Genetic and Phenotypic Variation in Randombred White Leghorn Controls over Several Generations1

Genetic and Phenotypic Variation in Randombred White Leghorn Controls over Several Generations1 T. B. KINNEY, JR., 2 P. C. LOWE,2 B. B. BOHREN3 AND S. P. WILSON4 United States Department of Agriculture, and Purdue University Agricultural Experiment Station, Lafayette, Indiana 47907 (Received for publication May 10, 1967)

I

Journal Paper No. 3070 of the Purdue University Agricultural Experiment Station. 1 This investigation was conducted as a portion of the Cooperative research of the NC-47 Regional Poultry Breeding Project entitled "Evaluation of Breeding Systems for Chickens." 2 Poultry Research Branch, Animal Husbandry Research Division, ARS Regional Poultry Breeding Laboratory, Lafayette, Indiana. 3 Department of Animal Science, Purdue University, Lafayette, Indiana. "Poultry Research Branch, AHRD, ARS, Beltsville, Maryland.

year period. These workers concluded that no important genetic trends existed for body weight, sexual maturity, egg production or egg quality traits studied. The study reported here concerns a population referred to as the Regional Cornell Control which originated from a sample of the Cornell Control population utilized in the study by King et al. (1963). The origin of this population has been discussed in detail by King et al. (1959). A sample of the population was transferred to the North Central Regional Poultry Breeding Laboratory at Purdue University in 1956. Since that time the population has been maintained as a randombred control and samples have been utilized extensively by random sample tests and poultry research groups throughout the United States and Canada. It has also served as the base population for many selection studies. The purposes of this study were: 1. To determine whether changes in the means, genetic variances or heritabilities of a number of economic traits have occurred during the first eight generations. 2. To estimate the heritabilities of and genetic correlations between economic traits of interest in this population. MATING PROCEDURES AND MANAGEMENT

The Regional Cornell Control population is reproduced each year with 50 sires each mated to five dams. Females are assigned to males at random with the restriction that

113

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T IS A generally accepted fact that adequate controls are essential for the estimation of genetic gain in selection studies. Lerner (1950), Dickerson (1955), Goodwin et al. (1955), Go we and Johnson (1956), King et al. (1959) and others have recognized and discussed the value of control strains for the separation of genetic and environmental effects. Gowe et al. (1959) clearly demonstrated the value of a control strain by comparing absolute trends of two selected strains with trends estimated by use of deviations from a control population. These workers also studied changes in this White Leghorn Control Population during six years by regressing annual means on generation number. No significant changes in hen-housed and survivor egg production, body weight at housing, March body weight or laying house mortality were noted. A significant increase in March egg weight and a significant decrease in sexual maturity were observed. King et al. (1963) investigated the genetic stability of eight traits of the Cornell Randombred Control Population of White Leghorns over a six

114

T. B. KINNEY, JR., P. C. LOWE, B. B. BOHREN AND S. P. WILSON

THE DATA AND ANALYTICAL PROCEDURES This study is based on data collected from shift one and two during the eight years from 1957 to 1964. The traits measured on each female are defined as follows: 1. Eight-week body weight (grams). 2. Thirty-two week body weight (grams). 3. Fifty-five week body weight (grams).

4. Thirty-two week egg weight (grams), of eggs from three consecutive trap days. 5. Fifty-five week egg weight (grams). 6. Age in weeks at first egg. 7. Albumen score—a visual score ranging from one to nine and based on the USDA egg quality chart. 8. Specific gravity measures obtained from salt solutions with hydrometer readings ranging from 1.060 to greater than 1.100 and scored 0-9. 9. Shape index—the ratio of egg width to length. 10. Percent production from first egg to 40-weeks of age based on a three day per week trap record (Period A % ) . 11. Percent production from 40 to 55 weeks of age based on a three day per week trap record (Period B %). 12. Percent production from 55 to 70 weeks of age based on a three day per week trap record (Period C % ) . 13. Percent production from first egg to 70 weeks of age based on a three day per week trap record (Total % Prod.). Individual hen records were excluded if a hen started laying prior to housing, had less than 10 trap days in which to make her record, a zero production record or was recorded as sick. It was felt that removal of these records would cause less bias in the estimates of parameters than would their inclusion. Shift one and two data could not be regarded as independent because the same sires and dams were used in both shifts. For this reason the data from the two shifts were analyzed separately. Data for each shift-year subclass were analyzed by use of nested analyses of variance and covariance appropriate to the hierarchal model assumed as follows: Yijk = fi + Si + djj + e i j k

(1)

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no full or half-sib matings are made. Full pedigree records are maintained. An attempt is made to obtain one surviving son from each sire and one daugher from each dam. This generally has been possible but in those instances where no sons survive from a particular sire a replacement is randomly selected from another sire family with the restriction that he come from a dam family which has not already contributed a son. Similarly a dam which has no surviving daughters is replaced by a daughter drawn at random with the restriction that no dam family contributes more than two progeny. In addition to the breeder flock, two pedigreed hatches of birds are made each year. The first hatch referred to as shift one is obtained from the breeder flock matings. Following collection of eggs for shift one, the SO sires and 250 dams are re-mated with each sire being mated to a new group of dams. After two weeks, eggs are saved and a second pedigreed hatch referred to as shift two is obtained. In both shift one and two, each dam is represented equally by progeny insofar as possible. Incubation, brooding, rearing, housing, rations, disease control and other management aspects as well as facilities have remained constant in that no physical changes in these factors have been made since 1956. The birds are brooded to 8-weeks of age and moved to range where they remain until housed at 20-22 weeks of age.

VARIATION IN CONTROLS

where:

115

TABLE 1.—Range in number of sires, dams and progeny used in pooled variance and covariance analyses

A nested analysis of variance and covariance program by Bogyo (1965) was used for all analyses of variance (covariance)

These significant regressions, particularly the regressions of the shift mean averages, suggest that a downward trend exists in

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Yijk=an observation on the k-th progeny of the j-th dam and the i-th Minimum Maximum sire. Shift 1 Shift 2 Shift 1 Shift 2 Ai=the population mean. s; = the effect of the i-th sire. 395 396 Sires 392 392 1,300 1,210 1,220 1,144 dij = the effect of the j-th dam mated Dams 2,520 2,510 Progeny 2,186 2,191 to the i-th sire. eijk = is a random residual effect of the k-th progeny of the j-th dam and and calculations outlined above. i-th sire. Because of missing observations several All elements of the model are considered sets of analyses were run in order to utilize to be independent and except for /u are as much of the data as possible. The miniassumed to be uncorrelated random effects 2 2 mum and maximum numbers of sires, dams with zero means and variances o-s ,
5 3 . 6 + .46 5 3 . 7 + .59 53.65

50.4+.70 5 0 . 8 + .58 50.60

5 6 . 2 ± .54 5 7 . 1 ± .45 56.65

57.li.67 S8.4+.65 57.75

5 3 . 0 ± .82 50.7+.84 51.85

55.7+.59 5 6 . 2 + .53 55.95

1 2 Ave.

1 2 Ave.

% Prod.

% Prod.

% Prod.

* Significant at the .05 level of probability. ** Significant a t the .01 level of probability. *** Significant a t the .10 level of probability.

Total % Prod.

Per. C

1 2 Ave.

50.1±.74 5 0 . 1 + .91 50.10

58.1±.68 59.S±.63 58.80

5 7 . 1 + .78 6 0 . 4 + .51 58.75

1 2 Ave.

Per. A

Per. B

60.8±.62 60.5+.49 60.65

.72±.002 .73±.003 .725

1 2 Ave.

Egg Shape

. 7 2 + .002 .73+.002 .725

3.0+.10 2 . 8 ± .09 2.90

3 . 0 + .10 3 . 3 ± .08 3.15

1 2 Ave.

Specific Gravity Score

3 . 1 + .08 2 . 9 + .06 3.00

3.9+.06 4 . 0 ± .06 3.95

1 2 Ave.

Albumen Quality Score

25.3+.14 27.0±.14 26.15

2 6 . 1 + .14 2 6 . 9 + .13 26.50

1 2 Ave.

Wks. to 1st Egg

5 3 . 3 + .68 54.3+.77 52.80

57.6+.52 57.1+.59 57.35

.73+.002 .72+.002 .725

3 . 0 + .10 2.7+.10 2.85

3.1+.06 3 . 3 + .09 3.20

2 5 . 3 + .15 2 5 . 8 + .13 25.55

61.3+.30 S8.9+.31 60.10

59.5+.28 6 0 . 5 + .27 60.00

60.9+.31 6 0 . 3 + .27 60.60

1 2 Ave.

55-Week Egg Wt. (Grams)

51.7+.26 51.6+.25 51.65

5 1 . 2 + .22 52.4+.20 51.80

5 5

1,795+ 14 1,772+ 13 1,784

668+ 591+ 630

5 2 . 8 + .27 54.3+.21 53.65

1 2 Ave.

32-Week Egg W t . (Grams)

5 5

1,958+ 14 2 , 0 0 8 + 15 1,983

618+ 577+ 598

1,693+ 14 2 , 0 1 3 ± 14 1,988

1 2 Ave.

55- Week Body W t . (Grams)

5 5

1959-60

1,977± 23 2 , 0 1 8 ± 18 1,998

1 2 Ave.

32-Week Body W t . (Grams)

750+ 673+ 712

1958-59

1,827+ 14 1,849+ 14 1,838

t

2 Ave.

8-Week Body W t . (Grams)

1957-58 5 6

56.5+.54 5 4 . 8 ± .72 55.65

50.9+.80 5 0 . 2 + .98 50.65

58.9+.64 54.9±.95 56.90

60.4+.63 60.1+.74 60.25

.72+.002 . 7 2 + .003 .720

4.0+.10 3.7+.10 3.85

4.5+.08 4.3+.08 4.40

2 5 . 7 + .13 26.0+.09 25.85

5 9 . 9 + .30 5 9 . 3 + . 37 59.60

51.8+.27 5 2 . 6 ± .29 52.20

2 , 0 2 2 + 18 2 , 0 4 9 + 20 2,037

1,818+ 15 1,849+ 16 1,834

627+ 586+ 606

1960-61 3 3

55.3+.48 5 5 . 6 + .41 55.45

51.4+.66 51.8+.64 51.60

5 5 . 4 + .63 5 5 . 2 + . 55 55.30

59.3+.54 60.3+.47 59.80

. 7 2 + .002 .72+.002 .720

3 . 8 + .08 3.5+.07 3.65

4 . 4 + .06 4 . 4 + .06 4.40

25.0+.14 2 4 . 6 + .09 24.80

6 0 . 3 + .25 60.3+.23 60.30

52.2+.25 52.9±.20 52.55

1,995+ 13 2 , 0 3 6 + 13 2,016

1,763+ 11 1,858+ 11 1,811

586+ 645+ 616

1961-62 4 4

5 4 . 5 + .43 5 4 . 4 + .55 54.45

5 1 . 8 + .63 52.7+.65 52.25

5 3 . 3 + .59 5 6 . 2 + .61 54.75

5 8 . 5 + .46 5 6 . 8 + .53 57.65

. 7 2 + .002 . 7 2 + .002 .720

3 . 5 + . 08 3 . 7 + .08 3.60

3 . 9 + .06 3 . 7 ± .06 3.80

24.5+.10 25.0+.11 24.75

59.2+.26 5 9 . 0 + .27 59.10

51.3+.21 51.7+.21 51.50

2 , 0 3 6 + 14 2 , 0 8 6 ± 15 2,061

1,781+ 11 1,845± 14 1,813

609+ 591+ 600

1962-63

55.4± 53.9± 54.65

52.3± 51.5± 51.90

54.4+ . 52.9+ . 53.65

60.1±. 57.4±. 58.75

.72+. .72±. .720

3.7±. 3.8±. 3.75

4.3±. 4.1± . 4.20

25.2±. 2S.0±. 25.10

59.4±. 58.5±. 58.95

50.8± . 51.7±. 51.25

2,095± 2,031± 2,063

1,813± 1,777± 1,795

568+ 609 ± 589

1963-6

means and standard errors, shift averages by years, number of progeny

1,858+ 14 1,836± 18 1,847

Shift

Trait

TABLE 2.-Shift-year

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VARIATION IN CONTROLS

117

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eight and 32-week body weight, 32- and Changes in genetic variances and herita55-week egg weight and weeks to first egg. bilities over time—A time trend in addiThese observations are at variance with the tive genetic variance and/or heritability observations of King et al. (1963) from a might be an indication of genetic change study of the Regional Cornell Control pop- due to natural selection, genetic drift, inulation over six years. These workers found breeding or other forces. In Table 3 the sire essentially no trend for eight-week body components of variance, which are estimates weight or sexual maturity in either shift of one-fourth the additive genetic variance and opposing trends for egg weight in the are presented by shift-year subclasses along two shifts. Gowe et al. (1959) reported a with the regressions on years for the thirsignificant decrease in days to sexual matur- teen traits. The averages of the shift-year ity in the control population which they means and their regressions on time are also presented. The regression coefficients are studied for six generations. The regressions of both albumen quality non-signficant for all traits except 55-week and specific gravity on time were positive egg weight. In this trait the shift on regresfor both shifts and for the average of the sion as well as the regression of shift mean average is positive and significantly greater shift means. The regressions of percent production on than zero. Shift-year estimates of the heritabilities time were negative in shift two for periods A and B percent production and for total for each of the 13 traits, averages of the percent production. The regressions of the shift means by years and the regressions on averages of the shift means on time were time are presented in Table 4. The regressignificant for periods B and C but non-sig- sion on time of shift mean averages of 55nificant for period A and total percent pro- week egg weight is positive and significantly greater than zero. For all other traits the duction. A study of the means of the Regional regressions are non-significant. The signifiRed Control population maintained at the cant regression of both genetic variance and North Central Regional Poultry Breeding heritability estimates on time in the case of Laboratory for nine generations revealed 55-week egg weight suggests the possibility the existence of significant negative regres- that a genetic change over time has taken sions of 32- and 55-week egg weight, place for this trait. It must be kept in 55-week body weight, age at 50 percent mind, however, that additive genetic variproduction, period A percent production ance and heritability are not independent. A and a significantly positive regression of al- significant regression of additive genetic bumen score on time. Eight week body variance on time would likely result in a weight was unfortunately not measured in significant regression of heritability on time this population after the fourth generation. if phenotypic variance remained relatively The results of the study of these two pop- constant from year to year. The significant ulations strongly suggest that the time regression of additive genetic variance for trends for egg weight, body weight, weeks 55-week egg weight might be due to chance. to first egg and albumen quality may be the The estimated genetic correlation between result of a time trend in the environment 32-week egg weight and 55-week egg during the period covered by this study. At weight in this population is greater than .90 this point, however, it is not possible to which indicates that these two traits are afconclude that these changes are non-genetic fected by many of the same genes. A genetic change affecting 55-week egg weight in nature.

10,117 9,911 10,014

13,483 14,515 13,999

1 2 Ave.

1 2 Ave.

1 2 Ave.

32-Week Body Wt. (Grams)

55-Week Body W t . (Grams)

32-Week Egg W t . (Grams)

55-Week Egg W t . (Grams)

19

.0 .0 .0

.1287 .4438 .2863 .1359 .1872 .1616 .2406 .1993 .2200 .0003 .0002 .00025 2.0538 -1.3776 .3381 -6.8030 .8210 -2.9910 -3.1137 2.9613 - .0762 -1.2036 -1.7541 - .4789

.7208 .4786 .5997 .0182 .0615 .0399 .3214 .0226 .1720 .0001 .0001 .00010 2.7173 -2.8877 - .0852 8.0589 -3.5045 2.2772 1.1785 -1.8508 -.3362 1.7632 -2.6992 -.4680

-.1910 .1978 .0034 .3407 .1230 .2319 .3095 .0482 .1789

9.5632 12.3817 18.4725 7.7364 13.1383 10.4374 -4.0385 10.5775 3.2695 4.3819 15.0695 9.7257

-.1903 .3035 .0566 -.0070 .2178 .1054 .3497 -.1599 .0949

3.5147 .4375 1.9761 2.7201 4.8391 3.7796 -.0456 -.2949 -.1703 .5450 -.1976 .1737

.6951 .3390 .5171

.0936 -.0507 .0215

.2061 .3371 .2716

.0002 .0001 .00015

3.8364 9.7527 6.7946

2.6212 13.6361 7.6287

4.8108 13.2966 9.0537

5.0257 9.5402 7.2830

.3461 .5000 .4231

.0863 -.0707 .0078

.6777 .1987 .4382

.0002 .0001 .00015

-4.7009 - .2964 -2.9847

3.3886 -7.2776 1.9445

4.3342 2.1345 3.2344

1.1905 .0328 .6117

1 2 Ave.

1 2 Ave.

1 2 Ave.

1 2 Ave.

1 2 Ave.

1 2 Ave.

1 2 Ave.

1 2 Ave.

Weeks to 1st Egg

Albumen Quality Score

Specific Gravity Score

Shape Index

Per. A % Prod.

Per. B % Prod.

Per. C % Prod.

Total % Prod.

** Significant at the .10 level of probability.

.0002 .0001 .00015

2.5582 2.7191 2.6387

2.5547 1.9979 2.2763

2.3356 .1327 1.2342

3.7713 2.9740 3.3727

.9666 1.8920 1.4293

1.2204 .7523 .9864

1 2 Ave.

.0001 .0002 .00015

.4 .1 .3

1.5043 2.6939 2.0991

2.0211 .3584 1.1898

-.0437 .4656 .2110

3.5746 1.8902 2.7324

1.3106 3.0095 2.1601

3.0546 1.5069 2.2808

4.4 1.3 2.9

4.4 -2.6 .8

7.4 1.7 4.5

3.9 7.8 5.8

.1 .0 .0

.3 .4 .3

4.98 1.7 3.34

.5 1.3 .9

20,4 -1,3 9,5

20,008 8,796 14,402

11,687 7,660 9,674

6,793 11,666 9,230 27,193 19,905 23,549

13,38 2,2 7,8

1,

7,454 8,734 8,094

784 743 764

1962

7,206 7,722 7,464

888 227 558

557 1,466 1,012 9,106 9,932 9,519

1961

1960

6,979 4,935 5,957

847 950 899

1959

and

14,453 9,828 12,141

909 268 589

1958

estimates of sire components of variance, shift averages by years•

8,713 7,805 8,259

1,135 764 1,000

1 2 Ave.

1957

Shift

Trait

8-Week Body W t . (Grams)

TABLE 3 . --Shift-year

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. 8 0 + .33 - . 4 6 + . 24 .170

.78+.36 .56 + .28 .670

.73+.34 .45+.32 .590

.21+.30 . 1 5 + .29 .180

. 2 8 + .22 .35+.25 .315

. 3 8 + . 27 - . 2 8 + . 25 .050

1.22+.35 .43+.25 .825

1.04+.38 . 3 0 + .24 .670

— .01+ .19 .12+.27 .055

1 2 Ave.

1 2 Ave.

1 2 Ave.

1 2 Ave.

1 2 Ave.

1 2 Ave.

1 2 Ave.

1 2 Ave.

1 2 Ave.

1 2 Ave.

1 2 Ave.

1 2 Ave.

32-Week Body Wt. (Grams)

55-Week Body W t . (Grams)

32-Week Egg W t . (Grams)

S5-Week Egg W t . (Grams)

Weeks to 1st Egg

Albumen Quality Score

Specific Gravity Score

Shape Index

Per. A % Prod.

Per. B % Prod.

Per. C % Prod.

Total % Prod. - . 0 4 + .22 - . 0 1 + .24 -.025

. 2 4 + .24 - . 0 2 + .28 .110

.05+.24 . 0 0 + .22 .025

** Significant at the .10 level of probability.

- . 0 1 + .21 - . 0 7 + .21 -.040

. 4 8 + .24 . 6 8 + .40 .580

- . 0 4 + .22 . 1 2 + .25 .040

. 1 2 + .23 - . 1 2 + .19 .000

.02±.22 .09+.22 .055

. 3 8 ± .27 . 5 7 + .30 .475

.59±.28 -.31+.27 .140

-.03+.27 .48±,27 .225

- . 1 3 + .23 . 2 6 ± .27 .065

. 7 1 ± .37 .52+.30 .615

.84±,36 .54±.34 .690

. 5 7 + .32 .54+.32 .555

.90+.35 .71+.34 .80S

. 5 9 + .30 . 5 3 + .33 .560

1959

.41+.20 .13+.22 .270

-.03+.29 .08+.22 .025

1.09+.39 .35±.23 .720

.37+.26 . 5 8 + . 26 .475

. 2 6 + . 27 1.54+.47 .900

. 4 9 + .27 .22+.22 .355

.19+.26 . 3 6 + .27 .275

.38+.28 .90+.30 .640

.52+.27 . 4 3 + .31 .475

. 7 2 + . 31 .83±.35 .775

. 6 7 + . 31 .18+.26 .425

1958

- . 2 1 + .20 ,10±.21 -.055

. 7 4 + .35 . 5 6 ± .31 .655

1 2 Ave.

1957

Shift

Trait

8-Week Body Wt. (Grams)

1961

1962

. 5 0 + .24 .42±.24 .460 . 8 5 + .28 .63+.26 .740 - . 0 6 + .13 -.22+.12 -.140

. 6 7 + . 28 .61+.19 .640 .50+.23 . 4 7 + .25 .485 -.14+.14 . 2 3 + .19 .045

. 5 6 + .33 . 3 8 + .35 .470 1.01 + .39 .30+.27 .655

.08+.16 - . 1 3 + .14 -.025 — .07±.15 - . 1 0 + .15 -.135

-.05+.13 .11+.17 .030 .09±.17 -.17+.14 -.040

. 2 3 + .30 . 1 3 ± .24 .180 . 2 4 + .26 . S 9 ± .34 .415

-.03+.18 - . 0 9 + .14 -.060

-.13+.16 . 0 3 + .14 -.050

. 3 0 + .34 - . 1 0 ± .22 .100

.71+.35 . 1 1 + .34 .410

. 5 3 + .25 . 6 9 + .28 .610

.59+.19 . 2 3 + .23 .410

.48+.23 .49+.24 .485

. 5 2 + .25 . 4 6 + .23 .480

.99±.38 . 5 3 ± .34 .760

.42±.22 .75+.28 .585

. 3 9 + .19 .10+.19 .245

.16+.19 .45+.24 .305

1.14+ .33 . 4 3 + .21 .785

.72+.26 . 4 7 ± .23 .595

. 4 3 + .21 . 6 1 ± .23 .520

. 8 4 + .29 .66+.24 .750

.67+.27 . 6 8 + .27 .675

. 6 7 + .26 .41+.25 .540

. 9 0 + .30 .22+.23 .560

- . 1 8 + .23 . 4 7 ± .32 .145

.47+.31 . 0 2 + .38 .245

-.01+.26 . 1 2 + .34 .550

1.33+.41 1.02+.43 1.175

1.05+ .37 .79+.42 .920

.50±31 .77+.41 .635

1960

TABLE 4.—Shift-year heritability estimates and standard errors, shift averages by years an

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120

T. B. KINNEY, JR., P. C. LOWE, B. B. BOHREN AND S. P. WILSON

Heritabilities and genetic correlations— The primary reason for presenting the heritability and genetic correlation estimates obtained in this study is the fact that they should be useful to many researchers who have utilized or who may in the future utilize samples of the Regional Cornell Control population for genetic studies. Pooled estimates of heritabilities and genetic correlations for the 13 traits are presented for shift one and two, along with an unweighted average of the estimates from both shifts, in Table 5. With the exception of egg shape, Per. A percent and Per. B percent production, the estimates obtained in this study are directly comparable with the paternal half-sib correlation estimates reported by King (1961) and King et al. (1963) from studies of this same population. Most estimates reported in the literature have been obtained from selected populations and comparison with estimates reported here is not strictly

valid. However, the results of Friars et al. (1962) suggest that the effect of selection on changes in heritability may not be very important over as many as ten generations. This is particularly true of genetic correlations which may change in magnitude and/ direction as selection is practiced (Bohren et al., 1966). As a matter of interest, a summary of average heritability estimates from the literature, estimates reported by King (1961) and King et al. (1963) and estimates from this study for ten traits is presented in Table 6. The heritability estimates obtained in this study agree closely with estimates reported by King (1961) and King et al. (1963) as might be expected. There is also close agreement between average estimates from the literature, estimates from this study and those reported by King (1961) and King et al. (1963). This is not very surprising because most populations from which estimates have been reported in the literature were under selection for a relatively short period of time. For the ten traits in Table 6, agreement between the genetic correlations of this study and those reported by King (1961) and King et al. (1963) is as good as might be expected in view of the large sampling variance associated with genetic correlation estimates. SUMMARY Data from eight generations of the Regional Cornell Control population of S. C. White Leghorns were analyzed to obtain estimates of phenotypic means, components of variance and covariance, heritabilities and genetic correlations for 13 economic traits. The means of each trait were regressed on generation number to determine whether there were time trends for any of the traits. Estimates of sire components of variance and heritabilities were also regressed on generation number to determine

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might then be expected to affect 32-week egg weight. The regressions of genetic variances and heritabilities for 32-egg weight were not significant, thus raising a question about the basis of the significant regression for SS-week egg weight. While the regressions of estimates of genetic variances and heritabilities on time do not provide any evidence for genetic changes in the traits studied, with the possible exception of 55-week egg weight, the possibility of genetic changes having occurred cannot be ruled out. The argument for directional changes in the environment causing time trends in the phenotypic means of some traits is reasonable in view of the results discussed in the previous section, however, the change may well be a combination of genetic and environmental factors. Data from this line over several more generations may permit a more conclusive evaluation of time trends and their causes.

1 1

. 4 8 + .09 . 4 3 + .10 .45

. 8 6 + . 11 .41+ .09 .63

. 8 6 ± .05 . 8 8 + .04 .87

32-Wk. body wt.

- , 6 3 ± .08 - . 2 2 + .18 -.42 - . 1 9 + . 10 . 0 2 ± .16 -.08

- . 1 5 + .13 -.03+.23 -.09 . 6 2 + .10 . 3 0 + .09 .46

- . 1 1 + . 15 . 0 3 ± .21 -.04 - . 2 0 ± .20 -.27+.18 -.26 . 3 8 + .09 .23+.09 .30

,40±.13 . 6 0 + .11 .50 .27+.08 .38+.08 .32

.96+* ,94±» .95 . 5 2 + . 10 .41+.09 .46

. 5 3 + .09 . 5 1 + .10 .52

~

.47±.13 .22+ .17 .34

- . 2 0 + .14 - . 1 2 + .19 -.16

. 4 6 + .11 . 6 9 + .09 .57

.46+.08 . 2 2 ± .15 .34

.44+.09 . 2 2 + .16 .33

. 8 5 + .11 . 4 1 + .09 .63 . 3 2 + .12 .24+.15 .28

.17+.14 .18+.14 .17 . 0 4 + . 12 - . 2 4 + .17 -.10

-.02±.12 — . 1 3 ± .16 -.07

- . 0 5 + .11 . 1 6 + .19 .05

- . 0 6 + .10 . 3 1 + .16 .12

- . 0 1 + .09 . 0 9 + .18 .04

-.14+.08 -.03±.15 -.08

.74+.10 .49+.09 .61

.07+.16 . 1 6 + . 14 .11

.09+.11 . 2 7 ± .13 .18

.26+.10 . 2 4 + . 13 .25

- . 1 1 + .08 . 0 3 ± .14 -.03

- . 0 1 ± .11 . 1 1 ± .13 .05

- . 0 8 ± .22 + . 2 0 + .14 .06

. 4 9 + .14 .30+.14 .39

- . 1 1 + .12 - . 1 2 + .18 -.11

. 4 7 + .08 .22+.14 .34

- . 0 2 + .15 - . 3 9 + .18 -.20

Shape index

.97±.05 1.16+* 1.06

.00+.16 - . 0 2 + .16 -.01

Specific gravity

. 1 8 + .13 . 0 9 + .16 -.13

Albumen quality

. 2 0 + .12 . 1 2 + .15 .16

Sexual maturity

.77 + .05 . 8 6 + .04 .81

55-Wk. egg wt.

32-Wk. egg wt.

S5-Wk body wt.

Ileritabilities on diagonal, correlations off diagonal; first figure is Shift I, second figure Shift II and third figure an unweighted average. Standard error not meaningful when correlation is close to one.

% Prod. Total

Per. C % Prod.

Per. B % Prod.

Per. A % Prod.

Shape Index

Specific Gravity Score

Albumen Quality Score

Sexual Maturity (Weeks)

55-Week Egg Wt. (Grams)

32-Week Egg W t . (Grams)

55-Week Body W t . (Grams)

32-Week Body W t . (Grams)

8-Week Body W t . (Grams)

8-Wk. body wt.

TABLE S.—Pooled heritability and genetic correlation estimates and standard erro

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122

T. B. KINNEY, JR., P. C. LOWE, B. B. BOHREN AND S. P. WILSON TABLE 6.—Heritability1 or genetic corr Literature2 summary

Present study

.29 .87 .00 .36 .22 .15 .07

.45 .87 -.01 .16 .13 -.20 -.11

.37

.48 .02 .36 .38 .26 .17

.63 .17 .34 .39 -.07 -.08 -.07 .00

.51

55-Week Body Weight .26 Age at Maturity And: 32-Week Egg Weight .78 55-Week Egg Weight Albumen Score Specific Gravity % Prod, to J a n . 1 -.15 % Prod, to 72-Weeks - . 1 7

—

.44 .09 .32 .32 -.41 -.09

.63 .32 .57 .50 -.26 .34 -.22 -.15

.47 .34

.60 32-Week Egg Weight And: 55-Week Egg Weight Albumen Score Specific Gravity % Prod, to J a n . 1 -.50 % Prod, to 72-Weeks - . 2 4

.51 1.03 .04 .25

.52 .95 -.16 .12 -.55 -.23

.58

—

.53 .06 .41

.46 -.04 .05

.57

.10

.29 .03

.30 -.09 -.16

^35

—

.34

.06 .69 .16

— -

.46 .18 .80 .13

.35 .18

8-Week Body Weight And: 32-Week Body Weight Age a t M a t u r i t y 32-Week Egg Weight 55-Week Egg Weight Albumen Score Specific Gravity 32-Week Body Weight And: Age a t M a t u r i t y 32-Week Egg Weight 55-Week Egg Weight Albumen Score Specific Gravity % Prod, to J a n . 1 % Prod, to 72-weeks

55-Week Egg Weight And: Albumen Score Specific Gravity Albumen Score And: Specific Gravity % Prod, to 72-Weeks Specific Gravity % Prod, to Jan. 1 And: % Prod, to 72-weeks % Prod, to 72-Weeks 1 2

King

— — .62 .50 .33

.70 -.01

.34

REFERENCES

.20

Underlined values are heritability estimates. An average of estimates reported in the literature excluding estimates from unselected populations.

whether time trends existed for these parameter estimates. Results indicated that significant trends of phenotypic means exist for eight- and 32-week body weight, 32- and SS-week egg weight, weeks to first egg, albumen quality score and specific gravity. Regressions of sire components of variance and heritabilities on generation number were non-significant for all traits except SS-week egg weight. The results strongly suggest that the time trends in eight- and 3 2-week body weight, 32- and 55-week egg weight, weeks

Bogyo, T. P., 1965. WSU analysis of variance and covariance (Hernest). Completely nested classification with genetic variance (covariance) analysis. An unpublished mimeograph. Statistical Services, Washington State University, Pullman. Bohren, B. B., W. G. Hill and A. Robertson, 1966. Some observations on asymmetrical correlated responses to selection. Genet. Res. 7: 44-S7. Dickerson, G. E., 195S. Genetic slippage in response to selection for multiple objectives. Cold Spring Harbor Symposium on Quantitative Biology. 20: 213-224. Friars, G. W., B. B. Bohren and H. E. McKean, 1962. Time trends in estimates of genetic parameters in a population of chickens subjected to multiple objective selection. Poultry Sci. 4 1 : 1773-1784. Goodwin, K., G. E. Dickerson and W. F. Lamoreaux, 1955. A technique for measuring genetic progress in poultry breeding experiments. Poultry Sci. 34: 1197. Gowe, R. S., and A. S. Johnson, 1956. The performance of a control strain of S. C. White Leg-

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King et al. 1963

Traits correlated

to first egg, albumen quality score and specific gravity may be due to directional changes in the environment during the period covered by this study. The possibility of a combination of environmental and genetic factors causing the changes is recognized. The average heritability estimates were .45, .63 and .63 for eight, 32 and 55-week body weight; .52 and .46 for 32 and SS-week egg weight; .32, .30, .46 and .61 for sexual maturity, albumen quality, specific gravity and shape index; .18, .10, .08 and .13 for percent production to 40 weeks of age, 41 to 55 weeks of age, 56 to 70 weeks of age and total percent production to 70 weeks of age respectively. Heritability estimates agreed closely with previous estimates obtained from this population and with an average of estimates reported in the literature. Genetic correlation estimates varied widely but agreed reasonably well with previous estimates obtained from this population by other workers.

VARIATION IN CONTROLS horn stock over four generations on test at several locations. Poultry Sci. 35: 1146. Gowe, R. S., A. S. Johnson, J. H. Downs, R. Gibson, W. F. Mountain, J. H. Strain and B. F. Tinney, 1959. Environment and poultry breeding problems. 4. The value of a random-bred control strain in a selection study. Poultry Sci. 38: 443-462. King, S. C., 1961. Inheritance of economic traits in the Regional Cornell Control Population. Poultry Sci. 40: 975-986.

123

King, S. C , J. R. Carson and D. P. Doolittle, 1959. The Connecticut and Cornell randombred populations of chickens. World's Poultry Sci. J. I S : 139-159. King, S. C, L. D. Van Vleck and D. P. Doolittle, 1963. Genetic stability of the Cornell randombred control population of White Leghorns. Genet. Res. 4 : 290-304. Lerner, I. M., 1950. Population Genetics and Animal Improvement. Cambridge University Press, London, England.

R. L. PETERS, 1 J. E. FABER2 AND H. M. DEVOLT 3 Department of Veterinary Science and Department of Microbiology, University of Maryland, College Park, Maryland 20740 (Received for publication May 12, 1967)

I

N CHICKENS, Haemophilus gallinarum is the etiologic agent of an infectious coryza. Involvement of the lower respiratory tract, specifically the air-sacs, can occur without the presence of secondary invaders (Page, 1962). This fact complicates the large number of disease agents which cause similar gross pathologic lesions in the chicken respiratory system. Isolation of H. gallinarum from field cases is often difficult, especially if isolation is not attempted early in the clinical period (Bornstein and Samberg, 1954). Successful isolation must be followed by affirmation of pleomorphic, Condensation of a dissertation submitted to the Faculty of the Graduate School, University of Maryland, as a partial fulfillment of the requirements for the degree of Doctor of Philosophy. Scientific Article No. A1354. Contribution No. 3927 of the Maryland Agricultural Experiment Station. 1 Graduate Assistant, Department of Veterinary Science and Department of Microbiology. 2 Professor of Microbiology, Department of Microbiology. 3 Professor of Avian Pathology, Department of Veterinary Science.

gram-negative, pathogenic bacteria requiring the classical V factor (nicotinamide adenine dinucleotide, NAD) for growth. Blood and chocolate agars have been utilized as primary isolation media, since and including the work of DeBlieck (1932) and Nelson (1932), by most investigators. These media take advantage of excretions of V factor by normally occurring contaminants or cross-streaks with pure cultures of Staphylococcus epidermidis and Pseudontonas aeruginosa. Recently Page (1962) found that H. gallinarum could be grown on the nutrients of tryptose agar when supplemented with tryptic digest of casein, NaCl, glucose and NADH (reduced form of NAD); tryptose broth required chicken serum in the place of casein digest. Serological comparisons among H. gallinarum isolates were made by Page (1962) and Kato and Tsubahara (1962). Yamamoto and Sommersett (1964) detected agglutinins, in chickens inoculated with H. gallinarum, 7 to 14 days after onset of clinical signs. They also isolated H. gallinarum from chickens which showed no clinical

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Identification of Haemophilus Gallinarum in Artificially Infected Chickens