Selection for Egg Production Within Crossbred Chickens1,2

AMPEOLIUM, OXYTHIAMINE AND PYRITHIAMINE

ministration. These results suggest that oxythiamine may be less potent when given subcutaneously than when given in the diet, whereas pyrithiamine may be more potent by the subcutaneous route than by the dietary route of administration. SUMMARY

A procedure was described for determining antithiamine activities of thiamine antagonists using a thiamine-deficient, purified-type diet in 9-day growth test with chicks. The "antithiamine index" (mg. antagonist calculated to negate the growth activity of 1.0 mg. thiamine nitrate) for dietary administration was estimated to be 503 ± 14 (avg. ± S.E.) for amprolium, 79 ± 5 for oxythiamine and 14 ± 1 for pyrithiamine.

925

REFERENCES Fox, M. R. S., and G. M. Briggs, 1960. Salt mixtures for purified-type diets. III. An improved salt mixture for chicks. J. Nutrition, 72: 243-250. Naber, E. C , W. W. Cravens, C. A. Baumann and H. R. Bird, 1954. The effect of thiamine analogs on embryonic development and growth of the chick. J. Nutrition, 54: 579-591. Ott, W. H., W. R. Cobb, A. C. Cuckler, D. Polin and H. C. Stoerk, 1962. Amprolium 7. Biological studies in poultry. Proc. Xllth World's Poultry Congress, Sydney, Australia, p. 293-296. Robenalt, R. C , 1960. The thiamine requirement of young turkey poults. Poultry Sci. 39: 354360. Rogers, E. F., 1962. Thiamine antagonists. Annals New York Acad. Sci. 98: 412-429. Waibel, P. E., H. R. Bird and C. A. Baumann, 1954. Effects of salts on the instability of thiamine in purified chick diets. J. Nutrition, 52: 273-283.

Selection for Egg Production Within Crossbred Chickens1'2 A. B. STEPHENSON, Q. B. KINDER AND E. M. FUNK Department of Poultry Husbandry, College of Agriculture, University of Missouri, Columbia (Received for publication Tune 3, 1960)

C

ROSSES of various kinds are used extensively for the production of chickens. It has been generally assumed that crossbred females are undesirable for breeders to produce a terminal generation for maximum egg production. Published data regarding the breeding value of such 1

Contribution from the Missouri Agricultural Experiment Station, Journal Series No. 2169. Approved by Director. 2 Portions of this study were conducted as part of a North Central Regional Project (NC-47); a cooperative study involving agricultural experiment stations in the North Central Region and supported in part by regional funds of the United States Department of Agriculture.

terminal generation females are limited. Kusner (1957) found a cross between New Hampshire and White Russian gave better production than the backcross to the New Hampshires. Skaller (1954) found 2-way crosses laid 216 eggs and 3-way crosses 210 eggs in experiments extending over a five-year period. Waters (1938) and Maw (1942) suggest that if females from a cross were used as dams the males should be unrelated to the dams. Warren (1953) mentions the common practice of some swine breeders in using crossbreds for dams. He states 3-way

926

A. B. STEPHENSON, Q. B. KINDER AND E. M.

TABLE 1.—Lines used in producing 2-way cross

dams and 3-way cross of spring Sire XDam producing Female Parent H6XLa LIXHa R3XLs Code of Female Parent Cx Cz Cy Male Parent of 3-way Cross Progeny LI and L3 H6 and R3 Ll and L3

crosses are as good as 2-way crosses but no better. Laurent (1953) found vigor to be greater in the 3-way than in the 2-way crosses. He did not state the trait used to measure vigor. Kinder et al. (1960) used an index to measure general performance. A pure bred White Leghorn strain and commercial hybrids had indexes of 96 and 105 respectively while a cross between these groups had an intermediate value of 101. The primary objective of this experiment was to obtain data on the performance of 3-way cross progeny from 2-way cross dams which has been produced as a terminal generation. An additional objective was to estimate the relative value of the dam's family deviation and the dam's individual deviation within family, in predicting the productive rate of the 3-way cross progeny. SPECIAL TERMS 2-way cross: Females produced by recurrent selection. 3-way cross: The progeny of 2-way cross dams and non-related inbred males. Mean, rather than individual values are used in analysis of data. Rate 1: Percent egg production from housing at 22 weeks to about 37 weeks of age. Individual ranks 1 and 2: The classification assigned the 2 sisters within a family with the lowest and next to lowest individual rate 1 respectively. Individual ranks 3 and 4: The classification of the 2 sisters within a family with the next to highest and highest individual rate 1 respectively.

FUNK

Family ranks 1 and 2: The classification within each female population of the lowest and next to lowest families means respectively. Only families with 4 or more sisters were assigned ranks. Family ranks 3 and 4: The classification of the next to highest and highest family mean production rates respectively. Lower level: Family ranks 1 and 2 combined. Upper level: Family ranks 3 and 4 combined. Family deviation: The amount by which the rate of a family deviates from the mean of the dam's population. Individual deviation: The amount by which the rate of an individual bird deviates from its family mean. Correlated responses: Rate 2 is the percent egg production from first egg through November and rate 3 is production from December 1st to June 15th. Rate 4 and rate 5 are annual rates from housing and first egg respectively. EXPERIMENTAL

Three populations of pullets were available as crossbred dams. These females were the eighth generation of a recurrent selection breeding system. The breeds and strains involved in producing both the 2-way cross dams and the 3-way cross progeny are shown in Table 1. The first letter indicates the breed with L for Single Comb White Leghorns, H for New Hampshires, R for Rhode Island Reds, and C for 2-way crosses. The second character indicates a subdivision of breed. A number represents a specific inbred line used as a male parent in a cross. A letter following Ff, L or R indicates a non-inbred female line which had been selected for several generations on its combining ability with a specific inbred male line. The female parents were produced as a terminal generation by the reg-

SELECTION FOR EGG PRODUCTION

927

ular recurrent selection breeding program. These 2-way crosses, which were used as + (PL)ijkl+Rillm+(PR) dams, have been coded as Cx, Cy, and Cz. +1 ijklmn As shown in Table 1, the line Cx resulted +E from a cross of males from inbred New Where ijklmnT Hampshire line H6 and females from nonmean value of offspring. YiiMmnr inbred Leghorn line La. These Cx females M population mean. were mated to males from inbred lines LI Pi effect, common to the offspring and L3 to produce 3-way crossbred progeof the ith female line. ny. Comparisons were made between the Mij= effect common to the offspring 2-way cross dams and their 3-way cross of the specific combination of progeny. The same inbred lines were used the ith female and j'th male in both the 2 and 3-way crosses but in line. different combinations. A specific inbred Pijk — effect common to the offspring line was never used as both a sire and a grandsire. of the kth. pen of a replication. Liji= effect common to the offspring Within each group of 2-way cross dams, of the Mi family level within families were assigned ranks according to a breeding group. their mean rate of egg production from housing at 22 weeks of age until November {PL) ,7*1= effect common to the offspring 30, 1956, which was a period of about 15 of the specific combination of weeks. Egg production during this period the &th pen and /th level was the basis for breeder selection and is within a specific breeding called rate 1. The families with the lowest group. rate 1 were assigned a family rank of 1. R%jim = effect common to the offspring The family with the next to lowest rate 1 of the mth. family rank within was given a family rank of 2, and similarly each level. for ranks 3 and 4. Rank 5 was assigned to (PR) ijkim = effect common to the offspring the family with the fourth from highest of the mth specific combinarate, 6 to the third from highest, 7 to the tion of the &th pen and fth next to highest and a rank of 8 to the famfamily rank. ily with the highest rate 1. Families with Iijkimn = effect common to the offspring rates between rank 4 and 5 were not used. of the «th individual rank The individuals within a family were aswithin family rank. signed individual ranks in a manner simi.Ei/iUumr — variation among the mean of lar to that of families. The pullets with the offspring of the /th dams with lowest and next to lowest rate 1 within a the same individual rank. No family were given an individual rank of 1 direct estimate of this value is and 2, respectively. The next to highest available since there were no and highest rate birds were given individreplications of an individual ual ranks within family of 3 and 4, respecrank within a specific group. tively. The individual birds with a rate between that of individuals with ranks 2 and An estimate of the relative value of fam3 were not used. The relation among the ily and individual rates were obtained by variables considered may be expressed by expressing these values as independent the following model: deviations. The family deviation was from

928

A. B. STEPHENSON, Q. B. KINDER AND E. M.

the mean of the genetic group to which it belonged. Only a portion of the population was used as breeders and some of these did not produce female pullets which were housed, so the sum of these deviations was not zero. Individual rates of dams were expressed as deviations from the mean of their family, after omitting those dams without trapnest progeny. Thus the sum of the individual deviations within a family is zero for all families. The values used for family and individual rate deviations are independent. The family rate values are independent of the differences in production rates of their strain and annual environmental effects as they are in terms of deviations. Regression values were calculated by pooling data from all pens on an intra-sire line basis. Eight families were selected from each of the Cx, Cy, and Cz populations. There were 17, IS, and 42 families with 4 or more full sisters in Cx, Cy, and Cz, respectively, from which the 4 lowest and the 4 highest rate families were selected. None of the families had over S full sisters. The system of distributing females to individual breeding pens is illustrated in Table 2 for the Cx population. The Cy and Cz dams were distributed in a similar man-

FUNK

ner. There were 8 dams per pen and 2 replicated pens were mated to males from each of 2 inbred lines. This arrangement would give all 4 pens, within the same dams population the same average rate, if the differences in rates between each rank were the same. The mean of rank 1 and 4 would be the same as 2 and 3 and similarly ranks S and 8 would be equal to 6 and 7. However, the ranks do not represent a uniform change in rates and some of the pullets in the breeding pens did not produce any offspring. Because of these conditions, the means of the 4 pens of each population are not identical. Of the 96 females placed in breeding pens, 79 dams produced a total of 288 progeny with trapnest records. The 3-way crosses were hatched on March 9 and 23, 1957. Factors thought to be associated with rate 1 were also observed. The four correlated production rates were defined in the special term section. All rates were based on three day per week trapping until death or end of trap year. Age at first egg and egg weight in February were also analyzed. RESULTS The number of offspring from the dams of each family rank within each level of

f females to breeding pens on basis of family rank for part year egg production TABLE 2.—Aissignment o_ and individual rank within family LIXCx Replication 1 Family Level

L3XCx Replication 2

Replication 1

Replication 2

Family Rank

Individ. Rank Within F'amily

F'amily Rank

Individ. Rank Within Family

Family Rank

Individ. Rank Within Family

Family Rank

Individ. Rank Within Family

Lower level

1 1 4 4

1 4 2 3

1 1 4 4

2 3 1 4

2 2 3 3

2 3 1 4

2 2 3 3

1 4 2 3

Higher level

6 6 7 7

2 3 1 4

6 6 7 7

1 4 2 3

5 5 8 8

1 4 2 3

5 5 8 8

2 3 1 4

929

SELECTION FOR EGG PRODUCTION

TABLE 3.—Number of offspring and their deviation, when classified by their dam's family rank, from their mean egg production within specific breeding combinations for rates of production from i to November 30, 1057 Breeding Combina- tion

Low family

LI Cx L3 Cx

Dev. -17 0

LI Cz L3Cz

-

5 9

6 7

H6Cy R3Cy Total

-

7 5

19 8

Means

High family level

Low family level

No. 9 13

High family

High family

No. 4 4

Dev. 15 -1

No. 11 9

Dev. 18 -2

No. 13 18

56 56

37 44

0 1

15 11

8 1

7 20

-4 7

14 16

46 62

42 54

10 2

16 13

0 -2

15 11

-3 6

17 12

56 51

67 44 288

Dev. -14 3

63

62 -

Low family

Mean of Total breeding number combi- 3-way nations crosses

7

90

73 3

1

each genetic combination is shown in Table 3. This table also shows the mean rate 1 of each breeding combination. The progeny of the different family rank dams are shown as deviations from this mean. The means of these deviations are shown in the bottom row of Table 3. Each column from left to right of this table represents an increase of one family rank unit. The rate deviations of progenies from all dams with a family rank of 1 to 4 were —7, 1, 3 and 3 respectively, which indicates a positive regression.

54

3

The progeny means when classified by their dam's individual rank are shown in Table 4. As the dam's individual rank increases from 1 to 4, the mean deviations of their progeny have values of — 4, 0, 1 and 4 respectively. This indicates a positive relation between the individual rank of the dam and the production rate of their progeny. Family and Individual Deviations: The relative effectiveness of family and individual selection were estimated independently.

TABLE 4.—Number of offspring and their deviation when classified by their dam's individual egg production rank within its family rank, from their mean within specific breeding combinations of rate of production from housing to November 30, 1957 Family Level Within Low Family Rank

Combina-

Low Individ.

High Individ.

Ll Cx L3 Cx

Dev. 3 -16

No. 11 8

Dev. -3 5

LI Cz L3 Cz

-12 - 2

5 13

H6Cy R3 Cy

-

17 15

2 2

Total Means

4

Mean of Total breeding number combi- 3-way nations crosses

Low Individ.

High Individ.

No. 8 11

Dev. -1 6

No. 11 14

Dev. 0 5

No. 7 11

62 55

37 44

-2 -2

15 15

4 1

11 9

8 3

11 17

44 62

42 54

1 -1

20 10

18 12

1 4

12 7

57 51

67 44

-1 -5

79

69 -

Within High Family Rank

0

75 1

65 4

288 55

930

A. B. STEPHENSON, Q. B. KINDER AND E. M.

Family differences were measured by the deviation of the family mean from the mean of the genetic group to which the family belonged. Individual deviations were taken from their family mean. For example, the dams used from the Cy population had a mean rate of 67%. The highest rate family was 78% so this family's deviation was 11%. This family was composed of individuals whose rates were 84, 83, 76 and 69%. The values used for analysis were 11 % as a family deviation and 6, 5, — 2%, and — 9%, respectively as individual deviations. The individual dams with rates of 69% and 84% were in replicate pen 1 and thus had individual deviations of —9% and + 6 % respectively from their family mean. The 76% and 83% rate individuals were in replicate pen 2 and had individual deviations of —2% and 5%. There was some disproportionality as some dams had no progeny. Because of this disproportionality the intra-pen correlation between family and individual rate deviations was .01 rather than the expected zero for complete independence. Since the family and individual deviations are independent, their regression coefficients are the same in both linear and multiple regression. The multiple regression was:

FUNK

and individual regression coefficients were 10% and 14% respectively. This relation shows the probability of these coefficients being zero or negative is .03 and .05 for family and individual deviations respectively. It is not likely that the positive relation between dam and daughter in egg production was due to chance. The relative influences of family and individual selection can be expressed by converting this multiple regression into standard units which gives: y'=.22x\+.20x' where the primes indicate standard deviation units. These coefficients show family deviation to be slightly more efficient than individual deviations in predicting the progeny mean. The standard error of the difference between these coefficients is .14 units, and much larger than the actual difference of .02, so no significance is attached to the relative importance of family and individual deviations.

Rates of 2-Way and 3-Way Crosses: The mean production of all the 2-way cross dams was 60% and the mean of all their 3-way cross progeny, produced with males from lines untested for this specific cross, was only 54% as shown in Table 5. The breeding groups varied greatly in the y=.19xi+.24xz differences in production between the 2 where y is the expected deviation of the and 3-way crosses. The production of progprogeny mean, x1 and x2 are the family eny from Cx dams with both male lines and individual rate deviations of the dam and the Cz dams with L3 males was higher than their dam's rate. The L3 Cz combinarespectively. These regression coefficients were calcu- tion with a rate of 62% was the only lated on an intra-sire pen basis which gives 3-way cross to exceed the overall mean of heritability estimates of twice the regres- the 2-way cross dams, which was 60%. sion coefficients or 38% and 48% for fami- The Cz dams with LI males and Cy dams ly and individual deviations respectively. with both male lines produced progeny These estimates are for the mean of all the which had much lower production rates progeny from a dam. The number of pro- than their dams. The overall mean of the geny varied from 1 to 8 sisters per family. 3-way crosses was 6% below their dams. The standard errors of the family The 96 dams used in this experiment were

SELECTION FOR EGG PRODUCTION

931

selected from the 919 pullets with a rate of TABLE 5.—Number of birds and rate 1 egg production of 3-way crosses, all individuals in families of four or 63.5% as shown in Table 5. The next year more sisters in the 2-way cross dam's populations and the two control populations present both years the 288 three-way crosses of this experiment were housed with 752 regular recur1957 hatch 1956 hatch and 3-way and 2-way Offspring Breeding rent selection birds. At housing no distincCombination cross Cross dam offspring dams tion was made between 2 and 3-way cross2 and 3-way crosses % No. % No. es in distributing among 7 pens in 6 separL I Cx 56 37 51 ,0, 5 ate houses. Some of the pure strain S. C. 1Vi L3 Cx 56 44 51 5 White Leghorns were housed in pens adjaL I Cz 46 42 60 -14 oao iK L3 Cz 62 54 60 * 2 cent to the crossbreds. The fact that these H6 Cy 56 67 69 , , , 1 3 two rather large populations gained 0.5% R3 Cy 51 44 69 "J -18 and 1% respectively from 1956 to 1957 54 60 - 6 makes it unlikely that the 6% decline in Mean Regular Recurrent production from 2 to 3-way crosses would Selection Project 64 753 63| 919 J 61 517 1 be due to yearly effects or pen interactions. Pure Strain Leghorns 62 415 An indication of additive and non-additive sources of variation are shown in had production rates of 51, 69, and 60% Table 6. These data are based on the lines respectively as shown in Table 7. The mated in more than one combination and mean rate of the individual Cx dams with each combination was replicated in 2 pens. the offspring in the lower level was 39% The progeny of the two female lines and the mean of the individuals' dam in differed from the over-all mean rate by the higher level was 64% which gives a 2.5% and the two male lines by 4%. The range of 25%. The difference between the non-additive cell effects had deviations of means of the high and low rank dams in 6% from their expected values based on the Cy and Cz groups were 22% and 3 1 % the marginal means. For example, progeny respectively which show the populations from Cx would be expected to be 2.5% were rather uniform in the range between above overall mean and the progeny of LI the means of the low and high rank indiwould be expected to be 4% below general viduals, although the population means mean on the basis of additive effects. The ranged from 5 1 % to 69%. Table 7 also sum of these additive effects indicates the shows the mean of the offspring from each progeny of LI Cx would be 1.5% below group of dams. The progeny of the lower general mean or 53%. The observed value level dams had a mean rate of 5 1 % which was 59% which represents a non-additive was 4% above their dams, while the progedeviation of 6%. The non-additive devia- ny of the higher level dams had rates 17% tion of the other 3 groups have the same below their dam. This relation shows the absolute value. An analysis of variance of expected regression toward the population these 8 pen means showed interaction be- mean. However, the decline from the high tween lines to be significant at below the dams was greater than the increase from .005 probability level. This small group of the low dams. This comparison of dams data indicates specific combining ability is and offspring includes annual environmenmore important than the general combin- tal and any other general effects confounding ability among the lines used. ed with generations. Selection: The Cx, Cy , and Cz populations, from which the dams were selected,

The last row of Table 7 shows the deviation of each progeny group from the mean of all progeny. This comparison is within

932

A. B. STEPHENSON, Q. B. KINDER AND E. M.

FUNK

TABLE 6.—Production values, their deviation from the general mean and the expected deviation of cells based on marginal means of two male and 2 female lines in a diallele cross where each cell represents the mean of two replicated pens LI Observed Mean Value Cx Cy Mean

59 42 50.5

Deviation 4.5 -12.5 - 4.0

L3 Expected Deviation

Observed Mean Value 55 62 58.5

-1.5 -6.5

generation and shows considerable variation in range between rates of progeny of high and low level dams. The progeny of the low and high level Cx dams deviated from the mean of all 3-way crosses by — 5% and 8%, respectively. The progeny of Cy had about the same rates from dams at each level while Cz had a range between these extremes. The mean deviation of all low and high level dams was — 3 % and 2% respectively, which indicates selection could change production by this amount from the population mean in one generation. An analysis was made of the production rates of the 3-way crosses when classified according to their dams level or rank with the results shown in Table 8. This analysis is of a hierarchal type where family level and family rank and individual rank are assumed to be fixed effects and male lines, female lines and pens random variables. Data were available for the offspring of

Deviation

Mean

Expected Deviation

0.5 7.5 4.0

6.5 1.5

57 52 54.5

Deviation

2.5 -2.5 0.0

only 79 of the 96 birds used as breeders. The usual analysis of variance for age sexual maturity, with the assumption of proportional numbers, was obviously not valid as it gave a negative sum of squares for interaction. A Chi square test showed the observations per cell were not significantly different from the expected number based on marginal means, so the method of expected numbers as described by Snedecor (1934) was used. This method uses the product of the observed cell mean and expected number of observations to obtain an adjusted sum. The adjusted sums and expected number of observations per cell were used in an analysis of variance with the results shown in Table 8. There was only one dam of a given individual rank per pen so no estimate of the variance within individual ranks was available. The interactions of pens with levels and pens with ranks are assumed to measure uncontrolled variation. As these inter-

TABLE 7.—Rate 1 of dam's populations, means of low and high level individual dams, their offspring, deviation of of spring from dam, and deviation of of spring from their own mean Level of Dam's Population Cx

Dam's population Mean of individual dams Mean of offspring Offspring minus dam Deviation of offspring from their pooled meani

Cz

Cy

Low

High

Low

High

Low

High

51 39 49 10 — - 55

51 64 62 -2 8

69 55 55 0 1

69 77 54 -23 0

60 46 50 4 -4

60 77 53 -24 -1

Low

High

60 47 51 4 -3

60 73 56 -17 2

933

SELECTION FOR EGG PRODUCTION

TABLE 8.—Analysis of variance of the mean rate 1 values of offspring relative to the genetic composition and production rank of their dams Source

d/f

M.S.

Total Female line Male line/female Pen replication/M/F Family level/M/F Family rank/level/M/F PenXlevel/M/F Pen X rank/level/M/F Individual rank/pen/level/M/F Pooled pen interactions for error Within ind. rank

781 2 3 6 6 12 6 1023 33 16 0

183 947 32 357 85 229 204 156 213

1 2 3

F.

—

4.45

—

—

Probability

(T2+n
—

.02

—

1.68

.20

— — — — —

— — — — —

Variance Components

would be 95 if all cells filled. would be 12 if all cells filled. would be 48 if all cells filled.

dams started laying 3 days later and 3 days earlier respectively than the mean of all 3-way crosses. The analysis of variance of the correlated responses shown in Table 10 were also calculated by the method of expected numbers. The male line differences were significant at below the 25% level for all traits. The most significant difference was at the 5% level for age of first egg. The differences in egg weight among the female lines were significant at the 16% level. This was the only trait in which the female lines showed any indication of a significant difference. The 4% and 17% probability levels for difference among pens for egg weight and age sexual maturity respectively were not related to any known pen environmental effects. The family rank and family level had little effect on any of the correlated responses of the offspring.

actions were similar in nature and value, they were pooled to give an error term with a mean square of 213 with 16 degrees of freedom. The offspring from the two male lines with each female group were significantly different at the 2% level. The difference in family level had a probability of 20% of being due to chance. None of the other grouping approached significance. Correlated responses are shown in Table 9. The 3-way crosses were classified as their dam's level of egg production. Rates 2, 3, 4, and 5 show the same general trend, but to a smaller degree than for rate 1, which was the basis of selection. A negative relation exists between production rate of dams and mature egg weight of offspring. The progeny of low and high level dams showed deviations from their mean of 2.8 and —2.8 grams per egg respectively. The progeny of the low and high level

TABLE 9.—Correlated responses to selection on production of rate 1, in other rates, mature egg weight and age first egg by dam's population, means of low and high level individual dams, their of spring, deviation of offspring from dam and deviation of offspring from their own mean Rate 3

Rate 2 Low

Dam's population 77 Mean of Ind. dams used 72 Mean of offspring 69 Deviation of offspring from their mean —1

High 77 84 71

Low 64 64 60

1

High 64 67 60

Rate 4 Low 63 58 57

High 63 69 60

Rate 5 Low 68 65 63

High 68 72 65

Mature egg wt. Low

Hight

Grams 61 .6 61.6 60 .8 59.7 62 .4 56.7 2.8

Age 1st egg Low

High Days

176 188 183

176 168 177

934

A. B. STEPHENSON, Q. B. KINDER AND E. M. FUNK DISCUSSION

The dam's family deviation and individual deviations being of approximately the same value in predicting the production rate of the progeny was not expected. Theoretically, traits of low heritability are more closely related to family means than individual values. Heritability estimates of egg production in populations selected over several generations have generally shown low values. In these data the dams were mated to males not selected for this genetic combination and the progeny responded to individual selection to a greater degree than would have been expected within populations having undergone several generations of selection. Some of the decline in production of the progeny of the Cy dams was most likely due to a social disadvantage of plumage color. About half of the pullets in this cross had colored plumage and were in pens where most of the birds had predominately white feathers. Information on individual birds regarding the relation between egg production and plumage color was not available. A loss of genetic recombinations could

be responsible for a portion of the general decline from 2-way to 3-way crosses. Improvement in recurrent selection populations was by selection within the noninbred female line. The relative value of general and specific combining ability were confounded in this type of selection because matings were made to only one male line. If non-additive traits were important, some genetic recombination loss would be expected in the progeny from 2-way cross dams with unselected males. Such a loss was observed by Hill and Nordskog (1958). Their data showed, that among 2-way crosses of Leghorns and heavy breeds, general and specific combining ability accounted for 12% and 7%, respectively, of the total variance in hen day egg production. Three-way crosses among the same lines showed general and specific combining ability accounted for only 3% and 1%, respectively of the total variance. These lines had not been selected on previous cross performance. Hazel and Lamoreux (1947) in a non-inbred population found specific combining ability to have little influence on sexual maturity or body weight. Goto and Nordskog (1959) found

TABLE 10.—Analysis oj variance of the responses correlated with rate 1 value oj of spring relative to the

genetic composition and production rank oj their dams Rate 2 Source

M.S. P.

M.S.

— —

383 213 87 118

— — — —

213 312 45 197

Total Female line Male line/F Pen R e p / M / F Family level/M/F Family rank/level/ M/F Pen X Level Pen X Rank Ind. Rank

77i 2 3 6 6

158 227 35 116

12 6 102 32 3

134 122 80 121

Pooled Error

16

97

1 2 3

Rate 3

Rate 4

Rate 5

d/f

would be 95 if all cells filled. would be 12 if all cells filled. would be 48 if all cells filled.

—

.14

145

P.

M.S.

—

121 305 38 149

.25

— — .25

— — —

112 173 94 139 123

P.

M.S.

— — —

251 168 83 122

— — — —

163 174 64 135

.10

105

Mature Egg Weight

Age 1st egg

P.

M.S.

P.

M.S.

—

1,747 256 425 125

.16 .21 .04

600 — 703 .05 147 .17 479 .005

.24

— — .22

— — —

164 144 145 146

104 33 108 67

145

80

P.

— — — —

SELECTION FOR EGG PRODUCTION

no indication of specific combining ability for 300 day hen-housed production rate in white egg crosses; however, in brown egg crosses specific combining ability accounted for 16% of the total variance in production rate. In these data, specific combining ability had approximately twice as much influence as general combining ability. SUMMARY

Three populations of 2-way cross dams were each mated with 2 unrelated inbred male lines. Selection among the dams, on both a family and individual basis, was made for both high and low rates of egg production from 22 to about 37 weeks of age. The expected deviation of the offspring from unselected inbred sires and 2-way cross dams was: y = .19 Xi + .24 x2 where xt and x2 were rates of the dam's family deviation and individual deviation respectively. These coefficients are significantly different from zero. Family and individual rates of the dam were of about equal predictive value. Mean production was 6% less among the 3-way cross progeny than their 2-way cross dams. Two control populations showed little difference in annual environmental effects for these years. This decrease in production was probably due to loss of genetic recombinations and a social disadvantage of colored plumage of 1/6 of progeny in pens where 95% of the birds were predominately white. The loss of genetic recombinations and other factors confounded with years or generations, decreased production at about twice the rate that selection increased production. Differences between the progeny of male lines for egg production from 22 to about 37 weeks of age were significant at the 2% level. This trait was the basis of dam selec-

935

tion. The correlated responses for production from 22 to 64 weeks and from 1st egg to 34 weeks were significant at the 10% and 14% level respectively. Differences among other rates were of questionable significance. The progeny when classified by their sire's line were different in age at sexual maturity at the 0.5% probability level. Mature egg weight was the only trait in which the differences among the dam lines showed any indication of significance. Differences in the dam's family level were related to significant differences in their progeny at age at first egg. None of the other correlated traits were significantly different when grouped by family level or rank within level. REFERENCES Goto, E., and A. W. Nordskog, 1959. Heterosis in poultry. 4. Estimation of combining ability variance from diallel crosses of inbred lines of the fowl. Poultry Sci. 38: 1381-1388. Hazel, L. N., and W. F. Lamoreux, 1947. Heritability, maternal effects and nicking in relation to sexual maturity and body weight in White Leghorns. Poultry Sci. 26: 508-514. Hill, J. F., and A. W. Nordskog, 1958. Heterosis in poultry. 3. Predicting combining ability of performance in the crossbred fowl. Poultry Sci. 37: 1159-1169. Kusner, H. F., 1957. (The effectiveness in poultry breeding of 2-breed crisscross breeding.) Dolk. Adad, Selskohoz. Nauk Lenin. 22(2): 29-32. Animal Breeding Abstracts, 1958. Review 417. Kinder, Q. B., A. B. Stephenson and E. M. Funk, 1960. Comparison of purebreds, crosses and hybrids for egg production. Missouri Agricultural Experiment Station Bulletin 754. Laurent, F., 1953. Production d'hybrids provenenant de 3 races. Tri-way cross. Revue d'Oka, 25: 51. Lush, J. L., 1945. Animal Breeding Plans. 3rd Edition. The Collegiate Press, Ames, Iowa. Maw, A. J. G., 1942. Crosses between inbred lines of the domestic fowl. Poultry Sci. 2 1 : 548553. Skaller, F., 1954. Crossbreeding in poultry. Worlds Poultry Sci. J. 10: 58-59. Snedecor, G. W., 1934. The method of expected

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numbers for tables of multiple classification with disproportionate subclass numbers. J. Amer. Stat. Assn. 29: 389-393. Snedecor, G. W., 1956. Statistical Methods. The Iowa State College Press.

FUNK

Warren, D. C , 1953. Practical Poultry Breeding. MacMillan. Water, N. F., 1938. The influence of inbred sires top crossed on White Leghorn fowl. Poultry Sci. 17: 490-497.

Effects of Dietary Protein Level on Performance of Four Commercial Egg Production Stocks JAMES W. DEATON AND J O H N H. QUISENBEREY Texas A&M University, College Station, Texas (Received for publication October 13, 1964)

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ITH the advent of commercialization in the poultry industry there has been a decrease in the number of breeders of egg production stocks, and in turn, an increase in the number of laying hens produced by one breeder. Since this trend is expected to continue, the genetic influence of one breeder's stock will become more widespread and the assumption is made that each breeder's stock will have a different genetic background. In order to attain the precision that is necessary to maintain progress in a breeding program, the bird sold by the breeder of the future will probably have specific nutritional and environmental requirements. Since protein is one of the more expensive items in a laying ration, considerable work has been done to determine the minimum ended for optimum returns. Several workers, Neywang et al. (1955), Miller et al. (1956), Frank and Waibel (1959), Griminger and Fisher (1959), Thornton et al. (1957) and Thornton and Whittet (1959), have reported satisfactory egg production with protein levels of 13-15%. Other workers, Reid et al. (1951), Quisenberry and Bradley (1962), Milton and Ingram (1957) and Denton and Lillie (1959), have reported optimum performance from protein levels above 15%.

Considerable controversy exists concerning the amount of protein necessary for optimum performance. These differences in results could be due in part to differences in strains of birds used by the various investigators. Thornton and Whittet (I960), using four different strains of egg production stocks and four levels of protein, could find no consistent trends; whereas, Moreng et al. (1963) using three different levels of dietary protein on four commercial strains of egg type chickens found highly significant differences in Haugh unit values within the same season, strain and dietary protein level. An interaction of strain and diet for egg production was also found to exist. Harms and Waldroup (1962) reported a significant strain X protein level interaction as measured by rate of egg production. This present study was conducted to determine if genetic differences in protein requirements existed between four commercial egg production stocks made available to the Texas A&M University Poultry Science Department. EXPERIMENTAL PROCEDURE

Sexed day-old chicks hatched March 7, 1961, representing four nationally-known egg production stocks, were wing banded