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Genetic and environmental factors influencing growth in the chicken Deland, Michael Campbell 1965

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GENETIC AND ENVIRONMENTAL FACTORS INFLUENCING GROWTH IN THE CHICKEN by MICHAEL CAMPBELL DELAND B.S.A., University of B r i t i s h Columbia, 1963 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of Poultry Science We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA AUGUST, 1965 I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y , I f u r t h e r a g r e e t h a t p e r -m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e Head o f my D e p a r t m e n t o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t , c o p y i n g o r p u b l i -c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n , . D e p a r t m e n t o f P o u l t r y Science The U n i v e r s i t y o f B r i t i s h Columbia-, V a n c o u v e r 8, C a n a d a D a t e A u g u s t 10th, 1965 i i ABSTRACT A comparison was made of r a t e s of growth and body weights between pre- and post-hatching stages of development of the chicken as a f f e c t e d by s t r a i n s or s t r a i n crosses, egg storage, egg weights, time of hatch, sex and post-hatching n u t r i t i o n a l environment. The i n t e r r e l a t i o n s h i p s of these f a c t o r s were a l s o i n v e s t i g a t e d . The r e s u l t s of the i n v e s t i g a t i o n i n d i c a t e that p r a c t i c -a l l y a l l of the v a r i a t i o n of six-week body weight i n t h i s data was s u c c e s s f u l l y accounted f o r by the combined e f f e c t s of six-week growth r a t e , hatching weight and embryonic growth r a t e between eight and twelve days. The data a l s o i n d i c a t e that gains i n six-week body weight may be made by s e l e c t i n g f o r e a r l y growth r a t e without con-comitant change i n other t r a i t s . Hatching time, hatching weight and post-hatching growth appear to be a f f e c t e d by egg storage only i f some form of s t r e s s i s present during i n c u b a t i o n . In the absence of s t r e s s i t appears that a compensatory increase i n r a t e of embryonic growth overcomes the e f f e c t of a delayed i n i t i a t i o n of growth caused by egg storage. A s i g n i f i c a n t i n f l u e n c e of sex on embryo weight i n favour of the male embryos was observed. TABLE OF CONTENTS INTRODUCTION REVIEW OF THE LITERATURE MATERIALS AND METHODS Experiment 1 Experiment 2 STATISTICAL METHODS RESULTS AND DISCUSSION Experiment 1 Embryo Weights Embryo Growth Rates Post-hatching Body Weights (Males) Post-hatching Growth Rates (Males) Post-hatching Body Weights (Females) Post-hatching Growth Rates (Females) Embryo Correlations Post-hatching Correlations Correlations of Embryo and Post-hatching Data Within "Genotypes" Experiment 2 Embryo Weights Embryo Growth Rates Post-hatching Body Weights (Males) i i i Page 1 2 10 11 15 17 20 20 20 22 25 27 29 31 32 33 36 37 37 40 43 i v Page Post-hatching Growth Rates (Males) 4 5 Post-hatching Body Weights (Females) 1+6 Post-hatching Growth Rates (Females) 4 8 Embryo Correlations 5 1 Post-hatching Correlations 52 Correlations of Embryo and Post-hatching Data Within "Genotypes" 5 4 Further Discussion of Storage Effects on Embryo • Weights and Growth Rates 5 9 SUMMARY 60 BIBLIOGRAPHY 67 V LIST OF TABLES Table Page I S t a t i s t i c a l Models f o r Analyses of Variance of Embryo Data 70 II F Values From the Analyses of Variance of Em-bryo Weights Recorded at 12, 14, 16 and 18" Days of Incubation Using S t a t i s t i c a l Model (a): Experiments 1 and 2 71 III Percentage Sums of Squares From the Analyses of Variance of Embryo Weights at Two Day In-ter v a l s from 6 to 18 Days of Incubation: Experiment 1 73 IV E f f e c t of Duration of Pre-incubation Egg Stor-age on Embryo Weights Recorded at Two Day Intervals from 6 to 18 Days of Incubation: Experiment 1 74 V Ef f e c t of Sire Line on Embryo Weights Recorded at Two Day Intervals From 6 to 18 Days of In-cubation: Experiment 1 75 VI E f f e c t of Dam Line on Embryo Weights Recorded at Two Day Intervals From 6 to 18 Days of In-cubation: Experiment 1 76 v i Table Page VII E f f e c t of Sex on Embryo Weights Recorded at Two Day Intervals From 12 to 18 Days of Incubation: Experiment 1 77 VIII Percentage Sums of Squares From the Analyses of Variance of Embryo Growth Rates During Succes-sive Two Day Intervals Between 6 and 18 Days of Incubation: Experiment 1 76 IX E f f e c t of Duration of Pre-incubation Egg Storage on Embryo Growth Rates During Successive Two Day Intervals from 6 to 18 Days of Incubation: Experiment 1 79 X E f f e c t of Sire Line on Embryo Growth Rates Dur-ing Successive Two Day Intervals From 6 to 18 Days of Incubation: Experiment 1 80 XI E f f e c t of Dam Line on Embryo Growth Rates During Successive Two Day Intervals From 6 to 18 Days of Incubation: Experiment 1 81 XII Percentage Sums of Squares From the Analyses of Variance of Embryo Growth Rates When Averaged for Intervals Beginning at 6 or 6 Days of In-cubation: Experiment 1 82 XIII E f f e c t of Egg Storage on Averaged Two Day Embryo Growth Rates: Experiment 1 63 y n Table XIV XV XVI XVII XVIII XIX XX XXI E f f e c t of S i r e L i n e on Averaged Two Day Em-bryo Growth Rates: Experiment 1 E f f e c t of Dam Line on Averaged Two Day Em-bryo Growth Rates: Experiment 1 Percentage Sums of Squares From the Analyses of Variance of Male Body Weights at Weekly I n t e r v a l s from Hatch to 6 Weeks of Age: Experiment 1 E f f e c t of S i r e L i n e on Body Weights of Male Chicks at Weekly I n t e r v a l s from Hatch to 6 Weeks of Age: Experiment 1 Page 84 85 86 87 Means and Standard Dev i a t i o n s of Pre- and Post-Storage Egg Weights, According t o Dam Line and Sex of Hatched Chicks 88 E f f e c t of Dam Line on Body Weights of Male Chicks at Weekly I n t e r v a l s From Hatch to 6 Weeks of Age: Experiment 1 89 E f f e c t of Ration on Body Weights of Male Chicks at Weekly I n t e r v a l s From Hatch to 6 Weeks of Age: Experiment 1 90 Percentage Sums of Squares From the Analyses of Variance of Weekly and Average Growth Rates of v i i i Table Page XXII Male Chicks From Hatch to 6 Weeks of Age: Experiment 1 E f f e c t of S i r e Line on Growth Rates of Male Chicks During Weekly I n t e r v a l s From Hatch to 6 Weeks of Age: Experiment 1 91 92 XXIII XXIV XXV XXVI XXVII E f f e c t of Dam Li n e on Growth Rates of Male Chicks During Weekly I n t e r v a l s From Hatch t o 6 Weeks of Age: Experiment 1 93 E f f e c t of Ration on Growth Rates of Male Chicks During Weekly I n t e r v a l s From Hatch to 6 Weeks of Age: Experiment 1 94 Percentage Sums of Squares From the Analyses of Variance of Female Body Weights at Weekly I n -t e r v a l s From Hatch to 6 Weeks of Age: Experiment 1 95 E f f e c t of S i r e Line on Body Weights of Female Chicks at Weekly I n t e r v a l s From Hatch to 6 Weeks of Age: Experiment 1 96 E f f e c t of Dam Line on Body Weights of Female Chicks at Weekly I n t e r v a l s From Hatch t o 6 Weeks of Age: Experiment 1 97 i x Table XXVIII Page XXIX XXX XXXI XXXII XXXIII XXXIV E f f e c t of Ration on Body Weights of Female Chicks at Weekly I n t e r v a l s From Hatch to 6 Weeks of Age: Experiment 1 9S E f f e c t s of S i r e x Dam I n t e r a c t i o n on Weekly Body Weights of Female Chicks: Experiment 1 99 Percentage Sums of Squares From the Analyses of Variance of Weekly and Average Growth Rates of Female Chicks From Hatch to 6 Weeks of Age: Experiment 1 100 E f f e c t of S i r e Line on Growth Rates of Female Chicks During Weekly I n t e r v a l s From Hatch to 6 Weeks of Age: Experiment 1 101 E f f e c t of Dam Line on Growth Rates of Female Chicks During Weekly I n t e r v a l s From Hatch to 6 Weeks of Age: Experiment 1 102 E f f e c t of Ration on Growth Rates of Female Chicks During Weekly I n t e r v a l s From Hatch to 6 Weeks of Age: Experiment 1 103 Simple C o r r e l a t i o n s of Pre and Post Storage Egg Weights and Date of Lay wit h Embryo Weights and Date of Lay at Two Day I n t e r v a l s Between 6 and 18 Days of Incubation: Experiment 1 104 Table XXXV XXXVI XXXVII XXXVIII XXXIX XL Page C o r r e l a t i o n C o e f f i c i e n t s of Hatching Time, S t o r -age Period and Pre- and Post-storage Egg Weights w i t h Chick Body Weights. From Hatch t o 6 Weeks of Age: Experiment 1 10$ C o r r e l a t i o n C o e f f i c i e n t s of Hatching Time, Date of Lay, Pre- and Post-storage Egg Weights and 6 Week Body Weight w i t h Weekly Growth Rates Bet-ween Hatch and 6 Weeks of Age; Experiment 1 106 C o r r e l a t i o n C o e f f i c i e n t s of 6 Week Body Weight With Embryo Weights, Embryo Growth Rates, Chick Weights and Chick Growth Rates W i t h i n Each Sex and R a t i o n . C a l c u l a t i o n s Based on Genotypic Averages: Experiment 1 107 C o r r e l a t i o n C o e f f i c i e n t s of Hatch to 6 Week Average Growth Rate With Embryo Growth Rates Within Each Sex and Rati o n : Experiment 1 Percentage Sums of Squares From the Analyses of Variance of Embryo Weights at Two Day I n -t e r v a l s From 6 to 18 Days of Incubation: Experiment 2 E f f e c t of Duration of Pre- i n c u b a t i o n Egg S t o r -age on Embryo Weights Recorded at Two Day I n t e r v a l s From 6 t o 18 Days of Incubation: Experiment 2 109 110 111 Table XLI X L I I X L I I I XLIY XLV XLVI XLVII x i Page E f f e c t of S i r e Line on Embryo Weights Recorded at Two Day I n t e r v a l s From 6 t o 18 Days of I n -cubation: Experiment 2 112 E f f e c t of Dam Line on Embryo Weights Recorded at Two Day I n t e r v a l s From 6 to 18 Days of Incuba-t i o n 113 E f f e c t of Sex on Embryo Weights Recorded at Two Day I n t e r v a l s From 10 t o 18" Days of Incuba-t i o n : Experiment 2 114 Percentage Sums of Squares From the Analyses of Variance of Embryo Growth Rates During Succes-s i v e Two Day I n t e r v a l s Between 6 and 18 Days of Incubation: Experiment 2 115 E f f e c t of Duration of P r e - i n c u b a t i o n Egg Storage on Embryo Growth Rates During Successive Two Day I n t e r v a l s From 6 t o 18 Days of Incubation: Experiment 2 116 E f f e c t of S i r e Line on Embryo Growth Rates Dur-i n g Successive Two Day I n t e r v a l s From 6 to 18 Days of Incubation: Experiment 2 117 E f f e c t of Dam Line on Embryo Growth Rates During Successive Two Day I n t e r v a l s From 6 to 18 Days of Incubation: Experiment 2 118 x i i Table Page XLVIII Percentage Sums of Squares From the Analyses of Variance of Embryo Growth Rates When Averaged For Intervals Beginning at 6 or 8 Days of In-cubation: Experiment 2 119 XLIX E f f e c t of Egg Storage on Averaged Two Day Embryo Growth Rates: Experiment 2 120 L E f f e c t of Sire Line on Averaged Two Day Embryo Growth Rates: Experiment 2 121 LI E f f e c t of Dam Line on Averaged Two Day Embryo Growth Rates: Experiment 2 122 LII Percentage Sums of Squares From the Analyses of Variance of Male Body Weights at Weekly Intervals From Hatch to 6 Weeks of Age: Experiment 2 123 L I I I E f f e c t of Sire Line on Body Weights of Male Chicks at Weekly Intervals From Hatch to 6 Weeks of Age: Experiment 2 124 LV E f f e c t of Dam Line on Body Weights of Male Chicks at Weekly Intervals From Hatch to 6 Weeks of Age: Experiment 2 125 LVI Ef f e c t of Ration on Body Weights of Male Chicks at Weekly Intervals From Hatch to 6 Weeks of Age: Experiment 2 126 X l l Page Percentage Sums of Squares From the Analyses of Variance of Weekly and Average Growth Rates of Male Chicks From Hatch to 6 'Weeks of Age: Experiment 2 127 E f f e c t of Sire Line on Growth Rates of Male Chicks During Weekly Intervals From Hatch to 6 Weeks of Age: Experiment 2 128 Ef f e c t of Dam Line on Growth Rates of Male Chicks During Weekly Intervals From Hatch to 6 Weeks of Age: Experiment 2 129 E f f e c t of Ration on Growth Rates of Male Chicks During Weekly Intervals From Hatch to 6 Weeks of Age: Experiment 2 130 Percentage Sums of Squares From the Analyses of Variance of Female Body Weights at Weekly In-tervals From Hatch to 6 Weeks of Age: Experiment 2 131 E f f e c t of Sire Line on Body Weights of Female Chicks at Weekly Intervals From Hatch to 6 Weeks of Age: Experiment 2 132 E f f e c t of Dam Line on Body Weights of Female Chicks at Weekly Intervals From Hatch to 6 Weeks of Age: Experiment 2 133 x i v Table Page LXIV E f f e c t of Ration on Body Weights of Female Chicks at Weekly Intervals Frqm Hatch to 6 Weeks of Age: Experiment 2 134 LXV Percentage Sums of Squares From the Analyses of Variance of Weekly and Average Growth Rates of Female Chicks From Hatch to 6 Weeks of Age: Experiment 2 135 LXVI E f f e c t of Sire Line on Growth Rates of Female Chicks During Weekly Intervals From Hatch to 6 Weeks of Age: Experiment 2 136 LXVII E f f e c t of Dam Line on Growth Rates of Female Chicks During Weekly Intervals From Hatch to 6 Weeks of Age: Experiment 2 137 LXVIII E f f e c t of Ration on Growth Rates of Female Chicks During Weekly Intervals From Hatch to 6 Weeks of Age: Experiment 2 138 LXIX Simple Correlations of Pre- and Post-storage Egg Weights and Date of Lay With Embryo Weights and Date of Lay at Two Day Intervals Between 6 and 18 Days of Incubation: Experiment 2 139 LXX Correlation C o e f f i c i e n t s of Hatching Time, Stor-age Period and Pre- and Post-storage Egg Weights With Chick Body Weights From Hatch to 6 Weeks of Age: Experiment 2 140 XV Table Page LXXI C o r r e l a t i o n C o e f f i c i e n t s of Hatching Time, Date of Lay, Pre- and. Post-storage Egg Weights and 6 Week Body Weight With Weekly Growth Rates Between Hatch and 6 Weeks of Age: Experiment 2 141 LXXII C o r r e l a t i o n C o e f f i c i e n t s of 6 Week Body Weights With Embryo Weights, Embryo Growth Rates, Chick Weights and Chick Growth Rates W i t h i n Each Sex and Ration. C a l c u l a t i o n s Based on Genotypic Averages: Experiment 2 142 LXXIII C o r r e l a t i o n C o e f f i c i e n t s of Hatch to 6 Week Av-erage Growth Rate With Embryo Growth Rates Within Each Sex and Rati o n : Experiment 2 144 LXXIV C o e f f i c i e n t s of Determination (100 2) of the Geno-t y p i c Estimates of 6 Week Body Weight W i t h i n Each Sex and R a t i o n , M u l t i p l y Regressed on Selec-ted "Genotypic" T r a i t s : Experiment 2 145 A C K N O W L E D G E M E N T The writer wishes to express his appreciation to Dr. CW. Roberts, Assistant Professor, and Dr. J.R. Richards, Assistant Professor, Department of Poultry-Science, for t h e i r c r i t i c i s m of t h i s manuscript, and to those members of the Faculty who read the manuscript and. offered t h e i r advice. The writer i s also indebted to Mr. Herbert E l l i s , Farm Supervisor, and others who provided essen-t i a l help i n gathering and recording the data. INTRODUCTION Breeding programmes f o r the development of b r o i l e r s t r a i n s of chickens have generally placed primary emphasis on improvement of body weight and conformation at market age. The use of body weights as the c r i t e r i a for s e l e c t i o n to increase early growth has tended over the years to increase egg size and lower egg production. I t would accordingly be of value i f some other t r a i t , independent of egg size or production, could be ut-i l i z e d i n s e l e c t i o n programmes to achieve body weight gains. Recent work (Roberts, I964) has indicated that growth from hatching to seven weeks of age may be represented by a power function y - at 1 3; where y_ i s the body weight of an i n d i v i d u a l at time t, a i s equal to the body weight of that i n d i v i d u a l at time zero and b represents the growth rate of the i n d i v i d u a l . In theory, then, t h i s function i s independent of any other t r a i t such as egg size and i t i s possible that s e l e c t i o n for increase of the i n d i v i d u a l growth rate may be unassociated with change i n other t r a i t s . The present study was undertaken to investigate further the value of the i n d i v i d u a l growth rate, as a measure of genetic worth, i n the pre-hatching stage as compared to the post-hatching stage when measured over a number of s t r a i n s and s t r a i n crosses. Also investigated were the i n t e r r e l a t i o n s h i p s of duration of pre-2 incubation storage, egg weights before and a f t e r storage, hatch-ing time and l e v e l of n u t r i t i o n during post-hatching growth, and t h e i r e f f e c t s on the i n d i v i d u a l growth rate. REVIEW OF THE LITERATURE Halbersleben and Mussehl (1922), among the e a r l i e s t investigators of egg weight:chick weight re l a t i o n s h i p s , reported that when eggs were grouped according to weight, the average hatching weight of chicks from these groups, with minor excep-tions, were ranked i n the same order as the average egg weights. However, t h i r t y - f i v e days a f t e r hatching, the average weights of chicks from small egg groups were approximately the same as those of chicks from large egg groups. Upp (1928) reported that egg weight and chick weight at hatching were highly corre-lated but that neither observation formed a r e l i a b l e index of chick weights at two, four or twelve weeks of age. J u l l and Hewang (1930) pointed out that yolk material forms about 18 per cent of chick weight at hatch and that the c o r r e l a t i o n of egg and embryo weights increases during yolk assi m i l a t i o n . A study by Wiley (1950b) showed that the correlation c o e f f i c i e n t s between egg weight and body weight diminished grad-u a l l y from the t h i r d to the twelfth week, however, they were highly s i g n i f i c a n t u n t i l a f t e r the ninth week i n three out of four t e s t s . In contrast, Godfrey et a l . (1953) concluded that egg size exerts a ra p i d l y diminishing e f f e c t on body weight and 3 has no appreciable e f f e c t on b r o i l e r weight. They mentioned that t h i s r e l a t i o n s h i p might not hold true f o r a l l breeds. O'Neil (1950) reported that better feed consumption, lower mortality and higher body weights at eight weeks of age were achieved by chicks which had the highest percentage body weight of egg weight at hatching. Godfrey and Williams (1955), however, argued that the day-old chick weight as a percentage of egg weight accounted f o r only about 5 per cent of the v a r i a t i o n i n twelve-week body weight and was therefore of no value as an index to predict growth rate. Skoglund et a l . (1952) reported that chicks from larger eggs were heaviest at twelve weeks of age when a l l birds were reared together and the differences i n weight corresponded to those obtained i n an e a r l i e r study i n which chicks from d i f f e r e n t sized eggs were reared separately. In contrast, Tindel and Morris (1964) agreed that the chicks from heavy egg groups were heaviest at b r o i l e r age, regardless of whether they were reared separately or intermingled. However, they reported a strong tendency for chicks from any egg weight group to show increased weight gains when the groups were reared separately. In order to determine the influence of egg s i z e on the i n t r i n s i c growth of the chick, Kosin et a l . (1952) used body weight gain during i n t e r v a l s between weighing as a measure of growth rate. They concluded that egg size frequently exerts an 4 influence on subsequent growth up to twelve weeks, the effects of which are more prominent i n the early stages, but that breed and sex differences preclude any generalization. Regression analysis was used by Goodwin (1961) to i n -vestigate the e f f e c t of egg size or hatching weight on body weight at nine weeks. He found a greater e f f e c t of egg size between strains than within and suggested that chick size at hatching does have an important e f f e c t on i t s growth to nine weeks. Bray and Iton (1962) studied the i n t e r r e l a t i o n s h i p s of parental weight, embryo weights, egg weights and chick weights during the i n t e r v a l from s i x days of incubation to eight weeks af t e r hatching by ranking s t r a i n s according to these t r a i t s and determining the correlations of the ranks. They observed that egg weight exerted a temporary e f f e c t which concealed genetic differences i n l a t e embryonic and early post-hatching growth. Reports i n the l i t e r a t u r e indicate that there i s no doubt about the ef f e c t of egg size on hatching weight but opinions vary as to the duration of t h i s influence on subsequent body weight. The ef f e c t of breed on embryos has been studied almost as extensively as the ef f e c t of egg weight on embryo weight. Henderson (1930) was unable to detect any difference between the embryo weight of White Leghorns, Dark Cornish and the r e c i p r o c a l 5 crosses of these two breeds from four to twenty days of incubation. His observations consisted of duplicate samples of from four to s i x embryos, and, i n addition, the experimental error was possibly increased by incubating the pure l i n e embryos and the crossbred embryos at d i f f e r e n t times. In a study involving two s t r a i n s and t h e i r r e c i p r o c a l crosses, Byerly (1930) reported s l i g h t differences i n size" of em-bryos at the same stage of incubation and from eggs of the same si z e . These differences tended to disappear at hatching. Con-tinuing his studies of egg weight, breed and embryo weight i n t e r -r e l a t i o n s h i p s , Byerly (1932) proposed that each embryo has an inherent rate of growth which i s modified i n d i r e c t proportion to a function of egg s i z e . He thought, however, that the rate, function and proportion were each i d e n t i c a l f o r a l l breeds, regardless of egg s i z e . Blunn and Gregory (1935) were able to detect embryo-l o g i c a l differences between White Leghorns and Rhode Island Reds when compared by c e l l number and number of mitotic figures, but they were unable to demonstrate s i g n i f i c a n t differences i n weight. Some of these d i f f e r e n t findings were resolved by Byerly et a l . (1938) when they presented c r i t i c a l data which indicated that em-bryos of four genetic classes d i f f e r e d s i g n i f i c a n t l y i n s i z e dur-ing the eleven- to seventeen-day period, even i n eggs of s i m i l a r weight. A comparison of embryo weights, c e l l counts and c e l l 6 s i z e of two l i n e s of Barred Plymouth Rock which had been s e l e c t e d f o r l a r g e and sm a l l egg s i z e , r e s p e c t i v e l y , was made by Wiley (1950a). He d i d not f i n d c o n s i s t e n t d i f f e r e n c e s i n embryo weight between the two l i n e s , but d i d demonstrate t h a t egg s i z e was pos-i t i v e l y r e l a t e d t o c e l l number per u n i t area of embryo t i s s u e and n e g a t i v e l y r e l a t e d t o the c e l l s i z e . McNary et a l . ( i960) reported t h a t s i g n i f i c a n t genetic d i f f e r e n c e s were found between embryos of White Leghorns, Rhode I s l a n d Reds and New Hampshires i n the number of somites present a f t e r t h i r t y - e i g h t hours and i n embryo weights at one week and at two weeks of i n c u b a t i o n . Bray and I t o n (1962), i n a p r e v i o u s l y mentioned paper, a l s o observed genetic d i f f e r e n c e s i n embryo weights from the t e n t h t o nineteenth day of i n c u b a t i o n . Coleman et a l . (1964) found embryo weights of a l i n e s e l e c t e d f o r high body weight were s i g n i f i c a n t l y greater than those of a l i n e s e l e c t e d f o r low body weight, during the fou r t e e n -to nineteen-day pe r i o d of i n c u b a t i o n . However, at forty-two hours of i n c u b a t i o n the low weight l i n e had s i g n i f i c a n t l y higher somite counts. I n t e r e s t i n g l y , s i g n i f i c a n t c o r r e l a t i o n s between egg weight and embryo weight were found w i t h f a r greater frequency i n the low weight l i n e . E a r l y i n v e s t i g a t o r s of embryonic growth r a t e s tended i n general t o assume t h a t growth r a t e was constant during i n c u b a t i o n . Thus Murray (1925), p l o t t e d the l o g of embryo weight agai n s t l o g 7 of time and observed an apparently s t r a i g h t l i n e . He c a l c u l a t -ed the l e a s t squares l i n e of best f i t to the data and reported t h a t : "The average weight of chicken embryos between 5 and 19 days of i n c u b a t i o n as found by over 600 weighings may be ex-pressed by a simple exponential equation, W = K t 3 , D where K -0 . 6 6 8 " . In t h i s formula ¥ expresses embryo weight and t r e f e r s to time i n days from s t a r t of i n c u b a t i o n . Lerner (1939) exam-ined the d e v i a t i o n s from l i n e a r i t y present i n the data of Murray and others and reported t h a t : "While i n d i v i d u a l sets of data may produce a s a t i s f a c t o r y f i t t o a l o g a r i t h m i c s t r a i g h t l i n e , small d e v i a t i o n s i n the same d i r e c t i o n and appearing at the same time i n the m a j o r i t y of sets of r e l i a b l e data cannot be disregarded". B y e r l y et a l . ( 1 9 3 8 ) , i n a p r e v i o u s l y mentioned paper, used equations which r e l a t e l o g of weight to l o g of time to i n -v e s t i g a t e genetic d i f f e r e n c e s i n embryonic growth during the peri o d two t o twenty days of i n c u b a t i o n . They a l s o used a l e a s t squares e s t i m a t i o n and re p o r t e d that they were unable to detect any genetic d i f f e r e n c e s i n growth of embryos from eggs of the same s i z e . Examination of h i s f i g u r e s , however, r e v e a l s a con-s i d e r a b l e d i f f e r e n c e i n the p a t t e r n of d i s t r i b u t i o n of p o i n t s along the l i n e s of best f i t , among the f o u r genotypic c l a s s e s and one could question the v a l i d i t y of us i n g t h i s method to solve f o r growth constants during t h i s p e r i o d . In g e n e r a l , the more recent papers seem t o agree t h a t p r o v i d i n g enough genetic d i v e r s i t y i n p a r e n t a l body weight e x i s t s , 8 genetic, d i f f e r e n c e s i n embryo weight may be d i s t i n g u i s h e d . Op-i n i o n s seem to d i f f e r as to the d u r a t i o n of these genetic d i f f e r -ences i n embryo weight, and the work t h a t has been done on genetic d i f f e r e n c e s i n embryo growth r a t e s does not appear to be very c r i t i c a l . Lerner and Asmundson (193$), summarized the work t h a t had been done on growth constants and used Schmalhausen's growth constants, which are based on the p o s t u l a t e t h a t growth i s i n -v e r s e l y p r o p o r t i o n a l t o elapsed time, t o compare post-hatching growth r a t e s obtained from various sets of data. The use of these growth constants gave evidence of sex l i n k a g e and d i f f e r -ences between strains., breeds and sexes. As i n the embryo s t u d i e s , however, i n v e s t i g a t o r s were basing t h e i r c a l c u l a t i o n s on the premise t h a t growth curves could be d i v i d e d i n t o s e c t i o n s which, when reduced t o l o g a r i t h m i c s c a l e , would y i e l d s j s t r a i g h t l i n e s . Roberts (I964) i n v e s t i g a t e d the power f u n c t i o n y = at* 5 r e l a t e d to that o r i g i n a l l y proposed by Schmalhausen (as c i t e d by Lerner and Asmundson, 1938). He used the power func-t i o n to c a l c u l a t e weekly i n d i v i d u a l growth r a t e s d i r e c t l y from the data during the pe r i o d from hatch to ten weeks of age. In t h i s formula, age was expressed as time from conception. The r e s u l t s showed that the weekly growth r a t e s r e f l e c t e d a degree of l i n e a r i t y up t o seven or e i g h t weeks of age, and that when these weekly values to seven weeks of age are averaged, the seven-week 9 growth rate provides a useful estimate f o r comparison of genetic worth of individuals or s t r a i n s . Investigation of the e f f e c t of sex on embryo or hatched chick weight began with J u l l and Quinn (1925). They were unable to f i n d sex differences i n the hatching weight of chicks from eggs of hens or pu l l e t s of Rhode Island Red or Barred Plymouth Rock breeds. Monro and Kosin (1940), however, found that the hatch-ing weight of male chicks was s i g n i f i c a n t l y heavier than that of female chicks when expressed as a percentage of egg weight. Kagiama (cited by Monro and Kosin, 1940) reported s i g n i f i c a n t sex differences i n oxidation and reduction powers of male and female embryos which became apparent at t h i r t e e n days of incubation. This occurred at the same time as a sex difference i n embryo weight gain (no statement of significance) was observed. An invest i g a t i o n of sex differences i n weight of chicks hatched from eggs of si m i l a r weight was made by Godfrey and Jaap (1952), who showed that genotype may e f f e c t hatching weight of chicks (crossbreds versus purebreds) out of eggs from the same dam l i n e . They also claimed f i r s t conclusive evidence that genotype may e f f e c t hatching weight within each sex. The evidence i n the l i t e r a t u r e indicates that both sex and genotype e f f e c t the weights of chicks at hatching, but doubt remains as to the e f f e c t of sex on embryo weights during incubation. 10 A study of the e f f e c t of r a p i d i t y of hatching on growth, egg production, m o r t a l i t y and sex r a t i o s i n chickens showed th a t e a r l y emerging chickens grew s l i g h t l y f a s t e r i f removed from i n -cubator and given feed and water soon a f t e r hatching (Williams et a l . , 1951). In a l a t e r study, Bohren et a l . ( I96I) reported t h a t hatching time was l i n e a r l y r e l a t e d to l e n g t h of preincuba-t i o n egg storage. M e r r i t (1963) was able t o show th a t mean body weights at 42 , 6 3 , 147 and 31$ days were decreased by storage of hatching eggs f o r longer than two weeks p r i o r to i n c u b a t i o n , and that h a t c h a b i l i t y and v i a b i l i t y of hatched chicks decreased i n r e l a t i o n to storage time. The l i t e r a t u r e i n d i c a t e s that l i t t l e work has been done on sex d i f f e r e n c e s i n embryonic weights or embryonic growth r a t e s . N e i t h e r have the i n t e r r e l a t i o n s h i p s of length of egg storage, growth before and a f t e r i n c u b a t i o n and hatching time been i n v e s -t i g a t e d . A study of these f a c t o r s was t h e r e f o r e incorporated i n t o the present i n v e s t i g a t i o n . MATERIALS AND METHODS Three s t r a i n s ( l i n e s ) of chicken were used i n t h i s study: White Leghorn (WL), White Rock (WR) and New Hampshire (NH). The WL l i n e has been a closed breeding population since 19$8 and random bred s i n c e 19$9. I t i s c h a r a c t e r i s e d by good egg production, l i g h t body weight, a high degree of l i v a b i l i t y and l a r g e egg s i z e . The WR l i n e has been maintained at The Un i -v e r s i t y of B r i t i s h Columbia Genetics Unit as a random mating u n i t 11 since I 9 6 0 . I t i s a t y p i c a l b r o i l e r stock, being characterized by heavy body weight, a high degree of l i v a b i l i t y and large egg s i z e , but low egg production. The NH l i n e has been maintained at The University of B r i t i s h Columbia as a random mating unit f o r at l e a s t twelve years. I t combines medium body weight with f a i r l y good egg production. Experiment 1 The breeding pens for the production of the crosses, t h e i r reciprocals and the pure l i n e s used i n Experiment 1 were set up as follows. Eighty-four hens represented each of the NH and WL l i n e s whereas between seventy-two and seventy-five hens represented the WR l i n e . Hens of each l i n e were randomized into s i x breeding pens, and four males of each genotype were randomly assigned i n pairs to these s i x pens. By repeating t h i s d i s t r i b -ution f o r each l i n e , each of the nine possible "genotypic" mat-ings was duplicated. Ten days a f t e r the mating pens were es-tablished, a t h r i c e weekly ro t a t i o n of the males among the six pens which contained the same male s t r a i n , was commenced. I t was assumed that t h i s male rotation technique would minimize i n d i v i d u a l male ef f e c t s . Commencing at t h i s time and during the following three weeks, eggs were gathered twice d a i l y , dated, i d e n t i f i e d as to o r i g i n and placed d i r e c t l y into a room maintained at approximate-l y 55°F. The c o l l e c t i o n regime was i n s t i t u t e d to reduce embryo-nic development occurring p r i o r to storage of the eggs. Each 12 day's c o l l e c t i o n was removed from storage on the f o l l o w i n g morn-i n g and f i f t e e n eggs of each "genotype" were randomly s e l e c t e d . The number f i f t e e n was determined by the average production of the poorest producing pens. The s e l e c t e d eggs were then i n d i v -i d u a l l y weighed and recorded to the nearest gram before being returned t o storage. A f t e r three weeks of c o l l e c t i o n , a l l eggs were r e -weighed and trayed f o r i n c u b a t i o n . In t h i s manner, i n d i v i d u a l records of week of l a y , "genotype" and weight before and a f t e r storage were obtained f o r more than 2,700 eggs. Before t r a y i n g , the eggs of each "genotype" were randomly d i v i d e d i n t o two groups those t h a t were assigned f o r hatching and those that were assigne f o r embryo weighing during i n c u b a t i o n . The eggs t h a t were assigned f o r embryonic t e s t were f u r t h e r subdivided randomly i n t o seven subsets, w i t h the r e s t r i c t i o n that approximately seven eggs of each week of l a y were present i n each "genotypic" subset. One of the seven subsets would be broken out and the embryos weighed on each of the a l t e r n a t e days from 6 t o 18 days of i n c u b a t i o n , i n c l u s i v e . The corresponding subsets of each genotype were then brought together and randomly d i s t r i b u t e d i n t o incubator t r a y s . This meant th a t a l l eggs w i t h i n any one t r a y would be withdrawn f o r embryonic examination on the same day, thus minimizing heat l o s s during i n c u b a t i o n . The t r a y s were then randomly d i s t r i b u t e d i n t o two Jamesway Model 2940 i n c u b a t o r s . In order to minimize growth o c c u r r i n g between w i t h -13 drawal of the t r a y s and the a c t u a l weighing of the embryos the as s i g n e d t r a y s were withdrawn at f o r t y - e i g h t hour i n t e r v a l s and r e f r i g e r a t e d o v e r n i g h t . P r i o r t o weighing, each embryo was separated from i t s extra-embryonic membranes by c u t t i n g the u m b i l i c a l cord a t i t s ju n c t u r e with the abdomen. The e x c i s e d embryo was then p l a c e d on a pi e c e of absorbent paper f o r a few seconds i n order to d r a i n o f f excess moisture before weighing. I n f e r t i l e eggs and embryos which had d i e d p r i o r to removal from the i n c u b a t o r , as w e l l as o b v i o u s l y deformed embryos, were d i s c a r d e d . Embryo weights were taken to the nearest thousandth of a gram, and the sex was d e t e r -mined and r e c o r d e d s t a r t i n g on the t w e l f t h day of i n c u b a t i o n . Approximately 1 , 3 5 0 eggs were broken out over the seven weighing p e r i o d s . Those eggs t h a t were a s s i g n e d f o r h a t c h i n g were d i v i d e d at random w i t h i n each genotype i n t o two groups corre s p o n d i n g t o the two n u t r i t i o n a l environments on which t h e hatched c h i c k s would be r e a r e d . Eggs from each genotype, w i t h i n a treatment, were then randomized throughout the i n c u b a t o r s . The eggs assigned f o r h a t c h i n g were candled a t eighteen days and v i a b l e eggs were t r a n s f e r r e d i n t o h a t c h i n g t r a y s . Each t r a n s f e r r e d egg was placed under an i n v e r t e d polythene basket, and wire frames were p l a c e d over the baskets t o h o l d them down. In t h i s f a s h i o n , i n d i v i d u a l h a t c h i n g data could be obtained. The ha t c h i n g time of each c h i c k was recorded as o c c u r r i n g i n one of 14 t h r e e p e r i o d s ; p r i o r to the end of the t w e n t i e t h day, or w i t h i n one of the f o l l o w i n g two s u c c e s s i v e twelve-hour p e r i o d s ( i . e . e a r l y t w e n t y - f i r s t and l a t e t w e n t y - f i r s t day). The h a t c h i n g p e r i o d s were eva l u a t e d as 1, 2 and 3 r e s p e c t i v e l y . During the l a t e t w e n t y - f i r s t and e a r l y twenty-second day p e r i o d s the hatched c h i c k s were i n d i v i d u a l l y wing-banded and weighed to the n e a r e s t gram. D i s t r i b u t i o n of the c h i c k s i n t o the brooding pens was done l a t e on the twenty-second day, the c h i c k s f o r each treatment being randomized i n t o d u p l i c a t e pens so t h a t each of the f o u r pens contained a random sample of c h i c k s of each genotype. The nut-r i t i o n a l environments were provided by a commercial b r o i l e r r a t i o n and a commercial s t a r t e r r a t i o n from the same source. The hover-type brooders were e n c i r c l e d with a cardboard guard f o r the f i r s t t h r ee days to keep the c h i c k s c l o s e to the source of heat. A n t i -b i o t i c was added to the d r i n k i n g water f o r t h e f i r s t t h r e e days i n recommended amounts. I n d i v i d u a l body weights were reco r d e d week-l y to s i x weeks of age and the sex, determined by v i s u a l i n s p e c t i o n , was r e c o r d e d a t e i g h t weeks of age. The b i r d s were g i v e n an ocu-l a r v a c c i n e f o r Newcastle d i s e a s e and i n f e c t i o u s b r o n c h i t i s at f o u r t e e n days of age. A m i l d outbreak of c o c c i d i o s i s was noted d u r i n g the s i x t h week and t r e a t e d promptly w i t h a c o c c i d i o s t a t . Seven hundred and n i n e t y - t h r e e b i r d s were s u c c e s s f u l l y r a i s e d out of e i g h t hundred and s i x s t a r t e d , thus g i v i n g a t o t a l m o r t a l i t y :of l e s s than 2 per cent. Experiment 2 The procedures of Experiment 2 were s t a n d a r d i z e d t o those of Experiment 1, except f o r the f o l l o w i n g v a r i a t i o n s : 1) The number of dam genotypes and t h e r e f o r e the number of eggs c o l l e c t e d and incubated was doubled by the i n c l u s i o n of c r o s s b r e d p u l l e t s which were c a r r i e d over from the f i r s t t e s t . Each of the three groups of c r o s s b r e d dams was made up of equal numbers of the s i n g l e and i t s r e c i p r o c a l c r o s s . I t was assumed that no adverse e f f e c t on the measured t r a i t s would r e s u l t by combining the s i n g l e c r o s s and i t s r e c i p r o c a l t o use as a s i n g l e dam l i n e . E i g h t y - f o u r dams of each s t r a i n and s t r a i n c r o s s were a v a i l a b l e f o r breeding. 2 ) A f e r t i l i t y check p r i o r t o the commencement of the c o l l e c t i o n p e r i o d was made by i n c u b a t i n g f o r twenty-f o u r hours a sample of one day's c o l l e c t i o n of eggs from each breeding pen. The eggs were broken and the degree of f e r t i l i t y f o r each pen determined. T h i s check showed that a replacement of a p a i r o f males from each of the WL and WR l i n e s was needed. The sex of t h e embryos was recorded s t a r t i n g at the t e n t h day of i n c u b a t i o n , two days e a r l i e r than i n Experiment 1. The c h i c k s were randomized i n t o nine, f o u r - t i e r e d 3) 4) battery brooders with two compartments per l e v e l , with the r e s t r i c t i o n that one bird of each genotype would be placed i n each compartment i f s u f f i c i e n t represen-tati v e s were available. A separate battery brooder was used to rear excess chicks, and any b i r d that died i n the f i r s t two weeks was replaced by a bird of the same genotype and n u t r i t i o n a l environment. The two n u t r i t i o n a l environments were of the same type and from the same source as i n Experiment 1. Although the rations were intended to be i d e n t i c a l with those of Experiment 1, i t was noted that the chick s t a r t e r r a t i o n was of a much f i n e r texture. During the test, a number of birds on the starter r a t i o n developed a crossed beaked condition which was diagnosed as being due to impaction of the f i n e r textured feed. These crossed beaked chicks were recorded, with a subjec-t i v e d i f f e r e n t i a t i o n being made between a s l i g h t twist-ing of the beak and a serious deformity. It was assumed that the s l i g h t twisting of the beak would not a f f e c t the subsequent performance, but that a serious deformity would. Therefore, those birds with a mark-edly deformed beak were not included i n the analysis of the data. 17 STATISTICAL METHODS The body weights of i n d i v i d u a l chicks during the growth phase between hatch and s i x weeks of age were assumed to follow the power function, y - a t b , where 2 i s equal to the body weight of the i n d i v i d u a l at time t , a i s equal to the body weight of the in d i v i d u a l at time zero and b represents the growth rate of the i n d i v i d u a l . Weekly growth rate estimates were calculated between hatching and s i x weeks of age for each i n d i v i d u a l . The averaged weekly values provided a single estimate of growth rate from hatch to s i x weeks of age. As only one body weight observation could be made for any embryo, i t was impossible to calculate i n d i v i d u a l embryonic growth rate. .It was assumed, however, that the growth rates bet-ween two embryonic weighing periods could be estimated f o r any ex-perimental c e l l by using the average of the embryonic weights of those i n d i v i d u a l s within a genotype, sex (when recorded) and egg storage period. In the few instances (once i n Experiment 1 and twice i n Experiment 2 ) where no embryo weight was available within a p a r t i c u l a r subclass an estimate was calculated, based on the av-erage weight r a t i o s of other subclasses and the embryo weights immediately preceding and following the missing value. Embryonic growth rate estimates were calculated f o r each of the two-day periods between s i x and eighteen days of incubation. In addition, 18 the two-day estimates were averaged i n d i f f e r e n t combinations to provide values f o r the f o l l o w i n g embryo growth p e r i o d s ; 6-10, 6-12, 6-14, 6-16, 6-18, 8-12, 8-14, 8-16 and 8-18 days. The general model assumed to e x p l a i n the sources of v a r i a t i o n i n the embryonic body weights and growth r a t e s was: E i j k l + s i + d j 4 ( s d ) i j 4 p k + ( s p ) i k + (dp) J- k4 ( s d p ) i j k 4 f x + ( s f l ^ l ( d f ) j i 4 ( p f ) k l 4 ( s d f ) i j ] L 4 ( s p f ) i k l + ( d p f ) j k l 4- e i j k l The s i r e e f f e c t ; s ( i - 1 - n s ) , the dam e f f e c t ; d ( j = 1 - nd), the storage period e f f e c t ; p(k = 1 - np) and the sex e f f e c t ; f ( l = 1 - nf) were considered t o be f i x e d , whereas the r e s i d u a l term e was considered to be of a random nature. Table I shows the p a r t i c u l a r models used i n the analyses of embryo data. The models i n t h i s t a b l e w i l l be r e f e r r e d to c o n s i s t e n t l y i n the t e x t and t a b l e s throughout t h i s t h e s i s . In the analyses of variance of the post-hatch data, the average value w i t h i n genotype, treatment and r e p l i c a t i o n was used as the sample observation, and the two sexes were analyzed sep-a r a t e l y . Assuming t h a t i f d i f f e r e n c e s d i d e x i s t w i t h i n the bat-t e r i e s of Experiment 2 they would be more l i k e l y to occur between the top and bottom t i e r s , the top two t i e r s and the bottom two t i e r s were combined as r e p l i c a t i o n s 1 and 2 r e s p e c t i v e l y . The s t a t i s t i c a l model assumed to e x p l a i n the sources of variance of 19 the average body weight o b s e r v a t i o n s a t h a t c h i n g and at weekly i n t e r v a l s t h e r e a f t e r was: Y i j k l = Si + d j f ( s d ) i j + t k + ( s t ) i k + ( d t ) j k f ( s d t ) i J k + e i j k l Model ( i ) The s i r e e f f e c t ; s ( i - 1 - n s ) , the dam e f f e c t ; d ( j • 1 - n^) and the treatment e f f e c t ; t ( k = 1 - nt) were con-s i d e r e d t o be f i x e d e f f e c t s and e i j k ( l = 1 - 2 ) was considered t o be a random e f f e c t of r e p l i c a t i o n w i t h i n genotype and treatment. The model assumed t o d e s c r i b e each of the growth p e r i o d s was: b i j k l " y ^ 4 s i + d j + ( s d ) i j + t k + ( s t ) i k + (dt) j k +(sdt)ij k + e i j k i Model ( j ) which d i f f e r e d from model ( i ) only i n the phenotype analyzed. In a d d i t i o n , simple c o r r e l a t i o n s and the c o e f f i c i e n t s of d e t e r m i n a t i o n based on simple l i n e a r r e g r e s s i o n s and m u l t i p l e l i n e a r r e g r e s s i o n s were c a l c u l a t e d from i n d i v i d u a l c h i c k data as w e l l as from averaged data w i t h i n genotype and treatment. C a l c u l a t i o n s of the analyses of v a r i a n c e , r e g r e s s i o n s and c o r r e l a t i o n s were done on The U n i v e r s i t y of B r i t i s h Columbia I.B.M. 7040 computor, a c c o r d i n g t o the methods presented by R a l -ston and W i l f ( i 9 6 0 ) . Duncan's new m u l t i p l e range t e s t ( S t e e l e and T o r r i e , I960) was used t o t e s t d i f f e r e n c e s between means w i t h -i n the main e f f e c t s of the analyses of v a r i a n c e ( P £ . 0 5 ) . I t 20 should be noted here th a t Duncan's t e s t i s independent of the a n a l y s i s of variance and can demonstrate d i f f e r e n c e s between p a r t i c u l a r means, when the main e f f e c t (as shown by a n a l y s i s of variance) i s n o n - s i g n i f i c a n t . The words " s i g n i f i c a n t " and " h i g h l y s i g n i f i c a n t " were used to r e f e r to d i f f e r e n c e s among sample means which, on the b a s i s of s t a t i s t i c a l a n a l y s i s , are expected to r e f l e c t t r u e d i f -ferences among the population means w i t h a p r o b a b i l i t y of not more than .05 and .01 r e s p e c t i v e l y of being i n c o r r e c t . RESULTS AND DISCUSSION Table I I contains the F values and t h e i r s i g n i f i c a n c e l e v e l c a l c u l a t e d from the analyses of va r i a n c e of embryo weights at 12, 14, 16 and 18 days of i n c u b a t i o n f o r Experiments 1 and 2, us i n g s t a t i s t i c a l model ( a ) . I t can be seen t h a t only the main e f f e c t s ; sex, age, s i r e and dam, and the i n t e r a c t i o n between s i r e and dam were s i g n i f i c a n t at 5 or 1 per cent p r o b a b i l i t y l e v e l s w i t h any a p p r e c i a b l e consistency. For t h i s reason the other i n t e r a c t i o n s were in c l u d e d w i t h the r e s i d u a l variance i n a l l subsequent analyses of variance of embryonic data. Experiment 1 Embryo Weights The percentage of the t o t a l sums of squares a t t r i b u t e d to each of the p a r t i t i o n e d e f f e c t s , t h e i r s i g n i f i c a n c e and the 21 models used f o r the analyses of embryo weights at each of the weighing p e r i o d s are presented i n Table I I I . The e f f e c t of storage p e r i o d was h i g h l y s i g n i f i c a n t a t each of the embryo weighings. Duncan's t e s t i n d i c a t e d t h a t , a l -most without e x c e p t i o n , each week of storage r e s u l t e d i n a s i g n i f -i c a n t and cumulative d e p r e s s i o n o f mean embryo weight w i t h i n each i n c u b a t i o n p e r i o d (Table I V ) . Storage p e r i o d seemed t o ac-count f o r r e l a t i v e l y more of the v a r i a t i o n i n the e a r l i e r stages of i n c u b a t i o n than a t l a t e r s t a g e s , as evidenced by the d e c r e a s i n g percentage sums of squares i n Table I I I . The e f f e c t s of s i r e and dam l i n e s on embryo weight were l e s s c o n s i s t e n t and of s m a l l e r magnitude than the e f f e c t of egg storage, however, both s i r e and dam l i n e e f f e c t s were h i g h l y s i g -n i f i c a n t a t twelve and f o u r t e e n days of i n c u b a t i o n , and the s i r e l i n e e f f e c t a l s o showed s i g n i f i c a n c e a t t e n days of i n c u b a t i o n (Table I I I ) . The r e s u l t s i n Table V i n d i c a t e t h a t a t twelve and at f o u r t e e n days of i n c u b a t i o n , the mean weight of embryos from each s i r e l i n e was s i g n i f i c a n t l y d i f f e r e n t (Duncan's t e s t ) from those of the other two s i r e l i n e s , and t h a t the order of means from lowest t o h i g h e s t was WL, NH and WR. S i m i l a r r e s u l t s can be seen i n Tab l e VI f o r the dam l i n e e f f e c t s . A h i g h l y s i g n i f i c a n t i n t e r a c t i o n between the s i r e and dam l i n e s o ccurred on the t e n t h day of i n c u b a t i o n (Table I I I ) , however, as t h i s i n t e r a c t i o n d i d not approach s i g n i f i c a n c e a t any other time, i t was assumed due to sampling e r r o r . A s i g n i f i c a n t 22 sex difference was observed at fourteen days, but the proportion of t o t a l variance due to sex was reduced and non-significant at sixteen days and almost non-existent at eighteen days (Table I I I ) . Table VII indicates that, with the single exception of embryos at the twelfth day of incubation, the average weight of male embryos was greater than that of females. Embryo Growth Rates The per cent of the t o t a l sums of squares attributed to each of the partitioned effects from the analyses of variance of growth rates f o r two-day i n t e r v a l s between each embryo weigh-ing day are presented i n Table VIII. The e f f e c t of storage per-iod on embryonic growth rate was highly s i g n i f i c a n t during the 6-8 day i n t e r v a l , s i g n i f i c a n t f o r each of the periods $-10 and 10-12, highly s i g n i f i c a n t again during the 12-14 day i n t e r v a l and non-significant thereafter. Duncan's t e s t , when applied to the mean growth of embryos from the three storage periods (Table IX) indicated that, i n the growth periods 6-8, 10-12 and 12-14 days, a general pattern can be seen i n that embryos from eggs stored fo r three weeks p r i o r to hatching had a s i g n i f i c a n t l y greater growth rate than those from eggs stored for one week. However, only f o r the 6-8 day i n t e r v a l did two-week storage r e s u l t i n an embryo growth rate which was both intermediate to and s i g n i f i c a n t -l y d i f f e r e n t from the growth rates r e s u l t i n g from one and three-week storage. For the 8-10 day incubation i n t e r v a l a dispropor-t i o n a t e l y high embryo growth rate f o r the one-week storage group was evident. I f the growth rates during the d i f f e r e n t i n t e r v a l s 23 are compared i t can be seen that growth appeared t o be i n h i b i t e d during t h i s same period,(perhaps due to some f a u l t i n i n c u b a t i o n ) . I t may be tha t the higher growth r a t e of the embryos from the one-week storage group was due to a higher r e s i s t a n c e of t h i s group to the i n c u b a t i o n s t r e s s . Neither s i r e nor dam l i n e s had any s i g n i f i c a n t e f f e c t on growth r a t e during the i n t e r v a l s 6-8 and 8-10 days of incuba-t i o n (Table V I I I ) . Both e f f e c t s , however, were h i g h l y s i g n i f i -cant during the 10-12 day i n t e r v a l , at which time each of the mean growth r a t e s of the WR l i n e s i r e s and dams were s i g n i f i c a n t -l y s u p e r i o r to those of the s i r e s and dams of the NH or WL l i n e s r e s p e c t i v e l y (Tables X and X I ) . The e f f e c t of s i r e s or dams d i s -appeared dur i n g the 12-14 day i n t e r v a l but reappeared s i g n i f i c a n t -l y i n the case of s i r e s during the 14-16 day i n t e r v a l , however, at t h i s i n t e r v a l the WL s i r e l i n e was now su p e r i o r t o the WR l i n e , and the NH s i r e l i n e was intermediate to but not s i g n i f i c a n t l y d i f f e r e n t from e i t h e r . The s i r e x dam l i n e i n t e r a c t i o n e f f e c t on the two-day growth r a t e s was h i g h l y s i g n i f i c a n t d u r i n g the 8-10 and the 10-12 day periods. Both of these growth r a t e i n t e r v a l s , however, i n v o l v e the ten-day embryo and i t was considered that i f e x p e r i -mental e r r o r was the cause of the s i g n i f i c a n t s i r e x dam i n t e r -a c t i o n of embryo body weights, then t h i s same e r r o r would be r e f l e c t e d i n the 8-10 and 10-12 day growth r a t e s . S i m i l a r l y , the s i g n i f i c a n t e f f e c t of sex on growth ra t e during the 12-14' 24 day i n t e r v a l corresponded to the sex e f f e c t on fourteen-day embryo weight. The two-day growth r a t e estimates f o r the d i f f e r e n t i n t e r v a l s of i n c u b a t i o n were averaged to provide estimates f o r the periods beginning at 6 and ending at 10, 12, 14, 16 and 18 days, as w e l l as those beginning at S and ending at 12, 14, 16 and 18 days of i n c u b a t i o n . The r e s u l t s of the analyses of var-iance of these averaged growth r a t e estimates are presented i n Table X I I . The e f f e c t of egg storage on these average growth r a t e s was g e n e r a l l y h i g h l y s i g n i f i c a n t , and only the average estimates f o r the pe r i o d 8-12 days were not s i g n i f i c a n t l y d i f f e r e n t . I t can be seen from Table IX th a t the values of growth r a t e s f o r the d i f f e r e n t storage periods during the 10-12 day i n t e r v a l were i n -v e r s e l y r e l a t e d t o the depressed values of the 8-10 day i n t e r v a l . I t would seem reasonable, t h e r e f o r e , to suggest t h a t a compensa-t o r y e f f e c t on growth during the i n t e r v a l f o l l o w i n g the depression was enough to mask any e f f e c t of egg storage on the average growth r a t e during the 8-12 day i n t e r v a l . The r e s u l t s i n Table X I I I i n d i c a t e t h a t the average growth r a t e s of embryos from eggs held f o r three weeks p r i o r to i n c u b a t i o n were s i g n i f i c a n t l y higher than the average growth r a t e s of embryos from eggs h e l d f o r only one week, f o r a l l growth periods c a l c u l a t e d except the 8-12 day p e r i o d mentioned above. In a d d i t i o n , i t can be seen that during the growth periods begin-25 ning at 6 days and ending at 12, 14, 16 and IB days of incuba-t i o n , the average growth r a t e s of embryos from eggs held f o r two weeks p r i o r to i n c u b a t i o n were intermediate to and s i g n i f i c a n t l y d i f f e r e n t from the average growth r a t e s of embryos from eggs held f o r one or three weeks. These f i n d i n g s are con t r a r y to those of Kaufman (as c i t e d by Bohren et a l . , 1961), who reported t h a t , though i n i t i a t i o n of embryo growth was delayed by pre- i n c u b a t i o n storage of eggs, subsequent embryo growth was unaffected. As mentioned p r e v i o u s l y , storage periods appeared to account f o r r e l a t i v e l y more v a r i a t i o n i n embryo weight during e a r l y stages of i n c u b a t i o n than during l a t e r stages. The compensatory growth of embryos from the eggs which were held f o r longer periods provides a reasonable explanation f o r reduced r e l a t i v e d i f f e r e n c e s due to storage e f f e c t s on embryo weights observed during l a t e r stages of i n c u b a t i on. S i r e and dam l i n e e f f e c t s on average growth r a t e s were s i g n i f i c a n t d u r i n g some periods and n o n - s i g n i f i c a n t d u r i n g others (Table X I I ) . Duncan's t e s t (Tables XIV and XV), however, i n -d i c a t e d t h a t there was a high degree of i n c o n s i s t e n c y when the means of the v a r i o u s s i r e or dam l i n e s were compared and no mean-i n g f u l i n t e r p r e t a t i o n was. .apparent. Post-hatching Body Weights (Males) The percentage of the t o t a l v a r i a t i o n a t t r i b u t a b l e to the p a r t i t i o n e d e f f e c t s , t h e i r s i g n i f i c a n c e and the models used i n the analyses of variance of post-hatching body weights of the 26 male progeny are presented i n Table XVI. The e f f e c t of s i r e s was s i g n i f i c a n t at one week of age and h i g h l y s i g n i f i c a n t a t each week from two to s i x weeks of age. Table XVII i n d i c a t e s t h a t the mean weights o f c h i c k s from the t h r e e s i r e l i n e s were s i g n i f -i c a n t l y d i f f e r e n t from each other from the t h i r d week onwards, and t h a t the order from lowest t o h i g h e s t was WL, RH and WR. The e f f e c t of the dam l i n e s was h i g h l y s i g n i f i c a n t a t a l l weighings (Table XVI), i n c l u d i n g the hatch weight where the e f f e c t was e v i d e n t l y due to the maternal i n f l u e n c e s of the d i f -f e r e n c e s i n egg weights from the t h r e e dam l i n e s (Table X V I I I ) . The data of Table XIX i n d i c a t e s t h a t the mean weights of c h i c k s from the three dam l i n e s were not s i g n i f i c a n t l y d i f f e r e n t from each other u n t i l the t h i r d week. The order of magnitude was the same as f o r c h i c k s from the t h r e e s i r e l i n e s . The r a t i o n e f f e c t (Table XVI) was h i g h l y s i g n i f i c a n t a t the second week's weighing, n o n - s i g n i f i c a n t at the t h i r d week and h i g h l y s i g n i f i c a n t from the f o u r t h week on. I t i s i n t e r e s t i n g to note t h a t the s i g n i f i c a n t t h i r t e e n gram d i f f e r e n t i a l t h a t e x i s t e d i n f a vour of the b r o i l e r r a t i o n a t two weeks was reduced to a non-s i g n i f i c a n t d i f f e r e n c e of f o u r grams a t t h r e e weeks before i n -c r e a s i n g a g a i n d u r i n g l a t e r weighings (Table XX). As the c h i c k -ens were v a c c i n a t e d a t two weeks i t seems reasonable to suppose t h a t the l o s s of s i g n i f i c a n c e of treatment e f f e c t s was due to a d i f f e r e n t i a l response to the v a c c i n a t i o n . An i n h i b i t i o n o f growth r a t e by o c u l a r v a c c i n a t i o n take was noted by Roberts (I965). 27 The s i r e x dam and the dam x r a t i o n i n t e r a c t i o n s a t -t a i n e d s i g n i f i c a n c e at d i f f e r e n t weighing periods. The s i r e x dam i n t e r a c t i o n may be r e a l , but the random allotment of eggs to r a t i o n s p r i o r t o i n c u b a t i o n a t t e s t s to the spurious nature of the dam x r a t i o n i n t e r a c t i o n of hatching weights. Post-hatching Growth Rates (Males) The e f f e c t of s i r e l i n e s on post-hatching growth r a t e of the male ch i c k s was h i g h l y s i g n i f i c a n t f o r a l l weekly periods between hatching and f i v e weeks of age and remained s i g n i f i c a n t f o r the p e r i o d between f i v e and s i x weeks of age (Table XXI). During the hatch to one week i n t e r v a l the growth r a t e of the WL s i r e l i n e males was s i g n i f i c a n t l y s u p e r i o r to that of the NH s i r e l i n e males and not s i g n i f i c a n t l y d i f f e r e n t from t h a t of the WR l i n e (Table X X I I ) . Duncan's t e s t i n d i c a t e d t h a t growth r a t e of male c h i c k s from the WL s i r e l i n e was s i g n i f i c a n t l y lower than t h a t of the NH or WR s i r e l i n e males during each weekly i n t e r v a l from one to f i v e weeks of age. The NH and WR s i r e l i n e male growth r a t e s were not s i g n i f i c a n t l y d i f f e r e n t except during the hatch to one week i n t e r v a l when the WR l i n e was s u p e r i o r . The six-week growth r a t e of male c h i c k s from these two s i r e l i n e s d i f -f e r e d by only 0.01 (not s i g n i f i c a n t ) . I t would seem, t h e r e f o r e , that the t h i r t y - t w o gram d i f f e r e n c e i n six-week body weight i n favour of the WR l i n e (Table XVII) was mainly due to the s i g n i f i -cant d i f f e r e n c e i n growth during the f i r s t week a f t e r hatching. However, the r a t e of growth during t h i s i n t e r v a l i s not always 28 i n d i c a t i v e of f i n a l body weight or growth r a t e i n subsequent p e r i o d s . I t can be seen from Tables X X I I and X V I I tha t i n s p i t e of the f a c t tha t c h i c k s from the NH male l i n e had a f i r s t week growth r a t e t ha t was s i g n i f i c a n t l y lower than tha t o f male c h i c k s of the WL l i n e , t h i s former group achieved a s i g n i f i c a n t l y h igher s ix-week body weight and six-week growth r a t e . However, t h i s may be a n a t u r a l c o n d i t i o n e x i s t i n g between l i g h t and heavy breeds of c h i c k e n . Table XXI i n d i c a t e s t ha t the e f f e c t of dam l i n e on week-l y growth r a t e of male c h i c k s was h i g h l y s i g n i f i c a n t dur ing the f i r s t week of p o s t - h a t c h i n g growth, and s i g n i f i c a n t from then un-t i l the end of the f o u r t h week. The e f f e c t of dam l i n e on s ix-week growth r a t e was h i g h l y s i g n i f i c a n t . The r e s u l t s of Duncan's t e s t on the mean growth r a t e s o f male c h i c k s from the three dam l i n e s (Table X X I I I ) i n d i c a t e t h a t the d i f f e r e n c e s between them compare ve ry c l o s e l y w i t h those observed f o r the s i r e l i n e s (Table X X I I ) . Apparen t ly the on ly gene t i c d i f f e r e n c e i n weekly growth r a t e s between the NH and WR l i n e s occurred du r ing the f i r s t week 's growth p e r i o d , s i n c e f o r both s i r e and dam l i n e s no s i g n i f -i c a n t d i f f e r e n c e was found i n subsequent growth p e r i o d s . In con-t r a s t to the male l i n e s there was a s i g n i f i c a n t d i f f e r e n c e be t -ween the s ix-week growth r a t e s of a l l three dam l i n e s , t h e i r r e l -a t i v e o rder ; WL, NH and WR being the same as was observed f o r t h e i r s ix-week body w e i g h t s . The r a t i o n e f f e c t on weekly growth r a t e s (Table XXI) 29 was h i g h l y s i g n i f i c a n t d u r i n g the second, t h i r d and f o u r t h weeks of post-hatching growth, s i g n i f i c a n t during the f i f t h and non-s i g n i f i c a n t during the f i r s t and s i x t h weeks. The e f f e c t on six-week growth r a t e was h i g h l y s i g n i f i c a n t . Comparisons of the r a t i o n means (Table XXIV) i n d i c a t e d t h a t f o r each weekly i n t e r v a l between one and f i v e weeks of age, with the exception of the two to three week i n t e r v a l , the b r o i l e r r a t i o n was s u p e r i o r t o the s t a r t e r . The s i g n i f i c a n t l y g r eater growth r a t e achieved on the s t a r t e r r a t i o n during the two t o three week per i o d was due to a d i f f e r e n t i a l response to the e f f e c t of v a c c i n a t i o n at the begin-ning of t h i s p e r i o d . I t i s i n t e r e s t i n g t o note that the s i r e x dam i n t e r a c -t i o n s which showed some s i g n i f i c a n c e when body weights were an-alyzed were not s i g n i f i c a n t . w h e n the same data was placed i n a d i f f e r e n t frame of ref e r e n c e . P o s s i b l y many genetic i n f e r e n c e s which i n the past have been based on the appearances of a s i r e x dam i n t e r a c t i o n i n body weight data would be changed, s i n c e the i n t e r a c t i o n appears to a r i s e from the n o n - a d d i t i v i t y a s s o c i a t e d w i t h body weight. Post-hatching Body Weights (Females) The percentage suras of squares a t t r i b u t a b l e to the par-t i t i o n e d e f f e c t s obtained i n the analyses of variance of post-hatching female chick weights are presented i n Table XXV. I t can be seen t h a t there was a h i g h l y s i g n i f i c a n t e f f e c t of dam l i n e s on hatching weight and that the e f f e c t s of both dam l i n e s 30 and s i r e l i n e s on body weights were h i g h l y s i g n i f i c a n t t h e r e a f t e r Tables XXVI and XXVII i n d i c a t e that f o r both of these main e f f e c t the mean weights of chi c k s from each l i n e were s i g n i f i c a n t l y d i f -f e r e n t a f t e r two weeks'growth and increased i n the order WL, NH and WR:,: as d i d the male progeny. The e f f e c t of r a t i o n on the weekly weights of female c h i c k s was very s i m i l a r to the e f f e c t observed on the males. Again the e f f e c t disappeared at the t h i r d week's weighing and r e -appeared with a high s i g n i f i c a n c e during the subsequent weighings As i n the case of the male c h i c k s , the mean weight of females fed the b r o i l e r r a t i o n was s i g n i f i c a n t l y g r e ater than t h a t of the f e -male c h i c k s fed the s t a r t e r r a t i o n at a l l weighings except those at hatch and at three weeks of age (Table X X V I I I ) . The s i r e x dam i n t e r a c t i o n accounted f o r a f a i r l y high (8.52'/o) but n o n - s i g n i f i c a n t p r o p o r t i o n of the variance of female body weights at hatching (Table XXV). At a l l subsequent weigh-ings t h i s e f f e c t was h i g h l y s i g n i f i c a n t and warrants f u r t h e r con-s i d e r a t i o n . Table XXIX contains the mean body weights of female ch i c k s from each combination of s i r e and dam l i n e s at each of the weighing periods. I t can be seen t h a t w i t h i n both the WL and WR s i r e l i n e s , the mean weights of female chicks from the NH dam l i n were g e n e r a l l y intermediate t o those of the WL and WR dam l i n e s . W i t h i n the NH s i r e l i n e , however, there appears to be very l i t t l e d i f f e r e n c e between the WL and NH dam l i n e s , i n f a c t , u n t i l the s i x t h week the mean weight of c h i c k s from the NH dam l i n e was 31 s l i g h t l y l e s s than t h a t from the WL dam l i n e . G e n e t i c a l l y these data i n d i c a t e a r e l a t i v e l y constant non-additive e f f e c t , however, c a u t i o n should be placed on t h i s i n -t e r p r e t a t i o n since the n o n - a d d i t i v i t y of body weight per se was e s t a b l i s h e d i n the male data. Post-hatching Growth Rates (Females) The e f f e c t of s i r e l i n e s on weekly and six-week growth r a t e s was g e n e r a l l y h i g h l y s i g n i f i c a n t (Table XXX) and l o s t a l l s i g -n i f i c a n c e only d u r i n g the s i x t h weekly p e r i o d . The l o s s of s i g -n i f i c a n c e during the s i x t h week may have been due to the outbreak of c o c c i d i o s i s at t h i s time. Table XXXI i n d i c a t e s that the s i x -week growth r a t e of the WR s i r e l i n e was s i g n i f i c a n t l y greater than t h a t of the NH s i r e l i n e during the f i r s t week only, however, the average growth r a t e s of the three s i r e l i n e s were s i g n i f i c a n t l y d i f f e r e n t from each other and i n the ascending order WL, NH, WR. The dam e f f e c t on growth r a t e of female c h i c k s was very s i m i l a r to the s i r e e f f e c t (Table XXX), except t h a t there was a h i g h l y s i g n i f i c a n t d i f f e r e n c e during the second week and no s i g n i f -i c a n t d i f f e r e n c e during the t h i r d week. Table XXXII i n d i c a t e s that the only s i g n i f i c a n t d i f f e r e n c e between weekly growth r a t e s of female c h i c k s from the NH and WR dam l i n e s occurred d u r i n g the f i r s t week of post-hatching growth, however, the average growth r a t e s of the three dam l i n e s were s i g n i f i c a n t l y d i f f e r e n t from each other and i n the same order as observed 'for the s i r e l i n e s . Apparently the f i r s t week's growth of both males and females i s the d e c i d i n g f a c t o r i n the six-week body weight d i f f e r e n c e s of these heavy l i n e s . The r a t i o n e f f e c t on weekly and average growth ra t e s of female ch i c k s (Table XXX) was e s s e n t i a l l y i d e n t i c a l t o the e f f e c t of r a t i o n on male chick growth r a t e s . Again the growth r a t e of the chicks fed the b r o i l e r r a t i o n was more s e r i o u s l y a f -f e c t e d by v a c c i n a t i o n than that of chicks f e d on the s t a r t e r r a t i o n (Table X X X I I I ) . Embryo C o r r e l a t i o n s The simple c o r r e l a t i o n s of pre- and post-storage egg weights, embryo weights and date of l a y at each i n c u b a t i o n period are presented i n Table XXXIV. The c o r r e l a t i o n s between pre-storage egg weights and embryo weights showed no s i g n i f i c a n c e u n t i l the fourteenth day of i n c u b a t i o n , at which time the coef-f i c i e n t was p o s i t i v e and h i g h l y s i g n i f i c a n t and continued t o i n -crease dur i n g the s i x t e e n t h and eighteenth days of i n c u b a t i o n . The c o r r e l a t i o n c o e f f i c i e n t s between post-storage egg weight and embryo weight were a l s o h i g h l y s i g n i f i c a n t and p o s i t i v e and i n -creased from the fourteenth to the eighteenth day. However, at the e a r l i e r stages of i n c u b a t i o n the c o e f f i c i e n t s appeared t o be c o n t r a d i c t o r y . The r e l a t i o n s h i p between embryo weight and date of l a y was h i g h l y s i g n i f i c a n t at a l l stages of i n c u b a t i o n record-ed i n t h i s experiment (and may p a r t l y e x p l a i n t h i s c o n t r a d i c t i o n ) . Thus the s i g n i f i c a n t c o r r e l a t i o n between date of l a y and post-storage egg weight i n conjunction w i t h the high c o r r e l a t i o n bet-ween embryo weight and date of l a y , e v i d e n t l y c o n t r i b u t e d to the 33 high c o r r e l a t i o n and embryo weight and post-storage egg weight ob-served at the tenth day of i n c u b a t i o n . The h i g h l y s i g n i f i c a n t c o r r e l a t i o n between embryo weight and post-storage egg weight at s i x days of in c u b a t i o n appeared to be c o n t r a d i c t o r y to the general trend and may be spurious. Post-hatching C o r r e l a t i o n s Table XXXV presents the simple c o r r e l a t i o n s of time of hatch, storage period and pre- and post-storage egg weights with weekly c h i c k body weights from hatch to s i x weeks of age as c a l -c u l a t e d from the i n d i v i d u a l data of Experiment 1. The c o r r e l a -t i o n between time of hatch and chick body weight was h i g h l y s i g n i f i c a n t at a l l weighings. With hatching weight the c o e f f i c -i e n t was p o s i t i v e , however, from one week on i t became negative, reaching a minimum of -.290 at two weeks and i n c r e a s i n g very slow-l y t h e r e a f t e r . The p o s i t i v e c o r r e l a t i o n of time of hatch and hatching weight was presumably due to dehydration of e a r l i e r hatch-ed chicks p r i o r t o weighing. The negative r e l a t i o n s h i p at sub-sequent weighings i n d i c a t e s that the l a t e r hatching c h i c k s were smaller except when f i r s t hatched. The c o r r e l a t i o n s between storage period and chick weights were h i g h l y s i g n i f i c a n t w i t h the s i n g l e exception of the c o e f f i c i e n t between hatch weight and storage period. Again i t i s probable that drying out of e a r l i e r hatched c h i c k s obscured any r e l a t i o n s h i p between the recorded t r a i t s at hatching, f o r the c o r r e l a t i o n between storage period and hatching time ( r - .452) 34 was h i g h l y s i g n i f i c a n t and i n d i c a t e d t h a t the eggs which were stored f o r l e s s time p r i o r to i n c u b a t i o n tended to hatch e a r l i e r . These data are s u b s t a n t i a l l y i n agreement w i t h the r e p o r t of Bohren et a l . (1961) who showed that storage p e r i o d and hatching time were l i n e a r l y r e l a t e d . The negative c o e f f i c i e n t s between storage p e r i o d and subsequent chick body weights may be p a r t i a l l y due to the h i g h l y s i g n i f i c a n t c o r r e l a t i o n s of storage p e r i o d w i t h pre- and post-storage egg weights ( r - - .114 and r = -.211 r e s -p e c t i v e l y ) , although M e r r i t (1963) has reported that storage of hatching eggs f o r longer than two weeks decreases subsequent body weight. Both the pre- and post-storage egg weights were h i g h l y c o r r e l a t e d (P< . 0 1 ) with weekly body weights from hatch to s i x weeks of age, the c o e f f i c i e n t s being extremely high at hatching (.855 and .847) and d e c l i n i n g s t e a d i l y t h e r e a f t e r . Most of the more recent work i n the l i t e r a t u r e (Wiley, 1950b, O'Neil, 1950, Skoglund et a l . , 195'2 and T i n d e l and M o r r i s , 1964) agree that egg weight exerts an i n f l u e n c e on body weight at b r o i l e r age, although some (Godfrey et a l . , 1953 and Godfrey and W i l l i a m s , 1955) de-emphasize the importance of t h i s e f f e c t . Table XXXVI contains the c o r r e l a t i o n c o e f f i c i e n t s of hatching time, storage p e r i o d , pre- and post-storage egg weights and six-week body weight w i t h the i n d i v i d u a l weekly growth r a t e s . The c o r r e l a t i o n s between time of hatch and the weekly growth r a t e s were negative f o r a l l periods except the l a s t , and were 35 h i g h l y s i g n i f i c a n t during the f i r s t and second p e r i o d . These data i n d i c a t e d t h a t those chicks which hatched f i r s t tended t o have higher growth r a t e s . The c o r r e l a t i o n between storage period and weekly growth r a t e s i n d i c a t e d that those chicks from eggs which were layed l a t e r i n the c o l l e c t i o n and storage period tended to have higher growth r a t e s d u r i n g the e a r l y post-hatching p e r i o d , but lower growth r a t e s d u r i n g the l a t e r stages. Pre- and post-storage egg weights were n e g a t i v e l y cor-r e l a t e d with weekly growth r a t e s i n d i c a t i n g that the c h i c k s from l a r g e r eggs tended to have lower growth r a t e s . The c o e f f i c i e n t s were h i g h l y s i g n i f i c a n t during the second and t h i r d weeks' growth and g e n e r a l l y s i g n i f i c a n t during the remaining periods. Kosin et a l . ( 1 9 5 2 ) , u s i n g body weight gain as a measure of i n t r i n s i c growth, concluded that chicks from l a r g e r eggs had the greater growth. I f the present i n v e s t i g a t i o n had used the same frame of reference to measure growth, the c o n c l u s i o n would not have been d i f f e r e n t . The c o r r e l a t i o n c o e f f i c i e n t s between six-week body weight and weekly growth r a t e were p o s i t i v e and h i g h l y s i g n i f i c a n t from hatch to s i x weeks. I t i s i n t e r e s t i n g t o note that the high est c o e f f i c i e n t was obtained during the second week's growth at the same time as the most negative value occurred f o r the c o r r e l a -t i o n s between egg weights and weekly growth r a t e s . The i m p l i c a -t i o n s of t h i s are t h a t i t may be p o s s i b l e t o improve s i x week 36 body weight by s e l e c t i n g f o r e a r l y growth r a t e , without i n c r e a s -ing egg s i z e . Further work i s needed to determine i f s i m i l a r r e s u l t s can be obtained w i t h other s t r a i n s and s t r a i n crosses. C o r r e l a t i o n s of Embryo and Post-hatching Data Within "Genotypes" Embryo weights and growth r a t e s were averaged w i t h i n each s t r a i n and s t r a i n cross to o b t a i n "genotypic" estimates f o r these t r a i t s . In a d d i t i o n , "genotypic" estimates were obtained f o r post-hatching body weights and growth r a t e s and these data were a l s o separated as to sex and r a t i o n . W i t h i n sex and r a t i o n the six-week body weights were c o r r e l a t e d with each of the other corresponding "genotypic" estimates. The c o r r e l a t i o n c o e f f i c -i e n t s thus obtained are presented i n Table XXXVII. The six-week growth rate and weekly body weights from the end of the second week on bore a h i g h l y s i g n i f i c a n t r e l a t i o n -s h i p w i t h six-week body weight!. Weekly growth r a t e s , w i t h the exception of the s i x t h week's growth, were g e n e r a l l y s i g n i f i c a n t -l y r e l a t e d and w i t h i n each sex and r a t i o n the highest s i g n i f i c -ance occurred during the second week's growth. The six-week body weights of females r e c e i v i n g e i t h e r r a t i o n and of males r e c e i v i n g the s t a r t e r r a t i o n were s i g n i f i -c a n t l y c o r r e l a t e d w i t h twelve-day embryo weight and h i g h l y s i g -n i f i c a n t l y c o r r e l a t e d with fourteen-day embryo weight. The s i x -week body weight of males on the b r o i l e r r a t i o n was s i g n i f i c a n t l y c o r r e l a t e d with embryo weights only on the fourteenth day of i n -cubation. 3 7 None of the embryo growth r a t e s was s i g n i f i c a n t l y cor-r e l a t e d w i t h six-week body weight (Table XXXVII) or six-week growth r a t e (Table XXXVIII), however, t h i s may be due to too few degrees of freedom ( 7 ) and the d i f f i c u l t y of o b t a i n i n g accurate growth r a t e estimates d u r i n g the embryonic stage of growth. Although t he c o r r e l a t i o n s between six-week body weight and embryo growth r a t e s were i n s i g n i f i c a n t i t should be noted t h a t the highest c o r r e l a t i o n s were obtained during the i n t e r v a l s 6-14 and 8-12 days of i n c u b a t i o n ; the same i n t e r v a l s d u r i n g which the s i r e and dam e f f e c t s together were of the highest magnitude i n the analyses of variance (Table X I I ) . Experiment 2 Embryo Weights The percentage sums of squares a t t r i b u t a b l e t o the par-t i t i o n e d e f f e c t s , t h e i r s i g n i f i c a n c e and the models used f o r the analyses of variance of embryo weights at each of the weighing periods are presented i n Table XXXIX. With respect to the e f f e c t s of egg storage on embryo weights, the r e s u l t s of Experiment 2 were s i m i l a r to those of Experiment 1. The e f f e c t of storage was h i g h l y s i g n i f i c a n t at each o f the embryo weighings (Table XXXIX) and Duncan's t e s t on the mean weights of embryos from eggs stored f o r one, two or three weeks showed that at each weighing period each week of storage r e s u l t e d i n a s i g n i f i c a n t and cumulative depression of embryo 38 weight (Table X L ) . As i n Experiment 1, the percentage sums of squares i n d i c a t e d that storage period appeared to account f o r a l a r g e r p r o p o r t i o n of the v a r i a t i o n i n the e a r l y stages of incuba-t i o n than i n the l a t e r stages. The e f f e c t of s i r e l i n e on embryo weight was s i g n i f i c a n t at e i g h t and twelve days of i n c u b a t i o n and h i g h l y s i g n i f i c a n t at ten and at eighteen days. Table X L I i n d i c a t e s t h a t a t t e n , twelve and at eighteen days of i n c u b a t i o n , the mean weights of embryos from the NH and WR s i r e s was s i g n i f i c a n t l y greater than the mean weight of embryos from the WL s i r e s , but not s i g n i f i c a n t -l y d i f f e r e n t from each other. At ei g h t and again at twelve days of i n c u b a t i o n the mean weight of embryos from the NH s i r e l i n e was s i g n i f i c a n t l y greater than those of the WL or WR s i r e l i n e s . The dam e f f e c t s were g e n e r a l l y h i g h l y s i g n i f i c a n t from the ei g h t h day through to the fourteenth, however, a t twelve days t h i s e f f e c t was only s i g n i f i c a n t at the .0$ p r o b a b i l i t y l e v e l (Table X X X I X ) . At e i g h t , ten and f o u r t e e n days of i n c u b a t i o n the mean weight of embryos from the WL dam l i n e was s i g n i f i c a n t l y smaller than that of embryos from any other dam l i n e i n c l u d i n g the crossbreds (Table X L I I ) . The means of the other dam l i n e s appear to have no constant r e l a t i o n s h i p t o each other, except t h a t the embryos from the NH l i n e were g e n e r a l l y smaller than, but not s i g n i f i c a n t l y d i f f e r e n t from embryos from the WR dam l i n e . The general l a c k of s i g n i f i c a n t d i f f e r e n c e s between the mean weights of embryos from the d i f f e r e n t dam l i n e s as compared to Experiment 39 1, c o u l d be due t o t h e l a c k o f g e n e t i c d i v e r s i t y o f t h e c r o s s b r e d dams. The s i r e x dam i n t e r a c t i o n was s i g n i f i c a n t a t e i g h t , t e n and t w e l v e d a y s and h i g h l y s i g n i f i c a n t a t e i g h t e e n d a y s o f i n c u b a t i o n . A c o m p l e t e i n t e r p r e t a t i o n o f t h e s e r e s u l t s w o u l d r e q u i r e more p r e c i s i o n i n e s t i m a t i n g t h e " g e n o t y p i c " means t h a n t h i s e x p e r i m e n t p r o v i d e s , h o w e v e r , t h e p r e s e n c e o f t h e s i r e x dam i n t e r a c t i o n i n d i c a t e s t h a t n o n - a d d i t i v i t y i s f o u n d d u r i n g e m b r y o n i c d e v e l o p m e n t . S i g n i f i c a n t e f f e c t s o f g e n o t y p e on embryo w e i g h t i n b o t h e x p e r i m e n t s w e re r e s t r i c t e d m a i n l y t o t h e p e r i o d b e t w e e n e i g h t and f o u r t e e n d a y s o f i n c u b a t i o n . T h e r e seems t o be a g e n e r a l a g r e e -ment i n t h e l i t e r a t u r e t h a t g e n e t i c d i f f e r e n c e s i n embryo w e i g h t s do e x i s t , a l t h o u g h t h e r e i s some v a r i a t i o n i n t h e i n c u b a t i o n i n -t e r v a l d u r i n g w h i c h t h e y w e r e f o u n d t o be s i g n i f i c a n t . M o s t i n v e s t i g a t o r s h a v e o b s e r v e d s i g n i f i c a n t e f f e c t s o f b r e e d o r s t r a i n d u r i n g i n t e r v a l s w h i c h commence l a t e r and l a s t l o n g e r t h a n t h o s e m e n t i o n e d a b o v e ( B r a y a n d I t o n , 1962, B y e r l y e t a l . , 1938 and C o l e m a n e t a l . , 1964) . N e g a t i v e e v i d e n c e s u c h a s H e n d e r s o n (1930) may be due t o t o o s m a l l s a m p l e s i z e o r f a i l u r e t o t a k e a c -c o u n t o f t h e v a r i a t i o n due t o h o l d i n g o f e g g s p r i o r t o i n c u b a t i o n . The e f f e c t o f s e x on embryo w e i g h t s was h i g h l y s i g n i f i -c a n t a t t e n d a y s , and s i g n i f i c a n t a t t w e l v e ( T a b l e X X X I X ) . T a b l e X L I I I , h o w e v e r , i n d i c a t e s t h a t a t t h e o t h e r p e r i o d s a l s o , t h e mean w e i g h t o f t h e m a l e s was g r e a t e r t h a n t h e mean w e i g h t o f t h e 40 females. Combining the r e s u l t s of Experiment 1 (Table VII) and Experiment 2, the mean weight of male embryos was observed to be greater than that of female embryos on eight out of nine occa-sions. The binomial p r o b a b i l i t y of th i s happening by chance i s less than 0.01 which indicates that for the t o t a l of observations a highly s i g n i f i c a n t difference existed between the sexes. Embryo Growth Rates The percentage sums of squares from the analyses of variance of growth rates f o r the two-day i n t e r v a l s between each embryo weighing day are presented i n Table XLIV. The effe c t of storage was highly s i g n i f i c a n t during the 6-8 day period and dur-ing the 14-16 day period, but was non-significant during a l l other two-day i n t e r v a l s . Comparison of the mean growth rate of embryos from eggs stored for one, two or three weeks (Table XLV) in d i c a -ted that during the 6-8 day i n t e r v a l , each week of storage re-sulted -'• i n a s i g n i f i c a n t increase of the mean growth rate. A l -though the mean 14-16 day growth rate of embryos increased with each week of storage, no s i g n i f i c a n t differences were observed between one and two week storage. The s i r e effect on two-day growth rate was highly s i g -n i f i c a n t during the 8-10 day period, s l i g h t l y e a r l i e r than i n Experiment 1. Table XLVI indicates that the means could be ranked i n the ascending order WL, NH and WR during t h i s i n t e r v a l , although only the WR mean was s i g n i f i c a n t l y d i f f e r e n t from the other two. 41 The dam e f f e c t , s i g n i f i c a n t during the 14-16 day i n t e r -v a l , occurred somewhat l a t e r than i n Experiment 1. When the mean growth r a t e s of the dam l i n e s were compared (Table XLVTI), i t could be seen that d u r i n g t h i s p e r i o d the mean of the WR l i n e was s i g n i f i c a n t l y l e s s than t h a t of the WL l i n e and the mean of the NH l i n e was intermediate to but not s i g n i f i c a n t l y d i f f e r e n t from e i t h e r . I t w i l l be remembered that t h i s same order and s i g n i f -icance was observed f o r the s i r e l i n e embryos during the 14-16 day i n t e r v a l of Experiment 1. I t seems reasonable t o suggest t h a t during the l a t e r stages of i n c u b a t i o n , l a r g e r embryos may be more subject to growth r e s t r i c t i o n by l i m i t of s h e l l s i z e or by exhaustion of n u t r i e n t s , and thus the ra n k i n g of s i r e l i n e s or dam l i n e s on the basis of e a r l y embryonic growth r a t e or embryo s i z e could be reversed when ranking was based on l a t e embryonic growth r a t e . In general, the same observation can be made when the means of embryos from the NHxWR l i n e are compared with those of the other two crossbred dam l i n e s . As i n Experiment 1, the two-day estimates of growth r a t e were averaged to provide estimates f o r the periods beginning at 6 and ending at 10, 12, 14, 16 and 18 and beginning at 8 and ending at 12, 14, 16 and 18 days of i n c u b a t i o n . Table XLVTII contains the percentage sums of squares from the analyses of var-iance of these averaged growth r a t e estimates. The e f f e c t of pr e - i n c u b a t i o n egg storage on the averaged growth r a t e s was high-l y s i g n i f i c a n t f o r a l l periods beginning a t 6 days of in c u b a t i o n and f o r the periods 8-16 and 8-18 days of i n c u b a t i o n . Duncan's 42 t e s t (Table X L I X ) indicated that for each of the growth i n t e r v a l s i n which the storage period had a s i g n i f i c a n t e f f e c t on the em-bryo growth rate, each week of storage resulted i n a s i g n i f i c a n t increase i n growth rate except the increase between one and two weeks' storage within the 8-18 day growth i n t e r v a l . These re-s u l t s agree very closely with the r e s u l t s of Experiment 1. The effect of s i r e l i n e on the averaged growth rates was s i g n i f i c a n t only during the 8-12 day period (Table X L V I I I ) and during t h i s period the mean growth rate of the embryos from the WR sire l i n e was greater than that of the embryos from either the NH or WL l i n e s , but these l a t t e r means were not s i g n i f i c a n t l y d i f f e r e n t from each other (Table L ) . The data i n Table X L V I I I indicate that the e f f e c t of dams on the averaged embryo growth rates was s i g n i f i c a n t during the 6-14 and 8-1$ day i n t e r v a l s , highly s i g n i f i c a n t during the 6-16, 6-18, 8-14 and 8-16 day i n t e r v a l s and non-significant dur-ing the remaining periods. Duncan's t e s t , however, indicated that even during the periods when the dam effect was highly s i g -n i f i c a n t , there was no clear relationship between the dam means (Table L I ) . Again, perhaps the lack of genetic d i v e r s i t y masked any clear understanding. The s i r e x dam i n t e r a c t i o n of averaged growth rates was s i g n i f i c a n t during a number of the analyzed periods and probably had a connection with the lack of d e f i n i t i o n of the sire and dam l i n e means, however, i n view of the probable sampling errors i n 43 dach subc lass w i t h i n the i n t e r a c t i o n means, a meaningful i n t e r -p r e t a t i o n of t h i s e f f e c t was not p o s s i b l e . B y e r l y et a l . (1938) were unable to de t ec t s i g n i f i c a n t gene t i c d i f f e r e n c e s i n embryonic growth w i t h the use of a func -t i o n which r e l a t e d l o g weight to l o g t ime du r ing the p e r i o d two to twenty days of i n c u b a t i o n . In the present i n v e s t i g a t i o n , however, both experiments demonstrated s i g n i f i c a n t gene t ic d i f -ferences i n growth du r ing in te rmed ia te embryonic s tages . There were a l s o i n d i c a t i o n s tha t growth du r ing the l a t e r stages o f i n -cuba t ion was i n v e r s e l y r e l a t e d to growth du r ing e a r l i e r s t ages . C o n s i d e r a t i o n o f t h i s con t ras t i n growth between e a r l y and l a t e stages of i n c u b a t i o n would seem to s a t i s f a c t o r i l y account f o r the l a c k of gene t i c d i f f e r e n c e repor ted by the p rev ious au thors , f o r they cons idered the data from two to twenty days of i n c u b a t i o n as a whole and used the l e a s t squares s o l u t i o n to o b t a i n the l i n e s of best f i t f o r each gene t ic c l a s s . The i n h i b i t i o n o f growth dur -i n g the l a t e r stages would tend to wipe out any gene t i c d i f f e r -ences which might e x i s t i n e a r l i e r s t ages . P o s t - h a t c h i n g Body Weights (Males) The percentage sums of squares and the s i g n i f i c a n c e o f the p a r t i t i o n e d e f f e c t s obtained from the analyses of va r i ance of the weekly body weights o f male c h i c k s are presented i n Table L I I . The e f f e c t of s i r e s on body weight was h i g h l y s i g n i f i c a n t a t a l l weighings except tha t at ha tbh . Duncan's t e s t (Table L I I ) i n d i -cated tha t from hatch to two weeks of age the mean weights of 44 chicks from the NH and WL s i r e l i n e s were not s i g n i f i c a n t l y d i f -ferent from each other, but were both s i g n i f i c a n t l y smaller than that of the WR s i r e l i n e . During the remaining weeks of the test , the means of each s i r e l i n e were s i g n i f i c a n t l y d i f f e r e n t .' from each other and increased i n the order WL, NH, WR, as observed i n the same period of Experiment 1. The dam ef f e c t was s i g n i f i c a n t at hatching weight and highly s i g n i f i c a n t during the remainder of the tes t . As i n Ex-periment 1, the mean weights of chicks from the three "pure" dam li n e s did not become consistently d i f f e r e n t from each other u n t i l the end of the t h i r d week (Table LV). Beginning at the t h i r d week the means of chicks from the WLxNH and the WLxWR dam l i n e s were generally intermediate to the means of the WL and NH dam l i n e s , whereas the mean weight of chicks from the NHxWR dam l i n e was intermediate to the means of the NH and WR dam l i n e s at a l l weighings except the f i r s t . Except f o r hatching weight the mean weight of the WR dam l i n e was consistently and s i g n i f i c a n t l y heav-i e r than that of any other dam l i n e s . With respect to th e i r ef-fe c t on six-week body weight, the dam l i n e s were ranked i n the ascending order WL, WLxNH, WLxWR, NH, NHxWR, WR. The r a t i o n e f f e c t on weekly body weights was highly s i g -n i f i c a n t from the end of the f i r s t week on, and the data indicated that the difference i n the mean weights of chicks i n favour of the b r o i l e r r a t i o n increased s t e a d i l y with age (Table LVI). Other factors which had s i g n i f i c a n t e f f e c t on weekly 45 body weights were the s i r e x dam and dam x r a t i o n i n t e r a c t i o n s . As the main e f f e c t s of r a t i o n and s i r e were w e l l d e f i n e d , i t i s probable t h a t these i n t e r a c t i o n s were caused by d i f f e r e n t i a l r e s -ponses of the dam l i n e s w i t h i n each s i r e or r a t i o n , as was ob-served f o r the s i r e x dam i n t e r a c t i o n of female body weights i n Experiment 1. Post-hatching Growth Rates (Males) In Table LVII are presented the percentage sums of squares and s i g n i f i c a n c e of the p a r t i t i o n e d e f f e c t s from the an-al y s e s of variance of weekly and average growth r a t e s of male c h i c k s . The s i g n i f i c a n c e of the s i r e e f f e c t was i d e n t i c a l to t h a t observed i n Experiment 1. S i r e s were h i g h l y s i g n i f i c a n t i n a l l i nstances except the 5-6 week growth pe r i o d during which the e f f e c t was s i g n i f i c a n t a t the .05 l e v e l of p r o b a b i l i t y . Compar-i s o n of the means by Duncan's t e s t (Table L V I I I ) i n d i c a t e d t h a t , as i n Experiment 1, the only time t h a t the mean weekly growth r a t e of the WR s i r e l i n e was s i g n i f i c a n t l y greater than that of the NH l i n e was during the f i r s t week. However, t h i s d i f f e r e n c e i n one-week growth, and probably the n o n - s i g n i f i c a n t d i f f e r e n c e s i n favour of the WR l i n e o c c u r r i n g i n l a t e r weeks, were enough t o cause a s i g n i f i c a n t d i f f e r e n c e i n the six-week growth r a t e of these two s i r e l i n e s . For the six-week growth r a t e and f o r growth r a t e s d u r i n g each weekly i n t e r v a l , except hatch to one week, the WL s i r e l i n e males were s i g n i f i c a n t l y i n f e r i o r to males from the other two s i r e l i n e s . The e f f e c t of dams on weekly growth r a t e s (Table LVII) 46 was g e n e r a l l y s i g n i f i c a n t , and as i n Experiment 1, the dam e f f e c t on the six-week growth r a t e was h i g h l y s i g n i f i c a n t . Comparison of the means again i n d i c a t e d that only during the f i r s t week was the mean growth r a t e of ch i c k s from the WR dam l i n e s i g n i f i c a n t l y g r e ater than a l l other dam l i n e means, and only i n the s i x t h week was the mean growth r a t e of chicks from the WL dam l i n e s i g n i f i -c a n t l y s m a l l e r than a l l other means. The dam l i n e means of the hatch to six-week average growth were i n the ascending order; WL, WLxWR, WLxNH, NH, NHxWR and WR. However, the second, t h i r d and f o u r t h means were not s i g n i f i c a n t l y d i f f e r e n t from each other. The e f f e c t of r a t i o n on weekly growth r a t e s of male chicks was h i g h l y s i g n i f i c a n t during the f i r s t four weeks, s i g -n i f i c a n t during the f i f t h and n o n - s i g n i f i c a n t d u r i n g the s i x t h . The r a t i o n e f f e c t on six-week growth r a t e was a l s o h i g h l y s i g n i f -i c a n t . . Comparison of the means (Table LX) i n d i c a t e d that the weekly growth r a t e of ch i c k s on the b r o i l e r r a t i o n was greater than th a t of chicks on the s t a r t e r r a t i o n only during the f i r s t three weeks. During the remaining three weekly periods the s i t u a t i o n was reversed. I t w i l l be remembered from Table LVI, however, that the d i f f e r e n c e i n body weight i n favour of the b r o i l e r - f e d c h i c k s continued to increase d u r i n g t h i s p e riod, i n d i c a t i n g again that e a r l y growth i s more important than l a t e r growth i n determining body weight advantage. Post-hatching Body Weights (Females) Table LXI contains the percentage sums of squares and 47 » t h e i r s i g n i f i c a n c e , from the analyses of variance of weekly body weights of female c h i c k s . The s i g n i f i c a n c e of the s i r e e f f e c t was s i m i l a r to t h a t observed f o r male c h i c k s . Table LXII i n d i -cates t h a t the mean weight of c h i c k s from the WL s i r e l i n e was s i g n i f i c a n t l y g r e a t e r at one week of age than that of the NH s i r e l i n e , although t h i s d i f f e r e n c e was n o n - s i g n i f i c a n t at two weeks. From three weeks on the means of each s i r e l i n e resumed the order and s i g n i f i c a n c e that had been observed p r e v i o u s l y . Except at hatch, the e f f e c t of dam l i n e s was h i g h l y s i g -n i f i c a n t (Table LXI) , and, as observed w i t h the male c h i c k s , the three "pure" dam l i n e s were s i g n i f i c a n t l y d i f f e r e n t from each other a f t e r three weeks of growth (Table L X I I I ) . During most of the growing pe r i o d the mean weights of the dam l i n e s assumed group-ings i n which the WL and WLxNH dam l i n e s were not s i g n i f i c a n t l y d i f f e r e n t from each other, but were both s i g n i f i c a n t l y l e s s than the NH, WLxWR and NHxWR dam l i n e s . These three l i n e s i n turn were s i g n i f i c a n t l y l e s s than the WR dam l i n e , but not s i g n i f i c a n t -l y d i f f e r e n t from each other. As with the male c h i c k s , the dam l i n e s were ranked i n the order; WL, WLxNH, WLxWR, NH, NHxWR and WR wi t h respect to t h e i r e f f e c t on six-week body weight. How-ever, the WLxWR, NH and NHxWR dam l i n e s were not s i g n i f i c a n t l y d i f f e r e n t from each other. The e f f e c t of r a t i o n on body weights of female chicks corresponded very c l o s e l y t o the e f f e c t observed w i t h male c h i c k s . Again the mean weights of the two r a t i o n s were s i g n i f i c a n t l y d i f -f e r e n t a f t e r the f i r s t week's growth, and again the margin i n 48 favour of the b r o i l e r r a t i o n i n c r e a s e d a t each weighing (Table LXIV). The s i r e x dam i n t e r a c t i o n was c o n s i s t e n t and prominent (Table LXI) and again i s assumed to be due t o d i f f e r e n t i a l r e s -ponse o f dams w i t h i n each s i r e . > P o s t - h a t c h i n g Growth Rates (Females) The percentage sums of squares of the weekly and s i x -week growth r a t e s of the female c h i c k s are presented i n Table LXV. The e f f e c t of s i r e l i n e on growth r a t e was h i g h l y s i g n i f i -cant i n every i n s t a n c e , i n c l u d i n g the 5-6 week growth p e r i o d , where the s i r e l i n e e f f e c t on male growth r a t e s had d e c l i n e d . I t can be seen from Table LXVI t h a t the s i g n i f i c a n t d i f f e r e n c e between the NH and WR s i r e l i n e s extended i n t o the second week's growth, where-as i n Experiment 1 i t had e x i s t e d only d u r i n g the f i r s t week. A l s o i n Table LXVI i t can be seen t h a t d u r i n g the hatch to one-week i n t e r v a l the mean growth r a t e of the WL s i r e l i n e was s i g n i f -i c a n t l y g r e a t e r than t h a t of the NH s i r e l i n e . In the an a l y s e s of f i r s t - w e e k growth r a t e s of both male and female c h i c k s i n Ex-periment 1 and of male c h i c k s i n Experiment 2, the mean growth r a t e of t h e WL s i r e l i n e was always g r e a t e r than the growth r a t e of the NH s i r e l i n e , however, i n these p r e v i o u s i n s t a n c e s , the d i f f e r e n c e was not s i g n i f i c a n t . The e f f e c t of dams on weekly growth r a t e was h i g h l y s i g -n i f i c a n t d u r i n g the f i r s t , t h i r d and f i f t h weeks, but non-s i g n i f i c a n t d u r i n g the other weekly p e r i o d s . The e f f e c t on the 49 six-week growth r a t e was a l s o h i g h l y s i g n i f i c a n t . Comparison of the means by Duncan's t e s t (Table LXVII) revealed that f o r each weekly i n t e r v a l and f o r the hatch to six-week period the dam ef -f e c t was l a r g e l y a t t r i b u t a b l e t o d i f f e r e n c e s between the WL or WLxNH dam l i n e s and the WR dam l i n e . On the b a s i s of average growth r a t e from hatch to s i x weeks the dam l i n e s were ranked i n the ascending order; WL, WLxNH, WLxWR, NH, NHxWR and WR, the same order that was observed f o r the average growth r a t e of the male c h i c k s , and f o r the six-week body weight of the male and female c h i c k s . As i n Experiment 1, the body weight d i f f e r e n c e s between the heavy l i n e s at s i x weeks of age were p r i m a r i l y due t o the d i f -f e r i n g growth r a t e s between hatch and one week of age. In both Experiments 1 and 2 the analyses of growth r a t e s i n d i c a t e d that f o r each sex the f i r s t week's growth r a t e o f the WL dam l i n e was always l e s s than t h a t of the NH dam l i n e , although these d i f f e r e n c e s were not s i g n i f i c a n t . When these observations are compared w i t h those of the WL and NH s i r e l i n e s where the r e -verse s i t u a t i o n holds, i t seems that the d i f f e r e n c e i n growth p a t t e r n may have some bearing on the s i r e x dam growth r a t e i n t e r -a c t i o n that occurred during e a r l y periods i n Experiments 1 and 2. The appearance of t h i s e a r l y i n t e r a c t i o n during the f i r s t week's growth and the subsequent l o s s during the l a t e r stages i n -f e r s that the presence of the c o n s i s t e n t s i r e x dam i n t e r a c t i o n i n body weight data has i t s o r i g i n at t h i s e a r l y age. I n - s o - f a r as weekly growth rate.does not give any evidence of n o n - a d d i t i v i t y 50 d u r i n g these l a t e r stages of growth i t would appear that s e l e c -t i o n programmes based on growth r a t e from one to s i x weeks of age, or perhaps l e s s , would have the advantage of a high degree of a d d i t i v e g e n e t i c v a r i a n c e when compared with s e l e c t i o n pro-grammes based on body weight alon e . Some c a u t i o n must be placed on t h i s i n t e r p r e t a t i o n s i n c e the evidence i s based on "pure" l i n e s and t h e i r c r o s s e s , although i n t h i s case the evidence appears c o n c l u s i v e . R a t i o n s had a h i g h l y s i g n i f i c a n t e f f e c t on growth r a t e d u r i n g the f i r s t t h ree and the l a s t weekly p e r i o d s as w e l l as on the six-week growth r a t e . Of the two remaining weekly p e r i o d s the r a t i o n e f f e c t was s i g n i f i c a n t d u r i n g the three to f o u r week i n t e r v a l and n o n - s i g n i f i c a n t d u r i n g the f o u r to f i v e week i n t e r -v a l . Comparison of the means, however, (Table LXVIII) r e v e a l e d t h a t the advantage of the b r o i l e r r a t i o n was r e v e r s e d a f t e r the f i r s t t h r e e weeks, as was the case w i t h male c h i c k s , although a g a i n the body weight margin i n favour of the b r o i l e r - f e d c h i c k s continued to i n c r e a s e . T h i s r e v e r s a l i n growth r a t e s (of c h i c k s f e d on the two r a t i o n s ) d i d not occur i n Experiment 1 except dur-i n g the t h i r d week's growth, where the e f f e c t was c o n s i d e r e d to be due to a d i f f e r e n t i a l response to v a c c i n a t i o n . The two s e t s of o b s e r v a t i o n s can be r e c o n c i l e d i f i t i s c o n s i d e r e d t h a t each c h i c k e n and/or i t s l i n e has a c e r t a i n g e n e t i c and t h e r e f o r e l i m i -t e d c a p a c i t y f o r growth and t h a t environment a f f e c t s only the r a t e a t which t h i s c a p a c i t y i s being expended at any g i v e n time. Thus, when the r e a c t i o n to v a c c i n a t i o n delayed the growth of the b r o i l e r -51 f e d c h i c k s they s t i l l had enough c a p a c i t y i n reserve to be able to expend i t at a f a s t e r r a t e than the s t a r t e r - f e d chickens, at l e a s t f o r the d u r a t i o n of the six-week t e s t p e r i o d . Embryo C o r r e l a t i o n s The simple c o r r e l a t i o n s of pre- and post-storage egg weights, embryo weights and date of l a y a t each i n c u b a t i o n period are presented i n Table LXIX. The c o r r e l a t i o n c o e f f i c i e n t of pre-storage egg weight w i t h embryo weight was s i g n i f i c a n t a t eight and s i x t e e n days of i n c u b a t i o n and h i g h l y s i g n i f i c a n t at fourteen and eighteen days. The c o e f f i c i e n t of post-storage egg weight w i t h embryo weight showed the same f l u c t u a t i n g p a t t e r n of s i g n i f -icance except that i t was a l s o s i g n i f i c a n t a t twelve days of i n -cubation. As i n Experiment 1, these d i f f e r e n c e s can be explained on the b a s i s of the extremely high c o r r e l a t i o n between date of l a y and embryo weight, i n conjunction with s i g n i f i c a n t r e l a t i o n s h i p s between date of l a y and pre- and post-storage egg weights t h a t e x i s t e d at e i g h t and fourteen days of i n c u b a t i o n . The f a c t that these l a t t e r c o r r e l a t i o n s e x i s t e d f o r the eggs which were broken out at some stages of i n c u b a t i o n and not at others i s i n e x p l i c a b l e except as experimental e r r o r . P a r t i a l c o r r e l a t i o n s between em-bryo weight and egg weight were not c a l c u l a t e d , however, i t i s b e l i e v e d by the author t h a t such c a l c u l a t i o n s would have shown th a t i f the e f f e c t of date of l a y was removed, the r e l a t i o n s h i p between embryo weight and egg weights would have become s i g n i f i -cant around twelve days of i n c u b a t i o n and shown an i n c r e a s i n g cor-r e l a t i o n t h e r e a f t e r . These observations t h e r e f o r e agree f a i r l y 52 c l o s e l y t o those of Bray and I t o n (1962), although the methods of d e t e r m i n i n g the c o r r e l a t i o n between egg weight and embryo weight were d i f f e r e n t . In c o n t r a s t to the r e s u l t s i n Experiment 1, the amount of v a r i a t i o n o f embryo weight due t o age of egg was r e l a t i v e l y constant d u r i n g the d i f f e r e n t s t a g e s of i n c u b a t i o n . P o s t - h a t c h i n g C o r r e l a t i o n s Table LXX presents the simple c o r r e l a t i o n s of time of hatch, storage p e r i o d and p r e - and p o s t - s t o r a g e egg weights w i t h weekly body weights from hatch t o s i x weeks of age. Time of hatch showed no s i g n i f i c a n t c o r r e l a t i o n with body weights, whereas i n Experiment 1 a h i g h l y s i g n i f i c a n t n e g a t i v e c o r r e l a t i o n was found. I t i s p o s s i b l e t h a t the r e l a t i o n s h i p observed between these t r a i t s i n Experiment 1 depended on the i n c u b a t i o n s t r e s s t h a t occurred i n t h a t experiment. The c o r r e l a t i o n between storage p e r i o d and c h i c k weight was n e g a t i v e d u r i n g a l l weighings and e s s e n t i a l l y i n agreement w i t h the r e s u l t s i n Experiment 1. They were h i g h l y s i g n i f i c a n t f o r the f i r s t t h r e e weighings and s i g n i f i c a n t u n t i l the f i f t h week's weighing. I t seems probable, however, t h a t t h i s r e l a t i o n -s h i p was due to the h i g h l y s i g n i f i c a n t c o r r e l a t i o n s o f p r e - and p o s t - s t o r a g e egg weights with c h i c k weights a t each weighing, i n c o n j u n c t i o n with the h i g h l y s i g n i f i c a n t c o r r e l a t i o n s of p r e - and p o s t - s t o r a g e egg weights w i t h storage p e r i o d (- .126 and - . 154 r e s p e c t i v e l y ) . A gr a d u a l i n c r e a s e i n egg s i z e d u r i n g the c o l l e c -t i o n and storage p e r i o d accounts f o r the s i g n i f i c a n t c o r r e l a t i o n of p r e - s t o r a g e egg s i z e and storage p e r i o d . The f a c t t h a t the 53 magnitude of the c o r r e l a t i o n of storage period w i t h hatching weight was not p r o p o r t i o n a l to that of egg weight with hatching weight could have been due to the l o s s of weight, by d r y i n g , of the e a r l i e r hatched c h i c k s , although the c o e f f i c i e n t between time of hatch.and storage period (- .051) was not s i g n i f i c a n t . The h i g h l y s i g n i f i c a n t r e l a t i o n s h i p between storage period and time of hatch observed i n Experiment 1 may have been another e f f e c t of the i n c u b a t i o n s t r e s s which apparently occurred i n that experiment. The c o r r e l a t i o n s between egg weight and weekly body weights seem to be i n general agreement wi t h r e p o r t s i n the l i t -e rature (Wiley, 1950b, Skoglund et a l . , 1952, T i n d e l and M o r r i s , 1964), and c o n f l i c t d i r e c t l y only w i t h r e p o r t s of Halbersleben and Mussel (1922) and Upp (1928), although d i f f e r e n c e s i n s t r a i n s could e x p l a i n the c o n f l i c t . The c o r r e l a t i o n c o e f f i c i e n t s of hatching time, storage p e r i o d , pre- and post-storage egg weights and six-week body weight w i t h weekly growth r a t e s from hatch to s i x weeks of age are pres-ented i n Table LXXI. Neither time of hatch nor storage period bore any s i g n i f i c a n t r e l a t i o n s h i p with weekly growth r a t e , whereas i n Experiment 1 both of these t r a i t s were found to have a nega-t i v e c o r r e l a t i o n up to two weeks of age. I t was observed i n Ex-periment 1 that i n c u b a t i o n s t r e s s may have given a temporary ad-vantage i n growth r a t e to embryos from those eggs which had been stored f o r l e s s time and thus could have maintained the d i f f e r -ences i n development of embryos that were a t t r i b u t a b l e to storage p e r i o d e f f e c t s u n t i l hatching. In t h i s way the i n c u b a t i o n s t r e s s 54 by i n c r e a s i n g the v a r i a t i o n i n time of hatch due to storage of eggs, could have magnified the r e l a t i o n s h i p s of time of hatch and storage period w i t h weekly growth r a t e s or body weights. Pre- and post-storage egg weights bore a h i g h l y s i g -n i f i c a n t negative r e l a t i o n s h i p to f i r s t week's growth r a t e , whereas the c o r r e l a t i o n c o e f f i c i e n t s of egg weights w i t h other weekly growth r a t e s were a l l negative but n o n - s i g n i f i c a n t . How-ever, i n Experiment 1 the d i r e c t i o n of c o r r e l a t i o n agrees complete-l y w i t h that of Experiment 2 , i n d i c a t i n g that a s m a l l but d e f i n i t e r e l a t i o n s h i p may e x i s t . As i n Experiment 1 , the highest c o r r e l a t i o n between six-week body weight and weekly growth r a t e s occurred w i t h the second week's growth. The c o e f f i c i e n t s d e c l i n e d t h e r e a f t e r , a l -though a l l , i n c l u d i n g the f i r s t week's, were h i g h l y s i g n i f i c a n t . As p r e v i o u s l y observed the e a r l y growth periods (hatch to one week and one to two weeks) have considerable i n f l u e n c e on six-week body weight. C o r r e l a t i o n s of Embryo and Post-hatching Data Within  "Genotypes" As i n Experiment 1 , "genotypic" estimates of weight and growth r a t e were obtained f o r embryo stages and post-hatching ( w i t h i n sex and r a t i o n ) stages of development. The c o r r e l a t i o n c o e f f i c i e n t s of six-week body weight w i t h each of the other cor-responding "genotypic" estimates are presented i n Table L X X I I . Six-week growth r a t e and weekly body weights from the 55 end of the f i r s t week on were h i g h l y s i g n i f i c a n t l y c o r r e l a t e d w i t h six-week body weight. The "genotypic" hatching weight estimates of both male and female c h i c k s on the s t a r t e r r a t i o n were a l s o s i g -n i f i c a n t l y c o r r e l a t e d w i t h six-week body weight estimates. The c o r r e l a t i o n c o e f f i c i e n t s of six-week body weights w i t h embryonic growth r a t e s during two-day periods from s i x to eighteen days increased u n t i l s i g n i f i c a n c e was reached at the ten to twelve day i n t e r v a l , and then became negative and non-s i g n i f i c a n t during the remainder of the i n c u b a t i o n period. This p a t t e r n was i n general s i m i l a r to that of Experiment 1. The change to a negative r e l a t i o n s h i p a f t e r twelve days was presumably due to the growth r e s t r i c t i o n of those "genotypes" t h a t had grown f a s t e r i n the e a r l y stages e i t h e r by l i m i t of s h e l l s i z e or exhaustion of n u t r i e n t s as mentioned before. The smaller embryos at s i x and ei g h t days were much more subject to experimental e r r o r i n weigh-i n g and i t i s considered that the increase i n the magnitude of the c o e f f i c i e n t s up t o twelve days could be due more to a r e d u c t i o n of sampling e r r o r than to an a c t u a l increase i n the b i o l o g i c a l c o r r e l a t i o n . The c o r r e l a t i o n of eigh t t o twelve-day averaged embryo growth w i t h six-week body weight was h i g h l y s i g n i f i c a n t and the c o e f f i c i e n t s of c o r r e l a t i o n of embryo weight from twelve to e i g h t -een days, i n c l u s i v e , w i t h six-week body weight were i n general h i g h l y s i g n i f i c a n t . In connection w i t h these observations i t i s of i n t e r e s t to note the f o l l o w i n g statement by Bray ( I 9 6 5 ) : "The usefulness of embryonic weight as an a i d t o a l t e r i n g 56 the post embryonic growth of any species of b i r d s seems r e a l though i t w i l l have to be c a r e f u l l y evaluated i n each s i t u a t i o n . " I t should be noted t h a t the apparent r e l a t i o n s h i p between the growth periods which gave the highest s i g n i f i c a n c e to "genotypic" e f f e c t s and the higher c o r r e l a t i o n values between embryo growth and six-week weight (observed i n Experiment 1) d i d not hold f o r the data of Experiment 2. Between 81 and 92 per cent of the v a r i a t i o n i n "geno-t y p i c " six-week body weight was e x p l a i n a b l e i n terms of six-week growth r a t e alone, and between 34 and 42 per cent of the v a r i a -t i o n was e x p l a i n a b l e i n terms of only the eight to twelve-day embryo growth. Table LXXIII contains the "genotypic" c o r r e l a t i o n co-e f f i c i e n t s of six-week growth rate w i t h embryo growth r a t e s . The pa t t e r n was very s i m i l a r t o that obtained i n the c o r r e l a t i o n of six-week body weight. Again, g e n e r a l l y s i g n i f i c a n t c o e f f i c i e n t s were obtained w i t h ten to twelve-day embryo growth and h i g h l y s i g -n i f i c a n t c o r r e l a t i o n s were obtained w i t h eight to twelve-day averaged embryo growth r a t e s . As i n Experiment 1, the e i g h t t o twelve-day embryonic growth period gave the highest p o s i t i v e c o r r e l a t i o n and i t should be noted t h a t a general agreement between the two experiments ex-i s t s f o r the s i x to twelve-day period of i n c u b a t i o n . To the author's knowledge, t h i s i s the f i r s t i n stance where embryonic 57 growth has been c o r r e l a t e d w i t h e i t h e r post-hatching growth or body weights of the same "genotypes". Table LXXIV contains the c o e f f i c i e n t s of determination ( i . e . the percentage of the v a r i a t i o n of the dependent v a r i a b l e t h a t can be a t t r i b u t e d to the m u l t i p l e v a r i a t i o n of the indepen-dent v a r i a b l e s ) obtained from simple and m u l t i p l e l i n e a r regres-sions of the "genotypic" estimates of six-week body weight w i t h i n each sex and r a t i o n on s e l e c t e d v a r i a b l e s . The s e l e c t e d v a r i -ables were; six-week growth r a t e ( X ^ ) , embryo growth r a t e during the e i g h t to twelve-day i n t e r v a l (X2), embryo weight at fourteen days (X^), hatch weight (X^) and one-week body weight (X^). The data i n Table LXXIV i n d i c a t e s that hatch weight (X^) was the lowest s i n g l e c o n t r i b u t o r among the s e l e c t e d v a r i a b l e s and explained on the average only 22.1 per cent of the v a r i a t i o n i n six-week body weight. Embryo growth (X2) and embryo weight (X^) explained an average of 3 9 . 2 and 4 3 . 2 per cent of the v a r i a t i o n r e s p e c t i v e l y . Six-week growth r a t e (X-]_) was the highest s i n g l e c o n t r i b u t o r to the six-week body weight (86.6 per cent of the v a r i a t i o n was ex p l a i n e d ) . Six-week growth r a t e , having the high-est c o r r e l a t i v e value w i t h six-week body weight, was r e t a i n e d i n a l l m u l t i p l e l i n e a r r e g r e s s i o n analyses and the e f f e c t s of adding the other v a r i a b l e s , as w e l l as one-week body weight (X^), were t e s t e d . Embryo growth r a t e (X]_ and X2) gave a n o t i c e a b l e i n -crease i n the average p r o p o r t i o n of v a r i a t i o n explained (89.2 per c e n t ) , although c u r i o u s l y , i t caused a r e d u c t i o n i n the e x p l a i n -58 ed variance of six-week body weights of female c h i c k s on the b r o i l e r r a t i o n . The cause of t h i s r e d u c t i o n i s unknown. The f u r t h e r a d d i t i o n of embryo weight (X]_, X2and X3) made very l i t t l e d i f f e r e n c e to the explained v a r i a t i o n , however, the use of hatch weight i n s t e a d of the embryo weight (X]_, X2 and X/^ ) r a i s e d the amount of the explained variance to an average of 92.1 per cent. Six-week growth, embryo growth, hatch weight and embryo weight (X]_, X2, X3 and X^) explained no more of the v a r i a t i o n than when only the f i r s t three v a r i a b l e s were considered. The s u b s t i t u -t i o n of one-week body weight f o r hatch weight and embryo weight (X]_, X2 and X5) r a i s e d the pr o p o r t i o n of variance explained to 96.3 per cent, however, i t should be noted t h a t six-week growth r a t e and one-week body weight are not un r e l a t e d v a r i a b l e s . Re-i n c l u s i o n of embryo weight did not r a i s e the p r o p o r t i o n of var-iance explained, however, w i t h 96.3 per cent of the v a r i a t i o n i n t h i s data explained i n terms of only three v a r i a b l e s ; six-week growth r a t e , e i g h t to twelve-day embryonic growth and - one-week body weight, there i s very l i t t l e v a r i a t i o n i n six-week body weight l e f t unexplained. The e f f e c t s of each v a r i a b l e , considered e i t h e r s i n g l y or i n combination, were f a i r l y c o n s i s t e n t w i t h i n each sex and r a t i o n . Considerably more of the six-week body weight v a r i a t i o n of female c h i c k s was explained i n terms of t h e i r six-week growth r a t e than i n the case of the male c h i c k s , however, and i n most other r e g r e s s i o n s , l e s s of the v a r i a t i o n i n six-week body weight was explained i n the case of female c h i c k s on the b r o i l e r r a t i o n . 59 The data suggest that a m u l t i p l e l i n e a r r e g r e s s i o n an-a l y s i s , u s i n g one-week body weight, one t o six-week growth r a t e and e i g h t to twelve-day embryo growth r a t e as the independent v a r i a b l e s should e f f e c t i v e l y e x p l a i n p r a c t i c a l l y a l l the v a r i a t i o n i n six-week body weight. I t should be recognized, however, that i n t h i s data six-week growth r a t e alone e x p l a i n s the m a j o r i t y of the v a r i a t i o n . Further D i s c u s s i o n of Storage E f f e c t s on Embryo Weights and  Growth Rates In both experiments, each week of egg storage gave a s i g n i f i c a n t and cumulative depression of embryo weight at each stage of i n c u b a t i o n . However, when growth r a t e s of embryos were compared f o r eggs from each storage p e r i o d , a trend of increase i n the measured growth r a t e was observed f o r each week of storage. Averaged embryo growth r a t e s over d i f f e r e n t periods of i n c u b a t i o n g e n e r a l l y confirmed t h i s trend. The apparent i n t e r p r e t a t i o n of these observations i s that those embryos whose growth r a t e s were retarded by storage e f f e c t s i n the e a r l y stages of i n c u b a t i o n have a compensatory increase i n growth r a t e at l a t e r stages, which would tend to overcome the ear-l i e r e f f e c t . Kaufman, as c i t e d by Bohren et a l . , 1961, holds that only i n i t a t i o n of growth i s delayed by storage and that once s t a r t -ed, the growth r a t e s of the d i f f e r e n t storage groups of embryos are the same. To r e c o n c i l e t h i s b e l i e f w i t h the present data i t i s necessary to assume t h a t the embryos from the d i f f e r e n t storage 6 0 groups are supplying a d i f f e r e n t time s c a l e t o the f u n c t i o n y -at* 3 and that the growth of embryos of the d i f f e r e n t groups at e q u i v a l e n t p o i n t s of b i o l o g i c a l time are equal. This l a t t e r i n t e r p r e t a t i o n a l s o r e q u i r e s the assumption t h a t the growth r a t e (b) has a maximum value e a r l y i n the i n c u b a t i o n period and de-c l i n e s t h e r e a f t e r . Had the r e s u l t s of Experiment 1 only been considered, Kaufman's hypothesis would have been e n t i r e l y acceptable, f o r i n t h i s case the h i g h l y s i g n i f i c a n t c o r r e l a t i o n of hatching time and d u r a t i o n of egg storage ( r - . 4 5 2 ) i n d i c a t e d that eggs that were stored longer, hatched l a t e r . In Experiment 2 , however, the cor-r e l a t i o n between these two f a c t o r s ( - . 0 5 1 ) was n o n - s i g n i f i c a n t and i n d i c a t e s that the eggs from each storage period hatched at ap-proximately the same time. As Experiment 2 gave no evidence of any i n c u b a t i o n s t r e s s , the f i r s t i n t e r p r e t a t i o n seems more l i k e l y , f o r the compensatory growth would seem to have been s u f f i c i e n t l y great to overcome the e f f e c t s of delayed i n i t i a t i o n of growth. I t would seem from these r e s u l t s that s p e c i a l care must be taken to ensure t h a t i n c u b a t i o n c o n d i t i o n s are uniform during any ex-periment i n v o l v i n g egg storage e f f e c t s on embryonic or subsequent growth. SUMMARY A comparison was made of r a t e s of growth and body weights between pre- and post-hatching stages of development of the grow-i n g chicken as a f f e c t e d by s t r a i n s or s t r a i n crosses, egg storage, 61 egg weights, time of hatch, sex and post-hatching n u t r i t i o n a l environment. The i n t e r r e l a t i o n s h i p s of these f a c t o r s were a l s o i n v e s t i g a t e d . The three "pure" s t r a i n s used i n the study were: White Leghorns (bred f o r high egg p r o d u c t i o n ) , White Rocks (bred f o r meat) and New Hampshires (an intermediate t y p e ) . In Experiment 1, progeny of the nine p o s s i b l e combinations of the three pure s t r a i n s were used. In Experiment 2 nine e x t r a genotypes were obtained by i n c l u d i n g the three l i n e crosses ( s i n g l e and r e c i p -r o c a l crosses) i n the dam l i n e s . Eggs were gathered and st o r e d over a three week pe r i o d , i n d i v i d u a l l y recorded as to "genotype", date of l a y and pre- and post-storage egg weights. One-half of the eggs i n each e x p e r i -ment were broken out and.the embryos weighed on a l t e r n a t e days from s i x to eighteen days of i n c u b a t i o n . The sex of each embryo was recorded beginning at twelve days of i n c u b a t i o n i n Experiment 1 and beginning at ten days of in c u b a t i o n i n Experiment 2. The hatched chicks were d i v i d e d and r a i s e d on two n u t r i -t i o n a l environments provided by a commercial s t a r t e r r a t i o n and a commercial b r o i l e r r a t i o n . Rearing was done i n d u p l i c a t e f l o o r pens f o r each r a t i o n i n Experiment 1 and i n nine b a t t e r y brooders, each c o n t a i n i n g e i g h t compartments, i n Experiment 2. Chicks were weighed at hatch and at weekly i n t e r v a l s t h e r e a f t e r . The power f u n c t i o n y = atb (Roberts, 1964) was used t o 62 c a l c u l a t e weekly and six-week growth r a t e s f o r each hatched chick and f o r each "genotype". The same f u n c t i o n was used to c a l c u l a t e "genotypic" estimates of embryonic growth. Analyses of variance were c a l c u l a t e d on body weights and growth r a t e s during the pre-and post-hatching stages. C o r r e l a t i o n s between recorded t r a i t s were c a l c u l a t e d and "genotypic" estimates of six-week body weight were regressed on s e l e c t e d "genotypic" v a r i a b l e s . The f o l l o w i n g p o i n t s were brought out i n the r e s u l t s and d i s c u s s i o n : 1. Embryonic growth between eight and twelve days of incuba-t i o n was found to be s i g n i f i c a n t l y c o r r e l a t e d w i t h both six-week body weight and six-week growth r a t e . In ad-d i t i o n , both six-week growth r a t e and six-week body weight were found t o be s i g n i f i c a n t l y c o r r e l a t e d w i t h embryo weight at fourteen days of i n c u b a t i o n . 2. A h i g h l y s i g n i f i c a n t c o r r e l a t i o n was found between aver-aged estimates of six-week growth r a t e and six-week body weight ( r 2 = .866). 3 . M u l t i p l e l i n e a r r e g r e s s i o n based on averaged values showed that a high p r o p o r t i o n (92 per cent) of the v a r i a t i o n i n six-week body weight could be as s o c i a t e d w i t h the combin-ed v a r i a t i o n of eigh t t o twelve day embryo growth r a t e , hatching weight and six-week growth r a t e . 4. Each week of egg storage was a s s o c i a t e d w i t h a s i g n i f i -cant and cumulative depression of embryonic weights and 63 g e n e r a l l y s i g n i f i c a n t and cumulative increments i n em-bryonic growth r a t e during the s i x to eighteen day i n t e r v a l . 5. An apparent i n c u b a t i o n s t r e s s was observed i n E x p e r i -ment 1 which temp o r a r i l y but s i g n i f i c a n t l y modified the e f f e c t s of egg storage i n Experiment 1 i n favour of the eggs stored f o r one week or l e s s . 6. S i g n i f i c a n t 'genotypid' e f f e c t s on embryo weight were ob-served, concentrated mainly i n the p e r i o d of eight to fourteen days of i n c u b a t i o n . 7. S i g n i f i c a n t 'genotypic*' e f f e c t s on embryo growth were ob-served during various stages of i n c u b a t i o n and a tend-ency f o r growth r a t e s d u r i n g e a r l y and l a t e stages of i n c u b a t i o n to be i n v e r s e l y r e l a t e d was discussed. 8. A s i g n i f i c a n t sex e f f e c t i n embryonic weight i n favour of the males was observed. 9. S i g n i f i c a n t maternal e f f e c t s on hatching weight and s i g -n i f i c a n t genetic e f f e c t s on subsequent body weights up to s i x weeks of age were obtained. 10. Genetic d i f f e r e n c e s i n weekly and average growth r a t e s were s i g n i f i c a n t . The d i f f e r e n c e s i n six-week body weight between the two heavy l i n e s were mainly due to d i f f e r e n c e s i n growth r a t e during the f i r s t week of age. 64 11. A s i r e x dam i n t e r a c t i o n , s i g n i f i c a n t and c o n s i s t e n t throughout most analyses of post-hatching body weight, was found to be p r i m a r i l y due to a s i r e x dam i n t e r -a c t i o n present i n the f i r s t week of growth. The ad-vantages of a r e l a t i v e l a c k of non-additive e f f e c t s i n growth r a t e s from one t o s i x weeks of age, as compared to the presence of non-additive e f f e c t s i n body weights was discussed i n r e l a t i o n to s e l e c t i o n programmes. 12. Rations exerted an i n f l u e n c e on weekly body weights i n favour of the b r o i l e r r a t i o n . This d i f f e r e n c e became s i g n i f i c a n t and continued to increase a f t e r the f i r s t week's weighing. 13. Rations exerted a s i g n i f i c a n t e f f e c t on growth r a t e dur-i n g a l l but one of the growth i n t e r v a l s c a l c u l a t e d . In Experiment 2 the advantage of the b r o i l e r r a t i o n i n the e a r l y periods was reversed during the l a t t e r h a l f of the six-week growth p e r i o d . 14. A concept of a g e n e t i c a l l y l i m i t e d p o t e n t i a l f o r growth i n r e l a t i o n to environmental i n f l u e n c e s was discussed. 15. A s i g n i f i c a n t r e l a t i o n s h i p between pre- and post-storage egg weights and embryo weights which commenced around twelve days of i n c u b a t i o n and increased during the l a t e r stages was noted. 16. Pre- and post-storage egg weights bore a r e l a t i o n s h i p w i t h body weight which diminished with age but remained 65 h i g h l y s i g n i f i c a n t at l e a s t u n t i l s i x weeks i n both exper-iments. 17. Hatching time was found t o be c o r r e l a t e d w i t h l e n g t h of egg storage i n Experiment 1 but not i n Experiment 2. Hatching time was s i g n i f i c a n t l y and n e g a t i v e l y c o r r e l a -ted w i t h weekly c h i c k body weights i n Experiment 1 but not i n Experiment 2. Hatching time and storage period were s i g n i f i c a n t l y and n e g a t i v e l y c o r r e l a t e d w i t h weekly growth r a t e to two or three weeks of age r e s p e c t i v e l y i n Experiment 1 but no r e l a t i o n s h i p was evident i n E x p e r i -ment 2. These d i f f e r e n c e s were mainly a t t r i b u t e d to the in c u b a t i o n s t r e s s which was evidenced i n Experiment 1. 18. In general, six-week body weight of i n d i v i d u a l s bore h i g h l y s i g n i f i c a n t r e l a t i o n s h i p s with a l l weekly growth r a t e s . In both experiments the peak of s i g n i f i c a n c e occurred during the second week's growth p e r i o d . 19. The r e l a t i o n s h i p between weekly growth and pre- and post-storage egg weights was negative and i n some instances s i g n i f i c a n t . The i m p l i c a t i o n s of the two r e s u l t s men-tioned above were discussed as f a c t o r s i n a s e l e c t i o n programme based on e a r l y growth r a t e . These r e s u l t s i n d i c a t e that p r a c t i c a l l y a l l of the var-i a t i o n of six-week body weight i n t h i s data was s u c c e s s f u l l y ac-counted f o r by the combined e f f e c t s of six-week growth r a t e , hatching weight and embryonic growth r a t e between eight and twelve 66 days. The data a l s o i n d i c a t e that gains i n six-week body weight may be made by s e l e c t i n g f o r e a r l y growth r a t e without concomitant changes i n other t r a i t s . 67 BIBLIOGRAPHY Blunn, C.T. and P.W. Gregory. 1935. The embryological b a s i s of s i z e i n h e r i t a n c e i n the chicken. J . Exp. Z o o l . 7 0 : 397-414* Bohren, B.B., L.B. C r i t t e r d e n and R.T. King. 1961. Hatching time and h a t c h a b i l i t y i n the f o w l . P o u l t r y S c i . 40: 620-632. Bray, D.F. and E.L. I t o n . 1962. The e f f e c t of egg weight on s t r a i n d i f f e r e n c e s i n embryonic and post embryonic growth i n the domestic f o w l . B r i t i s h P o u l t r y S c i . 3 : 175-188. B y e r l y , T.C. 1930. The e f f e c t s of breed on the growth of the chick embryo. J . Morph. and P h y s i o l . 50: 341-359. 1932. Growth of the chick embryo i n r e l a t i o n to i t s food supply. J . Exp. B i o l . 9 : 15-44 . B y e r l y , T.C., W.C. H e l s e l and J.P. Quinn. 1938. Growth i n weight and c e l l number. Genetic e f f e c t s i n the chick embryo and chi c k . J . Exp. Z o o l . 78:185 -203. Coleman, J.W., H.S. S i e g e l and P.B. S i e g e l . 1964. Embryonic dev-elopment of two l i n e s of White Rocks. P o u l t r y S c i . 43: 453-458. Godfrey, E.F. and R.G. Jaap. 1952. Evidence of breed and sex d i f f e r e n c e s i n the weight of chic k s hatched from eggs of s i m i l a r weights. P o u l t r y S c i . 31: 1108-1109. Godfrey, G.F. and C. W i l l i a m s . 1955. U n s u i t a b i l i t y of chick weight:egg weight r a t i o as an i n d i c a t o r of post n a t a l growth. P o u l t r y S c i . 34: 164-166. Godfrey, G.F., C. Wi l l i a m s and C E . M a r s h a l l . 1953. The r e l a -t i v e i n f l u e n c e of egg s i z e , age at sexual m a t u r i t y and mat-ure body weight on growth to twelve weeks of age. P o u l t r y S c i . 3 2 : 496-500. Goodwin, K. I 9 6 I . E f f e c t of hatching egg s i z e and chick s i z e upon subsequent growth r a t e i n chickens. P o u l t r y S c i . 40: 1408. Halbersleben, D.L. and F.E. Mussehl. 1922. R e l a t i o n of egg weight to chick weight at hatching. P o u l t r y S c i . 1: 143-144. Henderson, E.W. 1930. Growth and development. XVI. The i n -fluence of temperature and breeding upon the r a t e of growth of c h i c k embryos. Univ. M i s s o u r i A g r i c . Exp. Sta. Res. B u l l . 149: 5-47 . 68 J u l l , M.A. and B.W. Heywang. 1930. Yolk assi m i l a t i o n during the embryonic development of the chick. Poultry S c i . 9: 393-404. J u l l , M.A. and J.P. Quinn. 1925. The re l a t i o n s h i p between the weight of eggs and the weight of chicks according to sex. J. of A g r i c u l t u r a l Research pp. 223-226. Kosin, I.L., H. Abplanalp, J. Gutierrez and J.S. Carver. 1952. The influence of egg size on subsequent early growth of the chick. Poultry S c i . 31: 247-254. Lerner, I.M. 1939. The shape of the chick embryo growth curve. Science 89: 16-17 , No. 2297. Lerner, I.M. and V.S. Asmundson. 1938. Genetic growth constants i n domestic fowl. Poultry S c i . 17: 286-294. McNary, H.W., A.E. B e l l and C.H. Moore. I960 . The growth of i n -bred and hybrid chicken embryos. Poultry S c i . 39: 378-384. Monro, S.S. and I.L. Kosin. 1940. The existance of a sex d i f -ference i n the weight of day-old chicks, with further data on egg weight-chick weight r e l a t i o n s h i p . S c i . Agr. 20: 586-591. Murray, H.A. J r . 1925. Physiological ontogeny. A. Chicken em-bryos. I I I . Weight and growth rate as functions of age. J. Gen. Physiol. 9 : 39-48. O'Neil, J.B. 1950. Relationship of chick size to egg size and i t s e f f e c t upon growth and mortality. Poultry S c i . 29: 774. Ralston, A. and H.S. Wilf . 1962. Mathematical methods fo r d i g i -t a l computors. London: Clapman and H a l l Ltd. Roberts, C.W. I 9 6 4 . Estimation of early growth rate i n the chick-en. Poultry S c i . 43: 238-252. . 1965. One week body weight and bi-weekly early growth rate as related to 7 week body weight i n the chicken. Poultry S c i . 44: (4) In Press. Skoglund, W.C., K.C. Seegar and A.T. Ringrose. 1952. Growth of b r o i l e r chicks hatched from various sized eggs when reared i n competition with each other. Poultry S c i . 31 : 796-799. S t e e l , R.G.D. and I.H. Torrie. P r i n c i p l e s and procedures of s t a t -i s t i c s . I960 . New York: McGraw-Hill Book Co., pp. 107-109. Tindel, D. and D.R. Morris. I 9 6 4 . The e f f e c t s of egg weight on subsequent b r o i l e r performance. Poultry S c i . 4 3 : 534-539. Upp, C.W. 1928. Egg weight, day old chick weight and rate of growth i n Single Comb Rhode Island Red chicks. Poultry S c i . 7: 151-155. 69 Wiley, W.H. 1950a. The i n f l u e n c e of egg weight on the pre-hatching and post-hatching growth r a t e i n the f o w l . I . Egg weight-embryonic development r a t i o s . P o u l t r y S c i . 29: 570-574. . 1950b. The i n f l u e n c e of egg weight on the pre-hatching and post-hatching growth r a t e i n the f o w l . I I . Egg weight-chick weight r a t i o s . P o u l t r y S c i . 29: 595-604. W i l l i a m s , C., G.F. Godfrey and R.B. Thompson. 1951. The e f f e c t of r a p i d i t y o f hatching on growth, egg production, m o r t a l i t y and sex r a t i o s i n the domestic f o w l . P o u l t r y S c i . 3 0 : 599-6 0 6 . TABLE I STATISTICAL MODELS FOR ANALYSES OF VARIANCE OF EMBRYO DATA Model Observation Component Eff e c t s General E (sdh j Pk (sp)ik (dp) jif (spd)i i h ( s f ) n ( d f ) ( 1 l ( P f ) k l (sdfJi.u ( s p f ) i k i (dpf).ikl * a Ew-i j t 1 •f + + + +• + + + + 4 + -XT b + + -r — c E b i ik + + + + — d E w i i k l + + + — — — + — — — — — — -r e E b i . i k l + f — — — — — — — — — + f E b i j k l + + — — — - — — — — — - •+ g E W i j k t + + + — — — + h E b i i k + i + -r + — • — — * The residual effect E f f e c t s Analyzed Included within the residual effect Ew Embryo weight Eb Embryo growth rate o TABLE I I F VALUES FROM THE ANALYSES OF VARIANCE OF EMBRYO WEIGHTS RECORDED AT 12, 14, 16 AND 18 DAYS OF INCUBATION USING STATISTICAL MODEL ( a ) : EXPERIMENTS 1 AND 2 Days of Incubation 12 14 16 18 Experiment Sources of V a r i a t i o n df 1 2 1 2 1 2 1 2 Sex (Sx) 1 0.09 5.81* 13.19** 2.65 3.66 1 .29 0.10 2.52 Storage Period (P) 2 93.50** 75 .09** 74.85** 106.06** 39.91** 26.01** 38.86** 117.37*: S i r e (S) 2 18.80** 5.62* 41.95** 2.69 2.39 2.21 1.73 13.74* Dam (D) 2 15.67** 3.74* 29.88** 11.05** 3.79 1.41 7.85* 3 .26* Sx x P 2 0.78 1.42 0.68 0.24 2.07 0.27 0.88 1.56 Sx x S 2 0.50 1.63 0.01 1.64 0.06 0.36 2.36 3.09 Sx x D 2 1.62 1.13 2.08 0.71 0.71 1.21 0.75 1.60 P x S 4 0.50 1.12 1.47 1.27 2.88 1 .72 4 .29* 0.78 P x D 4 0.33 2.65* 0.96 1.04 2.41 0.74 0 .09 1.07 S x D 4 1.21 2.38* 2.31 0.91 1.61 1.22 3.17 6.32*; TABLE I I (Continued) Days of Incubation 12 14 16 18 Expe riment Sources of V a r i a t i o n df 1 2 1 2 1 2 1 2 Sx x P x S 4 0.30 0.58 1.87 1.08 1.00 0.10 2.86 2.45 Sx x P x D 4 0.33 1.02 1.21 0.83 1.35 1.15 1.34 1.87 Sx x S x D 4 1.02 0.93 3.18 1.58 1.41 0.58 1.04 2.58* P x S x D 8 3.31 0.94 4.24* 0.87 1.30 0.69 4.73* 1.44 R e s i d u a l 8 * S i g n i f i c a n t a t .05 p r o b a b i l i t y ** S i g n i f i c a n t at .01 p r o b a b i l i t y TABLE III PERCENTAGE SUMS OF SQUARES FROM THE ANALYSES OF VARIANCE OF EMBRYO WEIGHTS AT TWO DAY INTERVALS FROM 6 TO 18 DAYS OF INCUBATION: EXPERIMENT 1 S t a t i s t i c a l Model % ii g d g a a a a Source of Var i a t i o n df df 6 8 Days i 10 of Incubation 12 14 16 18 Sex 1 # # # 0.03 3 . 3 1 * 2.25 0.05 Storage Period 2 2 79.10** 56.88** 60.60** 60 .13** 37 .61** 49.12** 3 8 . 5 0 * * Sire 2 2 3.36 6 .21 5 .09* 1 2 . 0 9 * * 21.08** 2.94 1.71 Dam 2 2 4.39 6.44 1.92 10 .08** 15 .02** 4 .67 7.77 Sire x Dam 4 4 2.91 7.88 21.97** 1.55 2.32 3.96 6.27 Residual 16 42 10.22 22.58 10.41 16.12 20 .66 37.07 45.70 # Not Measured * S i g n i f i c a n t a t .05 probability ** Si g n i f i c a n t at .01 probability 74 TABLE IV EFFECT OF DURATION OF PREINCUBATION EGG STORAGE ON EMBRYO WEIGHTS RECORDED AT TWO DAY INTERVALS FROM 6 TO 18 DAYS OF INCUBATION: EXPERIMENT 1 Mean Embryo Weights (Grams) Duration of Storage (Weeks) Days of Incubation 1 2 3_ 6 .432 .346 .244 8 1.262a 1.197a .992 10 2.587 2.186 1.896 12 6.032 5.492 4.710 14 11.554 10.420 9.698 16 17.818 17.047 15.295 18 25.542 23.893 22.418 Those means within the same row which carry the same superscript are not significantly different at . 0 5 probability. 75 TABLE V EFFECT OF SIRE LINE ON EMBRYO WEIGHTS RECORDED AT TWO DAY INTERVALS FROM 6 TO 18 DAYS OF INCUBATION: EXPERIMENT 1 Days of Incubation Mean Embryo Weights (Grams) Sire Line WL NH WR 6 . 3 2 3 a . 3 6 l b .338 a b 8 1.101 a 1.194 a 1.157 a 10 2.178 a b 2.338 b 2.152 a 12 5.132 5.377 5.725 14 9.938 10.417 11.318 16 I6.388 a I 6 . 7 5 5 a b 17.017 b 18 23.919 a 23.639 a 24.295 a Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . 76 TABLE VI EFFECT OF DAM LINE ON EMBRYO WEIGHTS RECORDED AT TWO DAY INTERVALS FROM 6 TO 18 DAYS OF INCUBATION: EXPERIMENT 1 Mean Embryo Weights (Grams) Dam Line Days of Incubation WL NH WR 6 .315 a . 3 4 9 a b .357 i b 8 1 . 1 0 4 a 1 . 1 9 9 a 1 . 1 4 8 a 10 2 . 1 7 5 a , . 2 . 2 9 3 a 2 . 2 0 1 a 12 5.150 5.391 5.693 14 10.074 10.383 11.216 16 16.386 a 1 6 . 6 l 2 a b 1 7 . l 6 l b 18 23.152 24.231 a 24.470 a Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . 77 TABLE VII EFFECT OF SEX ON EMBRYO WEIGHTS RECORDED AT TWO DAY INTERVALS FROM 12 TO 18 DAYS OF INCUBATION: EXPERIMENT 1 Mean Embryo Weights (Grams) Days of Incubation Males Females 12 5.400a 5.423 a 14 10.784; 10 . 3 3 r 16 I6 . 9 4 6 a I6.494 a 18 23.996a 23.906a Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . TABLE VIII PERCENTAGE SUMS OF SQUARES FROM THE ANALYSES OF VARIANCE OF EMBRYO GROWTH RATES DURING SUCCESSIVE TWO DAY INTERVALS BETWEEN 6 AND 18 DAYS OF INCUBATION: EXPERIMENT 1 S t a t i s t i c a l Model h f h h f f f f Source of Variat i o n df df 6-8 Intervals (Days 8-10 10-12 of Incubation) 12-14 14-16 16-18 Sex 1 # # 0.08 9.44* 0.94 1.22 Storage Period 2 2 50.68** 15.20* 6.16* 17.76** 5.22 3.32 Sire 2 2 1.18 5.59 26 .75** 1.09 12.82* 2.45 Dam 2 2 5.09 1.19 10.27** 1.15 6.98 1.76 Sire x Dam 4 4 7.12 51.42** 25.66** 12.41 6.07 6.60 Residual 16 42 35.93 26 .59 31.08 58.19 67.98 84.66 # Not Measured * S i g n i f i c a n t at .05 p r o b a b i l i t y ** S i g n i f i c a n t at .01 p r o b a b i l i t y 79 TABLE IX EFFECT OF DURATION OF PREINCUBATION EGG STORAGE ON EMBRYO GROWTH RATES DURING SUCCESSIVE TWO DAY INTERVALS FROM 6 TO 18 DAYS OF INCUBATION: EXPERIMENT 1 Mean Embryo Growth Rates Duration of Storage Period (Weeks) Incubation Intervals (Days) 1 2 3_ 6-8 3.725 4.326 4.923 8-10 3 . 2 1 0 a 2 . 6 8 8 b 2 . 9 0 6 a b 10-12 4.662 5 . 0 5 5 a 4 . 9 9 7 a 12-14 4 . 2 1 7 a 4.141 a 4.67$ 14-16 3 . 2 5 3 a 3 . 7 0 4 a 3.441 a 16-18 3 . 0 6 l a 2 . 8 6 7 a 3 . 2 3 6 a Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . 80 TABLE X EFFECT OF SIRE LINE ON EMBRYO GROWTH RATES DURING SUCCESSIVE TWO DAY INTERVALS FROM 6 TO 18 DAYS OF INCUBATION: EXPERIMENT 1 Mean Embryo Growth Rates S ire Lines Incubation Interva ls (Days) WL NH WR 6-8 4 . 3 7 a 4 .22 a 4 .38 a 8-10 3 . 0 6 a 2 .99 a 2 .76 a 10-12 4 . 7 0 a 4 .60 a 5.41 12-14 4 . 3 0 a 4 .30 a 4 . 4 3 a 14-16 3 . 7 6 a 3 . 5 6 a b 3 . 07 b 16-18 3 . 2 3 a 2 .93 a 2 .99 a Those means wi th in the same row which carry the same superscr ipt are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . SI TABLE XI EFFECT OF DAM LINE ON EMBRYO GROWTH RATES DURING SUCCESSIVE TWO DAY INTERVALS FROM 6 TO 18 DAYS OF INCUBATION: EXPERIMENT 1 Mean Embryo Growth Rates Dam Lines Incubation Intervals (Days) WL NH WR 6-8 4 . 5 2 a 4.32 a 4.14a 8-10 3.02 a 2.88 a 2 . 9 1 a 10-12 4.77 a 4.72 a $.22 12-14 4.35 a 4 . 2 7 a 4.42 a 14-16 3.68 a 3 . 5 $ a 3 . 1 7 a 16-18 2.94 a 3.20 a 3.03 a Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 pr o b a b i l i t y . TABLE XII PERCENTAGE SUMS OF SQUARES FROM THE ANALYSES OF VARIANCE OF EMBRYO GROWTH RATES WHEN AVERAGED FOR INTERVALS BEGINNING AT 6 OR 8 DAYS OF INCUBATION: EXPERIMENT 1 S t a t i s t i c a l Model h f h. f f f f f f f f Source of Variance df df 6-10 6-12 Intervals (Days of Incubation) 6-14 6-16 6-18 8-12 8-14 8-16 8-18 Storage Period 2 2 32 .22* 38 .07** 48 .78** 56". 87** 53.58** 1.83 1 5 . 8 8 * * 14.43* 24.41** S i r e 2 2 3 .01 13.79** 12 .05** 4 .72* 8.28* 2 2 . 4 5 * * 16 .67** 4 .29 12.17* Dam 2 2 8.23 4.58 4.91* 6 . 4 3 * 2.19 18 .27** 14.38** 5.25 0.61 Sire x Dam 4 4 19.53 4.95 1 0 . 6 3 * * 2.59 2.16 11.88* 16.60* 9.54 7.38 Residual 16 43 37.01 38.61 23.63 29.39 : 33.84 45.58 36.46 66.49 55.43 * S i g n i f i c a n t a t .05 probability ** S i g n i f i c a n t at .01 probability CO. 83 TABLE XIII EFFECT OF EGG STORAGE ON AVERAGED TWO. DAY EMBRYO GROWTH RATES: EXPERIMENT 1 Mean Averaged Embryo Growth Rates Storage Period (Weeks) Range of Intervals Averaged (Days) 1 2 3 6-10 3.47a 3.51 a 3.91 6-12 3.87 4.02 4.28 6-14 3.95 4.05 4.38 6-16 3.81 3.98 4.19 6-18 3.69 3.80 4.03 8-12 3 . 9 4 a 3.87a 3.95 a 8-14 4.03 a 3.96a 4.19 8-16 3.84a 3.90 a b 4.01 b 8-18 3.68a 3.69a 3.85 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . 84 TABLE XIV EFFECT OF SIRE LINE ON AVERAGED TWO DAY EMBRYO GROWTH RATES: EXPERIMENT 1 Mean Averaged Embryo Growth Rates Sire Line Range of Intervals Averaged (Days) WL NH WR 6-10 3.7l a 3.60a 3.57a 6-12 4.04a 3.94a 4.18 6-14 4.11a 4.03a 4.25 6-16 4.04a 3.93b 4.01 a b 6-18 3.91a 3.77b 3.84 a b 8-12 3.88a 3.79a 4.08 8-14 4.02a 3.96a 4.20 8-16 3.96a 3.86a 3.92a 8-18 3.8l a 3.68b 3.73 a b Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . 85 TABLE XV EFFECT OF DAM LINE ON AVERAGED TWO DAY EMBRYO GROWTH RA.TES: EXPERIMENT 1 Mean Averaged Embryo Growth Rates Dam Line Range of Intervals Averaged (Days) WL NH WR 6-10 3 . 7 7 a 3.60 a 3 . 5 2 a 6-12 4 . 1 0 a 3 . 9 7 a 4 . 0 9 a 6-14 4 . l 6 a 4 . 0 4 4 . 1 7 a 6-16 4.07 3 . 9 5 a 3 . 9 7 a 6-18 3 . 8 8 a 3.82 a 3 . $ l a 8-12 3.89 a 3.80 a 4.07 8-14 4 . 0 5 a 3 . 9 6 a 4.18 8-16 3.95 a 3 . 8 5 a 3 . 9 3 a 8-1$ 3 . 7 5 a 3 . 7 2 a 3 . 7 5 a Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . TABLE XVI PERCENTAGE SUMS OF SQUARES FROM THE ANALYSES OF VARIANCE OF,-MALE BODY WEIGHTS AT WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 1 S t a t i s t i c a l Model i i i i i i i i Source of Variance df Hatch Week 1 Time Week 2 of Weighing Week 3 Week 4 Week 5 Week 6 Sires (S) 2 0.42 11.35* 12.67** 20.26** 27.50** 31.13** 33.44** Dams (D) 2 46.14** 58.37** 55.09** 60.56** 57.27** 53.70** 51.00** Rations (R) 1 0.99 0.27 13.86** 0.43 3.47** 4.56** 5.98** S x D 4 11.61 6.22 6.86* 6.56* 4.78** 3.85* 3.13* S x R 2 0.19 0.19 0 .09 0.70 0.58 0.69 0.52 D x R 2 11.84* 3 .31 1.94 3.28* 1.58 1.53 1.40 S x D x R 4 6 .07 1.24 0.24 0.30 0.51 0.58 0.57 Residual 18 22.75 19.08 9.25 7.90 4.31 3.95 3.97 * S i g n i f i c a n t at .05 p r o b a b i l i t y ** S i g n i f i c a n t at .01 p r o b a b i l i t y 87 TABLE XVII EFFECT OF SIRE LINE ON BODY WEIGHTS OF MALE CHICKS AT WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 1 Mean Body Weights of Chicks (Grams) Sire Line Time of Weighing WL NH WR Hatch 43.0a 42.8a 42.8a 1 Week 71.2a 67.6 7 2 .8 a 2 Weeks 139.6a 1 3 9 .8 a 152.8 3 Weeks 231.2 249.7 266.6 4 Weeks 326.4 368.7 391.5 5 Weeks 447.6 520.7 551.8 6 Weeks 580.7 690.8 722.9 Those means within the same row which carry the same superscript are not significantly different at .05 probability. TABLE XVI I I MEANS AND STANDARD DEVIATIONS OF PRE- AND POST-STORAGE EGG WEIGHTS, ACCORDING TO DM LINE AND SEX OF HATCHED CHICKS Sex of Hatched Chicks Males Females WL NH Post-storage Egg Wt. Pre-storage Egg Wt. WR Pre-storage Egg Wt. Post-storage Egg Wt. Standard Standard lean D e v i a t i o n Mean D e v i a t i o n ^ E g f w t ? ^ 6 0 ' 5 3 ' 5 1 6 0 ' 6 3.64 59.7 3.42 59.7 3.67 62.2 4.57 62.1 4.44 Post-storage , , , . Egg Wt. 6 1 , 6 ^* 6 0 6 1 , 5 59.0 3 . 8 6 59.0 4 . 2 3 58 . 2 3 . 9 2 5 8 . 2 4 . 3 0 89 TABLE XIX EFFECT OF DAM LINE ON BODY WEIGHTS OF MALE CHICKS AT WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 1 Time of Weighing Hatch , 1 Week 2 Weeks 3 Weeks 4 Weeks 5 Weeks 6 Weeks Mean Body Weights of Chicks (Grams) Dam Line WL NH WR 4 2 . 5 £ 6 6 . 7 ' 132.2 £ 223.5 319.7 442.5 557.1 41.9J 67.4£ 138.r 241.0 353.1 495.8 656.3 44.2 77.5 162.0 283 .1 413.8 581.7 760.9 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . 90 TABLE XX EFFECT OF RATION ON BODY WEIGHTS OF MALE CHICKS AT WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 1 Mean Time of Weighing Hatch 1 Week 2 Weeks 3 Weeks 4 Weeks 5 Weeks 6 Weeks Body Weight Rat B r o i l e r 4 2 . 7 a 7 0 . 9 a 150.5 251.3 a 371.8 523.4 690.6 of Chicks (Grams) ons Starter 4 3 . 0 a 7 0 . 2 a 137.6 2 4 7 . l a 352.6 4 9 0 . 0 639.0 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . TABLE XXI PERCENTAGE SUMS OF SQUARES FROM THE ANALYSES OF VARIANCE OF WEEKLY AND AVERAGE GROWTH RATES OF MALE CHICKS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 1 S t a t i s t i c a l Model 3 3 3 3 3 3 3 3 Source of Variance df Hatch-1 1-2 Period of 2-3 Growth 3-4 (Weeks) 4-5 5-6 Hat eh-. 6 Sires (S) 2 20.25** 20.51** 29 . 6 5 * * 30.98** 39.31** 21.25* 48.65** Dams (D) 2 43.54** 12.15* 8.66* 9.87* 10.07 9.65 32 . 3 0 * * Rations (R) 1 1.42 39.69** 38.90** 23.46** 8.02* 10 . 03 7.75** S x D 4 10.41 3.70 1.50 5.14 7.04 3.00 2.95 S x R 2 0.43 0.16 2.57 0.07 0.47 1.50 0.18 D x R 2 0.65 1.39 0.93 4.09 0.95 5.72 1.60 S x D x R 4 1.40 1.15 1.48 1.55 2.87 3.35 1.16 Residual 18 21.89 21.25 16.32 24 .84 31.27 45.51 5.40 * S i g n i f i c a n t at .05 probability ** S i g n i f i c a n t at .01 probability 92 TABLE XXII EFFECT OF SIRE LINE ON GROWTH RATES OF MALE CHICKS DURING WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 1 Mean Growth Rates S ire Lines Growth Intervals (Weeks) WL NH WR Hatch-1 1 .72 a 1.56 1.84* 1- 2 3.00 3 .24 a 3 . 3 1 a 2- 3 2.76 3 . 1 8 a 3 . 0 6 a 3- 4 2.21 2 .52 a 2 .48 a 4- 5 2.35 2 .58 a 2 .57 a 5- 6 2 .22 a 2 . 41 b 2 .29 a Hatchr>6 2.38 2 .58 a 2 .59 a Those means wi th in the same row which carry the same superscr ipt are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . 93 TABLE XXIII EFFECT OF DAM LINE ON GROWTH RATES OF MALE CHICKS DURING WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 1 Mean Growth Rates Dam Lines Growth Intervals (Weeks) WL NH WR Hatch-1 1 . 5 6 a 1 . 6 2 a 1.94 1-2 3 . 0 5 a 3 . 2 0 a b 3 .30 b 2- 3 2.86 3 . 0 7 a 3 . 07 a 3- 4 2.30 2 .47 a 2 .45 a 4- 5 2.43 2 .53 a 2 .55 a 5- 6 2 .25 a 2 .38 b 2 . 2 8 a b Hat.ch-6 2.41 2.55 2.60 Those means wi th in the same row which carry the same superscr ipt are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . 94 TABLE XXIV EFFECT OF RATION ON GROWTH RATES OF MALE CHICKS DURING WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 1 Mean Growth Rates Rations Growth Intervals (Weeks) B r o i l e r Starter Hatch-1 1.74a 1 . 6 8 a 1- 2 3.37 3 .00 2- 3 2.80 3 .20 3- 4 2.52 2.29 4- 5 2.55 2.46 5 - 6 2 . 3 6 a 2 . 2 5 a Hatch-6 2.56 2.48 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . TABLE XXV PERCENTAGE SUMS OF SQUARES FROM THE ANALYSES OF VARIANCE OF FEMALE BODY WEIGHTS AT WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 1 S t a t i s t i c a l Model i i i i i i i Source of Variance df Hatch Week 1 Time of Weighing Week 2 Week 3 Week 4 Week 5 Week 6 Sires (S) 2 6.21 13.47** 14 .31** 25.28** 31 . 9 3 * * 3 6 . 5 2 * * 3 9 . 3 9 * * Dams (D) 2 51.79** 6 3 . 2 3 * * 60 .11** 6 2 . 2 7 * * 5 5 . 3 0 * * 51.11** 4 9 . 4 1 * * Rations (R) 1 0 .39 1.67* 11.62** 0.04 2.10** 3 . 4 1 * * 3 . 9 6 * * S x D 4 8 .52 12.91** 9 . 6 5 * * 8 . 6 3 * * 6.06** 4 . 9 2 * * 3 . 3 3 * * S x R 2 1.35 0.02 0.44 0.56 0.73 1.10* 0.62 D x R 2 1.30 0.13 0.10 0.10 0.03 0.10 0 . 0 0 S x D x R 4 1.31 3.00 0.92 1.05 0.67 0.72 0.53 Residual 18 29.12 5.56 2.83 2.07 3.19 2.12 2.75 * S i g n i f i c a n t at .05 probability ** S i g n i f i c a n t at .01 probability 9 6 TABLE XXVI EFFECT OF SIRE LINE ON BODY WEIGHTS OF FEMALE CHICKS AT WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 1 Mean Body Weights of Chicks (Grams) Sire Line Time of Weighing WL NH WR Hatch 4 2 . 9 a 4 2 . 3 a 4 2 . 0 a 1 Week 6 7 . 6 a 6 6 . 2 a 7 0 . 9 2 Weeks 1 2 6 . 9 1 3 0 . 8 1 4 0 . 4 3 Weeks 2 0 5 . 0 2 2 3 . 0 2 3 8 . 0 4 Weeks 2 7 8 . 9 3 1 8 . 1 3 4 0 . 6 5 Weeks 3 7 3 . 5 4 4 3 . 1 4 7 4 . 7 6 Weeks 4 7 8 . 2 5 7 3 . 9 6 1 9 . 0 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at . 0 5 p r o b a b i l i t y . 97 EFFECT OF DAM LINE ON BODY WEIGHTS OF FEMALE CHICKS AT WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 1 TABLE XXVII  INTERVMean Body Weights of Chicks (Grams) Dam Line Time of Weighing WL NH WR Hatch 42.0a 41.5a 43.8-1 Week 64.9a 65.5a 74.3 2 Weeks 122.3 126.8 149.0 3 Weeks 202.1 212.5 251.3 4 Weeks 277.3 302.6 357.7 5 Weeks 375.1 420.0 496.2 6 Weeks 480.0 550.4 640.7 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . 98 TABLE XXVIII EFFECT OF RATION ON BODY WEIGHTS OF FEMALE CHICKS AT WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 1 Time of Weighing Hatch 1 Week 2 Weeks 3 Weeks 4 Weeks 5 Weeks 6 Weeks Mean Body Weight of Chicks (Grams) Rations B r o i l e r Starter 42.'5C 68.9 137.8 222.5£ 319.1 443.3 575.6 4 2 . 3 a 67.5 127.6 2 2 1 . 5 a 306.0 417.5 538.4 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . TABLE XXIX EFFECTS OF THE SIRE X DAM INTERACTION ON WEEKLY BODY WEIGHTS OF FEMALE CHICKS: EXPERIMENT 1 Mean Body Weights (Grams) Sire Line WL NH WR Dam Line WL -NH WR WL NH WR WL NH WR Time of Weighing (Weeks) Hatch 4 1 . 9 a 4 2 . 7 a b 4 4 . 0 b 4 2 . 2 a b 4 1 . 2 a , ' 4 3 . 6 b 4 1 . 9 a 4 0 . 5 a 43 .7 1 61 .9 67.2 73.7 65 .8 60.0 72.7 6 7 . 0 a 6 9 . 4 a 76.4 2 110.0 126.9 143.8 127.1 116.9 148.2 129.6 136.7 154.9 3 176.1 205.7 233.1 212.8 198.8 257.5 217.6 233.0 263.3 4 229.5 280.0 327.1 2 9 5 . 4 a 288 .5 a 370.5 307.1 339.2 375.4 5 302.4 377.5 440.5 4 0 3 . 9 a 4 0 3 . 4 a 522.1 419.0 478.8 526.2 6 389.3 488.1 557.1 5 1 4 . 3 a 5 3 3 . 5 a 674.0 536.3 629.7 690.9 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 probability. TABLE XXX PERCENTAGE SUMS OF SQUARES FROM THE ANALYSES OF VARIANCE OF WEEKLY AND AVERAGE GROWTH RATES OF FEMALE CHICKS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 1 S t a t i s t i c a l Model 3 3 3 3 3 3 3 3 Source of Variance df Hatch-1 1-2 Period 2-3 of Growth 3-4 (Weeks) 4-5 5-6 Sires (S) 2 25.83** 17.49* 23.28** 29.94** 42.59** 8.54 53.62** Dams (D) 2 36.54** 20.96** 2.64 18.29** 17.88** 16 .42 34.74** Rations (R) 1 1.33 24.54** 53 .09** 17.11** 7.$5* 3.87 3.86** S x D 4 16.60** 3.04 1.23 7.13 1.33 11.04 1 .91 S x R 2 0.19 1.14 1.81 0.89 3.17 8.52 0.31 D x R 2 0.25 2.05 0.33 1.21 0.89 5.38 0.03 S x D x R 4 4.28 1.94 0.62 2.06 8.55 2.72 1.71 Residual 18 14.99 28.85 17.01 23.38 17.74 43.51 3.81 * S i g n i f i c a n t at .05 probability ** S i g n i f i c a n t at .01 probability 101 TABLE XXXI EFFECT OF SIRE LINE ON GROWTH RATES OF FEMALE CHICKS DURING WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 1 Mean Growth Rates Sire Lines Growth Intervals (Weeks) WL NH WR Hatch-1 1 . 5 6 a 1 . 5 4 a 1.80 1- 2 2.80 3 . 0 4 a 3 . 0 4 a 2- 3 2.63 2.93 a 2.90 a 3 - 4 1.97 2 . 2 9 a 2 . 3 2 a 4 - 5 2.17 2 . 4 7 a 2.48 a 5- 6 2 . 1 1 a 2 . 2 0 a 2 . 2 5 a HatchT^ 2.21 2.41 2.47 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . 102 TABLE XXXII EFFECT OF DAM LINE ON GROWTH RATES OF FEMALE CHICKS DURING WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 1 Mean Growth Rates Dam Lines Growth Intervals (Weeks) WL Nil WR Hatch-1 1.50 a 1.57 a 1.83 1- 2 2.82 a 2.95 a b 3 . 1 2 b 2- 3 2.76 a 2.84 a 2.87 a 3- 4 2.01 2.28 a 2.28 a 4- 5 2 .25 2.44 a 2.44 a 5- 6 2.10 a 2 . 2 9 b 2 . l 6 a Hafcch36 2.24 2.40 2.45 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . 103 TABLE XXXIII EFFECT OF RATION ON GROWTH RATES OF FEMALE CHICKS DURING WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 1 Mean Growth Rates Rations Growth Intervals (Weeks) B r o i l e r Starter Hatch-1 1.66 a 1 . 6 l a x - 2 3.09 2.83 2"3 2.62 3.02 3- 4 2.31 2.07 4- 5 2.44 2.31 5- 6 2.22 a 2.14 a Hatchr6 2.39 2.33 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . TABLE XXXIV SIMPLE CORRELATIONS OF PRE AND POST STORAGE EGG WEIGHTS AND DATE OF LAY WITH EMBRYO WEIGHTS AND DATE OF LAY AT TWO DAY INTERVALS BETWEEN 6 AND 18 DAYS OF INCUBATION: EXPERIMENT 1 Days of Incubation No. of Viable Pre Stora Egg Wt. Post Storage Egg Wt. Date of l a y 6 8 * 10 1 12 14 16 18 112 116 123 131 114 127 115 Embryo Weight Date of lay Embryo Weight Date ?f lay Embryo Weight Date of lay Embryo height Date of laj Embryo Weight Date of lay Embryo Weight Date of lay Embryo Weight Date of lay .172 .251** .743** .021 .116 .068 .117 .600** .057 .168 .170 .242** .677** .095 .193* .123 .178* .542** .015 .120 .275** .319** .579** .072 .162 .331** .364** . 4 9 9 * * .182* .258* .412** U61** .479** .016 .111 S i g n i f i c a n t at .05 probability S i g n i f i c a n t at .01 probability o 105 TABLE XXXV CORRELATION COEFFICIENTS OF HATCHING TIME, STORAGE PERIOD AND PRE- AND POST-STORAGE EGG WEIGHTS WITH CHICK BODY WEIGHTS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 1 Weekly Body Time of Storage Pre-storage Post-storage Weights Hatch Period Egg Weight Egg Weight Hatch .146** .013 .855** .847** 1 -.269** -.207** .443** .466** 2 - . 2 9 0 * * -.218** .292** .318** 3 -.284** -.172** .223** .241** 4 -.270** -.154** .172** .187** 5 - . 2 5 3 * * - . 1 2 3 * * .144** .155** 6 -.241** -.111 .122** .134** Degrees of freedom = 790 ** P r o b a b i l i t y less than .01 106 TABLE XXXVI CORRELATION COEFFICIENTS OF HATCHING TIME, DATE OF LAY, PRE- AND POST-STORAGE EGG WEIGHTS AND 6 WEEK BODY WEIGHT WITH WEEKLY GROWTH RATES BETWEEN HATCH AND 6 WEEKS OF AGE: EXPERIMENT 1 Weekly Storage Growth Time of Period Rates Hatch (Weeks) Hatch-1 - . 3 9 1 * * - . 2 1 4 * * 1-2 -.134** -.092* 2- 3 3- 4 4- 5 5- 6 -.024 -.064 -.017 .037 .078* -.016 .085* .043 6 Week Pre-Storage Post Storage Body Egg Weight Egg Weight Weight -.076* -.150** -.109** -.078* -.069 -.091 -.045 -.136** -.123** -.079* -.083* -.084* .480** .606** .306** .480** .371** .176** Degrees of freedom = 790 * Pr o b a b i l i t y less than .05 ** Probab i l i t y l e s s than .01 107 TABLE XXXVII CORRELATION COEFFICIENTS OF 6 WEEK BODY WEIGHT WITH EMBRYO WEIGHTS, EMBRYO GROWTH RATES, CHICK WEIGHTS AND CHICK GROWTH RATES WITHIN EACH SEX AND RATION. CALCULATIONS BASED ON GENOTYPIC AVERAGES: EXPERIMENT 1 Embryo Weight (Days of • Incubation) Time of Weighing 6 8 10 12 Chick Weight (Weeks) Embryo Growth Rate (Days of Incubation) 18 . Hatch 1 2 3 4 5 6 I n t e r v a l s 6-8 8-10 10-12 12-14 14-16 16-18 6 Week Body Weight Males Females B r o i l e r R a t ion .294 - . 0 7 3 .160 .657 .743* .305 .594 .464 .628 . 8 3 2 * * .972** . 9 8 9 * * .997** 1.000 S t a r t e r Ration .342 -.211 .073 .676* .831** .431 .604 .439 .697* .887** . 9 4 9 * * . 9 8 9 * * .996** 1.000 B r o i l e r R a t ion .342 - . 0 2 5 .168 .736* .839** .331 .638 I-.072 . 711* .864** .937** .984** .996** 1 .000 S t a r t e r R a tion .336 -.108 .194 .752* . 8 2 8 * * .407 .593 .520 .785* .910** .956** . 9 8 4 * * .994** 1.000 - . 2 6 5 -.402 - . 2 5 8 - .314 .328 .373 .273 *404 .251 .353 .286 , .273 . .133 .226 .157 .128 - . 4 6 5 -. '469 - . 5 2 8 - . 4 7 9 .180 .099 .190 .108 * S i g n i f i c a n t at ** S i g n i f i c a n t a t .05 p r o b a b i l i t y .01 p r o b a b i l i t y TABLE XXXVII (continued) 108 6 Week Body Weight Males Females I n t e r v a l s Averaged Embryo Growth Rates (Days of Incubation) Chick Growth Rate (Weeks) Average Chick Growth Rate (Weeks) 6-10 6-12 6-14 6-16 6-18 8-12 8-14 8-16 8-18 Hatch - 1 1- 2 2- 3 3 - 4 4 - 5 5- 6 Hatch - 6 B r o i l e r S t a r t e r B r o i l e r S t a r t e r R a t i o n R a t i o n Ration Ration .011 - . 101 - . 0 3 6 .013 .298 .326 .306 .335 .332 .413 .352 .360 - . 2 9 7 - . 152 - . 3 7 9 .267 - . 015 - .011 - . 0 5 4 - . 0 6 9 .507 .648 .505 .583 .404 .542 .414 .452 .035 .201 - .011 .082 .200 .298 .155 .182 .578 .721* .830** .766* .934** .931** .922** . .906** .784* .792* .782* .772* .800** .637 .$16** .804** .761* .789* .835** .793* .06$ .455 - . 103 .598 . 9 5 0 * * .919** .953** .944** * S i g n i f i c a n t at .05 p r o b a b i l i t y ** S i g n i f i c a n t at .01 p r o b a b i l i t y 109 i TABLE XXXVIII CORRELATION COEFFICIENTS OF HATCH TO 6 WEEK AVERAGE GROWTH RATE WITH EMBRYO GROWTH RATES WITHIN EACH SEX AND RATION: EXPERIMENT 1 Intervals Growth Rate Hatch to 6 Weeks Male s B r o i l e r Ration Starter Ration Females Br o i l e r Ration Starter Ration Embryo Growth Rates (Days of Incubation) Averaged Embryo Growth Rates (Days of Incubation) 6-8 -.084 -.154 - . 0 9 3 -.565 8-10 .249 .422 .202 .214 10-12 .079 .104 .149 .551 12-14 .023 -.000 .057 .219 14-16 -.412 -.385 -.488 -.121 16-18 .229 .200 .276 -.296 6-10 .121 .189 .073 -.396 6-12 .206 .299 .244 .286 6-14 .,185 .253 .239 .374 6-16 -.475 - . 2 9 7 -.517 .470 6-18 -.063 .009 -.455 -.332 8-12 .246 .413 .306 .751 8-14 .189 .278 .234 .607 8-16 -.175 -.039 -.192 .619 8-18 .257 .143 .046 .377 TABLE XXXIX PERCENTAGE SUMS OF SQUARES FROM THE ANALYSES OF VARIANCE OF EMBRYO WEIGHTS AT TWO DAY INTERVALS FROM 6 TO 18 DAYS OF INCUBATION: EXPERIMENT 2 S t a t i s t i c a l Model g d g g d d d d d Source of Variance df df 6 8 Days i 10 3 f Incubation 12 14 16 18 Sex 1 # # 2.10** 1.85** 0.71 0.86 0.53 Storage Period 2 2 77.7k** 69.66** 59.38** 47.97** 56.82** 34.67** 49.07** Sire 2 2 0.27 3.22* 3.78** 3.59* 1.44 2.95 5.74** Dam 5 5 3.96 9.09** 6.28** 5.97* 14.81** 4.71 3.41 Sire x Dam 10 10 6.78 8.19* 6.46* 7.60* 2.44 8.13 13.20** Residual 34 87 11.24 9.84 21.99 33.02 23.78 48.68 28.04 Not Measured S i g n i f i c a n t at .05 probability * S i g n i f i c a n t at .01 pr o b a b i l i t y I l l TABLE :,XL. EFFECT OF DURATION OF PREINCUBATION EGG STORAGE ON EMBRYO WEIGHTS RECORDED AT TWO DAY INTERVALS FROM 6 TO 18 DAYS OF INCUBATION: EXPERIMENT 2 Mean Embryo Weights (Grams) Duration of Storage (Weeks) Days of Incubation 1 2 3_ 6 8 10 12 .429 1.203 2.867 5.991 .333 1.082 2.560 5.457 .239 .931 2.213 4.764 14 12.057 16 18.797 18 27.084 11.141 9.581 17.974 16.490 24.843 22.819 Those means w i t h i n the same row which c a r r y the same s u p e r s c r i p t are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . 1 1 2 TABLE :-XLI... EFFECT OF SIRE LINE ON EMBRYO WEIGHTS RECORDED AT TWO DAY INTERVALS FROM 6 TO 18 DAYS OF INCUBATION: EXPERIMENT 2 Mean Embryo Weights (Grams) Sire Line Days of Incubation WL Nil WR 6 .328 a .339 a .335 a 8 1.063 a 1.105 1.048a 10 2.451 2.591 a 2.597a 12 5 . 2 I I 5.480a 5 . 5 2 0 a 14 1 0 . 6 9 8 a 11.063 a 1 1 . 0 1 9 a 16 17.369 a 18.018 17.873 a 18 24.073 25.325 a 25.348 a Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y s i f f e r e n t at .05 p r o b a b i l i t y . 113 EFFECT OF DAM LINE ON EMBRYO WEIGHTS RECORDED AT TWO DAY INTERVALS FROM 6 TO 18 DAYS OF INCUBATION: EXPERIMENT 2 TABLE XLII. .: Mean Embryo Weights (Grams) Dam Line Days of Incubation WL NH WR WLxNH WLxWR NHxWR 6 ,306 a .327 a b .321 a b .344b .349 b .356b 8 .999 1.067a 1.106ab 1.057a 1.126b 1.076ab 10 2.370 2.530a 2.577a 2.564a 2.589a 2.651a 12 5.098a 5.425 a b c 5.666c 5.293ab 5.423ae 5.517bc 14 9.915 11 . 0 6 3 a b c 11.560c 10.928 a b 10.761a 11.331 b c 16 17.336a 18.195a 17.945a 17.433a 17.468a 18.143a 18 24.687ab 24.792ab 25.667b 24.221a 24.834ab 25.292ab Those means within the same row which carry the same superscript are not significantly different at .05 probability. 114 TABLE - X L i l i : „ EFFECT OF SEX ON EMBRYO WEIGHTS RECORDED AT TWO DAY INTERVALS FROM 10 TO 18* DAYS OF INCUBATION: EXPERIMENT 2 Mean Embryo Weights (Grams) Days of Incubation Males Females 10 2 .597 : ! 2.496' 12 5.503 5.305 14 11.041 a 10.813 a 16 17 . 9 0 3 a 17.604 a 18 25 . 0 9 5 a 24.736 a Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . TABLE .XLIV .' PERCENTAGE SUMS OF SQUARES FROM THE ANALYSES OF VARIANCE OF EMBRYO GROWTH RATES DURING SUCCESSIVE TWO DAY INTERVALS BETWEEN 6 AND 18 DAYS OF INCUBATION: EXPERIMENT 2 S t a t i s t i c a l Model h e h e e e e e Source of Variance df df 6-8 Intervals (Days 8-10 10-12 of Incubation) 12-14 14-16 16-18 Sex 1 # 3.94* 0.04 0.65 0.00 0.02 Storage Period 2 2 48.87** 0.12 1.94 0.48 14.12** 4.17 Sire 2 2 0.49 9.68** 0.03 1.56 0.04 0.68 Dam 5 5 2.32 4.79 4.09 5.54 11.38* 3.50 Sire x Dam 10 10 19.62* 18.70* 8.48 8.76 * 6.37 12.12 Residual 34 87 28.69 62.77 85.42 83.01 68.09 79.52 Not Measured Si g n i f i c a n t at> .05 probability S i g n i f i c a n t at .01 probability 116 TABLE :XLV- • EFFECT OF DURATION OF PREINCUBATION EGG STORAGE ON EMBRYO GROWTH RATES DURING SUCCESSIVE TWO DAY INTERVALS FROM 6 TO 18 DAYS OF INCUBATION: EXPERIMENT 2 Mean Embryo Growth Rates Duration of Storage Period (Weeks) Incubation Intervals (Days) m 1 2 3_ 6-8 3.60 4.11 4.75 8-10 3.89a 3.85a 3.87a 10-12 4.02a 4.l6 a 4.20a 12-14 4.56a 4.64a 4.53a 14-16 3.33a 3.59a 4.07 16-18 3.11a 2.73a 2.78a Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . 117 TABLE :XLVI ~, EFFECT OF SIRE LINE ON EMBRYO GROWTH RATES DURING SUCCESSIVE TWO DAY INTERVALS FROM 6 TO 18 DAYS OF INCUBATION: EXPERIMENT 2 Mean Embryo Growth Rates Sire Lines Incubation Intervals (Days) WL NH WR 6-8 4.20a 4.17a 4.09a 8-10 3.74a 3 . 8 l a 4.06 10-12 4.14a 4.12a 4.13 a 12-14 4.65a 4.57a 4.47a 14-16 3.64a 3.68a 3.66a 16-18 2.79a 2.87a 2.96a Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . 118 TABLE -ZLVII EFFECT OF DAM LINE ON EMBRYO GROWTH RATES DURING SUCCESSIVE TWO DAY INTERVALS FROM 6 TO 18 DAYS OF INCUBATION: EXPERIMENT 2 Mean Embryo Growth Rates Incubation Dam Lines (Days) WL NH WR WLxNH WLxWR NHxWR 6-8 4 .20 a 4 . l 8 a 4 .33 a 4 . 0 4 a 4 . 15 a 4 . 03 a 8-10 3 . 8 7 a b 3 . 8 8 a b 3 . 7 9 a b 3 . 9 4 a b 3 . 72 a 4 .03 b 10-12 4 .22 a 4 . l 6 a 4 . 3 1 a 4 . 00 a 4 . 0 4 a 4 . 0 4 b 12-14 4 .30 a 4 . 67 a 4 . 66 a 4 . 72 a 4 .42 a 4 . 6 7 a 14-16 4 .20 a 3 . 7 5 a b 3 . 3 1 b 3 . 5 3 b 3 .67 b 3 . 53 b 16-18 3 .00 a 2 . 6 l a 3 . 0 3 a 2 .76 a 3 . 0 2 a 2 .82 a Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . TABLE .XLVIII; PERCENTAGE SUMS OF SQUARES FROM THE ANALYSES OF VARIANCE OF EMBRYO GROWTH RATES WHEN AVERAGED FOR INTERVALS BEGINNING AT 6 OR 8 DAYS OF INCUBATION: EXPERIMENT 2 S t a ^ i f t f c a l f f f f f f f f f f Model Intervals (Days of Incubation) Source of Variance df 6-10 6-12 6-14 6-16 6-18 8-12 8-14 8-16 8-18 Storage Period 2 4 2 . 3 0 * * 39.98** 37 .87** 55 .89** 4 8 . 0 7 * * 1.45 1.73 22.21** 11.82** Sire 2 1.64 1.10 0.26 0.08 0.61 5 .75* 1.43 0.71 3.12 Dam 5 1.28 4.45 7.76* 5 .49** 7.41** 4 .46 1 4 . 6 3 * * 10.36** 10.47* Sire x Dam 10 12.79 10.47* 10.76* 11.02** 7.33 12.76 9.58 15 .96** 17.49** Residual 88 41.99 44.00 43.35 27.52 36.5$ 75.59 72.57 50.75 57.10 * S i g n i f i c a n t at .05 probability ** S i g n i f i c a n t a t .01 probability 1 2 0 TABLE XLJX . EFFECT OF EGG STORAGE ON AVERAGED TWO DAY EMBRYO GROWTH RATES: EXPERIMENT 2 Mean Averaged Embryo Growth Rates Storage Period (Weeks) Range of Intervals Averaged (Days) 1 2 3 6 - 1 0 3 . 7 5 3 . 9 8 4 . 3 1 6 - 1 2 3 . 8 4 4 . 0 4 4 . 2 8 6 - 1 4 4 . 0 9 4 . 1 9 4 . 3 4 6 - 1 6 3 . 8 8 4 . 0 7 4 . 2 9 6 - 1 8 3 . 7 5 3 . 8 5 4 . 0 4 8 - 1 2 3 . 9 6 a . 4 . 0 1 a 4 . 0 9 A 8 - 1 4 4 . l 6 a 4 . 2 2 a 4 . 2 0 a 8 - 1 6 3 . 9 5 4 . 0 6 4 . 1 7 8 - 1 8 3 . 7 8 a 3 . 7 9 a 3 . 8 9 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . 121 TABLE L EFFECT OF SIRE LINE ON AVERAGED TWO DAY EMBRYO GROWTH RATES: EXPERIMENT 2 Mean Averaged Embryo Growth Rates Sire Line Range of Intervals Averaged (Days) WL NH WR 6-10. 3 . 9 7 a 3.99 a 4.08 a 6-12 4.03 a 4.03 a 4.09 a 6-14 4 . 1 9 a 4.17 a 4.19 a 6-16 4.08 a 4.07 a 4.08 a 6-18 3.87 a 3.87 a 3 . 9 0 a 8-12 3.94a 3.96 a 4.10 8-14 4.19 a 4.17 a 4.22a 8-16 4 . 0 5 a 4.05 a 4.08 a 8-18 3.80 a 3 . 8 l a 3.86a Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . 122 TABLE LI EFFECT OF DAM LINE ON AVERAGED WO DAY EMBRYO GROWTH RATES: EXPERIMENT 2 Mean Averaged Embryo Growth Rates Dam Line Range of Intervals Averaged (Days) WL NH WR WLxNH WLxWR NHxWR 6-10 4.03a 4.08a 4.06a 3.99a 3.94a 4.03a 6-12 4.10a 4.07a 4.15 3 . 9 9 a 3.97a 4 . 0 3 a 6-14 4.15 a b 4.22bc 4 .27° 4 . 1 7 a b c 4.08a 4 . l 9 a b c 6-16 4.l6 b 4.13 b c 4.08 a b c 4.05 a c 4.00a 4.06 a c 6-18 3.96b 3.87a 3.91 a b 3.83a 3.84a 3.85a 8-12 4.05a 4.02a 4.05a 3.97a 3.88a 4.04a 8-14 4.13 a b 4.24 a c 4.25a 4.22a 4.06b 4.25a 8-16 4.18c 4.11 b c 4.02 a b 4.05 a b 3.96a 4.07 a b 8-18 3.92 3.81a 3.82a 3.79a 3.77a 3.81a Those means within the same row which carry the same are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . superscript TABLE LII PERCENTAGE SUMS OF SQUARES FROM THE ANALYSES OF VARIANCE OF MALE BODY WEIGHTS AT WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 2 S t a t i s t i c a l Model i i i i i i i Source of Variance df Hatch Week 1 Time of Weighing Week 2 Week 3 Week 4 Week 5 Week 6 S i r e s (S) 2 6.87 30.45** 25.34** 30.97** 36.24** 40.17** 42.31** Dams (D) 5 21.17* 28.84** 19.77** 18.36** 20.78** 22.35** 26.26** Rations (R) 1 0.19 7.71** 26.79** 28.21** 21.37** 17.83** 16.61** S x D 10 12.93 14.18** 10 .91** 9.62** 8.89** 7.25** 5.77** S x R 2 0.87 0.41 0.50 0.28 0.42 0.52 0.74 D x R 5 3.85 5.61** 4.76* 3.82** 3 .25* 2.93* 1.95 S x D x R 10 10.65 1 .61 1.68 1.26 0.82 0.73 0.41 Residual 36 43.48 11.20 10.26 7.48 8.23 8.22 5.96 * S i g n i f i c a n t a t .05 probability ** S i g n i f i c a n t at .01 p r o b a b i l i t y 124 TABLE L I U EFFECT OF SIRE LINE ON BODY WEIGHTS OF MALE CHICKS AT WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 2 Mean Body Weights of Chicks (Grams) Sire Lines Time of Weighing WL NH WR Hatch 41.8a 41.8a 42.7 1 Week 7 9 .O a 78.5a 85.7 2 Weeks 148.l a 151.1a 167.1 3 Weeks 240.1 255.4 283.6 4 Weeks 348.1 377.5 419.9 5 Weeks 472.1 519.4 579.6 6 Weeks 614.3 683.7 761.3 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at . 0 5 p r o b a b i l i t y . 125 TABLE LV EFFECT OF DAM LINE ON BODY WEIGHTS OF MALE CHICKS AT WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 2 Mean Body Weights of Chicks (Grams) Dam Lines Time of Weighing WL NH WR WLxNH WLxWR NHxWR Hatch 4 1 . 5 a b 43 .2° 4 2 . 2 a b c 4 1 .0 a 4 2 . 0 a b c 4 2 . 6 b c 1 Week 7 7 . 7 a 80.9 b 8 6 . 6 7 7 . 0 a 81.9 b 82.4 b 2 Weeks 1 4 9 . 0 a b 154.5 b c 168.6 1 4 5 . 4 a 1 5 7 . 1 ° 158.0 C 3 Weeks 2 4 5 . 4 a 2 5 9 . 9 b 285.2 2 4 3 . 7 a 2 5 8 . 2 b 2 6 5 . 9 b 4 Weeks 3 5 6 . 3 a 3 8 2 . 2 ° 423.3 3 6 0 . l a b 3 7 6 . 6 b c 392.5° 5 Weeks 4 8 3 . 5 a 5 2 4 . 3 c d 581.3 4 9 3 . l a b 5 1 3 . 9 b c 5 4 6 . 0 d 6 Weeks 6 2 2 . 2 a 6 9 1 . 4 b 765.9 6 4 6 . 0 a 6 7 2 . 8 b 720.2 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . 126 TABLE LVI EFFECT OF RATION ON BODY WEIGHTS OF MALE CHICKS AT WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 2 Mean Body Weight of Chicks (Grams) Rations Time of Weighing B r o i l e r Starter Hatch 4 2 . 2 a 4 2 .O a 1 Week 82 .8 79.5 2 Weeks 164.0 146.9 3 Weeks 276.9 242.5 4 Weeks 404.5 359.2 5 Weeks 553.0 494.4 6 Weeks 724.0 648.8 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . TABLE LVII PERCENTAGE SUMS OF SQUARES FROM THE ANALYSES OF VARIANCE OF WEEKLY AND AVERAGE GROWTH RATES OF MALE CHICKS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 2 S t a t i s t i c a l 3 3 3 j Period 3 (Weeks) 3 3 Model 3 of Growth Source of Variance df Hatch-1 1-2 2-3 3-4 4-5 5-6 Hatonv6 Sires (S) 2 21.97** 9 .55** 34.18** 14.56** 15.62** 7.85* 44.83** Dams (D) 5 25.24** 3.18 11.00* 11.13* 16.28** 16.61* 25.77** Rations (R) 1 7.76** 47.02** 9.01** 10.04** 3.18* 0.67 9.81** S x D 10 14.67* 9.91 11.22 14.65 18.36 12.57 5.03 S x R 2 0.83 2.59 1.17 3.16 0.97 1.63 0.65 D x R 5 4.77 1.90 5.19 3.83 3.90 6.90 0.51 S x D x R 10 1.92 3.37 3.56 10.67 11.09 11.21 1.65 Residual 36 22.84 22.48 24.67 31.96 30.60 42.56 11.74 * S i g n i f i c a n t at .05 probability ** S i g n i f i c a n t at .01 p r o b a b i l i t y 1 2 $ TABLE L V I I I EFFECT OF SIRE LINE ON GROWTH RATES OF MALE CHICKS DURING WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 2 Mean Growth Rates Sire Lines Growth Intervals (Weeks) WL NH WR Hatch-1 2.20 a 2.19 a 2.42 1- 2 2.79 2.91 a 2.97 a 2- 3 2.64 2.87 a 2.91 a 3- 4 2.41 2.53 a 2.55 a 4- 5 2.2$ 2.39 a 2.41 a 5- 6 2.24 2.34 a 2.32 a Hatch-6 2.43 2.54 2.60 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . 129 TABLE LIX EFFECT OF DAM LINE ON GROWTH RATES OF MALE CHICKS DURING WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 2 Mean Growth Rates Dam Lines Growth Intervals (Weeks) WL NH WR WLxNH WLxWR NHxWR Hatch-1 2 . l 6 a 2.17 a b 2.49 2 . l 8 a b 2.31 b 2.30 a 1- 2 2.89 a 2.89 a 2.97 a 2.82 a 2.89 a 2.89 a 2- 3 2.72a 2.85 b 2.88 b 2 . 8 l a b 2.71 a 2.86 b 3- 4 2.41 a 2.49 a b 2.57 b 2.53 a b 2.44 a b 2.53 a 4- 5 2.28 a 2.37 a 2.38 a b 2.35 a 2.33 a 2.47 b 5- 6 2.16 2.35 a 2.34 a 2.30 a 2.30 a 2.36 a Hatch=6 2.44 2.52 a 2.60 2.50 a 2.50 a 2.57 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 pr o b a b i l i t y . 130 TABLE LX EFFECT OF RATION ON GROWTH RATES OF MALE CHICKS DURING WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 2 Mean Growth Rates Rations Growth Intervals (Weeks) B r o i l e r Starter Hatch-1 2.33 2.21 1- 2 3 .05 2.73 2- 3 2.87 2.75 3 - 4 2.44 2.55 4 - 5 2.33 2.39 5- 6 2 . 2 9 a 2 . 3 1 a Hatchs6 2.55 2.49 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . TABLE LXI PERCENTAGE SUMS OF SQUARES FROM THE ANALYSES OF VARIANCE OF FEMALE BODY WEIGHTS AT WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 2 S t a t i s t i c a l Model i i i i i i i Source of Variance df Hatch Week 1 Time of Weighing Week 2 Week 3 Week 4 Week 5 Week 6 Sires (S) 2 5 .96 16.36** 17.23** 22.62** 29.68** 31.22** 37.14** Dams (D) 5 7.73 28.43** 17.14** 19.10** 22.28** 27.73** 2 9 . 9 2 * * Rations (R) 1 2.59 11.07** 3 2 . 3 2 * * 34.78** 28.47** 23.42** f 18.43** S x D 10 22.11* 27.42** 20 .09** 13.81** ,12.07** 9.37** 6 . 9 0 * * S x R 2 6.11 0.25 0.48 0.44 0 .14 0.46 0.29 D x R 5 4.88 1.43 0.96 0.75 0.21 0 . 2 4 0.60 S x D x R 10 16.37 3.72 3.05 1.52 1.41 1.49 1.65 Residual 36 34.24 11.31 8.74 6.99 5.75 6.06 5.07 * S i g n i f i c a n t at .05 probability ** S i g n i f i c a n t at .01 probability 132 TABLE LXII EFFECT OF SIRE LINE ON BODY WEIGHTS OF FEMALE CHICKS AT WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 2 Mean Body Weights of Chicks (Grams) Sire Line Time of Weighing WL NH WR Hatch 41.6 a 41.4 a 4 2 . 3 a 1 Week 77.5 75.3 81.0 2 Weeks 1 4 2 . l a 1 4 0 . 6 a 154.9 3 Weeks 226.1 233.4 258.1 4 Weeks 319.5 33$.9 374.9 5 Weeks 422.2 457.3 502.7 6 Weeks 53$.6 593.7 656.0 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . 133 TABLE LXIII EFFECT OF DAM LINE ON BODY WEIGHTS OF FEMALE CHICKS AT WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 2 Mean Body Weights of Chicks (Grams) Dam Line Time of Weighing WL NH WR WLxNH WLxWR NHxWR Hatch 41.0a 42.2b 4 2 . 1 ^ 41.5 a b 4 l . 9 a b 42.0 a l 1 Week 74.4a 76.9b 84.2 75.9 a b 77.7b 78.4b 2 Weeks 1 3 9 .0 a 144.4 a b 158.5 140.0a 146.3b 147.2b 3 Weeks 224.4a 237.3b 262.9 2 2 7 .6 a 238.$b 244.3b 4 Weeks 319.4a 3 4 2 .3 b 380.6 326.6a 3 4 2 .7 b 355.2b 5 Weeks 419.2a 461.l b 517.1 434.4a 458.l b 474.4b 6 Weeks 536.6 597.9a 672.0 558.5 595.2a 616.4a Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 pr o b a b i l i t y . 134 TABLE LXIV EFFECT OF RATION ON BODY WEIGHTS OF FEMALE CHICKS AT WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 2 Mean Body Weights of Chicks (Grams) Rations Time of Weighing B r o i l e r Starter Hatch 4 2 .O a 41.6 a 1 Week 7 9 . 8 7 6 . 0 2 Weeks 154.7 137.1 3 Weeks 256.2 222.3 4 Weeks 366.9 322.0 5 Weeks 489.3 432.2 6 Weeks 629.9 562.3 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . TABLE LXV PERCENTAGE SUMS OF SQUARES FROM THE ANALYSES OF VARIANCE OF WEEKLY AND AVERAGE GROWTH RATES OF FEMALE CHICKS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 2 S t a t i s t i c a l Model j 3 3 3 3 3 3 3 Source of Variance df Hatch-1 1-2 Period 2-3 of Growth 3-4 (Weeks) 4-5 .5-6 H a t c h e r 6 Sires (S) 2 10.86** 13.68** 43.45** 28.40** 15.11** 21.26** 46.96** Dams (D) 5 24.45** 2.69 10.82** 9.29 24.59** 9.79 28.15** Rations (R) 1 9.12** 56.74** 9.37** 4.96* 2.72 6.12* 8.25** S x D 10 29 .73** 7.69* 7.25 2.30 13.88 14.92 4.81* S x R 2 2.51 0.66 0.75 5.21 4.26 6.68* 0.28 D x R 5 2.08 1.33 3.37 12.11* 4.98 4.72 0.99 S x D x R 10 5.14 5.73 6.98 8.52 3.54 6.35 2.62 Residual 36 16.12 11.48 18.02 29.21 30.92 30.15 7.94 * S i g n i f i c a n t at .05 probability ** S i g n i f i c a n t at .01 probability 136 TABLE LXVI EFFECT OF SIRE LINE ON GROWTH RATES OF FEMALE CHICKS DURING WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 2 Growth Intervals (Weeks) Hatch-1 1- 2 2- 3 3 - 4 4 - 5 5- 6 Hateh=:6 Mean Growth Rates Sire Lines WL NH WR 2.15 2.69 2.53 2.24 2.09 2.08 2.30 2.07 2.78 • 2.78 a 2.42a 2.24 a 2.21 a 2.42 2.25 2.89 2.80 a 2 . 4 3 a 2 . 1 9 a 2 . 2 8 a 2.47 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . 1 3 7 TABLE LXVII EFFECT OF DAM LINE ON GROWTH RATES OF FEMALE CHICKS DURING WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 2 Mean Growth Rates Dam Lines Growth Intervals (Weeks) WL NH WR WLxNH WLxWR NHxWR Hatch-1 2.06a 2.08 a 2.40 2 . 0 9 A 2.14 a 2 . l 6 a 1- 2 2.77 a b 2.80 a b 2.83 b 2 . 7 2 A 2.83 b 2.80 a b 2- 3 2 . 6 l a 2 . 7 2 B C 2.77 c 2.65 a b 2.68 a b c 2.78c 3- 4 2.28 a 2.37 a 2 . 4 0 B 2.34 a b 2.34 a b 2.44 b 4- 5 2.04a 2 . 2 3 B C 2 . 3 0 ° 2.13 a b 2.16 b 2 . l 6 b 5- 6 2.10 a 2.22 b 2 . 2 4 B 2.13 a b 2.23 b 2.22b -Hatdhs6 2.31 a 2.40 b 2.49 2.34 a 2.40 b 2.43 b Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . 138 TABLE LXVIII EFFECT OF RATION ON GROWTH RATES OF FEMALE CHICKS DURING WEEKLY INTERVALS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 2 Mean Growth Rates Rations Growth Intervals (Weeks) B r o i l e r Starter Hatch-1 2.22 2.09 1- 2 2.96 2.62 2- 3 2.76 2.64 3 - 4 2.32 2.40 4 - 5 2 . 1 4 a 2 . 2 0 a 5- 6 2.14 2.23 Hatch-6 2.43 2.36 Those means within the same row which carry the same superscript are not s i g n i f i c a n t l y d i f f e r e n t at .05 p r o b a b i l i t y . TABLE LXIX SIMPLE CORRELATIONS OF PRE AND POST STORAGE EGG WEIGHTS AND DATE OF LAY WITH EMBRYO WEIGHTS AND DATE OF LAY AT TWO DAY INTERVALS BETWEEN 6 AND 18 DAYS OF INCUBATION: EXPERIMENT 2 Days of Incubation No. of Viable Eggs Pre Storage Egg Wt. Post Storage Egg Wt. Date of lay 6 8 10 12 14 16 18 301 272 231 230 228 237 169 Embryo Weight Date of lay Embryo Weight Date of lay Embryo Weight Date of lay Embryo height Date of lay Embryo Weight Date of lay Embryo Weight Date of lay Embryo Weight Date of lay -.112 - . 0 9 1 .699** -.098 -.063 .131* .153* .629** .118* .155* .013 .036 .682** .015 .056 .111 .134* . 591** .001 .036 .193** .223** . 619** .137* .162* .138* .163* .486** .054 .085 .333** .376** ,635** .119 .153* * S i g n i f i c a n t at .05 probability ** S i g n i f i c a n t at .01 probability 140 TABLE LXX CORRELATION COEFFICIENTS OF HATCHING TIME, STORAGE PERIOD AND PRE- AND POST-STORAGE EGG WEIGHTS WITH CHICK BODY WEIGHTS FROM HATCH TO 6 WEEKS OF AGE: EXPERIMENT 2 Weekly Body Weights Time of Hatch Storage Period Pre-storage Egg Weight Post-storage Egg Weight Hatch .038 -.118** .825** .773** 1 2 3 -.01$ -.116** - . 0 0 4 - . 0 9 $ * * ,011 -.077* .322** .232** .201** .313** .234** .216** 4 5 6 ,013 -.060* .032 -.059 ,041 -.051 .190** .16$* .15$** .19$** .175** .16$** Degrees of freedom = 120$ * S i g n i f i c a n t a t .05 p r o b a b i l i t y ** S i g n i f i c a n t at .01 pr o b a b i l i t y 141 TABLE LXXI CORRELATION COEFFICIENTS OF HATCHING TIME, DATE OF LAY, PRE- AND POST-STORAGE EGG WEIGHTS AND 6 WEEK BODY WEIGHT WITH WEEKLY GROWTH RATES BETWEEN HATCH AND 6 WEEKS OF AGE: EXPERIMENT 2 Weekly Storage Growth Time of Period Rates Hatch (Weeks) Hatch-1 -.047 1- 2 2- 3 3- 4 4- 5 5- 6 .020 .045 .005 .067 .036 -.025 -.019 .033 .051 .012 .028 Pre-Storage Egg Weight -.276** -.035 -.024 -.008 -.051 -.022 Post-Storage Egg Weight - . 2 5 0 * * - .017 - .012 - . 0 3 3 - . 0 5 4 - . 0 1 0 6 Week Body Weight .456** .508** .452** .298** .276** .144** Degrees of freedom s 120$ ** S i g n i f i c a n t at .01 pr o b a b i l i t y 142 TABLE LXXII CORRELATION COEFFICIENTS OF 6 WEEK BODY WEIGHTS WITH EMBRYO WEIGHTS, EMBRYO GROWTH RATES, CHICK WEIGHTS AND CHICK GROWTH RATES WITHIN EACH SEX AND RATION. CALCULATIONS BASED ON GENOTYPIC AVERAGES: EXPERIMENT 2 6 Week Body Weight Males Females Embryo Weight (Days of Incubation) Chick Weight (Weeks) B r o i l e r Starter Broiler Starter Ration Ration Ration Ration Time of Weighing 6 .202 .071 .086 - . 0 0 0 8 .034 .025 .065 .099 10 .320 .290 .331 .380 12 .607** .597** .575* .623** 14 .716** .563* .671** .669** 16 .524* .535* .426 .468* 18 .620** .625** .595** . 567* Hatch .443 .604** .188 .537* 1 .789** .821** .751** .784** 2 .904** .873** .879** .841** 3 .955** .953** .960** .946** 4 .986** .978** .972** .984** 5 .997** .989** .793** .992** 6 1.000 1.000 1.000 1.000 Intervals 6-8 -.149 - .046 - .042 .040 Embryo Growth 8-10 .293 .272 .273 .296 Rate 10-12 .522* . 519* .467# .492* (Days of 12-14 - .226 -.318 -.215 -.283 Incubation) 14-16 - .257 -.077 - .304 -.262 16-18 - .036 -.044 .043 - .027 S i g n i f i c a n t at .05 p r o b a b i l i t y * S i g n i f i c a n t at .01 p r o b a b i l i t y Approaches significance at .05 pr o b a b i l i t y TABLE LXXII (Continued) 143 6 Week Body Weight Males Females Averaged Embryo Growth Rates (Days of Incubation) Chick Growth Rate (Weeks) Average Chick Growth Rate (Weeks) B r o i l e r Ration Starter Ration B r o i l e r Ration Starter Rati on Intervals 6-10 6-12 6-14 6-16 6-18 8-12 8-14 8-16 8-18 .100 .375 .295 .033 - . 0 5 3 ^ .496* .185 .148 .176 .441 .281 .167 .124 . 6 3 6 * * .353 .221 .178 .198 .412 .367 .055 .087 . 5 9 0 * * .436 .094 .135 .296 .506* .425 .132 .096 . 6 2 6 * * .387 .094 .063 Hatch-1 1- 2 2- 3 3 - 4 4 - 5 5- 6 .780** .812** .812** .629** .462 . 6 4 5 * * .488* . 7 0 2 * * .554* .568* .378 . 578* . 7 2 0 * * .734** . 8 6 5 * * .565* .759** .402 . 6 4 6 * * . 8 3 6 * * .517* .564* .347 .559* Hatch-6 . 8 9 9 * * . 9 0 5 * * . 9 6 0 * * .956** * S i g n i f i c a n t at .05 p r o b a b i l i t y ** S i g n i f i c a n t at .01 p r o b a b i l i t y 144 TABLE LXXIII CORRELATION COEFFICIENTS OF HATCH TO 6 WEEK AVERAGE GROWTH RATE WITH EMBRYO GROWTH RATES WITHIN EACH SEX AND RATION: EXPERIMENT 2 Growth Rate Hatch to 6 Weeks Males Females Intervals Embryo Growth Rates (Days of Incubation) Averaged Embryo Growth Rates (Days of Incubation) 6--8 8--10 10--12 12. -14 14--16 16' -18 6--10 6--12 6--14 6--16 6--18 8--12 £• -14 8--16 8--18 Bro i l e r ^ t a r t e r B r o i l e r Starter Ration Ration Ration Ration -.113 -.006 -.014 .057 .258 .233 • .231 .296 .524* .547* .408 .510* -.271 -.344 -.214 - . 2 5 9 -.354 -.165 -.336 -.327 .018 -.011 .153 .010 .141 .211 .220 .356 .388 .472* .374 .530* .255 .294 .306 . 4 9 0 * -.073 .110 -.020 .135 -.070 .092 .116 .132 . 6 3 2 * * .637** . 512* .642** .413 .318 .341 .440 .031 .117 -.012 .080 .051 .109 .139 .088 * S i g n i f i c a n t at .05 pr o b a b i l i t y ** S i g n i f i c a n t a t .01 prob a b i l i t y 145 TABLE LXXIV COEFFICIENTS OF DETERMINATION (100R2) OF THE GENOTYPIC ESTIMATES OF 6 WEEK BODY WEIGHT WITHIN EACH SiX AND RATION, MULTUPLY REGRESSED ON SELECTED "GENOTYPIC" TRAITS: EXPERIMENT 2 Males Females Regression Variables B r o i l e r Ration Starter Ration B r o i l e r . Ration Starter Rati'bn X l 80.8 81 .9 92.2 91.4 x 2 42.4 40.4 34.8 3 9 . 2 x 3 51.2 31.7 45 .0 4 4 . 8 X 4 19.6 36.5 3.5 28.8 X l X 2 91.0 91.4 $2.0 92.3 X l x 2 x 3 92.6 91.5 8 3 . 8 92.5 X l X 2 X 4 95.8 92.7 86.1 9 4 . 0 X l X 2 X 5 9$.4 98.3 92.5 96.1 X l X 2 x 3 x 4 95.8 92.8 86.4 94.2 X l X 2 x 3 X 5 98.7 98.5 94 .0 96.8 X i = 6-week Growth Rate X2 - 8-12 day Embryo Growth Rate X3 = 14-day Embryo Body Weight X/^  • Hatching Weight X5 = 1-week Body Weight 

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