animals. When Dunlop - 10? -corrected the f i n a l weights for differences i n c a l o r i c content by back f a t measurements, i t was shown that the gains could be calculated on an equal energy basis and f i n a l corrected weights consequently varied only to a s l i g h t degree f o r i n d i v i d u a l s on one treatment. Equalization of food intakes for animals on experiment i n Dunlop*s t r i a l s allowed for large variations i n true weight gains. Ritzman et a l . (1941), studying basal metabolic rates i n Chester White swine, further substantiated the work of e a r l i e r investigators by showing that the female has a basal metabolic rate 20 per cent lower than the male, and that castration of the male lowered the basal metabolic rate to that of the female during the stage of sex r e s t . 3. Endocrine Secretions and t h e i r Effect on Growth Rates; Some physiologists have t r i e d to explain differences i n growth rates i n swine from measurements of the amount of growth hormone secreted by the anterior p i t u i t a r y . E l i j a h et a l . (1942), worked on the thyrotropic content of the anterior p i t u i -tary of three strains of Poland Chinas swine. These animals had been selected for slow and fast rates of growth. The potency of thyrotropic secretions was determined by chick assay. E l i j a h et a l . (1942) showed that r a p i d l y gaining pigs had anterior lobes containing 27 per cent more chick units of thyrotropic hormone per gram of fresh anterior p i t u i t a r y t i s s u e . Thus a high c o r r e l a t i o n existed between rapid growth and high thyro-tropic hormone concentration i n the anterior p i t u i t a r y gland. Total thyrotropic concentration of the anterior p i t u i t a r y gland was found to decrease as the pigs reached mature body weights. - 108 -Cole ( 1 9 3 8 ) i n a discussion on endocrine control of growth has stated that although post-natal growth Is arrested promptly when growth hormone i s withdrawn as i n the hypophy-sectomized animal, there are s t i l l other agents c o n t r o l l i n g growth inasmuch as the result s obtained from chronic adminis-t r a t i o n of growth hormone are d i s t i n c t l y l i m i t e d . Evidence has been presented that c e l l s have varying inherent capacities for growth, independent of e x t r a c e l l u l a r influences such as growth hormones. Baird et a l . ( 1 9 5 2 ) have studied endocrine causes of genetically d i f f e r e n t growth rates i n Hampshire swine. They selected f o r rapid and slow growth rate f o r nine generations and developed two genetically d i f f e r e n t s t r a i n s . The two strai n s d i f f e r e d widely i n t h e i r a b i l i t y to gain and i n t h e i r economy of feed u t i l i z a t i o n f o r growth. The anterior p i t u i t a r i e s were obtained from pigs from these strains at equal age for weight and concentration of growth hormone was determined using immature hypophysectomized female r a t s . I t was found that at a l l ages the anterior p i t u i t a r i e s of the rapidly growing s t r a i n contained s i g n i f i c a n t l y more growth hormone on an equal weight basis, also the sex of the hog did not influence the growth hormone potency of the p i t u i t a r i e s . These results are i n close agreement with those of E l i j a h et a l . (194-2). The result s of both workers would indicate that more rapid gains i n swine at a l l ages are due primarily to the secretion of larger amounts of growth hormone, hence an increase i n basal metabolic rate for faster growing swine as evidenced by the work of Ritzman, Dunlop and others. _ 109 -4. Sex Differences and Growth Rates; Growth rate studies by Comstock et a l . (1944) on Poland China and Minnesota No. l ' s have shown that sex differences i n rate of growth from weaning to 200 pounds were .039 pounds per day i n the Poland China's and .089 pounds per day i n the Minne-sota No. l ' s for barrows over g i l t s . The sex difference i n growth rate were found to increase with age i n both groups. The shorter time to puberty from b i r t h In the Minnesota No. 1 i s believed to explain the higher sex difference i n growth rate between the two breeds. Age at puberty has been studied by Robertson et a l . (195D i n Poland China and Chester White g i l t s and found to average 201 days. Estimates f o r age at puberty i n the Yorkshire are e a r l i e r than those reported by Robertson. 5. The Normal Growth Pattern of the Hog; The c l a s s i c a l study of growth i n the meat animal was conducted by McMeekan (1941) who analysed carcasses of groups of hogs at d i f f e r e n t body weights from b i r t h to 200 pounds to determine the e f f e c t of varying l e v e l s of n u t r i t i o n on r e l a t i v e growth of body organs and systems. The study has substantiated the claim of a d i f f e r e n t i a l rate of growth of body organs (Hammond 1928), the more es s e n t i a l organs, heart, lungs, brain and bone grow most ra p i d l y i n e a r l y development, but they also have the top p r i o r i t y for nutrients at any time during l i f e when the supply i s l i m i t e d . The key to his entire growth study was that the best development and balance i n conformation and compo-s i t i o n was obtained when experimental animals grew at a rapid and uninterrupted rate from b i r t h to slaughter. - 110 -(3) Carcass Composition Differences i n carcass composition have been used to explain differences i n rates of gain f o r animals on an equal c a l o r i c intake at the same body weight (Dunlop 1935)• 1. Carcass Composition i n Relation to Body Gain: Several investigators have commented upon various r a t i o s and values f o r c e r t a i n constituents i n animal bodies. Armsby and Moulton (1925) and Johnson et a l . (1936) have adduced evidence f o r the comparative constancy of the r a t i o of water to protein i n animal bodies a f t e r chemical maturity has been reached. V a r i a b i l i t y of f a t content has led a number of i n v e s t i -gators to express the composition of bodies on a f a t free basis. Murray (1922) stated that the f a t free matter i s of p r a c t i c a l l y constant composition. Moulton (1923)» by ca l c u l a t i n g values f o r the composition of bodies to the f a t free basis, was able to define regular and consistent changes with age. At a mature weight, a l l groups were s i m i l a r . M i t c h e l l and Carman (1926) have shown by computing the gains of i n d i v i d u a l rats that equal gains made at the same rate by l i t t e r mates on the same diet may d i f f e r widely i n composition. Moulton, Towbridge and Haigh (1922) maintained steers at three planes of n u t r i t i o n by feeding d i f f e r e n t amounts of the same r a t i o n . It was found that the best nourished and most ra p i d l y gaining group added the greatest portion of f a t at a l l ages and the slowest growing animals contained and deposited the least f a t . These re s u l t s are i n accord with those of Pickens - I l l -(194-0) who conducted similar t r i a l s with r a t s , and also i n accord with some of the results obtained by McMeekan (1941) i n a study of the Large White p i g . The re s u l t s of Pickens (1940) and others can be r e a d i l y explained since i n the absence of s u f f i c i e n t energy the animals would merely maintain body weight or gain very s l i g h t l y i f protein was not l i m i t i n g since i t i s the excess energy above the requirement f o r maintenance that i s used f o r fattening purposes. This concept has been well substantiated by the very early work of Mendel and Judson (1915) who demon-strated that older mice when r e s t r i c t e d i n c a l o r i c intake con-tained the same proportion of f a t as younger normal mice of the same weight. Pomeroy (1941) studying the e f f e c t of a submaintenance d i e t on the composition of the pig found that the early maturing organs, brain, eyes, etc., continued to grow. The tissues of the carcass were affected i n reverse order to t h e i r development, i . e . f a t most, muscle le s s and bone l e a s t . Bone continued to grow i n the e a r l i e r stages of submaintenance. Within the f a t depots of the pig the l a t e r developing kidney f a t was reduced f i r s t , then the subcutaneous f a t and l a s t l y the early-developing i n t e r -muscular caul and mesenteric f a t when the di e t was at a sub-maintenance l e v e l . In the case where animals are fed ad li b i t u m , each i n d i v i d u a l i s allowed to express his own genetic growth po t e n t i a l and his a b i l i t y to fatten may also be measured. M i t c h e l l and Hamilton (1929) and Crampton (1940) have fed hogs a uniform d i e t ad libitu m . Individual variations i n rate of gain were not p a r a l l e l e d by consistent differences i n body composition. - 112 -Haecker (1922), who analysed the bodies of steers over a wide range of weights distinguished between two periods of development, the growing stage, when protein exceeded f a t i n rate of deposition, and the fattening stage when the reverse held. This has been well demonstrated i n the work of McMeekan (194-1) with the pigs. Donald (1940), i n a study of growth rate and carcass q u a l i t y i n bacon hogs, has pointed out that growth rate a f f e c t s carcass quality, but the extent of i t s e f f e c t s varied with the part of the carcass, with the time at which the growth rate was measured, and with the genetic c o n s t i t u t i o n of the pigs. Moulton and co-workers (1922) observed a thinning during early growth followed by a tendency to deposit f a t a f t e r the period of most rapid gain i n weight. They found that n i t r o -gen storage followed that of water and was inversely proportional to f a t deposition. Early rapid gains were found to contain larger proportions of protein and smaller proportions of f a t than l a t e r slower gains. Slow gains i n slow groups were found to be preponderantly protein i n nature. This has been demon-strated i n the rat by Pickens et a l . (1940) and by many other i n v e s t i g a t o r s . Another factor of importance r e l a t i v e to carcass composition i s that of age. Reed et a l . (1930) have stated that f a t t y acid deposition Is more cl o s e l y correlated with body weight than with age. In t h e i r experiments older stunted animals made larger gains i n the f a t sense than did younger normal animals at the same body weight. This phenomenon has also been demonstrated by McMeekan (194-1) i n the p i g . Pickens et a l . (1940) and other workers have shown that dietary f a t promotes f a t - U S -deposition i n rats to a greater extent than does carbohydrate. The experiment of Pickens et a l . (1940) has also demonstrated that those animals that achieved the most rapid early growth, i n which water and protein were added i n high proportions, accumu-lated at maturity disproportionate quantities of f a t i n the gains. In contrast, the stunted rats of the experiment, given an oppor-tunity f o r growth only at a mature age, made gains r i c h e r i n protein and water than those made at the same age by the heavier animals. Hamilton (1939) has observed i n controlled feeding experiments where le v e l s of whole egg protein fed ranged from 16 per cent to 42 per cent of the d i e t , that no marked d i f f e r -ences i n composition of gains resulted. In t h i s thought Beach et a l . (1943), have analysed voluntary muscle tissue from a large number of animals of d i f f e r e n t species. The r e s u l t s indicate that the same or c l o s e l y similar amino acid composition of muscle proteins i s repeated throughout the animal kingdom, thus a d e f i n i t e pattern exists f o r the synthesis of tissue proteins. 2. The E f f e c t of Fat Content of The Diet on Carcass Composition; E l l i s et a l . (1925) have demonstrated that when hogs are fed a r a t i o n low i n f a t , the r e s u l t i n g carcass f a t formed was hard, being high i n saturated f a t t y acids, with a decrease i n the percentage of l i n o l e i c acid with o l e i c remaining nearly constant. Recently data by Shorland et a l . (1945)» i n a study of swine carcass q u a l i t y as affected by dietary f a t t y acids, has indicated that dietary l i n o l e i c acid was assimilated to a greater extent by slow-growing than by fast-growing pigs. Dietary l a u r i c - 114 -and myristic acids, however, appeared i n greater proportions i n the f a t depots of fast-growing as compared with slow-growing pigs. They proposed that pigs which grow slowly produce a more unsaturated f a t than pigs that grow rapidly, as f a s t growing pigs use more carbohydrate f o r energy rather than l i m i t e d food o i l s . The f a s t e r the rate of f a t deposition the more saturated i s the f a t deposited. Basic differences i n unsaturation of outer and inner layers of back f a t were said to be due to d i f f e r -ences i n the r a t i o of o l e i c to s t e a r i c acid, while differences i n l i n o l e i c acid were small. Later Shorland (1950) disagreed with the general b e l i e f that dietary f a t influences depot f a t . He has suggested that animal f a t s be divided i n t o two types: 1. Heterolipoid f a t s - the f a t t y acid composition of which i s s u b s t a n t i a l l y unaffected by the nature of the dietary f a t , as i n beef and mutton tallow; and 2. Homolipoid f a t s - f a t s which r e a d i l y incorporate the f a t t y acids present i n dietary f a t . Shorland states that most animal f a t s are homolipoid, but some are intermediate such as milk f a t which, i f the concentration i n the d i e t i s large enough, w i l l a l t e r f a t t y acid content by including the dietary constituent. This section can be summed up quite well from a d i s -cussion by McMeekan (195D on growth i n the meat animal. He stated that the important thing to appreciate i n growth and development of meat animals i s that the best development and balance i n conformation and composition are obtained when these animals grow at a f a s t and uninterrupted rate from b i r t h to slaughter. Interruption i n the normal growth rate of a meat - 115 -animal w i l l produce predictable e f f e c t s on the carcass, poor muscle can be a consequence of slow growth i n early l i f e , and excessive fatness i s inevi t a b l e i f fattening i s too fa s t i n the l a t e r stages. (4) Feed U t i l i z a t i o n Since much of the material reviewed from the l i t e r a -ture, dealing with variations i n growth rate due to differences i n feed u t i l i z a t i o n , has been covered i n two preceeding sections, (Growth and Metabolism, and Carcass Composition) only a b r i e f review of some of the more pertinent data w i l l be presented. 1. Preliminary Investigations on Feed E f f i c i e n c y of Yorkshire  Hogst One of the most s i g n i f i c a n t papers relevant to the present study on rate and e f f i c i e n c y of gain i n Yorkshire swine was conducted by Crampton (1928), where growing Yorkshire pigs were fed i n d i v i d u a l l y on the same d i e t . In t h i s study wide fluctuations were made i n body gains by d i f f e r e n t pigs on approxi-mately the same food intake. For example, one pig consumed 224 pounds of feed f o r a gain of 62 pounds; while s t i l l another p a i r consumed 283 and 290 pounds of ratio n respectively f o r body gains of 52 pounds and 73 pounds respectively. These wide v a r i -ations i n feed u t i l i z a t i o n were exhibited i n a small population of ten pigs. Crampton (1939) and Ashton et a l . (1942) have published data on growth rates and feed consumption of the Canadian York-shire hog i n order that normal growth curves and feed consumption figures could be used to establish standards for the breed. - 116 -2. Methods of Expressing Feed E f f i c i e n c y ; Dunlop (1933)) conducted a study on d i f f e r e n t methods of feeding animals In n u t r i t i o n a l studies i n order that v a r i a t i o n i n growth response could be measured more accurately. He pointed out 3 methods for feeding animals i n n u t r i t i o n a l studies. 1. Group feeding. 2. Individual feeding - t h i s method was said to be lim i t e d as animals could not be compared on random feed Intakes. 3. New method - Individual feeding on a controlled Intake. This was said to give a more precise measurement of actual c a l o r i c intake i n order that animals could be compared at equal body weights. I t has been stated that method (3) allows f o r maximum expression of differences between animals In any feeding t r i a l . The method, i s o c a l o r i c intake at equal body weight, has been used i n the present thesis to demonstrate wide fluctuations i n growth rate and feed e f f i c i e n c y i n an animal population that i s f a i r l y c l osely related. Differences i n e f f i c i e n c y of food u t i l i z a t i o n have been recognized by physiologists since the early days when use was made of the b i o l o g i c a l method i n biochemical research. Thus Hopkins (1912) considered the cost of growth i n his animals i n terms of ca l o r i e s required for unit gain i n body weight i n order to explain the remarkable growth-promoting effects of small additions of milk to certain synthetic d i e t s . Macallum (1919) obtained data showing the energy cost of a gram of gain to be - 117 -greater for female than for male r a t s . Smith and Carey (1923) and Levine and Smith (1927) calculated food u t i l i z a t i o n by determining the calories required by rats to make a d e f i n i t e gain i n l i v e weight. Eward et a l . (1928) calculated the amount of food required to make 100 grams gain. This method was used i n early l i v e s t o c k feeding t r i a l s . I t had the disadvantage that i t did not account f o r a change i n maintenance cost as an animal becomes heavier. Titus et a l . (1930), i n feeding t r i a l s with growing chicks, determined the average e f f i c i e n c y of the food conversion f o r the d i f f e r e n t l o t s by calculating for two-week periods the gain i n l i v e weight per unit weight of food consumed. In a r r i v i n g at a method for determining the energy requirements of dogs, Cowgill (1923)> calculated the calories consumed per kilo-gram of body weight. M i t c h e l l and Carmen (1926) expressed: Percentage U t i l i z a t i o n of food energy = 100 x (ave. basal heat produced x days on experiment + energy of the gain) metabolizable energy 3. Inheritance as a Faetor Influencing the E f f i c i e n c y of Food  U t i l i z a t i o n ; Morris et a l . (1933) have studied inheritance as a factor influencing the e f f i c i e n c y of food u t i l i z a t i o n i n the r a t . Evidence was given to support the b e l i e f that heritable factors influence the e f f i c i e n c y of food u t i l i z a t i o n . Female rats were found to consume more dry matter per unit of gain per unit of body weight than males on i d e n t i c a l d i e t s . A chemical analysis - 118 -of the carcasses of female rats showed them to be higher i n t o t a l dry matter, ash and f a t and lower i n nitrogen and f a t free dry matter than the carcasses of the male r a t s . The experiment also demonstrated that e f f i c i e n c y of food u t i l i z a t i o n could be f a i r l y well standardized i n the inbred l i n e s a f t e r s i x generations. S i g n i f i c a n t differences i n food u t i l i z a t i o n f o r two inbred l i n e s , showed that the low e f f i c i e n c y l i n e was about 40 per cent less e f f i c i e n t than the high e f f i c i e n c y l i n e . This percentage figure i s a c t u a l l y the same as that obtained by Crampton (1928) who measured variations i n feed u t i l i z a t i o n i n Yorkshire swine. Palmer et a l . (1946) have continued the study of Morris et a l . (1933) dealing with genetic differences i n the biochemis-t r y and physiology influencing food u t i l i z a t i o n f o r growth i n r a t s . They concluded that the o v e r - a l l e f f i c i e n c y of food u t i l i -z ation i n growing rats i s controlled by inheritance f a c t o r s . Also that the e f f i c i e n c y differences of two test strains were not due to differences i n a b i l i t y to digest and metabolize test r a t i o n s . The less e f f i c i e n t s t r a i n animals consumed less dry matter and developed at a slowerrate when fed the test r a t i o n ad l i b i t u m , but when both strains were r e s t r i c t e d so that they consumed the same amount the less e f f i c i e n t s t r a i n s t i l l showed a decreased growth rate and lower feed e f f i c i e n c y . On equalized feed intake the more e f f i c i e n t s t r a i n made greater gains i n protein, ash, ether extract, dry matter, and Calories than the less e f f i c i e n t s t r a i n . When the heat increment l o s t In metabolism during growth was calculated i t was found to be higher i n the less e f f i c i e n t s t r a i n . Mature males of the low e f f i c i e n c y s t r a i n - 119 -showed a higher energy requirement for maintenance both per unit surface area and per unit body weight. They had too, a higher basal metabolism per unit body weight, a lower excretion of en-dogenous urinary nitrogen per unit surface area, and a lower body temperature than the more e f f i c i e n t s t r a i n . Castration was found to reduce the e f f i c i e n c y of food u t i l i z a t i o n i n the more e f f i c i e n t s t r a i n but did not s i g n i f i -cantly a f f e c t that of the less e f f i c i e n t s t r a i n . Castration reduced growth i n length of skeleton i n both s t r a i n s . Thus i t seems apparent that physiological differences do exist between the high-and low-efficient s t r a i n s of r a t s . These phy s i o l o g i c a l differences have been shown to explain i n part the differences between the two strains i n e f f i c i e n c y of food u t i l i z a t i o n . There i s no doubt that several of these same factor s are probably responsible for differences i n e f f i c i e n c y of feed u t i l i z a t i o n i n swine. Forbes (194-6) has shown i n a feed u t i l i z a t i o n study with rats that i f the per cent of f a t fed to rats i n an i s o -c a l o r i c diet i s increased from 2 to 30, then there re s u l t s a decrease i n energy expense of u t i l i z a t i o n of the i s o c a l o r i c diets i n order of t h e i r increasing f a t contents, due to a decrease i n heat from catabolism of carbohydrate and from synthesis of f a t . In a study of hereditary obesity i n yellow mice, Dickerson and Gower (1947) demonstrated that t h i s t r a i t was the re s u l t of a more e f f i c i e n t u t i l i z a t i o n of food. There was c e r t a i n evidence that the yellow gene i s hormone i n action and i s i n -volved i n altered carbohydrate metabolism. Hess (1948), studying inheritance of food u t i l i z a t i o n - ISO -In growing domestic fowl, stated that there was an inherent difference i n feed e f f i c i e n c y between in d i v i d u a l s that could not be explained on the basis of body weight, rate of gain or time. Baker et a l . (195D have substantiated the work of e a r l i e r investigators who conducted d i g e s t i b i l i t y t r i a l s with animals to explain differences i n feed e f f i c i e n c y and found that differences i n rates and e f f i c i e n c i e s of gain were not due to i n d i v i d u a l differences i n digestive powers of the animals tested. Mayer et a l . (1951) have t r i e d to measure the thermo-chemical e f f i c i e n c y of growth i n the Albino r a t . They have stated that a consideration of gross e f f i c i e n c y does not ade-quately represent the energetics of growth any more than the weight curve does, due to proportions of protein, f a t and water being deposited i n the gains. The thermochemical e f f i c i e n c y of growth was found to remain remarkably constant throughout the period of active growth and did not begin to decrease u n t i l the onset of puberty. In summary, variations i n feed u t i l i z a t i o n i n c l o s e l y related populations do exist and are probably controlled by inheritance f a c t o r s . The precise explanation f o r these v a r i -ations i s not yet evident. From a very detailed l i t e r a t u r e review on growth and e f f i c i e n c y of feedconversion as related to the present study of post-weaning growth and e f f i c i e n c y of feed conversion i n the Yorkshire hog, the following f a c t s are evident: (1) H e r i t a b i l i t y estimates of several economic charac-t e r i s t i c s of Swine, which include weight f o r age and feed economy, - 121 -are highly v a r i a b l e . Sampling errors probably make a large contribution to the v a r i a b i l i t y of these estimates although c e r t a i n of the v a r i a t i o n may come from a genuine difference between populations. (2) S u f f i c i e n t v a r i a b i l i t y exists between indivi d u a l s i n most swine populations to provide adequate se l e c t i o n d i f f e r -e n t i a l s . (3) Selection for rate of gain alone would seem to provide rapid improvement i n both rate and economy of gain with s l i g h t improvement i n the major carcass t r a i t s . (4) H e r i t a b i l i t y estimates f o r several economic charac-t e r i s t i c s of Canadian Yorkshire swine appear to be f a i r l y high. (5) The Instantaneous Relative Growth Rate Equation: K = In W2 - In w± t 2 - t i appears to express the growth of animals on a mathematical basis but with a chemical and physiological foundation. (6) The most s i g n i f i c a n t explanation f o r differences i n l i v e weight gain i s based on the actual energy store as body gain. The retention of 1 gram of f a t represents a storage of 9 Calories while the retention of 1 gram of protein with i t s associated water represents a storage of 1 C a l o r i e . Hence f o r any two pigs at equal body weight, the one that stores protein w i l l be putting on body gain more e f f i c i e n t l y than the one that stores f a t . Therefore, by actual measurement the f a s t e r growing pig exhibits the more rapid metabolic rate due to a greater active metabolic mass. (7) During the growth phase the impetus to store protein - 122 -Rather than f a t and hence u t i l i z e food e f f i c i e n t l y appears to be due to the secretion of large amounts of growth hormone. (8) . The growth rate of g i l t s i s slower than that of males and i s possibly accounted f o r by a 20 per cent reduction i n the basal metabolic rate of a g i l t below that of a boar before puberty. (9) A. rapid rate of growth f o r a pig from b i r t h to slaughter appears to afford maximum development and balance i n conformation and composition. (10) The f a s t e r the rate of f a t deposition the more saturated the f a t deposited. (11) Individual feeding on a controlled intake would seem to offe r a more precise measurement of actual c a l o r i c intake i n order that animals be compared at equal body weights. (12) Physiological differences exist between highl-and l o w - e f f i c i e n t s t r a i n s of animals and these ph y s i o l o g i c a l differences explain i n part the differences i n food u t i l i z a -t i o n between c l o s e l y related i n d i v i d u a l s . - 125 -3. Experimental Procedure A total of 28 pigs were placed on the Feed Efficiency-test, 6 from each of Litter Nos. 2, 3 and 4 and 10 from Litter No. 5. Litt e r No. 2: Sex Pig Number Litter No. 3 Sex Pig Number F F M M 200 201 204 205 206 207 F F M M M M 211 212 214 215 218 221 Lit t e r No. 4: Sex Pig Number Litter No. 5 : Sex Pig N F 230 F 240 F 231 F 241 F 232 F 242 M 234 F 243 M 237 H 244 M 238 M 245 M 246 M 247 M 248 M 249 The dams of the four l i t t e r s were f u l l sisters and a l l were bred to their grandsire, an inbreeding coefficient of 12^ per cent. As f a c i l i t i e s were not available when the piglets from - 124 -L i t t e r Nos. 2 , 3 and 4 were weaned at eight weeks, they had to be penned and fed i n groups. On February 7 t h , 1953 > L i t t e r Nos. 2 , 3 and 4, a f t e r an adjustment period of four days..in i n d i v i d u a l pens, were put on a feeding schedule, (Table XXVIII (h)) where a l l pigs were fed i s o c a l o r i c a l l y at equal body weight. A l l pigs were fed twice d a i l y and any feed not eaten was weighed back d a i l y . The feeding schedule f o r pigs fed i s o c a l o r i c a l l y ( L i t t e r Nos. 2 , 3 and 4) was calculated from the following data: (1) The growth curve of a pig that reached 200 pounds i n 165 days, was selected from the Arrowsmith data. The growth constants over the phases of l i n e a r i t y were calculated and from these the expected d a i l y gains were derived. (2) M i t c h e l l ' s data f or the energy content of the body weight gain of swine (Figure XII) was used to compute the net energy represented by the body weight change of the pig i n (1) above. (3) The resting energy requirements of growing swine (Figure XII) were taken from the report of Brody (1945). Using these values the net ca l o r i e s required for growth were computed as follows: e.g. The pig of (1) was taken at a body weight of 3 3 . 1 pounds. The K value or per cent growth f or t h i s pig at 33 pounds was 3.40$ per day as calculated by the method of least squares (Appendix I I I ) . Expected d a i l y gain = .034 x 3 3 . 1 = 1 .12 pounds per day. Energy content of gain at a body weight of 33 pounds (Figure - 125 -XII) = 1360 Calories per pound of body gain. Therefore the net Calories required f o r gain r I36O x 1.12 = 1523 net Calories for a gain of 1.12 pounds. The Resting Energy requirements at 33 pounds body weight (Figure XII) = 1150 Calories per day. Therefore the t o t a l net Calories required f o r growth = Resting Metabolism Calories + Calories required f o r gain. T o t a l net Calories = 1523 + 1150 - 2673 The thermal content of the rations as calculated a f t e r estimates from Morrison (195D was approximately 1 Therm per pound of r a t i o n fed. Assuming t h i s value I t was seen that a pig of body weight 33 pounds would receive: 2673 Calories 1000; Calories (1.Therm) r 2.67 pounds of feed per day. This method was used to calculate the feed require-ments of the pig used i n the example from a s t a r t i n g weight of 33 pounds, then at weekly increments u n t i l i t reached a market weight of 200 pounds. The calculated feeding schedule i s presented i n Table XXVIII (a). In order to obtain the feed requirements f o r the pigs at f i v e pound i n t e r v a l s , the calculated feed requirements were plotted on a r i t h - a r i t h paper against body weight. The actual feed given i s presented i n Table XXVIII (b). The pigs were weighed weekly and the feed intake ad-justed at that time. After a two week feeding period i t was r e a l i z e d that the feed fed was i n s u f f i c i e n t so the 18 pigs were then fed at a body weight 10 pounds greater than the actual weight. L i t t e r No. 5 was put on test March 4th, 1953» - 126 -and a f t e r a four day period of adjustment i n i n d i v i d u a l pens each pig was fed at a rate demanded by i t s own growth constant. That I s , the feed requirement was calculated i n the same manner as i l l u s t r a t e d i n the example for L i t t e r Nos. 2, 3 and 4, except that the growth constant or K value of each pig i n L i t t e r No. 5 (pig Nos. 240-249 inclusive) was determined from the weights of the previous week. By p l o t t i n g the weights at weekly i n t e r v a l s on a r i t h - l o g paper, any change i n the growth constant as indicated by a deviation from a straight l i n e could be determined and the feed requirements altered accordingly. To i l l u s t r a t e t h i s reasoning the feed requirements of Pig No. 240 as derived from her Growth Constants may be used. Example? Body weight = 46 pounds. K Value or Growth Constant = 2.58 per cent per day. Expected d a i l y gain = .0258 x 46 a 1,18 pounds. Therefore the gain i n 3.5 days s 3.5 x 1.18 • 4.13 pounds. Increase i n body weight a f t e r 3.5 days a 46 +• 4.13 • 50.13. Resting Energy Metabolism at 50 pound body weight a 1600 Calories. Energy Content Per Pound of Body Gain, at 50 pounds body weight a 1500 net Calories. The d a i l y gain at 50 pounds = .0258 x 50 = 1.29 Therefore the number of calories required d a i l y f o r a gain of 1.29 pounds at 50 pounds body weight = 1.29 x 1500 Calories -1935 net Calories. The t o t a l net Calories required for growth = Resting Energy Metabolism Calories required f or d a i l y gain. Calories - 1600 + 1935 * 3535 I f the net energy value of the r a t i o n i s 1 Therm per pound of feed then the number of pounds of feed fed each day = - 127 -3535 • 3 . 5 3 5 pounds. The amount of feed required for the week = 1000 7 x 3 . 5 3 5 = 24.7 pounds. The amount of feed a c t u a l l y consumed i n the week was r 2 5 . 2 pounds. The actual d a i l y gain for the week was = 1.42 and the body weight reached a f t e r 7 days = 5 6 pounds, an increase i n 7 days of 10 pounds or 1.42 pounds d a i l y . The weight of 5 6 pounds i s now used. At a per cent d a i l y gain of 2 . 5 8 , the expected d a i l y gain = .0258 x 5 6 a 1.44 pounds. Following the preceding method of c a l c u l a t i o n the amount of feed required f o r the week i s found to be 2 9 . 6 pounds. The amount of feed consumed i n the week was 29.5 pounds. This same method was used to calculate the feed requirements of pig Nos. 240 to 249 i n c l u s i v e . The rations used throughout the experiment had been tested previously at Arrowsmith Farms and found to produce rapid, economical gains, r e s u l t i n g i n the market hogs reaching 200 pounds i n 172 days and y i e l d i n g 60 per cent. Grade A carcasses. These rations are l i s t e d i n section B of the thesis i n Tables X a, b, c, d, e, with complete analysis presented i n Table XI a and XI b. The rations were formulated at the Animal N u t r i t i o n Laboratory, University of B r i t i s h Columbia, using as standards the Recommended Nutrient Allowances for Swine as compiled by the National Research Council. The rations were fed to d e f i n i t e weight i n t e r v a l s : U.B.C. Ration No. 2 0 - 5 2 Swine Weaner Ration - fed from weaning to a body weight of 70 pounds. - 128 -U.B.C. Ration No. 22 - 52 Swine Grower Ration - fed from 71 pounds to a body-weight of 125 pounds. U.B.C. Ration No. 24 Swine Fattener Ration - Fed from 126 pounds body-weight u n t i l the pigs reached market weight. A l l weekly weights of animals were recorded and growth constants calculated from these weights. - 129 -4. Results. Complete weekly weighings for L i t t e r Nos. 2, 3» 4 and 5 from b i r t h to market are presented i n Tables XXIX a, b, c and d. Table XXVII contains a complete l i s t of growth constants fo r each pig from b i r t h to 200 pounds. The K values or growth constants are presented as KI, K I I , K i l l , etc., that i s the sequence i n which the breaks or deviations from l i n e a r i t y occurred throughout the l i f e cycle as shown by an a r i t h - l o g plot of growth data. Table XXX presents the same constants as i n Table XXVII but over d e f i n i t e ranges i n body weight. The method used i n calculating the growth constants i s presented i n Appendix I I I . A r i t h - l o g plots of weekly weights of a l l pigs from b i r t h to market are presented i n section I I of the Appendix. Table XXXI, compares the E f f i c i e n c y of feed conversion of a l l pigs over 10 pound i n t e r v a l s at equal body weights between 60 and 190 pounds as calculated from growth constants and as calculated from actual body gains. The average d a i l y gains at equal body weights are presented i n Table XXXII. This table also shows the average d a i l y gains of L i t t e r Nos. 2, 3 and 4; L i t t e r No. 5 and L i t t e r Nos. 2, 3, 4 and 5 i n c l u s i v e . Age to 160 and 190 pounds l i v e weight, t o t a l feed consumption to 160 and 190 pounds, plus type and carcass grade data are summarized i n Table XXXIII (a). Table XXXIII (b) presents the feed consumption and feed e f f i c i e n c y of the 28 pigs on test f or the 130 pound gain - 130 -from 60 to 190 pounds, also the average daily gain, and the per cent difference in feed efficiency between the most efficient male and female to the other males and females for Litter Nos. 2, 3, 4 and Litter No. 5. The feed requirements per week of pig No. 249 are presented i n Table XXXIV as an example of a l l pigs of Litter No. 5» which had their feed requirements calculated from their individual growth constants, resting metabolism and energy content of gain data. Included i n this table i s the actual feed consumption per week. The method used for calculating inbreeding, and the pedigree of the experimental pigs are shown i n Appendix IV. - 131-TABLE XXTil: GROWTH CONSTANTS OF LITTER NOS. 2t 3. 4 AND 5 AS CALCULATED FROM THE SMOOTHED BODY WEIGHTS BY THE ,INSTANTANEOUS RELATIVE GROWTH RATE EQUATION. Pig No. , KL KL a K2 E2 a K3 K3 a K4 K4 a K| K5 a K6 200 1 2 . 5 6 5.30 2.46 3.27 1.83 .96 . 6 3 201 8.73 4.31 2.62 1 .47 .81 204 9.50 5 . 3 4 3 .9U 1 .74 1.17 .91 205 7.99 ii . 3 5 3.23 1 . 4 3 . 7 8 206 13.26 3.66 2.66 .77 1 .39 .88 207 1 0 . 1 0 . 4 . 2 3 4 . 0 7 2.74 1.22; 1.18 211 9.40 2.93 2.85 1.71 1 .20 1.10 212 11.20 6.09 2.97 1 .97 1 .36 . 9 0 214 1 2 . 0 8 3.39 2.91 1.57 . 8 2 21$ 11.20 3.78 2.55 1.39 1.26 218 14.30 7.32 3.59 2.15 1.30 . 6 8 221 1 2 . 7 2 5.66 1 . 8 5 3 . a 1.79 1 .35 . 6 0 230 8.1*1 3.50 1.66 . 9 4 231 11.15 3.99 . 9 4 3.27 2.05 1 .39 . 9 5 232 8.55 2.95 I . 8 7 1 .06 234 9.18 5 . 3 9 . 5 3 3.62 2.12 l . a .72 237 9.39 3.13 2.20 1 .40 1.10 238 7.41* 3.59 1 . 0 9 3.50 2.32 1 .55 .88 240 6.66 2.58 1.65. 1 .05 . 56 21*1 9.53 3.77 2.24 1 .43 . 73 242 6.92 4.1*9 2.48 1 .70 1.03 . 5 2 243 7.49 4 . 4 6 2.27 I . 2 7 . 5 5 244 8.1*1 3.58 ' 3 .09 2.22 1 .09 . 9 9 245 1 0 . 2 7 4 . 2 9 2.26 1.68 1 .09 246 8.97 5 . 4 4 2.61 1.97 1 .07 247 8.43 3.87 1.35 2.30 1 . 2 5 . 6 8 248 . 6.52 4.51 2.52 1 . 6 3 . 6 4 249 9.67 5 . 0 3 2.36 1.66 .82 Table XXVIII (a): FEEDING SCHEDULE FOR LITTER NOS. 2, 3 ? AND 4 AS CALCULATED FROM RESTING ENERGY METABOLISM DATA. ENERGY CONTENT OF GAIN DATA AND  FROM GROWTH CONSTANTS OF A PIG THAT WEIGHED 200 POUNDS AT 165 DAYS. Body Weight K Value or Growth Constant Expected Da i l y Gain Energy Content Per Pound of Body Gain Calories Required of Body Gain Resting Metabolism Calories Total Calories Required fo r Growth Pounds of Feed Required Per Pig Per Day Pounds Calories 22 .034 .74 1200 888 850 1738 1.74 33.1 .034 1.12 1360 1523 1150 2673 2.67 44.1 .034 1.49 1480 2205 1420 3625 3.62 55.1 .023 1.25 1550 1937 1680 3653 3.65 66 .023 1.51 1610 2431 1900 4331 4.33 88 .023 2.02 1720 3474 2280 5754 5.75 110 .0124 1.36 1800 2448 2620 5068 5.09 132 .0124 1.62 1890 3061 2880 5941 5.94 154 .0124 . 1.89 2040 3855 3060 6915 6.91 176 .0124 2.17 2230 4839 3220 8059 8.06 198 .0124 2.44 2420 5904 3380 9284 9.28 220 .0060 1.32 2600 3432 3530 6962 6.96 - 133 -Table XXVIII (b): ACTUAL FEEDING SCHEDULE FOR LITTER NOS. 2 , ^ AND 4 . ' Weight Total Feed Given Body Weight Total Feed Given 3 0 Pounds 2 . 4 125 Pounds 5 . 5 6 3 5 2 . 7 130 5 . 7 2 40 3 . 0 135 5 . 8 8 45 3 . 2 140 6 . 0 6 50 3.42 145 6 . 2 8 55 3.64 150 6 . 5 0 60 3 . 8 8 155 6 . 7 4 65 4 . 0 5 160 6 . 9 8 70 4 .,.24 165 7.20 75 4.40 170 7 . 4 5 80 4 . 5 0 175 7 . 7 0 85 4 . 6 5 180 7 . 9 0 90 4 . 8 0 185 8.04 95 4 . 8 5 190 8 . 1 5 100 4 . 9 5 195 8 . 2 5 105 5.08 200 8 . 3 2 110 5 . 1 9 2 0 5 8 . 3 8 115 5 . 3 0 210 8.42 120 5.42 - 154 -Table XXIX (a): BODY WEIGHTS OF LITTER NO. 2 FROM BIRTH TO 200 POUNDS. Age Days Birth Female 2 0 0 Pounds 1.6 Female 201 Pounds 2.1* Boar 20U Pounds 2 . 6 Boar 205 Pounds 2.6 Boar 206 Pounds 2.7 Boar 207 Pounds 2.U 3 2 . 2 3 . 0 3 . 3 3.1 3a 3.1 6 3.k U.3 U.6 U.2 U.7 U.U 9 3 . 8 5.1 U.3 U.5 5.U U.8 12 l i . 6 6.1 5.5 5.1 6.5 5.9 15 5.U 7 . 0 6.3 5.7 6.6 6.5 18 6 . 3 7.9 7 . 0 6.6 7.7 7.7 21 7.2 9 . 1 6.U 7.9 8.5 9.3 25 o.k 10 .7 6.6 9.7 8.7 11.2 29 9.U 12.2 7.5 10.8 9.8 12.5 3 3 10.U iU.o 8.9 12.8 12.3 1U.9 -37 11*2 115.5 1 1 . 0 15.3 15.2 17.8 la 12 .0 16.3 12.2 17.2 17.7 20. U 1*5 13.8 18.8 15.7 a.7 a.8 25.0 h9 16.8 21.5 19.7 26.3 26.0 29.0 53 16.5 a .5 20 .0 25.2 25.0 32.5 57 1 8 . 1 . 23.5 23.5 27.3 27.3 3U.0 61 2 2 . 0 26.7 27.5 30.0 31.5 38.5 68 27.U 3U.1 35.5 uo UO J , U7 75 36.0 U3.0 UU 50 U8 58 82 U5 50 50 57 57 67 89 5U 57 57 65 6U 76 9 6 Sk 58 6 0 68 6U 8 0 103 62 68 72 79 71 92 160 73 79 81 87 7U 100 1 1 7 8 0 86 91 95 8 0 106 12U 92 98 10U 108 90 120 1 3 L 1 0 3 1 0 6 1 1 6 1 1 7 99 130 138 112 116 127 126 109 1U0 1U5 120 127 139 138 120 150 152 130 136 150 1U6 131 165 159 137 1U3 163 156 1U2 177 1 6 6 11*7 155 176 163 152 186 17U 16U 16U 187 178 165 198 181 187 19k 201 208 169 1 7 2 178 182 195 1 6 9 182 195 200 195 182 192 203 176 187 193 205 20U - 135 -Table XXIX (b): BODY WEIGHTS OF LITTER NO. 3 FROM BIRTH TO 200 POUNDS. Age Female 211 Female 212 Boar a 4 Boar a 5 Boar a s Boar 221 Days Birth Pounds 2.5 Pounds 2.0 Pounds 2.2 Pounds 2.6 Pounds 2.8 Pounds 2.3 3 3.6 2.8 3.2 3.9 4.3 3.7 6 5.1 3.2 3.7 5.6 5.9 5.0 9 6.7 3.6 5.4 7.6 7.5 6.3 12 8.7 4.8 7.0 10.0 9.6 7.8 15 10.1 5.7 8.4 11.6 11.3 8.7 18 11.4 6.7 9.7 13.5 13.3 10.7 a 12.6 8.0 11.2 15.3 14.9 10 .9 25 13.8 9.4 12.8 17.7 17.1* 12.2 29 14.5 9.5 13.6 20.0 20.4 12.7 33 15.8 10.4 15.5 22.9 23.0 14.0 37 17.3 13.0 18.3 27.0 26.0 15.7 111 17.5 13.0 18.5 27.5 26.0 16.0 45 18.0 14.0 19.3 29.5 27.3 17.0 2i9 20.5 16.1 22 33.6 30.5 20 . 5 53 23.0 17.9 25 37.5 33.5 23.5 57 25.6 20.5 27 42.2 36.9 25.8 66 35 29.0J 38 53 1*7 36 73 42 35.0 46 63 54 44 80 50 1*3 51* 72 62 52 87 52 45 57 76 65 56 94 60 53 67 88 78 66 I d 66 61 76 98 90 74 108 75 68 88 107 100 84 115 84 81 96 119 111 96 122 96 89 107 129 123 103 129 104 98 115 11*1 136 117 136 114 109 « 128 154 146 129 143 124 118 11*2 166 158 142 150 134 128 150 183 166 153 157 142 137 163 193 173 167 165 15U 148 174 209 185 181 172 161 157 182 191 191* 178 174 165 190 196 201 185 192 199 206 187 191 203 178 184 191 200 199 204 - 1 3 6 -Table XXIX ( c ) : BODY WEIGHTS OF LITTER NO. 4 FROM BIRTH TO 200 POUNDS. Age Female 230 Female 231 Female 232 Boar 23U Boar _237 Boar 238 Days Birth Pounds 2.0 Pounds 1.3 Pounds 2.5 Pounds 2.0 Pounds 3.2 Pounds 2.7 3 2.9 1 . 8 ' '3.5 2.8 U.3 3.5 . 6 3.3 2.U U.U 5.6 U.8 9 U.3 , 3.6 5.9 U.9 7.5 5.3 12 U.9 7.3 6.0 - 9.0 6.7 15 7.3 6.1 9.2 10*8 7.9 1 8 7 . 6 7.0. 10.0 9.1 11*6 . 8 . 7 21 7.7 8.0 10.6 10.8 13.0 9.8 25 9.0 9.1 12.9 12.9 15.0 10.1 29 10.0 10.0 1U.3 15.U 16.5 10.U 33 11.0 9.6 15.5 15.6 17.5 10.5 37 13.0 10.8 17.5 I 6 . 9 19.6 l l . U ia 15.5 10.9 19.5. 16.1 22.0 12.0 1*5 19.0 1U.9 23.5 21.7 27.6 16.3 h9 - 21.6 1 6 . 6 25.7 25.8 31.U 19»0 53 25.0 19.0 29.0 29.0 35.0 22.5 57 27.5 2L.6 • 32.5 32.5 38.5 2U.6 62 33 26 37 38 U5 3 0 6 9 la 3U UU U5 '52 . 3 6 76 U3 39 U8 50 58 Ul 83 52 U7 59 6 0 69 U9 9 0 58 5U 68 70 8 0 58 97 66 . 61 76 79 87 68 10U 79 73 * 85 8 9 97 8 0 111 8U 8 3 98 I d 109 91 118 96 93 108 112 120 101 125 10U 101 118 1 a 128 11U 1 3 2 108 113 1 2 9 133 1U0 127 1 3 9 1 2 3 125 137 1U5 151 1U0 11*6 133 136 1U9 15U • 161 152 151* 1U2 1 U 6 159 165 172 16U 161 1£3 157 172 172 189 172 167 159 166 188 180 196 182 171* 175 172 1 9 9 189 209 193 181 179 1 8 7 19U 200 1 8 8 1 9 1 197 205 Table XXIX (d): BODY WEIGHTS OF LITTER NO. 5 • ' mm.. B i a m i o . _20fl_P_0HND.S_ — Age Female Female Female Female Boar Boar Boar Boar Boar Boar 240 242 243 244 245 246 247 248 249 Days Pounds Pounds Pounds Pounds Pounds Pounds Pounds Pounds Pounds PoundE Birth 2.6 3.3 3.2 3.3 3 . 4 3 . 3 3 . 3 2.5 3.0 2.1 3 3.2 4.2 3.8 3.8 4.1 4.2 3.8 2.7 3 .7 . 2 . 5 6 3.4 6.1 6.0 5.0 5 .9 6.2 5 .4 4 . 0 4 . 8 4 . 0 9 4.4 8.0 6.4 6 . 6 7.3 8.1 7 . 2 5 . 3 5 . 5 $.3 1 12 5.8 1 0 . 0 7.4 8.2 9.0 9 .9 8.8 6.7 7.0 6 . 7 15 7.4 11.8 9.1 9.6 10 .8 11.7 1 0 . 5 8.1 8.3 : 8 .4 18 9 . 0 13.5 11.0 1223 12.5 13.0 12.3 9.6 9.6 10.© a 10«0 14.5 12 .5 12.6 13.6 14 . 4 13.0 1 0 . 5 1 0 . 4 .11.® 25 12.8 17.0 1 5 . 0 15 .4 15 .8 17.5 1 5 . 3 12.5 12.8 14.0 29 lS*k 2 0 . 4 18.1 18 .5 18 20.6 17.5 14.6 15 17.7 33 17.5 22 a . 5 a . 5 a 2 5 . 0 1 9 . 5 17 18 20.5 37 18 24 22 23 22 24 22 18 18 23 ia a 26 26 26 25 27 24 19 20 25 1*5 24 29 29 29 28 30 27 20 24 30 49 26 32 32 31 32 33 30 23 26 33 53 29 31 33 33 33 32 30 25 25 33 57 32 35 36 38 37 38 35 27 28 38 65 39 43 45 43 46 45 43 34 36 4 5 72 46 5® 53 51 55 52 52 38 43 53 79 56 60 66 6% 6$l, 64 64 46 54 64 86 66 71 75 74 70 75 73 56 64 75 93 75 80 83 83 84 84 83 63 75 85 100 86 90 94 98 93 91 94 74 84 96 107 97 101 107 110 108 108 i l l 86 96 110 115 108 114 119 122 119 i a 124 96 108 122 122 116 120 129 133 128 135 135 106 120 131 128 128 133 138 147 135 145 145 113 129 135 135 136 138 149 156 148 158 1 5 5 119 138 143 l l i 2 144 148 157 168 153 170 170 128 151 1 5 5 11+9 153 156 169 176 163 184 182 142 161 161 156 159 164 178 183 172 197 195 152 173 172 163 166 173 184 I89 179 162 183 180 170 172 179 189 197 186 170 196 188 - 158 -Table XXX: GROWTH CONSTANTS OF LITTER NOS. 2,3, It AM 5 FROM BIRTH TO 200 POUNDS AS CALCULATED FROM THE SMOOTHED BODY WEIGHTS BY THE INSTANTANEOUS RELATIVE GROWTH RATE EQUATION. Pig No. Sex 0 - 1 0 1 1 - 2 0 2 0 0 F itfe 2.46 2 0 1 F 2.62-204 M - m 3.94-2 0 5 M 7.99 4.35 206 M 1 3 . 2 6 3 . 6 6 2 0 7 M 10.10 4.23-211 F 9.40 2.93 2 1 2 F 1 1 . 2 0 6.09 2.97-21k M 1 2 . 0 8 3 . 3 9 2 1 5 M 1 1 . 2 0 3 . 7 8 . a 8 M 3.59-2 a M 1.85 2 3 0 F 3 . 5 0 -231 F 3$t 2 3 2 F 8.55 2.95-234 M 5.34 2 3 7 M 9 . 3 9 3.13-2 3 8 M 3:1* 1 . 0 9 1.831— : . 9 6 — . 6 3 -1 . 4 7 - • • — . . . 8 1 -2 4 0 F 6 . 6 6 2 . 5 8 2 4 1 F 9 . 5 3 3 . 7 7 2 . 2 4 -2 4 2 F 6 . 9 2 4 . 4 9 2 . 4 8 -2 4 3 F 7 . 4 9 4 . 4 6 2 . 2 7 -2 4 4 M 8.41 3 . 5 8 3 . 0 9 2 4 5 M 1 0 . 2 7 4 . 2 9 2 . 2 6 -2 4 6 M 8 . 9 7 5 . 4 4 2 . a . 2 4 7 M 8 . 4 3 3 . 8 7 2 4 8 M 6 . 5 2 4 . 5 1 2 . 5 2 -2 4 9 M 9 . 6 7 5.03 2.36-2 . 2 2 -1 . 7 4 : : ^ 1 . 1 7 . 9 1 -3 . 2 3 — _ — 1 . 4 3 . ^ . 7 8 . . 7 7 . _ 1 . 3 9 . . , . 8 8 . 2 . 7 4 ; ^ — 1 . 2 2 - _ . — , , ; , , , , 1 . 1 8 -1.71 ^— 1.20 : ^ — 1.10-1 . 9 7 1 . 3 6 . _ ^ . 9 1 — . . — . 5 5 -1 . 5 7 — — ^ ^ ^ ^ , 8 7 ^ 2 . 5 5 — — _ 1.39— ^ . _ - 1.26. 2 . 1 5 — — ^ — — 1.30 ^ • ^ • — . 6 8 '—^ 1 . 7 9 ^—^ ^ 1 . 3 5 — ^ ^—^ — ^ ^ ^ — . 6 0 -1 . 6 6 ^ ^ . 9 4 -2 . 0 5 • — 1 . 3 9 ^  ^ ^ : . : : - . 9 5 -. — 1 . 8 7 - • : : — 1.06 — . 3 4 3.62 2 . 1 2 — ^ ^  ^ _ — i.a — . . . — . 7 2 -• 2 . 2 0 — , . 1 . 4 0 , . „ -._ ' 1 . 1 0 . 0 9 3 . 5 0 2 . 3 2 — . 1 . 5 5 _ ; . 8 8 -1 . 6 5 — 1 . 0 5 — . 5 6 -1.43- — ^ 7 3 — ^ 1 . 7 0 - _ 1 . 0 3 — - ^ • . £ 2 -1 . 2 7 ^ ' — * 5 5 -; 1 . 0 9 — ^ ^ — • 6 9 ~ 1 . 6 8 — — — ^ ^ L O ? ^ 1 . 9 7 — ^ 1 . 0 7 — ^ 1 0 1 6 - • ^ — ' 6 8 -1 . 6 3 — ^ ^ — .98-1 . 6 6 — — — .82 ^ ^ — - 139 -Table XXJI: EFFICIENCY OF FEED CONVERSION AT EQUAL  BODY WEIGHT (LITTERS NOS. 2 and 3). Pig Sex No. 61-A. -70 c. 71-A. •80 c. 51-A. -90 C. 91-100 A. "C. 101-A. -110 C. 111-A. -120 c. 121-130 A. C. 131-11*0 A. C. l i a - 1 5 0 A. C. 151-A. -160 - £• 161-170 A. C. 171-180 A. C. 181-190 A. C. 200 F 2.65 2.66 2.17 2 . 5 6 U.lto 3.00 2.62 2.67 3.05 2.51* 3.9k U.71 1*.53 l*.5o 5.71 3.79 k.3h h.33 3.99 i*.03 9.26 2.90 6.26 2*.37 7.08 5.1A 1 2 . 7 6 7.25 1 0 . 2 0 5.08 201 F 2.18 3.03 2.1*6 3.3k k.2U 3.37 2.56 3.08 1*.20 3.08 3.39 2.81* 3.37 3.11 i*.32 2.96 5.87 2.93 3.65 5 . i a 5.98 5.36 1 0 . 0 8 5.2*0 3.1*3 5.1*1* 20l* M 2.00 3.26 3.02 3.19 3.15 3.0h 2.58 3.05 2.95 2.81 3.37 2.63 3.22* 3.71* 3.85 3.71 3.5C 3.69 3.87 3.78 5.60 1*.85 205 M 2.21* 3.63 3.71 3.75 1*.06 3.73 2.60 3.56 i*.03 3.36 1*.12 3.17 3.21* 3.08 5.30 5.63 k.39 5.50 6.50 5.31* 3.66 5.1*0 1 2 . 0 5 1*.95 206 M 2.02 5 . 9 5 7.13 5 .60 i*.l6 6.28 3.73 3.01 3.81* 3.86 3.1*6 3,59 3.30 3.1*2 3.2*2* 3.22* 3.63 3.13 h.2k U.85 1*.00 i*.85 1*.58 1*.96 l * . l l * 1*.68 207 M 2.1*1*. 1*.28 3.93 5.76 1*.01 It. 07 2.53 3.92 3.79 3.70 1*.00 3.60 l*.2l* 3.51* 3.03 3.55 1*.20 3.57 5.91* 3.51* 211 F 2.52 3.98 3.21* 3.32 3.11* 3.58 3*2*2 3.1*3 2.70 3.23 2*. 23 2.95 3.55 1*.06 3.71. 3.87 3.89 3.73 5.15 3.66 h.Ok 3.88 6.71* 3.98 3.11* 3.85 l u l l * 1*.02 212 F 3.88 2 . 8 0 3.23 3.06 2.28 3.16 3.93 i*.08 3.73 3.96 3.11* 3.71 1*.03 3.50 3.79 3.37 k.kk 1*.96 2*. 27 i*.76 5.05 1*.88 1*.1*8 1*.76 3.53 i*.l*2 8.05 7.05 2ll* M 2.21* 3.57 2.83 3.1*6 2.56 3.68 1*.20 3.1*7 3.08 3.21 k.k3 3.02 2.85 2.93 2.85 2.81* 5.30 2.71 3.50 1*.98 5.23 5 . 0 7 6.58 i*.97 215 M 2.35 3.82 3.15 3.67 3.81* 3.63 2.95 3.1a 3.79 3.27 3.33 3.18 3.26 3.09 3.93 3.15 2.96 3.1*1* 218 M 1.96 2.60 2.1*7 2.53 3.36 2.1*8 3.11* 3.80 3.02 3.59 2.99 3.1*7 1*.12 3.33 3.65 3.30 6.10 3.39 6.1*5 6.55 1*.70' 6.00 221 M 2 Jilt 3.05 3.18 3.08 3.08 3.33 2 . 7 0 3.08 2*.8i* 2 . 8 2 2.53 3.61* 3.09 3.35 3.07 3.28 3.85 3.16 3.37 3.26 l u l l 3.19 A. - Efficiency Calculated from Actual Body Gains - Weekly Feed C. - Efficiency Calculated from Gr?¥th Constants - Weekly Feed Weekly Gain Growxn constant x BodyWeight - 140 -TAble tm (b)j EFFICIENCY OF FEED CONVERSIONj AT "EQUAL  BODY WEIGHT (UTTERS NOS. 4 and 5). Pig Sex 61-70 71-•80 81-90 9 1 - 1 0 0 1 0 1 - 1 1 0 1 1 1 - 1 2 0 No. A. C. A. C A. c. A. c. A. c. A. C. 230 F 3 . 4 0 4 .04 2 . 1 7 3.69 £ . 3 0 3 . 4 3 2 . 7 0 3.32 4 .23 3 . 0 4 8 . 8 7 2.93 231 F 3 . 6 4 3 . 2 9 2.26 3 . 1 0 3 . 0 8 2.94 3 . 2 5 2.72 4 .23 3 . 7 5 2 . 8 8 3 . 5 2 232 F 2 . 6 5 3.09 3.71 3 . 3 3 3 . 4 2 3.09 2 . 5 0 2 . 9 2 3 . 4 6 2 . 6 9 3 . 6 3 2 . 5 6 2 3 4 M 2.39 2 . 6 8 3.30 2 . 8 6 3.15 2 . 6 8 2.80 2 . 5 4 3 .14 4 . 0 4 237 M 2.17 2 . 6 7 2 . 4 7 2 . 5 6 4 . 5 0 2.55 3 . 2 5 3.81 2.82 3 . 5 6 3 . 3 0 3.39 238 M 2 . 7 2 2.89 2.47 2.69 2 . 8 6 2 . 4 2 3 . 3 6 3 . 4 0 2 . 6 6 3.15 2 4 0 F 2.95 2.91 3 . 8 6 2 . 9 2 3 . 7 3 4 . 7 4 3.90 4 .33 4.97 4.88 5 .38 3 . 4 5 24L F 2 . 5 0 2 . 9 2 3 . 4 0 2 . 7 4 3 . 4 3 4.28 3 . 4 7 4 . 2 4 3 . 8 6 4 . 3 4 242 F 2.12 3 . 0 0 3.57 2 . 8 1 4 .25 3.81 3.10 3 . 4 6 2 . 6 8 3 . 1 2 4 . 0 5 3 .34 243 F 2 . 5 7 3.17 2.32 3.11 4 . 1 1 3 . 1 4 2 . 7 6 3.14 4 . 1 1 3.17 244 M 2.60 3 . 0 4 5.44 3 . 1 6 2.31 2.98 3 . 2 2 2 . 2 2 2 . 7 1 2.81 4 .56 5 .33 245 M 1.80 2.62 2 . 4 3 2 . 6 4 3 . 3 5 2 . 5 4 4 .35 3.09 2.19 3 . 4 8 246 M 2 . 0 7 2.62 2 . 6 7 2 . 0 6 3.21 3.19 3.19 3.06 2.41 3 . 1 6 247 M 3.47 2.69 2 . 6 5 2 . 6 7 2 . 7 5 2 . 7 7 4.11 2.59 3.49 4.48 m 248 M 2.43 2 . 5 5 2 . 7 3 2 . 6 6 3 . 5 7 3 . 7 6 2 . 9 6 3 . 7 1 3 . 8 8 3.72 3 . 6 3 3 . 5 4 249 M 2 . 6 2 3 . 3 0 2 . 9 8 3 . 1 0 3 . 6 6 2 . 9 5 3.59 4 .00 3 . 0 4 3.82 1 2 1 - 1 3 0 1 3 1 - 1 4 0 141-150 151-160 161-170 171-180 181-190 A. C. A. C. A. C. A. C. A. C. A. C. A. G. 1 3 . 4 0 4 . 6 3 3 . 8 5 4 . 5 2 6 . 7 3 4 . 6 5 3 . 0 5 4 . 6 4 3 . 8 5 3 . 9 0 3.99 4 . 5 0 4 . 4 8 4 . 4 9 8 . 4 0 4 . 5 4 3.18 4 . 1 5 5 . 2 0 4 . 1 1 3 . 7 5 4 . 1 3 2 . 3 6 3 . 4 5 7 . 2 0 5 . 9 9 4 . 8 7 3 . 5 7 4 . 9 0 4 . 1 3 4 . 7 7 5 . 0 8 5 . 0 6 5 . 8 0 3 . 8 5 3 . 9 3 4 . 5 5 3 . 9 1 4 . 6 5 3 . 9 4 3 . 0 6 3 . 9 3 3 . 5 3 2 . 7 9 4 . 3 3 4 . 8 3 6 . 0 5 4 . 7 6 4 . 3 5 4 . 7 6 4 . 9 8 4 . 2 4 5 . 4 0 4 . 3 2 m 3 . 7 0 5 . 2 1 3 . 5 1 3 . 9 6 3 . 3 6 3 . 7 2 4 . 9 9 5 . 0 6 3 . 2 9 4 . 2 2 5 . 7 2 4 . 7 9 2 . 81 3 . 5 5 3 . 4 3 3 . 3 8 4 . 4 0 4 . 3 6 4 . 4 3 5 . 2 5 3 . 3 1 3 . 8 2 2 . 6 4 3 . 5 6 6.93 6 .9? 7 . 2 3 6 . 6 5 4 . 4 8 4 . 7 8 7 . 3 0 4 . 9 2 5 . 0 2 7 . 2 7 ^ ' O l 7 .09 5 . 9 7 5 . 7 1 6 . 9 9 5 . 6 4 5 . 7 7 5.91 4.79 3.96 4 .27 4.12 3.88 3 . 1 8 2.97 . 4 6 4 .00 3 . 4 6 4 .16 3.37 5 . 0 5 5.23 3.75 2.88 3.77 2.31 2.85 3.91 4 .32 4 .17 3 . 6 6 3 . 9 8 4 . 4 6 3 . 7 6 4.70 3.86 <b"3? 3^41 3.57 3.69 2 .95 4 .31 6 .53 4 .40 3.67 4 .37 f-31 A. - Efficiency Calculated from Actual Body Gains - Weekly Feed C. - Efficiency Calculated from Growth Constants • Weekly Feed weekly trains Growth Constant x Body Weight Table XXXII (a): DAILY GAINS AT EQUAL BODY WEIGHTS BETWEEN 61 AND 190 POUNDS FOR PIGS OF LITTER NOS. 2,3 ,2* . AND. 5. Pig No. Sex 6 1 - 7 0 71-80 81-90 91-100 1 0 1 - 1 1 0 1 1 1 - 1 2 0 1 2 1 - 1 3 0 131-12*0 i i a - 1 5 0 1 5 1 - 1 6 0 1 6 1 - 1 7 0 1 7 1 - 1 8 0 1 8 1 - 1 9 0 2 0 0 F 1 . 5 7 1.00 1 . 7 1 1 . 5 7 1.28 l.ll* 1.1*2 1.00 1.1*2 71 2.1*2 .85 . 2 * 2 . 5 7 2 0 1 F 1.2*2 1 . 5 7 1.00 1 . 7 1 1 . 1 2 * 1.2*2 1 . 5 7 1.28 1.00 1 . 7 1 itS 2 0 1 * M X#*7X 1.28 1.2*2 1.85 1 . 7 1 1 . 5 7 x 9 yx X « 5 7 1.85 1.85 1 . 5 7 2 0 5 2 0 6 M M 1.00 1 . 5 7 .2*2 .85 1 . 1 2 * 1.2*2 1 . 1 2 * 1.28 1.85 X> 0 ^-|-^— 1.28 1 . 5 7 1.28 X#$7 1 . 7 1 1 . 5 7 x#xlt 1.2*2 1.2*2 1 . 0 0 1.85 2 . 1 2 * 1 . 5 7 1X2 1 . 5 7 2 0 7 M fcft .85 2.00 X$ i j.2 X#l{-2 1.2*2 2 . 1 1 * 1 . 7 1 1.28 211 F . 8 5 1.28 1.28 1.71 1 . 1 2 * 1.2*2 1.2*2 1.2*2 1 . 1 2 * 1 . 7 1 1.00 1.85 1.85 212 F 1.85 1.11* 1.28 1 . 5 7 1.28 X o lj.2 1.28 1 . 5 7 1.28 1.28 1 . 8 5 .85 21k M 1.2*2 1.28 X a^X x «xii 1 . 5 7 1 . 1 2 * 1.85 2.00 X> ©UL^-i 1.85 1 . 5 7 l.ll* 1 . 1 2 ) . 21$ M 1 . 7 1 1.2*2 1.28 1.71 1.2*2 1.71 1.85 1 . 7 1 2.2*2 218 M 1.85 1.71 1.2*2 1 . 5 7 1.71 X • Of? 1.2*2 1.71 X»Xl| 1.00 1 . 7 1 221 . . M 1.2*2 1.12* 1.2*2 1.71 1.00 2.00 1 . 7 1 1.85 1 . 5 7 2.00 2.00 230 F 1 . 1 2 * 1.85 . 7 1 X A 7X 1.1% 2#Xlj> X » i i 2 1.28 1 . 5 7 .85 2\2% 2 3 1 F 1.2*2 1.2*2 1 . 1 2 * 1 . 7 1 1 . 7 1 1 . 5 7 1.1*2 1 . 5 7 1.28 .85 2 . 1 ) 4 2 3 2 232* F M 1.28 , 1.2*2 1 . 1 2 * 1.28 1.28 1.2*2 1 . 8 5 1 . 7 1 1.2*2 1 . 5 7 1.2*2 1.28 1.57 1 . 7 1 1 . 1 2 * 1.71 1 . 7 1 1.2*2 1.28 1.85 1 . 5 7 l.ll* 1.00 2.28 1.28 2 3 7 M 1 . 5 7 1 . 5 7 1.00 i.i*2 1 . 7 1 1 . 5 7 1.1k 1 . 7 1 1 . 5 7 1.2*2 1.71 2.2*2 238 M 1.2*2 1 . 7 1 1 . 5 7 1.1*2 1.85 1.85 1.85 1 . 7 1 1 * 7 1 1 . 1 2 * 1.2*2 1 . 5 7 22*0 F 1.2*2 1.28 1 . 5 7 1 . 5 7 1 . 5 7 l.li* 1.71 1 . 1 2 * l.ll* 1:2% 1.00 .85 2 2 a F 1 . 5 7 1.28 1.2*2 1 . 5 7 1.85 1.85 . 7 1 1.1*2 X «Xl|- 1 . 1 2 * I'M 22*2 F 1.85 1.28 l.ll* 1 . 5 7 1.85 X 0 7X 1.2*2 1.28 1 . 5 7 X«Xif- x • yx 1.28 :& 22*3 • F 1.85 1 . 2 8 2 . 1 2 * 1.71 1.71 1 . 5 7 1.85 1.28 1 . 7 1 1 . 1 2 * i:85 22* 2 * M i:S 2.00 1.28 2 . 1 2 * 1 . 5 7 1 , 2 8 1.00 1.85 1'Jk 1.28 1.00 1 . 0 0 22*5 " M 1.71 1 . 5 7 1.28 1.00 2.2*2 1.85 2.00 1.2*2 1 . 8 5 1 . 7 1 2 . 0 0 22*6 M 1.71 1.28 1.2*2 1 . 5 7 2.2*2 1.85 1 . 5 7 1.2*2 1.2*2 2 . 1 2 * 1.71 2 2 * 7 M 1.00 1 . 5 7 1.71 1.2*2 X » 2 ^ . 2 .85 1.00 1 . 2 8 2.00 X# i ( 2 1.2*2 l.li* 21*8 M 1.2*2 1 . 5 7 1.28 1 . 7 1 1.71 1.71 1.28 1.28 1.85 1.2*2 1.71 1.2*2 2 2 * 9 M 1 . 5 7 1 . 5 7 1.2*2 1 . 5 7 2.00 1.28 .85 .85 1 . 7 1 .85 1 . 5 7 l.ii* Ave. of L i t t e r No. 2,3,and 1* 1 . J 5 l.2a 1.38 1.2*7 1 . 2 a 1 . 5 6 1.52* 1 . 5 2 1.2*6 1 . 5 2 1.55 1.60 1 . 5 9 Ave. of L i t t e r No, 5 1 . 5 5 1.2*6 1.39 1 . 5 6 1.91 X e^X 1.2*2 X # 3X 1.2*8 1 . 3 9 1.2*2* 1.38 X # 2 L Ave. of L i t t e r No. 2,3,2*, and 5 1.2*3 1.2*3 1.38 l . 5 o 1 . 5 9 1.52* 1 . 5 0 1.2*5 1.2*7 1.2*6 1 . 5 1 1.53 1 . 5 2 - 142 -Table No. XXXIII (a)t AGE'TO 160 POUNDS, AGE TO 190 POUNDS, TOTAL FEED; CONSUMPTION TO 160 AND 190 POUNDS, TYPE AND GRADE DATA OF ALL PIGS ON THE FEED EFFICIENCY TEST. Pig Sex Age to Age to Feed Con- Feed Con- Type Carcass Ave. Daily Gain sumed to (Alive) Grade From 60 to 190 lbs. 160 lbs. 190 libs. 200 F Days 205 Days 172 Pounds 774 Pounds 582 Short&Small EL 1 . 2 2 201 F 191 I 6 9 622 473 n a 1 .35 204 M 177 157 556 417 Good A 1 .64 205 M 1 8 6 164 606 464 n Sold (A) 1.35 206 M 189 170 604 462 Ave. EL 1 .34 207 M 168 IBS" 150 161 531 61^ 393 46T Fat A 1.51 211 F 191 171 658 518 Small A L .39 212 F 199 175 680 523 n HL L.46 214 M 178 155 596 437 Ave. Sold (A) 1.34 a 5 M 156 139 492 373 Fat B3 i r 6 9 as M 171 144 570 390 Excellent Sold (A) lL55 221 M 170 177 154 535 544 590 423 Wk Ave. Sold (A) 1L62 j 230 F 187 168 648 506 Small A lL32 1 231 F 183 163 596 464 n A 1^45 232 F I 6 9 155 535 448 Good HL ii.53 234 M 175 152 580 425 n A l i 4 l 237 M 162 145 526 411 Fat HL l i 5 7 238 M 172 175" 573 .6 409 m Excellent Sold (A) i | 6 o 240 F 157 540 Short&Small EL 1*27 241 F 152 476 Good A 1 .30 242 F 170 144 620 439 Short&Small HL 1 . 3 8 243 F 164 138 639 480 Fat HL 1 .51 244 M 173 146 610 454 Good A 1 . 3 3 245 M 152 136 521 399 n A 1.71 246 M 153 138 523 380 Excellent Sold (A) 1 . 6 8 247 M 161 451 Small n (A) 1 .35 248 M 168 148 547 432 Ave. EL 1.53 249 M I 6 9 16TT 148 ro.8 624 5*3 ' 478 433 Poor HL 1 . 3 9 - 143 -' Table No. XXXIII (b): FEED EFFICIENCY DATA FOR LITTER NOS. 2, 3, k AND 5 BETWEEN 60 AND 190 POUNDS. Pig Sex Ave. Daily Gain Feed Consumed For Feed Efficiency Per $ Difference in Feed No. Between 60&190 The Gain of 130 lb. of Body Gain for Efficiency Over Wt. Pounds lbs. Between Body Body Gain of 130 lbs. Range 60-190 lbs. Wt. of 60&190 lbs. Males Compared to M's Females Compared to F's Calculated Actual Calculated Actual Females kales Litter 2, 3, and k 200 F 1.22 • 51*8 l*.2i* i * . a 20.2$ 201 F 1.35 511* 3.79 3.89 11.2$ 20l* M 1.61* 1*1*1* 3.1*3 3.& 3.0$ 205 M 1.35 533. li.25 1*.02 21.ii* 206 M 1.31* 503 l*.l*8 3.87 16.9$ 207 M 1.5L 1*98 3.77 3.83 15.7$ 211 F 1 .39 530 3.62 1*.07 16.3$ 212 F 1.1*6 51a 1*.20 1*.16 18.8$ 211* M 1.31* 1*89 3.65 3.76 13.5$ 215 M 1.69 1*31 3.1*0 3.31 0$ 218 If 1.55 1*82 3.73 3.71 12.1$ 221 M 1.62 1*31* 3.20 3.33 6$ 230 F 1.32 532 3.91* 1*.09 16.8$ 231 F 1.1*5 502 3*62 3.86 10.3$ 232 F 1.53 • 1*56 - 3.1*9 3.50 0$ 231* M l . i a 506 3.88 3.89 17.5$ 237 M 1.57 1*61 3.38 3.55 7.2$ 238 M 1.60 1*51 3.1a 3.1*7 1*.8$ 2lj0 F 1.27 550 606 i*.23 U.66 Females Males Litter No. 5 11.2$ 21a F 1.30 527 51*5 l*.05 1*.19 0$ 242 F 1.38 527 51*6 1*.05 1*.20 ,2$ 243 F 1.51 520 555 1*.00 1*.26 1.6$ 21*1* M 1.33 51*1 527 1*J.5 1*.05 • 18.1*$ 21*5 M 1.71 1*61 1*51 3.51* 3.1*6 3.3$ 21*6 M 1.68 1*55 1*1*5 3.50 3.1*2 0$ 21*7 M 1.35 532 1*91* U.09 3.79 10.8$ 21*8 M 1.53 1*85 1*59 3.73 3.53 3.2$ 21*9 M 1.39 51*3 51*.2 1*.17 1*.16 a.6$ - 144 -5. Discussion of Results. At the outset i t must be stated that the dams of the four l i t t e r s were f u l l s i s t e r s and were a l l bred to t h e i r own graridsire, thus a l l pigs i n the experiment were 12.5 per cent inbred. Aft e r averaging the d a i l y gains for L i t t e r Nos. 2, 3 and 4 (Table XXXII) at equal body weights, one finds that they are near a maximum of 1.56 pounds per day at 111 to 1 3 0 pounds. The average d a i l y gain deviates very l i t t l e from 1 . 5 6 pounds per day even at 180 pounds. This was probably the pigs maximum genetic potential for growth and not due to a lim i t e d feed intake as most individuals of L i t t e r Nos. 2, 3 and 4 had a feed weigh-back every day when they reached 170 pounds. Table XXXII also shows that L i t t e r No. 5 reached the same maximum growth rate of 1 . 5 6 pounds per day or s l i g h t l y greater, but t h i s maximum occurred at 90 to 100 pounds or nearly two weeks e a r l i e r f o r pigs of L i t t e r No. 5 than f o r pigs of L i t t e r Nos. 2, 3 and 4. The increased growth Is probably due to the greater feed intake of L i t t e r No. 5 at that time. But i f the average d a i l y gain of L i t t e r Nos. 2, 3 and 4 i s compared with L i t t e r No. 5» the two values are nearly i d e n t i c a l at 1.48 and 1.46 pounds respectively. Although the average gains of the l i t t e r s are very s i m i l a r , the gains of i n d i v i d u a l pigs of each l i t t e r are very d i s s i m i l a r . For example g i l t No. 200 i n L i t t e r No. 2 shows a low average d a i l y gain of 1.22 pounds between 60 and 190 pounds compared with the boar No. 204 who had a gain bf 1.64 pounds per day. This represents an increase of .42 pounds per day or - 145 -25.5 per cent. Another example of wide differences i n i n d i v i d u a l gains i s between boar No. 245 and boar No. 247 of L i t t e r No. 5 who were fed according to t h e i r own growth rate. The former gained at an average rate of 1.71 pounds per day between 60 and 190 pounds while the l a t t e r gained at 1.35 pounds, an increase of .36 pounds or 21 per cent more growth per day for boar No. 245 over boar No. 247. These same variations also e x i s t i n d a i l y gain between males i n L i t t e r Nos. 2, 3 or 4 who were fed i s o -c a l o r i c a l l y at equal body weight. For example boar No. 215, of L i t t e r No. 2, had an average d a i l y gain of 1.69 pounds compared to h i s brother, boar No. 214, who had an average d a i l y gain of 1.34 pounds. This i s a difference of .35 pounds per day or 20.7 per cent more growth per day for the f a s t e r gaining male. In spite of fluctuations i n weekly gains of i n d i v i d u a l s , a d e f i n i t e growth pattern i s exhibited when weekly weights are plotted on an a r i t h - l o g g r i d . The i n d i v i d u a l growth curves of a l l pigs i n the experiment are found i n Appendix I I . These figures demonstrate the decided l i n e a r i t y of growth when body weight i s regressed against time. Thus the data would sub-stantiate Brody^ (1945) hypothesis that growth i s phasic, tending to occur at decreasing increments from the moment of conception. I t can be seen from the graphs (Appendix II) that each time the slope of the growth curve changes or every time there i s a "break" i n the curve, the K value or percentage growth decreases by nearly one-half; pig No. 249H provides an excellent example. As i n the pre-weaning stage of growth, any - 146 -abnormal condition In the post-weaning environment of the pig tends to alter the growth rate, resulting i n a corresponding decrease i n the percentage growth or K value. When the i n -hibiting factor i s removed there i s an increased rate of growth tending to restore the pig to i t s original growth rate. This phenomenon was exhibited by pigs No. 206 and No. 247. The cause of the decreased, then increased growth rate was lack of sufficient feed or energy Intake. It i s not known why these animals restricted their feed intake. From birth to 200 pounds each pig has five or six phases of linearity in his growth curve (Table XXVII). Corre-sponding to every phase of linearity is a growth constant or K value, that l i e s in an approximate weight range for a l l pigs. Table XXX presents the growth constants of a l l pigs i n their respective body weight ranges from birth to 200 pounds. The i n i t i a l phase of linearity in the growth curve occurs from 0 to 10 pounds, the second phase from 10 to 20 pounds, the third phase from 20 to 80 pounds, the fourth phase from 80 to 120 pounds, the f i f t h phase from 120 to 160 pounds and the sixth phase from 160-200 pounds. The "breaks" i n the growth curve or the changes In slope occur at near definite body weights up to 80 pounds for a l l pigs i n the experiment, but after that there i s no definite weight at which the breaks occur. Certain explanations have been offered for the various changes in the relative growth rates or percentage growth rates. The f i r s t change i n relative growth following birth has been attributed to a lack of energy for the suckling piglet due to insufficient milk production of the sow. This has been demon-- 147 -strated by a simple c a l c u l a t i o n i n the preceding section "Energy Limitations". The milk shortage at t h i s stage of growth i s common to multiparous species. The second a l t e r a t i o n i n percentage growth rate occurs at about 20 pounds or approximately 30 days post-farrowing and i s probably due to a physiological adjustment i n the organ structures of the suckling pig to allow for the handling of a dry ra t i o n or some supplemental feed. An a r i t h -log regression of body organ weights of hogs against time, from the data of McMeekan (1941) on Carcass composition studies, shows that at approximately 30 days post-farrowing there i s a sharp decline i n percentage rate of f a t deposition and muscle development. Also, the r e l a t i v e growth rate of the small i n -testine decreases markedly at t h i s age. Viewing these changes, one would think that they were due to a change In the neuro-endocrine system resul t i n g i n a homeothermic adjustment by the pig i n order to cope with environmental conditions. The t h i r d a l t e r a t i o n i n r e l a t i v e growth occurs between 60 and 80 pounds, at about 80 to 90 days post-farrowing. About t h i s time there i s a decrease i n r e l a t i v e growth rate of the large i n t e s t i n e , stomach and skeleton, but f a t and protein deposition continues at the same pace. The fourth "break" In the growth curve varies to some extent as to a d e f i n i t e body weight or age but In some cases occurs at about 120 pounds, at 110 to 130 days. At t h i s point there i s a further decrease i n the r e l a t i v e growth rate of the large and small i n t e s t i n e , stomach and the skeleton. Coupled with t h i s , the rate of fat deposition f a r exceeds that of protein -148 -deposition, hence a poor e f f i c i e n c y i n feed conversion to body gain and thus a reduction i n body gain i n the absolute sense, even though" the gain i n t o t a l energy i s f a r higher at t h i s weight than any previous weight. occurs between 140 and 170 pounds, and i s believed to be due to the onset of sexual maturity. In f a c t , male pig Nos. 218, 244 and g i l t s (females) Nos. 200 and 201 exhibited d e f i n i t e signs of sexual maturity at t h i s time. McMeekan's (1941) data on carcass studies i n swine showed that the stomach and small i n t e s t i n e reach the greatest percentage of t h e i r weight at b i r t h at 160 days of age which i s approximately puberty f o r the pig. d e f i n i t e factors c o n t r o l l i n g or retarding growth of the pig at c e r t a i n stages i n the normal growth pattern. These factors a l t e r the rate of development of organs and systems of each animal, and hence control the o v e r a l l speed of maturity or development. Nos. 2, 3, 4 and 5 at weaning provides only a barely s i g n i f i c a n t d i f f erence, indicating that there i s a minor degree of uni-formity i n the l i t t e r s f o r body weight at that age. The standard deviation of the l i t t e r s f o r body weight at weaning was: The f i f t h "break" or decrease i n r e l a t i v e growth From what has been said before there seem to be An analysis of variance for body weight of L i t t e r L i t t e r No. 2 5.4 pounds 4 3 8.3 pounds 6.2 pounds 5 4.1 pounds - 149 -A si m i l a r analysis f o r body weight at 115 days pro-vides no s i g n i f i c a n t difference between the l i t t e r averages. But the body weights at 115 days show a marked degree of v a r i a b i l i t y between pigs of the same l i t t e r . The standard deviation of the four l i t t e r s f o r body weight at 115 days was: L i t t e r No. 2 10.2 pounds 3 10.8 pounds 4 14.8 pounds 5 8.8 pounds An analysis of variance f o r body weight at 150 days provided no s i g n i f i c a n t difference between l i t t e r averages for weight at t h i s age. The standard deviation of each l i t t e r f o r body weight at 150 days was: L i t t e r No. 2 13.2 pounds 3 20.3 pounds 4 11.5 pounds 5 13.2 pounds An analysis of variance for age at 160 pounds body weight yielded no s i g n i f i c a n t difference between the four l i t t e r s . The standard deviation f o r age to 160 pounds was: L i t t e r No. 2 8.6 days 3 14.3 days 4 8.4 days 5 8.3 days The same s i t u a t i o n existed f or age to 190 pounds. The standard deviation of L i t t e r Nos. 2,3, and 4 f o r age to 190 pounds was: L i t t e r No. 2 11 days 3 15.5 days 4 9.2 days - 150 -There was no s i g n i f i c a n t difference between l i t t e r s f o r t o t a l feed consumption to 160 pounds and 190 pounds body weight. The important factor i s the standard deviation of the l i t t e r s for feed consumption at the two weights. L i t t e r No. S.D. of Feed Consumed S.D. of Feed Consumed to 160 Pounds to 190 Pounds. 2 65.2 pounds 84.9 pounds 3 63.5 70.5 4 11.8 44.9 5 45.1 As might be predicted there should be no s i g n i f i c a n t difference between the l i t t e r averages of L i t t e r Nos. 2, 3 and 4 f o r the c h a r a c t e r i s t i c s measured because of the standard-i z a t i o n of feed intake at equal body weights. A high degree of v a r i a b i l i t y between pigs of the same l i t t e r as shown by the standard deviations of each l i t t e r f o r the items measured, contributes to the lack of significance between l i t t e r averages, Table XXXIII (a) points out the wide v a r i a b i l i t y between ind i v i d u a l s of the same l i t t e r f o r age to 190 pounds, age to 160 pounds, feed consumed to 190 pounds and feed con-sumed to 160 pounds. In t h i s same table, as one might expect, a marked relationship exists between feed consumption and age to 190 pounds. In L i t t e r Nos. 2, 3 and 4 where a l l in d i v i d u a l s were fed i s o c a l o r i c a l l y , the relationship between an early age to 190 pounds and t o t a l feed consumed i s more pronounced than i n L i t t e r No. 5 where each pig was fed to his growth constant. For example boar No. 237 i n L i t t e r No. 4, required 162 days to reach 190 pounds with a t o t a l feed consumption of 526 pounds - 151-as compared with hoar No. 245 of L i t t e r No. 5 who reached 190 pounds i n 153 days hut required 523 pounds of feed. Thus boar No. 246 reached 190 pounds 9 days e a r l i e r than boar No. 237 but the t o t a l feed consumption of each animal was approximately equal. This points out the fact that unless i n d i v i d u a l feed consumption i s recorded f or each p i g , an early age-to--market or a rapi d l y growing pig w i l l not necessarily indicate an e f f i c i e n t p i g , especially i f animals are s e l f fed i n groups,at maximum intake. A comparison of t o t a l feed consumption (Table XXXIII (a) ).demonstrates further the v a r i a b i l i t y between pigs of the same l i t t e r . For example g i l t No. 232 reached 190 pounds In 169 days requiring 535 pounds of feed while her s i s t e r , g i l t No. 230, reached 190 pounds i n 187 days using 648 pounds of feed. This represents an increase of 113 pounds of feed or 21 percent more feed f o r the less e f f i c i e n t p i g . An examination of E f f i c i e n c y of Feed Conversion . between 60 and 190 pounds (Table XXXIII (b)) reveals c e r t a i n important f a c t s . A rapid rate of gain i s usually closely correlated with increased feed e f f i c i e n c y , but i s not always correct. For example boar No. 207 required 498 pounds of feed fo r the 130 pound gainbetween 60 and 190 pounds with an average e f f i c i e n c y of 3.83 pounds of feed per pound of body gain, whereas boar No. 204 required 444 pounds of feed to go from 60 to 190 pounds body weight but with an average e f f i c i e n c y of 3.4-1 pounds of feed per pound of body gain. The former pig required 168 days to reach 190 pounds while the l a t t e r pig required 177 days. This demonstrates that at the heavier - 152 -weights pig No. 204 was more e f f i c i e n t than pig No. 207 even though the former pig required 9 days longer to reach 190 pounds. Boar No. 207 was probably storing more f a t than boar No. 204 at the heavier body weights: On the other hand boar No. 246 of L i t t e r No. 5 required 153 days to reach 190 pounds body weight using 445 pounds of feed f o r the 130 pound gain between 60 and 190 pounds body weight, with an average e f f i c i e n c y of 3.42, an e f f i c i e n t rate of gain coupled with an early age-to-market. Boar No. 246 i s i n marked contrast with his brother boar No. 247; the l a t t e r had an average feed e f f i c i e n c y of 3.79 pounds of feed per pound of body gain, but had not reached 190 pounds by 186 days. The improved feed e f f i c i e n c y i n t h i s case i s p a rtly due to measurements at l i g h t e r body weights, but also due to the r e s t r i c t e d feed intake and the slower growth rate of pig No. 247. A comparison of the e f f i c i e n c y of feed conversion between 60 and 190 pounds of the two extreme boars i n L i t t e r No. 5 reveals an average difference of .74 pounds of feed per pound of gain or 21.6 per cent more feed required by the l e s s e f f i c i e n t animal f o r every pound of gain. The amount of feed consumed by the g i l t s of L i t t e r Nos. 2, 3 and 4 between 60 and 190 pounds l i v e weight (Table XXXIII (b)7 ranges from 456 to 54-8, a difference of 92 pounds of feed or a difference of 20.2 per cent i n feed e f f i c i e n c y between the least e f f i c i e n t g i l t and most e f f i c i e n t g i l t f o r the 130 pound gain. The percentage difference i n feed e f f i c i e n c y for the boars of L i t t e r Nos. 2, 3 and 4 was nearly i d e n t i c a l to the g i l t s at 21.4 per cent. It must be remembered that a l l pigs of L i t t e r Nos. 2, 3 and 4 were fed equal quantities of feed at - 153 -equal body weights. A l l pigs of L i t t e r No. 5 were fed at a rate demanded by t h e i r growth constants. The amount of feed consumed by the 6 boars of L i t t e r No. 5 between 60 and 190 pounds ranged from 445 to 54-2 pounds a difference of 97 pound of feed or a difference In feed e f f i c i e n c y of 21.6 per cent between the le a s t e f f i c i e n t and most e f f i c i e n t male. A se l e c t i o n programme based on differences i n feed e f f i c i e n c y between c l o s e l y related i n d i v i d u a l s fed i s o c a l o r i c a l l y at equal^body weight should have considerable merit, i f i n d i v i d u a l feed e f f i c i e n c y and rate of gain are considered. The o v e r a l l r e s u l t s of feed e f f i c i e n c y indicate a sup e r i o r i t y of males over females. The same advantage exists f o r weight at any age, average d a i l y gain and t o t a l feed con-sumption. A comparison of feeding methods points out that L i t t e r No. 5 reached 160 and 190 pounds l i v e weight 10 to 18 days e a r l i e r than L i t t e r Nos. 2, 3 and 4, but the average feed consumption of the four l i t t e r s from b i r t h to 160 and 190 pounds l i v e weight was quite equal. An analysis of the two methods of expressing feed e f f i c i e n c y ; (Table XXXIII (b)) (1) the actual feed consumed per pound of body gain, and (2) the actual feed consumed divided by the expected gain as calculated from the growth constant or r e l a t i v e growth rates, f o r L i t t e r Nos. 2, 3» 4- and 5, shows that over the weight range between 60 and 190 pounds, 20 pigs of the 28 tested or 70 per cent exhibited a feed e f f i c i e n c y as calculated by the two separate methods within .15 - 154 -pounds of feed per pound of gain. The .15 pounds of feed per pound of body gain would represent 1.5 pounds of feed (consumed i f any pig gained 10 pounds i n one week. The number of pigs having an average equal feed e f f i c i e n c y as expressed by the two methods described, i s 78 per cent of L i t t e r Nos. 2, 3 and 4. L i t t e r No. 5, fed i n d i v i d u a l l y to t h e i r own growth constant, had 6 pigs of the ten who had the actual average feed e f f i c i e n c y within .15 pounds of the expected feed e f f i c i e n c y . The lower per centage would be expected since each pig was fed according to i t s r e l a t i v e growth rate and appetite would exert some influence on the t o t a l feed consumed. Table XXXIV shows the feed requirement figures of pig No. 249 as calculated from resting energy metabolism, energy content per pound of body gain and his r e l a t i v e growth data, and compares these values to the actual feed consumed. Similar calculations were made f o r a l l pigs of L i t t e r No. 5 and are shown i n Table XXXIII (b). Nine out of the ten pigs of L i t t e r No. 5 consumed on the average within 3 pounds of the weekly feed required to supply resting energy requirements and grow.at the rate predicted from the growth curves. The tenth pig consumed within 4 pounds of the feed required. The 3 pound range i n feed consumption for the week represents a weekly v a r i a t i o n i n t o t a l gain of approximately .75 pounds. The rate of gain of i n d i v i d u a l pigs i s an important factor when studying growth rates. In L i t t e r No. 5 pig Nos. 240, 244, and 249 exhibited their maximum d a i l y gain between 90 and 120 pounds. After t h i s weight, the d a i l y gain dropped - 155 -by one-half of the previous gain; presumably these pigs commenced to fa t t e n . The early decline i n d a i l y gain of these same individuals i s revealed by the decline i n r e l a t i v e growth rate as shown i n Tables X X V I I and X X X . The faster growing and more e f f i c i e n t pigs No. 245 and 246, of L i t t e r No. 5» maintained a high r e l a t i v e growth rate to market. At an early chronological age, say 120 days, the pigs which grew ra p i d l y might be selected as early developing, fast growing, e f f i c i e n t i n d i v i d u a l s . The f a l l a c y i n t h i s type of selection i s soon realized i f these animals are allowed to reach 200 pounds body weight and growth and feed consumption data co l l e c t e d . For example boar No. 249 of L i t t e r No. 5 weaned at 3 8 pounds, one of the heaviest weaning weights of the ten p i g l e t s of that l i t t e r . This animal continued to grow rapidly and e f f i c i e n t l y to 120 pounds, then h i s growth rate decreased by nearly one-half and his feed e f f i c i e n c y increased by nearly f i f t y per cent. This boar continued to grow very slowly and I n e f f i c i e n t l y u n t i l he reached 200 pounds. Other problems are also incurred by selecting animals on growth rate alone. G i l t No. 243 maintained the fourth highest average d a i l y gain i n L i t t e r No. 5» yet her average e f f i c i e n c y of converting feed to body gain was very poor, being 4.26 as compared to boar No. 246 with the most rapid rate of gain of a l l l i t t e r s and with a feed e f f i c i e n c y of 3»42. I t has been pointed.out previously that the opposite s i t u a t i o n may hold, that i s pig No. 247 had a slow rate of growth but with,a good feed e f f i c i e n c y of 3.79. After each animal reached approximately 200 pounds - 156 -i t was taken off t e s t . Certain males were castrated then shipped to market while others were sold. Column 8 of Table XXXIII (a) shows the carcass grade obtained for those pigs sent to market, and an estimated grade (figure i n brackets) f o r those pigs sold. I t w i l l be noted that boar No. 207 from external appearance was typed as a f a t hog, yet when carcass graded, i t f i t t e d i n t o the select class or Grade A d i v i s i o n . This hog was f a i r l y e f f i c i e n t and reached 190 pounds by 168 days, the second fastest growing pig i n L i t t e r No. 2. G i l t No. 232 and boar No. 215 were both e f f i c i e n t f a s t growing in d i v i d u a l s but they were graded as B^, which indicates excess f a t i n the shoulder, l o i n , and throughout the carcass. Boar Nos. 245 and 246 i n L i t t e r No. 5 had a high average e f f i c i e n c y of feed conversion and reached 190 pounds by 153 days and both graded as A hogs. G i l t s Nos. 200 and 201 of L i t t e r No. 2 required 205 and 191 days to reach 190 pounds, they were both i n e f f i c i e n t i n th e i r conversion of feed to body gain and both graded as B i , or overfinished. The method of feeding i s o c a l o r i c a l l y at equal body weight would have certain merit i n a hog testing program where future herd s i r e s and dams were selected for rate of gain, e f f i c i e n c y of feed conversion, type and carcass characters. The method would provide an accurate measurement of feed e f f i c i e n c y i n a rapid, short term selection program and show maximum differences between ind i v i d u a l s f o r the selected characters. - 157 -6. Summary and Conclusions. The main objects of t h i s study on post-weaning growth rates and e f f i c i e n c y of feed conversion i n Yorkshire swine were: (1) To study post-weaning growth rates of Yorkshire swine under more recent n u t r i t i o n a l standards. ( 2 ) To further present day knowledge of the existence of variations i n feed e f f i c i e n c y i n a closely related swine population, where one-third of the animals were fed according to t h e i r i n d i v i d u a l growth rates and two-thirds were fed i n d i -v i d u a l l y under conditions of i s o c a l o r i c feed intake at equal body weight. A l l pigs received the same rations over the same weight range. (3) To v e r i f y as f a r as possible using metabolism and energy content of gain data for swine, Brody's (194-5) concepts of pre-pubertal growth, that Is to determine {£c^> further the v a l i d i t y of the Instantaneous Relative Growth Rate Equation . K - In W2 - In w^  over the phases of l i n e a r i t y i n the t 2 - t x growth pattern when body weight i s regressed against time on an a r i t h - l o g g r i d . Certain explanations are offered i n the l i t e r a t u r e review for differences i n growth rate and feed e f f i c i e n c y between close relatives of animal populations. The amount of growth hormone secreted appears to control the composition of the gain. The composition of the gain In turn determines the rate of gain. Both of these are controlled by the genes, which are chemical e n t i t i e s , and are the l i m i t i n g factors c o n t r o l l i n g the rate of development when a l l other nutrients required by the animal are supplied. The degree of h e r i t a b i l i t y of any - 158 -c h a r a c t e r i s t i c i s important, especially i f that c h a r a c t e r i s t i c i s of economic concern, such as rate of gain, feed required for gain and the composition of the gain made by swine. Although there was a lack of s i g n i f i c a n t difference between the four l i t t e r s for most of the ch a r a c t e r i s t i c s measured, the standard deviations f o r each l i t t e r were high. This would suggest that a Selection D i f f e r e n t i a l would be very s i g n i f i c a n t for any chosen c h a r a c t e r i s t i c and that the v a r i a b i l i t y between l i t t e r mates for any measured cha r a c t e r i s t i c : was large. A good example was the 20 to 22 per cent difference i n growth rate between males of any l i t t e r . Also, the e f f i c i e n c y at which any pig converted food to body gain varied 20 per cent or more between l i t t e r mates under both methods of feeding as used i n the experiment. The experiment shows that under present n u t r i t i o n a l standards for the hog, a market weight of 200 pounds at 5 months i s quite possible, but t h i s can only be accomplished i f n u t r i t i o n i s optimum i n both the pre-weaning and post-weaning stages of growth. The experimental result s would suggest that i f a pig grows rapidly and his d a i l y gain does not reach a maximum u n t i l he reaches 180 to 190 pounds, the composition of the gain has probably been mostly protein. This i s opposed to a pig that reaches a maximum d a i l y gain at 90 to 100 pounds, then at 110 to 130 pounds the d a i l y gain decreases; the pig has probably commenced to lay on f a t . The former pig would require 30 to 40 per cent less feed for every pound of gain than the l a t t e r P i g . - 159 -The experiment has demonstrated that f o r hogs fed under conditions of i s o c a l o r i c feed intake at equal body weight, an early age-to-market i s usually-a good i n d i c a t i o n of an ef«r f i c i e n t animal. But where hogs are s e l f fed, or fed according to t h e i r own growth rate, age-to-market i s not always a true i n d i c a t o r of feed e f f i c i e n c y , f o r as shown by the experiment, one pig may require 15 days longer to reach 190 pounds than h i s l i t t e r mate, but the feed consumption of the two can be nearly equal. The only accurate way to evaluate feed e f f i c i e n c y i n r e l a t i o n to age-to-market i s to measure the feed consumption and the gain of each hog. I f such measurements are taken, plus v i s u a l evaluation of type, then the true e f f i c i e n c y of any pig can be determined and selected f o r i n a breeding program. As shown by other n u t r i t i o n studies with swine, boars exhibit a decisive margin i n rate of growth, feed e f f i c i e n c y and hence age-to-market, over g i l t s . The regression of body weight against time at weekly i n t e r v a l s between b i r t h and 200 pounds demonstrates the decided l i n e a r i t y of growth at the various stages of development plus the ever decreasing percentage growth rate. At such time that i t i s possible to determine accurately the amount of f a t and protein deposited at any instant, an absolute evaluation of the Instantaneous Growth Rate equation cannot be made. At present i t might be stated that the equation comes f a i r l y close to providing a mathematical explanation of a b i o l o g i c a l phenomenon. The value of u t i l i z i n g Resting Energy Metabolism data and Energy Content of Gain data of swine when establishing feeding standards f o r swine needs further study, but I t might - 160 -be stated that the present values as applied i n compiling the feeding standards for the Yorkshire swine population i n the experiment met f a i r l y c losely the actual requirements of the animals tested. Nine of the 10 pigs of L i t t e r No. 5 consumed within 3 pounds of t h e i r t h e o r e t i c a l weekly feed requirement. Between the body weights of 60 and 190 pounds, 70 per cent of the pigs tested had an actual feed e f f i c i e n c y within .15 pounds of feed per pound of gain of t h e i r expected feed e f f i c i e n c y . The l a t t e r r e s u l t s provide further evidence of the v a l i d i t y of the Growth Constants or K values as obtained from the Instantaneous Relative Growth rate equation as they were used i n c a l c u l a t i n g feed requirements and feed e f f i c i e n c y . The pigs that gain most rapid l y do not always develop the best carcass, but there are d e f i n i t e exceptions, and c e r t a i n factors have an extreme e f f e c t on the carcass grade obtained. One of these i s the f i n a l weight at which pigs are slaughtered. I f a rapidly growing pig i s allowed to reach 205 pounds or better, then the p o s s i b i l i t y of the carcass being graded A i s small as at t h i s weight the rate of f a t deposition i s very f a s t and the t o t a l f a t deposited great. I f a rapi d l y growing pig i s slaughtered between 190 and 195 pounds, the p o s s i b i l i t y of obtaining a Grade A carcass i s good as the t o t a l f a t deposited, e s p e c i a l l y i n the l o i n and shoulder area, i s not as great as f o r a pig slaughtered over 205 pounds. But In the o v e r a l l analysis a rapid rate of gain coupled with a. low feed require-ment are precursors to a Grade A carcass. The experiment has demonstrated variati o n s of 22 per cent f o r economic characters of swine i n a c l o s e l y related - 161 -population fed under controlled conditions. Since these varif^.: ations are quite r e a l , i t i s essential that a d e f i n i t e program be followed when establishing economic l i n e s . Probably the most accurate method of selecting breeding stock that are e f f i c i e n t , i s to measure the growth rate and feed consumption of individuals over a precise weight range. Feed e f f i c i e n c y data of i n d i v i d u a l hogs, coupled with type, reproductive a b i l i t y and milk production, can be used as a sound basis f o r selecting future breeding stock. By mating the most e f f i c i e n t animals and maintaining high producing l i n e s , a rapid growing, economical hog could be developed to produce a carcass that would q u a l i f y as Grade A under the present Canadian Hog Carcass Grading Standards. - m2 -IV. GENERAL SUMMARY 1. Calculations from metabolism studies of growing p i g l e t s and milk output of sows demonstrated that the milk production of the sow l i m i t e d the genetic growth p o t e n t i a l of the rapidly growing suckling young. 2. I t was shown that a high energy well balanced creep rat i o n could offset the energy d e f i c i t to the suckling young. I t raised the mean weaning weight fo r a l l tested l i t t e r s by 9 pounds. 3. The suckling p i g l e t s that weaned at 37 pounds at eight weeks post-farrowing required 15 days less to reach 200 pounds than those that weighed 28 pounds at weaning. 4. Maximum growth rate of suckling p i g l e t s cannot usually be attained i f hemoglobin l e v e l s are below 12 to 14 grams per cent even when a high energy creep r a t i o n i s a v a i l a b l e . 5. Maximum growth rate of suckling p i g l e t s or maximum response to any treatment f o r hypoferrous anemia i s not attainable unless a high energy creep r a t i o n i s supplied. 6. A d a i l y o r al administration of copper and i r o n produced the most s a t i s f a c t o r y hemoglobin l e v e l s i n the suckling p i g l e t s . 7. Intramuscular Injections of i r o n and copper may have promise f o r the control of anemia but considerable research i s s t i l l required. 8. Market weights of 200 pounds at 150 days are quite possible for swine under the more recent n u t r i t i o n a l standards. 9. Considerable v a r i a b i l i t y existed between l i t t e r mates for rate of gain, (21 per cent) weight for age (45 days), feed e f f i c i e n c y (21 per cent) under conditions of equalized feed - 16S -intake at equal body weight and also where i n d i v i d u a l hogs were fed according to t h e i r own growth rate. Thus the Selection D i f f e r e n t i a l f o r any c h a r a c t e r i s t i c would appear to be great and the amount of improvement that could be expected i n any generation for a selected c h a r a c t e r i s t i c should be appreciable. 10. The only accurate way to evaluate feed e f f i c i e n c y i n r e l a t i o n to age-to-market would seem to be an accurate measurement of the feed consumption and rate of gain of Individual hogs at weekly i n t e r v a l s throughout the growth period. 11. As shown by other n u t r i t i o n studies with swine, boars exhibited a decisive margin i n rate of growth, feed e f f i c i e n c y and hence age-to-market over g i l t s . 12. The Instantaneous Relative Growth Rate equation would seem to provide, at present, one of the better mathematical expressions of growth. 13. The use of Resting Energy Metabolism and Energy Content of Gain data i n compiling feeding schedules for swine would seem sound as demonstrated by the r e s u l t s of the present experiment. 14. A rapid rate of gain coupled with a low feed requirement f o r gain are precursors to a Grade A hog carcass. 1 5 . The use of i n d i v i d u a l growth rate constants over the phases of l i n e a r i t y , plus resting energy metabolism and energy content of gain data for swine, would seem to provide for the expression of maximum differences between l i t t e r mates fo r c e r t a i n economic characters and would suggest further the v a l i d i t y of the Instantaneous Relative Growth Rate Equation. 16. The composition of the gain probably a f f e c t s the - 164 -rate of gain and the e f f i c i e n c y of the gain more than any other f a c t o r . 17. The method used i n feeding swine and the method used to measure growth rates and e f f i c i e n c y of feed conversion w i l l influence the values obtained f o r the l a t t e r two characters. - 165 -APPENDIX I A REVIEW OF THE BASIC FACTS OF BLOOD COMPOSITION, • IRON-HEMOGLOBIN RELATIONSHIPS AND TYPES OF ANEMIA AFFECTING PRE AND POST-WEANING GROWTH RATES IN YORKSHIRE SWINE. The complexities of any problem concerning anemia are not f u l l y appreciated u n t i l a glance i s taken at the mass of data compiled by Wintrobe and presented i n his recent text " C l i n i c a l Haemataology" (1952) or at the work of Parker published i n a volume e n t i t l e d "Textbook of C l i n i c a l Pathology" (1948). The writer w i l l confine his discussion of anemia to a very small portion of t h i s vast f i e l d . Iron anemia i s a c r i t i c a l problem where p i g l e t s are raised i n drylot without access to s o i l or other i r o n supplements. 1. BLOOD CONSTITUENTS In order to have an understanding of hypoferrous anemia the proximate composition of blood must f i r s t be known. A b r i e f outline of blood constituents i s presented below. Blood i s composed of: 1. plasma and, 2. blood c e l l s . 1. Blood Plasma: Blood Plasma i s a l i g h t yellow viscous f l u i d contributing 55 percent of the t o t a l blood volume, and consisting of proteins, organic and inorganic substances, hormones, antibodies and excretory products. The plasma acts as a storehouse and c a r r i e r for the above nutrients, also i t transports the blood c e l l s through the c i r c u l a t o r y system. 2. 31ood C e l l s : The remaining 4 5 per cent of the - 166 -t o t a l blood volume Is made up of three- kinds of blood c e l l s : (a) Erythrocytes or red c e l l s . (b) Leukocytes or white c e l l s . (c) Thrombocytes or p l a t e l e t s . Erythrocytes - are biconcave, c i r c u l a r , non nucleated c e l l s with a semipermeable membrane re a d i l y penetrated by oxygen molecules. The s o l i d c e l l i n t e r i o r i s 8 0 to 9 0 per cent hemo-globin. The primary function of the erythrocyte i s to transfer hemoglobin i n combination with oxygen or carbon dioxide' to and from the tissues and lungs. Pigs blood contains approximately 6 , 3 0 0 , 0 0 0 erythro-cytes per cu. m.ra. Leukocytes - or white c e l l s are larger nucleated c e l l s containing no hemoglobin, are fewer In number i n a r a t i o of 1 leukocyte to 6 0 0 erythrocytes. They are divided into two morphological c l a s s i f i c a t i o n s : ( i ) Non-granular leukocytes and ( i i ) Granular leukocytes or granulocytes. The primary function of leukocytes i s t h e i r phagocytic action against invading bacteria. Blood P l a t e l e t s - which are not a c t u a l l y c e l l s , are an i n t e g r a l part of the blood c l o t t i n g process. 2. TYPES OF ANEMIA The general term of anemia refers to any abnormal condition of the blood usually characterized by a decrease i n hemoglobin content and a reduction i n the number and volume of packed red c e l l s . The more recent method of c l a s s i f y i n g anemia i s based on the erythron concept whereby the erythrocytes and their - 167 -precursor, the bone marrow, are c l a s s i f i e d as one organ. Under the erythron c l a s s i f i c a t i o n three concepts are presented: (a) blood loss or increased blood destruction, e.g.hemo-. l y t i c anemias. (b) decreased blood production, e.g. n u t r i t i o n a l .deficiencies. (c) f a u l t y c e l l production. The older morphological method of c l a s s i f i c a t i o n d i f f e r e n t i a t e s changes i n size, shape and hemoglobin content of the erythrocytes. Four morphological anemias are recognized: (1) Normocytic, whereby there i s no change i n c e l l size and hemoglobin content but rather the t o t a l number of c e l l s i s reduced, therefore, the t o t a l hemoglobin content and the packed c e l l volume are reduced. Normocytic anemia may r e s u l t from d i l u t i o n of the blood by excess f l u i d , lack of blood formation, sudden loss of blood from hemorrhage or by increased blood destruction as i n the hemolytic anemias. (2) Macrocytic, whereby i n d i v i d u a l c e l l volume i s increased, but t o t a l c e l l volume, t o t a l hemoglobin content and packed c e l l volume a l l remain normal. The production of large immature erythrocytes, call e d r e t i c u l o c y t e s , i s often a r e s u l t of an imbalance i n hematopoietic stimulus a r i s i n g from a deficiency of " i n t r i n s i c " or " e x t r i n s i c " factors which are both essential for erythropoiesis. (3) Microcytic, whereby red c e l l size i s reduced with no reduction i n c e l l u l a r hemoglobin. (4) Hypochromic Microcytic, whereby c e l l size i s re-- 168 -duced and, for a given packed c e l l volume, hemoglobin content i s lowered. Hypochromic microcytic anemia characterizes the one most commonly found i n suckling p i g l e t s and i s a re s u l t of continuous i r o n depravation, or i n e f f i c i e n t i r o n absorption. In pre-natal n u t r i t i o n there may be i n s u f f i c i e n t i r o n i n the diet or i n s u f f i c i e n t absorption to meet the demands of develop-ing young, esp e c i a l l y i n multiparous species. In post-natal n u t r i t i o n of the pig l e t s u f f i c i e n t iron i n the sow's ratio n does not ensure adequate i r o n i n the milk for the offspring due to a barrier at the mammary gland. 3. IRON-HEMOGLOBIN RELATIONSHIPS The erythrocyte, i s a very complex chemical unit, containing 60 per cent water and 40 per cent s o l i d s . Of the sol i d s about 90 per cent is:hemoglobin, while the remainder of the solids are made up of: stroma, the insoluble material, which remains when red corpuscles are hemolyzed; a g l y c o l y t i c enzyme system which serves to maintain the hemoglobin i n the reduced or ferrous state; catalase to protect the heme from peroxide decomposition; carbonic anhydrase to a i d i n the transport of carbon dioxide as bicarbonate ions and numerous other constituents, organic and inorganic. Of the t o t a l i r o n stores i n the body 3 to 5 per cent are present i n muscle myoglobin and 60 to 70 per cent are held i n the blood compound hemoglobin. Iron i s generally u t i l i z e d most e f f e c t i v e l y as an inorganic io n i c complex. While ga s t r i c hydrochloric acid tends to oxidize ferrous i r o n to the f e r r i c state, c e r t a i n food substances tend to maintain the iro n i n the - 169 -ferrous state; the condition i n which i t i s absorbed by the mucosal c e l l s of the g a s t r o - i n t e s t i n a l t r a c t . A p o f e r r i t i n , a protein present i n the mucosal c e l l s , as well as i n the l i v e r , spleen and bone marrow, has a marked a f f i n i t y for ferrous i r o n i n the intestine and when taken up i t becomes f e r r i t i n with the i r o n now i n the f e r r i c state. In the next step beta prime globulin of the blood picks up the i r o n from f e r r i t i n ; the f e r r i c iron has to be reduced to the ferrous state before i t can be taken up by beta prime globulin which i n turn holds the i r o n i n the f e r r i c state again. Thus the o v e r a l l process i s a series of equilibrium reactions, a l l dependent on the amount of iron required for the formation of red blood c e l l s , but each step i n the chain being a l i m i t i n g one. Therefore, only a limited amount of i r o n can be taken up at one time and hence the absolute necessity of a constant supply present i n the i n t e s t i n e . The'complete metabolic pathway of i r o n has been pre-sented by Cartwright and i s here taken from Wintrobe ( 1 9 5 2 ) . Notable i n the following diagram i s the small amount of i r o n that i s l o s t from that absorbed. - 170 -Metabolic Pathways Of Iron Diet Tissues Organic *\ Iron Inorganic/ Fe+ + Fe+++ T Stomach FeX ^Fe*-»-+-fX i o n i z a t i o n by HC1 1 Erythrocyte Destruction F e r r i t i n (Fef+ +) Verdohemoglobin F e ± + + _ Labile Iron . Pool Hemosiderin (Fe + + +) Haeme Enzvmes ( F e + + ) B i l i r u b i n Small Intestine '/ Fef*" F e r r i t i n Reduction . Fe+_,-:t_>Fe-«- + \ Plasma R.B.C. Transferrin (Fe +  + -f» a,, Globulin) Faeces JL Unabsorbed Organic and Inorganic Fe Urine Sweat Saliva Nails Hair F Hgb (Fe++) Bone Marrow Fe + + +protoporphyrin->Eaeme Haeme+Globin*Hemoglobin ( F e + + ) (Fe++'t-) i - 171 -CHEMICAL STRUCTURE OF HAEME - 172 -Hemoglobin, the esse n t i a l oxygen carrying constituent of the blood, i s formed within the erythrocytes from porphyrin precursors and the protein g l o b u l i n . The structure of haeme i s taken from Wintrobe ( 1 9 5 2 ) . From t h i s diagram we see that the basis of haeme i s four pyrrole rings with a l i p h a t i c substituted groups present on the p-p-*- positions of the rings, joined together by single carbon bridges. Four of' these haeme molecules are attached to one globin molecule thus each hemoglobin molecule possesses four atoms of i r o n since each haeme prosthetic group contains one atom of i r o n i n i t s nucleus. The iron has a co-ordination valence of si x , four being attached to the four pyrrole nitrogens, the f i f t h to the amino acid h i s t i d i n e of the globin molecule and the sixth- to an oxygen molecule. Linkages from the two pyruvic acid residues on the prosthetic group form the main bond strengths of the haeme-globin union. Hemoglobin of pigs' blood consists of 0 . 3 3 9 per cent i r o n with a molecular weight of 6 5 , 8 8 8 grams. - 17S -APPENDIX II ARITH-LOG PLOTS OF WEEKLY WEIGHT. DATA OF THE 28  EXPERIMENTAL PIGS FROM BIRTH TO 200 POUNDS. 1000 900 o 50 0 1 0 20 3 0 40 50 6 0 70 80 90 100 110 120 130 HO 150 160 170 1«0 190 200 210 22C AGE IN DAYS 1000 1 0 0 0 A G E I N D A Y S - 174 -APPENDIX III THE CALCULATION OF GROWTH CONSTANTS OR K VALUES OF YORKSHIRE HOGS BY USE OF THE METHOD OF LEAST SQUARES FOR SMOOTHING DATA. The method used to calculate the growth constants or K values over the phases of linearity in the growth cycle, when body weight was regressed against time on an arith-log grid, was the method of Least Squares for smoothing data. The relationship of the equation obtained, for any phase of linearity, to the Instantaneous Relative Growth Rate Equation w i l l be demonstrated. The example cited w i l l be a calculation of the growth constant for the third phase of linearity, from 21 days to weaning at 56 days, of the hog that was used as a standard for the feeding schedule of Litter Nos. 2 , 3 and 4 . (Age) Time = weeks 3 (Body Weight of Pig) x w = weight In w = y 15 2 . 7 0 8 " 2 x.y yi 8 . 1 5 9 4 21 3.044 1 2 . 2 16 5 27 3 . 2 9 6 1 6 . 4 5 2 5 6 34 3 . 5 2 6 2 1 . 2 36 7 42 3 . 7 3 7 2 6 . 1 5 4 9 ' £ ( X ) : : 25 -£(y) = l 6 : . 3 i l £(x.y) r n = 5 £ (y) = na + i ( x ) b 9 (1) :£(xy) = £(x) a + .i(x 2) b (2) 5 x (1) 1 6 . 3 1 1 - 5a 25b 8 1 . 5 5 = 25a+• 125b (3) - 175 -8 4 . 1 5 - 25 a * 135 b 8 1 . 5 5 = 25 a + 125 b 2 . 6 0 = 10 b b = . 2 6 0 a = 1 . 9 6 5 y z 1 . 9 6 5 +• . 2 6 0 x The Instantaneous Relative Growth.Rate Equation, kt K = In w2 - In ir-± or i t s integrated equation W = Ae t i =~~F[ which Is the equation for a monomolecular reaction, can be broken down to: Kt s In W2 - In w^  Kt s In w - In A where w = weight at time t A m weight at time 0 (conception) t s time interval between t 2 - t x or In w • In A 4> Et i s synonymous with the equation for a straight line, y - a + b x, where In w - y, In A - a and Kt - bx. Thus In w 5 1 . 9 6 5 + . 2 6 0 t, where K i s equal to b. Hence the growth constant for the hog i n the example between three weeks and eight weeks post-farrowing was 2 6 . 0 per cent per week or 3 . 7 0 per cent per day when multiplied by 1 0 0 . Therefore, at 35 pounds body weight the pig would be gaining 3 5 x 3.70 = 1 . 3 0 pounds per day. •- 100 Since the two equations are synonymous, any growth reaction, when plotted on an arith-log grid, w i l l have the reaction rate K = In w2 - In w-,. t 2 - t x -176-APPENDIX IV INBREEDING OF EXPERIMENTAL PIGS. The pigs are the progeny of 4 g i l t s which are f u l l sister. The sire of these experimental pigs i s also their great grandsire. Therefore, they w i l l a l l have the same degree of inbreeding. These pigs w i l l be represented by the letter "G" in the inbreeding formula. Inbreeding Formula: Fx = ( J (n-1)) F a Inbreeding x = The animal in question n = The number of paths i n any closed c i r c l e Pedigree: G Colony Wonder 1387 A 1 - 3 3 1 7 7 3 -\f66F-420899') Colony Wonder 487 E J67F-420900U • -391076-68F-420901J 169F-420902J (Number of paths in closed cir c l e - 4) 0 O O F s ^ (4-1) - £3 s 12.5J8 inbred PEDIGREE OF EXPERIMENTAL PIGS 200G 201G 204G • Pavillion Wonder 6X 205G [ -277454-206G ^ S i r e : Colony Wonder 13&7A 207G / - 3 3 1 7 7 3 -211G 212G 214G x Colony Barbara Malta 215G . 480Y - 2 9 0 2 3 1 -218G 221G 230G 231G 232G 234G 237G I / Colony Wonder 487E 238G I ( -39IO76-240H NDams: 66F -420899-241H 67F -420900-242H 68F -420901-243H 69F -420902-244H 245H NBellavista 39B 246H -342620-247H 248H 249H /'College King 70W -246854-Shur Gain Lady 273V - 2 6 0 6 8 4 -rColony Malte 28W - 2 3 9 9 3 5 -^ Colony Barbara 1005 -199613 /^Colony Wonder I387A - 3 3 1 7 7 3 -* Colony Daisy Empress 1142Y - 2 9 4 9 2 6 -Bellavista 325Z - 3 1 5 2 3 2 -• Bellavista 33Z - 3 2 9 5 3 2 -- 178 -VI. 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