GROWTH AND £00 PRODUCTION OF PUREBRED, CROSShRED AND INCROSSHRED POULTRY
DISSERTATION
Presented In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University
John Francis Grimes, B.S., h.S
The Ohio State University 195U
Approved fay ACKNOWLEDGMENT
I wish to acknowledge my indebtedness to Dr* E. G e o r g e Jaap Tor his assistance, encouragement and counsel; to Swift a n d Company for their financial support of the entire project; and to tlie staff of the Poultry Science Department for their cooperation s u x d assistance*
J . F . G.
-i- t a b l r o f CONTENTS
Page
INTRODUCTION ...... 1
REVIEW OF LITERATURE ...... 2 I. Growth...... 2 A* Crossbreeding Experiments ...... 2 B. Inbreeding Experiments ...... 9 II. Egg Production ...... 21* A. Crossbreeding Experiments ...... 21* B. Influence of Inbreeding on Egg Production . . . 32 III. Albumen Quality...... 1*3
...... 1*7 I. Materials and Methods...... 1*7 II. Results. 5i A. Boty Weight at 6, 9 and 12 Weeks of Age • • • • 51 1. 191*7-1*3 T e s t ...... 51 2. 191*3-1*9 T e s t ...... 55 3. 1950-51 T e s t ...... 56 1*. 1951-52 T e s t ...... 57 5. 1952-53 Test ...... 53 B. Nature of the Variability...... 59 1. 191*7-1*3 T e s t ...... 59 2. 191*3-1*9 T e s t ...... 6l 3« 1950-51 T e s t ...... 62 1*. 1951-52 T e s t ...... 63 5. 1952-53 T e s t ...... 63 III. Discussion ...... 102 IV. Summary ...... 107
EGG PRODUCTION ...... 110 I. Materials and M e t h o d s ...... 110 II • R e s u l t s ...... U 3 A. 1950-51 T e s t ...... 113 B. 1951-52 T e s t ...... 119 C. 1952-53 T e s t ...... 122 III. Discussion...... 139 IV. Summary ...... 1 j|2
ALBUMEN QUALITY ...... ll*5 1. Materials and Methods ...... li*5 II. Results...... 153 III. D i s c u s s i o n ...... 170 IV. Summary ...... 17b
BIBLIOGRAPHY ......
AU TQBIO GRAPriY 190 LIST OF TABLES iLE Page
1 Summary of the kinds of stocks used in the project. . . . 66
2 Average 12 week weights of males in the broiler test of 19li7 “ltd (In pounds) • • «.*•••••••»»•••• 69
3 Average 12 week wex&hts of females in broiler test of iyU7-Ud (In pounds}...... 70
u Average 12 week weights of males by pens in the mixed pen broiler study of 19U7-U6 (in pounds}...... 71
5 Analysis of varxance of the mean 12 week weights of males in the mixed pen broiler stuqy of 19U7-U6......
6 Averabe 12 week weights of females by pens in the mixed pen broiler stuqy of 19hf'-Ud (in pounos}...... 72*
7 Analysis of varxance of the mean 12 week weights of females in the mixed pen broiler study of 19k7~k8» . . . 73
8 Mean differences of wexgnts of 12 week old niales in the straxgnt pens of the 19U7~hd broiler study (In pounds}. . 7h
9 jMean differences of weights of 12 week old females in the straight pens of the 19h7-U6 broiler study (In pounds}. . 7U
10 mean differences of wexgnts of 12 week old males in the .nixed pens of the 19U7-Ud broiler study (In pounds). . . 75
11 mean differences of we^dts of 12 week pla females in the mixed pens of tne 19k7“U& broiler study (in pounds). . . 75
12 Coefficients of variability of body weights of 12 week old males in tne iyif7“Ub broiler stuqy (Percent). . . . 7 6
13 Coefficients of variability of body wex0nts of 12 week old femaies in the 19U7-U6 broiler study (Percent). . . . 76
1U Average 6 week wexgnts of males arid females in the comparative test of 19h7-Ud (In pounds)...... 77
15 Average 12 week wexgnts of males and f emales xn the comparative test of ±9k7~h8 (in pounds}...... 78
16 Coefficients of variability of body weights of 6 and 12 week old males in the comparative test of X9U7-U& (Percent). . . , , , ...... 7 y -iii- LIST OF TABLES (cont.)
TABLE Page
17 Coefficients of variability of body weights of 6 and 12 weeic old females in the comparative test of 19L7-L8 (percent)...... SO
IS Average 6 week weights of males and females In the comparative test of 19L8 -L9 (In pounds)...... 51
19 Average 12 week weights of males and females in the comparative test of 19L8-L9 (In pounds)...... 52
20 Coefficients of variability of body weights of 6 week old males and females in the comparative test of 19l*d-L9 (Percent)...... • • • • 83
21 Coefficients of variability of body weights of 12 week old males and females in the comparative test of 191*8 -1*9 (Percent)...... 61*
22 Average 9 end 12 week weights of heavy type females in the comparative test of 1950-51 (in pounds)* ...... 55
23 Average 9 and l2 week weights of Leghorn type females in the comparative test of 1950-51 (In pounos)...... 56
2U Coefficients of variability of body weights of 9 and 12 week old heavy type females in the comparative test of 1950-51 (Percent)...... 87
25 Coefficients of variability of body weights of 9 and 12 week old Leghorn type females in tne comparative test of 1950-51 (Percent j...... 55
26 Average 9 and 12 weeK weights of neavy type females in the comparative test of 1951-52 (in pounds)...... 59
27 Average 9 and 12 week weights of Leghorn type females in the comparative test of 1951 "52 (in pounds)...... 90
25 Coefficients of variability of body weights of 9 and 12 week old neavy type females in the comparative test of 1951-52 (Percent) . 91
29 Coefficients of variability of body weights of 9 and 12 week old Leghorn type females in the comparative test of 1951-52 (Percent)...... 92 30 Average 9 and 12 week weights of heavy type females in the comparative test of 1952-53 (In pounds)...... 93 -IV- LIST OF TABLES (cont.)
TtHtJ. Fag*
31 Average 9 and 12 week weights of Leghorn type females in the comparative test of 1952-53 (in pounds)...... 9k
32 Coefficients of variability of body weights of 9 and i2 week old heavy type females in the comparative test of 1952-53 (Percent)...... 95
33 Coefficients of variability of Dody weights of 9 and 12 week old Leghorn type females in the comparative test of 1952-53 (Percent)...... 96
3L Average survivors' and hen-housed egg production for 195U-51...... 126
35 Analyses of variance of the survivors' egg production data of 1950-51 by strain and mating type. ...•••• 12?
36 Analyses of variance of the hen-housed egg production data of 1950-51 hy strain and mating type...... i2d
37 Average egg production of 26 hens per month for 18 strains in the 1950-51 t e s t ...... 130
3b Analysis of variance of the egg production data of 1950-51 hy strain, mating type, month and group. .... 131
39 Average egg production for 1951-52 on a survivors' and hen—housed basis...... 132
1*0 Analyses of variance of the survivors' egg production data of 1951-52 by strain and joating type...... 133
U1 Average egg production of 29 hens per month for lb strains in the 1951-52 test...... 13L
1*2 Analysis of variance of the egg production data of 1951-52 by strain, mating type, monoh and group. .... 135
U3 Average egg production for 1952-53 on a survivors' and hen-housed basis...... 137
UU Analyses of variance of the survivors' eg*, production data of 1952-53 by strain and mating type...... 136
US Frequency distribution of egg albumen scores in the December sampling period of 19L9-50...... 15U
-v- U 3T OF TABLKS (cont.)
BhE Page 1*6 Average albumen quality scores for the purebred, crossbred and incrossbred strains in 191*9-50, 1950-51» 1951-52 and 1952-53...... 155
1*7 Analysis of strain differences in egg albumen quality scores by the Chi-Square technique (191*9-50). . . . 156
1*8 Summary of the 191*9-50 egg quality data by number of "good" and "poor* quality eg^s laid by 12 strains. . 157
1*9 Analysis of variance of the egg quality oata of 191*9-50 by strain and mating type...... 157
50 Analysis of strain differences in egg albumen quality scores by the Chi-Square technique (1950-51)* * * * 156
5i Analysis of mating type differences in egg albumen quality scores by the Cni-Square technique (1950-51) 159
52 Summary of the 1950-51 egg quality data by number of "good*1 and "poor" quality eggs laid by Iti strains* . 1 6 0
53 Analysis of variance of the egg quality data of 1950-51 by strain and mating type...... 161
51* Analysis of strain differences in egg albumen quality scores by the Chi-Square technique (195l“52). * * . 162
55 Analysis of mating type differences in eg& aibymen quality scores by the Chi-Square technique...... 163
56 Summary of tne 1951-52 egg quality data by number of "good" and "poor" quality eggs laid by 18 strains. . 161*
57 Analysis of variance of the egg quality data of 1951-52 by strain and mating type...... 165 56 Analyses of strain differences in eg^ albumen quality scores by the Chi-Square technxque (1952-53)• . . • 166
59 Analysis of mating type differences in egg albumen quality scores by tne Cni-Square technique (1952-53) 167
60 SuuLiiary of the 1952-53 egg quality data by number of "good" and "poor" quality eg&s laxd oy 16 strains. . 166 61 Analysis of variance of the egg quaixty data of 1952-53 by straxn and mating type...... 169 -VI- LIST OF FiGUHES
FiflUKE Page
1 Halation between the variance and mean weight of all strains included in the project from 1956 through 1953 (9 weelc data)...... 91
2 Heiation between the variance and mean weight of all strains included nr; the project from 1956 through 1953 (12 week data)...... 96
3 Relation of variance to mean weight of 23 strains of "Heavy* purebreds (9 week data)...... 99
U Relation of variance to mean weight of 23 strains of "Heavy" purebreds (12 week data)...... lou
5 Relation of variance to mean weight of New hempshires (8 week data)...... 1U1
6 Percent uen-housed egg production of the purebred, crossbred and incrossbred mating types in 1950*31* * * • 129
7 Percent nen-noused egg production of the purebred, crossbred and incrossbred mating types in 1931*5^* • • • 136
-vii- INTRODUCTION
Evaluation of the results obtainable from different breeding systems is one of the major tasks confronting the poultry industry*
The industry is confused regarding the breeding method which will allow most rapid progress* There are people who believe that we have reached the end of genetic improvement in the chicken by standard or
"pure" breeding* Recent interest in inbreeding* crossbreeding* recip rocal recurrent selection and various other programs are indications that the industry does not know which method will give the desired re sults. kith the widespread interest in inbreeding* crossbreeding* strain crossing and other techniques designed to exploit the phenomenon of heterosis* the problem of evaluation has been greatly intensified.
Much work has been published on the efficacy of different breeding methods but comparisons in a similar environment cure very limited*
Much additional information is needed on basic comparisons of perform ance with a view to predicting the most desirable trends in commercial production as well as in breeding research*
In 19U7, a research program was inaugurated to evaluate the pro ductive fitness of chickens produced by various mating systems* The objectives were to compare uniformity of growth and egg production in chickens developed by different breeding systems and to secure infor mation on the performance of stock from purebred* crossbred and in crossbred origin.
The investigation herein reported provides additional basic infor mation on this acute problem facing poultry breeders.
1 REViEta OF LITERATURE
I. Growth
Growth as defined by Brody v 19Ui>) is the self multiplication of reproducing units, whether of individuals in a population or of cells in a multicellular organism. The curve of growth as shown by Broay
(1927), in weight cr volume, is divided into two principal components.
In the segment of increasing slope, the velocity of growth is propor tional to the growth already attained. The first component is initi ated by incubation and continues until sexual maturity is reached.
The velocity of the decreasing slope is proportional to the growth yet
to be made to reach body maturity.
Three general methods of evaluating the growth of an individual have been used by various investigators in the past. These are cumu lative weights, successive gains and relative rates of growth, i.e.,
some transformation of weight or gain. Since the literature dealing with the second and third methods has little bearing on the investi
gation to be reported here, this work is not included in this review.
A. Crossbreeding Experiments
One of the first comprehensive crossbreeding experiments was con
ducted by Pearl and Surface (1910). They made reciprocal crosses
between the Cornish Indian Game and Barred Plymouth Rock breeds. Data 2 were collected on many characteristics among which were infozwiation on hatenability, mortality snape of body. The progeny from the barred Plymouth Rock male by Cornish Indian Game female mating were good winter egg producers with a production equal to that of the pure
Barred Plymouth Rocks. The black crossbred pullets from the Cornish male by Barred Plymouth Rock female were poor winter layers*
The crossbreeding technique was not explored very much from then until Warren (1927} began his extensive studies* This was probably due to the influence of the poultry fancier and the cost of maintaining two breeds* Warren (1927) made reciprocal crosses oetween dingle Comb
White Legnorns and Jersey Black Giants; how ever, the results of the reciprocal crosses were not separated* In all of the comparisons, tne first generation crossbreds were compared with the pure breeds used in thexr production* The crossbreds exhibited vigor superior to the pure breeds in growtn from one to twelve weeks of age* In adult size, the crossbreds were intermediate to the parental breeds as would be expected from the nature of the cross* Succeeding generations did not show any hybrid vigor. Warren (19JQ) made crosses between dingle Comb
White Leghorns and Rhode Island Reds. The matings were made so that all crossbreds were haif-sibs to the purebreds with w m c h they were compared* The most rapidiy growing group to eight weeks of age was the progeny from the White Leghorn-Rhode Island Red mating. At 6 weeks of age these crossbreds were heavier than the pure Rhode Island Reds but by twelve weeks of age the Rhode Island Red purebreds weighed more than the heaviest crossbred* u
Additional reciprocal matings were made by Warren (1930) between
Single Comb White Leghorns, Rhode Island Reds and Barred Plymouth
Rocks* The males of each breed were rotated every two days so that
chicks of all crosses were produced in each hatch after the first one*
Each group of hybrids weighed more than the parental breeds at 10 weeks of age* Probably the most crucial test for the effects of hy
bridization on vigor in all of this work is found in the three groups
of progeny from the Rhode Island Red females* The hybrids were larger
than the Rhode Island Reds at practically every weighing period from
hatching to 12 weeks of age although tne Rhode Island Reds made very
good growth*
Haw (1933) made a comparative study of purebred and crossbred poultry* His heaviest crossbred at ten weeks of age (Cornish x Barred
Plymouth Rock) was no heavier than the heaviest purebred (Buff Orping
ton)*
Knox and Olsen (193d) published the results of a comparative test
of crossbred stock from different parts of the country against White
Leghorns bred by various breeders over the United States and against
Rhode Island Reds produced at Beltsville* No attempt was made to use
similar parental stock to produce the purebred and crossbred progeny*
The progeny from the crosses of the "general purpose” breeds, on the
average, were better than the purebred Rhode Island Reds, the White
Leghorns and the progeny from crosses involving the White Leghorns in
body weight at tan and twenty weeks and at body maturity* Of the
parental crosses studied in this experiment, the data indicate that
the average crossbred was superior only in the case of early body 5 weight. They concluded that the quality of the parental stock has considerable influence upon the quality of the hybrid progeny and that different strains of the same varieties of chickens may produce different results whan crossed. Knox (1939) gave a resume of this work at the Seventh World's Poultry Congress.
Horlacher and Smith (1933) gave a preliminary report on the possibilities of crossbreeding for broiler production. These investi gators made crosses between Rhode Island Reds, White Wyandot tes, White
Leghorns, Dark Cornish, Barred and White Plymouth Rocks; however, in only one case was the cross made reciprocally. Both parental types and the F-^ were raised concurrently to twelve weeks of age. The cross- ored progeny from the White Wyandotte by Rhode Island Red mating exhib ited hybrid vigor. These chicks grew more rapidly than any of the other crossbreds or purebreds and they required less feed to produce a given amount of gain.
Jeffery (1939) found that crossing a poor production strain of
Rhode Island Red with a good egg production strain of Barred Plymouth
Rocks produced hybrids giving superior results with respect to rate of growth to twelve weeks of age. The adult weight of the crossbreds was inferior to that of the purebreds.
Bice and Tower (1939) crossed Barred Plymouth Rock, Rhode Island
Red and White Leghorn females with Japanese Shamo Came males and re produced the pure breeds in separate mating pens. The crossbreds were compared with the purebred progeny but the crossbred and purebred progeny were not half-sibs. The crossbred males of all three groups grew more rapidly and ate less feed to eight weeks of age than the four 6 groups of purebreds. The purebred Japanese Shamo Game females were slightly heavier at eight weeks of age than the three groups of cross bred females, while the latter were heavier than the purebred Barred
Plymouth Rock, Rhode Island Red and White Leghorn females.
Horlacher, Smith and Wiley (l?Ul) reported on ten crosses and one reciprocal cross. They found that the progeny from a White Wyandotte by Rhode Island Red mating exhibited hybrid vigor in three consecutive years. They obtained varying results from different crosses but in
general the crossbreds were superior to the parental lines in rate of
growth and feed requirement to ten and twelve weeks of age.
Warren (19l|i and 19U2) summarised his crossbreeding experiments which covered a period of fourteen years. Data were collected on
twenty-two different crosses of twelve breeds and varieties. In five of the tests, comparisons were made during the same year between recip rocal crosses and the two pure breeds, providing a critical test of the
effects of crossbreeding, Warren suggested that this gave better assur
ance that the observed differences are the results of crossbreeding instead of being due to individual variation in genetic makeup of birds used as parents. He found that the weight of day old chicks reflects mainly variations in egg size and that the crossbreds generally grow more rapidly to six weeks of age than the purebreds from which they
came. When the Mediterranean breeds are crossed to larger breeds, the
crossbreds are usually intermediate in size after the first eight
weeks, while crossing two "general purpose" breeds usually produces
crossbreds which grow more rapidly than the parental lines at all ages.
He concluded that early growth rate exhibits a definite response to crossbreeding but later growth is conditioned by adult body size.
Boetian and Dearstyne (1942) made various crosses between White
Leghorns, Rhode Island Reds, Barred Plymouth Rocks and New Heaps hires.
Comparisons were made between half-sibs which were hatched on the same date and reared together. With few exceptions, the crossbred broilers exceeded their purebred half-sibs in weight at ten weeks of age.
Knox, Quinn and Godfrey (1943) made comparisons of Rhode Island
Reds, White Wyandottes, Light Sussex and crosses among them to produce
and three-way cross progeny. Data on mass-mated Rhode Island Red stock were used as the basis of comparison between the crossbred and purebred progeny since this would eliminate the effect of single male matings. They found that the progeny of the two- and three-way crossesj were usually heavier at ten and twenty weeks of age than the purebred
Rhode Island Reds. The perfozmance of Rhode Island Reds and Light
Sussex as compared with that of their and three-way crossbreds was reported by Knox, Gordon and Mehrhof (1949) * They found that the live body weights at all ages for the crossbreds were superior to those of the standardbred breeds used except when the White Leghorn was one of the parental breeds, in which case the progeny were intermediate*
Massey and Hoffmann (1946) made reciprocal crosses between one strain of New Hampshire males and three strains of Rhode Island Red females in an attempt to obtain broiler chicks from egg production dams. However, the crossbred progeny were intermediate in body weight to the parental breeds at twelve weeks of age. 6
O'Neil end Rae (19U6) observed from crossbreeding experiments that crossbred chicks grew more rapidly than purebred chicks* They observed further that the weight of the crossbred female chicks when expressed as a percentage of the setting weight of the egg is signifi cantly heavier than that of the purebred Barred Plymouth Rock females.
The same type of observation was noted on the male chicks. They pos tulated that this might oe one expression of hybrid vigor. New Hamp shire by Barred Plymouth Rock crossbreds and purebred Barred Plymouth
Rocks were used in this experiment*
Henderson (19k9) made receiprocal matings oetween White Leghorns and Dark Cornish and compared the weights of the crossbreds at sixteen weeks of age with the weights of purebred Dark Cornish and White Leg horns at the same age* The Dark Cornish purebred progeny were slightly slower growing than the White Leghorn purebred progeny. The female progeny from the Dark Cornish male by White Leghorn female mating did
not weigh as much at sixteen weeks as the standardbred White Leghorns, while the crossbreds from the reciprocal cross were slightly heavier
than the Leghorns*
Essary, Wountney and Goff (19$U) studied body conformation and
performance in Barred Plymouth Rocks, New hampshires ( a meat and an
egg strain) and reciprocal crosses between the meat strain New Hamp
shires and the Barred Plymouth Rocks. The crossbreds from both crosses
were heavier than the three groups of purebreds at twelve weeks of age*
The cross involving the Barred Plymouth Rock male by New Hampshire
meat strain females weighed two-tenths of a pound more at twelve weeks
than the progeny of the reciprocal cross. Ghost ley and Nordskog (1951) ‘>*ated eight strains from four breeds
(New Hampshire, Rhode Island Red, Barred Plymouth Rock and Australorp)
in all possible combinations in such a way that progeny of the three mating types— 'purebreds, strain crosses and breed crosses— were obtain
ed from each breeding pen. Growth and chick viability exhibited the
greatest expression of hybrid vigor. On the average, the crossbred
and the strain crosses were fifty-eight and thirty grams heavier respec
tively than the pure strains at eight weeks of age.
King (1951) and King and Bruckner (1952) made a comparative anal
ysis of purebred and crossbred poultry covering a five year period.
They used different parental strains of Rhode Island Reds and Barred
Plymouth Rocks each year. Individual pedigree matings were set up with
one half of the females being Rhode Island Red and the other half
Barred Plymouth Rock pullets. During the first two years a male shift
was employed so that all comparisons could be made between paternal
and maternal half-sibs. In the other three years only paternal half-
sib comparisons were possible. They state that there seems to be
little doubt that hybrid vigor for growth rate has been demonstrated
for these crosses.
B. Inbreeding Experiments
A second breeding method that nas been used quite extensively as
a tool for plant and animal improvement is the inbreeding technique.
Mild inbreeding has been practiced in the development of most of our
pure breeds of chickens in the guise of linebreeding. However, in
tense inbreeding, i.e., brother x sister, sire x daughter or son x 10 dam, has been avoided because of the degeneration which accompanies
Inbreeding. Ample evidence is available to demonstrate this degener ation or loss of vigor in chickens (Cole and Halpin 1916, Hays 1923 , Dunn 1923 and 1923, Goodale 1927# Jull 1929# Dumon 1930 and many others).
Plant geneticists were the first to utilize this technique prof itably. Inbreeding of plants results in a loss of vigor in most of the productive characteristics. Inbred lines of maize produced by
Shull (1911) and Hayes and East (1911) were inferior to the randombred parental stock. Seed production of the progeny of some of the crosses between different inbred lines was superior to that of the inbred lines and of the random-bred stock. Many investigators found that the prog eny from crosses of certain inbred lines were superior to the parental stock and to the open-pollinated progenitors of the inbred lines, With these findings# inbreeding rapidly increased as a breeding method about
192U. Only one method was followed# that of continuous self-fertiliza tion coupled with selection within and between progenies of selfed ears.
When measured phenotypically, not one good productive inbred line was discovered. However# many lines possessed an ample sample of yield genes capable of producing vigorous hybrids. The poor performance of the inbred lines necessitated the use of these lines in double crosses.
The basic problem was to determine how to identify the inbred lines that would combine to give the best results.
Topcrossing and incrossing were introduced as breeding techniques for c o m imporvement. Jones (1922), L in os trora (1931) and Jenkins and
Brunson (1932) were able to increase yields considerably by topcrossing 11 inbred lines on commercial varieties* Jenkins (1929) computed corre lations between various characteristics in inbred and crossbred strains of -*aize* Some of the correlations between characters in the inbred parents and the same character in the crossbred progeny were high enough to be of value for predictive purposes. In Lindstrom's (19Jl) work, ne demonstrated that strains of maize inbred for six generations were markedly prepotent for ear type, disease resistance and other economic characteristics. Jenkins and Brunson (1932) concluded that crossing inbred lines with open-pollinated varieties may be used efficiently in preliminary testing of new inbred lines.
Top crosses were used by Jenkins (1935) to determine the perform ance value of inbred lines in crosses. Selection between sister prog enies was effective in choosing the progenies whose crosses were slightly but consistently more productive than those of their discarded sibs. He proposed furtner that selection for performance should be based upon crossing tests ratner than upon the appearance of the paren tal lines. He demonstrated that the characteristic good yield genes in an inbred line are fixed by the second generation of inbreeding and no later selection augments tneir number. Jenkins (1937) thoroughly reviewed the corn improvement program giving results and methods used in the production of inbred lines, single crosses, three-way crosses, double crosses and topcrosses.
Lindstrom (I9I4I) attempted to determine if the poor quality and yield of inbred lines traced to the system of inbreeding used in maize inbreeding programs, i.e., selfmg with the accompanying rapid fixa tion of genes. Since poultry had been inbred (using milder forms of 12 inbreeding than brother by sister mating, see Waters and Lambert 1?>6) for more than twelve generations without serious loss of fertility and vigor, he suggested that possibly milder forms of inbreeding in maize might give better results. Four mating systems were utilized in this study. In one sys tea selfing was used during the first three of eight generations followed by aibbing. A second system utilised sibbing during the first five generations and this was followed by selfing for three generations. The other two systems were intermediate to these extremes. JPheno typically, the progenies of the system utilizing selfing at the end of the experimental period were slightly superior in vigor and size of ear to the progenies of the other three systems.
He suggested that milder inbreeding at the beginning not only would prevent too rapid fixation but would provide a broader base for selec tion under more diverse environmental conditions.
Sprague and Tatum (1?1*2) investigated the phenomena of general and specific combining ability in single cross c u m hybrids. In single crosses involving previously tested lines, they found that genes conditioning specific combining ability have the most effect in determining yield differences, while in untested material genes affeeling general combining ability are of most importance. They demonstrated the importance of specific combining ability as a source of variance among single crosses.
Comstock, Robinson and Harvey (1VU9) designed a breeding system for c o m to make maximum use of both general and specific combining ability. Theoretically this program, reciprocal recurrent selection, is superior to two other current c o m breeding metnods in selection 13 for general combining ability for loci where there is over-dominance and for loci where there is partial dominance. However, they concluded that available evidence indicates that over-dominance i*ay not play too great a role in maize improvement.
Keller (191*9) investigated tne relationship between the use of a related and an unrelated single cross as a tester in evaluating a group of selected plants. Analysts of the data suggested that two testers did not yield similar measures of combining ability as regards the ranking of tne lines. To obtain some iaea of the theoretical number of testers needed to evaluate lines, ne computed the average gain xn combining ability due to the selection of the apparent best instead of a random line from a sample of n lines. He concluded that tne g a m in combining ability beyond the use of eight to ten inbred line testers is very slight.
Recurrent selection for general combining ability provides a means for increasing the frequency of favorable yield genes within a population prior to inbreeding for the extraction of homozygous lines
(JLonnquist 1951)* Lonnquist suggests tnat the method provides greater
efficiency in selection of superior genotypes as well as a higher
level of combining ability in the lines obtained.
Plant geneticists were able to infcreed their material extensively without serious economic repercussions even if tney lost most of the
inbred lines. Animal geneticists were slower to explore the possibil
ities of genetic improvement through inbreeding primarily because of
the degeneration and loss of vigor which accompanies inbreeding.
However, as a result of the phenomenal success of hybridization of corn, animal and poultry geneticists began to explore this technique. Castle
(1916) inbred Drosophila by brother to sister mating for fifty-nine generations in succession without obtaining a diminution in either the vigor or the fecundity of the race. He observed that crossing two inbred strains of Drosophila produced offspring superior in productive ness to either inbred strain. King (1918 and 191?) inbred albino rats for twenty-eight generations of brother to sister mating. The vari ability in body weight of the fifteenth generation of inbred males and females was about UO percent less than the control animals. East and
Jones (1919) summarized the results of matings of close relatives among plants and annuals. In general, tnere is a decrease in vigor of most economic characteristics studied. Variability in most of the characteristics of the inbred plants and animals decreased progressive ly during the course of inbreeding until a level of comparative uni formity is reached. East and Jones interpreted these effects of inbreeding as due to the specific inheritance received, rather than to tne fact of close blood relationship among the individuals mated.
Wright (1922 a and 1922 b) inbred guinea pigs for twenty genera tions of brother to sister mating. He found that there was an average decline in vigor in all characteristics during the course of thirteen years of inbreeding. He conducted extensive experiments in which different inbred families were crossed. It was shown that crossbred guinea pigs from unrelated inbred parents are distinctly superior to their inbred relatives in nearly all elements of vigor. Wright (1922 c) concluded that there are two classes of effects which are ascribed to inbreeding. First, a decline in all elements of vigor, as weight, 15 fertility and vitality, and second, an increase in uniformity within the inbred stock, correlated with which there is an increase of pre potency in outside crosses*
The Minnesota and Iowa Experiment Station workers were pioneers in swine inbreeding* A review of the Iowa work is given by Dickerson,
Lush and Culbertson (191*6) j Hazel, Mus son and Lush (191*3) and Hetzer,
Hankins and seller (1950)* In inters et al (19JO) made a survey of
inbreeding research being carried on at various experiment stations*
Winters et al (191*3) and Winters et al (191*6) reported on swine in breeding experiments which were conducted at the Minnesota Station*
Eaton (191*1) made reciprocal crosses between inbred strains of mice and some backcrosses to one of the original parents or to a third
inbred strain* He found that crosses between some inbred strains
showed increases over the inbred parental lines in growth, viability and fertility while others were incompatible in crosses. Combination
of three inbred strains gave a greater increase in the criteria of measurement than combinations of two strains* This he attributed to
greater general vigor of the hybrid dam* Eaton, Neville and
Dicxerson (1950) investigated general ana specific combining abilities
in 72 crosses among nine inbred strains of mice. They found evidence
of little dominance for genes influencing weight in the mouse*
Kobertson (191*9) reviewed results of inbreeding experiments in
dairy cattle. In general there is a decrease in size, vigor, milk
and fat production during the process of inbreeding.
The influence of inbreeding on various characteristics of repro
ductive performance in chickens has been investigated extensively* 16
This literature will be reviewed separately under the various divisions of this paper*
While the literature on egg production and natchability is volumin ous, the amount of work that naa been done on the influence of inbreed ing on growth and body weight is rather meager* Dunn (1923) presented an account of the effects of inbreeding in White Leghorns. Six inbred lines were established by full brother by sister mating for three years.
The basis of selection was the number of full sisters available for mating on February 1 of the pullet year. He expressed rate of growth to three weeks of age as the number of times the chicks increased their hatching weight* Ho data are available on the first generation but in the second and third generations the inbreds grew at a rate of
2.03 and 1*91 as compared with 2.21* and 2.36 for the controls. He observed various other characteristics but concluded that one of the most striking effects of close inbreeding was to lower the rate at w m c n growth and development normally proceeds. Dunn (1926) reported on the effect of inbreeding and crossbreeding upon the domestic fowl.
Thus classical account of inbreeding in White Leghorns describes the
deterioration and ultimate extinction of most of the inbred lines.
Crosses were made between three inbred families. The comparison of the
inbred with the outbred progeny from the same families showed that the
cross had an immediate effect on the growth rate of the outbred chicks.
The substitution of another equally inbred male for the dam's own
brother was shown to increase the productive level, although it was
noted that the amount of this heterosis varied among different families. 17
Hays (1923) continued Goodale's (1919) investigation of the effects of inbreeding on a strain of Rhode Island Reds* He made parent x offspring, brother x sister and more distant matings for three successive generations* He observed that variability in body weight at sexual maturity was not affected by inbreeding. Qoooale
(1927) observed no decline in body weight at sexual maturity after five generations of brotner to sister mating in White Leghorns.
Dunkerly (1930) found little difference between the average weights at maturity of inbred and outbred progeny. Hays (1935) reported that tne daughters of inbred males were heavier at sexual maturity and less variable than daugnters of non-inbred males.
In a report on ten years of inbreeding of White Leghorns in which the degree of inbreeding was less than brother x sister mating, Waters arid Lambert (1936) concluded that inbreeding did not materially de crease nor increase growth rate and adult body size, delection of breeding stock was based on high hatchability, large family size and good vigor. Haw (19i*2) found that tne inbreds were about two hundred grams lighter at sexual maturity than tne control Legnomsj however, there was considerable family differentiation with respect to body size. Knox (191*6) was able to produce inbred lines of White Leghorns and Rhode Island Reds by practicing rigid selection throughout the inbreeding period that showed no decrease in mature body weight when compared to random-bred birds of the same breed, dhoffner (191*0 a and
191*3 b) working with adult body weight determined by tne regression technique that inbreeding has little effect on this variable. 18
Apparently Maw (1?U1 and 191*2) was one of the first to collect growth uata in topcrosslng experiments in chickens. Inbred families of one strain were intercrossed and outcrossed to inbred birds of un related stock. Single, three-way and double crosses were also made between families having low and high degrees of relationship. With respect to growth, the data show that while the progeny from crosses between related families exhibit but little improvement over the paren tal lines they tend to vary according to the degree of relationship between the parents. Topcrossing gave better results than crosses between the inbred lines when some relationship existed between the
inbred lines. The topcross and incross progeny were significantly heavier in adult weight than the inbred progeny.
Brother x sister matings of Wnite Legnorns, Rhode Island Keds ana
White Wyandottes were made by Pease (191*6) in an attempt to find a
line which would stand up to this degree of inbreeding. After five years of inbreeding all but one line of White Legnorns had degener ated to such a point tnat tney naa to be discarded. Five lines were
developed from this one remaining white Legnom line and these were
crossed in all combinations. The incrosses were significantly lighter at sexual maturity and final body weight than the outbred controls.
He observed that body weight and rate of growth remain very variable
after inbreeding. From a study of the coefficients of variability of five economic characteristics considered in this experiment, Pease
concluded that the basis of selection adopted led every year to pick
ing out the most heterozygous birds for breeders. He theorized that
if this is so it would seem that the capacity to thrive and leave a 19 large progeny is partially dependent on heterozygosity of several genes which express than selves in rate of growth, body weight and other characteristics*
Dudley and Pease (l?Ud) tested the topcrossing technique as a method of improving productivity of commercially ored poultry* Since
it was not feasible to mate inbred and outbred males alternatively
to tne same set of females, a group of sisters were selected and di vided into sets of four* Then an inbred and outbred male were each mated to four females, the eight females being sisters* Weight at
sixteen to twenty weeks of age for the topcross pullets was in every year lighter than corresponding outcross pullets. Final adult weight of the topcross pullets was less than that of the outcross pullets*
Progeny result-ing from six crosses involving seven inbred lines
were tested by ttaw (1?U9J« body weights at eight weeks of age for the
incross females ranged from 537 to 701 grams as compared to 623 to 6b 7
grams for the controls* None of the differences in weight at this cr
any of tne other weighing periods were significant*
Glazener and blow (155G and 1551) mated males from eight inbred
lines to non-inored hew nampsnxre, Barred Plymouth hock, White Plymouth
Hock, Rhode island Ked and White Leghorn females. Sixteen topcross mat
ings in all were made. The topcross progeny were compared with inbred
progeny of the lines from which the sires originated. Tney found the re
gression of topcross performance on inbred performance was positive and
significant for ten week weight and for featnering* A significant line x
tester interaction for broiler weight and for hatchability was reported 20 by these investigators* This suggests that the role of dominance and gene interactions cannot be overlooked in the inheritance of ten week body weight* They concluded that hybridization has only a limited place in a broiler program as compared with the possibility of hybrid poultry for egg production*
Mueller (1950 and 1952) made a comparative study of commercial inbred-hybrid chickens and first generation crossbreds from non-inbred stock* Five different lines of inbred-hybrids were purchased as chicks from various breeders* The crossbreds were from reciprocal crosses made between White Leghorns and New Hampshires and between White Leg- noras and White Plymouth Kocks* The birds were intermingled through out the entire test* Body weights of the crossbreds were significantly heavier at eight weeks of age and at housing than the inbred-hybrids but this probably reflects the selection for growth rate in both heavy breeds. The coefficients of variability of eight week body weight were low ranging from 9*5 to 16*2 percent* No statement is made rela tive to the observed variation in body weight of the inbred-hybrids and the crossbreds as separate units*
Dickerson et al (1950) crossed twenty-one families of inbred lines of White Leghorns, six families of New Hampshires, two families of
Khode loland Keds and sxx families of Wnute Plymouth Hocks in 227 of
1*62 possible crossbred combinations of White Leghorns with the other breeds* In addition, IjJ of 265 possible intra-breed combinations were made* Compared with the mean of the parental intra-breed crosses, the crossbreds weighed four to seven percent more at eight and twelve weexs of age* Compared wuth their reciprocals, the crossbreds from 21 matings involving White Leghorn males were superior in growth to eight and twelve weeks of age.
Hales of thirty-three inbred lines were topcrossed to the same two openbred stocks (at different experiment stations). The eggs were sent to the Regional Breeding Laboratory at Lafayette where tne stock was hatched and grown together. Hoore and Warren (1951) found a tendency for the more highly inbred males to show lesser variability of growth rate in the topcrosses with one openbred stock but not the other. Purebred stocks and commercial hybrids reared under the same conditions as the topcrosses both showed mean vari abilities of growth greater than the mean of the topcross.
Glazener, Blow, Bostian and Dearstyne (1951) analyzed data collected on 50d0 chicks hatched from three inbred strains of New
Hampshires and two inbred strains of Barred Plymouth Rocks over a five year period. They found that genetic variability in body weight at twelve weeks of age was not consistently reduced as maternal de gree of relationship increased. The regression of inbreeding on twelve week body weight was -0.1297* Thus for every ten percent in crease in the inbreeding coefficient a decline in weight of approxi mately 1.3 ounces would be expected. They concluded that if rigid selection for growth rate is maintained inbreeding may proceed as rapidly as possible without effecting a decline in broiler weight.
Variation in body weights as a function of growth was measured by Bell and Baldini (1951) from hatching to ten weeks of age in inbred, single cross, double cross, crossbred and openbred chicks reared on two different types of rations. They found that the single cross 22
progeny of two inored lines were the most uniform in growth of all
the various kinds of chickens tested, whereas, the greatest variation
as measured by the coefficient of variability was observed among the rcm-tnbred varieties.
Waters (1951) reported on the body weights of ten month old
fanales of six inbred lines of White Leghorns. He concluded that
intensive inbreeding per se will not necessarily decrease the defini
tive body weight of chxcKens. By practicing rigid selection for body
weight he was able to maintain this variable and in some instances
body weight at ten months of age was increased.
Maw (1952) investigated the possibility of obtaining a greater
degree of uniformity in growth and body type by topcrossing. Inbred
families of Barred Plymouth Rocks and Hew Hampshires were developed
and each year males from these lines as well as random-bred males were
mated to random-bred females in either purebred or crossbred matings.
In the Barred Plymouth Rock male by New Hampshire female matings, the
male progenies of the inbred males in all years except 19U9 were
slightly heavier tnan tnose from the ranoom-bred males. The female
progenies of the inbred males in all years except 1950 were slightly
neavxer tnan those from the random-bred males. In the reciprocal of
tnis mating type only some of the progenies of the inbred males were
heavxer than the progenies of the random-bred males. There was no
evidence from any of the comparable matings within years to show that
inbreeding of the male parent had any effect on the variability of
the topcross progeny. He concluded that factors other than the 23 breeding method evidently determines a large amount of the variabil ity in early body weight*
Topcross matings were made by Wyatt (1953) using sires from five inbred lines of White Leghorns on female progeny from five non-inbred crosses. He found little relationship between topcross performance and inbred performance for eight week bocy weight. This suggested to
Wyatt that additive genes contrioute little to the variance between lines. He observed that the different tester females faxled to rank the inbred lines in the same order as measured by the mean performance of tne topcross progeny. This, he believed was further evidence against additive genes playing a major role in the total variance of early growth. Analysis of variance of the data revealed that the lines exhibited no difference in general combining ability for any of the traits studied. He concluded that the observed differences between tne inbred lines are due largely to non-additive factors*
Data collected over a six year period on one inbred line of White
Legnorns and two inbred lines of New Hampsnires were analyzed by Blow ana Glazener (1953). Tney found no significant change in performance for body weight at sexual maturity with increases in inbreeding* II. Egg production
The literature on variation in egg laying capacity is too volumi nous to be reviewed completely in this paper. An excellent review of tne subject nas been made by Hutt and more recently by Jull
. In general, only the literature dealing with comparative studies between strains, breeds, crosses, incrosses, topcrosses and incrossbreds will be considered.
A. Crossbreeding Experiments
Crossing breeds with a view toward increasing egg production in tne crossbred progeny has not been practiced to the same degree as crossbreeding to increase early growth in crossbred broilers. In the
Mid-West and Eastern sections of the United States, crossbred females have been used rather extensively as egg layers. In the former area, the austra-White nas been used widely in farm flocks, while in the latter area the black-cross nas been very popular.
Early work by Pearl and Surface (lyiO) indicated that Black-cross pullets from a Cornish x Barred Plymouth Kock mating were poor winter egg layers, while the Barred-cross puliets from the reciprocal mating were good winter egg producers having about the same production as
tne purebred Barred Plymouth Bocks. 2k 25
Warren (1927) reported that crossbred pullets from reciprocal matings of White Leghorns and Jersey Black Giants were definitely superior to either parental breed in average egg production* The hybrxds averaged 39*1 eggs more than the better of the two parent breeds (White Leghorn) and exceeded the production of the Jersey Black
Giants by 50.6 eggs. The differences in both cases were statistically
significant. Warren (1930 and 19U2) summarized his extensive cross
breeding experiments. Reciprocal crosses between various breeds were
made in 1928, 193U* 1936, 1937 and 1939* In 1928, the crosses were
made between White Leghorns and Rhode Island Reds. Hales of each
breed were rotated weekly in the pens producing crossbred and pure
bred progeny which were naif brothers and sisters. Although the two
breeds differed widely in annual egg production, the mean annual egg
production of the crossbreds was similar to the Leghorns, the cross
involving the Legnom male being better. Crossbred pullets from the
Legnom sire were approximately the same age at sexual maturity as
the Leghorns, wnile the females from the reciprocal mating were inter
mediate between the two breeds witn respect to age at maturity. The
matings of 1936 involving different strains of White Leghorns and
Knode Island Reds gave essentially the same results. The crossbreds
from tne White Leghorn male x iuiode Island Red female were outstand
ingly good egg layers surpassing the best purebred breed (Rhode Island
Red) by 2U eggs. The White Leghorn strain was relatively late maturing
and the Rhode Island Red strain was relatively early maturing. The
crossbreds from both crosses were very similar and intermediate between
the two breeds in age at sexual maturity. 26
The 193U flock matinee were between White Legnorns and Austra- lorps. In the cross where the Australorp was used as the sire, egg production was similar to the White Leghorns (the superior parental breed), while the pullets from the reciprocal mating were markedly superior in annual egg production. Age at sexual maturity of the crossbred pullets of both reciprocal matings was much like that of the
White Leghorns.
The crossbreds from the reciprocal matings of 1937 (White Leghorn x New Hampshire) were similar in egg production and on an equality with tne White Leghorns. These two breeds differed widely in age at first egg. The crossbred pullets were intermediate to the parental breeds.
In 1939* matings between Rhoae Island Reds and Barred Plymouth
Hocks produced crossbred pullets that laid more eggs than either of the parental breeds. The pullets from the Knode Island Red male x
Barred Plymouth Rock female mating laid 10 eggs more than the pullets from the reciprocal mating and 20 eggs more than the Rhode Island Reds.
Tne crossbred pullets matured earlier than the pullets of either pure breed.
Warren produced a three-way cross by mating males of a single cross (Rhode island Red x Barred Plymouth Rock) with White Legnom females. A Wnxte Legnom strain cross was used as the control stock.
The White Leghorn strain cross pullets nad a mean annual egg produc tion of 211 eggs as compared wxth 215 eggs from the three-way cross breds. The strain cross pullets came into production 7 days earlier than the three-way crossbreds. 27
Barred Plymouth Rock male* were flock mated by Warren to females of three strains of White Leghorns in an attempt to determine the influence of the quality of the pure breed upon the resulting cross breds* The females in each mating pen were equally divided among the three strains of Leghorns. Strain W, £ and K averaged 221* 162 and
180 eggs, respectively, while their crossbreds had a mean annual egg production of 221, 227* and 219 ogga, respectively. Warren observed that for most of the characteristics studied there was a striking improvement of the crossbreds over their respective purebreds.
In order to determine if strain crossing produced a stimulating effect in the same manner as breed crossing, Warren mated strain W
White Leghorns with strains £ and K in reciprocal matings in two breeding seasons. The strain cross pullets from the W x K mating laid considerably better then either parental strain. When the lower producing strain £ was used, the strain crosses did not lay as well as the pullets from the other cross but they did lay more than the pure strains involved in the cross.
The results of Warren's work warrant the following summary state ments:
1. Egg production of the crossbreds was equal to or better than that of the better producing purebred parent.
2. Not all crossbreds were superior egg producers.
3* The level of production of the crossbreds is conditioned by that of the parental breeds.
U. There is more heterosis for egg production in breed crosses than in strain crosses.
m 28
5* Three-way crossbreds are satisfactory egg producers but they are no better than most first generation crosses.
6. When early and late maturing strains are crossed, the progeny will be intermediate to the parental breeds.
Knox as quoted by Knox and Olsen (1938) found that the F^ hybrids from crosses between White Plymouth Rocks and White Wyandottes and between White Leghorns and Rhode Island Reds did not attain the pro duction of the Reds or Leghorns* The strains of Reds and Leghorns were good producers averaging 200 and 225 eggs, respectively* Knox and Olsen (1936) observed that the progeny from crosses of "general purpose" breeds, on the average, produced more eggs than the progeny from crosses involving White Leghorns* The best crossbreds for egg production were those obtained from crosses between Rhode Island Reds and White Wyandottes and between Rhode Island Reds and Barred Plymouth
Rocks. However, their data showed that the average crossbred did not lay as well as did the average of the Rhode Island Red and White
Leghorn stock* The crossbred progeny were older at sexual maturity and had almost twice as much broodiness as the purebreds* Three-way
crossbreds were obtained by mating White Wyandotte males x F females 1 (R.I.R. x Light Sussex) and by crossing Light Sussex males x F1 females
(R.I.R. x White Wyandotte). Neither of these groups laid as well as
the single cross pullets from a Rhode Island Red x White Wyandotte mating* They concluded that the quality of the parental stock has
considerable influence upon the quality of the crossbred progeny*
Jeffrey (1939) in a crossbreeding experiment which was repeated
in two successive years found that the crossing of a poor production strain of Rhode Island Reds with a good laying strain of Barred
Plymouth Rocks produced progeny that were intermediate or inferior to the pure breeds in laying house mortality and eleven month egg production*
Crosses between Barred Plymouth Rocks, New Hampshires, Rhode
Island Reds and White Leghorns were made by Bostian and Dearstyne
(19U2) so that comparisons could be made between purebred and cross* bred progeny that were half-sibs. They observed that the crossbred pullets performed better than their respective purebred half-sibs.
The pullets from the New Hampshire x Barred Plymouth Rock mating
averaged 22 eggs more than the purebred New Hampshires and 29 eggs more than the Barred Plymouth Rocks. Pullets from the White Leghorn
x Rhode Island Red and the White Leghorn x Barred Plymouth Rock mat
ings exceeded the purebred Leghorns only slightly in egg production.
A comparative study of Rhode Island Reds, White Wyandottes, Light
Sussex and crosses among them to produce and three-way cross progeny
was made by Knox, Quinn and Godfrey (19U3). Mass-mated Rhode Island
Red pullets were used to measure the performance of the two- and three-
way crossbreds. No selection was practiced in the production of the
crossbreds* The average number of eggs laid by the Light Sussex,
White Wyandottes and Rhode Island Reds was 13?.9, 15U.3 and 16?.6 eggs,
respectively. The four year average production for crossbred pullets
from the R.I.R. x Light Sussex and the R.I.R. x White Wyandotte mat
ings was 171.5 and 162.3 eggs, respectively. The two year average
production for the three-way crossbred pullets from the White Wyandotte 30 male x female (R.I.R. x Light Sues ex) mating was 161*1 eggs, while that for the pullets from the other three-way cross was 152*1 eggs*
Thus as far as this experiment is concerned there is little to be gained in egg production by crossbreeding* However* they concluded that it is quite possible that the stock used in these crosses lacked the essential factors for producing outstanding crossbreds*
Knox* Gordon arid Mehrhof (191*?) reported on the performance of
Rhode Island Reds and Light Sussex as compared with that of their F-^ and three-*ay crossbreds* This is a continuation of Knox* i^uinn and
Godfrey's earlier work* however* the pullets were selected on data to
February 1 subsequent to year of hatch* White Leghorns and Barred
Plymouth Rocks were used in the production of three-way crossbreds*
The average egg production of the crossbred pullets* on the average* was significantly better than that of the progeny of the standardbred stock used in the same cross* These data vary from previous data cited above* They believe that the differences are possibly due to use of unselected mass-mated pullets in the first report and selected mass-mated pullets in the current test*
Dudley (1
Island Red and White Leghorn breeds of poultry. To minimize effects
due to different parentage* purebred and crossbred chicks were pro
duced from the same females* The average annual egg production of
the crossbred pullets was slightly higher than that of the purebred pullets but the difference was not significant* The average annual
production for the Rhode Island Reds* Whxte Leghorns and pullets from the W.L. x R.I.R. and R.I.R. x W.L. mat Inga was 197* 194, 204 and 197 eggs, respectively.
The data of Knox (1950) for first year egg production of progenies secured from outbreeding and crossbreeding indicate that crossbreeding
is beneficial. The two year average egg production was 209 for the outbred Rhode Island Reds and 2ol for the outbred White Leghorns, while
comparative figures for pullets from a R.I.R. x W.L. mating was 213
eggs.
Eight strains from four breeds (New Hampshire, Rhode Island Red,
Barred Plyuiouth Rock and Australorp) were mated by Qhostley and Nord-
skog (1951) in all possible combinations. The strain and breed crosses
laid 9 percent more eggs and matured 10 days earlier than the pure
strains.
Using different parental strains of Rhode Island Reds and Barred
Plymouth Rocks each year, King (1951) and King and Bruckner (1952)
found that the Barred-cross pullets were significantly better than the
Black-cross pullets for either of the parental breeds for survivors'
500 day egg production in 3 of the U years. The average four year
advantage of the Barred-cross was 21 eggs over the next highest mating.
The Black-cross pullets were no better than the better purebred parent
in any year. With respect to age at first egg, the Barred-cross
pullets were significantly earlier (one week) than the purebreds or
the Black-cross pullets. They concluded that there could be little
doubt that hybrid vigor ahd been demonstrated for egg production.
They suggested that the interaction effect could be due to sex-linkage. 32
Comparisons of productive performance were made by Brunson and
Godfrey (1951) among Rhode Island Reds, Barred Plymouth Rocks, White
Leghorns, F^ progeny of a Rhode island Red x Barred Plymouth Rock mating, and F^ progeny of a White Leghorn x Black-cross mating. In the first year of the test, the Black-cross pullets were superior to the other breeds and cross in egg production. The three-way cross pullets showed a lower rate of production than either parent. The
Black-cross pullets in the second test laid at a rate below that of either parent, while the three-way cross pullets were superior in performance to either parent. Their data f a n e a to snow that egg pro duction can be consistently improved by crossbreeding.
Glazener et al (1952) mated females of one breed to a male of the same breed and a male of a different breed in a diallel breeding scheme. In the first year, the same sires were used during the entire hatching season but in the second year a different sire was used for each natch. Mean differences between purebred and crossbred pullets were estimated separately from the data on offspring of each pair of sires, i.e., a pair of sires consists of two males of different breeds
that were mated to the same set of dams. By comparing the performance
of the purebreds and crossbreds by specific cross, they found that 12
out of the 15 groups of crossbreds were equal or superior to their
corresponding purebreds for six months' egg production.
B* Influence Of Inbreeding On Egg Production
Reports on the influence of inbreeding on egg production vary
considerably. However, this sort of thing would be expected by the very nature of the inbreeding technique. Inbreeding increases the number of homozygous pairs of genes in the inbred stock* Deleterious genes as well as favorable genes are fixed in a like manner* Fixation or increased frequencies of detrimental genes would result in decreased performance, while fixation of desirable genes would account for favor able performance in inbred stock* This type of phenomena would explain why one investigator could report adverse findings, while another could maintain or possibly increase the productive xevel of his inbred mate rial* A second feature of inbreeding is that of decreasing heterozy- gosity. This tends to make the inbred population more uniform and to differentiate families and lines* There is ample evidence to demon strate family and line differentiation with respect to egg production as inbreeding is continued over a period of time but the expected in crease in uniformity is not as evident*
One of the first inbreeding experiments utilizing poultry as the biological material was conducted by Cole and Halpin (I?l6)« They in- bred Rhode Island Reds by brother x sister mating for four successive years* A marked decline in vigor occurred* Hatchability reached
such a low level that the experiment had to be discontinued in the
fourth year* The only selection that was practiced was based on the
color of the plumage on the back of the birds and on the number of
progeny* Another experiment was started with Rhode Island Reds in
which full brother x sister matings were made (Cole and Halpin, 1?22)*
delection in this experiment was based on hatchability and livability.
Egg production during the first three generations decreased rather
markedly* Dry den (1915) reported that inbreeding resulted In fewer eggs and more variation among individuals* Inbreeding, he states, did not fix the characters for uniformity of egg production* However, he did not report either the degree of inbreeding, other than some dam x son mating, or the sise of his experiment*
Goodale (1919) reported that fecundity had no necessary relation ship with the degree of inbreeding since from inbred or outbred mating?, good or poor egg producers might appear depending on the individuality of the mothers* However, the data reported in this experiment were based on only one generation of inbreeding* Goodale stated that in his experience the best egg producers are obtained from outcrossing rather than from inbreeding*
Dunn (192j) observed a marked decrease in hatchability and egg production after three years of inbreeding White Leghorns* Selection was base a on the number of full sisters available for mating on Febru ary 1 of the pullet year* Winter egg production in the generation was less than one-thxrd that of the parent stock and about one-half
that of the controls* In the F2 generation, winter egg production was 6 eggs for the inbreds and 13 eggs for the controls* In the first
generation, the average age at maturity of the inbreds was 260 days
and in the second generation it was up to 276 days* Corresponding
figures for the controls were 23U and 2U2 days* Fart of the decrease
in production, Dunn suggested, could be due to the increased age at
sexual maturity* Dunn (1928) compared inbred with outbred progeny
from the same families and observed that the outbred chickens were
superior in egg production to their inbred half sisters* 35
Hays (1923) studied the effect of varying degrees of inbreeding
(parent x offspring, brother x sister and more distant matings) on
winter egg production In Rhode Island Reds* His data indicated that
winter egg production tends to decrease under close inbreeding, due to
retardation of sexual maturity and decreased winter rate of production*
Hays states that inbreeding reduces variability in winter egg produc
tion only when the foundation stock is largely homozygous for factors
determining heavy egg yield* He concluded that winter egg yield
showed a tendency to decline after the degree of inbreeding passed
25 percent. Hays (1929) conducted another series of experiments from
1923 to 1929* There were from U to 28 inbred matings each year in
this test* His results Indicated that birds of diverse ancestry
could be inbred with greater safety than those of restricted ancestry.
- Age at sexual maturity was not retarded consistently. There was a
consistent decrease in annual egg production as inbreeding increased*
Hays observed that the piysiological factors determining egg produc
tion, i.e., early maturity, intensity, persistency and pauses, did
not become more uniform as inbreeding increased in the restricted
ancestry group, but the control birds, which had more diverse ancestry,
did become more uniform when inbred.
Systematic brother x sister matings were made by Qoodale (1927)
with varying degrees of success. No difficulties were encountered
in the first generation but thereafter egg production dropped drasti
cally. The offspring of the first mating of brother x sister had an
average annual egg production of 22k eggs. The average egg production 3 6 of the second generation pullets was 113 eggs, while the fifth genera tion pullets averaged H I eggs. Age at first egg was not adversely influenced by inbreeding.
Dunkerly (1930) inbred White Wyandottes, Rhode Island Reds and
White Leghorns from 1925 to 1926 by making a brother x sister mating followed by father x daughter matings. Also, fathers were mated to daughters whose ancestry was outbred. The results of his experiment
indicates that production or maintenance of high fecundity is more lively to result from outbreeding than from either of the two types of inbreeding employed. In most cases, age at sexual maturity was
significantly higher for the inbred birds than for the controls.
Inbred families of White Leghorns were produced by Jull (1933)
by mating males to their full and half sisters. The inbred stock was intercrossed after three years of inbreeding. Inbreeding resulted
in an increase in age in days to laying, a decrease in the rate of
laying during the first fifty days of production and & decrease in
the total first year production. The parent stock laid 25 eggs
during the first $0 days of production, while the progeny laid
15 eggs. Annual egg production decreased from 168 eggs for the dams
to 76 eggs in the third generation of full sib matings. Jull suggest
ed that thxs decrease is largely due to slower sexual maturity and
decreased rate of production. The intercrossing of the inbred progeny
resulted in a marked increase in egg production. He suggests that
this intercrossing brought together complementary genes.
Three inbred lines of Rhode Island Reds were established by full
brother x sister and half brother x sister matings (Hays, 193U)» His 37 data showed that inbreeding retarded sexual maturity, reduced inten sity of production and consistently reduced annual egg production without reducing its Tar lability* When he crossed the inbred lines, the incross pullets matured earlier and had a higher annual produc tion than the inbred pullets* Hays reported that in no respect did the inbreds or incrosses surpass the general flock*
Hays (1935) produced inbred Rhode Island Red males from brother x sister, half brother x sister, sire x daughter and son x dam mat ings* Hales from these matings along with non-inbred males were mated to non-inbred Rhode Island Red females. A total of 11 inbred males and 36 non-inbred males were used in the three year test* Hays anticipated that the results of the topcross in g would be increased homozygosity for the genes controlling fecundity characters and the absence of deleterious effects of inbreeding on high production* The progeny of the inbred males matured 7*2 days later than the progeny of the non-inbred males* There was no reduction in variability of winter and annual egg production* Both winter and annual production were significantly lowered by the use of inbred males*
Waters and Lamberts (1936) data showed that inbreeding over a
ten year period has little effect on egg production for the winter
months. They observed a marked decrease in egg production for the
first 200 days of laying as the inbreeding coefficients increased
from 0 to 50 percent* The change in inbreeding from $0 to 70 percent
was accompanied by a slight increase in 200 day production* Annual
egg production showed a general but not consistent decrease over the
10 year period. They reported that the more intensely inbred birds 3a matured sexually 1 6 days earlier, on the average, than birds of the original non-inbred foundation stock.
Crosses between inbred lines of White Leghorns were made by Haw
(191*1 and 191*2). The data showed that the randombred Leghorns laid
to March 31 approximately 20 percent more than the inbreds* The pro
duction of all of the crosses exceeded that of the inbreds but only
one single cross between unrelated lines and the topcross birds stir-
passed the production of the randombred Leghorns. The topcross
pullets matured earlier than the randombred Leghorns and most of the
Inbred crosses* Maw concluded that crossing of unrelated lines ap
pears to offer the best opportunity of using inbreds in securing
increased production*
Knox (191*6) crossed inbreds of high coefficients of inbreeding
with inbreds of the same breed and variety, with inbreds of a differ
ent breed and variety and with outbred stock of the same breed and
variety* Rhode Island Reds and White Leghorns were the stock util
ised in this study* The data indicate that inbred lines may be
produced without a decrease in annual egg production, however, many
lines were discarded because of poor productive performance* He
found that the progeny produced from inbred Rhode Island Reds mated
to White Leghorns gave superior results in annual egg production to
the purebred White Leghorns and Rhode Island Reds* They averaged
26 to l*ti eggs more than the Rhode Island Red pullets and in all but
one year laid 30 to 1*1 eggs more than the White Leghorn pullets* The incrosses and topcrosses did not lay as well as the in crossbreds but
were on an equality with the outbred Reds and Leghorns* 39
Dudley and Pease (191*8) reported that topcross pullets laid hut
1*3 eggs more (hiring i*Q-l*l* weeks of production than their half sisters from an outbred mating* Likewise, the topcross pullets came into production about 6 days earlier than the outcross pullets* These differences are not significant* Pease (!9i*o) made crosses between
5 inbred lines of White Leghorns* in egg production for 1*1* weeks, tne incrosses differed decidedly among themselves and these differ* ences were usually consistent from year to year* There were no marked differences among the incrosses in age at first egg*
Regressions of egg production rate on inbreeding of the dam and on inbreeding of the offspring were calculated by Wilson (191*8) on an intra-sire, intra-year basis* The corresponding values are -O.li* and -0.06. The former value would signify an average reduction of
1*1* percent in egg production rate for each 1 percent increase in inbreeding*
Shoffner (19l*8 a) reported on the variation wxthin an inbred line of White Leghorns* The in breeding coefficxent of this line had reached 60 percent* Five characteristics of productive perfoxmance
(egg proauction, sexual maturity, hatchability, egg weight and body weight) were studied. Tnere was no obvious tendency for the coeffi cients of variation to decline as inbreeding progresses. Shoffner concluded that reduction in variability due to inbreeding whxch ex ceeds 50 percent is so small as to be of little practical importance*
Shoffner (191*8 b) reported that the within sire regression of the mean egg production of sister groups on mean inbreeding was -0*926* 1*0
A decrease of 9 eggs would be the anticipated result for each 10 per cent increase in inbreeding*
Maw (19l*9) made crosses between seven inbred lines which were susceptible or resistant to lymphomatosis* There was little differ ence in annual egg production between the crosses* The average production of the crosses was lower than that of the high producing control strain*
Inbred families of Leghorns, New Hampshires, Rhode Island Reds
and White Plymouth Rocks were crossed in 227 combinations of Leghorns with other breeds and in 133 intra-breed combination (Dickerson, et al,
1?£0). Compared with the mean of the intra-breed crosses, the Leghorn
x Hampshire and Leghorn x Red crossbreds laid S-9 eggs more during a
production period from 15U to 300 days of age* Crossbreds by Leghorn
males were superior to their reciprocals in egg production to 300
days* Outcrossing consistently improved adult viability and egg pro
duction when compared with progeny from intra-flock matings*
Stephenson and Nordskog (1950) and Stephenson, Wyatt and Nordskog
(1953) studied the influence of inbreeding on egg production in the
domestic fowl* The study was based on egg production records of
9,999 individuals from 23 inbred and 3 non-inbred lines collected
over a period of 15 years* The effect of inbreeding on egg produc
tion was found to be non-linear for inbreeding coefficients under 25
percent and essentially linear above 25 percent* The general regres
sion of egg production rate on percent inbreeding was reported as
-o*l43* Various lines departed significantly from this general re
gression value. Ill
Duzgiines (1950) reported that different inbred lines of White
Leghorns selected for characteristics not directly related to repro ductive fitness behave in a variable fashion so far as reduction in fitness is concerned. Egg production during the hatching season was lowered as a result of inbreeding in two lines in which no selection was practiced for high egg production* while it was increased in lines selected for high and for low egg number in November.
Mueller (1950 and 1952) reported that crossbred pullets laid at a higher rate (hen-day) than inbred-hybrid pullets until April but
then this superiority was reversed. Average age to first egg was
19b-6 days for the crossbred pullets and 200.U days for the inbred-
hybrid pullets.
Reciprocal crosses were made by Hutt and Cole (1952) in succes
sive years between two mildly inbred strains of White Leghorns. Ge
netic variability was reduced by mating each male concurrently with
20 females* half of nis own strain and half of the other strain. Egg
production was consistently higher for the crosses in 8 of the 9
families* the average increase for all nine being 22 eggs. The
crosses began to lay about 5 days earlier than their purebred half-
sibs. They concluded tnat one effect of heterosis is to induce
earlier sexual maturity and that another is to cause a higher rate
of production after laying has started.
A decrease in egg production and hatchability and an increase
in age at sexual maturity due to inbreeding a strain of White Leg
horns and two strains of New Hampshires was reported by Blow and
Glazener (1953)• The regressions of age at sexual maturity and of 1*2 egg production for first six months on inbreeding coefficients were
0.315 and -0.302, respectively.
Wyatt (1953) topcrossed sires from 5 inbred lines with females
from 5 single non-inbred crosses. He observed but little difference
between the progeny of the crosses with regard to egg proauction.
The different crosses failed to rank the inbred lines in the same
order as measured by the mean performance of the topcross progeny. XIX• Albumen Quality
The literature pertaining to egg- and albumen- quality is rather large* Wilhelm (1939) presented a comprehensive review of the egg quality literature. Hutt (19U9) and Jull (1952) have also reviewed tne literature rather thoroughly* In this paper we will be concerned only with the genetic portion of the literature and with reports on performances of strains or breeds relative to albumen quality*
Since interior quality of the egg is of utmost importance to the consumer, egg producers and poultry breeders are interested in know ing what factors determine egg quality and to what extent these fac tors may be fixed or altered by breeding methods.
Holst and Almquist (1931) have demonstrated that the percentage of firm albumen is a characteristic of the individual hen* Lorenz,
Tayior and Almquist (193U) were able to establish lines of chickens which were characterized by high and low percentages of firm albumen*
The progeny of the high line produced eggs which contained 66*7 per cent firm white, while the average percent of firm albumen in 523 eggs laid by the progeny of the low line was 57*2 percent* The dif ference between the two lines is highly significant, however, an unselected group of chickens produced eggs which contained 56* U percent firm albumen*
143 U k
Lorenz and Taylor (19U0) reported that continued selection for high and low percent of firm albumen failed to increase the differ ence between their high and low lines until the last year of the experiment, when the low line was significantly lowered. Crossing the high and low lines gave intermediate F-^ progeny and back-cross ing produced progeny that were intermediate between the and the parental generation. However; the progeny resembled the oam' s line more than the sire*s line. They proposed that multiple factors are involved but their data deviates slightly from the classical concept of multiple factors in that the variation in the F2 generation was not greater than that of the Fj, and the F-^ variation was greater than that found in the parental lines.
Knox and Godfrey (19Jh) found a significantly greater percent of firm albumen in the eggs of White Leghorns than in eggs laid by Rhode
Island Reds. Knox and Godfrey (19dL and 19ib) observed that the per cent of egg production has no influence upon the percent of thick albumen in eggs laid by White Leghorns or Rhode Island Reds. Knox and Godfrey (19U0) selected for high and low percentages of firm albumen in Rhode Island Reds. The average percent of firm albumen in the eggs of the selected breeaers of the high line rose from $0.2 to 6d.6 percent in five years; while the mean percent of frim albumen in the eggs of the unselected progeny rose from £1.9 to 6U.0 percent.
The decrease in the low line was not as marked as the change which
occurred in the high line.
Van Wagenen and Wilgus (19di>) suggested that the condition of
the firm albumen could be scored on a numerical scale from 1 (highest us quality) to 5 (poorest quality) by comparing the broken out eggs vith a set of photographic standards* They examined 1*796 fresh eggs laid by Single Comb White Leghorns and found that the average albumen score was 1*76* Van Wagenen and Hall (1936) demonstrated that selec tion influences the observed score of the firm albumen much more than the percent of firm or inner thin albumen. Van Wagenen, Hall and
Wilgus (1937) observed that albumen quality seems to be highest in
White Leghorns and progressively lower in Rhode Island Reds, New Hamp- shires, Barred Plymouth Rocks and White Plymouth Rocks* The Barred and Wiixte Plymouth Rocks laid eggs which were significantly poorer in
tne condxtion of firm albumen than those produced by White Leghorns,
New hampsnires and Rhode Island Reds* The difference between the New
Hampshires and Rnode Island Reds wxth respect to albumen score was
not significant* The White Leghorns exhibxted greater variability
between straxna than those of the other three breeds, indicating
strain differences for the condxtion of fxna albumen and percent of
fxra albumen.
rtunro (1938) housed members of full-sister families in batteries
just prior to sexual maturity and collected data on egg quality over
three four-week periods* His data failed to demonstrate a hereditary
basis for albumen quality, therefore, he concluded that genetics
plays only a minor role in determining this characteristic*
Hall (1939) reported that the eggs laid by White Wyandot tea and
Barred Plymouth Rocks showed a significantly better score for the
observed condition of the firm albumen than those produced by Rhode
Island Reds and White Leghorns. £ggs from the Barred Plymouth Rocks U 6
had a significantly lover albumen score than those from the White
Vjyandottes.
Scott (l?Ul) examined representative eggs from all hens entered
in the Storrs Egg Laying Contest for standing up quality of the albu
men as measured by the Haugh unit. The condition of the thick white
was bAst in the White Leghorns and progressively poorer in the eggs
laid by Rhode Island Reds, New Hampshires, Barred Plymouth Rocks and
White Plymouth Rocks.
King (1952) working with data collected at the New York Random
Sample Test states that there are rather marked strain differences in
albumen quality and that the variation within strains is fairly high.
Re reported that breed differences are small compared with that found
between strains.
Brant* Otte and Chin (195d) examined all of the eggs produced in
the Egg Laying Contests in Rhode Island and Georgia during March and
August for various egg quality characteristics. They observed no
large differences in the average albumen q u a l i t y between the five
breeds and the crossbreds included in the study* however* within each
breed and among the crossbreds albumen quality varied greatly from
pen to pen. They concluded that no breed nor cross is outstandingly
superior in albumen quality.
Mueller (1950 and 1952) obtained a measure of albumen quality on
187 eggs laid during June by commercial inbred—hybrids and crossbreds
from non-inbred stocks. No significant difference was apparent be
tween pullets from the two sources with respect to albumen quality as
measured by the Baugh unit. C l i O W T H
I • Materials and Methods
On January 2U> 19h7» a project was initiated at The Ohio State
University designed to evaluate the relative performance of pure bred, crossbred and incrossbred chickens which were brooded, ranged and housed intermingled. The major objectives of this study were to compare the uniformity of growth and of production in chickens devel oped by different breeding methods and to secure information on the performance of stocks varying from none to relatively high Inbreeding and their value in crosses of strains and breeds. Coleman and Jaap
(195U) have reported on part of the latter phase of the experiment.
The project was designed to evaluate the most superior strains and crosses as a measure of what has been accomplished, rather than try ing to determine what might be done in the future.
Over a six year period U8 strains of purebreds, Uii crosses and j>3 groups of incrossbreds have been tested. The number of each kind
tested in each year is presented in Table 1. For the most part,
different pure strains, crosses and incrossbred line numbers were used each year. However, 7 kinds of chickens were repeated each of
the last 3 years to provide a measure of the year to year environ mental influence. The stocks were purchased either as eggs or as
hi aa chicks from some or the outstanding breeders in the United States.
The strains used in any one year were chosen on the basis of high egg
production records either in Egg Laying Contests or Becord of Perform
ance summaries. The crossbreds were selected on the performance of
the parental strains used in the cross. Usually, no data were avail
able on the performance of the cross itself. The incrossbreds have
been purchased from 5 different hybrid chick breeders. In 19U8-U9,
some incrosses and incrossbreds were obtained from different Experi
ment Stations. There were some exceptions in selecting the pure
strains, i.e. some meat or broiler strains were included in the study.
In purchasing the stock, it was requested that the chicks or eggs be
from flock rather than special pedigree matings. In this manner, we
hoped to obtain a fair cross-section of a breeder's commercial stock.
In 19U7-U6, there were two separate tests, dne was a broiler
study and the second a comparative test between purebreds, crossbreds
and incrossbreds. Five different kinds of broiler-bred stock were
secured in the form of 2 cases of hatching eggs during the first week
of August. Two hundred and fifty chicks of each kind were brooded
separately in every 2 nd pen of a 10 pen brooder house, while each
of the five remaining pens contained about $u straight run chicks of
each kind. This procedure was used as a preliminary test of growth
performance in competition with (a) same kind and (bj other kinds of
chicks. All chicks received the same ration (20 percent protein)
and the same care. Body weights were obtained for all chicks at
twelve weeks of age. The •t" test (Snedecor, 19U6) was used to test U9 for differences between strains in the straight and mixed pens. The data from the mixed pens were also analyzed by a modified Analysis of
V ariance technique given by Anderson and Bancroft (1952). This method is an approximate analysis for disproportionate data. Stan dard errors are given for each mean weight. Coefficients of vari ability were calculated for each strain. The standard errors and coefficients of variation for the average of all strains were computed from the within strains mean square. Tne harmonic number of birds was used in the computation of the standard errors.
Six pure strains, a three-way crossbred and a four-way incross bred were the stocks used in the comparative study of 191*7-1*8 * The purebreds were hatched at Ohio State while the crosses were purchased as chicks. From all but the 2 strains of New Hampshires, 160 sexed pullets and 60 cockerels were started on January 21*. All chicks hatched from each of the New Hampshire strains were started. All 8 kind3 were brooded in one long brooder house, one kind to each pen.
All chicks received a 20 percent protein ration and were given the
same care. Body weights were obtained on all chicks at 6 and 12 weeks of age. To determine whether the differences between strains
are significant, one-way analyses of variance (Sneaecor, 191*6) were
computed for the data of this year. The data for the males and fe
males were analyzed separately. Least significant differences were
calculated from the within strain mean squares (Snedecor, 19U6)•
Since the number of birds per strain varied, the harmonic number of
birds was used in these calculations. This procedure introduces a
slight bias. However, when the least significant difference method 50 of testing for significance between two means was compared with the
"t" test technique, this bias was observed to be slight. Thus, for
a rapid, comparative test the method of least significant differences
was chosen to indicate which mean differences are significant.
The purebred strains, incrosses and incrossbreds used in 19U8-U9
were obtained from the breeders in the form of hatching eggs as were
the Barred and Black crossbreds. Dominant White crossbreds were pro
duced from stock at Tne Ohio State University by rotating males in 3
pens to produce crossbreds from the same male par ants. These matings
were*
W-U* Dominant W*P.R. male x R.I.R. female.
W-7. Dominant W.P.R. male x N.H. (A) female.
W-8. Dominant W.P.R. male x N.H. (B) female.
Tne A and B denote that these strains are from the same source as
those in the preceding year, included in the project were a smaller
number of chicks from two additional matings involving Dominant White
males. These matings were:
H-7* Dominant W.P.R. male x Cornisn female.
ft-U* Dominant W.P.R. male x B.P.R. female.
Tne purpose of these matings was to test the combining ability of the
Dominant W.P.R. males with 3 different kinds of "Red" chickens, Cor
nish and Barred Plymouth Rocks. Approximately one case of eggs from
each kind was set on January U, 5 and 6, 19 Ud. Straight run chicks
from each hatching date were randomly assorted into groups for brood
ing. All received the same ration and care. Body weight measurements
were made on all male and female birds at 6 and 12 weeks of age. 51
To establish whether the observed differences between strains were significant, one-way analyses of variance were computed for the data.
The data for the sexes were analyzed separately. The average number of birds was used in the computation of the least significant differ
ences. Standard errors were calculated for each mean weight.
The design of the project during the last three years (1950
through 1953) was essentially the same. One hundred pullet chicks
each of 26 to 28 kinds were brooded intermingled. The starting date
each year was about February 1. All pens received the same ration
and care, however, at the start of the 1951-52 test, the ration was
altered 3lightly raising the amount of protein from 2u to 22 percent.
All chicks were weighed at 9 and 12 weeks of age. The method of anal
ysis was similar to that applied to the data of the preceding year.
Throughout the entire test a deep, unchanged litter system has been
used not only in the laying house but also in the brooder house.
The words strain and Kind are used in this paper to denote a
group of chickens from the same source whether they are purebreds,
crossbreds or incrossbreds.
II. Results
A. Body heights at 6 or 9 and 12 Vleeks of Age
1. 19U7-U8 Test
The broiler experiment of I9it7-U8 was performed as a preliminary
investigation of the feasibility of intermingled brooding. It is the
contention of many investigators that intermingled brooding or rearing 52 per se is detrimental. The average 12 week weights of the males and females In the straight and mixed pens are given In Tables 2 and 3*
The birds in the straight pens, i.e. only one kind of chickens, on
the average, were lighter in weight at 12 weeks of age than those in
the mixed pens (chicks of the five kinds intermingled). However, the
purebred chicks in the straight pens were heavier than in the Mixed
pens, while the crossbreds grew more rapidly intermingled with the
otner kinds than when raised by themselves. Although most of the
strains are ranked differently by the two types of brooding, the Colum
bian x N.H. crossbreds were the heaviest in both groups at 12 weeks of
age. Only three of the differences between the straight and mixed
pens are significant. In the case of the B.P.R. x N.H. (1) mating,
both tne male and female progeny raised in tne mixed pens were signif
icantly heavier than the same stock in the straight pens. The B.P.R.
females raisea in tne strai^nt pens were significantly heavier than
the^r contemporaries wn^ch were brooded intermingled (Table 3). labile
tne other differences are not significant (BtH test) they do show a
slight trend for heavier crossbreds and lighter purebreds in the inter-*
mangled pens. The fact that the crossbreds tend to be heavier and the
purebreds lighter wnen intermingled than those brooded by themselves
may indicate that the more heterozygous an individual is the better
it will be able to adapt itself to competitive growing conditions.
Dobzhansky (19U7) and Dobzhansky and Levene (1?U8) have observed that
flies (Drosophila pseudoobscura) heterozygous for certain genic ar
rangements in the third chromosome have a higher survival value than
either of the homozygotes. 53
Differences between the individual strains indicate that the
B.P.R. x N.H. (1) males raised in the straight pens are significantly lighter than the other crossbred males and the New Hampshire males
(Table 8). The females from this mating are significantly lighter in
12 week body weight than all of the other females in the straight pens.
The New Hampshire and Barred Plymouth Rock males brooded in the mixed pens are significantly lighter than the crossbred males (Table 10).
While the purebred females are lighter in weight than the crossbred
females in the mixed pens, all of the differences are not significant
(Table 11).
Presented in Tables U and 6 are the average 12 week weights of
the males and females of the broiler study by strain and by pen. The
analyses of variance of these means by the method of unweighted means
are given in Tables 5 and 7> The error term based on the means must
be divided by the harmonic number of birds in each pen (Anderson and
Bancroft, 1952). The degrees of freedom for the error mean square
are n-pq where p is the number of strains and q is the number of pens.
The mean square values for the strains and pens are highly significant
for both the male and female analyses. The strain x pen interactions
are not significant. This implies that one or more strains did not
weignt decidedly more in one pen than another. These results indicate
that the strains differ significantly with respect to 12 week body
weights. The significant pen effect demonstrates the need for rigor
ous control of environmental factors in this type of experimental
work. The pens were located in the same long brooder house and each
contained a random sample of 5 0 chicks from each of tne 5 strains. $ u
While this test does not provide sufficient evidence to critically prove the question of intermingled brooding, it does indicate the necessity of providing a similar, uniform environment for all stocks
and/or of providing an experimental estimate of the pen to pen varia
tion* Replicated pens may be used to furnish information on the
latter, however, if the observed variation is small the number of
replications needed to insure statistical soundness becomes quite
large and impractical for most experimental work* It is suggested
that the intermingled technique of brooding, rearing and laying be
utilized as a method of providing more uniform environmental condi
tions*
The design of the broiler experiment is such that pen effects
are confounded with the effects due to the brooding method* No at
tempt was made to separate and evaluate the major effects (brooding
procedure, strains and pens) in a combined analysis*
Presented in Tables lit and 15 are the average 6 and 12 week
weights for the males and females in the comparative test of 19U7-U8.
The least significant differences for the 6 week male and female
weights are *01* and *03 pounds, respectively* The New hampsnire
strain B inales were significantly heavier at 6 weeks of age than the
maies of any of the other strains* The females of this strain weighed
more at 6 weeks of age than the females of the other strains* The
minimal weight differences at 12 weeks of age are *13 and *07 pounds,
respectively, for ths males and faaales* The males of the B strain
New hampshires weighed significantly more at 12 weeks than the males
of any of the other strains except the Barred Plymouth Rocks* All of 5 5 the females except the Barred Plymouth hocks were significantly lighter in weight than the females of the B strain Hew Hampshires.
The three-way crossbreds were significantly heavier than the pure bred White Leghorns and the incrossbreds (Tables li* and 15).
2. 191*6-1*9 Test
The data in Table Id indicate that the crossbreds, on the aver age, are significantly heavier in weight at 6 weeks than the "Heavy" purebreds. This is true for both the male and female data. The
"Leghorn Type" incrossbred males and females weighed no more, on the average, than the purebred White Leghorns.
An examination of the average 6 week weights of the Dominant
White crossbreds reveals that the Dominant White males combined best with the strain B New Hampshire females. These crossbreds were signif icantly heavier in weight at 6 weeks than any of the other crossbreds.
The differences between the other Dominant White crossbreds are not
significant. The Dominant White Plymouth Rock by Rhode Island Red, by New Hampshire (B) and by New Hampshire (A) crossbreds were signif
icantly heavier at 6 weeks of age than the pure Dominant Whites. The
other two crosses involving the Dominant White males were heavier at
6 weeks of age than the pure Dominant Whites, although these differ
ences are not significant. The Barred and Black crossbreds weighed
decidedly less than the Dominant White crossbreds. The difference of
• 05 pounds between the Barred and Black Cross males is significant.
The same is true for the difference between the females of these
matings.
m 5 6
The crossbred males and females are significantly heavier than the purebred males and females at 12 weeks of age (Table 19)* The
Dominant White Plymouth Rock x New Hampshire (B) crossbred males are significantly heavier than the other crossbred males* The Dom inant White males "nicked” exceptionally well with this strain of
New Hampshires. In 19U8, an average weight of 3. 1* pounds (both sexes) at 12 weeks of age was an outstanding result. Except for the cross breds from the W.P.R. x B.P.R. mating, the differences between the other Dominant White crossbreds were not great* The Dominant White males did not combine well with the Cornish females. At 12 weeks of age, all of the Dominant White crossbreds were significantly heavier than the pure Dominant Whites. Although the differences between the
Barred and Black crossbreds were significant at 6 weeks, they weighed approximately the same at 12 weeks of age.
The "Heavy" incrosSbreds are aignificantly lighter than the
crossbred chicks but weighed more, on the average, than the "Heavy" purebreds (Table 16 and 19)* The "Leghorn Type" incrossbreds are
decidedly heavier than the purebred White Leghorns. This is to be
expected since "Heavy" breeds are used as one side of the cross.
3* 1950-51 Test
The data presented in Table 22 show that the "Heavy" crossbreds
are heavier both at 9 and 12 weeks of age than the "Heavy" purebred
strains but the differences at both age levels are not significant*
The "Heavy" incrossbreos are lighter in weight at 12 weeks than the
crossbreds but they weighed more, on the average, than the "Heavy" 57 purebred strains. These data Indicate that there is some hybrid vigor for growth and body weight to 9 or 12 weeks of age. They do not pro vide critical information on this phenomenon but rather illustrate that it occurs.
The "Leghorn Type" crossbreds are heavier at 9 and 12 weeks of age than the purebred strains of White Leghorns (Table 2Ji). The difference between these two groups at 9 weeks is significant, while at 12 weeks the variation in weight is not significant. The "Leg
horn Type" incrossbreds are heavier at both 9 and 12 weeks of age
than the Leghorn purebreds but lighter in weight than the crossbreds.
The "Leghorn Type" crossbreds and incrossbreds are expected to be
larger than the purebreds by virtue of the nature of the crosses.
U. 1951*52 Test
In 1951-52, the "Heavy" crossbreds were not significantly heavier
than the "Heavy* purebred strains (Table 26). It is of interest to
note that the crossbreds from the W.P.R. x R.I.R. and R.I.R. x W.P.R.
matings weighed approximately the same at 9 and 12 weeks of age.
The females of strain 56, a broiler strain of New Hampshires, were
significantly heavier at 9 weeks of age than the females of any other
pure strain or any of the crosses. At 12 weeks of age, all of the
crosses and pure strain UO, a White Plymouth Rock, were heavier than
these New Hampshires. All except the crossbreds from the R.I.R. x
W.p.R. mating were significantly heavier than these New Hampshires. The "Leghorn Type" crossbreds weighed significantly more at 9
and 12 weeks of age than the purebred strains of White Leghorns and 5 0 were heavier, on the average, than the "Leghorn Type" incrossbreds
(Table 27). No comparisons have been made between the "Leghorn" and
"Heavy* type strains because of the obvious differences in growth rates•
5. 1952-53 Test
The "Heavy" crossbreds in the 1952-53 test as in preceding years weighed more at 9 and 12 weeks of age than the "Heavy" purebred strains (Table 30), The differences at both age levels are signifi
cant. Tne New Hampshire strain 5U females were decidedly heavier at
9 and 12 weeks than any of the other pure strains or crosses. These
birds are from the same source as the strain $6 New Hampshires used
in 1951-52. The golds, strain 67, weighed significantly more at 9
and 12 weeks of age than the silver crossbreds (strain 66). The White
Plymouth Hocks (strain 63) and the Khode Island Reds (strain 71) ere
stocks from the same strains used in making these reciprocal matings.
At 12 weeks of age, the White Plymouth Rocks weighed more than the
silver and gold crossbreds, while the Rhode Island Reds weighed signif
icantly less than either crossbred. These results indicate that more
vigor for growth rate may occur if the Rhode Island Red is used as the
male parent rather than the female parent. This effect might be due
to sex linkage or to maternal effects transmitted by the female
through the egg.
The "Leghorn Type" crossbreds as in preceding years are signifi
cant!y heavier at 9 and 12 weeks of age than the purebred White 5 9
Leghorns (Table 31)- Likewise, the "Leghorn Type" incrossbreds weighed more than the purebred White Leghorns but less than the
crossbreds.
8. Nature of the Variability
The nature of the variation exhibited by the various strains
and mating types is of sufficient importance to be considered as a
separate phenomenon. Several statistics have been proposed to measure
the dispersion or variation of a variable such as growth (Snedecor,
19U6; Mills, 1?U0; Kenney, 19U9; and others). Among these are the
absolute measures of variation such as the range, mean deviation and
standard deviation and the relative measures such as the quartiles
and the coefficient of variability. It is common practice to use the
coefficient of variability as the measure of variation in comparing
two strains of chickens. Since it is a relative measure devoid of
units, the coefficient of variability is sometimes used rather blindly.
It is possible for two strains to differ widely in absolute variation
but have the same coefficient of variability. While the coefficient
of variability is used in this paper as a measure of the variation
exhibited by different strains, reference is aiso made to the stan
dard deviations of the means and of the individuals*
1. 19L7-lid Test
The variation in body weight of the males brooded in the mixed
pens of the 19U7-U& broiler atucty was markedly less, on the average,
than that for the males in the straight pens (Table 2). The within 60 strain coefficients of variability for the males in the straight and mixed pens are 1$.12 and 12*72 percent, respectively (Table 12).
Corresponding figures for the females are 13*08 and 13*09 percent, respectively (Table 13)* The standard errors of the average weights for the females in the straight and mxxed pens are *032 and *031 pounds, respectively (Table 3J* The female progeny from the Columbian x N.H. and B*P.H* x B.P.R. matings exhibited greater variability in weight in the mixed pens than in the straight pens* It might be reasoned that the Columbian x N.H. crossbreds are more variable be
cause their plumage pattern is entirely different from the other birds, however, one would expect that the males as well as females would be adversely affected. Very little of the increased variability
in weight of the B.P.R* females can be attributed to plumage colora
tion since two of the crossbred matings produced Barred chicks* It
seems very likely that the greater variability of weight of the B.P.R.
females is due largely to fortuitous factors* An examination of the
standard deviations of the means shows that the intermingled cross
bred males have much lower standard errors and at the same time are
heavier than the crossbred males raised in the straight pens (Table 2).
Tne purebred males whj.cn were brooded in the straight pens are heavier
and iiiore variable than the same stock brooded intermingled* The
standard errors for the females in either brooding procedure are ap
proximately the same. While the crossbred females are heavier in the
mixed pens than in the straight pens, only the Columbian x N.H. fe
males show an increase in total variance. Based on the axiom that
bigger things are more variable than smaller items one would expect 61 that these birds should all show greater variances. Likewise, the purebred females in the mixed pens by virtue of being smaller than their contemporaries brooded separately should have smaller variances •
Only the New Hampshire females show such a tendency. The data would seem to indicate that a marked decrease In the variation of 12 week body weight of males may be expected when birds of different kinds are brooded intermingled. Little or no reduction in total vari ability is expected among purebred or crossbred females*
2. 191*8-1*9 Test
The crossbred strains of 191*8-1*9 are slightly more variable than the "Heavy" purebreds or incrossbreds. The average within strain standard deviations for the purebred, crossbred and incrossbred males at 6 weeks of age are .17* *18 and .17 pounds, respectively. Corre
sponding figures for the females are .15, .16 and .15 pounds, respec
tively. When the influence of the larger mean weight is removed, the
purebred males and females are more variable than the crossbred males
and females (Table 20). The incrossbred males have a smaller within
strain coefficient of variability than any of the "Heavy Type" cross
breds or purebreds. The purebred White Leghorns and tne "Leghorn
Type" incrossbreds are markedly less variable in weight than the
"Heavy Type" chickens. This is to be expected since they are con
siderably smaller.
The standard deviations for the 12 week old "Heavy Type" pure
bred, crossbred and incrossbred males are .1*9, .1*6 and .1*2 pounds,
respectively. Corresponding figures for the females are .1*0, .39 62 and .36 pounds, respectively. Disregarding weight the purebred males
and females are more variable than either the crossbreds or incross
breds. The same trend is apparent from the coefficients of variation
(Table 21). As expected, the purebred Leghorn males and females are
the least variable of any of the various kinds of chickens studied.
3. 1950-51 Test
The data presented in Table 2k reveal that the purebred strains
are more variable than the crossbred or incrossbred strains. The
within strain coefficients of variability for the purebred, crossbred
and incrossbred females at 9 weeks of age are 11*. 11, 12.U9 and 11.66
percent, respectively. Corresponding figures for the 12 week data are
13.15, 12.65 and 10.60 percent. While the incrossbreds averaged to
weigh more than the crossbred and purebred strains at 9 weeks of age,
tneir within strain coefficient of variation was lower than that for
the other two mating types. The standard deviations of the 9 week
weights for the purebred, crossbred and incrossbred mating types are
• 26, .26 and .2U pounds, respectively. Corresponding figures for the
12 week data are .36, .36 and .30 pounds.
At 9 weeks of age, the “Leghorn Type* incrossbreds were more
variable in weight than the purebred or crossbred chickens (Table
25)* At 12 weeks of age, the incrossbreds, on the average, exhibited
less variation in weight than the purebreds or crossbreds. It is of
interest to note that the purebred strains of White Leghorns are more
variable in 9 and 12 week weight than the crossbred females. The
crossbreds weighed considerably more than the purebred Leghorns 6 3
(Table 23). The within etrain standard deviations for the 9 week weights of the purebred, crossbred and incrossbred mating types are
.2U> *2U and .27 pounds, respectively. Corresponding figures for the 12 week data are .31# >30 and .29 pounds.
U. 1951-52 Test
The purebred strains of 1951-52 are more variable in 9 and 12 week weight than the crossbred strains. The within mating type coef ficients of variability' for the 9 and 12 week weights of the purebred strains are 15*A|2 and 11**60 percent, respectively' (Table 2d). Similar values for the crossbred strains are 13.69 and 12.13 percent. The standard deviations of the 9 and 12 week weights of the purebred strains are .27 and .26 pounds, respectively, while the within mating type standard deviations of the 9 and 12 week weights of the cross
bred strains are, respectively, .38 and .35 pounds.
The HLeghorn Type*1 crossbreds as in the preceding year exhibit
less variation in 9 end 12 week weights than the purebred White Leg
horns (Table 29). The crossbreds are likewise less variable in
weight than the incrossbreds. The variation in weight observed
among the incrossbred strains is less than that found among the
purebred strains.
5. 1952-53 Test
Presented in Table 32 are the coefficients of variability of
body weights of the 9 and 12 week old "Heavy Type" females in the
1952-53 test. Again as in previous years the crossbreds exhibit 6 U less variation in body weight at 9 and 12 weeks than the purebred strains* The standard deviations for the 9 and 12 week data cal culated from the within purebred strains mean squares are *2U and
•30 pounds, respectively* Corresponding figures for the crossbred strains are *2U and .30 pounds*
The purebred White Leghorns used in the 1952-53 test are more variable in 9 week weight than the “Leghorn Type" crossbreds and incrossbreds (Table 53>• The incrossbreds exhibit less variation in weight at both age levels than the crossbreds* The standard deviations for the 9 week old purebred, crossbred and incrossbred females are .23, .23 and *22 pounds, respectively* Similar values
for the 12 week data are *25* *29 and *26 pounds*
The fact that the "Heavy Type" crossbreds weighed more and
at the same time were less variable in weight is quite surprising*
Likewise, the "Heavy Type" incrossbreds of 19l|8-U9 and 1950-51 were
heavier and less variable than the "Heavy" purebred strains* The
heavier "Leghorn Type" crossbreds and incrossbreds tend to be less
variable in 9 week weight than the lighter Leghorn purebreds* How
ever this trend is not as pronounced as the one observed among the
"Heavy Type" chickens. These and similar observations on individual
strains suggested a closer examination of the relationship between
mean weight and variance* Plotted in Figures 1 and 2 are the 9 and
12 week mean weights and variances of each strain used during the
last three years of the project. A cursory examination of Figures
1 and 2 reveals that the heaviest strains within an age group are 6 5 not necessarily the most variable. The total variance exhibited by a strain is greater at 12 weeks of age than at 9 weeks of age. For the 9 week data the regression of variance on mean weight is .00659*
This regression value is not significantly different from aero. The small non-significant regression coefficient indicates that there is little or no change in the variance as the mean weight becomes larger.
In the 12 week data there is evidence of a closer relationship be
tween mean weight and variance (Figure 2). The regression of variance
on mean weight for the 12 week data is .02852* a significant associa
tion. This nay be interpreted to Indicate that for each 10 percent
increase in mean weight for these data there has been a corresponding
average increase of .2852 units in the variance.
Since MHeavy Type" chickens are normally grown for meat produc
tion, it seemed desirable to study this relationship in the "Heavy"
purebred strains separately. Plotted in Figures 3 and b are the 9
and 12 week mean weights and variances of the 23 pureured strains
used in the project during the last three years. The regression of
variance on mean weight for the 9 and 12 week data are -.i>G3bl and
-.01332, respectively. Although neither of these regressions are
significant, they indicate that there may actually be a decrease in
tne variance as average body weight becomes larger. This is in di
rect contrast to the results obtained from the study of all strains.
Plotted in Figure 5 are 3 week average weights and variances
obtained from a purebred strain of New Hampshires. These birds were
not part of the project, however, the data were made available by the breeder. Although the data are not entirely comparable, pertinent information can be obtained from them. Prom an examination
of the graph, it ia clearly evident that as weight increases the vari
ance likewise becomes larger* The regression of variance on mean weight of these females is *1092* a significant association* These
data present a striking contrast to that obtained from the "Heavy"
purebred strains or from all strains included in the project*
Two explanations could be proposed to account for the differences
observed in the relationship of the mean weight and variance* One
could theorize a physiological maximum for growth rate which would
explain why the heaviest strains tend to have smaller variances than
lighter strains* In view of the data obtained from the New Hamp-
shires, a broiler strain well known for their rapid growth rate, it
seems likely that a physiological maximum for growth rate is not
causing the low variation in weight of the more rapidly growing
strains* The brooding procedure, intermingling, might be causing
in some unknown manner the more rapidly growing strains to be less
variable. The data collected in the comparative test of 191*7-1*6
(Tables 11*, 15* 16 and 1?) indicate that the variances of the "Heavy"
purebred strains increased as body weight becomes larger. These
strains were brooded in the conventional manner* However, the opposite
is true for the broiler-bred stock of the broiler test which were
brooded in the conventional method, while the variances for the birds
in the mixed pens showed a pronounced tendency to increase in magni
tude as body weight increased* Although the possibility of a physio
logical maximum is not denied, it seems unlikely that it is operating 6 7 in the present situation. Much more vork is needed to explain the nature of this phenomenon.
i 7kU* l. Summary of the kinds of stocks used in the project.
Year Purebred No. of Crossbred No. of Incrossbred Strains Strains 19U7-48 New Hampshirea 2 W. Leghorn x (R.l.R. Rhode I. Red 1 xB.P . R . ) 1 1 Barred P. Rock 1 White Leehom 1
Total 5 1 1
19U8-U9 White leghorn 1 Dora. W.P.R. X R.l.R. 1 Dorn. W. P. Rock 1 Dorn. W.P.R. x N .H* 2 Rhode I. Red 1 Dora. W.P.R. x Cornish 1 Barred P. Rock 1 Dora. W.P.R. x B.P.R. 1 5 Barred Cross 1 Black Cross 1
Total k 7 5 19U9-50 New Hampshire 2 All possible combine- White Plymouth Rock 2 tions of the U parental lines, i.e. 12 crosses
Total h 12 0
1950-51 White Leghorn 3 R.l.R. x W. Leghorn 3 Rhode I. Red 2 Australorp x W. Leghorn 1 New Hampshire 2 Gold 2 White P. Rock 2 Silver 2 8 Barred P. Rock 1 Black Cross 2
Total 10 10 8 1951-52 W. Leghorn 3 W. Leghorn x Red 1 New Hampshire 3 Red x W. Leghorn 1 Rhode 1. Red 2 Australorp x W. Leghorn 1 W. P. Rock 2 Black Cross 1 B. P. Rock 1 Gold 1 9 Silver 1
Total 11 6 9
1952-53 W. Leghorn 3 W. Leghorn x Red 1 New Hampshire 3 Red x W. Leghorn 1 Rhode 1. Red 2 Australorp x W. Leghorn 1 W» P. Rock 2 Black Cross 1 B. P. Rock 1 Gold 1 10 Silver 1
Total 11 6 10 Table 2. Average 12 week weights of males in the broiler test of 1 91*7-1*8. (in pounds)
Straight Pen Mixed Pen Strain No. Ave. Weight No. Ave. Weight Difference
B.P.R. x N.H. (1) 115 3.11* t .01*7 15U 3.1*1 * .031* -.27**
B.P.R. x N.H. (2) 130 3.29 ♦ .0 39 80 3.38 t .0h5 -.0?
Columbian x N.H. 125 3.37 t .01*6 i69 3.1*2 1 .033 -.05
N.H. 133 3.29 t .01*3 u*9 3.23 * .036 .06
B.P.R. 118 3.21 m♦ .01*6 98 3.13 t .01*1 .08
Average — 3.26 *♦ .oi*l* — 3.32 t .038 -.06
#* Sigiificant at P ^ level. Table 3. Average 12 week weights of females in the broiler test of 19k7mh&* (in pounds)
Straight Pen Kixed Jm Strain No. Ave. weight Ho. Ave.. Weight Difference f B.P.R. x N.H* (1) 102 2.50 t .035 137 2.66 .030 -.16#* ♦ B.P.R. x N.H. (2) 105 2.63 1 .031 98 2.6k m .031 -.01
Columbian x N.H. 107 2.67 t .029 163 2.71* * .030 -.07 CO CM O N.H. 133 2.63 t .035 Uih 2.61 « . •02
B.P.R. 110 2.69 t .030 93 2.53 * .033 .16**
Average 2.62 + .032 — 2.65 ♦ .031 -.03
** Significant at level* Table 1*. Average 12 week weights of males by pens in the mixed pen broiler study of 19l*?~l*8. (In pounds)
Pen 2 1* 6 8 16 Strain No. Ave. kt. No. Ave. ki. No. Ave. kt. No. Ave. kt. tlo. Ave. kt. Average
B.P.R. x N.H. (1) 2? 3*U5 35 3.59 26 3.31* 29 3.20 35 3.1*1 3.1*1
B.P.R. x N.H. (2) 18 3.56 23 3.1*2 12 3.26 17 3.30 10 3.22 3.38
Columbian x N.H. 36 3.56 33 3.60 37 3.30 36 3.29 27 3.32 3.1*1
N.H. 31* 3.39 28 3.17 29 3.16 32 3.16 26 3.21* 3.23
B.P.R. 21 3.30 21 3.30 19 3.00 20 2.88 17 3.11 3.13
Average mm 3.1*6 — 3.1*1* - 3.23 3.18 — 3.29 3.32 72
Table 5» Analysis of variance of the mean 12 week weights of males in the mixed pen broiler study of
Source of Variation D.f. Sum of Squares Mean Square
Strains h .31368 •078U7**
Pens U .31811 .07953**
Strains x pens 16 .10561 .00660
Within^ 625 .00723
-a-#- Significant at P01 level.
1. Within mean square from preliminary analysis adjusted by multiplying it by (1/25) (S 1/k^). Degrees of freedom for adjusted mean square are n-pq. Table 6. Average 12 week weights of females by pens in the Mixed pen broiler study of 19l*7-l*&. (In pounds)
Pen 2 J* 6 8 10 Strain No. Kean No. Kean No.. K ean No. Kean No. Kean Average
B.P.R. x N.H. (1) 2? 2.61* 21 2.82 30 2.61 28 2.56 31 2.55 2.66
B.P.R. x N.H. (2) lb 2.7b 17 2.75 20 2.51* 21 2.53 22 2.61* 2.61*
Columbian x N.H. 30 2.?1 33 2.80 29 2.77 31 2.66 1*0 2.62 2.71*
N.H. 26 2.7 9 30 2.52 31 2.56 25 2.57 32 2.61* 2.61
B.P.R. 17 2.72 18 2.60 17 2.1*9 16 2.1*1* 23 2.1*3 2.53
Average — 2.82 m v 2.6? — 2.61 ~ 2.57 — 2.58 2.65 75
Table 7* Analysis or variance of the mean 12 week weights of females in the mixed pen broiler study of l?li7~U&*
Source of varxation Q.f. Sum of Squares Mean Square
Strains h .12532 . 03133**
Pens h .2 2 0 6 ? .05517**
Strains x pens 1 6 .0679? .00i*25
Within^ 610 •001*72
** Significant at PQ^ level.
1. Within mean square from preliminary analysis adjusted by multiplying it by (S TEj^* degrees freedom for adjusted mean square are n-pq. 7 k
Table 6 . Mean differences of weights of 12 week old males in the straight pens of the iyl*7 “i48 broiler study. (1 ) (in pounds)
Strain ” r z 3" -- 5” 5" B.P.R. x N.H. (1) —
B.P.R. x N.H. (2) .15*
Columbian x N.H. .23** .08 — i 1 1 • N.H. .15* .00 0 CO
B.P.R. .07 -.08 -.16* -.08 ~ Ti Mean of stock at left side of table minus mean of stock at top of table. * Significant at Pq £ level. ** Significant at P q -j_ level.
Table 9 . Mean differences of weights of 12 week old females in the straight pens of the 19U7-U8 broiler study. (1) (In pounds)
Strain .... " " " I .... 3---- IT --- F " B.P.R. x N.H. (1) «
B . P . R . x N.H. (2 ) .13** —- Columbian x N.H. .17** ,uk
N.H. .13** .00 -.oii —
B.P.R. .19** .06 .02 .06 Mean of stock at left side of table minus mean oT stock at top of table. * Significant at P q ^ level. ** Significant at Pu^ level. 75
Table 10. Mean differences of weights of 12 week old males in the mixed pens of the 19U7-U6 broiler study. (1) (in pounds)
Strain ’ 1 2 - 3 h 3 B.P.R. x N.tf. (1) 0 1 . B.P.R. x N.H. (2) —
Columbian x N.H. .01 .01* —
N.H. -.16** -.15* -.19**
B.P.R. -.26** -.25** -.29** —.10 —
table. * Significant at P q ^ level. ** Significant at PQ^ level.
Table 11. Mean differences of weights of 12 week old females in the mixed pens of the 19U7-li6 broiler test. (1) (In pounds)
Strain ■S LA T ~ * T~ B.P.R. x N.H. (1) — i • fo B.P.R. x N.H. (2) o —
Columbian x N .H. .06 .10* — 0 0 1 1 • N.H. e -.1 3 * *
B.P.R. -.13** -.11* -.21** -.08
table. * Significant at Pq £ level. ** Significant at P q ^ level. Table 12. Coefficients of variability of body weights of lit: week old males in the 1947-48 broiler study* (Percent)
Strain______straight Pens Mixed Pens
B.P.K. x N.H. (1) 16.10 12.21
B.P.R. x N.ii. (2) 13.71 12.02
Columbian x N.H. 15-15 12.57
N.H. 15.15 13.65
B.P.R. 15.56 12.63
Average 15.12 12.72
Table 13* Coefficients of variability of body weights of 12 week old females in the 1947*48 broiler study (Percent)
Strain Straight Pens Mixed Pens
B.P.R. x N.H. CD lii* 16 1 3.09 B.P.R. x N.H. (2 ) 1 2 .0 7 11.72
Columbian x N .H. 1 1 .1 6 14.23
N.H. 1 5 .3 5 12.94
B.P.R. 1 1 .6 6 12.1*5
Average 1 3 .0 6 13.09 77
Table lit* Average 6 week weights of males and females in the comparative test of 1947-48. (In pounds)
Hale Female Strain NO. Mean No. " Mean
R.l.R. 187 1.12 *.010 184 0.941.010
W.P.R. 163 1.041.013 203 0.941.009
B.P.R. 210 l.ijf.ood 158 1.031.009
N.H. (A) 80 1.13*.016 117 0.991.012
N.H. (B) 111 1.23 *.013 138 1.061.011
VI.L. x (R.l.R. x B.P.R.) 42 1.161.022 101 1 .0 4 1 . 0 1 2
W.L. 67 0.921.016 103 0.861.010
Xncrossbred 73 0.991.012 148 0.86?. 009
Average __ 1.101.015 — m 0.961.010
Least sxgnifleant difference for males: PQc level * *01: lb. j PQ1 level a .05 lb. P
Least significant difference for females: Pq £ level s .03 lb.;
P 01 level s .04 lb. 78
Table 15* Average 12 week weights of males and females in the comparative test of 1987-88• (in pounds)
Kale Female Strain No. Mean No. Kean
R.l.R. 181 3 . 8 2 *.030 188 2.571*019
W.P.R. 156 3.221.039 200 2.591*021
B.P.R. 195 3.551*029 158 2.871*028
N.H. (A) 76 3*311*087 113 2.581*027
N.H. (B) 107 3*601.088 135 2.781.025
W.L. x (R.l.R. x B.P.R*) Uo 3.001.072 97 2.851*032
W.L. 63 2.681.089 100 2.231*023
Incrossbred 69 2.881*038 183 2.161.027
Average ~ 3.311.086 ~ 2.581.025
Least significant difference for males * P^,- level .13 lb.} Pm level .17 lb. 05
Least significant difference for females* PQI- level .07 lb.5 Pm level .09 lb. *
1 Table 16. Coefficients of variability of body weights of 6 and 12 week old males in the comparative test of 1?U7-U8. (Percent)
Strain 6 week 12 week
12.27 12.02
W.P.R. 15.6$ 15.08
B.P.R. 10.79 11.51
N.H. (A) 12.80 12.33
N.H. (B) 11.38 12.80
W.L. x (R.l.R. x B.P.R.) 12.31 15.29
W.L. 1U.65 1U.15
Incrossbred 10.57 11.16
Average 12.53 12.8U Table 17* Coefficients of variability of body weights of 6 and 12 week old females in the comparative test of l947-,48- (Percent)
Strain 6 week 12 week
R.l.R* 14*46 10.19
W.P.R. 13. 39 11.48
B.P.R. 10.59 10.70
N.H. (A) 12.
N.H. (B) 11.91 10.64
W.L. X (R.l.R. x B.P.R*) 11.99 12.79
W.L. 11.96 10.28
Incrossbred 12 02 14.76
Average 12.57 11.47 Table Id* Average 6 week weights of males and females in the comparative test of 191*8-1*9* (in pounds)
Male Female
Strain No. Mean No. Mean
Rd.Ji« 101* 1.10 t .016 68 0.99 ft . 0 15 B.P.R. 100 1.15 t .016 10 5 1.01* A .015 W.P.R.* 93 1.29 * .019 102 1.12 ft .011* Average 1.18 ft .017 — —— 1 . 0 5 ft .015
W.P.R. x R.l.R. -Wl* 101* 1.36 ft .019 111 1.19 ft .021 W.P.R. x N . H . (A) -W7 85 1.35 ± .019 97 1.21 4 .015 W.P.R. x N.H. (B) -W8 122 1.1*1* i .019 103 1.29 ft .017 W.P.R. x Cornish -M7 31 1.32 » .02k 1*8 1.19 * .015 W.P.R. x B.P.R. -Ml* 23 1.32 ft .039 20 1.23 ft .011 B.P.R. x R.l.R. 115 1.16 t .015 89 1.02 * .011* R.l.R. X B.P.R. i n 1.11 * .017 121* 0.96 ft .011 Average 1.28 ft .020 — - 1.11* ft .017
Heavy Incrossbred Jfl 105 1.27 * .017 117 l.l i* ft .016 *2 S i 1.16 ft . 0 1 6 103 1.02 ft .012 Average 1.22 t . 0 1 7 -- 1.08 t .OH*
iiv.L. 128 1.19 * .013 117 1.06 ft .012
Leghorn Type Incrossbred *1 51* 1.23 ft .019 75 1-07 i .013 * 2 113 1.26 ft .015 118 1.13 ft .013 #3 102 1.13 ft .012 103 0.97 ft .011 Average --- 1.20 t .015 — 1.06 ft .013
Average of a l l strains ___ 1.23 ft .017 ... 1.09 ft . 01 5 * The W.P.R. in this test year are all Dominant White. Least significant difference for males: Pq£ level a .05 lbs.; P01 level equals .0? lbs.
Least significant difference for females: Pq c level s .05 lbs. PqI level - .06 lbs. 82
Table 19* Average 12 week weight* of males and females in the comparative test of 19U&-U9* (in pounds)
Male______Female____
Strain No* Mean No* Mean
R.l.R. 10U 2 .9 8 ft .01*3 08 2.1*5 ft . 01*3 B.P.R. 100 3 .2 9 t -oa7 105 2 . 6a ± .0 3 6 W.P.R.* 93 3 .2 5 t .0 5 6 102 2 .6 9 i .0 4 2 Average --- 3 .1 7 t .0 4 9 2 .6 0 ft . 01*0 ♦ W.P.R. x R.l.R. -WU loi* 3 .a a .0 5 2 105 2. 8a ft .0 3 8 W.P.R. XN.H. (A) -W7 85 3.U 9 * .049 98 2 .6 8 ft . 01*1* W.P.R. xN.H. (B) -Wb 122 3 .8 0 ft .01*3 97 3 .1 0 * .01*7 W.P.R. x Cornish -M7 31 3.1*5 ■V .065 U9 2 .9 5 * .0 4 7 W.P.R. x B.P.R. -Ml* 23 3 .2 4 «» .0 7 9 19 2.7a ft .096 B.P.R. x R.l.R* H 5 3 .2 0 ± .01*3 09 2 .6 5 t .035 R.l.R. x B.P.R. 111 3 .2 6 t .0 4 2 12U 2 .5 5 ft .0 3 0 Average — 3.1*5 ♦ .051 ----- 2 .0 0 ft .01*3
Heavy Incrossbred 0l 105 3 .2 3 + .oai* 115 2 .6 0 t .0 3 4 #2 87 3 .1 9 ft • 01*2 102 2 .6 2ft .0 3 4 Average 3 .2 1 ft .01*3 ----- 2 .6 5 ♦ .0 3 a W.L. 129 2 .6 0 • 026 Ill 2 .2 3 t .0 2 6
Leghorn Type Incrossbred #1 55 2 .9 5 .0 2 0 77 2 .2 5 ft .028 02 n u 2 .9 9 ♦ .0 3 1 n a 2.a a ft .0 3 1 0J 102 2.1U .035 105 1 .9 1 ft .0 2 6 Average — 2.77 ♦ .039 2.20 ft .0 2 9
Average of all strains — 3 .1 6 ♦ .ua6 — 2 . 5 0 ft .037
Least significant difference for males: P qkj level s .14 lbs*; Pq I level - .19 lbs* Least significant difference for females: Pq5 level r .11 lbs.; P01 level - .15 lbs. 8 3
Table 20. Coefficients of variability of body weights of 6 week old males and females in the comparative test of 19L6-L9* (Percent)
Strain Hale Female R.l.R. 15.16 1L.6L B.P.R. 1U.02 15.26 W.P.R.* 1L-L6 13.OL Average li+.S2 1L> 3L W.P.R. x R.l.R. -WL 13. *1 18.2L W.P.R. x N . H . (A) -W? 13-10 12.6L W.P.R. X N.H. (B) -W8 1L.58 13.78 W.P.R. x Cornish -M7 10.01 8.6L W.Plt. x B.P.R. -&L 1U.27 13.21 B.P.R. X R.l.R. 13.60 13.OL R.l.R. X B.P.R. 16.59 12.Ll Average 1U.28 1L.03
Heavy Incrossbred #1 lL.il 15.18 * 2 12.7L 12.2L Average 13.58 11*. 11 W.L. 12.83 11.88
Leghorn Type Incrossbred 11. L3 10.92 0 2 12.37 12.92 *3 10. L7 11.57 Average 11.63 12.06 Average of all strains 13-70 13.6L
* The W.P.R. in this test year are all Dominant White. 8U
Table 21. Coefficients of variability of body weights of 12 week old males and females in the comparative test of 19lj£-U?« (Percent)
Strain Hale Female
R.l.R. 1U.83 16.53 B.P.R. 1U. 36 II4.OI4 W.P.R.* 16.61 15.61 Average 15.38 15.33
W.P.R* x R.l.R. Hiili 15.19 13. lh W.P.R. xM.H. (A) -W7 12.71 1 5 . 2 2 W.P.R. xN.H. (B) -W8 12.66 111. 90 W.P.R. x Cornish <417 10. U5 11.09 W.P.R. x B.P.R. -MU 11.66 15*19 B.P.R. X R.l.R. 1U.11 12.62 R.l.R. x B.P.R. 1 3 . aa 1 2 . 9 2 Average 13.U6 13.85
Heavy Incrossbred frl 13.88 13.65 *2 12.32 13.19 Average 13.21 13.145
W.L. 13.65 12.12
Leghorn Type Incrossbred #1 12.UU 10.97 #2 12.79 13.37 #3 Hi* 56 H 4.O8 Average 13.31 13.05
Average of all strains 13.86 13.95
* The W.P.R. in this test year are all Dominant white. 8 5
Table 22. Average 9 and 12 week weights of heavy- type females In the comparative test of 1950-51 • (In pounds)
Strain 9 week T 2 week Strain No. too. Mean No. Mean ♦ W.P.R. k 96 2 .0 U .036 58 2.97 t .059 W.P.R. 22 8 6 2.17 * .035 59 2.96 £ .051 B «P *R. 1 6 92 1.93 ♦ .028 56 2.67 * .oiid R.l.R. 8 90 1.82 £ .027 6 0 2.55 * .0 li6 R.I.R.* 26 83 1.77 t .026 6 1 2.39 * .030 N.H. 1 8 8 8 2.18 ± • 0 2 li 59 2 . 7 8 £ .038 N.H. 2 k 95 2 .Oil t .028 6 0 2 . 6 6 ± .0 ii8 Average — — 1.99 t .029 — 2.71 i .0 U6
R.l.R. x B.P.R.* 1 89 2.15 t .029 61 2.89 t .0U9 R.l.R. x B.P.R. 17 96 1 . 9 6 t .022 58 2 . 7 8 £ .03U ♦ W.P.R. X R.l.R.* 6 82 2 . 1 1 m .031 57 2.99 t .OitO W«P.R. X R.l.R. 2 1 6 0 2 . 1 6 £ . 0 32 57 2.82 £ .0 ii6 R.l.R. X W.P.R.* 7 72 2 . 02 £ .025 59 2.82 ± .05U R.l.R. x W.P.R. 9 8 8 1.93 * .027 6 1 2.67 t .052 Average — — 2 . 0 5 t .028 — 2.83 ♦ .0ii7
Incrossbred # 1 11 8U 2.00 * .026 58 2.68 * .035 0 2 12 66 2.15 £ .030 58 2.85 ♦ *0U3 Average —— 2.06 + .028 — 2.76 £ .059
Average of all strains — 2.02 * .029 __ 2.76 t .0U6
Least significant difference for 9 week data: PQq level s *08 lb.$ Pq I level = .11 lb.
Least significant difference for 12 week data; P q ? level - .13 lb. PqI level - .17 lb. * Indicates the strains which were repeated in each of the last three years of the project. 86
Table 23- Average 9 and 12 week weights of Leghorn type females In the comparative test of 1950-51• (In pounds)
Strain 9 week -12 — j-- Strain No. Wo. Mean Wo. Mean
Vi. L. 0 66 1.70 * .027 59 2.30 * .01*2 VI.L. 15 86 1.80 * . 0 2 5 58 2.38 * .033 V.L. 19 89 1.71 ± .025 SU 2.21 * .01*8 Average — — 1.7U T .026 — 2.30 t -01*1
Minorca x W.L. lit 95 1.68 * .026 58 2.27 t .038 Australorp x Vi.L. 3 89 1.78 * .022 56 2,kk t .01*1 Red x Vi • L. 20 89 2.02 ± .025 59 2.58 t .01*5 Red x V.L. 25 69 1.80 t ,029 57 2.32 t .036 Average — — 1.82 1 .026 — 2.1*0 t .01*0
Incrossbred *1 2 95 1.92 t .028 59 2.60 t .01*3 5 82 1.73 * .028 6 0 2 .1*2 * .036 #3* 10 9k 1.81 * . 0 2 7 59 2.39 * .029 /fit* 13 87 1.88 t *030 58 2.60 ± .036 Average of all s trains -- — 1.78 ± .027 2.37 - .039 Least significant difference for 9 week data; A W level s .08 lbs.; Rq! level ■ .10 lbs. Least significant difference for 12 week data: P q c level s .11 lbs. Pqi level - ,1k lbs. * Indicates the strains which were repeated in each of the last three years of the project. 87 Table 21*. Coefficients of variability of body weights of 9 and 12 week old heavy type females in the comparative test of 1950-51. (Percent) Strain______Strain No* 9 Week 12 Week W.P.R. 1* 17. 2k 15.27 W.P.R. 22 11*. 99 13.16 B.P.R. 16 13.93 13.1*8 R.l.R. 8 13.91 13.87 R.l.R.* 26 13.28 9.97 N.H. 18 10. 2k 10.63 N.H. 2k 13.57 11*. 00 Average — li*. 11 13.15 R.l.R. x B.P.R.* 1 12.95 13.35 R.l.R. x B.P.R. 17 10.93 9.31 W.P.R. x R.l.R.* 6 13.17 10.12 W.P.R. x R.l.R. 21 13.28 12.29 R.l.R. X W.P.R.* 7 10.66 U*.77 R.l.R. X W.P.R. 9 13.17 15.H* Average — 12.1*9 12.65 Incrossbred #1 11 12.13 9.9 2 *2 12 11.51* 11.1*8 Average 11.88 10.80 Average of all strains 13.23 12.68 * Indicates the strains which were repeated in each of the last three years of the project. m Table 25* Coefficient® of variability of body weights of 9 and 12 week old Leghorn type females in the comparative test of 1950-51* (Percent) Strain Strain No. 9 Week 12 Week W.L. 0 14. 70 14.19 W.L. 15 13.06 10.66 W.L. 19 13.96 15.99 Average — 13.87 13.61 Minorca x W.L. lit i5*Uo 12.70 Australorp x W.L. 3 11.89 12.76 R e d x W.L. 20 11.84 13.33 R e d x W.L. 25 13.25 11.60 Average « 13.07 12.70 Incrossbred # 1 2 lit. 11 12.73 #2* 5 14-44 11.44 10 llt.33 9.32 #4* 13 14-94 11.30 #5 27 15.47 14.57 * 6 28 17.63 14.32 Average -- 15.08 12.21 Average of all strains — 14.21 12.67 * Indicates these strains were included In the project in each of the last three years* 89 Table 26• Average 9 and 12 week weights of heavy type females in the comparative test of 1951-52. (In pounds) Strain 9 We e k 1 2 w e e k Strain No. No. Mean No. Mean W.P.R. ko 88 1.83 * .037 67 2.93 t .0k5 W.P.R. U6 87 1.67 * .029 69 2.6k t .0i*2 B.P.R. k9 86 1.63 t .029 7k 2.38 fc .ok9 R.I.R.# 3k 88 1.7k * .027 80 2.56 t .0k6 R.I *R. U8 77 1.61 t .028 70 2.31 * .039 N.H. 33 91 1.65 * .028 69 2.k6 t .oko N.H. 39 98 1.68 t .02k 68 2.5k t *0k3 N.H. 56 119 2.12 * .02k 116 2.73 1 .038 Average — --- 1.76 ± .028 --- 2.58 * .0k3 R.l.R. X B.P.R.* 35 97 1.93 * .02k 69 2.90 t .okk W.P.R. XR.I.R.* U2 93 1.86 * .030 68 2.90 i . 0 k 3 R.l.R. x W.P.R.* kl 9k 1.6k t .02k 71 2.8k 1.039 Average 1.87 t *026 — 2.88 ! . 0 k 2 Average of all strains — — 1.79 * .028 —- 2.65 ± .0k3 Least significant difference for 9 week data; P q c level s .08 lbs*; P01 level ■ .10 lbs* Least significant difference for 12 week data; pQIj level s .12 lbs.; P01 level s .16 lbs. * Indicates these strains included in each of the last three years of the project. m 9 0 Table 27* Average 9 and 12 week weights of Leghorn type females in the comparative test of 1951-52. (in pounds) Strain 7 Week ---- 12 Week Strain No. No. Kean No. Kean W.L. 37 93 1 . 6 0 t .017 69 2.33 t .025 VI.L. 1*7 83 1 .1*2 t .029 6 8 2.23 ♦ .035 W.L. 52 89 1.55 t .027 71 2.28 * . 0 3 6 Average —— 1.53 t .021* — 2 . 2 8 i .032 Australorp xW.L. 38 90 1.63 t .023 67 2.1*3 t .038 Red x W.L. 1*3 91 1 . 6 6 t .029 69 2.55 t .01*0 W.L. x Red 1*1* 98 1 . 7 8 t . 0 2 0 6 8 2.63 t .031* Average —— 1.69 * .021* — 2.5U * .037 Incrossbred # 1 55 83 1 . 3 2 t .027 72 1.93 * .037 36 9k 1.65 * . 0 2 0 69 2 .1*6 * .031 *3 3 0 96 1.83 * .021* 71 2.63 t .0 l|0 # 1** 31 9k 1.63 t .021* 70 2 . 3 6 ♦ .033 #5* 51* 85 1 . 6 6 t .026 6 6 2.35 t .037 #6 1*5 96 1.59 t .023 6 6 2.38 ± .01*1 #7 50 66 1.61* t .031 66 2.31* t .035 #8 51 91* 1.62 * .026 70 2.32 * .036 09 32 90 1.70 t .025 66 2.53 t .038 Average — — 1.63 i .025 — 2.37 ± .036 Average of all strains — 1.62 * .025 — 2.36 t .036 Least significant difference for 9 week data: pQ(- level * *07 lbs.; P q I level m .09 lbs. Least significant difference for 12 week data: F0t level r *10 lbs.; P01 level r *13 lbs. * Indicates these strains included in each of the last three years of the project. 91 Table 28* Coefficients of variability of body weights of 9 and 12 week old heavy type females in the comparative test of 1 9 5 1 -5 2 . Strain Strain Mo. 9 Week 12 Week W.P.R. 1*0 1 9 . 1 6 1 2 . 5 6 W »P *R* U6 1 6 . 1 6 13.36 B.P.R. 1*9 1 6 . 6 2 17.61* H.I.R.* 31* 11*. 57 1 6 . 0 8 R.l.R. 1*8 15.21 11*. 2 1 N.H. 33 1 6 . 2 5 13.57 N.H. 39 11*. 12 13.96 N.H. 56 12.39 1 5 . 1 6 Average — 15. 1*2 11*. 6 8 R.l.R. x B.P.R.* 33' 1 2 .1*0 12.70 W.P.R. x R.l.R.* 1*2 1 5 .61* 12.13 R.l.R. x W.P.R.* ia 12.78 11.67 Average — 13.69 12.18 Average of all strains __ 11*. 92 11*. 03 * Indicates these strains included in each of the last three years of the project* 92 Table 29- Coefficients of variability of booty weights of 9 and 22 week old Leghorn type females in the comparative test of 1951-52* (Percent) Strain Strain No. 9 Week 12 Week W.L. 37 1 0 . 1 6 8.61* W.L. 1*7 18.75 1 2 . 6 6 W.L. 52 16*33 13.31 Average — 1 5 * 0 8 11*80 ▲ustralorp x W.L. 38 1 3 * 6 1 1 2 * 8 1 Red x W.L. i*3 1 6 * 6 8 12.93 W.L* x Red 1*1* 11.25 10*69 Average — 13.87 12.13 Incrossbred # 1 55 16.1*2 16.17 # 2* 36 1 2 *01* 10.31* *3 30 13.09 12.69 31 11*.17 1 1 . 6 8 #5* 5U 11**61* 13.06 # 6 1*5 11*. 52 11**38 * 7 50 15*63 12.27 # 8 51 15*77 12.61* #9 32 11*. 0 1 12.15 Average — 11*. 55 1 2 . 8 0 Average of all strains -- 11*. 52 12.51 * Indicates these strains included in each of the last three years of the project* 93 Table 30. Average 9 and. 12 week weights of heavy type females in the comparative teat of 1952-53* (In pounds) Strain 9 week 12'SSSS: Strain No. No. Mean too. Mean W»F iR* 53 87 2 . 1 2 * .028 87 3 . 0 2 t .039 W.P.R* 6 6 92 2.26 & .026 76 3 . 3 0 t .033 B.P.R. 6 1 6 8 2.08 ± .026 87 2.91 t .031* R.I.R.* 56 87 2 . 0 7 ± .021* 81* 2.89 t .032 R.I.R. 71 96 1.92 * .025 75 2 . 6 8 * .031* N.H. 50 78 1.91 t .025 71* 2 . 6 6 A .028 N.H. 51* 8 8 2.73 * .026 85 3.60 ± .031 N.H. 61* 65 2 . 0 1 A . 0 2 9 61* 2.70 * *038 Average —— 2 .11* 1 .026 — 2.98 *.031* R.I.R. X B.P.R.* 51 79 2 .21* t . 0 3 0 7k 3.09 t .039 W.P.R. X R.I.R.* 6 6 87 2.19 t . 0 2 1 75 3.08 * .02? R.I.R. X W.P.R.* 67 89 2.26 A .025 75 3 . 2 2 't . 03 6 Average — — 2.23 A .025 — 3.13 * .031* Average of all strains — — 2.17 t .026 — 3.02 t .031* Least significant difference for 9 week data* Pq£ level s *07 lbs*; PqI level s *09 lbs* Least significant difference for 12 week data: P^c level - ,09 lbs* tM P ^ level s mia xbs. * Indicates these strains included in each of last three years of the project* 1 9k Table 31* Average 9 and 12 week weights of Leghorn type females In the comparative test of 1952-53* (In pounds) Strain 9 Week TTfleSk Strain No. tdO. Mean No. Mean W.L. 58 56 1.89 i *031 69 2.52 t .033 W.L. 65 67 1.72 ± .025 76 2.35 4 .028 W . L. 69 93 1 .8 U ± .026 75 2.53 * *026 Average —— 1.81 Tt .026 — 2.U6 ± .029 Australorp x W.L. 76 8 6 1.80 * . 0 2 3 75 2.U6 t .029 Red x W.L. 62 03 1.95 * .027 77 2.56 1 .033 W.L. x Red 55 69 2 . 0 6 * .030 67 2.62 ♦ .0 U0 Average —— 1 . 9 2 * .026 — 2.5U ± .031: Incrossbred # 1 63 90 2 . 1 0 ± .020 77 2.67 * .025 # 2* 70 0 U 1.87 ±r .023 76 2.59 * .027 #3 72 92 1.92 * .025 75 2 . 7 0 ± .033 73 0 U 1 . 6 8 t .022 7U 2 .3 8 * .026 #5 7U 56 1.75 * .028 53 2.U9 * .035 *6* 57 93 2 . 0 7 * .020 75 2.73 * .030 #7 52 73 1 . 8 8 ± .033 76 2 .W: t .039 *0 59 96 1 . 7 8 t .018 93 2 . 2 6 t *021: *9 6o 75 1 . 8 6 ± .029 75 2 .U6 * .032 n o 75 91 1.90 t .023 72 2.63 * .031 Average — — 1 . 8 9 * .021* — 2.53 ± .030 Average of all strains — — 1 . 8 8 t .025 —— 2.52 t *031 Least significant difference for 9 week datat P q *j level s *07 lbs.; P q -^ level s .09 lbs. Least significant difference for 12 week data: Pqc level z *09 lbs. j P01 level s .11 lbs. * Indicates these strains included in each of last three years of the project. 95 Table 32 • Coefficients of variability of body weights of 9 and 1? week old heavy type females in the comparative test of 1952-53* (Percent) Strain Strain No. 9 Week 12 Week W.P.R. 53 12.23 1 2 * 0 6 W.P.R. 6 8 10*99 8.07 B.P .K. 6 1 ll.S U 10.83 R.I.R** 56 10.75 10.29 R.I *R* 71 12*73 10.85 N.H. 50 11*51 8 . 9 8 N.H. 5U 8*79 7*95 N.H. 6k 1 1 . 6 0 11.39 Average — 11.18 10.13 R.I.R. X B.P.R.* 51 11.82 1 0 . 7U W.P.R. x R.I.R.* 66 9*17 7.66 R.I.R. x W.P.R.* 67 10.53 9*72 Average — io*5U 9.U7 Average of all strains — 10.98 9-9U * Indicates these strains included in each of last three years of the project* 1 9 6 Table 33* Coefficients of variability of body weights of 9 and 12 week old Leghorn type females in the comparative test of 1952*53* (percent) Strain Strain No. 9 Week 12 Week W.L. 58 12.38 10.91* W.L. 65 13.65 10.32 W.L. 69 13.55 9.00 Average — 12.53 10.11 Australorp x W.L. 76 11.76 10.09 Red x W.L* 62 12.U2 11. 3U W.L. x Red 55 12.16 12.38 Average — 12.20 11.31a Incrossbred #1 63 9.07 8.23 92* 70 11.07 9.19 *3 72 12.70 10.66 9h* 73 11.85 9.56 95 71a 12.18 10.30 #6* 51 9.26 9.1a2 91 52 1 5 . 0 0 13.81 #8 59 10 . 0 5 IO.IaO 99 60 13.72 h .U a 910 75 11.79 9.97 Average ... 11.58 10.35 Average of all strains 11.87 1 0 . 5 0 * Indicates these strains included in each of the last three years of the project* Figure 1* Reiation between the variance and mean weight of all of weight mean and variance the between Reiation 1* Figure strains included in the project from 1950 through 1953* through 1950 from project the in included strains YAJtlANCE .02 . .10 .1* 01 1.30 ) ' 0 5 . 1 0 7 . 1 1.90 .OI FFMLS KPOUWS W U O P IK FEMALES W.IO-ITOF (9 week data) week (9 .10 2 ?= ?= 6 6 0 0 . I•• I 9 6 0 . 91 9 8 Figure H. Relation between the variance and mean weight of strain® included in the project from 1950 through 1953* (12 week data) ,lk g 5a I Figure Figure VARUNGE .10 .06 3* 3* 1.50 Relation of variance to to variance of Relation "Heavy*1 purebreds "Heavy*1purebreds 1.70 1.90 EO T F ESL- H F0UM3S Hi FEiSALf-S OF .T VEIO 9.10 (9 (9 n a e m week data)* week weight of of weight * * B ,0T6 .003- 1 23 23 strains of strains 90 9 9 m Figure U Figure UUiNUE Relation of variance to mean weight of of weight mean to variance of Relation *10 .*o . .it 1 * 2,00 "Heavy" purebreds (12 week data). week (12 purebreds "Heavy" t.ko .O . a Z.&O r n i a r u u u n r cr SO *0 N 3.1*3 .N 3 3*00 j.tc 23 sris of strains 100 101 Figure 5* Relation of variance to aean weight of New Haapshires (ti week data). ! 12 r ■ .109 x 155 10 0 6 02 1.70 1.90 2.10 2.50 yfEIOliT OF FEiaU^S IN POUNDS 102 111* Discussion One of the major objectives of the project was to compare the uniformity of growth of purebred, crossbred and incrossbred poultry. Tnere has been and still Is a decided need for tests or experiments designed to evaluate existing strains of poultry for their ability to live, grow and produce eggs. Much work has been published on the efficiency of different breeding or mating systems} however, comparisons between the various systems in the same or similar envi ronment are rather limited. Warren (1927, 1930 and 19U2), in his notable work on crossbreeding, compared crossbreeding with standard breeding. While an attempt was made to provide a uniform environ ment for the crosses and purebreds, the stocks were raised in sep arate pens. Xn view of accumulating evidence (Qowe, 1952} Qowe, et. al., 1953} and others) the possibility of location, not only geographic but also location within one large brooder house, must be considered as a major source of variation that may be observed in a variable such as growth. Many of the early investigations designed to compare rate of growth or body weight at a given age did not take into account this factor. This may have been one of the reasons why conflicting results were obtained. Two different lines of approach have been used in the past in an attempt to control environmental factors, namely increase the sample size and to use replicated pens. If the expected variation between groups is rather small, the sample size or number of replica tions become quite prohibitive (Bird and Qutteridge, 193U and 103 Schroeder and Lawrence, 1932)* Since these two techniques or a com bination of the two are not always practical, a procedure, intermin gled brooding, rearing and laying, was utilized in the current inves tigation as a means of providing as near identical conditions as possible* By intermingling we infer that a random sepl* of every kind is placed in each pen* The results of the intermingled vs* straight brooding test of 19U7-U& are conflicting* In the intermingled pens the crossbreds are heavier than the purebred stock* The crossbreds in the mixed pens are heavier than those brooded in the straight pens* This would imply that the crossbreds, possibly because of greater heterozygosity, can adapt themselves to competitive growing conditions more effect tively than the purebreds* The crossbred and purebred males brooded in the mixed pens a exhibited less variation in 12 week body weight than the males brooded in the straight pens* Variability in weight of the females, on the average, was approximately the same for both brooding methods* Tne analyses of the mean weights of the strains in the mixed pens by the method of unweighted means demonstrate the presence of significant pen effects* The significant pen effect is surprising* Three factors which may have caused or contributed to the pen effect are pen location, an inadequate sample or a genotype x environment interaction* The data in Tables U and 6 indicate that location is probably the major contributor to the between pens mean square* The average weight for the females is largest in pen 2 and steadily decreases through the rest of the house* There is a difference of iou .2h pounds between the heaviest and lightest pen. While the weight gradient is not as pronounced for the males (Table h)> there is con siderable difference between the weights of the males in pens 2 and U and pens 8 and 10. While the possibility of an inadequate sample or genotype x environment interaction are not ruled out, it seems likely that they contribute very little to the pen to pen variation. More information is needed to ascertain the exact magnitude and nature of the pen effects. These data do indicate the necessity of provid ing some kind of a control over environmental factors. The design of the broiler experiment is such that the brooding effects are confounded with pen effects. A. combined analysis de signed to partition the effects due to brooding method, pens, strains and certain interactions was not carried out. While the results of crossbreeding studies are conflicting in many cases, most investigators agree that there is hybrid vigor for early growth rate and body weight at broiler age (Warren, 1927, 1930, 19U2; Knox and Olsen, 1938; Horlacher and Smith, 1938; Horlacner, Smith and Wiley, 19U1; uhostley and Nordskog, 1951; and many others). The data presented in this paper indicate that there is hybrid vigor for growth rate and/or body weight at 6, 9 and 12 weeks of age. Al though the design of the project in every year except 19U9-50 is such that a critical evaluation cannot be given for hybrid vigor, it does provide evidence of the occurrence of this phenomenon. In 19^9-50, two strains of White Plymouth Rocks and two strains of New Hampshires were reciprocally crossed in all possible combinations. Coleman (19$3) concluded from this test that a greater degree of heterosis i 1 0 5 is obtained from breed crosses than from strain crosses* He observed that reciprocals do not always perform in a similar manner* The stocks used in this project were for the most part egg pro* duct ion strains or crosses. A few meat or broiler strains were included from time to time* The "Heavy Type" crossbreds in the last U years weighed more at 6, 9 and 12 weeks of age than the "Heavy* purebred strains (Tables IS* 19* 22, 23, 26 and 30). The crossbreds, in general, exhibited less variability in weight at all age levels than the purebred strains* Knox and Olsen (1936) reported that cross breds produced from "general purpose" breeds, on the average, were better than purebred Rhode Island Reds, White Leghorns and the progeny from crosses involving the White Leghorns in body weight at 10 weeks of age. They concluded that the quality of the parental stock has considerable influence upon the quality of the crossbreds and that different strains of the same varieties of chickens may produce dif ferent results when crossed. The data given in Table 22 illustrate this point very clearly. Strains 6 and 21 are silver crossbreds from two different sources. At 12 weeks of age, these crossbreds differed significantly in body weight. The gold crossbreds, strains 7 "nd 9, likewise differed significantly with respect to 12 week body weight* At 12 weeks of age, the two groups of Black-Cross females weighed approximately the same* Similar differences are observable between the "Heavy* purebred strains. White Plymouth Rocks are being discriminated against by poultry processors because of the popular belief that this variety of chickens exhibits greater variation in weight at broiler age than other popular 1 0 6 broiler strains, varieties or crosses* There is not to our knowledge any reports on this subject in the literature* An examination of the data for 19i*8 through 1953 (Tables 20, 21, 2k, 28 and 32) reveals that the variety as a group tends to be more variable than other pure* breds and some crosses* However, just the same as there are meat and egg strains of New Hampshires, there are strains of White Plymouth hocks which are average with respect to variation in body weight and strains that are remarkably uniform in growth. The reason why the White Plymouth hocks should be more variable than the Barred Plymouth hocks or other pure varieties is not at all clear* Since the birds were all treated alike so far as possible, it seems likely that envi ronmental factors would have little Influence here* One could theorise that there is (are) some factor (s) In the hereditary makeup of White Plymouth Rocks that cause or contribute to this phenomenon* One ap proach to the problem is nutritional, assuming that the genes respon sible for the increased variation in weight alter the digestive or metabolic systems. Much work is needed to determine the exact nature of this phenomenon. Considerable effort is being made by commercial poultry breeders at the present time to find lines which will "nick11 well when crossed. Evidence to date (Warren, 19U2; Ghostley and Nordskog, 1951; Coleman, 19 $ J and others) indicates that a greater degree of hybrid vigor is to be expected from breed crosses than strain crosses* The data ob tained from crossing Dominant White Plymouth hock males on 3 kinds of "Red” chickens indicate that strains of the same breeds may perform differently with respect to body weight at 6 and 12 weeks of age* 107 These Dominant Whites exhibit good general combining ability with the stocks tested (Table 13 and 19) • They combined exceptionally well with the B strain Mew Hampshires. The production of dam lines which will possess specific combining ability for certain sire lines on a commercial basis will require a continual testing program. Ad ditional research is needed relative to this problem. The average 12* week weights of the 7 strains which were repeated during the last three years (marked by asterisks) for 195<->-5l* 1951- 52 and 1952-53 are 2.6U* 2.63 and 2.85 pounds* respectively. The difference between years was found to be significant. Since most of the 7 strains showed a lower average weight in 1951-52 than in 1950- 5 1 or 1952-53* environmental conditions were apparently not the most ideal for growing conditions in this year. Likewise, it is unlikely that there is any strain x year interaction since most of the 7 strains responded in a similar manner. Growing conditions in 1952-53 and/or improved genetic stocks may nave caused the marked increase in body weight at 12 weeks of age. In view of the fact that all 7 strains showed a decided increase in weight* moat of this greater growth rate in 1952-53 must be contributed to environmental condi tions. The only measure of the year to year fluctuation in growth is a consideration of the performance of these 7 strains. IV. Summary The results of the growth studies warrant the following summary statements* 1. The data indicate that there is considerable hybrid vigor 108 for growth or body weight at 6, 9 and 12 weeks of age. Crosses of egg production strains were heavier, on the average, than the pure bred strains which were selected primarily for egg production, 2. As body weight increases in size the variance in weight tends to remain constant or in the case of 23 strains of "Heavy1* purebreds to show a slight decrease in size (within a given age group). Data obtained from a different source indicate that there is a high relationship between bocfer weight and variation in weight. It does not seem likely that the brooding procedure nor a physiological max imum for body size are the causes of this large weight-low variance phenomenon. 3. The results of the project demonstrate the need for further tests designed to evaluate poultry. Most of the strains were utilized in the study only one or possibly two years. There were only seven strains included for three years. The wide year to year variation m growth of the same stock indicates that conclusions based on the per formance of a stock in one year give little or no indication of the true performance of tne stock. U. While the question of intermingled brooding is not decided, the data indicate a decided need of rigorous control over environ mental factors. The significant pen effect noted in the 19U7-U8 data indicate that within one brooder house, there are uncontrolled en vironmental factors. Since increased sample sizee or larger numbers of replicated pens are often impractical, it is suggested that inter mingled brooding be used as a means of providing more nearly uniform conditions for all birds. 109 $. White Plymouth Rocks are more variable than most of the other pure strains and crosses studied* However, certain strains exhibit rather marked uniformity in growth to broiler age. 6. Data from limited tests for combining ability indicate that different strains from the same breed do not combine equally with Dominant White Plymouth Rocks. i EGG PRODUCTION I. Materials and Methods The egg production records reported here were collected during 1950-51, 195l-$2 and 1952-53* The stocks have been described in the section on growth. Approximately 75 pullets of each strain were ran domly selected at about 10 weeks of age and placed on range* These pullets were intermingled in the colony houses while on range* Fifty pullets of each strain were randomly chosen during the middle of June (at approximately Id to 20 weeks of age) and housed in the layxng house* The pullets were intermingled in each of the Id laying pens* Three or U pullets of each kind were placed in 10 of the Id pens, while the remaining pens accommodated 5 or 6 pullets of each strain* Dead birds were replaced until the start of the laying test on July 1st* The laying test extended from this date (pullets about 150 days old) until the second week of June or until the birds were 500 days old* A five-day trapnesting week was used in each year* The produc tion records presented in this paper have not been converted to seven # day equivalents except for use in the concluding remarks* Management and feeding practices were essentially the same for all pens. Morning lights were utilized in the fall and winter months to stimulate egg 110 Ill production. Throughout the entire project, a deep, compost litter system was utilised in each laying pen* Possibly mortality aa it was experienced in theee experiments was the major factor in differentiating the atraina with respect to egg production* There ia considerable evidence to indicate that egg production ia reduced quite substantially by disease (Harris, 1926, 1927; Hutt, 1938 and others)* With mortality averaging about 30 percent, it is very likely that morbidity was the major variable measured in this project* Survivors* and hen-housed production records are given in this paper* Standard errors for the mean of each strain, mating type and for the flock were calculated for the survivors* egg production records. The average number of hens in each category was used in these calcu lations rather than the harmonic number primarily because the number of hens per group did not vary too greatly* The average number, in general, is larger than the harmonic number of hens and if there was much difference between the two it would provide a leas critical estimate of the standard deviation of the mean than the harmonic number* Aa implied previously, the differences between the average and harmonic numbers are small. Since all standard errors were calculated in the same manner, comparative statements will not be biased too greatly. Standard errors were calculated for the mean hen-housed production of each strain, mating type and for the flock from the 1950-51 data* These statistics were not computed for suc ceeding years. Coefficients of variability were calculated from the survivors1 egg production data for each strain, mating type and for 112 the entire flock* The mating type and flock coefficients of varia tion were based on the within mating type and within flock mean squares, respectively. This statistic was computed for the hen- housed data in 1950—51 hut not in succeeding years. Analyses of variance were calculated for the survivors1 egg pro duction records in each year. These analyses were made on the data within each mating type, between all strains irregardless of mating type and between mating types. The data were handled in this manner because of the disproportionate subclass numbers. Similar analyses were performed on the hen-housed production data of 1950-51* The close agreement between the hen-housed and the survivors1 analyses in 1950-51 indicate that analyses based on hen-housed production data would add but little information to that obtained from the survivors1 data. Thus, in succeeding years the hen-housed data were not analyzed. In order to obtain a more comprehensive analysis, the data of 1950-51 and 1951*52 were reduced so that tnere would be an equal num ber of items in the subclasses. Eighteen strains were chosen for , this analysis in each year so there were 6 strains of purebreds, 6 groups of crossbreds and 6 kinds of incrossbreds. In the purebred category, there w e r e 3 strains of “Heavies** and 3 strains or strain crosses of White leghorns. The 6 kinds of crossbreds consisted of 2 groups, one composed of 3 "Heavy** x "Heavy" type crosses and the other of 3 "Leghorn Type" x "Heavy" crosses. The 6 kinds of incrossbreds consisted of 2 groups of 3 strains each, selected at random from the total number of incrossbreds. The data were further reduced by con sidering the number of eggs laid by only 26 surviving hens in 1950-51 113 and 29 surviving hens in 1951-52• Egg records were available on these hens over a 10 month period* Only the production records from August to June were analysed in this manner* The July data were dis carded because of the very low production, while the June records did not cover an entire month* Since the egg records are based on a 5-day trapnest week., the total number of trap days varied from month to month. The month effect is, as a result of this procedure, a biased effect* The month to month variation as estimated in these analyses is slightly greater than it may actually be* II. Results A. 1950-51 Test The average, number of trapped eggs xaid by the surviving hens of all strains in the 1950-51 test is 120* U eggs (Table 51*)* The between strains mean square is significantly large 1 than the with in strain mean square (Table 35* Part I). This result is not sur prising when it is realized that we are comparing strains bred for egg production with strains bred for meat production* The least significant differences for the Pq^ and Fq^ levels of significance are 21*8 and 28*7 eggs, respectively* Differences in mean numbers of eggs between any two strains which exceed these values are termed significant or highly significant* Before examining the differences between strains, it is of Interest to study the analyses of variance presented in Parts XU, IV and V of Table 35* The mean square for the between strains of purebreds is highly significant while the mean square values for between crossbreds and between incrossbreds are not Ill* significant* It is the low production of the purebred** particularly those classified as "Heavy** that has brought about the significant between strain* mean square. Strains number U and 22 are White Plym outh Rocks one of which has been bred for meat production and the other could be considered a dual purpose strain* Strain 19 is a strain of White Leghorns well known for their egg producing abilities* In this test year* they averaged only 9U*1 eggs per surviving hen* The New Hampshire* strain 2li* is better Known as an egg strain than a meat strain* Strain 26* an egg production strain of Rhode Island Reds* are significantly better than every other pure strain except numbers 15 and 16* The "Heavy* purebreds laid more eggs* on the aver age* than the purebred White Leghorns* The gold and silver crosses (strains ? and 6) were obtained from tne same breeder. Presumably the same parental stock was used in both crosses* The golds averaged 114.6*5 eggs and the silvers averaged 12L*6 eggs* Strains 9 and 21 are likewise gold and silver crossbreds but from a different source* In this case the silvers averaged to lay more eggs than the golds* The Austra-Whites* strain number 3* laid fewer eggs than the other "Leghorn Type" x "Heavy" crossbreds* The other "Leghorn Type" x "Heavy" crossbreds laid* on an average, approximately the same number of eggs* The two Red x Leghorn crosses (numbers 20 and 25) were obtained from the same source* The average survivors1 egg production for these two crosses is approximately the same* The "Heavy" crosses averaged to lay 2*0 eggs more than the "Leghorn Type" x "Heavy* crosses. The notation* "Leghorn Type" x "Heavy", does not imply necessarily that a Leghorn or a breed similar 115 to the Leghorns was used as a male parent In the cross. This notation is used to include all crosses in which a Leghorn or some other light breed was used as one of the parents of the cross. The “Heavy Type" incrossbreds (used to denote that both sides of the cross were what is commonly called " Heavy" breeds) tended to lay slightly fewer eggs than the "Leghorn Type", however, the difference of 11.2 eggs is not significant. By "Legnom Type" incrossbreds we mean those in which one parent was an inbred line or incross of White Leghorns. The possibility of an inbred line must be included because some of these incrossbreds are three-way rather than four-way crosses. For ^ase of classification and manipulation of the data these three- way and four-way hybrids are all considered as incrossbreds. The "Leghorn Type" incrossbreds from different sources averaged approxi mately the same number of eggs. The range in average survivors' egg production was from 12b.2 eggs for strain 10 to 1U3.3 eggs for strain 28. The between mating type mean square for the survivors' production data is significant at the Pq-^ level (Table 35 » Part II). The least significant differences calculated from the within mating type mean square for the P ^ and PQ^ levels are 7*2 and 9.5 eggs, respectively. The differences between the purebred and the other two mating types are highly significant, while the difference between the crossbred and incrossbred mating types is not significant. The purebred strains as a group are more variable than the cross breds or incrossbreds. The average coefficient of variability for the purebred strains is U3*3 percent (Table Jk)* Corresponding figures 116 for the crossbred and Incrossbred mating types are 3 3 * 9 and 3 7 * 2 per cent, respectively. The crossbreds exhibited less variation in num bers of eggs laid by the surviving hens than the incrossbreds. How ever, this is not the case for the hen-housed production data. The coefficients of variability based on the hen-housed production data for the crossbred and incrossbred mating types are 6U.7 and 61.2 per cent, respectively. This change in relative size of the coefficients can be attributed to the greater variability in mortality within the crossbreds and incrossbred strains. Since the crossbreds experienced greater variation in mortality than the incrossbreds or the pure- breds, it seems remarkable for them to exhibit variability approaching that of the incrossbreds. The coefficients of variation for the entire flock on a survivors1 and hen-housed basis are 3 6 * 0 and 6 I4.6 percent, respectively. Survivors1 egg production excludes mortality and does not measure the complete reproductive performance. For this reason, the hen- noused averages are given (Tables 3U* 39 and 143) for each year. Only the data of 1950-^1, however, were analyzed by the Analysis of Vari ance technique. The difference between the average survivors* and hen-housed production values gives an indication of the mortality which a strain experienced during the year. In some cases, the strain which has the highest average number of eggs on a survivors* basis is also the high ranking strain when the average number of eggs is com puted on the hen-housed basis. This type of phenomenon is possible if the strain has low mortality. Purebred strain 26 illustrates this point. Similarly, a strain might rank high as a result of computing 11? its* production on the survivors' basis but be among the lowest when the average is based on the number of hens housed. Purebred strain 15, a White Leghorn, exemplifies this case. The average number of eggs per hens housed in 1950-51 is presented in Table 3i*. Due to high mortality among most of the strains, these averages are very low. This fact also is the cause of the very high coefficients of vari ability. The mean square value for between strains is highly significant, as it was for the survivors' data (Table 56). Tne between purebred strains and the between crossbreds mean squares are significant at the P01 and P ^ levels, respectively. The differences between tne crossbreds were not significant for the survivors' egg production data. This is probably due to the high mortality of some of the crosses. A difference of 21 or 22 eggs between any two strains constitutes a significant difference. Strain 26, a Rhode Island Red, is clearly superior to all otner pure strains and to most of the crosses and in crossbreds. The relative ranking of the three mating types remained the same. The purebred strains, with an average hen-housed production of 60.9 eggs, were significantly lower than the crossbreds and incrossbreds. Tne incrossbreds produced, on the average, significantly more eggs tnan the crossbreds. This difference was not significant for the survivors' data. The difference in number of eggs laid by the cross breds and incrossbreds on a survivors' and hen-housed basis are 35.0 and 28*5 eggs. This difference indicates greater mortality within the 1X8 crossbred strains than within the Incrossbreds. Plotted in Figure 6 is the percent hen-housed production for each mating type. It is evident from this graph tnat the superiority of the Incrossbred mating type Is maintained throughout the period from August to April. In Hay the incrossbred strains produced fewer eggs than the crossbreds or purebreds. The crossbreds are superior to purebreds in percent non-housed production from August through May. It is of interest to note that egg production dropped steadily from August to December* however* the rate of decline was not the same for each of the mating type. The egg production of all three mating types increased in January and the purebred strains exhibited increased pro duction .through February. The percent hen-housed production for the crossbreds and incrossbreds steadily declined after January. The average number of eggs laid by 26 surviving hens in each of 18 strains is presented in Table 37* The analysis of these data is given in Table 38• The mean squares for all of the sources of vari ation listed in the table are significantly greater than the error mean square. The mating type, strains within mating type and month mean squares were also tested against the mating type x month or „ strain x month mean squares. The main effects were likewise signif icantly larger than the appropriate interaction mean squares. It can be concluded from tnis analysis that the three mating types differ significantly as do the 6 strains within each mating type. The groups within >mating type notation refers to the "Heavy* or "Leghorn Type" strains in the purebred and crossbred matings and the two randomly 1X9 selected sets of "Leghorn Type" incrossbreds* The differences between these groups are highly significant. B- 1951-52 Test The average number of eggs laid by the surviving hens in the 1951-52 test is 115»7 eggs (Table 59). The average production for tne purebred, crossbred and incrossbred mating types are 100*0, 123*U and 130.2 eggs, respectively* The between mating type mean square is significantly larger than the within mating type mean square (Table 1*0, Bart 11)* The least significant number of eggs between mating types is 6*5 eggs* The surviving incrossbred hens averaged to lay significantly more eggs than the hens of the crossbred or purebred mating types. The purebred strains, on the average, laid signifi cantly fewer egg a than the crossbreds* The analyses of variance presented in Parts 111, IV and V of Table 1*0 indicate that the differences between the pure strains, be tween the crosses and between the incrossbreds are all significant* The least significant differences calculated from these analyses in dicate that 17 to 19 eggs constitute a significant difference between strains* Strain 3U averaged to lay more eggs than any of the other "Heavy" purebreds. This Rhode Island Red is from the same breeder as strain 26 in the 195o-5l test. Strain 39* a New Hampshire, ranks second among the "Heavy" purebreds in average survivors* egg produc tion. The "Heavy" pure strains averaged „ fewer eggs than the purebred White Leghorns* 120 The golds and silvers, strains 111 and U2, are from the same source as the gold and silver strains (7 and 6) used in the preced ing year. The average survivors1 egg production for these two crosses is approximately the same* Strains i*3 and liU are Red x Leg horn and Leghorn by Red crosses obtained from the same source as the Red x Leghorn cross used in 1950-51* The Leghorn x Red crossbreds averaged 7 . 6 _ eggs more than the crossbreds from the Red x Leghorn mating. The range in average survivors1 egg production for the incross breds was 1*7-U eggs. This difference between the highest and lowest average production is significant as might be expected. There is more variation in the average number of eggs laid by the incrossbred strains in this year than in 1950-51j although the average within strain coefficient of variability for 1950-51 was considerably higher. The coefficient of variation calculated from the within crosses mean square is 30.7 percent (Table 39). Corresponding figures for . the purebred and incrossbred strains are 1*2.1 and 31*7 percent, respec tively. The crossbreds are slightly less variable than the incross breds and both are decidedly less variable than the purebred strains. Since the incrossbreds experienced greater mortality tnan the cross breds, the crossbreds would undoubtedly show less variation than the incrossbreds for hen-housed production data. In 1950-51, total mor tality as measured by the difference between the two production in dices was less for the Incrossbreds than for the crossbred strains. The coefficient of variation for the entire flock is 3U*2 percent. An examination of the coefficients of variability reveals that usually 121 the strains with the lowest average number of eggs per surviving hen have a coefficient of variation among the largest* This is not always true. Purebred strain 33 illustrates this case. These birds averaged 80.1 eggs and the coefficient of variability is 62.8 percent. The average number of eggs based on the number of hens housed for each strain and mating type is given in Table 39* The relative rank ing of the various strains nave cnanged considerably, due to excessive mortality. A crossbred, strain Uii, averaged to lay more eggs than any other strain. The second ranking strain is a White Leghorn (number li7). The relative ranking of the mating types are the same. However, ^he superiority of the incrossbred strains is not as great for the hen-housed data as it was in the case of the survivors* data. The average hen-housed production for the purebred, crossbred and incross bred mating types are 81.3* 99*7 and 100.1 eggs, respectively. Plot ted in Figure 7 is the percent hen-housed production for the purebred, crossbred and incrossbred mating types. The purebred strains laid at a lower rate throughout the test period than the crossbreds or incross breds. The incrossbreds laid at a higher rate than the crossbreds from August through October. From November through December the cross breds were slightly better than the incrossbreds. Thereafter, the crossbreds were superior to the incrossbreds in rate of production. The birds in this test year came into production much later than the stock used in 19$0-£l. Egg production peaked during September fol lowed by a decline through November. This low point in rate of pro duction was a month later in the 1950-51 data and the period of decreasing production covered a longer period. After this slump, 122 production increased during December (Figure 7) followed by a gradual decline throughout the rest of the test. However, the rate of decline was not the same for each mating type. The percent production for the purebred strains dropped off rather rapidly while the decline was less marked for the crossbreds. The average egg production of 29 hens per month for 18 strains in the 1951-52 test is given in Table Ul. The analysis of variance of tnese data is presented in Table 1*2. The mean squares for the main effects are all highly significant when compared with either the error mean square or the appropriate interaction mean square. The two interactions are likewise significantly larger than the error mean square. Least significant differences were not calculated from the within mean square of this analysis because statements about the significance of individual differences should be based on the data collected from all of the strains. However, this analysis and the one presented in Table 38 provide a more refined estimate of the error mean square or variance than the one-way analyses of variance. C. 1952-53 Test The average number of eggs for the entire flock in 1952-53 based on the number of surviving hens is 130.9 eggs (Table UJ)• The between strains mean square is highly significant (Table LU, Part I). A dif ference between any two strains of 20 or 21 eggs is the minimal number needed for significance. The mean squares for the between purebred strains and the between Incrossbreds are significantly larger than the error mean square (Table 1(4, Parts 111 and V). I 123 Purebred strain 56, a Abode island Red from the same breeder as strains 26 in 1950-51 and 3U in 1951*5% laid Significantly more eggs than any of the other "Heavy41 purebreds except strains 6U and 71* Strain 6U is an egg production strain of Hew Hampshires and strain 71 is another strain of Rhode Island Reds* The "Heavy" purebreds aver aged 32.1 eggs less than the purebred White Leghorns. This difference between the two types of purebreds is Significant* The "Heavy" crossbreds averaged to lay 131*6 eggs while the "Leg horn Type" x "Heavy" crossbred laid, on the average, 130*5 eggs* The golds and silvers (strains 67 and 66) are from the same source as those of the preceding year* The golds averaged 126.3 eggs, while the aver age number of eggs per surviving hen for the silver crossbreds is 13d.1 eggs. In two of the three years under consideration the hens from the W.P.R* x R.i.R. joating have laid more eggs (survivors' basis) tnan those from the reciprocal mating* The White Plymouth Rocks and hhode Island Reds (strains 66 and 71* respectively) are stocks from the same strains used in these reciprocal matings* The two crosses are significantly better than the White Plymouth Rocks, while only the silver crossbreds laid, on the average, significantly more eggs tnan the Rhode Island Reds. This evidence would tend to indicate that higher average survivors' egg production is more likely to result from the W.P.R. x R.I.R. mating than from the reciprocal mating* However, conclusions based on such limited data are unsound* The between mating types mean square is highly significant (Table UU, Part XI). The minimal number of eggs needed for a significant 121* difference between, any two mating types is 7.0 eggs. The average survivors* egg production for the purebred, crossbred and incrossbred mating types is 116.0, 130*5 and 11*7*7 eggs, respectively. The pure bred strains averaged significantly fewer eggs than the crossbreds or incrossbreds* The difference of 17*2 eggs between the crossbreds and incrossbreds is highly significant* In each of the three years con sidered in this study the incrossbreds have laid, on the average, more eggs on a survivors' basis than the purebreds or crossbreds. In all three years the differences between the incrossbreds and purebreds have been significant, while only in 1951-52 and 1952-53 were the dif ferences between the incrossbreds and crossbreds signifxcant. Even when the "Heavy" purebred strains are not considered, the incrossbreds averaged to lay more eggs than the purebred White Leghorns. The White Leghorn strains averaged 103*7, 119.1* and 11*0.1 eggs, respectively, for 1950-51, 1951-52 and 1952-53* Corresponding figures for the in crossbreds are 132.1, 130.2 and ll*7«7 eggs. The average within mating type coefficients of variability for tne purebred, crossbred and incrossbred mating types are 36.5* 31.6 and 27.3 percent, respectively (Table 1*3)* Th^s is the first year that the incrossbreds have exhxbxted less variation in numbers of eggs laid by tne surviving hens than the crossbreds. On a hen-housed basis the incrossbreds would undoubtedly have a greater coefficient of vari ability than the crossbreds due to the excessive mortality among the incrossbred straxns. The purebred strains as in preceding years are more variable than the strains of the other two mating types. The coefficient of variability for the entire flock is 31*6 percent. 12$ The average number of eggs laid par han housed is given in Table Uj by strain and eating type* The Rhode Island Reds, strain $6, aver aged 99*6 eggs. This strain also ranked first among the "Heavy* pure bred strains in survivors1 egg production. Most of the other strains which ranked high on a survivors' basis were also high on a hen-housed basis* The purebred strains averaged to lay on a hen-housed basis fewer eggs than either the crossbreds or incrossbreds. The average hen- housed production for the purebred, crossbred and incrossbred mating types is #6.1, 102.5 and 1 0 6 . 6 eggs, respectively. The superiority of the incrossbred mating type is less pronounced than it was when the basis for comparison was the survivors' production index. I r"N u cm AP-ONO n C M H O H ACM A A O niA I A ^ A W O n N iA cAO nO iA 0 H 4 4 ® 0 AONf^CM A 4 0) *V A 9999999999 A P-OO N © 00 A CM 4 A ® A CO HvO (MIAAI P " 0 \ O r * 4 H 0 A- ® H O n® 4 « 4 4 C M O CM * ® • t M I t I • • I • I 1 lltlllflllll t IVI1VI9VII 9 t ® P 0 n A0®P-4CM AP-P- P- 04 ^nO 4 1 A T A 4 H OnO On4 4 4N4NnOCM A H ® A H 4 P- ® ® ® ® UN 4 ® ® ® ® P- NO lAlA'O M A O n ® C^® A ® ® ® ® 4 A ® A ® A ® A ® ® <3 00 If • f> A ® ► A 4) A 4 ® A A 4 ® ® CM AOH CO O n O CNJ 0 O n ® ® O n H P - ® ® N H A ® CMH A O i H O A 0 4 if Os • A M «<«•••»••••• f 99*99*9999 t rl 3 P-OnA"P“® Np-p-®® ® ® p- !*■ On On® N On® ® ® ® ® ® ® ® A - C ^ A ® C0\ 00 r-J -On Os On OO a 0 a .13 3 j) I 3 0 A A* A® H AAP-A ? ; 3 0P-A4®®®0 0,a OnA- x)4|| n aj A P * ® 4 0 n4 H C M ( M O n 4 On 0 On A A- ® A H 4 C M 4 ® P- A- A H -N® ® ® ® OA4®CM>® ® P2 N O v ® A*AP-A-P»O n P - ® ® N s?f H H .52 n «a tn n a 2 'H & 0®AH®4P-0®CO®0 s 4 ® P-A4CM A A A ® H 4 0 4 UN 0 A 0 A * ® CM H N 04 « " fib » • ) i t i t t i • • « 99999*999*99 itiillllll » > 4 ® A ® CM ® On O n 4 4 ® a 4 o ^ ® CM 0 a a • 00 CNJ 4 A A (Aoo H A A ® 4 A H NO CM CM CM A W CM A 4 4 A CNI■rl 3 4) 0 4) W » aicm4.Hcm4 Table 35* Analyses of variance of the survivors' egg production data of 19iiO-51 by strain and mating type. Source of Variation D.F. Sum of Squares Mean Square Part I Total 91*8 2,150,21*3.50 Between strains 2? 219,101.30 8, 111*.86** Error 921 1,931,11*2.20 2,096.79 Least significant differences* P0£ level s 21.8 eggs Pq i level * 28.7 eggs Part IX Total 91*8 ------Between mating types 2 131,822.30 65,911*15** Error 91*6 2,018,1421.20 2,133*61* Least significant differences; P0£ level s 7*2 eggs PQ1 level - 9*5 eggs Part in Total 31*6 71*9,327.60 ---- Between pureored strains 9 50,550.1*6 5,616.72** Error 337 698,777*11* 2,073.52 Least significant differences* level ■ 21.1* eggs Pq2 level * 28.2 eggs Part IV Total 321* 606,080.28 Between crossbreds 9 21*,163.9h 2,685*1*1* Error 315 581,911*31* 1,81*7*31* Part V Total 276 663,013.32 --- between incrossbreds 7 12,559*56 l,79l**22 Error______269____650, l*5o * 76______2,1*18 «0l* ** Significant at P q -^ level. 128 Table 36. Analyses of variance of the hen-housed egg production data of 1950*51 by strain and mating type. Source of Variation D.F. Sum of Squares' Mean Square Part I Total 1389 5,120,621.80 Between strains 2? 310,699*67 11,507*39** Error 1362 U,809,922.13 3,531*51 Least significant differences: P05 level s 23*1* eggs PQ1 level s 3 0 . 8 eggs Part II Total 1389 - *— Between mating types 2 115,969*36 57,981**68** Error 1387 5,001*,652.1*1* 3,608.26 Least significant differences: Pq5 level s 7*7 eggs Pq^ level x 10.2 eggs Part III Total 1*95 1,553,121.73 Between purebredstrains 9 88,807*98 9,867*55** Error 1*86 1,1*61*,313*75 3,012.99 Least significant differences: Pqej level - 21.6 eggs P 01 level s 28.1* eggs Part IV Total 1*92 1,839,025.72 Between crossbreds 9 63,385*17 7,01*2.80* Error 1*63 1,775,61*0.55 3 ,6 7 6 . 2 7 Least significant differences: P0g level x 21**2 eggs Pq I level = 31.8 eggs Part V Total 1*00 1,612,501**99 Between incrossbreds 7 32,537*16 1*,61*6.17 Error______393___ 1,579,967*63______1*, 020.27 * and ** Significant at P ^ and P q -^ levels, respectively. PLHCaJT l !(— I *1’ Figure 6. Percent, hen-housed eg* production of the purebred, the of production eg* hen-housed Percent, 6. Figure 50 60 10 20 JO 0 rsbe n nrsoe otn tps n 195b-£l. in types *oatong incrossored and crossbred HOHTH Umj 129 130 Table 37. Average egg production of 26 hens per month for 18 strains in the 195u-5l test. Strain ______t Month ______Ave. Per Ave. Per Mating No. Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May Hen/Month Strain Purebred Heavy 1* 7*6 7.8 7.5 7.It 5.lt 9.3 11.0 10.6 10.lt 9.9 6.7 87.0lt 16 8.2 8,3 9.6 9.8 11.2 13.2 11.1 11.8 11.6 10.6 10.6 105.62 26 13*3 11.8 lh . 9 llt.lt 12.8 lit. 2 11.2 13.2 12.2 12.2 13.0 130.27 Group X 9.7 9.h 10.7 10.5 9.8 12.3 11,1 11.9 l l. it 10.9 10.3 107.6it Leghorn 0 10.8 7.8 7.5 7.6 6.7 11.5 10.7 18.0 11.3 12.0 9.9 98.85 15 13.0 10.3 10.1 6.8 5.5 11.6 11.8 13.8 12.1 11.8 10,7 106.58 *2 10.9 7.9 8.3 8.5 7.0 9.5 6.0 9.9 y.it 9.lt 8.9 88.68 Group X 11.6 8.7 8.6 7.6 6. it 10.9 10.2 12.1 10.9 11.0 9.8 98.10 Mating X 10.6 9.1 9.7 9.1 8.1 11.6 10.6 12.0 11.2 11.0 10.3 102.87 Crossbred Heavy 6 IP 10.2 10.2 8.8 10.3 13.2 11.7 12.lt 11.it 10.5 11.8 113.19 9 12.7 11.9 10.6 8.8 8 0 13.9 11.5 12.1 10.8 9.3 11.0 1u9.85 13.7 10.1 I0 .lt 10.2 9.2 IP 12.lt 18.5 12.5 12.9 11.9 119.19 Group X 13.5 10.7 10.it 9.2 9.3 13.8 11.9 12.7 11.6 10.9 11. It lllt.08 Leg. x H. 3 lh.8 8.7 11.7 12.5 11.8 15.0 12.1 13.5 10.5 10.6 12.1 121.15 lh 13.3 10.9 11.6 11,2 8.1 12,9 12.3 12.6 12.2 11,5 11.6 Il6.!t6 20 IP 10.7 18.3 13.lt 11.3 15.2 13.2 13.8 11.8 12.0 12.9 128.96 Group X llu l 10.1 12.2 12.3 lo .lt llt.it 12.3 13.3 11.5 U.3 12.2 122.19 Mating X 13.8 10.lt 11.3 10.8 9.9 IP 12.2 13.0 11.5 11.1 11.8 118.13 Incrossbred Group 1 5 lh.8 11.7 10.3 10.7 10.9 lit. 2 13.3 13.7 13.0 11.7 12.3 121t.M 13 15.0 IP 15.5 12.7 10.5 13.5 11.7 12.3 11.7 12.6 12,9 129. It2 27 15.2 13.3 13.0 llt.O 18.9 15.7 12.8 I3 .lt 12.7 13.1 18.9 139.28 Group X 15.0 13.0 13.7 12.lt 11.8 lh. 5 12.7 13.2 12.5 12.5 13.1 I 3I.I 8 Group 2 2 lU.o 10.6 11.3 12,7 12.3 lit. 6 10.9 12.3 11.2 9.5 12.0 119.65 10 13.0 l l . l t 10.7 12.3 10.it 13.8 12.1 12.3 11.3 12.2 12.1 120.65 28 15-5 13.8 Ip. 7 12.9 11.8 13.9 11.1 lit* 3 12.2 11.5 10.1 130.77 Group X l p 11.9 11.9 12.7 11.3 I P l l . i t 13.2 11.7 11.1 12.it 123.69 Mating X lh.6 12.3 12.8 12.6 11.6 lit. 3 12.0 13.2 12.1 11.3 12.7 12?.Itlt Monthly X u .o 10.7 11.3 10*8 9.9 13.8 11.6 12.7 11.6 11.3 11.6 116.18 131 Table 36. Analysis of variance of the egg production data of 1950-51 by strain, mating type, montn and &roup. Source of Variation b.F. Sum of Squares Mean Square Total 1*67 9 186,11*2.36 --- Between Hating types 2 1*, 798.88 2,399.1*1*-** Strains within matings 15 9,283.99 618.93** Months 9 5,102.72 566.97** Groups within matings 3 5,629.19 1,876.UO** Interaction Hating type x month 18 1,379.21* 76.62** Strain x month 135 6,272.17 1*6.1*6* Error 1*1*97 153,676.19 31*. 17 * and ** Significant at and **01 levels, respectively. 132 Table 39* Average egg production for 1951-52 on a survivors' and hen-housed basis. Survivors1 ”~Een-Housed T & t T Strain No. of Ave. No. Std. C.V. Ave. No. in No. 11a ting No. Birds * 8 ® Error CD Eggs of Eggs Purebred Heavy 33 30 80.1 9.2 62.8 61.3 18.8 31** 35 113.9 5.7 29.7 8 7 . 8 26.1 39 1*1* 103.7 5.2 33.1 92.5 1 1 . 2 1*0 1*3 81.8 6 .1* 51.2 71*. 8 7.0 1*6 29 82.9 7.0 1*5.5 61.5 2 1 .1* 1*8 36 9 0 . 6 6 . 1 1*0.5 7 2 . 0 1 8 . 6 1*9 30 91.3 7.6 1*5.5 63.1* 27.9 56 37 8 6 . 1 5.3 37.5 6 9 - 6 16.5 Group X — 91.7 6.5 1*2 . 1 72.9 18.9 Leghorn 37 1*7 115.9 6 . 0 35.7 1 1 1 . 6 1**3 1*7 39 131.9 5.2 21*. 5 111*. 2 17.7 52 35 1 1 0 . 2 7.9 1*2 .1* 85.1 25.1 Group X — 119.1* 6 .1* 33.8 1 0 3 * 6 1 5 . 8 Hating X — 1 0 0 . 0 6.7 1*0 . 6 81.3 18.7 Crossbred Heavy 35* 1*0 1 1 0 . 6 5.9 33.7 92.7 17.9 1*1* 1*3 116.1* 5.5 31.0 103.1* 13.0 1*2* 1*1 117.6 6 . 0 32.7 99.5 18.1 Group X — 111*. 9 5-8 32.1* 98.5 1 6 .1* Leg. x H. 38 29 131.3 7.2 2 9 . 6 83.1* 1*7.9 1*3 31* 129.9 6 .1* 28.7 1 0 0 . 8 29.1 % 1*2 137.5 6 . 0 28.1 113.1* 19.1 Group X — 133.3 6.5 28.7 100.9 32.1* Hating X — 123.1* 6 . 1 30.7 99-7 23.7 Incrossbred 30 31 129.9 7.6 32.5 8 6 . 2 1*3.7 31* 31* 122.9 6 . 0 37.8 102.9 2 0 . 0 32 29 116.5 6 . 8 31.3 76.1 1*0 .1* 36* 39 135.3 l*.l* 2 0 . 1 113-1* 21.9 1*5 31* 1 5 1 . 0 5*7 2 2 . 1 111.1* 39.6 50 37 H*o.5 6 . 2 2 7 - 0 1 1 1 . 0 29.5 51 39 135.9 8 . 1 37.3 109.1* 26.5 51** 32 135-7 8 .1* 35.0 1 0 0 . 6 35.1 55 39 1 0 3 . 6 7.0 1*2 . 1 9 0 . 0 13.6 Hating X -- 130.2 7.0 31.7 1 0 0 . 1 3 0 . 1 Flock X — 115.7 6.5 31*. 2 9 2 . 0 23.7 Indicates those strains which were .included j j » each of the last three years. 133 Table 1*0. Analyses of variance of the survivors' egg production data of 1951-52 by strain and mating type. Source of Variation D.F. Sum of Squares Mean Square Part X Total 91*7 1,806,522.70 Between strains 25 367,265.70 1U, 690.63** Error 922 1,1*39,257.00 1,561.02 Least significant differences! level - 16.1 eggs p05 P 01 level s 23.9 eggs Part II Total 9U7 --- ... Betweenmating types 2 176,993.55 89,1:96.78** Error 9US 1,627,529.15- 1,722.53 Least significant differences: p05 level — 6.5 eggs PG1 level m 6.5 eggs Part i n Total u o k 713,530.91: ... Between purebred strains 10 61*, 837.23 6,1*83* 72** Error 391: 61*8,693.71 1,61*6.1(3 Least sxgnificant differences: p o5 level z 16*5 eggs P01 level s 21*. U eggs Part IV Total 226 338,690.92 ... Between crossbreds 5 19,315.23 3,863.05* Error 223 319,375.69 1,1*32.16 Least significant differences: level z 17.0 eggs p o5 level r 22.U eggs P01 Part V Total 313 57^,307.29 ... Between incrossbreds 8 56,883.20 7,110.1*0** Error 305 518,1*21*. 09 1,699.75 Least significant differences: level — 19*U eggs * 0 5 *01 level * 25*5 eggs * and ** Significant at P q ^ and PQ1 levels, respectively. Table Ul. Average egg production of 2y dens per month fo r 18 strains in tne 1951-52 test. „ Month _ Ave. Per Ave. Per Mating No. Aug. Sept. Oct. Nov. Dec. Jan. Peb. Kar. Apr. May Hen/rionth Strain Purebred Heavy 39 5.5 10.7 13.6 104 12.8 124 9.7 6.3 9.2 8.3 10.1 101.0 1*6 5.7 6.8 7.5 6.6 114 10.2 7.9 7.8 7.9 6,8 7.9 78.5 1*9 2.3 7.5 9 4 8.8 12.1 11.6 8.7 8.7 8.7 8.0 8.6 85.8 Group X It. 5 8.3 10.2 8.6 12.1 114 8.8 8.3 8.6 7.7 8.6 884 Leghorn 37 114 11.7 11.5 10.2 12.5 13.5 10.6 10.7 8.8 8.6 10.9 109.5 1*7 10.7 11,8 13.9 11.0 13.9 15.0 11.6 10.7 11.6 12.7 12.3 122.9 % 6.8 11.6 11.9 8.5 12.1 13.3 I 0.6 9.5 9.9 9.8 104 103.9 Group X 9.6 11.7 124 9.9 12.8 13.9 10.9 10.3 10.1 104 11.2 112.1 Mating X 7.1 10.0 11.3 9.3 12.5 12.7 9.8 9.3 9.3 9.1 10,0 100.3 Crossbred Heavy 35 lt.6 9.8 11.6 10.9 134 11*. 7 11.3 9.5 11.6 11.2 10.9 108.6 1*1 8.3 12.1 13,6 10.2 124 12.6 11.0 11.3 12.1 10.1 114 113.6 1*2 6.3 10,7 12.6 10.2 12.5 li* 4 11.5 9.9 12.? 12.1 11.3 113.0 Group X 6 4 10.9 12.6 104 12.8 13.9 11.3 10.2 12.1 11.1 11.2 111.7 Leg. x H. 38 8.2 11.9 lli.6 10.9 lit.3 13.7 134 12.6 13.5 11.9 12.5 125.3 1*3 lt.9 11.7 13.5 13.0 lli.6 15.3 12.9 12.9 4 4 12.2 12.5 1254 hh 7.3 12.0 16.2 154 llt.9 15.8 12.1 12.2 12.6 12.8 13.1 131.3 Group X 6.8 11.9 11*. 8 13.1 lli.6 11*.9 12.8 12.7 13.5 12.3 12.7 127.3 Mating X 6.6 114 13.7 11.8 13.7 11*4 12.0 114 13.8 11.7 11.9 119.5 Incrossbred Group 1 30 11.1 lil.2 15.9 12.3 lli.6 lli.O 12.0 11.1 10.7 9.1 12.5 125.0 36 6.2 13.2 154 13.0 11*.9 13*5 12.1 11.8 13.1 124 12.6 125.6 130.7 -51* «*• 8.3 13.1 15.0 12.9 11*4 4 4 12.6 13.0 13,3 13.5 13.1 Group X 8.5 13.5 15.5 12.8 11*. 6 4 .0 12.2 12.0 124 11.7 12,7 127.1 Group 2 31 9.7 12.0 12.6 10.9 13.1 13.6 12.0 10.1* 11.3 11.8 11.7 117.3 1*5 11,2 15.3 16.8 13.2 15.8 17.1 13.5 13.6 4*2 15.2 4 .6 11*6.0 % 10.1 13.8 15.3 13.3 lli.6 15.1 13.3 12.5 4 .3 13.1 13-5 135.3 'Group X 10.3 13.7 1 it. 9 12.5 4 .5 15.2 12.9 12.2 13*3 13.3 13.3 132.9 Mating x 9 4 13.6 15,2 12.6 lk .6 lli.6 12.6 12.1 12.8 12.5 13.0 130.0 1 3 5 Table 1*2. Analysis of variance of the egg production data of 1951- 1952 by strain, mating type, month and group. Source of Variation D.F. 3urn of Squares Mean Square Total 5219 198,81*2.1*3 --- Between Hating types 2 7,909-38 3,951*. 90** Strains within matings 15 11*, 21*9.18 91*9.95** Months 9 11*, 811*. 26 1,61*6.03** Groups within matings 3 11,51*7.1*1* 3,81*9.15** Interaction Hating type x month ia 1,231.62 68.1*2** Straxn x month 135 5,680.13 1*2.08** Error 5 0 3 7 11*3 ,1*1 0 .1*2 28.1*7 ** Significant at *01 level. PLrf'L-i.'i d g Figure 7* Percent hen-housed egg production of the purebred, the of production egg hen-housed Percent 7* Figure 10 0 2 crossbred and incrossbred n 136 i 137 Table 1*3. Average egg production for 1952-53 on a survivors* and hen-housed basis* Survivors1 Wen-Housed DTff. ” Strain No. of Ave. Mo. Std. C.V. Ave. No. in No. Mating No. Birds Eggs Error W Eggs of Eggs Purebred Heavy 50 28 96*7 11.1 60.5 69.3 27.1* $3 30 92.0 7.1* UU* 2 68.2 23.8 51* 31* 98.5 5.1* 31.9 75.1 23.1* 56* 31* 129.8 6.6 29.8 99.8 30.0 61 27 98.5 8.7 1*5.8 66.5 32.0 61* 28 126.8 8.9 37.2 66.6 1*0.0 68 1*2 102.6 5-6 35-6 90.1 12.5 71 38 116.5 7.9 1*1.6 99.1 17.1* Group TL — M 106.0 7.6 1*0.2 81.9 26.1 Leghorn 58 30 138.8 7.2 28.3 100.6 38.2 65 1*0 11*0.7 6.6 29.8 116.9 23.8 69 17 11*1.2 7.2 21.0 71*. 1* 66.6 Group X — 11*0.1 7.2 27.8 97.3 1*2.8 Mating X — 116.0 7.5 36.5 86.1 29-9 Crossbred t Heavy 51* 29 130.1* 7.5 30.9 90.5 39.9 66* 36 138.1 6.1* 28.6 117.0 21.1 67* 1*1 126.3 5.2 26.1* 109.1* 16.9 Group X — 131.6 6.3 28.5 1 0 5 . 6 26.0 Leg* x H. 55 32 11*1.3 9.1 36.1* 109.0 32.3 62 35 119.9 7.2 35.6 98.5 21.1* 76 28 127.2 7.9 32.8 90.3 36.9 Group X — 129.3 8.1 35.2 99.3 30.0 Mating X — 130.5 7.1 31.8 102.5 28.0 Incrossbred 52 37 155-8 7.1* 28.8 128.7 27.1 57* 31 11*3.6 6.2 23.8 1 0 5 . 6 38.0 59 25 138.3 7-8 28.0 90.3 1*8.0 6 0 38 161*. 2 6.6 21*. 9 132.1* 31.8 63 28 121*. 9 9.5 1*0.1 81.6 1*3.1 70* 28 11*9.1* 8.0 28.1* 98.2 51.2 72 31* H*5.o 5.1* 21.6 108.6 36.1* 73* 37 161.0 5.9 22.2 131.3 29*7 71* 30 11*1.1 6.5 2 5 . 2 106.1 35.0 75 21* 11*0.8 9.9 31**3 85.2 55-6 Mating X — 11*7-7 7.2 27.3 106.8 1*0.9 Flock X — 130.9 7.3 31.6 97.1* 33.5 Indicates these strains were included In each of the last three years* 138 Table Vi- Analyses of variance of the survivors1 egg production data of 1952-53 by strain and mating type. Source of Variation D.fr* Sum of Squares Ikean Square Part X Total 862 1,762,695»50 — Between strains 26 330,601-60 12,707-75** Error 836 1,632,296-10 1,713-27 Least significant differences: Pq5 level s 20.3 eggs PQ1 level * 26.7 eggs Part II Total 662 — --- Between mating types 2 165,762.39 82,881.20** Error 860 1,696,933-11 1,856*90 Least significant differences: Pq5 level - 7.0 eggs Pq1 level - 9-3 eggs Part III Total 3U7 718,202.97 Between purebred strains 10 116,612-68 11,661-27** Error 337 603,790.29 1,791-66 Least significant differences: Pgg level - 20.9 eggs P 01 level =27-5 eggs Part IV Total 202 369,236.75 Between crossbreds 5 10,865-08 2,169*02 Error 197 338,391.67 1,717-72 Part V Total 311 529,693-39 Between incrossbreds 9 39,381.21 6»375-69** Error 302 690,112.18 1,622.69 Least significant differences: P0£ level s 20.0 eggs P01 level = 26.3 eggs ** Significant at Pq -^ level. 13 9 Ill. Discussion The second major objective of the project was to evaluate and compare the uniformity of egg production of purebred, crossbred and incrossbred poultry* Since the initiation of laying contests about 1 9 0 0 , the problem of evaluation has been of utmost importance not only to the prospective purchaser of chickens but also to the breeder* In reality both the purchaser and the breeder are interested in the same things* The purchaser desires a strain or breed that will grow, live and lay better than any other and the breeder wants to be able to supply this stock* The Standard Egg Laying Contests provided for a number of years the best information on the performance of stock in competitive conditions* There are many obvious faults with these contests. While the Record of Performance programs serve a useful purpose, all results are obtained on the breeder*s own farm and as such do not give the best possible information on the performance of a strain in different locations* In recent years Random Sample Tests not only for growth but also for egg production have been started* To date they provide the best data we have on the relative performance of poultry. The present project differs rather markedly from the Random Sample Tests. The major difference between the Random Sample Tests and this project is that the strains were intermingled through out the test period, i.e. they were brooded, reared and housed inter mingled. A second and possibly equally important factor in view of the high mortality records, is the use of old, compost type litter in the brooder, colony and laying houses. U*G During 1950-51, 1951-52 and 1952-53, 32 strains of purebreds, 22 kinds of crossbreds and 27 groups of incrossbreds were utilized in the project* For the most part different pure strains crosses and line numbers of incrossbreds were used, however, the 7 groups marked with asterisks were included in each of the three years. The purebreds were selected on high egg production records in Egg Laying Contests or Record of Performance summaries. Influencing the selection of the pure strains was the desire to obtain strains wh^ch are representative of the breed. The incrossbreds in each year laid more eggs, on the average, than the crossbred and purebred strains. Knox (191*6) found that tne progeny produced from inbred Rhode Island Reds mated to inbred White Leghorns gave superior results in annual egg production to the pure bred Wnite Leghorns and Rhode Island Reds. He reported that the incrosses and topcrosses did not lay as well as the incrossbreds but were on an equality with the outbred Reds and Leghorns. Maw (19U9) observed that progeny from crosses between inbred lines of the same breed lay fewer eggs than his high producing control strain. Inbred families of Leghorns, New Hampshixes, Rhode Island Reds and White Plymouth Rocks were crossed in 227 combinations of Leghorns with other breeds by Dickerson, et. al.(1950)* Compared with the mean of the intra-breed crosses, the Leghorn x Hampshire and Leghorn x Red cross breds laid 8 - 9 eggs more during a production period from 1 5 U to 3 0 0 days of age. Hueller (1 9 5 2 ) reported tnat crossbred pullets laid at a higher rate tnan inbred-hybrid pullets until April when the superi ority was reversed. Tne results of this project are conflicting m relative to the rate of lay. In 1950-51# th® Incrossbreds laid at a higher rate (hen-housed) than the crossbreds until April when the superiority was reversed. In 1951-52, the incrossbreds laid at a higher rate from August to October, thereafter the crossbreds were superior to the incrossbreds in rate of lay. Accumulating data (Warren, 19U2; Knox, 1936; Jeffrey, 1939$ Sostian and Dearstyne, 191*2; Knox, Gordon and Hehrhof, 19U9 and many others) indicate that crossbreds may be equal, superior or inferior in egg production to the parental lines used in the cross, depending on the quality of the parental lines. The results of this project indicate that, on the average, crossbreds produce more eggs than pure bred strains. Since the parental stock was not tested, there is no way of ascertaining the influence of the quality of the parental stock on the quality of the crossbred progeny. It is of interest to note that the difference between the production of the crossbreds and purebreds was greater than the difference between the crossbreds and incrossbreds. The results tend to indicate that for egg production the crossbreds are equally as good as the incrossbreds when laying house mortality and initial chick price are considered. Possibly if the effort spent on inbreeding had been directed at testing more crosses and improving the best of these, the resulting crossbreds would be equally as good as any other egg producer now available. It is possible that crossbreds might be improved more rapidly than incrossbreds due to the lack of necessity for severe inbreeding. In crossbreeding program, it might be useful to employ the inbreeding 1 U 2 technique as a means of increasing the variation between dam or sire families. Egg production varied considerably from year to year. The aver age egg production (based on survivors' data converted to 7 day equi valents) in 1950*51# 1951*52 and 1952*53 is 168.6* 162.0 and 183*3 eggs* respectively. Corresponding figures on a hen-housed basis are 129.0* 129.0 and 136.U eggs* respectively. The 7 strains which were repeated during the last three years averaged to lay (survivors* data converted to 7 uay equivalents) in 1950-51# 1951*52 and 1952-53# respectively* 18U.0* 171*8 and 195*1* eggs* The differences in egg production (survivors' basis) for these 7 strains between years are highly significant. In 1951-52* average egg production was much less than in the other two years. It will be recalled that the birds did not grow as well in 1951*52 as in the other two years. Just what factors are involved cannot be ascertained. Apparently environmental factors caused the poor performance in this year. While the incrossbreds laid more eggs than the crossbreds or purebreds* it is possible to select strains of Khode Island Reds or White Leghorns that will lay and live as well as the incrossbreds. When laying house mortality and chick price are considered* the pure bred Rnode Island Reds* White leghorns or egg production strain of New Hampshires would be chosen for commercial egg production. IV • Summary The following summary statements can be made from the egg pro duction studiest 11*3 1. The incrossbred strains averaged to lay more eggs than either the crossbred or purebred strains* Tne three year aver age superiority of the incrossbreds over the purebreds and cross breds amounts to 1*1 .1* and 13*7 eggs, respectively (survivors' data converted to 7 day equivalents). Corresponding figures based on hen-housed averages are 29*0 and 6 *9 eggs, respectively* The differences between the purebred and incrossbred mating types are significant in each year. The crossbreds averaged significantly fewer eggs than the incrossbreds in 1951-52 and 1952-53* 2* There is evidence of hybrid vigor for egg production but not for laying house mortality* The purebred strains exhibited lower average mortality in two of the three years than either the crossbred or incrossbred strains. Possibly, mortality as it was experienced in these tests may have been the major factor in differentiating strains for reproductive fitness* 3* Hen-housed production data provide a more critical evaluation for individual strains or the mating types than survivors' pro duction data. However, the three mating types are ranked the same whether the rating is made on a hen-noused or survivors' basis. Individual straxns may be ranked differently depending upon the amount of mortality* U* Egg production varies considerably from year to year depend ing upon non-heritable factors* The average number of eggs for the entire flock (survivors' index converted to 7 day equivalents) m I k k in 1950-51, 1951-52 «nd 1952-53 la 1 6 8 .6 , 162.0 and 183*3 eggs, respectively* Corresponding figures on a hen-housed basis are 129*0, 129*0 and 136.U eggs respectively. 5* The incrossbreds of 1950-51 laid at a higher rate from August to April than the purebreds or crossbreds but during Hay the crossbreds laid at a higher rate than the incrossbreds. In 1951- 52, the incrossbreds were superior to the crossbreds from August through October, after which the superiority was reversed. In both years there was a decline in rate production from August to November or December followed by an increased rate of production during the following month. The decline in production was not the same for the three mating types* 6 . It is possible to select strains of White Leghorns, Rhode Island Reds and New Hampshires that will lay as many eggs as the average incrossbred or crossbred* ALBUMIN QUALITY I. Materials and Methods A saiaple of eggs was obtained from each strain three times a year for albumen quality studies. In 191*9-50, the samples were se cured in July, December and March* The July sample consisted of only 20 eggs while the December and March samples were of 30 eggs each. During the last three years of the project (1950-1953) the eggs for albumen quality work were collected during September, Decem ber and March* Each sample consisted of 30 eggs from each strain* The egg a were taken from the trap-nests at hourly intervals and placed in a refrigerated egg room (held at approximately 5 5 ° F) twice daily. Due to differences in rate of egg production and laying house mortality, it was not possible to obtain a 20 or 3 0 egg sample from each group in one day. Usually a time interval of three or four days was required in order to collect the desired sample* At the end of each collection day, the eggs were sorted by strains and each sample was reduced to the number of eggs present in the smallest group. Each sample when complete contained an equal number of eggs of the same age. The samples were also sorted by hens and as much as possi ble only one egg per hen was used in each sample. It would have been highly desirable to have used only one egg per hen for these studies 12*6 since there is remarkable consistency in the albumen scores for the eggs from individual hens* Nordskog and Cotterill (1953) reported repeatability values of about 0.75 for albumen height and for the Haugh unit* The eggs were broken out at the end of the sampling period and compared with the photographic standards proposed by Van ttagenen and fcilgus (1935)* This method of determining albumen quality was se lected over other methods for two major reasons, namely, its applica bility to a project of this scope and because any breeder could use the technique without special skill or training. The Van Viagenen- Wilgus standards are designed for fresh eggs while the U. S. D* A* Scoring Chart is set up for eggs that have been held in storage (personal communication to Dr. Jaap from Dr. Brant, 1953)• Brant and Shrader (1952) published the U. S. D. A. Scoring Chart* The U* S. D* A. Chart would not be suitable for this project since fresh eggs were used. The "Haugh unit" method (Haugh, 1937) provides a continuous, objective measure of albumen quality and it takes into account egg weight as well as height of the albumen. This technique is slow, requires an expensive micrometer and from a comparative point of view probably does not furnish any more information than the visual method utilized. The technique used by Holst and Almquist (1931) of obtaining the percent of firm albumen is likewise a tedious process and was not considered for this reason. The eggs used in any one sampling period were all scored by the same individual and the breaking process was completed in one day. 1U7 The eggs were broken out on a flat surface and placed for scoring on an apparatus similar to that pictured and described by Thayer (19145)* however, two modifications were made in his device. First, a third mirror was placed below the glass plate to facilitate the detection of blood spots on the undersurface of the yolk and, secondly, instead of naving the glass plate level, the glass was adjusted so the eggs would slide slowly toward one end of the glass and drqp into a oontii— f» Two types of analyses have been performed on the albumen quality scores* Since the score for the observed condition of the firm al bumen is a subjective measure at best and because only a few of the nine possible classes are realized in fresh eggs or in eggs refrig erated for three days, the data have been treated as a discrete variable. It is granted that the variable, albumen quality, may be a continuous rather than discrete variable when measured differently, however, the Van Wagenen-Wilgus scoring system imposes discreteness upon the variable* The chi-square technique was applied to the data of each sampling period by choosing an albumen score such that at each sampling period approximately fifty percent of the eggs were better and fifty percent were poorer than the chosen score* For example, in the September sampling period of 1952-53 the eggs were dxvided into two groups by placing those with scores of 1*0 in one category and those with scores of 1*5 and below (2 *0 , 2*5 etc.) into a second class. This division placed 38.6 percent above and 61.2 percent below the division point. In the December and Kerch sampling periods, the eggs were separated into two groups by placing those eggs with scores of 1.0 or 1*5 in one group and those with scores IfeB of 2.0 or lower into the second class* A chi-square test of indepen dence was computed for each of the three & x 2 tables in each year* The expected frequencies were calculated from the observed frequencies for the entire group of chickens in any given sampling period and woe based on the assumption that there is no real difference in albumen quality score between the various strains* Similar tables were con structed and analysed for differences between strains within the major breeding or mating types, i.e. purebred, crossbred and incrossbred* A similar procedure was used to analyze for differences between mating types with one exception* Instead of dividing the scale of scores into two divisions, three or more divisions were made. As a result of combining the different strains within a mating type, the number of eggs in the poorer quality classes was increased sufficiently to warrant the third or fourth division* Also,.an equal number of stains within each mating type was used so that the same number of eggs were considered in each case* In 1950-5 1 * B strains per mating type were subjected to the chi-square analysis, while in 1951-52 and 1952-53 there were only 6 strains in each classification. These chi-square analyses provide information on the significance of differences be tween all strains considered as a group, between strains within mating types and between mating types, but it furnishes no information about the performance of one strain throughout the year, strain x sampling period interaction or other interactions of interest, ho concise rep resentation of the data can be made from this type of analysis* The necessary calculations become quite lengthy and tedious* For these reasons a second type of analysis was introduced. In order to overcome these diff iculties, a technique proposed by Lush, Lamoreux and Hazel (19U8) was utilized. These investigators presented a method of handling binomially distributed variables in the analysis of variance form. The all or none variable with which they worked was resistance to death. Vihile it might be argued that the phenomenon— resistance to death— is continuously and probably normally distributed, these workers observed that the data at the end of the year must necessarily fall into two mutually exclusive classes, i.e. the birds are alive or dead. In the case of albumen quality scores an analogous situation, although admittedly less rig orously defined, can be proposed. The eggs could be conceivably divided for analytical purposes into two arbitrary groups, those possessing "good*1 albumen quality and those possessing "poor" al bumen quality. The scoring system used in this study provides that the two divisions were mutually exclusive because each egg can re ceive but one score. For our purposes this arbitrary division was made so that 2 0 or more percent of the eggs fell into the HpoorM classification* It is advisable to avoid small percentages of “poor" quality eggs since the variance is related to the mean in a binomial distribution. The division point was not necessarily constant from one sampling period to the next or from year to year. For instance, in 1 9 U9 - 5 0 it was necessary to consider each sampling period sepa rately because the albumen quality scores varied greatly from period to period. In 1950-51* the September and December sampling periods were combined in the same analysis, while in 1 9 5 2 - 5 3 it was possible to combine the December and March data* The data from all three sampling periods of 1951-52 were analyzed in one analysis. Not all of tne strains in a given year were included in these analyses* This was done to avoid unequal subclass numbers* In 19U9- 5 0 , the test birds were from U pure strains, U strain crosses and 7 kinds of crossbreds* Three kinds of crossbreds were randomly dis carded from tne group of seven so that there would be U stiaxiis w j .th in each mating type* Eighteen strains consisting of 6 strains of purebreds, 6 groups of crossbreds and 6 kinds of incrossbreds were used in the 1950-51* 1951-52 and 1952-53 analyses. Whenever there were more than 6 strains within a mating type, the 6 strains to be used were randomly selected by utilizing a table or random numbers* The method of analysis can be illustrated by using the data col lected in 1951-52. A summary of the number of "good** and "poor" quality eggs for each of the 18 strains, the 3 mating types and the 3 sampling periods is presented in Table 56* The major factors con tributing to the observed variation in number of "good" and "poor** quality eggs are mating types, strains within mating type and sam pling periods. Two first order interactions are also of interest, namely, mating type x sampling period and strains withxn mating type x sampling period. The sum of squares for the analysis of var iance table are calculated in the following manner* 1. The total sum of squares are given by* 151 where Ctj, and P^ are the total number of "good* and "poor* quality eggs, respectively* k s . 366*73. 2* The between mating types sum of squares are given by* 3 G . P B =A- V * » m^l where implies a summation of the ratios obtained for each of the three mating types and and Pm are the number of "good" and "poor" quality eggs laid by the m ^*1 mating type, respectively* B = 366.73 - B = 366.73 - 359*35 = 7*36. 3. The between strains within mating type sum of squares are obtained from* J L Gm . Pm & G. • P. ' S T % + rm ' i=l 0i+ Pj. where G^ and are the number of "good" and "poor" quality eggs laid by the i*^1 strain, respectively and the summation is over .i s 1,2, ... , Id strains. C = 359.35 - f C = 359-35 - 3^5*59 s 13*76. U* The between sampling periods sum of squares are calculated by: where Gj and are the number of "good" and "poor” quality eggs laid in tne sampling period, 3 si, 2, and 3. D « 366.73 - 362.79 s 3.9k. 5. The mating type x sampling period sum of squares are given by; E = A _ £ • (B ♦ D) , “J*1 . °oj ♦ Pmj where and P ^ are the number of "good" and "poor" quality eggs, X L X u respectively, of the m ™ 1 mating type in the jvn sampling period. E s 366.73 - - (7.38 *3«0. E = 366.73 - 352.71 - 11.32 s 2.70. 6. The strain x sampling period sum of squares are obtained from; 5k Gj j • Ps j F ; A - .""a * i p * (C ♦ D) , ij=l ij where and P ^ are the number of "good" and "poor" quality eggs, respectively, of the i^h strain in the sampling period. F : 366.73 - F = 366.73 - 328.k3 - 17.70 s 20.60. 7* The error sum of squares were obtained in the usual manner» 153 11• Results The frequency distribution of egg albumen scores of the December sampling period of l?U?-50 is presented in Table U5* Mean albumen scores for the purebred, crossbred arid incrossbred strains for 1?U9 through 1953 are tabulated in Table I46* The R x 2 tables o f albumen scores on vhxch chi-square tests of independence were computed are presented in Table k7, 50, 5k and $8 . Summarized in Tables 51# 55 and 59 are the R x C tables of albumen scores and the calculated values of chi-square for each sampling period. The number of "good" and "poor" quality eggs laid by the purebred, crossbred and incross bred straxns are summarized in Tables I48, 52,56 and 60. The analyses of variance of these data are given in Tables k9, 53, 51 a n d 61* Table it5* Frequency distribution of egg albuaen scores in the December sampling period of 1919-50. Score 1 Bxl Cxi B A x B CxB DxB c IxC D Ax £> BxD Ox£> T S e U l 1.0 9 6 6 5 3 11 3 6 5 9 5 8 13 ii 97 1*5 13 12 8 u ll 7 13 7 5 11 10 lii 12 6 12 152 2,0 7 7 9 7 8 5 6 5 10 5 7 2 2 5 8 93 2*5 2 1 2 2 2 6 5 3 1 - 1 2 ii - 31 3*0 - - 3 3 1 - 1 1 3 2 3 1 1 3 - 22 3.5 1 - 1 1 1 2 1 2 2 - 3 1 - 3 2 20 ■*, 1*0 * 2 1 h 3 - 1 2 2 2 3 5 ii 35 5.0 -Jt CM CM o, -1 . • X 1.5 1.8 2.0 1*9 2.i 1.8 1*9 2.2 2.1 1*7 2*0 1.8 . 1*9 * 1 5 5 Table 1*6. Average albumen quality scores for the purebred, crossbred and incrossbred strains in ! 9 k 9 - $ 0 , 1950-51# 1951-52 and 1952-53. Mating 111 Year Month purebred Crossbred Incrossbred 8 Warns 191*9-50 July 1.1*0 1.31+ — 1.37 December i . a y 1.93 — 1.92 nai’Cii 2 .3 a 2.16 — 2.22 1950-51 September 1 . 6 0 1.61+ 1.69 1.61+ December 1.73 1.82 1.81 1.77 hared 2.22 2.31 2.21 2.25 1951-52 September' 1.59 1.63 1.78 1.66 December 1.50 1.68 1.51* 1.56 harch 1.60 1.75 1.82 1.71 1952-53 September 1.37 1.37 1.1+7 1.1+0 December i . a i 1.78 1.85 1.82 March 1 . 66 1.72 1.78 1.72 156 Table U7. Analysis of strain differences in egg albumen quality scores by the Chi-square technique (1949-50)* Sampling Period July December March Score 1.0 1.5-5*0 1.0-1.5 2.0-5*0 1.0-2.0 2.5-5*0 Strain A 7 13 22 8 24 6 A x B 5 17 18 12 24 6 A x C 10 10 20 10 20 10 A x D 4 16 25 5 12 18 B 3 17 14 16 11 19 B x A 5 15 18 12 24 6 B x D 12 8 10 20 IS 15 C 11 9 10 20 12 18 C x A 9 11 14 16 19 U C x B 11 9 16 14 16 14 C x D 7 13 16 14 15 15 D 10 10 22 8 12 18 D x A *8 12 16 14 21 9 D x B 7 13 13 17 23 7 D x C 12 8 15 15 13 17 Total 119 181 249 201 261 189 Percent of sample total 39. 7 60.3 55*3 44*7 58.0 42.0 Chi-square 26.57* 35*30** 47*28** * Significant at Pq ^ level. ** Significant at Pq ^ level. 157 Table 1*3• Summary of the 19l*9“50 egg quality data by number of "good” and "poor" quality eggs laid by 12 strains* Sampling Period December Karen Boo'd" Poor total Good foor Total Good Poor Total noting Purehred A 7 13 20 22 8 30 21* 6 30 B 3 17 20 H* 16 30 11 19 30 CU 9 20 10 20 30 12 18 30 D 10 10 20 22 8 30 12 13 30 Total 31 1*9 30 68 52 120 59 61 120 Strain Cross A x B 3 17 20 18 12 30 21* 6 30 B x A 5 15 20 18 12 30 21* 6 30 C x D 7 13 20 16 11* 30 15 15 30 D x C 12 a 20 IS 15 30 13 17 30 Total 27 53 80 67 53 120 76 1*1* 120 Crossbred A x D 1* 16 20 25 5 30 12 18 30 B x D 12 3 20 10 20 30 15 15 30 C x B 11 9 20 16 11* 30 16 11* 30 D x B 7 U 20 13 17 30 23 7 30 Total 31* 1*6 80 61* 56 120 66 51* 120 Sample Total 92 11*8 21*0 199 161 360 201 159 360 Table 1*9• Analysis of variance of the egg quality data of 19l*9“5o by strain and mating type. Source Sampling Period of July December March Variation 'iJ •t'» 239 .2371* 359 .21*79 359 .21*73 Strain No. Sam cling Period September December Harch Score 1.0-1.5 2 .0 -5.0 1 .0 -1 .5 2 .0 -5.0 1 .0 -2.0 2 .5 -5 .0 Hating Furebred i* 21* 6 19 11 23 7 a 17 13 12 18 13 17 16 20 10 19 11 13 17 16 - 18 12 15 15 15 15 22 17 13 2k 6 12 18 2k 13 17 20 10 16 lii 26 21 9 17 13 20 10 0 26 U 20 10 16 12 15 19 11 16 lii 12 18 19 19 11 16 lii 17 13 Hating total 19k 106 178 122 159 i i a Fereent of total 61*-7 35.3 59.3 U0.7 53.0 U7.0 Chi-square value 17. 83* 13. 77 1 6 .20 Crossbred 1 lii 16 22 8 11 19 6 15 15 15 15 11 19 7 25 5 19 11 2Ji 6 9 21 9 20 10 18 12 17 15 15 17 13 7 23 21 21 9 18 12 7 23 3 22 6 20 10 16 lii Hi 18 12 12 18 17 13 20 16 12 19 11 10 20 25 13 17 9 21 15 15 Hating total 162 116 171 129 136 16U Fercent of total 60.7 39.3 57.0 U3.0 U5.3 5U.7 Chi-square value 19. 75* 19. 70* 35. 00** Incrossbred 11 10 20 16 lii 20 10 12 17 13 23 7 19 11 2 19 11 21 9 17 13 5 20 10 13 17 lii 16 10 21 9 19 11 21 9 13 21 9 15 15 17 13 27 Hi 16 17 13 18 12 26 18 12 15 15 21 9 Hating total liiD 100 139 101 lli7 93 Fercent of total 58.3 ia. 7 57.9 ii2.1 61.3 38.7 Chi-aquare value _ 13-93 1 0 .93 5.67 Sample total 5 l6 32ii Ii8d 352 kk2 398 Fercent of total 6 1 .h 36.6 58.1 ia.9 52.6 ii7.1i Chi-aquare value 53.89** Uii.75** 69.80#* * SiimTiFiearit. at laval. ** Significant at Fq ^ level. 159 Table $1. Analysis o l T mating type di-ff erences in egg albumen quality scores b & t#ne Om-aqusjre uecnnique (1950-51). Saiupling Mating Percent period Score P u r e b r e d Crossbred lnerossbrea Total o£ total dep oeuiucr 1.0 7 5 a 55 201 27.92 1.5 8 2 76 65 243 33.75 2t0 5 o 63 69 190 26.39 2.5 3-7 21 21 59 3.19 3.0-5.o o 9 10 27 3.75 Total 2 U O 2UU 2U0 720 —— Cni-square 5 - 5 5 December 1.0 7 U 75 59 208 26.69 1.5 7 3 67 6o 220 30.55 2.0 5 0 39 Ul 130 16.05 2.5 2 6 29 3U 89 12.36 3.G-5.0 1 7 30 26 73 10. Ik Total 21*0 2iiO 260 72u —— Cni-square > > - 6 3 harch 1.0-1.5 2 0 19 16 63 a. 75 2.0 >>5 66 131 316 143.89 2.5 8 d 100 72 260 36.11 3.0-5.0 2 5 35 21 81 11.25 Total 2iiJ 21*0 2du 72o --- Chi-square 2 ^ . 29** .eve. Tabie 52* Sumiuary of vne egg quairty data by muuuer of wgoou" aixo “poor11 quarxty eggs laid by id strains* Sampling Period September December Two nontn Total hareu hating Strain Good Poor Total Good Poor ioual Good Pour To ui Good roor Tota; Purebred 0 26 k 30 20 10 30 ii6 xu 6u 16 i2 30 15 1? 11 3o 16 14 30 35 25 60 U 16 30 19 19 11 30 16 Hi 3d 35 25 60 17 13 30 k 2k 6 30 19 11 30 U3 17 6o 23 7 30 16 20 10 3o 19 11 30 39 21 6u 13 17 30 26 21 9 30 * 17 13 30 36 22 6o 20 10 30 Total 129 51 160 107 73 160 236 12ii 360 103 77 160 Crossbred 6 15 15 30 15 15 30 30 30 60 11 19 30 9 21 9 30 20 10 30 iil 19 60 16 12 30 17 15 i5 30 17 13 30 32 26 6o 7 23 30 3 22 6 30 20 10 30 ill 16 60 16 Hi 30 Hi 16 12 30 12 18 30 30 30 60 17 13 30 20 16 12 30 19 11 30 37 23 60 10 20 30 Total 109 71 160 103 77 160 212 1ii8 360 79 101 180 Incrossbred 5 20 10 30 13 17 30 33 27 60 14 16 30 13 21 9 30 15 15 30 36 2ii 60 17 13 30 27 Hi 16 30 17 13 30 31 29 60 18 12 30 2 19 11 30 21 9 30 iiO 20 60 17 13 30 10 21 9 30 19 11 30 iiO 20 60 21 9 30 26 16 12 30 15 15 30 33 27 60 21 9 30 Total 113 67 130 luo 60 180 213 lii7 360 108 72 160 Sample total 351 159 5ij0 310 230 560 661 619_1060______290 250 5UQ $ 161 Table 53. Analysis of variance of the egg quality data of 1950-51 by strain and mating type. Sampling Period Sept. and Dec March source of Variation P.P. Mean Square P.F. Mean Square Total 107? *2377 559 .2U?1 between mating types 2 .5100 2 1-3350** Strains within iaating type 15 *3533 15 .U?27* Sampling periods 1 1.5500* Interaction Mating x sampling period 2 . loOO Strain x sampling period 15 .2U60 Error loWi .23U2 522 -237? * Significant at j?(j£ level. ** Significant at l*vel. Table 58* Analysis of strain differences in egg albumen 162 quality scores by tne Cxii*•square tecnnique <1951-52). Strain bo. Sampling Period Septeuoer December Harch Score 1.0-1.5 2.0-5.6 1.0-1.5 2 . 0 - 5 . 0 1.0-1.5 2.0-5.0 Hating Purebred 33 11* 16 21 9 22 8 3U 11* 16 22 8 18 12 3 ? 29 1 2k 6 i a 16 ho 19 11 26 a 22 8 86 21 9 29 1 2a 6 1*6 26 a 23 7 23 7 1*9 23 7 25 5 25 5 56 26 h 23 7 25 5 37 20 10 20 10 17 13 1*7 23 7 19 11 i a 16 5 2 23 7 29 1 25 5 Hating total 239 92 261 69 229 101 Percent or total 72.1 27*9 79-1 20.9 6 9 .a 30.6 CM 3 Chi-square 37.2o** 22. 2 9 .15** Crossbred 35 21* 6 20 1 0 21 9 1*1 2o 1 0 2 0 1 0 1 8 1 2 1*2 1 2 16 13 17 12 1 8 36 17 13 2 0 10 9 2 1 1*3 2u 1 0 19 1 1 22 6 1*1* 25 5 2 1 9 2 1 9 Hating total 116 62 113 67 103 77 Percent of total 65*6 3U.1* 62.6 37*2 57*2 8 2 .6 Chi-square 16.70** 6.06 19.98** Incrossbred 30 19 1 1 16 12 15 15 31 13 17 1 8 12 2 0 1 0 32 12 1 8 19 1 1 6 28 36 12 18 2 1 9 12 18 1*5 17 13 22 6 18 12 5o 13 17 2a 6 19 1 1 51 15 15 30 0 1 6 18 51* 19 1 1 25 5 1 6 1 8 55 19 11 2 0 10 20 10 Hating total 139 131 197 73 182 128 Percent of total 51 *5 1*6.5 73.0 27.0 52.6 87*8 Chi-square 1 0 .1 6 2 0 .7 6 * * 21.58** Sample total 1*95 285 571 2u9 878 3 0 6 Percent of total 63.5 36.5 73.2 26.8 60.6 39*2 Chi-square 67*22** 6 2 .6 1 * * * 87.58** * Significant at Pq £ level. ** iign-iXicaiit at Pq ^ level. 163 Table 55* Analysis of mating type differences m egg albumen quality scores by tne Cni-square technique (ly5i-52>. Sampling hating Percent Period Score Purebred Crossbred Incrossbred Total of total September 1.0 27 15 7 k9 9.07 1.5 lu2 iui 6U 26 9 >3.52 2.0-5-'o 51 62 09 202 37.U1 Total 160 160 ido 5Uo -— Oni-square 26.10** December 1.0 Uo 22 U9 i n 20.55 1.5 103 91 6 1 261 52. oU 2.0 33 Uo 39 120 22.22 2.5—5.*-* U 19 3 26 5.16 Total l6o 160 idu 5Uu — Chi-square 29.66** march 1.0 27 11 lh 52 9*63 1.5 95 92 63 270 50.00 2.0 03 5* 61 163 30.16 2.5-5.o 15 16 22 55 10.16 Total 160 160 160 5UQ --- Chi-square la.22* ™ S ignifTcant at level. ** Significant at P q ^_ level. Table 56. Summary of tne 1951-52 efe6 quality data by numoer of “good" ana “poor" quality eg6s iaia by id strains. Sampling Period September December March Three Month Total Mating Strain Qood Poor Total flood Poor Total flood f W r Total Good Poor Total Purebred 39 29 1 30 21* 6 30 11* 16 30 67 23 90 1*6 21 9 30 29 1 30 21* 6 30 71* 16 90 1*9 23 7 30 25 5 30 25 5 30 73 17 90 37 20 10 30 20 10 30 17 13 30 57 33 90 1*7 23 7 30 19 n 30 11* 16 30 56 31* 90 52 23 7 30 29 l 30 25 5 30 77 13 90 Total 139 1*1 180 11*6 31* 180 119 61 180 1*01* lo6 51*0 Crossbred 35 21* 6 30 20 10 30 21 9 30 65 25 90 1*1 20 10 30 2u 10 30 18 12 30 58 32 90 1*2 12 18 30 13 17 30 12 18 30 37 53 90 33 17 13 30 20 10 30 9 21 30 1*6 Iti* 90 1*3 20 10 30 19 11 3o 22 8 30 61 29 90 1*1* 25 5 30 21 9 30 21 9 30 67 23 90 Total 118 62 180 113 67 180 103 77 180 331* 206 51*o Incrossbred 30 19 11 30 18 12 30 15 15 30 52 38 90 36 12 18 30 21 9 30 12 18 30 1*5 1*5 90 5U 19 11 30 25 5 30 16 11* 30 6o 30 90 31 13 17 30 18 12 30 20 10 30 51 39 90 1*5 17 13 30 22 8 30 18 12 30 57 33 90 5o 13 17 30 21* 6 30 19 11 30 56 31* 90 Total 93 87 180 128 52 180 100 80 180 321 219 51*0 Sample total 350 190 51*0 337 153 51*0 322 2ib 51*0 1059 561 1620 16$ Table $7. Analysis of varxance of tne egg quality data of 1951-52 by straxn ana mating type (!)• Source of Variation U.F. Hean oquare Total 1619 .2265 between Hating types 2 3.6900** Strains Within mating type 15 .9173** Sampling periods 2 1 .9700** Interaction Hating type x sampling period k .6750* Strain x sampling period 30 .6667** Error 15 66 .2033 * Significant at level. ** Significant at F ^ level. (1) All tnree aanplxng periods are combined in this analysis. 1 6 6 Table 58. Analysis of strain differences in egg aJbuaen quality scores by tne Chi-square technique (1952-53)• Strain No. 5aunling Period September December March Score 1.0 1.5-5.0 l.O-i.5 2.0-5.0 1.0—1*5 2.0—5*0 Haling Purebred 50 15 15 12 16 21 9 53 17 13 9 21 16 11* 51* 13 17 15 15 17 13 56 15 15 11* 16 15 15 61 10 2u 13 17 11* 16 61* 13 17 11 19 11* 16 65 10 20 15 12 20 10 71 16 H* 7 23 12 16 56 17 13 17 13 16 12 65 17 13 13 17 21 9 69 1* 26 3 27 7 23 Mating total 11*7 163 132 196 175 155 Percent of total 1*1*. 6 55*1* 1*0.0 60.0 53.0 1*7.0 Chi-square 22.,03** 26.63** 23. 66** Crossbred 51 13 17 7 23 13 17 66 12 16 ID 20 12 16 67 23 7 16 H* 21 9 55 U 19 15 15 H* 16 62 11 19 12 16 17 13 76 9 21 12 18 10 20 Mating total 79 101 72 106 87 93 Percent of total 1*3.9 56.1 1*0.0 60.0 1*8.3 51.7 Chi-square 1 6 .,89** 7.1*9 10.31* Incrossbred 52 6 22 6 22 6 22 57 9 21 15 15 6 22 59 5 25 6 22 12 18 60 6 22 10 20 lit 16 63 15 15 11* 16 19 U 70 li 19 17 13 9 21 72 6 22 10 20 12 16 73 9 21 9 21 11 19 71* 7 23 U 19 18 12 75 d 22 17 13 19 11 Mating total 66 212 119 181 130 170 Percent of total 29.3 70.7 39.7 6 0 . 3 1*3.3 56.7 Chi-square 10. 20 15.73 22.58** Sample total 311* 1*96 323 1*67 392 1*18 Percent of total 36.6 61.2 39.9 6 0 . 1 1*8.1* 51.6 Chi-square 67.15** 1*9.67** 62.57** ** Significant at P ^ level. 167 Table 59. Analysis of mating type oifferences in egg albumen quality scores by the Cnx-square tecnnique (1952-53>* Sampling hating Percent Period Score: purebred Crossbred Incrosabred Total of total Sepmember 1.0 d? 79 57 225 31.67 1.5 65 71 37 223 31.30 2.0-5. 0 26 30 36 92 17.03 Total 130 130 130 53u — Cni-squnre 1 2 .2li* becamber 1.0 11 15 9 35 6.33 1.5 65 57 57 179 33.15 2.0 39 95 87 271 50.13 2.5-5. 0 15 13 27 55 10.13 Total ldo 160 130 5Uo — Chi-square 9.05 rtarcn 1.0 35 29 12 76 13.07 1.5 62 53 60 130 33.33 2.0 72 77 92 2 3 1 33*63 2.5-5. 0 11 16 16 33 7.96 Total 130 130 160 530 — Chi-square 1 5 .22* * significant at P q ^ Table 60. Summary oT the 1952-53 eg6 quality o*ta bj number of “good* and ‘Voor" quality eggs laid, by Id strains. Sampling Period. September December iiarch______Two Month Totaj* Mating Strain food Poor Total Good Poor Total Good fcoor Total Good Poor Total Purebred 51* 13 17 30 15 15 30 17 13 30 32 28 60 6l 10 20 30 13 17 30 li* 16 30 27 33 60 66 10 20 30 18 12 30 20 10 30 38 22 60 58 17 13 30 17 13 30 18 12 30 35 25 60 65 17 13 30 13 17 30 21 9 30 31* 26 60 69 li 26 30 3 27 30 7 23 30 10 50 60 Total 71 109 180 79 101 180 97 83 180 176 181* 360 Crossbred 51 13 17 30 7 23 30 13 17 30 20 1*0 •60 66 12 18 30 10 20 30 12 18 30 22 38 60 67 23 7 30 16 li* 30 21 9 30 37 23 60 55 11 19 30 15 15 30 li* 16 30 29 31 60 62 11 19 30 12 18 30 17 13 30 29 31 60 76 9 21 30 12 18 30 10 20 30 22 38 60 Total 79 101 180 72 106 180 87 93 180 159 201 360 Incrossbred 57 9 21 30 15 15 30 8 22 30 23 37 60 60 6 22 30 10 20 30 li* 16 30 21* 36 60 73 9 21 30 9 21 30 11 19 30 20 1*0 60 52 6 22 30 8 22 30 8 22 30 16 1*1* 60 59 5 25 30 8 22 30 12 18 30 20 1*0 60 72 8 22 30 10 20 30 12 18 30 22 38 60 Total kl 133 180 60 120 180 65 115 180 125 235 360 Sas^ L 197 31*3 51*o 211 329 51*o 2i*9 291 5i*o I460 620 1080 ecember and March samples are combined. 169 Table 61. Analysis of variance of the egg quality data of 1952-53 by strain arid mating type. Sampling Perib'dT Septsmoer Dec. and March Source of Variation D.7. Mean Square D.t. Mean Square Total 539 .2322 1079 •21*1x7 Between Mating types 2 i.5Uoo** 2 1.8700** Strains within mating type 15 •571x7** 15 .31*67** Sampling periods —— — — 1 1.3300* Interaction Mating type x sampling period -- 2 .1350 Strain x sampling period —— — 15 .1*61*7** Error 522 .21/3 loUU .2290 * oigQii«v ivvei* ** Significant at P qj_ level. 1 7 0 Ill* Discussion The frequency distribution of egg albumen scores presented in Table kS is typical of all of the distributions. The other distri butions were not given in order to save space. A striking feature of the data in this table is that all of the nine possible classes do not occur. None of the strains produced eggs of poor enough al bumen to be classified as 5*u. Thirty-five eggs were scored as 4*0 wniie only 20 were given a 3*5 rating. One possible explanation for this increase rather than decrease in number of eggs rated 4*0 is due to the breaking operation per se. Host of the eggs in the 4*0 class may have resulted from faulty breaking technique brought on by thick shells and/or resistant shell membranes. As a result of applying added pressure to break these eggs, the thick white was inadvertently cut or broken in many cases. The scores are all skewed or clustered to one end of the scale, i.e. that of higher quality. In the March and September sampling periods, the same type of skewness is apparent, although in the former, the distribution is centered farther down the scale. Van Vlagenen and Hall (iy^6) observed essentially the same form of distribution curve. The model class in their data for eggs laid in January and February was 1.5 to 2.U. Only three eggs out of 5b received a score of 2*5 or more, tahile the Van fcagenen-fciilgus scoring system provides a rapid method of distinguishing differences between hens and strains, the technique is .defective due to the face that so many eggs fall in the higher quality classifications. The technique does not provide a fine enough scale to permit one to 171 investigate fully the natural variation which must be present in this variable. However, for a rapid, comparative test it probably measures albumen quality as good as many of the other tecnniques. The mean albumen scores for the purebreds, crossbreds and incross breds are given in Table 1*6. It is evident from these data tnat albu men quality as measured by the Van fcagenen-Viilgus technique decreases from September to March. The decrease in quality is most pronounced for the 1950-51 data. Tne average scores for toe September, December and March sampling periods are 1.6U, 1*77 and 2.25, respectively. In 1952-53, the eggs in the December sampling period possessed the poor est quality. There is no apparent reason why this should have occurred. At least four factors could exert an influence upon egg quality and bring about a decrease in albumen score from September through March. These are errors introduced by the grader, seasonal factors, egg sixe and age of the hen and/or sustained egg production, hrrors due to grader are prone to occur because of the subjective nature of the scoring technique. In each breaking period, the eggs were scored by one grader, however, this same grader may or may not have scored the succeeding samples. This factor introduces a source of variation over which we had no control in this experiment. Lorens and New Ion (19l*l*> conducted a field survey of the quality of eggs laid from March to July, iney observed that the albumen nexght of neat fresh eggs suffered a seasonal loss of about 0.5 mm and that the nest and "ranch fresn" (broken within 2k hours of laying) egg variances were twice as large in March as in June. They concluded 172 that initial egg quality is not only lower in the early part of the summer but also more uniform. If the same proportion of the variance should be Heritable, Harca would be a better tiiue to measure egg qual ity than June, especially from a breeder's standpoint. Hunter, Van wagenen and Hall (1936) reported a seasonal trend in the score of tne condition of tne firm albumen in fresh eggs. This decline first be came apparent in March or April and continued throughout the summer. The albumen index of newly laid eggs produced by White leghorns shov ed a downward trend from October to July (Wilhelm and Heiman, 1936). Ringrose and Morgan (1939) reported a decline in albumen height from January to June. Age of the hen producing the eggs m^ght nave an influence on the albumen quality of the egg. Lorenz and Kewlon (19iiU) compared the egg& produced by pullets and hens and observed that the pullets laid e&gs of superior quality. &nox and Godfrey (1936) after studying eggs produced by Hi yearling and 20 hnode Island Red hens concluded that age is probably not the major reason for the decrease in albumen quality which occurs with increasing age. While it nas been observed tnat egg weignt has no influence upon the percent of firm albumen (Xnox and Godfrey, 193U* Lorenz and Almquist, 1936$ Knox and Godfrey, 1930$ and others;, the natural increase in egg size during the first laying year has an influence upon the apparent condition of tne thick albumen. Larger eggs tend to spread out more and thus give the appearance of poorer quality. The eggs used in this study were not weighed prior to breaking, 173 therefore* no indication of now much influence egg size n&s upon the observed condition of the fxra albumen can be ascertained* The question of whether sustained hx&h egg production adversely influences albumen quality xs not decided. Jinox and Godfrey (193d) reported a non-signxfleant correlation between number of eggs and percent of tnxck albumen and a non-signxficant muitxpie correlatxon between egg weight* number of eggs and percent of tnxck white. Brant* Otte a d Chin (1933) reported that nigh-producing biros in the hhode Island Egg laying Contest tended to produce eggs of lower quality than low producers, however* this tendency was not apparent in data col lected at the Georgia Egg Laying Contest* In view of previous inves tigations* most of the decline in albumen quality can possibly be attributed to seasonal factors and sustained high egg production. The pure strain? in the 191*9-50 test produced eggs of poorer average quality than those laid by the strain crosses and crossbreds during tne July and March sampling periods* From 193d tnrougn 1933* tne pure strains laid eggs of higher average quality tnan the cross breds with one exception (tne December sampling period of 1 952~33). The eggs laid by the purebreds possessed better average albumen qual ity tnan those laid by the incrossbreds* except in March of 193^-51 when the average scores for these two groups were essentially the same* Tne crossbred strains on tne average* produced eggs of higher albumen quality than the incrossbreds although this trend is not as pronounced as that between the purebreds or crossbreds or between the purebreds and incrossbreds. Mueller (1952) observed that eggs laid 17U in June by commercial inbred-hybnds possessed somewnat more firm albumen tnan those produced by crossbred stock* Braut, utte ana C h m (l?5l) round little or no difference in albumen quality between pure breds and crossbreds. Significant values of chi-square were obtained for tne differ ences between strains with respect to albumen quality scores m each of the three sampling periods of l?U9->o (Table ki)* lne cni-square value for the July sample is significant at the Pq£ level, wnile those for the December and March samples are highly significant* This indicates that there are wide differences between tne strains relative to albumen quality* The analysis of variance of the data from 12 of these 15 strains supports this statement (lable l*y>* The mean squares for strains within mating type are significant at tne level in each of the three sampling periods. The relative sise of tnese mean square values shows a marked increase from tne July sa^plm*, periou u> tne iiarcn sampling period, while tne witnm variance remained es sentially the same. The pure strains, strain crosses and crossbreds exnib it Btarkeo co us latency in the number of "^oba** and “poor11 quality eggs (Table ho). Tne tuean square value for mating types does not exceed the within variance in two of the three sampling periods. In tne third SAMpling period, March, tne F ratio is not significant. From a consideration of the mating type mean squares, it is apparent that there is no evidence of hybrid vigor for albumen quality* The pure strains, strain crosses and crossbreds are producing approximately the same number of "good" and "poor* quality egg s. if there were ary 175 hybrid vigor for albumen quality the cross Dr eds, on a theoretical basis at least* should produce eggs of iugner quality than the pure breds and possibly tne strain crosses. However* this is not the case. In the data of 1950-51* the differences between the 26 strains in each sampling period are highly significant (iaole pu)* Only in tne oepteiuber sample are tne differences between the pure strains significant* while in all three sampling periods the crossbreds dif fered significantly with respect to albumen quality score. None of the cni-square values for the incrossbred strains exceed the Bq ^ level. * The various crossbred strains are markedly inconsistent in their abil ity to produce eggs of uniform quality. It is of interest to note that the incrossbred and crossbred strains produced* witn one excep tion* a smaller percent of eggs scoring l*u or 1.5 tnan the pure strains. The exception was in the March sailing period wnen tne in crossbreds produced 61.J percent as contrasted wibn 56.0 percent for the purebreds. Tnere is no pronounced trend between the crossbreds and incrossbreds witn respect to the percent of eggs scoring 1.0 or 1.5* in tne September sampling period* tne crossoreds possessed a slight advantage wnile in March the opposite is true. From these data it is evident that the incrossbred strains produced eggs of more uniform but poorer quality than the purebred strains. The analysis of mating type differences in egg albumen quality scores for 1950-51 by the chi-square technique indicates that only in March are these differences of such magnitude to be judg<. signif icant (Table 51)• The erratic distribution of the eggs laid by the crossbred and incrossbred groups probably accounts for this result* 1 7 6 The analysis of variance of the number of "good" and “poor" quality eggs laid by lb of the 28 strains is presented in Table 5J* Tne September and December samples were analyzed in one analysis, while the March sample was treated separately. From the combined analysis, it is apparent that the differences between mating types and between strains within mating type are not significant. Like wise, the mating type x sampling period and strain x sampling period interactioiiS are not significant. The significant sampling period mean square may be due in part to the scorer* In the March analysis the between strains within mating type and the mating type mean squares are significant at the Pq £ and Pq ^ levels, respectively* The cross bred strains produced many more “poor" quality eggs than either the purebred or mcrossbred strains (Table 52). Tnis probably accounts for the significance of the mating type and strains within mating type variances* The 26 strains in the 1951*52 test differed signxficantly with respect to albumen quality scores in eacn of the tnree sampling periods (Table 5k)* The chi-square values in eacn case exceed the Pqj_ level of significance. The chi-square values obtained from the analysis of differences between the pure strains are greater tnan the Pq^ or P ^ levels of significance* The eggs laid by the incrossbred strains in December and March and by the crossbred strains in September and March departed significantly from the hypothesis of no difference between strains within mating type relative to albumen quality* Again as in 1950-51, the pure strains laid a nigner percent of eggs scoring 1.0 or 1.5 than the crossbred or incrossbred strains. There is little 177 consistent difference oetween the crossoreds and mcrossbreds rela tive to the percent of eg6s scoring 1.0 or 1*5 (Table 5U)> Tne data presented in Table 55 indicate that tne pure strains* crossbreds and incrossbreds produced eggs within each sampling period differing significantly in albumen quality. The analysis of variance of the data from 15 of these 26 strains is given in Table 57* The three sampling periods are combined in this single analysis. All of the sources of variation listed in the table are Significant. Tne significant mating x sampling period interaction implies that the pure strains* crossbreds or incrossoreds did not produce eggs of the same quality throughout the year. The total number of "good** quality eggs laid by tne purebred strains increased from September to December* wnile tne corresponding figures for the incrossbreos showed a decided increase (Table 56). Tne strain x sampling period interaction indicates that the strains did not perform similarly from one sampling period to the next. The significant mating type and strains within mating type mean squares support the observation obtained from the chi-square technique. In tne 1952-^5 test as in the three preceding years, the dif ferences between strains within sampling periods are significant (Table 56). Likewise* the pure strains differ significantly among themselves in each of the three sampling periods* while the cross bred and inorossbred strains differed significantly in the September and harch sampling periods* respectively. The purebred strains laid a higher percent of eggs scoring 1.0 or 1*5 than the crossbred or incrossbred strains* although the superiority of the purebreds is 1 7 8 not as distinct aa In preceding years. The crossbreds consistently produced a higher percentage of eggs grading 1.0 or 1.5 than the in- crossbred strains. This advantage was not noted in previous years. An examination of Table 59 reveals that the three mating types dif fered signif icantly with respect to albumen quality scores in two of tne tnree sampling periods (September aiid narchj. The mean square values for mating types and for strains within mating type are significantly larger tnan the within mean square (Table 61). The strain x sampling period interaction calculated in the combined analysis is highly significant. IV• Summary Results of the albumen quality studies warrant the following conclusions t 1. There is apparently no hybrid vigor for albumen quality as measured by the Van feagenen-taiigus score. Tne incrossbreda almost witnout exception produce eggs of poorer quality than the purebreds. The crossbreds* in general* lay eggs of slightly lower quality than the purebreds but super ior, on the average* to the incrossbreds. 2. Albumen quality varies more in tne crossbreds than in the incrossbreds. The crossbreds are slightly less variable with respect to albumen quality than the purebred strains. Tne incrossbreds produce eggs that are more uniform in albumen qual ity than either the purebred or crossbred groups. 3* The variation in albumen quality scores between strains within a sampling period is very high* bexig significant In every case. 179 ii. The variation between mating types within a sampling period, is greater than can be explained on the oasis of random fluctuations. 5* The Cni-Square and analysis of Variance Techniques give essentially the same information. Since the analysis of vari ance procedure is muco simpler to compute and provides estimates of certain interactions* it is nighiy recommended. 6. The significant strum x sampling period interactions imply that the strams do not maintain albumen quality in a iiioe manner from one sampling period to the next. A similar state ment based on the significant mating type x sampling period inter action can be made. ItiO BIBLIOURAPhY Anderson, li* L. and T. A* Bancroft, J-952. Statistxcal Theory in Research. McGraw-Hill Book Co., Inc., New York. Bell, A. R. and J. T. Baldinx, 1951* Genetic influence in varia tion in growth rate of chxcks. f o u l . Sci. iu*906. Bice, C. M. ana B. A. Tower, 1919* Crossbreedxiig poultry for meat production, including a feeding test of taro waste and poi. Hawaii Agr. Rapt. Bta. Bull, dl. Bird, S. and H. S. Gutteridge, 195U* Significance aetermxnatxon- numbers. Sex an. Agr. IR j lu-lj. Blow, 1m . i* and A. 1m . Glazener, 1955* The effect of inbreedxng on some productxon characters in poultry. Foul. sex. 12* 696-7G1. Bo3 tian, C. h. and R. S. Dearstyne, 191*2. Crossbred broilers and layers compared wxth related purebreds. Foul. Scl. 21s U65. Brant, A. W., A. k. Utte and G. Chin, 195J. A survey of egg quality at two Egg-Laying tests. U. S. D. A. Tech. Bull. 1066. **. Shrader, 1952. How to measure egg 1 . q. (Interior quality). 0. S. B. A. Brody, S., 1927* Growth arid development, ho. Agr. Expt. Sta. Res. Bull. 97. “ --- Brody, S., 191*5* Bioenergetics and Growth. Reinhold Fublxshxng Co., New York. Brunson, C. C. and G. F. Godfrey, 1951* Performance of Rhode Island Reds, Barred Plymouth Rocks, khite Leghorns and crosses involv ing these breeds. Foul. Sci. >0j 9Gb. Castle, 1m . E. 1916. Genetics and bugenics. Harvard Univ. Press, Cambridge, Mass. Cole, L. J. and J. U. Halpin, 1916. Preliminary report of an experx- ment on close inbreeding in fowls. Jour. Am. Assn. Inst, and Invest. In Poultry husb. Ji 1-5. Coleman, T. H», 1955* Heterosxs for growth and a method for inten sifying thxs phenomenon in the domestic fowl, ph B. disserta tion, The Ohio State Univ. and R. G. Jaap, 1951*. The topcross progeny test of sires use a for inbreedxng in poultry. Foul. Sci. (in print). 151 Comstock, R. E., H. F. Robinson and F. R. Harvey*, 19li9* A. breeding procedure designed to make maximum use of both general and specific comb in-LnB ability. Agronomy Journal, l*lt 3 6 0 -3 6 7 . Dickerson, G. k., (4. h. kinder, «. F. Rrueger and ri. L. kempster, 1950. Heterosis from crossbreeding and from outbreeding* Foul. Sci. 29i 756. ______, J* L. Lusn and C. C* Culbertson, 191*6. Hybrid vigor in single crosses between inbred lines of Poland Cnina Swine* J* An. Sci* 5* 16-2U* Dobzhansky, I., 191*7* Genetics of natural populations* XIV* A re sponse of certain gene arrangements in the third chromosome of israssrDrosphila pseudoobscura------to natural selection* ---- Genetics 321 and N. Levene, 191*3. Genetics of natural populations. XVII* Froof of operation of natural selection in wild popula tions of Drosophila pseudoobscura» Genetics 33: 537-51*7* Dryden, J., 1915* Inbreeding, its effect on vigor and egg laying. Amer. Assoc. Inst* and Invest, in Foul, husb. It 19-21*. Dudley, F. J., 191*1*. Results of crossing the Knode Island Red and Iwhite Leghorn breeds of poultry. Jour. Agr. Sci* 3 i*t 76-51. ______and K. S. Fease, 191*5. Experiments in top-crossing poultry. Froc. 5th World's Foultry Congress, Copenhagen, Official Report 1. ZB5-290. Duiaon, A. G., 1930. The effects of inbreeding on hatchability. Froc. Fourth korld's Foultry Congress * 1-5* Dunkerly, J. s., 193C. The effect of inbreeding. Froc. Fourtn korld's Foultry Cong. 1*6-72. Dunn, L. C., 1923* Experiments on close inbreeding in fowls. A preliminary report. Storrs Agr. Exp. Sta. hull, lilt 135-172. , 1925. The effect of inbreeding and crossbreeding upon fowls. Froc. Fifth International Genetics Congress. Vol. 2: 609-617*------ Duzgunes, u*, 1950. The effect of inbreeding on reproductive fitness of 5. C. U. Leghorns. Foul. Sci. 291 227-235* East, E. M. and D. F. Jones, 1919* Inbreeding and Outbreeding. J. R. Lippincott Co., Fhiladelphia. 182 Eaton, 0* N», 19iil. Crosses between inbred strains of rnj.ce. Jour. Heredity 32t 393-395» , k. &• Neville and G. £. Dickerson, 1930. General and spec if1 ic combining abilities in mouse crosses. Jour. Animal Sci. 9* 636-637. Essary, E. U., G. J. mountney ana 0* E. Goff, lySb. Conformation and performance in standard bred and crossbred broilers. Poul. Sci. 2 y: 757* ______, 1931. Conformation and performance in standardbrea and crossbred broilers. Poul. Sci. 30: 552-537. Ghostley, F. and A. W. Noraskog, 1951* Hybrid vigor in strain cross ing and breed crossing. Poul. Sci. 30: 9lU> Glazener, E. A. and k. JL. Blow, 1950. Broiler performance of inbred cross combinations. Poul. Sci. 29: 759* , 1 9 5 1 . Topcross testing for broiler production. Poul. Sci. 30t 870-87U. ______9 C. H. Bostian and K. S. Bearstyne, 1 9 5 1 . Effect of inbreeding on oroiler weights and feathering in the fowl. Poul. Sci. 30: 106-112. , n. E. Comstock, k. L.blow, R. S. bears tyne and C. H. Bostian, 1952.crossbreeaing for egg production* Poul. Sci. 31s 1078-1003* Goodaie, n. D., lyly. Practical results from studies on egg pro duction. Thirty-Second Annual Report. hass. Agr. Expt. Sta. Buil. lyil 2B-iZ5I^ , 1927. Six consecutive generations of orother to sister matings in knxte Juegnorns. A preliminary report on studies m inbreeding in poultry. Poul. Sci. 61 27U-276* Gove, H. S., 1952. Recent information on the relative effect of environment and neredlty on egg production. Poul. Sci. 31: 918-919. , A. S. Johnson and k. J. kakely, 1953. The effect of location on the heritability of egg production of two S. C. White Leghorn strains. Poul. Sci. 32 : 901. Hall, G. 0., 1939* Breed variations in egg characteristics. Poul. Sci. 16: 262-287. ---- 183 Harris* J. 1., 1926. The monthly egg record of birds whxch dxe dur- xng the first laying year. foul, Sci. 6 s 1-8. * 1927* Further studies on the monthly egg record of birds wnxch dxe durxng the fxrst laying year, foul. Hex. 6 t 213-221*. Haugn, R. it.* 1937* The Haugh unxt for measuring eg6 qualxty. U* S. Egg and foul. Mag. i*3 ; 552-555* ~ Hayes, n. K. and E* m. East, 1911. improvement in com. Conn. Agr. Expt. Sta. Bull. 166. Hays* F. A.* 1923* Inoreedxng the Rnode island Red fowl with special reference to wxnter egg production. American Naturalist. 56: U3-59- * 1929* Inbreeding in relation to egg production. Mass. Agr. Expt. Sta. Bull. 256* 256-3U2. * 1931*. Effect of inbreeding on fecundity in Rhode island " Reds. Mass. Agr. Exp. sta. Bull. 312. * 1935* frogeny of inbred and non-inbred Rhode Island Red males. foul. Sci. li** 122-125- Hazel* L. N*> A. L. Hus son and J. L. Lush* 191*8* Comparisons of in- bred Boland China* Lanurace and purebred boars on iowa farms. Jour. Animal sci. 7* 511-313* Henderson* E. R.* 191*9* Inheritance of meat type and wexgnt of Dark Cornish* Rhite Leghorn and reciprocal crossbred chickens* Michigan Agr. mxp. Sta. quart. Bull. 321 1*6-51** Hetfter* H* 0>* 0. 0. Hankins and J. h. Eelier* 1950. Performance of crosses between six inbred lines of swxne. Jour. Animal Sci. 9* 639. Holst* R. F. ana H. J. Almquist* 1931a. Distribution of solxa matter in thick and thin egg white. Hilgardia 6 : 1*5 -i*b. * 1931b. Measurement of deterioration ~ in tne stored hen15 egg. Hilgardia 6 * 1*9-60. Horlacher* R. R. and R. M. Smith* 1936. freliminary report of cross breeding for broiler production. Ark. Agr. Exp. Sta. buJJL. 351*. and R. H. Riley, 19l*l« Crossbreed- in£ ^or broiler production* Ark. Agr. Exp. Sta. Bull. 1*11. 184 hunter, J. A., A* Van Wagenen ana G. u. hall, 1936* Seasonal cnanges In interior egg quality of Single Comb White Leghorn hens. Foul. 5c i. 151 115- H d . butt, F. b., 193d. The geneticist's objectives xn poultry improvement. Am. Nat. 72: 26d-2dU- _____ , 1949- Genetics of tne Fowi. McGraw-Hill book Co., Inc. taew York. ______and h. K. Cole, 1952. beterosis in an inter-strain cross of WWite Leghorns. Foul. Sci. 31: 365-374. Jeffrey, F. F., 1939* Crossbreedxng for egg production, hints to Foultrymen: N.J. A g r . hxp. Sta. 26: 5* Jenkins, h. T., 1929. Correlation studies with inbred and crossbred straxns of maize. Journ. Agr. Kes. 39: 677-721. , 1935* The effect of xnbreedxng arid selection withxn inbred lines of maize upon the nybirds made after successive generations of selfxng. Iowa State Coll. J. Sex. 9: 42y-50. , 1937. Corn improvement. U* S. D. A. Yearbook. 455- ^ 2 2 ------ ______and A. h. b runs on, 1932. Metnods of testing inbred lines of maize in crossbred coiabxnatxons. Jour. Amer. Soc. Agron. 24* >23-530. Jones, IK F., 1922. Tne productiveness of single and double first- generation com nybxrds. Jour. Amer. Soc. Agron. 14: 241-252. Jull, H. A., 1929. Stuoius in natchabxlxty. 11. batcnabilxty xn re lation to the consanguinity of the breeding stock. Fouit. ocx. 219-229. _ , 1933* The effects on various oaeructof cx^se inbreed- ing and intercrossing closely inbred lines of White Leghorns. Jour, heredity 24: 93-lbl. , 1952. Poultry breeding. John Wiley and Sons, New York* Keller, K. h., ly49* A comparison involving the number of, and re lationship between, testers in evaluating inbred lines of maize. Agron. Jour. 41: 323-331* Kenney, J. F., 1949* Mathematics of Statistics. IK Van Nostrana Co., Inc., New York. ias King, R. 0., 1916. Studies on inbreeding. 1. Tde effects of in- breeding on tne growtn and varxaoilxty in bo ay weignt of tne albino rat. J. mxpt. Looi. 26: 1-5U. , 1919. Studies on inbreeding. 11. Jour, of Rxpt. Lool. 551 136-175* ------ King, S. C., 1951* An interaction effect of crossoreeding on egg production. Foul. Sci. 30: 92u. ______. 1932. nfeg quality studies at the Wew fork ganoom Sample Test. * Foul. Sex. 31: 96a. and J. H. Bruckner, 1952. A compare live ajulysxs of pure- bred and crossbred poultry. Foul. Sci. 31: 1Q30-1o 36. Knox, C. *., 1939* Crossbreeding in tne aoir.estic fowl. Froc. oeventh World's Foultry Cong. 56-61. , 1966. Tne development ana use of chicken inbreds. Foul. £ci‘. 251 262-272. ______, 195a. Some results of poultry research. U. S. 0. A. Mimeo. 137. — ______and a . B. Godfrey, I93h. Variability of thick aioumen in fresh laid eggs. Foul. Sex. U : 16-22. , 1936. Factors influencing tne percent- age of thick albumen oT nens' eggs* Foul. Sci. 17: 159-162. , 196a* Five years of breeding for high and low percentage of thick albumen in the eggs of Rhode Island Reds. Foul. Sci. 19: 291-296* , C. 0. Gordon, N. R. hehrhof, 1969* Performance of nnode Island Reds ana Light Sussex as compared with that of tneir F and tnree-way crossbreds. Foul. Sci. 2d: 615-619. and H. In. Olsen, 1936. A test of crossbred chickens, Single Comb khite Leghorns and Rhode Island Reds. Foul. Sci. 17: 193-199. , J. P. guinn and A. B. Godfrey, 1963* Comparison of Rhode Island Reds, *hite kyandottes, Light Sussex, and crosses among them to produce Fi, and three-way cross progeny. Foul. Sci. 22: 53-67. ---- Lindstrom, £. k., 1931. Prepotency of inbred sires on cofflmercial varieties of maize. Jour. Amer. Soc. Agron. 23: 652-661* 1 8 6 Lindstrom, £. to., lyip-* Analysis of m o d e m maize brooding principles and methods. Proc. Seventh International Genetics Gong, 191-196. Lonnquist, J. n., 1951* Kecurrent selection as a means of modifying coiabining anility in com. Agron. Jour. 83: 311-313* Lorenz, P. to. ana h. J. Almqui^t, 1936. Seasonal variation in egg quality. Poul. Sci. 151 18-18. ______and to. to. Newlon, 1988* A fiela survey of ranch egg qualicy". Poul. Sci. 23* 818-830. i _ _ _ and L. to. Taylor, 1980. Tne inheritance of albumen quality ’characteristic of chicken eggs. J. Agr. ties. 61*293-301. ______H. J. Almquist, 193u. Firmness of albumen as an inherited characteristic. Poul. Sci. 13* 18-17* Lush, J. L., to. P. Lamoreux and L. N. nazel, 19U8. The heritability of resistance to death in the fowl. poul. Sci. 27* 375*388. Massey, J. H. and E. hoffmann,lyUb. Grosses between New dampshires and hhode Island deds for broiler production. Poul. Sci. 27* 673* haw, A. J. G., 19Ul. Crosses oetween inbred lines of tne domestic fowl. Poul. Sci. 20* 865* ______, 1982. Crosses between inbred lines of domestic fowl. PoulT Sci. 21* 588-553. ______, 1989* Performance of crosses of certain inbred lines. Poul. Sci. 28* 899-503. , 1952. Uniformity of Type in broilers. World's Poul. Sci. Jour. 8* 281-285. Haw, to. A., 1933* Heat production in poultry* U. S. ggg and Poul. Hag. 33* I0 -8 6 . *” Hills, F. C., 1980. Statistical Methods Applied to Economics and business, rienry Holt and Co., New fork. Hoore, C. n. and J. G. barren, 1951* Influence of tne coefficient of inbreedm& on the variability of growtn of topcross chicks. Poul. Sci. 301 928* Mueiler, G. 1)«, 1950. A comparison of commercial inbreu-hybrids and first generation crossbreds. Poul. Sci. 29* 773* Huellar, G. D*, 1952. A cowipanson of commercial inbred-hybrid chickens and first generation crossbreds from non-inbred stock. Poul. Sci. 31i 166-170. Munro, S. S., 193b. Effect of neredity on interior egg quality and shell composition. Poul. Sci. 17s 17-27. Nordskog, A. W. and 0. Cot ter ill, 1953*Breeding for egg quality. 2. Sampling hens for interior quality. Poul. Sci. 32 s Iu5l-1G54. O'Neil, J. B. and W. J. Bae, 1946* evidence of heterosis in the body weight of day-ola crossbred chicks. Poul. Sci. 27: 120-122. Pearl, B. and P. a . Surface, 191d. Studies on hybrid poultry. He. Agr. Expt. Sta. Bull. 179* Pease, H . , 1946* Inoreedihg in poultry livestock improvement. Proc. Eighth World's Poul. Cong. 33-42. Bingrose, B. C. ana C. L. Horgan, 1939* A studyof the effect of green feed upon interior egg quality. Poul. Sci. lbs 125-126. Bobers ton, A., 1949* Inbreeding experiments in Dairy Cattle. Animal Breeding Abs. 17s 1-6. Schroeder, C. H. and H. S. Lawrence, 1932. The number of chicks required to demonstrate the significance of growth differences. Poul. Sci. 11: 20d-21o. Scott, H. h., l9hl. Egg quality studies with the Storrs Contest hens. Poul. Sci. 20: 472. Shoffner, B. N., l9Uoa. The variation within an inbred line of Single Comb White Leghorns. Poul. Sci. 27s 235*236. , 1943b. The reaction of the fowl to inbreeding. Poul Sci; 27s’' 446-452. --- Shull, G. B., 1911* The genotypes of tuaize. Amer. Mat. 45s 234?*252 Snedecor, G. W., 1946. Statistical hethods. Iowa State Coll. Press., Ames. Sprague, G. P. arid L. A. Tatum, 1942. General vs specific combining ability in single crosses of corn. J. Amer. Soc. Agron. 34* 923-932. " Stephenson, A. B. and A. W. Nordskog, 195b. Influence of inbreeding on egg production in the domestic fowl. Poul. Sci. 29: 7bl. 188 Stephenson, A* B., A. J. Wyatt and A. W. Nordskog, 1953. Influence of inbreeding on egg production in the domestic fowl. Foul. Sci. 32: 510-517. Thayer, h. ri., 19U5* Measuring eg6 quality. U. S. E*^ and Foul. Mag. 51: 388. ------ Van Wagenen, A. and 0. 0. hall, 1936. The inheritance of certain characters affecting egg quality. Foul. Sci. 15: U05-U10. and ri. S. Wjlgus, 1937- Variation in egg quality cnaracters of certain breeds, varieties and strains of chickens. J. Afar. hes. 5U: 787-777* ana h. S. Wilgus, 1935* Tbe determination and impor- tance o f the condition of the firs aioumen in the studies of egg- white quality. Jour. Agr. hes. 51: 1129-1138. Warren, i). 0., 1927* hybrid vigor in poultry. Foul. Sci. 7: 1-6. , 1930. Crossbred poultry. Ean. Agr. Expt. Sta. null. T$T. , 19^1* hesults of crossbreeding poultry. Foul. Sci. sxrr u r6 . — — , 19U2. The crossbreeding of poultry. han. Agr. Expt. Sta. frech. Bull. 52. Waters, N. F., 1951* Body weight of different inbred lines of chickens. Foul. Sci. 30: 615-62U. and W. V. Lambert, 1936. inbreeding in the White Leg- norn Yowl. la. Agr. Expt. Sta. hes. Bull. 202. Wilhelm, L. A., 1939* Egg quality. A literature review. IJ. s* Egg and Foul. Hag. U5: 565-573* ” and V. hemman, 1938. The seasonal changes in interior egg Quality of new laid eggs. Wasn. Agr. Expt. Sta. Teen. Bull. 356.------ Wilson, W. 0., 19U6. Egg production ana fertility in inbred chickens. Foul. Sci. 27: 719-726. Winter, L* M., W. S. Anderson, W. V. Lambert, B. L. Warwick ana h. C. McFhee, 1930. A survey of inbreeding research. Amer. Soc. An. Fro a. iih-131:. — 11J9 Winters, L* h*, K. E. Comstock, it* E* Hodgson, 0. M. Kiser, P. S. Jordan and J. L. Dailey, 191*3* Experiments witn inbreeding swine and sheep* Mann. Agr* Expt. Sta* Hull. 361** , D* L. Daxley, P. S. Jordan, 0. M* Kiser, h. E. Hodgson, J . N * Cummings and C* F. Sierk, 19l*d. Experiments With inbreed ing swine* Minn. Agr* Expt. Sta. Bull. 1*00. Wright, S*, 1922 a. The effects of inbreeding and crossbreding on guinea pigs. U. S. 0. A. Bull* 1090* , 1922 b. The effects of inbreeditig and crossbreeding on guinea pigs. U. S* D. A. Bull* 1121. , 1922 c. Coefficients of inbreeding and reiationsnip. Am. Mat. 56* 330-336. Wyatt, A* J*, 1953* Combining ability of inbred lines of Leghorns. Poul* Sci. 32: 1*00-1*05* AUTUBIOGKAPnY I, John Francis Crimes, was born on Ravenswood, West Virginia, March J t 1927. 1 received ny secondary school education in the high school at Ravenswood* fly undergraduate train mg was obtained at Iowa State College and West Virginia University* I received the degree of Bacnelor of Science in Agriculture from West Virginia Uni versity in 1950* My undergraduate training was interrupted for a seventeen month tour of duty in the United States Navy* From July, 1950 to June, 1951* I uas a graduate assistant in the Poultry Hus bandry Department at West Virginia University* I received the degree of Master of Science in June, 195l> from this university. In June, 1951; 1 received an appointment as Research Assistant in the Poultry Science Department at The Ohio State University. 1 9 0