Evaluation of the Athens-Canadian Randombred Population

Evaluation of the Athens-Canadian Randombred Population 1. TIME TRENDS AT TWO LOCATIONS1 H. L. MARKS 2 AND P. B. SIEGEL3 United States Department of Agriculture and Virginia Polytechnic Institute and State University (Received for publication February 22, 1971)

HE importance of control populations for separating genetic and environmental effects has been well documented (Dickerson, 19SS; Gowe and Johnson, 1956; King et al., 1959; Goodwin et al., 1960). Although considerable information is available regarding egg-type control populations (King, 1961; King et al., 1963; Clayton and Robertson, 1966; Kinney et al., 1968), only limited data are available for meat-type controls (Jaap et al., 1962; Merritt and Gowe, 1962; Merritt, 1966, 1968). Hess (1962) described the development and maintenance of the Athens Canadian (A.C.) randombred meat-type population of chickens. Since this population is widely used it would be valuable to have information on production characteristics and possible time trends of various quantitative traits. Since time trends in control populations can be influenced by genetic (natural selection, genetic drift, inbreeding) and directional environmental changes, evalua1 This investigation was conducted as part of the Southern Regional Poultry Breeding Project (S-68), a cooperative study involving agricultural experiment stations in the Southern Region and supported in part by Regional Research Funds and Poultry Research Branch Funds of the United States Department of Agriculture. University of Georgia, College of Agriculture Experiment Stations, Journal Paper Number 631, College Station, Athens. 2 Southern Regional Poultry Breeding Project, A.S.R., A.R.S., U.S.D.A., Athens, Georgia 30601. 3 Department of Poultry Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061.

tion of these trends may not provide a critical measure of the reliability of these populations. Nevertheless, evaluation of the same population at two locations under different but relatively uniform management systems within locations should provide some evidence regarding the usefulness of this population. The A.C. population is segregating at the rose and pea loci. Data on comb phenotypes could provide evidence of genetic stability. Reported here are means for comb phenotypes and several quantitative traits in the A.C. population at two locations. METHODS AND MATERIALS

The A.C. population, whose base was the Ottawa Meat Control Strain (O.C.), has been maintained at the Southern Regional Poultry Genetics Laboratory since 1958. An effort was made to retain breeders from the same families available to the Canadian workers so that the A.C. population would be as similar as possible to the O.C. strain. The population was reproduced annually in two to three hatches. Pedigree records were maintained with five to seven females assigned for mating to each of 60 males. Assignments were made at random with the restriction that full- and half-sib matings were avoided. The males in all breeding pens were descendants of the original sires because each year sires were replaced by surviving sons. Efforts were made to have incubation, brooding, rearing, housing, rations, disease control, and other management aspects consistent over generations.

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T

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H. L. MARKS AND P. B. SIEGEL

hen-day egg production was determined from age at first egg to January 1. Egg traits were based on the mean of eggs laid during the 35th week after hatching. RESULTS AND DISCUSSION

Phenotypic Means of Economic Traits: Information on juvenile body weight is of particular importance since many studies utilizing this population are concerned with growth rate. Mean eight-week body weights, by year and sex, for chickens maintained at the Regional Lab. and at Virginia are presented in Table 1. Although efforts were made to keep environments within a location constant, there was considerable variation across years at both locations. Body weights of birds maintained at the Regional Lab. were consistently heavier than those reared in Virginia. This difference ranged from 22 to 226 g. for males and 31 to 200 g. for females in 1965 and 1968, respectively. Such variation may be expected because there was no attempt to standardize environments between the two locations. The consistently heavier weights at the Regional Lab. however, were probably due to differences in feed formulations. The ration fed at Virginia consisted of 20.8 percent crude protein and 816 kcal. of productive energy while that at the ReTABLE 1.—Mean eight-week body weight (g.) by year, sex, and location Location Year

1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 Regression

Regional Lab.

Virginia

Males

Females

Males

1000 1030 1027 1095 1063 1058 1062 998

834 880 869 929 886 894 883 849

949 903 949 999 920 878 948 976 913 971 876 856 -4.6+3.6

t t

1102 1022 2.5 + 3.4

t D a t a not available.

t

t

927 884 3.0+2.7

Females 759 753 795 835 772 724 791 818 768 820 727 709 2.6 + 3 . 5

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Chicks were maintained in a conventional brooder house with sexes separate for ten weeks and then moved to range shelters where sexes were intermingled until housing at 18 to 20 weeks of age. Additional management details were given by Hess (1962). This paper is based on data collected at two locations, the Southern Regional Poultry Genetics Laboratory (Regional Lab.) in Georgia and Virginia Polytechnic Institute and State University, during the 11 years from 1958 to 1968. At the Regional Lab. body weights and comb types were obtained at eight weeks of age for all years except 1966 and 1967. Egg data were based on a sample of at least ISO females maintained in individual cages. Egg production was for ten 28-day periods and egg weights were obtained at 300 days of age. Sexual maturity was measured as the age at first egg, while adult body weights were obtained at 300 and 400 days of age. Each year from 19S9 to 1968, 45 dozen unpedigreed eggs from the A.C. population were sent from the Regional Lab. to Virginia. Virginia's 1958 sample came from the parent O.C. strain. Chicks were hatched on the first Tuesday in March and efforts were made to have management and feed formulation consistent over years. Sexes were intermingled in floor pens with hot air brooding from hatching until eight to nine weeks of age. Thereafter, sexes were maintained in separate flocks. Details of how the traits shown in Table 2 were measured have been given by Siegel (1962, 1963). Briefly, body weights of all chicks were obtained at four and eight weeks, and for females only at 168 and 266 days of age. Also, breast angle and feather cover on the back area were measured on all chicks at eight weeks of age. Semen traits were based on the mean of three artificial ejaculates obtained from a random sample of males at 29-31 weeks of age. Percentage

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TIME TRENDS AND LOCATIONS TABLE 2.—Means and regression coefficients by sex for traits measured at the Virginia station Year

Trait

Sex 1958

1959

1960

1961

1962

1963

1964

1966

1967

1968

M F

321 277

298 260

299 267

343 306

328 274

303 265

355 309

349 313

337 301

355 313

302 272

2.6 + 2.1 3 . 1 ± 1.9

b

8-Wk. Breast Angle (degrees)

M F

55.1 51.6

53.5 51.3

55.9 54.5

57.1 55.7

54.1 53.9

53.2 51.0

53.8 51.5

55.9 53.5

55.3 54.0

54.3 52.9

54.8 52.6

-0.03+.12 0.03+.15

8-Wk. Feathering (% back)

M F

70 86

79 90

82 93

74 86

83 89

78 92

87 96

87 95

79 93

67 89

77 91

0.07±.64 0.42+.30

168-day Body W t . (g.) 266-day Body Wt. (g.) Semen Vol. (cc.) Semen Motility _ Semen Cone, (million/mm. 3 ) Sexual M a t u r i t y (days) Egg Prod. (% hen-day) Egg Weight (g.) Haugh Units Specific Gravity

F F M M M F F F F F

2495 2222 2359 2359 . 2313 2268 2268 2041 2137 2449 2137 -20+12 2858 2676 2767 2767 2722 2540 2449 2313 2585 2630 2672 -26+13 .32 .68 .48 .41 .34 .37 .22 .21 .32 .22 .28 -0.03+.01 3.4 3.8 4.2 4.2 3.9 4.4 3.9 3.8 3.8 4.3 3.5 0.01+.03 4.75 5.85 6.70 8.15 7.10 7.10 7.40 9.30 4.00 5.05 6.50 0.00+.16 177 174 167 165 168 170 167 167 170 170 174 — 0 . 1 7 + .37 61.1 64.9 64.3 66.1 60.4 54.8 53.2 45.5 50.1 56.4 49.9 -1.6+.4" 52.3 51.6 51.1 53.2 52.5 51.4 51.6 49.9 51.2 49.6 49.4 -0.27+.08" 85.3 83.6 83.2 81.4 79.2 74.2 78.5 80.5 81.5 81.6 82.3 - 0 . 2 8 + .28 1.081 1.088 1.088 1.085 1.088 1.087 1.089 1.082 1.083 1.088 1.084 - 0 . 0 0 0 0 + . 0 0 0 3

'P<.01.

gional Lab. consisted of 24.1 percent protein and 1006 kcal. of productive energy. At the Regional Lab. the regressions of mean body weight at eight weeks of age on years were 2.5 and 3.0 g. for males and females, respectively (Table 1). Comparable values of —4.6 and 2.6 g. were observed at Virginia. None of the regression coefficients were significant. Presented in Table 2 are the means and regression coefficients for various traits measured in the A.C. population reared at the Virginia station. Although there were fluctuations across years for some of these traits, the only significant regression coefficients were for percentage egg production and egg weight. Both egg production and egg weight declined over years. Regression coefficients for four-week body weight, eight-week breast angle, eight-week feathering, semen volume, semen motility, semen concentration, age at first egg, and specific gravity of eggs were extremely small indicating little or no change in these traits across years. While not significant, a rather large reduction in body weights at 168 and 266 days of age occurred over the elevenyear period. Means and regression coefficients for various adult measurements obtained at the

Regional Lab. are shown in Table 3. Average ages at first egg ranged from 164 to 177 days and were in close agreement with those observed in Virginia (Table 2). The trend in mortality was nonsignificant. Egg weights (300-day) were approximately four to six grams larger than the 245-day egg weights observed at Virginia. The negative trend (b = — . l l ) in egg weight was in the same direction as the Virginia data ( b = —.27), but was not significant. A substantial reduction in both 300- and 400-day body weights was observed for females maintained at the Regional Lab. (Table 3). The negative regressions of 52 and 37 g. for 300- and 400-day body weights, respectively, were significant (P < .01). Although there was a negative trend for 168- and 266-day body weights of A.C. females maintained in Virginia (Table 2), the regressions obtained there were of a lower magnitude and not significant. Egg production (total egg number and percentage survivor's production) of birds at the Regional Lab. increased significantly over the ten-yeear period (Table 3). These data are surprising, since they are in direct contrast to the response of egg production observed in Virginia. It is important to remember, however, that egg production at

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1965

4-Wk. Body Wt. (g.)

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H. L. MARKS AND P. B. SIEGEL TABLE 3.—Means and regression coefficients for trails measured at the Regional Lab. Years Trait 1959

1961

1962

1963

1964

1965

1966

1967

1968

172 166 165 170 177 167 166 165 164 3232 3216 3234 3068 2938 2825 2911 2833 2965 3283 3201 3293 3044 3058 3023 3051 2885 3128 56.7 59.5 58.7 57.5 59.3 57.1 57.5 59.6 56.3 56.9 162 160 177 146 123 124 114 124 122 130 174

t 3327

b .50+.48 - 5 2 + 13** - 3 7 + 10** -.11+.14 5.5+1.6**

52.6 7.1 81.6

47.3 11.0 63.3

48.4 18.1 75.8

43.9 10.0 83.2

49.2 10.8 84.0

47.9 10.2 77.3

57.3 9.0 83.9

72.8 8.0 81.0

63.9 18.9 86.9

68.6 11.3 83.6

2.6+.8** .24+.45 1.2+.6

72.5

66.1

64.5

71.4

70.1

60.2

73.6

73.0

78.3

75.9

.94+.55

88.8

81.6

85.2

85.8

83.5

77.9

87.8

90.1

90.1

91.0

.63+.44

** P < . 0 1 . t Data not available 1 Per bird housed

the Virginia station was measured from age of first egg to January 1 (approximately four months) while this trait was measured over a ten-month period at the Regional Lab. Since birds tested in Virginia were maintained in floor pens while those at the Regional Lab. were kept in individual cages, behavior patterns may also have had some influence (Biswas and Craig, 1970). A possible explanation for the increase in egg production at the Regional Lab. could be the change in farm managers in 1965. Similar changes in adult body weight and egg production of a second randombred population (Athens Randombred) maintained at the Regional Lab. suggests that these responses were due to environmental rather than genetic influences (Marks, 1971). With the exception of a low 63.3 percent in 1960, percentage fertility remained fairly constant indicating that the reproductive fitness of the A.C. population has not changed over the ten-year period. Regression coefficients of 1.2, .94, and .63 were observed for percentage fertility, percentage hatch of total eggs and percentage hatch of fertile eggs, respectively (Table 3).

The argument for directional changes in the environment causing time trends in the phenotypic means of some traits (adult body weight, egg production and egg weight) appears reasonable in view of a similar response of another control population. It is, however, possible that these changes could have been the result of genetic changes or due to a combination of genetic and environmental influences. Comb Phenotype Frequencies: Alleles at the pea and rose loci determine the single, rose, pea, and walnut phenotypes (Bateson and Punnett, 1906). A.C. chickens were classified for comb types at the Regional Lab. for 9 of the past 11 years. To evaluate the consistency of these phenotypes over time, their frequency was regressed on years (Table 4). There were considerable yearly fluctuations in the frequency of comb phenotypes. Regression coefficients were negative for single, pea, and walnut frequencies, while a positive trend was observed for the frequency of rose comb. Four different persons classified comb phenotypes during the eleven-year period covered by this report. Although there may have been observer differences and inaccu-

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Sexual Maturity (days) 300-day Body Wt. (g.) 400-day Body Wt. (g.) Egg Weight (g.) Total Egg Number 1 Egg Production (% Survivor) Mortality (%) Fertility (%) Hatchability (%) (Total Eggs) Hatchability (%) (Fertile Eggs)

1960

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TIME TRENDS AND LOCATIONS TABLE 5. Hevitability estimates of eight-week body weight {Regional Lab.)

TABLE 4.—Frequency of comb phenotype by year {Regional Lab.) Year

Pea

35.1 37.3 30.9 31.5 34.4 30.6 34.9

19.1 18.8 25.4 21.7 21.6 19.1 18.8

t t

t

t

31.1 18.4 35.4 20.2 - . 1 2 + . 2 7 •- . 1 8 + . 2 4

t Data not available

Rose

Heritability

Walnut

20.7 18.2 14.5 28.8 27.7 30.3 32.7

25.2 25.7 29.2 18.1 16.3 20.2 13.6

t

t

+ t 28.4 22.2 28.9 15.7 1.21 + .51 - . 9 0 + . 4 7

Year 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 X

4S

4D

.32 .25 .36 .35 .19 .23 .20

.43 .57 .40 .43 .38 .37 .59

t t

.22 .27 - . 0 1 + .01

t t

.52 .46 .01+.01

Regression racies in classifying comb types at eight weeks, it appears that the frequency of rose f Data not available. comb has increased in the A.C. population mainly at the expense of the walnut phenotype. Comb phenotypes were classified at ratios at the pea and rose loci. The first inhatching in 1968, 1969, and 1970 at the dication of this was by Bateson and PunVirginia station. All classifications were by nett (1906) from matings of RrPp and the same individual. Percentage frequencies rrpp genotypes. Examples of subsequent in 1968 were 30.9 single, 14.7 pea, 30.9 publications showing abnormal ratios were rose, and 23.S walnut. Percentages in 1969 by Petroff (1929) at the pea locus and were 36.2 single, 17.2 pea, 31.7 rose, and Merat (1962, 1967) at the rose locus. 14.9 walnut. Percentages in 1970 were 29.S single, 22.4 pea, 29.S rose, and 15.0 walnut. Heritabilities: Heritability estimates for The data for 1968 were significantly differ- eight-week body weight of birds mainent from those in 1970 with the frequency tained at the Regional Lab. are shown in of pea comb change at the expense of the Table 5. Estimates, based on sire compowalnut phenotype. These values were con- nents of variance (4S), ranged from .19 to sistent with 1968-69 comb frequencies ob- .36 with a mean of .27. Estimates based on tained at the Regional Lab. (Table 4). dam component of variance (4D) were It is interesting to speculate about consistently higher and ranged from .37 to changes in comb frequencies in this popula- .59, with a mean of .46. The higher values tion. Although marker genes may be used would be expected if maternal and/or domto measure genetic drift in randombred inance influences on juvenile body weight populations, there is confounding when were important. The regression of heritabilthese genes are involved with fitness traits. ities, based on sire and dam components of Cook and Siegel (1970) in a preliminary variance, on years were —.01 and .01, restudy observed a decrease in the frequency spectively, indicating a lack of significant of the R allele and an increase in the fre- time trends. Heritability estimates (sire quency of the P allele in a line selected for component) of .40 for both 42- and 63-day a low number of matings. The base of this body weights were obtained for the parent line was the first generation A.C. chicks re- O.C. population by Merritt (1966). Esticeived at the Virginia station. Several stud- mates from dam component of variance ies have also shown abnormal segregation were .72 and .62 for 42- and 63-day body

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1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 gression

Single

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H. L. MARKS AND P. B. SIEGEL

weights, respectively. Since heritabilities are a ratio, differences in environmental variances could explain the lack of agreement between the estimates obtained from populations with the same genetic base. SUMMARY

ACKNOWLEDGMENT

The authors acknowledge the efforts of Dr. C. W. Hess, Dr. R. E. Cook and Dr. L. D. Tindell for the maintenance of this population and collection of data during various periods covered by this report. REFERENCES Bateson, W., and R. C. Punnett, 1906. Comb characteristics. Royal Soc. Lond., Evol. Comm. Rpts. 3 : 11-16. Biswas, D. K., and J. V. Craig, 1970. Genotypeenvironment interactions in chickens selected

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Data obtained from the Athens-Canadian Randombred population maintained at the Southern Regional Poultry Genetics Laboratory and from a sample reared at Virginia Polytechnic Institute and State University were analyzed to obtain information on production characteristics and assess time trends of traits across generation. Regressions of most quantitative traits on generations were small and not significant. The exceptions were adult body weights (negative) and egg production (positive) at the Regional Lab., and negative regressions for egg production and egg weight at Virginia. There was evidence of changes in comb phenotypes. Since the pea and rose loci are associated with fitness components, these qualitative markers are not appropriate markers for evaluating genetic stability in randombred control populations. Mean heritability estimates for eightweek body weight of .27 and .46 were obtained from sire and dam components of variance, respectively. The regressions of heritabilities on years were —.01 and .01, respectively, indicating a lack of significant time trends.

for high and low social dominance. Poultry Sci. 49: 681-692. Clayton, G. A., and A. Robertson, 1966. Genetics of changes in economic traits during the laying year. Brit. Poultry Sci. 7: 143-151. Cook, W. T., and P. B. Siegel, 1970. Relationship of rose and pea comb loci to selection for mating ability. Poultry Sci. 49 : 1376. Dickerson, G. E., 1955. Genetic slippage in response to selection for multiple objectives. Cold Springs Harbor Sympos. on Quant. Biol. 20: 213-224. Goodwin, K., G. E. Dickerson and W. F. Lamoreaux, 1960. An experimental design for separating genetic and environmental changes in animal populations under selection. Biometrical Genetics, edited by O. Kempthorne, pp. 117138. Gowe, R. S., and A. S. Johnson, 1956. The performance of a control strain of S. C. White Leghorn stock over four generations on test at several locations. Poultry Sci. 35: 1146. Hess, C. W., 1962. Randombred populations of the Southern Regional Poultry Breeding Project. World's Poultry Sci. J. 18: 147-152. Jaap, R. G., J. H. Smith and B. L. Goodman, 1962. A genetic analysis of growth and egg production in meat-type chickens. Poultry Sci. 4 1 : 1439-1446. King, S. C , 1961. Inheritance of economic traits in the Regional Cornell control population. Poultry Sci. 40: 975-986. King, S. C , J. R. Carson and D. P. Doolittle, 1959. The Connecticut and Cornell randombred populations of chickens. World's Poultry Sci. J. 15: 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. Gent. Res. 4 : 290-304. Kinney, T. B., Jr., P. C. Lowe, B. B. Bohren and S. P. Wilson, 1968. Genetic and phenotypic variation in randombred White Leghorn controls over several generations. Poultry Sci. 47: 113123. Marks, H. L., 1971. Evaluation of the Athens Randombred population. Poultry Sci. 50: 15051507. Merat, P., 1962. Segregations anormale pour les alleles Crete simple et Crete en rose chez la poule. An. Biol. Anim. Bioch. Biophys. 2: 109-117. Merat, P., 1967. Contribution a l'etude de la voleur selective associee a quelques genes chez la poule domestique. An. Biol. Anim. Bioch. Biophys. 7: 79-104. Merritt, E. S., 1966. Estimates by sex of genetic

TIME TRENDS AND LOCATIONS parameters for body weight and skeletal dimensions in a randombred strain of meat type fowl. Poultry Sci. 45: 118-125. Merritt, E. S., 1968. Genetic parameter estimates for growth and reproductive traits in a randombred control strain of meat type fowl. Poultry Sci. 47 : 190-199. Merrit, E. S., and R. S. Gowe, 1962. Development and genetic properties of a control strain of meat-type fowl. Xllth World's Poultry Cong. Sect. Papers: 66-70.

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Petroff, S. G., 1929. A comb-inhibiting gene: An inhibitor of the development of the pea and walnut combs in domestic fowl. J. Hered. 20: 540. Siegel, P. B., 1962. Selection for body weight at eight weeks of age. 1. Short term response and heritabilities. Poultry Sci. 4 1 : 954-962. Siegel, P. B., 1963. Selection for breast angle at eight weeks of age. 2. Correlated responses of feathering, body weight and reproductive characteristics. Poultry Sci. 42: 437-449.

W. J. NEVILLE, J. W. MACPHEESON AND B. REINHART 1 Departments of Animal Science and Poultry Science1, University of Guelph, Guelph, Ontario, Canada (Received for publication February 22, 1971)

A

RTIFICIAL insemination of chickens • with liquid semen has been widely practiced for a number of years, but its commercial application has been hindered by the fact that chicken spermatozoa do not retain their fertilizing capacity when stored in vitro for any appreciable length of time. Early experiments demonstrated that chicken spermatozoa were highly active in concentrations of glycerol as high as 20% by volume at room temperature, but samples of semen containing more than 2% glycerol had lost their fertilizing capacity (Smith, 1961). Polge (1951) reported that chicken spermatozoa which had been diluted to contain 15% glycerol and which had been stored at - 79°C. for \ to 1 hour had normal fertilizing capacity after thawing, provided that the glycerol had been removed by dialysis prior to insemination. However, the potential fertilizing capacity and spermatozoan motility declined markedly in the weeks following freezing. Shaffner (1964) also demonstrated that fowl spermatozoa could be successfully frozen in the presence of glycerol, resulting in satisfactory fertility levels if the glycerol were removed by dialysis prior to insemination.

The objectives of the present study were to investigate the effect of various levels of glycerol on fertility and hatchability of chicken eggs and to determine the carryover effect of glycerol in the female tract. EXPERIMENTAL PROCEDURES Trial 1.—24 White Leghorn hens (approximately 14 months of age) from a strain developed at the Poultry Science Department, were allocated in groups of 6 to a control and 3 treatments of 3, 6 or 9% glycerol by volume of the semen extender. The chickens were inseminated at the beginning of each week for 3 consecutive weeks with 0.2 ml. of extended semen containing the desired concentration of glycerol; 290 eggs were incubated. Seven days after the last glycerol treatment, the chickens were each inseminated with 0.2 of extended semen containing no glycerol to determine the carry-over effect of glycerol in the female; 105 eggs were incubated. Trial 2.—32 White Leghorn hens (approximately 14 months of age) from the same strain and flock as in Trial 1, were allocated in groups of 8 to a control and 3 treatments of 1, 2 or 3 % glycerol by vol-

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The Contraceptive Action of Glycerol in Chickens