UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Strain differences in embryonic and early chick growth Iton, Laurence Eric 1962

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

Item Metadata

Download

Media
831-UBC_1962_A4 I7 S7.pdf [ 3.23MB ]
Metadata
JSON: 831-1.0105701.json
JSON-LD: 831-1.0105701-ld.json
RDF/XML (Pretty): 831-1.0105701-rdf.xml
RDF/JSON: 831-1.0105701-rdf.json
Turtle: 831-1.0105701-turtle.txt
N-Triples: 831-1.0105701-rdf-ntriples.txt
Original Record: 831-1.0105701-source.json
Full Text
831-1.0105701-fulltext.txt
Citation
831-1.0105701.ris

Full Text

STRAIN DIFFERENCES IN EMBRYONIC AND EARLY CHICK GROWTH by LAURENCE ERIC ITON B.S.A., University of British Columbia, 1953 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN AGRICULTURE in the Department of Poultry Science We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA AUGUST; 1962 In presenting this thesis in p a r t i a l fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make i t freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of Poultry Science The University of British Columbia, Vancouver 8, Canada. Date August 13, 1962 i i ABSTRACT The e x t e n t t o w h i c h egg w e i g h t m o d i f i e s g e n e t i c d i f f e r e n c e s i n body-w e i g h t o f t h e embryo and c h i c k and t h e c o r r e l a t i o n between embryonic growth r a t e and p o s t - h a t c h i n g g r o w th r a t e were i n v e s t i g a t e d . T h i s was done b y s t u d y -i n g t h e r e l a t i o n s h i p s between (l) egg w e i g h t and body w e i g h t o f embryo and c h i c k ; (2) s t r a i n and body w e i g h t o f embryo and c h i c k ; (3) s t r a i n and p e r -c e n t a g e growth r a t e o f embryo and c h i c k ; and (k) t h e r e l a t i o n s h i p between em-b r y o n i c g r o w t h r a t e and p o s t - h a t c h i n g growth r a t e . T h i s s t u d y was c o n d u c t e d on f i v e s t r a i n s and one s t r a i n - c r o s s . Two o f t h e s t r a i n s were b r e d f o r meat, (White P l y m o u t h Rock and White C o r n i s h ) ; two were b r e d f o r h i g h egg p r o d u c t i o n , (White L e g h o r n s ) ; and one was an i n t e r -m e d i a t e t y p e , (White-New H a m p s h i r e ) . The s t r a i n - c r o s s was d e r i v e d f r o m m a t i n g males o f one White L e g h o r n s t r a i n w i t h f e m a l e s o f t h e o t h e r . I n d i v i d u a l egg w e i g h t s were r e c o r d e d f o r o v e r 2,200 eggs. Between n i n e and e i g h t e e n embryos o f each c a t e g o r y were we i g h e d f r o m each o f two i n c u b a t o r s f r o m t h e n i n t h t o t h e e i g h t e e n t h day o f i n c u b a t i o n . Between f i f t e e n and t h i r t y - t h r e e c h i c k s o f each c a t e g o r y were we i g h e d a t h a t c h i n g and a t w e e k l y i n t e r v a l s f o r t h r e e weeks. A n a l y s e s o f v a r i a n c e o f embryonic w e i g h t s , c h i c k w e i g h t s , and embry-o n i c o r c h i c k w e i g h t s e x p r e s s e d as p e r c e n t a g e s o f egg w e i g h t were done. A n a l -y s e s o f v a r i a n c e were a l s o done on embryonic and p o s t - h a t c h i n g g r o w th r a t e s . C o e f f i c i e n t s o f c o r r e l a t i o n ( r ) between egg w e i g h t and embryonic o r c h i c k w e i g h t and a l s o c o e f f i c i e n t s o f r e g r e s s i o n o f c h i c k w e i g h t on egg w e i g h t were computed. The c o r r e l a t i o n between embryonic and p o s t - h a t c h i n g growth r a t e s was e s t i m a t e d . i i i From the results of the above tests i t was concluded that: (l) Differences in embryonic weights among the strains were due to differences in inherent genetic factors; (2) Egg weight exerted a temporary measurable influence on embryonic and chick weight, the effect being greatest at hatch-ing; (3) Differences in post-hatching growth rate among the strains were probably due to differences in nutritional factors which contributed to a more efficient u t i l i z a t i o n of nutrients by the heavy type chicks; and (k) Approximately 65 per cent of the variation in post-hatching growth rate to three weeks of age was dependent on the variation in growth rate during the nine- to fourteen-day incubation period. The estimate of correlation bet-ween growth rate during these two periods was, however, not precise. v i i i ACKNOWLEDGEMENT The writer wishes to express his indebtedness to Mr. Herbert E l l i s who assisted in weighing and setting eggs, and extracting embryos. The writer also wishes to express apprec-iation for the assistance given by Mr. Keith Eccleston who read the manuscript and made valuable suggestions about presenta-tion of the thesis. iv INTRODUCTION REVIEW OF THE LITERATURE MATERIALS AND METHODS STATISTICAL METHODS RESULTS AND DISCUSSION CONCLUSIONS BIBLIOGRAPHY TABLE OF CONTENTS Page 1 1 7 9 13 2k 25 LIST OF TABLES Table Page 1 Mean Egg Weights in Grams 27 2 Mean Embryonic and Chick Weights in Grams 28 3a Variability of Embryonic Weights 29 3b Variability of Embryonic Weights 31 k Total Number of Embryos Extracted 33 5a Variability of Chick Weights 3^+ 5b Variability of Chick Weights 35 6a Results of Bartlett's Test of Homogeneity of Variance 36 6b Results of Bartlett's Test of Homogenity of Variance 37 7 Analyses of Variance of Embryonic and Chick Weights 38 8 Results of Duncan's New Multiple-Range Test Used On Mean Embryonic and Chick Weights in Grams 39 9 Analyses of Variance of Egg Weights 0^ 10 Embryonic and Chick Weights Expressed as Percentages of Egg Weight kl Results of Tukey's Test for Non-Additivity Analyses of Variance of Embryonic and Chick Weights Expressed as Percentages of Egg Weight Results of Duncan's New Multiple-Range Test Used On Mean Embryonic and Chick Weights Expressed as Percentages of Egg Weight Coefficients of Correlation (r) Between Egg Weight and Embryonic or Chick Weight Coefficients of Correlation (r) Between Egg Weight and Embryonic or Chick Weight Regression Coefficients : Grams of Chick Weight On Grams of Egg Weight Results of Tests for Linear Relationship Between InW and Time Equations Used to Plot Growth Curves Analyses of Variance of Growth Rates Analyses of Variance of Growth Rates v i i LIST OF FIGURES Figure Page 1 Arith-log Graphs of Growth Rate Obtained From the Equation: InW = InA + kt 52 2 Arith-log Graphs of Growth Rate Obtained From the Equation: InW = InA + kt 53 3a Arithmetic Graphs of Growth Rate 5k 3b Arithmetic Graphs of Growth Rate 55 ka Arithmetic Graphs of Growth Rate 56 kh Arithmetic Graphs of Growth Rate 57 INTRODUCTION The ultimate size of an organism is under the joint control of gen-etic and environmental factors. The study of the comparative effects of gen-etic and environmental influences has posed problems for investigators of size inheritance in many organisms. Numerous investigators have used the domestic fowl for such studies. Some have confined their attention to the influence of environmental factors such as egg weight and hereditary factors such as breed or strain on body weight. A large proportion of these investigators was interested in the economic implications of the problem e.g. the effect of hatching-egg weight on growth of the chick to fryer age. They concerned them-selves with the post-hatching period of development. Others, whose interests were more academic, studied the influence of egg weight and hereditary factors on embryonic growth. The contributions of both categories of investigators are b r i e f l y reviewed below. REVIEW OF THE LITERATURE One of the earliest reports on the influence of egg weight on chick weight was submitted by Halbersleben and Mussehl (1922). They found the av-erage weight of the chick at hatching was 6k per cent of i n i t i a l egg weight and, at thirty-five days after hatching, the chicks from small eggs were ap-proximately the same average weight as were those from large eggs. Upp (1928) found the weight of chicks at hatching to be approximately 68 per cent of egg weight. He also found that egg weight and day-old chick weight were unreliable indices of chick weight at two, four, and twelve weeks of age. 2 J a i l and Heywang (1930) l i k e w i s e c o n c l u d e d t h a t , r e g a r d l e s s o f i n i t i a l egg w e i g h t , t h e p e r c e n t a g e c h i c k w e i g h t a t h a t c h i n g t e n d s t o be c o n s t a n t . They, t o o , f o u n d t h a t c h i c k w e i g h t a t h a t c h i n g a v e r a g e d about 68 p e r c e n t o f i n i t -i a l egg w e i g h t . B y e r l y (1930) r e p o r t e d t h a t c h i c k embryos o f d i f f e r e n t b r e e d s d i f f e r e d l i t t l e i n s i z e when d e v e l o p e d i n eggs o f t h e same s i z e . L a t e r on he p o s t u l a t e d , "major d i f f e r e n c e s i n embryo s i z e among embryos o f l i k e age c o u l d be s a t i s f a c t o r i l y a c c o u n t e d f o r b y d i f f e r e n c e s i n egg s i z e " . He c o n c l u d e d w i t h o u t p r o o f t h a t t h e e f f e c t o f egg s i z e on embryo s i z e i s c e r -t a i n l y a p p a r e n t b y t h e s e v e n t h day o f i n c u b a t i o n ( B y e r l y , 1932). I n c o n t r a s t W i l e y (l950a) o b t a i n e d eggs f r o m a s t r a i n o f B a r r e d P l y m o u t h Rocks t h a t l a i d l a r g e eggs, and f r o m a n o t h e r t h a t l a i d s m a l l eggs. He s t u d i e d t h e d e v e l o p -ment o f embryos a t sev e n t y - t w o h o u r s , f o u r t e e n d a y s , and n i n e t e e n days and fo u n d no c o n s i s t e n t d i f f e r e n c e s i n w e i g h t . However, he d i d s u g g e s t t h a t space i n t h e egg s h e l l d u r i n g t h e l a s t two o r t h r e e days o f i n c u b a t i o n has a s i g n i f i -c a n t e f f e c t on c h i c k s i z e a t h a t c h i n g . W i l e y (1950b) a l s o s t u d i e d t h e e f f -e c t o f egg w e i g h t on t h e g r o w t h o f B a r r e d P l y m o u t h Rock and White Wyandotte c h i c k s . He f o u n d t h a t a h i g h c o r r e l a t i o n e x i s t e d a t h a t c h i n g . T h i s c o r -r e l a t i o n was m a r k e d l y r e d u c e d i n magnitude by t h e t h i r d week and c o n t i n u e d t o d i m i n i s h s u b s e q u e n t l y . K o s i n e t a l . (1952) s t u d i e d t h e i n f l u e n c e o f egg w e i g h t on a c t u a l body w e i g h t g a i n o f t h e c h i c k f r o m h a t c h i n g t o t w e l v e weeks o f age. They r e p o r t e d t h a t t h o u g h egg s i z e f r e q u e n t l y e x e r t e d a s i g n i f i c a n t i n f l u e n c e on c h i c k g rowth, b r e e d and sex d i f f e r e n c e s i n t h e c h i c k s caused ex-treme v a r i a t i o n s i n t h e r e l a t i o n s h i p and p r e c l u d e d g e n e r a l i z a t i o n s . However, t h e mean growth r a t e d e t e r m i n e d b y a c t u a l g a i n i n body w e i g h t o f c h i c k s f r o m l a r g e eggs was, i n g e n e r a l , s l i g h t l y g r e a t e r t h a n t h a t o f c h i c k s f r o m s m a l l eggs. Goodwin (1961) c a r r i e d on i n v e s t i g a t i o n s t o f r y e r age and s t u d i e d t h e 3 relationship between chick size at hatching and growth rate. He found that chick weight at hatching exerted an important effect on growth to fryer age. Bray and Iton (1962) studied the effect of egg weight on embryonic and post-hatching weight of five strains of fowl from the sixth day of incubation to eight weeks after hatching. They ranked the strains on the basis of embry-onic weight and determined the correlation between these ranks and rankings of the parents' body weights and egg weights. They observed that the ranks of embryonic weights changed from a perfect correlation with parental weight at eleven days of incubation to a perfect correlation with egg weight at hatching and returned to a close relationship with parental weights at two weeks after hatching. They concluded that egg weight exerted a temporary environmental influence which concealed genetic differences in embryonic and early post-hatching growth among strains. The above investigations indicate that egg weight exerts a pronounced influence on growth during the late stage of incubation and the early post-hatching period. The evidence they provide about the influence of egg weight on the early and intermediate stages of em-bryonic growth is inconclusive. Investigation of the effect of breed or strain on growth has been equally extensive as that of egg weight on growth. Henderson (1930) measured the wet weight, dry weight, and total nitrogen content of Dark Cornish and White Leghorn embryos from four to twenty days of incubation and found l i t t l e difference between the breeds. Byerly (1930), in a previously mentioned study, used embryos of Rhode Island Reds, White Leghorns, and reciprocal cross-es between the two. He observed that embryos of Rhode Island Reds and cross-breds were somewhat heavier than White Leghorn embryos from the tenth day of incubation to hatching. In eggs of the same weight from the two breeds the embryo-size difference tended to disappear toward hatching time. Blunn and Gregory (1935) measured growth by weight, c e l l counts, and mitotic figure counts at seventy-two hours, fourteen days, and nineteen days of incubation. They observed a consistent difference between White Leghorn and Rhode Island Red embryos in the rate of c e l l proliferation. The difference in the number of cells per unit volume was less at nineteen days than at fourteen days or at seventy-two hours. In spite of significant differences in the rate of c e l l proliferation, these investigators found no significant breed differen-ces in embryonic weights. Byerly, Helsel, and Quinn (1938); studied embryos of White Leghorns, Silkies, Rhode Island Reds, and reciprocal crosses of S i l -kies and Rhode Island Reds. They found that during the period from the e l -eventh to the seventeenth day embryos of heavier parents were, in general, slightly heavier than embryos of lighter parents, even from eggs of similar weight. McNary, Bell, and Moore ( i 9 6 0 ) studied the growth of inbred and crossbred embryos of White Leghorns, Rhode Island Reds, and New Hampshires. They measured growth rate by counting the number of somites present after thirty-eight hours of incubation. They also recorded embryo weights after one week and two weeks of incubation. They reported significant genetic dif-ferences in a l l three measurements. Egg weight had l i t t l e effect on embry-onic weight because i t explained only 0 .06 per cent of the variation in em-bryonic weight at one week and 3 per cent of the variation at two weeks of age. Bray and Iton (1962) likewise observed genetic differences in embry-onic weight. The differences were significant from the tenth day of incub-5 ation onwards. It i s evident from the foregoing review that genetic differences in growth are discernible from the early stages of embryonic development. These differences were mostly differences in actual weight of the embryos or chicks. Few investigators of size inheritance in poultry have attempted to determine genetic differences in growth on the basis of the percentage or relative rate of increase in body weight per unit time. Those who have attempted such com-parisons have used mathematical formulae involving either the calculation of differences in actual weight at two or more periods of time or the f i t t i n g of an equation to the data collected. Lerner and Asmundson (1932) applied a formula of the former type to the study of growth rate of Light Sussex, An-conas, and crosses of the two breeds from three to twelve weeks after hatch-ing. They obtained significant genetic differences. Asmundson and Lerner (l933)> employing the same type of formula, found significant differences bet-ween White Leghorn families in rate of growth from two to eight weeks after hatching. Other workers have applied variations of the second type of form-ula to the study of embryonic growth in the domestic fowl but these applica-tions were not designed to determine genetic differences in growth rate in this species. For instance, Murray (1925) and Brody (1927) were interested in finding linear equations that would express the relative rate of growth of the chicken embryo. Byerly (1932) used a similar type of equation to demon-strate growth rates of embryos from different genetic sources but he assumed that the rates of growth of the different types of embryos were identical. Henderson and Penquite (1934) used Brody's equation to compare embryonic growth rates of chickens with those of turkeys, ducks and geese. 6 The above review of literature indicates that both egg weight and inherent genetic factors influence embryonic and post-embryonic growth. It does not, however, indicate clearly the extent to which egg weight modifies genetic differences. Neither does i t indicate the extent to which embryon-ic growth rate and post-embryonic growth rate are correlated. This study was undertaken to investigate these problems. The purpose was to study the relationships between (l) egg weight and body weight of embryo and chick; (2) strain and body weight of embryo and chick; (3 ) strain and percentage growth rate of embryo and chick; and (k) the relationship between embryonic growth rate and post-hatching growth rate. The fourth aspect of this study may have practical significance. Exhaustive investigations of this aspect may indicate whether or not there i s a high correlation between embryonic growth rate and post-hatching growth rate. If i t can be established that a high correlation exists then evaluation of growth rate of prospective breeding stock can be made on the basis of embryon-ic growth rate. Thus strains that are undesirable with respect to this char-acteristic can be eliminated at the embryonic stage. This practice would have the advantages of reducing rearing costs and accelerating a breeding pro-gramme . 7 MATERIALS AND METHODS Five strains and one strain-cross were used in this study. The parent stock was part of the flock of The University of Br i t i s h Columbia. The strains were of the following varieties: White Plymouth Rock, White New Hampshire, White Cornish, and White Leghorn. The strain-cross was derived from the mating of two White Leghorn strains. For the sake of convenience a l l six categories w i l l hereafter be referred to as strains. They w i l l be designated WR, WH, WC, MH, UBC, and MHxUBC, respectively. MH and UBC were White Leghorn strains, and MHxUBC was obtained from mating MH males and UBC females. WR, WH, and WC were classified as heavy or meat types, and the White Leghorns as light or egg types. On the basis of body weight at sexual matur-ity, the parent stock was ranked in the following ascending order of magnitude: MH, UBC, WH, WC, and WR. Hatching eggs were collected for fourteen days. Eggs were collected at mid-morning and mid-afternoon periods and stored in a room at approximately 55°F. More frequent collections were not made because the air temperature of the hen houses was considered to be low enough to prevent embryonic development. The eggs were weighed daily to the nearest gram. Table 1 shows the mean egg weights. The total egg collection of each strain was divided into twenty-two groups. In order to minimize differences due to the effect of storage on em-bryonic development, eggs were assigned at random to these groups in such a way that, in general, not more than three eggs from any day were included in a group. The twenty-two groups of eggs from each strain were divided into 8 two subgroups of eleven. One subgroup was incubated in each of two Jamesway Model 29^0 incubators. Eggs were set in eleven trays of each machine. There were six sections in each tray. Eggs from each strain occupied one section chosen at random. The trays were numbered consecutively and each was assign-ed a position in the incubator at random. The numbers determined the order in which the trays were withdrawn. Embryos were weighed from the ninth to the eighteenth day of incuba-tion. One tray was withdrawn daily from each incubator. Each developing em-bryo was removed from i t s shell and separated from i t s extra-embryonic membran-es by cutting the yolk stalk at i t s proximal end. An attempt was made to re-move as much amniotic f l u i d as possible by placing the embryo momentarily on a paper towel before weighing. The embryo was then transferred to a balance and weighed to the nearest one-hundredth of a gram. The weights of any embryos showing obvious abnormalities such as deformed beaks or undeveloped eyes were not recorded because the weights of such embryos were considered l i k e l y to bias the results. Table 2 shows the mean weights of the embryos, Tables 3a and 3b show the v a r i a b i l i t y of the weights, and Table k shows the number of embryos weighed and the number discarded. The eleventh tray of eggs in each incubator was candled on the nine-teenth day and the f e r t i l e eggs were transferred to the hatching compartment to hatch individually. On the twenty-second day the chicks were removed from the incubators, wing-banded and weighed to the nearest gram. The chicks from both incubators were grouped according to strain and assigned at random to six compartments in a battery brooder. They were weighed at weekly intervals to three weeks of age. Table 2 shows the mean weights of chicks and Tables 5a and 5b show the v a r i a b i l i t y of chick weights. 9 STATISTICAL METHODS The experimental design was that of a randomized complete-block with subsampling. Incubators were considered to be blocks and each developing em-bryo was considered to be a subsample of an experimental unit. This design was chosen in order to determine whether or not there was a significant in-teraction between incubators and strains. Consequently incubator effects, strain effects and incubator-strain effects were considered to be fixed and sampling error was used for testing hypotheses concerning interaction and strain effects. From the ninth day of incubation to the eighteenth day inclusive sub-samples of nine embryos were selected at random for analyses of variance. On the twenty-second day six chicks were similarly selected. Nine embryos and six chicks were the maximum numbers that could be thus selected in order to have equal numbers from each strain. Analyses of variance were done on embry-onic weights, egg weights, embryonic weights expressed as percentages of egg weights, and also on growth rates. Analyses of variance of egg weights were done on the eggs that yielded the selected embryos or chicks. The vali d i t y of the assumption of homogeneity of variances of the subsamples selected for analysis was verified by Bartlett's test. Variances of embryonic weights were heterogeneous on the tenth, twelfth, and thirteenth days. Variances of embryonic weights expressed as percentages of egg weights were heterogeneous on the tenth, thirteenth, and seventeenth days, and varian-ces of egg weights were heterogeneous on the tenth day. These variances were 1 0 not analyzed. Analyses of variance were not done on the grand total of pool-ed subsamples of egg weights because Bartlett's test showed that the variances were heterogeneous. The alternative approach of conducting separate analyses of variance on egg weights sub sampled each day was resorted to because varian-ces were homogeneous on every day except the tenth. Duncan's new multiple-range test as described by Steel and Torrie ( i 9 6 0 ) was used to make comparisons among strain means in a l l analyses of variance where significant differences were indicated. Tukey's test for non-additivity was applied to the embryonic weights expressed as percentages of egg weights in order to determine whether or not a transformation was necessary. Snedecor ( 1 9 5 6 ) advocates the use of this test for this purpose. Another method used to examine the data was the determination of the product moment coefficients of correlation between egg weight and embryonic or chick weight. From the ninth day of incubation to hatching coefficients were computed separately for each strain and each incubator. Separate analyses were done in order to compare the results obtained from each incubator. Since the chicks were separated after hatching on the basis of strain and not on the basis of the incubator in which they were hatched, computation of the coeffic-ients on the latter basis was not justi f i e d for the post-hatching period. For the correlation analyses the weights of a l l embryos and chicks and the weights of the eggs that yielded them were used. Coefficients of regression of chick weight on egg weight were also computed. A method different from those described above was adopted to examine the effect of strain on embryonic and post-hatching growth rate. Growth rate 11 in this report means the percentage increase in body weight at any instant. The computation of growth rate was based on the exponential function proposed by Brody (1927). The function i s : ¥ = Ae k t where ¥ = the weight of the embryo or chick at any observation point, t = the time, i.e. the day or week at which the observation was made, e = the base of natural logarithms, k = a constant which when multiplied by 100 gives the percen-tage growth rate, and A = the weight of the individual when t = 0. The parameter A has only theoretical significance. It does not indicate the actual weight of the zygote at time zero, the instant of f e r t i l i z a t i o n . Ex-trapolation of this value to time zero i s not jus t i f i e d because the constant was computed from data for the ninth day of incubation onwards. The above function was used because i t provided a means of compar-ing the strains on the basis of percentage increase in weight rather than on actual increase in weight per unit time. The former basis was preferred be-cause the object of interest was increase per unit weight. The natural log-arithm of the function provided the equation, InW = InA -t- kt, from which the curves were plotted on arith-log paper. This equation was f i t t e d to the data by the method of least squares. 12 Byerly (1932) c r i t i c i z e d Brody's method of f i t t i n g a straight line by inspection to points plotted on arith-log paper. He stated that the eye is a poor judge of goodness of f i t . Because of this criticism Student's t test was applied to the data to determine whether or not there was a linear relationship between InW and t for each strain. Differences in growth rate among the strains were tested for sig-nificance by analyzing the variance of rate of growth from day to day in the case of embryos and from week to week in the case of chicks. The variables to which the analyses of variance were applied were obtained from the equation k ^ lnw~2 - lnWj_ ^ where the subscripts 1 and 2 indicate the weights of the in-t2 " in-dividuals at the beginning (t]_) and at the end (t2) respectively, of the period. tg - tj_ was equal to unity in every case. To determine whether there was a significant relationship between growth rate during the embryonic period and growth rate during the three-week post-hatching period, product moment coefficients of correlation were comput-ed for the following time intervals: (l) nine to fourteen days of incubation, and zero to three weeks after hatching; and (2) fifteen to eighteen days of incubation and zero to three weeks after hatching. The fifteen- to eighteen-day rather than the fourteen- to eighteen-day period was chosen because there were no flexures in any of the curves during the former interval. The growth rates used in this analysis are presented in Table 17. 13 RESULTS AND DISCUSSION The results of Bartlett's test of homogeneity of variance are pres-ented in Tables 6a and 6b, and those for analyses of variance of embryonic and chick weights are presented in Table 7- The last table shows that dif-ferences among strains were highly significant at a l l observation points from the ninth to the eighteenth day of incubation, but were not significant on the twenty-second day. Significant differences are indicated in Table 8. Embryos of the heavy strains were significantly heavier than MH em-bryos from the ninth to the eighteenth day. This finding i s similar to that of Bray and Iton (1962), who, working with embryos from the same gene pool, obtained similar significant differences from the tenth to the seventeenth day. WR embryos were significantly heavier than MHxUBC embryos from the e l -eventh to the sixteenth day, and were significantly heavier than UBC embryos from the fourteenth to the eighteenth day. ' UBC and MHxUBC embryos were gen-erally not significantly heavier than MH embryos. The average weights of the meat-type embryos were greater than those of the egg-type embryos on every day for which tests were performed except the ninth day of incubation. The MH strain which ranked highest in egg weight ranked lowest in embryonic weight on every day except the eighteenth day of incubation. These results clearly demonstrate genetic differences in embry-onic weight from the eleventh to the eighteenth day of incubation. Table 9 shows the results of analyses of variance of egg weights based on a completely random design. There were non-significant differences Ik on a l l but the eleventh and twelfth days. Since for the most part there were no significant differences among egg weights, the significant differences am-ong embryonic weights were attributed to inherent genetic factors that influe-nced growth of the embryos. This finding i s contrary to Byerly's postulate that major weight differences among embryos of the same age can be satisfac-t o r i l y accounted for by differences in egg weight. Egg weights did not dif f e r significantly on the eighteenth day or at hatching. Embryonic weights differed significantly on the eighteenth day, but chick weights at hatching did not. Consequently, i t was concluded that egg weight, or, more precisely, yolk weight exerted an influence on embryonic weight between the eighteenth day of incubation and hatching. This was expec-ted since yolk absorption occurs during this interval, and according to J u l l and Heywang (1930) yolk material accounts for 15-30 per cent to 19-92 per cent of chick weight at hatching. Embryonic weights expressed as percentages of egg weights are shown in Table 10. Results of Tukey's test for non-additivity are shown in Table 11. This test indicated that the percentages did not require transformation. Consequently, analyses of variance were conducted on the actual percentages. Table 12 shows that there were genetic differences at a l l ages except at hatch-ing. On the twelfth day an interaction between incubators and strains was present. There was no reason to believe that this type of interaction would occur on one day only. Therefore this occurrence was attributed to sampling error. 15 Table 13 shows that, except on the twelfth day, embryonic weights expressed as percentages of egg weight were not significantly different among heavy strains on the days for which the test was performed. In contrast there were significant differences among the light strains on every day except the fifteenth and sixteenth. The heavy strains a l l ranked higher than the light ones on every day except the eleventh and twelfth. The measurements of the heavy strains were significantly greater than those of the MH on a l l days, but there were fluctuations in the significance of the differences among the heavy strains and the other two light ones. On a l l days the MH strain ranked lowest in measurement. These results agree substantially with those for actual body weight and manifest genetic differences in embryonic growth. In a l l strains chick weight averaged about 68 per cent of i n i t i a l egg weight. This value ag-rees with those of Upp (1928) and J u l l and Heywang (1930). Heavy-type embryos accounted for a significantly greater percentage of their egg weights than MH embryos did up to the eighteenth day but there were no significant differences at hatching. This evidence suggested that the yolk absorbed by MH embryos towards the end of the incubation period rep-resented a greater percentage of chick weight than i t did in the heavy strains. This phenomenon indicates either that yolk weight accounted for a greater per-centage of i n i t i a l egg weight in the MH strain than i t did in the heavy ones or that the heavy-type embryos u t i l i z e d a greater percentage of their yolk prior to the eighteenth day than MH embryos did. The findings of J u l l and Heywang (1930) provide evidence to support this conclusion. These authors calculated the mean percentage yolk weight of egg weight for different hens and found significant differences between several pairs of hens. They also 1 6 found that there were significant differences in the rate of assimilation of yolk material by the embryos from different White Leghorn hens. Coefficients of correlation (r) between egg weight and embryonic or chick weight are presented in Tables lha and iht. In at least one incubator a l l the strains showed evidence of a consistent increase in the magnitude of the coefficients as hatching time approached. The trend to consistent in-crease in magnitude began on the thirteenth day of incubation in the WH strain. In the WE and light strains i t began on the sixteenth day, and in the WC strain on the seventeenth day. The coefficients reached a maximum at hatching and de-clined thereafter. A few significant values were obtained before the seven-teenth day of incubation but were not part of a consistent trend and were there-fore considered to have occurred by chance. After the seventeenth day signif-icant correlation existed for longer periods in the heavy strains than i t did in the light ones. In the heavy strains correlation was significant by at least the eighteenth day in one incubator and continued to be significant at least to the end of the f i r s t week after hatching. In contrast, correlation in the light strains was significant only at hatching. At this stage high positive coefficients existed for a l l strains. There was thus no difference in the duration of the period for which significant values existed in the light strains but there were differences in the duration among the heavy strains. Significant values for WE existed from the seventeenth day of incubation to one week after hatching. For WR the correlation was significant from the eighteenth day of incubation to one week after hatching and for WC significant values were indicated from the eighteenth day of incubation to two weeks after hatching. These results show that significance of the correlation between egg 17 weight and embryonic or chick weight was different.among the heavy strains and more pronounced in these strains than in the light ones. The differences in the duration of a significant correlation may be associated with differences in the stage of development at which the yolk was absorbed by the embryos and differences in the rate at which i t was ut i l i z e d by the chicks after hatching. Perhaps the yolk of heavy strains started pas-sing into the intestine at an earlier stage than i t did in the light ones and was absorbed at a slower rate by the chicks of the heavy strains. Romanoff (i960) reported that yolk persists for varying periods of time in different chicks. The periods, he stated, range from two to thirty-four or more weeks. Table 15 shows the results of the analysis of regression of chick weight on egg weight. As was expected these results were similar to those of the correlation analysis. At hatching the coefficients of a l l strains were significant. Thereafter values of the light strains were non-significant. At one week of age the WR coefficient was significant at the 1 per cent level, whereas the WC and WH coefficients were significant at the 5 Ver cent level. At two weeks of age the WC coefficient was s t i l l significant at the 5 per cent level, whereas the others were non-significant. A l l values were non-significant at the end of the third week. Coefficients at hatching indicated that the in-crease in chick body weight that could be expected per gram increase in egg weight ranged from an average of 0.66 grams in the MHxUBC strain to an average of 0.84 grams in the WR and MH strains. According to magnitude of regression coefficient the strains ranked in the following ascending order: MHxUBC, WC, WH, UBC, WR, MH. There was thus no obvious relationship between magnitude of coefficient and type of chick i.e. meat or egg type. 18 The analyses of variance, correlation and regression considered jointly showed that significant strain differences in body weight existed bet-ween the ninth and eighteenth days of incubation, that any such differences which might have been present at hatching were almost entirely masked by the effect of egg weight and that there were strain differences in significance of the relationship between egg weight and body weight to two weeks after hatching. The results of Student's t test which was applied to show the rela-tionship between the natural logarithm of body weight and time are presented in Table 16. The test showed that there was a linear relationship between these two variables in each strain. Figures 1 and 2 demonstrate growth rate plotted on arith-log paper and Figures 3& "to kt demonstrate curves of growth plotted on arithmetic coordinate paper. The curves in Figures 1 and 2 show for each strain three periods of different growth rate between the ninth day of incubation and three weeks after hatching. The rate of growth during each period was calculated as a constant. For a l l strains except UBC and MH the periods occurred between (l) the ninth and fourteenth days of incubation; (2) the fourteenth and eighteenth days of incubation; and (3) hatching and three weeks thereafter. The second period for UBC was different; i t occurred bet-ween the fourteenth and seventeenth days of incubation. The f i r s t and second periods for MH were different; they occurred between the ninth and fifteenth days of incubation and between the fifteenth and eighteenth days of incubation respectively. These results conform with patterns observed by previous investig-19 ators. Brody (1927) found that the relative rate of growth of the chick emb-ryo tends to remain constant during certain intervals. Henderson and Brody (1927) reported that the chicken embryo passes through several distinct stag-es of growth during which the percentage-rate of growth is constant and that percentage-rate diminishes progressively from stage to stage. They also stat-ed that the rates of growth as well as the duration of each stage are influen-ced by temperature. Romanoff (1929) suggested that there are at least three well-defined cycles of embryonic growth In the chicken; one of these ends at nine and another at sixteen days of incubation. He, too, observed that a change in incubation temperature can shift the time of occurrence of the cycles. Hen-derson (1930) suggested that these stages were more closely related to attained weight than to time. The data of the present study indicate that the stages were more closely related to time than to weight, because changes in growth rate occurred on the fourteenth day of incubation in strains among which there were highly significant differences in embryonic weight. Growth rates are presented in Table 17 and results of the analyses of variance of growth rates in Tables l8a and l8b. There were no significant differences in the rate of embryonic growth among strains or between heavy and light types, but there were significant differences in the rate of post-hatching growth among strains and highly significant differences between heavy and light types. The heavy types considered as a group grew at a significantly greater rate than the light types considered as a group. The evidence so far considered indicates that differences in embryon-ic weights were significant but differences in embryonic growth rates were not 20 significant. This situation is explicable on the basis of the nature of the growth process. Reproducing cells tend to reproduce exponentially, i.e. at a constant percentage rate in a geometric progression. In this manner two in-dividuals differing in i n i t i a l weight may double their weights in the same time interval, but the one with the greater i n i t i a l weight w i l l be the heav-ier at the end of the interval. Thus minute differences at the beginning w i l l show up as considerable differences at a later stage. Differences in weights may, therefore, be simply a reflection of differences in the sizes and, by in-ference, the weights of zygotes which gave rise to the embryos. There are re-ports indicating that differences in c e l l size may be responsible for differ-ences in total size of an organism. Lerner (1937) n a s cited a number of work-ers who have found that body size was roughly proportional to c e l l size. The existence of significant differences in embryonic weight and non-existence of significant differences in embryonic growth rate may also be ex-plained in other ways. For instance i t is possible that the test applied to the growth rate data was not sufficiently sensitive to detect such differences. It i s also possible that differences in growth rate were so small as to be not significant at this stage. Another factor that might have influenced the re-sults of the test on embryonic growth rate i s that growth rate was calculated on the basis of average weights of different groups of embryos rather than on the same individuals from day to day. The last factor mentioned above did not exist during the post-hatching period because growth rate was computed on the basis of observed weights of the same individuals throughout this period. This may be one of the reasons for significant differences being manifest during this period and not during the 21 embryonic period. But different environmental conditions might also have had a bearing on the magnitude of differences in growth rate at this stage. For example the source of nutrients during the post-hatching period was the ration fed to the chicks whereas the source of nutrients during the embryonic period was the egg. It is possible that the faster growing strains u t i l i z e d nut-rients from the ration more ef f i c i e n t l y than the slower growing ones did dur-ing the post-hatching period whereas during the embryonic period there was no difference in the efficiency of u t i l i z a t i o n of nutrients among the strains. Another condition involving differences in efficiency of u t i l i z a t i o n of nut-rients during the post-hatching period might have had some influence on the magnitude of differences in growth rate. It concerns the duration of the per-iod in which egg weight was significantly correlated with chick weight. The suggestion was made in an earlier discussion that the yolk persisted for a lon-ger period in the heavy type chicks than i t did in the light type ones. If this longer persistence did occur then i t i s possible that the yolk material with i t s high fat content enabled the heavy type chicks to u t i l i z e the protein in the ration more eff i c i e n t l y than the light ones did. The significantly greater growth rate of the heavy type chicks probably resulted from a more ef-ficient u t i l i z a t i o n of protein in the ration. Card (1961) has reported that during the early post-hatching weeks chicks u t i l i z e protein with increasing ef-ficiency as the percentage of fat in the diet increases. There i s , of course, a limit to the extent to which the percentage of fat may be increased with ben-e f i c i a l results. The f i n a l phase of the investigation involved the determination of coefficients of correlation between embryonic growth rate and post-hatching growth rate. The coefficient of correlation (r) between growth rates for the 22 periods nine to fourteen days of incubation and zero to three weeks after hatch-ing was 0.805. This value is significantly different from zero at the 10 per cent level, but not at the 5 per cent level where a value of 0.811 is required for significance. The 95 per cent confidence limits for this estimate were -0.02 and 0-95- Approximately 65 per cent of the variation in post-hatching growth rate to three weeks of age was dependent on the variation in growth rate during the nine- to fourteen-day incubation period. However, an estimate of correlation with so wide a confidence interval i s not precise and was therefore considered to be of l i t t l e practical importance. A coefficient of -0.45 was ob-tained for the periods fifteen to eighteen days of incubation and zero to three weeks after hatching. In evaluating the results of this study one must bear in mind that the sample sizes were small. Small sample size imposes certain limitations on an experiment. The most important of "these limitations are that (i) the smaller the sample size the less accurate i s an estimate of a parameter l i k e l y to be; and ( i i ) a test performed on a sample that is too small is more l i k e l y to f a i l to detect significant differences than one performed on a sample that is large. Another point that must be considered in evaluating the results i s that an implied assumption in a l l the tests used to investigate differences in embryonic weight and growth rate was that the average incubation temperature was optimum for a l l the strains. Should this assumption be erroneous the re-sults could be misleading. 23 If investigation of the correlation between embryonic and post-hatching growth rates is to be conducted with a view to applying the results to breeding programmes, the problem of possible differences in optimum incub-ation temperature among strains w i l l have to be considered. The importance of this consideration suggested i t s e l f when differences in the time of occur-rence of flexures in the growth curves were observed. Henderson and Brody (1927) and others have shown that temperature greatly affects the position of flexures in the growth curve of the chicken embryo and also in the value of k, the relative rate of growth. A unit change in incubation temperature may not affect embryonic growth of different strains to the same extent. Consequent-l y i t is conceivable that, for different incubation temperatures, the correla-tion between embryonic and post-hatching growth rates may vary among strains in such a way as to complicate interpretation of the results. Such complica-tions would have a bearing on any generalizations that may be made about the relationship. This problem of different optimum incubation temperatures is a question arising from the present study that may warrant further investiga-tion. 2k CONCLUSIONS The conclusions that can be drawn from the foregoing results apply-only to the embryos and chicks that were used in this study and to the con-ditions under which the investigation was conducted. The conclusions are: (1) Differences in embryonic weights among the strains from nine to fourteen days of incubation were due to differences in in-herent genetic factors. (2) Egg weight exerted a temporary measurable influence on embry-onic and chick weight. This influence was evident from the last four or five days of incubation to two weeks after hatch-ing. At hatching the effect of egg weight almost completely concealed the effect of strain on chick weight. (3) Differences in post-hatching growth rate among the strains were probably due to differences in nutritional factors which contributed to a more efficient u t i l i z a t i o n of nutrients by the heavy type chicks. (k) Approximately 65 per cent of the variation in post-hatching growth rate to three weeks of age was dependent on the var-iation in growth rate during the nine- to fourteen-day in-cubation period. The estimate of correlation between growth rate during these two periods was, however, not precise, i.e. O the true value of the estimate could not be established with-in narrow limits. 25 BIBLIOGRAPHY Asmundson, V.S., and I.M. Lerner. 1933- Inheritance of rate of growth in domestic fowl. II. Genetic variation in growth of Leghorns. Poultry Sci. 12: 250-255. Blunn, C.T., and Paul W. Gregory. 1935- The embryo-logical basis of size inheritance in the chicken. J. Exp. Zool. 70: 397-4l4. Bray, D.F., and E.L. Iton. 1962. The effect of egg weight on strain dif-ferences in embryonic and postembryonic growth in the domestic fowl. (Unpublished). Brody, S. 1927- Growth and development. III. Growth rates, their eval-uation and significance. Univ. Missouri Agric. Exp. Sta. Res. Bull. 97: 5-70. Byerly, T.C. 1930. The effects of breed on the growth of the chick embryo. J. Morph. and Physiol. 50: 341-359-. 1932. Growth of the chick embryo in relation to i t s food sup-ply. J. Exp. Biol. 9: 15-44. Byerly, T.C, W.C. Helsel, and J.P. Quinn. 1938. Growth in weight and c e l l number. Genetic effects in the chick embryo and chick. J. Exp. Zool. 78: 185-203-Card, L.E. 1961. Poultry production. 9"th ed., 409 P- Philadelphia: Lea and Febiger. Goodwin, K. 1961. Effect of hatching egg size and chick size upon subsequent growth rate in chickens. Poultry Sci. 40: 1408. Halbersleben, D.L., and F.E. Mussehl. 1922. Relation of egg weight to chick weight at hatching. Poultry Sci. 1: 143-144. Henderson, E.W. 1930. Growth and development. XVI. The influence of temp-erature and breeding upon the rate of growth of chick embryos. Univ. Missouri Agric. Exp. Sta. Res. Bull. 149: 5-47-Henderson, E.W., and S. Brody. 1927- Growth and development. V. The effect of temperature on the percentage-rate of growth of the chick embryo. Univ. Missouri Agric. Exp. Sta. Res. Bull. 99: 3-H-Henderson, E.W., and R. Penquite. 1934. A comparison of embryonic growth rates of chickens, turkeys, ducks and geese. 5"th. World's Poultry Con-gress. 2: 297-306. 26 J u l l , M.A., and B.W. Heywang. 1930. Yolk assimilation during the embryonic development of the chick. Poultry Sci. 9: 393-404. Kosin, I.L., H. Abplanalp, J. Gutierrez, and J.S. Carver. 1952. The i n f l u -ence of egg size on subsequent early growth of the chick. Poultry Sci. 31: 247-254. Lerner, I.M. 1937- Relative growth and hereditary size limitations in the domestic fowl. Hilgardia 10: 5H-560. Lerner, I.M., and V.S. Asmundson. 1932. Inheritance of rate of growth in domestic fowl. I. Methods and preliminary report on results obtained with two breeds. Scient. Agr. 12: 652-664. McNary, H.W., A.E. Bell, and CH. Moore, i960. The growth of inbred and hybrid chicken embryos. Poultry Sci. 39: 378-384. Murray, H.A. Jr. Physiological ontogeny. A. Chicken embryos. III. Weight and growth rate as functions of age. J. Gen. Physiol. 9- 39-I+8-Romanoff, A.L. 1929- Cycles in the prenatal growth of the domestic fowl. Science 70: 484. . i960. The avian embryo. 1305 P- New York: The Macmillan Co. Snedecor, G.W. 1956. S t a t i s t i c a l methods. 5"th ed., 534 p. Ames: The Iowa State College Press. Steel, R.G.D., and J.H. Torrie. i960. Principles and procedures of statis-t i c s . 481 p. New York: McGraw-Hill Book Co. Upp, C.W. 1928. Egg weight, day old chick weight and rate of growth in Single Comb Rhode Island Red chicks. Poultry Sci. 7: 151-155-Wiley, W.H. 1950a. The influence of egg weight on the pre-hatching and post-hatching growth rate in the fowl. I. Egg weight-embryonic dev-elopment ratios. Poultry Sci. 29: 570-574. . 1950b. The influence of egg weight on the pre-hatching and post-hatching growth rate in the fowl. II. Egg weight-chick weight ratios. Poultry Sci. 29: 595-604. TABLE 1 MEAN EGG WEIGHTS IN GRAMS WR WC WH UBC MH 62.26 +4.35 60.54 +4.42 62.27 +4.90 61.73 + 3-75 62.68 +4.42 —j TABLE 2 MEAN EMBRYONIC AND CHICK WEIGHTS IN GRAMS (AVERAGES OF ALL EMBRYOS AND CHICKS WEIGHED) Days of Incubation Weeks After Hatching 9 10 11 12 13 14 15 16 17 18 22 I 2 3_ WR 1.55 2.52 3-47 5-51 7-29 11.16 13.78 17.32 20.72 23-46 43.85 96.08 169.38 264.12 WC 1.51 2.37 3-43 5-26 6.91 10.51 12.72 16.29 20.35 23.02 40.33 90.43 174.57 283.62 WH 1.52 2.47 3.34 5.01 6.97 10.42 13.26 17.10 20.87 25.10 43-42 89.OO 166.52 261.30 UBC 1.54 2.25 3.29 4.65 6.63 9.30 11.88 15.73 19-50 21.46 41.78 80.65 142.12 209.65 MHxUBC I.56 2.24 3-20 5-02 6.48 10.00 12.21 15-55 19-46 22.84 42.38 76.90 142.76 212.05 MH 1.35 2.11 3-04 4.20 5.65 9-04 11.66 14.99 18.34 21.47 42.12 79.69 140.47 207.06 ro 00 TABLE 3a VARIABILITY OF EMBRYONIC WEIGHTS Incub-Day ator WR WC WH Standard Standard Standard No. of Mean Wt Deviation No. of Mean Wt Deviation No. of Mean Wt Deviatioi Embryos (GM) (GM) Embryos (GM) (GM) Embryos (GM) (GM) 9 1 13 1.44 +0.17 10 1.47 +0.19 18 1.39 +0.18 2 15 1.65 + .54 16 1.54 + .19 16 I.67 + .21 10 1 15 2.53 + .19 14 2.39 + .22 14 2.54 + .15 2 Ik 2.52 + .14 15 2.35 + .29 17 2.41 + .15 11 1 15 3-57 + .42 12 3-42 + .41 17 3.47 + .26 2 14 3-37 + • 25 12 3.43 + .30 17 3-22 + .30 12 1 12 5.74 + • 47 11 5.65 + .29 15 5.19 + .59 2 15 5-33 + .40 13 4.93 + .56 18 4.86 + -75 13 1 16 7.42 +1.24 14 7.08 +1.22 14 7-37 + .92 2 15 7.14 + .92 13 6.73 + .54 18 6.66 + .59 Ik 1 16 11.28 +0.79 10 10.74 +0.94 15 10.65 +1.03 2 13 11.01 +1 .12 13 10.33 + .81 17 10.22 +1.27 15 1 10 13.91 +1 • 19 14 13-04 + .92 17 12.82 +1.04 2 13 13.68 + .85 13 12.37 +1.10 16 13.73 +1.07 16 1 10 17.06 + • 93 16 16.43 +1.31 15 16.74 +1.74 2 9 17.62 +1.43 13 l 6 . l l + .91 17 17.43 +1.24 TABLE 3a (continued) Incub-Day ator WE WC WH Standard Standard Standard No. of Mean Wt Deviation No. of Mean Wt Deviation No. of Mean Wt Deviation Embryos (GM) (GM) Embryos (GM) (GM) Embryos (GM) (GM) IT 1 l4 20.66 +2.01 12 19-90 +1.70 17 21.04 +1-53 2 16 20.78 +1.98 10 20.89 +1-75 13 20.64 +1.01 18 1 15 23-97 +1.07 Ik 23-25 +1.11 15 25-24 +2.51 2 9 22.60 +2.51 16 22.81 +1.66 17 24.97 +2.24 00 o TABLE 3b VARIABILITY OF EMBRYONIC WEIGHTS Incub-Day ator UBC MHxUBC MH Standard Standard Standard No. of Embryos Mean Wt (GM) Deviation (GM) No. of Embryos Mean Wt (GM) Deviation (GM) No. of Embryos Mean Wt (GM) Deviation (GM) 9 l 10 1.48 +0. .20 10 1.45 +0 .11 12 1.26 +0 •19 2 11 1.60 + , • 19 14 1.65 + •17 10 1.45 + .08 10 1 12 2.21 + , ,24 13 2.36 + .16 11 2.03 + -15 2 12 2.29 + , ,21 13 2. ,12 + •29 13 2.17 + -13 11 1 9 3-32 + , •19 14 3. .13 + • 32 13 3-22 + .18 2 12 3-27 + , •23 11 3. • 30 + .21 10 2.81 + -23 12 1 13 4.74 + , •36 14 5. • 13 + • 33 12 4.22 + -55 2 11 4.54 + , ,18 12 4, •89 + • 31 12 4.18 + -49 13 1 12 6.99 + , • 71 13 6, • 63 + •25 12 6.04 + •39 2 13 6.30 + . .67 12 6, • 32 + •92 14 5.32 + .60 14 1 12 9.26 +1. .16 10 9. • 93 + •49 12 9-30 + •79 2 10 9.36 + , .84 12 10. .06 + • 73 9 8.69 + • 65 15 1 11 II.89 +1. .07 13 12. • 33 + •71 12 12.00 + • 93 2 9 11.87 + , • 57 12 12. .07 +1 .24 13 11.35 + .85 16 1 Ik 16.01 +1, .24 13 15. ,92 + .61 11 15-37 +1 .42 2 11 15.37 +1. .00 11 15. .11 +1 •51 13 14.68 +1 .04 UJ H TABLE 3b (continued) Incub-Day at or UBC MHxUBC MH Standard Standard Standard No. of Mean Wt Deviation No. of Mean Wt Deviation No. of Mean Wt Deviation Embryos (GM) (GM) Embryos (GM) (GM) Embryos (GM) (GM) 17 1 13 19-53 +1.47 13 19.61 +1.14 12 18.51 +1.17 2 11 19.46 +1.64 13 19-30 +1.57 13 18.19 +2.13 18 1 9 21.97 +1.96 12 23.60 +2.17 13 22.29 +I.78 2 12 21.09 +2.00 14 22.20 +1.88 10 20.40 +1.45 ro TABLE k TOTAL NUMBER OF EMBRYOS EXTRACTED Number Weighed Number Discarded WR 269 k WC 261 3 WH 323 1 UBC 227 0 MHxUBC 2^ 9 2 MH 237 0 CO TABLE 5a VARIABILITY OF CHICK WEIGHTS Incub-Week at or WR WC WH Standard Standard Standard No. of Mean Wt Deviation No. of Mean Wt Deviation No. of Mean Wt Deviation Chicks (GM) (GM) Chicks (GM) (GM) Chicks ( G M ) (GM) 0 1 13 44.00 + 4.91 12 41.67 + 3.96 19 43.74 + 4.62 2 13 43.69 + 3.31 9 38.56 + 3-37 14 43.00 + 2.45 1 26 96.08 +11.31 21 90.43 +10.19 33 89.OO + 7.74 2 26 169•38 +19.74 21 17 -^57 +20.08 33 166.52 +16.94 3 26 264.12 +28.18 21 283.62 +36.22 33 261.30 ±37-50 OJ 4=" TABLE 5b VARIABILITY OF CHICK WEIGHTS Incub-Week at or UBC MHxUBC MH No. of Chicks Mean Wt ( G M ) Standard Deviation (GM) No. of Chicks Mean Wt (GM) Standard Deviation (GM) No. of Chicks Mean Wt (GM) Standard Deviation (GM) 0 1 2 10 8 41.80 41.75 + 3-03 + 3.67 12 9 41.67 43-33 + 1.89 + 2.36 10 6 42.30 41.83 + 2.86 + 3-39 1 I T 80.65 + 7-37 21 76.90 + 7-10 16 79.69 + 5-00 2 17 142.12 +13.56 21 142.76 +15•20 15 140.47 +10.08 3 17 209.65 +24.28 21 212.05 +27.49 16 207.06 +14.71 LO TABLE 6a RESULTS OF BARTLETT'S TEST OF HOMOGENEITY OF VARIANCE ~ for 5 degrees of freedom = 11.1 Embryo or Chick Embryo or Chick Weight as $ Day Weight Egg Weight Egg Weight 9 1-90 1.33 5-39 10 i 6 . 0 7 M 154. k6m 12.15* 11 7-20 4.23 2.08 12 2 2 . 3 9 M 10.99 8.73 13 19.89** 17.90** 5.39 Ik 9.5+ 10.72 3.26 15 1-72 7.13 3-35 16 7-50 0.79 3-55 17 9.96 13.60* 4.06 18 8.36 5-66 3-91 22 3-48 5.18 2.06 AA Significant at P=0.01 A Significant at P=0.05 TABLE 6b RESULTS OF BARTLETT'S TEST OF HOMOGENEITY OF VARIANCE X .05 f o r 5 degrees of freedom = 11.1 X2 9-14- days 15-18 days 0-3 weeks inc u b a t i o n i n c u b a t i o n post-hatching 10.59 4.14- 3-93 TABLE 7 ANALYSES OF VARIANCE OF EMBRYONIC AND CHICK WEIGHTS Source Degrees Mean Squares of Variation of Freedom Day 9 11 14 15 16 17 18 22 Incubators(i) 1 1. .17 0.35 k.69 1.00 3.86 0.01 20.23 1-39 Strains (S) 5 0. 1 j j jfcfe o.4o** 11.51** 11.67** 23.49** 30.89** 11.12 I x S 5 0. .01 0.19 0.60 1.10 2.59 3.26 6.19 26.92 Sampling Error 96 „ (6o) # 0. .03 0.10 0.87 1.07 1.63 3.18 4.46 11.62 Total 107 „ (7D# 1. • 35 1.04 17.67 14.84 21.40 29.94 61.77 51.05 M Significant at P=0.01 # Statistic for 22nd day. TABLE 8 RESULTS OF DUNCAN'S NEW MULTIPLE-RANGE TEST USED ON MEAN EMBRYONIC AND CHICK WEIGHTS IN GRAMS Age Standard Error of (Days) The Mean 9 MH WC WH MHxUBC UBC WR 1.34 1.46 1.54 1.56 1.56 1.56. +0.04 11 MH MHxUBC UBC WH WC WR 3.04 3.18 3.28 3-33 3-42 3-43 +0.08 14 MH UBC MHxUBC WH WC WR 8.95 9.27 10.01 10.30 10.50 11.11 +0.22 15 MH UBC MHxUBC WC WH WR 11.76 11.81 12.18 12.54 13.34 13.69 +0.24 16 MH MHxUBC UBC WC WH WR 15.12 15-32 15.82 16.48 16.62 17.38 +0.31 17 MH UBC MHxUBC WC WR WH 18.03 19.39 19.81 20.73 20.88 20.98 +0.42 18 UBC MH MHxUBC WC WR WH 21.38 21.46 22.79 . 23.10 23.18 24.92 +0.50 22 MH WH WC UBC MHxUBC WR 41-75 41-75 41.83 42.17 42.42 44.25 +O.98 Any values not underscored by the same line are significantly different. Any values underscored by the same line are not significantly different. TABLE 9 ANALYSES OF VARIANCE OF EGG WEIGHTS Source Degrees Mean Squares of Variation of Freedom Day 9 11 12 13 14 15 16 17 18 22 Strains (5)* 14.54 73.86** 45-13* 21.40 23-93 21.16 10.25 43.47 52.51 6.11 Error (66)# 16.89 20.91 18.63 16.24 15.68 16.79 17.45 22.23 25.26 18.88 107 „ ( 7 D # 31-43 94.77 63.76 37-64 39.61 37-95 27.70 65-70 77-77 24.99 AA Significant at P=0.01 A Significant at P=0.05 # Statistic for 22nd day TABLE 10 EMBRYONIC AND CHICK WEIGHTS EXPRESSED AS PERCENTAGES OF EGG WEIGHT (AVERAGES OF ALL EMBRYOS WEIGHED)  Days of Incubation 9 10 11 12 13 14 15 16 17 18 22 WR 2.4-7 3.96 5.52 8.92 11.50 18.10 21.98 27.41 33-30 38.40 68.43 WC 2.4-8 3.98 5.63 8.88 11.36 17.12 20.70 26.32 34.25 37-73 67.44 WH 2.46 3.98 5.23 7-93 11.43 16.80 21.34 27.60 33.62 39.63 68.47 UBC 2.49 3.66 5.49 7-46 10.83 15-04 18.89 25.19 31.59 34.17 67.44 MHxUBC 2.49 3.56 5.32 8.28 10.52 16.40 20.00 25.27 31.25 36.80 68.73 MH 2.11 3.35 4.78 6.69 9.34 14.29 18.62 23.96 29.80 33-43 67.94 4=-H TABLE 11 RESULTS OF TUKEY'S TEST FOR NON ADDITIVITY (EMBRYONIC AND CHICK WEIGHTS EXPRESSED AS PERCENTAGES OF EGG WEIGHT) Mean Squares Degrees of Freedom Day 9 10 11 12 13 Ik 15 16 17 18 22 Error Non-Additivity 96 (6o)# 1 .01 .01 .08 • 72 • 03 .07 .02 .16 .21 .90 .09 For Testing 95 (59)# .11 .21 M .89 2.52 3.38 3-97 5.19 12.17 12. kk 4.82 # Statistic for 22nd day. TABLE 12 ANALYSES OF VARIANCE OF EMBRYONIC AND CHICK WEIGHTS EXPRESSED AS PERCENTAGES OF EGG WEIGHT Source of Variation Degrees of Freedom 11 Mean Squares Day 12 14 15 16 18 22 Incubators (i) 3.05 0.08 10.99 k.ko 9.76 28.76 5.80 Strains (s) 5 0.38A 1.71* 17-23* 38.50* 35.85 M 34.01™ IO6.52* 8.20 I x S 5 0.05 0.78 2.70* 2.34 4.23 7.12 15.22 4.07 Sampling . Error 96 .. 0.11 0.43 (60 F  0.1 3-35 3-93 5-14 12.32 4.74 Total 107 «- 3-59 (7lF 3-00 31.81 53.17 48.41 56.03 162.82 22.81 A Significant at P=0.05 M. Significant at P=0.01 # Statistic for 22nd day TABLE 13 RESULTS OF DUNCAN'S NEW MULTIPLE-RANGE TEST USED ON MEAN EMBRYONIC AMD CHICK WEIGHTS EXPRESSED AS PERCENTAGES OF EGG WEIGHT Age Standard Error of (Days) The Mean 9 MH MHxUBC UBC wc WH WR 3-38 3.50 3-66 3.87 4.05 4.08 +0.08 11 MH WH MHxUBC WR UBC WC 4.74 5.18 5.26 5.38 5-53 5.60 +0.16 12 MH UBC WH MHxUBC WC WR 6.52 7.45 7.80 8.35 9.01 9.06 +0.23 14 MH UBC MHxUBC WH WC WR 14.13 15.09 16.33 16.71 17.58 17.95 +0.43 15 MH UBC MHxUBC WC WH WR I8.56 18.62 19.93 20.69 21.32 21-99 +0.47 16 MH MHxUBC UBC WC WH WR 24.08 24.98 25.32 26.75 27.00 27.64 +0.54 18 MH UBC MHxUBC WR WC WH 33-20 34.22 36.86 37-93 38.40 39-30 +0.83 22 MH WH WC UBC MHxUBC WR 67.51 67.82 68.07 68.14 68.85 69.78 +0.62 Any values not underscored by the same l i n e are s i g n i f i c a n t l y d i f f e r e n t . Any values underscored by the same l i n e are not s i g n i f i c a n t l y d i f f e r e n t . TABLE lim COEFFICIENTS OF CORRELATION (r) BETWEEN EGG WEIGHT AND EMBRYONIC OR CHICK WEIGHT Age WR WC WH Inc 1 Inc 2 Inc 1 Inc 2 Inc 1 Inc 2 9 Days -•350 .063 -.710* • 131 .114 - .068 10 • 300 -.409 -.480 -.478 .670* .084 11 .340 -.374 -.090 .024 - .440 - .172 12 • 125 -.196 -.092 -.068 .290 .001 13 -.098 -.634* .180 -.566* .036 .291 11+ .116 .197 -.205 -.313 .240 .123 15 -.062 .450 .760* -.366 .418 .156 16 .360 .094 .325 .076 .456 .772* 17 -.236 .225 .091 -.239 .652* .290 18 .542* • 493 .230 .594* .616* .811* 22 (Hatch) t gl|/7** .895™ .887™ : .902™ .976™ 1 Week • 501* • 534* .419* 2 Weeks .149 .445* .261 3 " .043 .297 .082 A Significant at P=0.05 ML Significant at P=0.01 TABLE l4b COEFFICIENTS OF CORRELATION (r) BETWEEN EGG WEIGHT AND EMBRYONIC OR CHICK WEIGHT Age UBC MH MHxUBC Inc 1 Inc 2 Inc 1 Inc 2 Inc 1 Inc 2 9 Days -.170 .186 -.620* -.275 .068 .176 10 .680* .356 .040 -.089 -.226 .125 11 .072 .142 -.450 -.178 -.614* -.440 12 .024 -.188 -.061 -.145 .160 .241 13 .100 ..344 .380 .021 .710 .333 14 .297 -.261 -.4io -.063 .610 .005 15 • 301 • 511 .385 -.018 .229 • 590J 16 .158 -.028 .272 .211 .058 .156 17 .291 -.153 .392 .058 .385 .286 18 •549 -•503 .422 - • 353 .410 • 347 22 (Hatch) • 910* A .832* .895*^  L Qfy ~| ^^^^ .889** t • 9^5] 1 Week .425 .284 -239 2 Weeks .118 .030 ,181 3 " - .044 .018 • 139 A Significant at P=0.05 ±k Significant at P=0.01 TABLE 15 REGRESSION COEFFICIENTS GRAMS OF CHICK WEIGHT ON GRAMS OF EGG WEIGHT Incubator Age (Weeks) 0 1 2 3 WR 1 . go5™ 2 .768 M -A-A-3_. 245™ .647 .269 WC 1 ry-i QitM 2 • 7-Lo JV.JL 1.050* 1.719* 2.07 WH 1 .746™ 2 A .A. .663* .904 .628 UBC 1 .856™ 2 .754* A A .884 .451 -.301 MH 1 2 . Y 0 4 ™ .403 .087 • 075 MHxUBC 1 .565™ 2 .563 .913 1.271 A Significant at P=0.05 &k Significant at P=0.01 TABLE 16 RESULTS OF TESTS FOR LINEAR RELATIONSHIP BETWEEN InW AND TIME t Values Strains Incubation Periods Post-Hatching Period 9-14 Days Ik-18 Days 0-3 Weeks t.05 = 2.776 t.05 = 4.303 t.05 = k.303 WR 30.82 10. • 79 11. ,02 WC 33.87 9-,88 4l. •57 WH 36.64 18. • 54 13. • 85 UBC 86.81 13. ,o6# 12. ,72 MHxUBC 36.67 15. • 79 14. •91 MH 22.28 13. .69 13. • 50 # t . 0 5 = 1 2 - 7 1 TABLE 17 EQUATIONS USED TQ PLOT GROWTH CURVES Incubation Period (Days) Class Equation Growth Rate InW = InA + kt (100k) Daily 9-l4 WR InW = -2.9956 + .3868t 38.68 WC InW = -2.97283 + -38lOt 38.10 WH InW = -2.91142 + .3752t 37.52 'UBC InW = -2.78441 + -3594t 35-9^ MH InW = -2.79025 + -35297t 35-30 MHxUBC InW = -2.88044 + -3693t 36.93 14-18 WR InW = -0.01238 + 0.l7744t 17.74 WC InW = -0.42924 + 0.2000t 20.00 WH InW = -0.56522 + 0.2113t 21.13 UBC InW = -1.22952 + 0.2477t 24.77 MH InW = -O.56726 + 0.203l6t 20.32 MHxUBC InW = -0.63164 + 0.21015t 21.02 Post-Hatching Period (Weeks) Weekly 0-3 WR InW = 3.87042 + o.59502t 59-50; (8.50) WC InW = 3.77720 + o.65052t 65.05; (9.29) WH InW = 3.83405 + 0.60099t 60.10; (8.59) UBC InW = 3.79487 + 0.54099t '54.10; (7-73) MH InW = 3.79728 + 0.53399t 53-40; (7.63) MHxUBC InW = 3-78465 + 0.54500t 54.50; (7-79) A Daily rates in parentheses TABLE 18a ANALYSES OF VARIANCE OF GROWTH RATES Source of Variation Degrees of Freedom Mean Squares Period 9-lk Days Incubation 15-18 Days Incubation 0-3 Weeks Post-Hatching Incubators (i) 1 .016 .0005 .015 Strains (s) 5 .003 .0009 .068* I x S 5 .001 .0003 .006 Sampling Error 48 a 24b 20kc .009 • 0057 .020 Total 5 9 a 3 5b 215c .029 .007+ .109 A Significant at P=0.05 Statistic for 15-18 days a Statistic for 9-lk days c Statistic for 0-3 weeks RESULTS OF DUNCAN'S MULTIPLE-RANGE TEST MH MHxUBC UBC WH WR WC •530 -537 -539 -594 .609 .631 Any values not underscored by the same line are significantly different Any values underscored by the same line are not significantly different TABLE 18b ANALYSES OF VARIANCE OF GROWTH RATES Source of Variation Degrees of Freedom 9-l4 Days Incubation Mean Squares Period 15-18 Days Incubation 0-3 Weeks Post-Hatchins Types .008 .0001 • 31* Error Total 58 a 2l4 c 59* 35b 215c .007 .015 ,0042 .0043 .02 • 33 AA Significant at P=0.01 a Statistic for 9-l4 days h Statistic for 15-18 days c Statistic for 0-3 weeks 52 53 Figure 2. Arith-log graphs of growth rate obtained from the equation : InW = In A* F igu r « 3 a Arithmetic graphs of growth rata 5 5 56 300 P O S T - H A T C H I N G A G E ( W E E K S ] Figure4a. Arithmetic graphs of growth rate. 57 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0105701/manifest

Comment

Related Items