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Evaluation of Certain Reproductive Traits in Lines of Chickens Selected for Mating Ability
ERYTHROCYTE
1201
Soliman, K. F. A., and T. M. Huston, 1972. Effect of dietary protein and fat on the hematocrit and plasma cholesterol of chickens at different environmental temperature. Poultry Sci. (In press). Stahl, P., G. W. Pipes and C. W. Turner, 1961. Time required for low temperature to influence thyroid secretion rate in fowls. Poultry Sci. 40: 646-650. Turner, C. D., 1966. General Endocrinology. 4th ed. W. B. Saunders Co., Phil. Lond. p. 579. Waldmann, T. A., S. M. Weissman and E. H. Levin, 1962. Effect of thyroid administration of erythropoiesis in the dog. J. Lab. Clin. Med. 59: 926-931. Washburn, K. W., and T. M. Huston, 1968. Effect of environmental temperature on iron deficiency anemia in Athens-Canadian Randombred. Poultry Sci. 47: 1532-1535.
Evaluation of Certain Reproductive Traits in Lines of Chickens Selected for Mating Ability W. T. C O O K 1 AND P . B.
SIEGEL
Department of Poultry Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 (Received for publication October 25, 1971) ABSTRACT An evaluation was made of age at sexual maturity, egg production, egg weight, fertility and hatchability in lines of chickens divergently selected for 10 to 12 generations for cumulative number of completed matings of males. Males of the low mating line matured at earlier ages than those of the unselected control and high mating lines. The four comb phenotypes involving the rose and the pea loci did not influence age at sexual maturity in males. In females no differences were found among lines for age at sexual maturity, hen-day egg production, and egg weights. The selected lines were not different for percentage fertility and hatchability of fertile eggs. POULTRY SCIENCE 51: 1201-1206, 1972
" D I D I R E C T I O N A L selection for com•*-* ponents of sexual behavior results in lines of chickens in which males have different mating propensities (Wood-Gush, 1960; Tindell and Arze, 1965). Siegel (1965, 1972) using the Athens-Canadian (AC) R a n d o m b r e d population as a base, established distinct high and low mating lines by selecting for number of complete
matings. T h e AC randombreds exhibit segregation of alleles at the rose and pea loci (Hess, 1962; Merritt and Gowe, 1962). Reported here are the effects of Siegel's continuous selection for high and low male mating behavior on certain reproductive traits, and the effects of comb phenotypes on one of those traits. MATERIALS AND METHODS
1 Present address, Research Headquarters, HyLine Poultry Farm, Johnston, Iowa 50131.
General. T h e d a t a used in this paper are from the 5 1 0 , S H and Si 2 generations
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 17, 2015
Johnson, P. M., 1955. Hematocrit values for the chick embryos at various ages. Amer. J. Physiol. 180:361-362. McClellan, J. E., C. Donegan, O. A. Thorup and B. S. Leavell, 1958. Survival time of the erythrocyte in myxedema and hyperthyroidism. J. Lab. Clin. Med. 51: 91-96. Moye, R. J., Jr., K. W. Washburn and T. M. Huston, 1970. Effect of environmental temperature on erythrocyte number and size. Poultry Sci. 49: 1683-1686. Rodnan, G. P., F. G. Ebaugh, Jr. and M. R. S. Fox, 1957. The life span of the red blood cell and the red blood cell volume in the chicken, pigeon and duck as estimated by the use of Na251Cr04. Blood, 12: 355-366. Shemin, D., 1948. The biosynthesis of prophyrins. Cold Spring Harbor Symp. Quant. Biol. 13: 185-192.
SURVIVAL
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W.
T.
COOK AND P.
Sexual maturity of males. T h e Sio generation cockerels were produced by approximately 30 randomly selected dams from each line. Within lines, 10 to 12 randomly selected sires were rotated among pens of dams to ensure t h a t all comb phenotypes were present among the progeny. Chicks were sexed a t one day of age and lines were intermingled in unisexual flocks. At 56 days of age, 20 males per line (5 per comb phenotype) were randomly selected and randomly assigned to individual cages. Commencing at 63 days of age, males were artificially stimulated thrice weekly until 133 days of age, and weekly thereafter until 150 days of age. Sexual m a t u r i t y was considered as the age at which the second of two consecutive semen samples were obtained. This procedure was satisfactory based on microscopic examination of the semen (Blom, 1950). Aspermatozoic males were assigned 150 days as their age at maturity. D a t a for sexual m a t u r i t y of the Sio generation males were analyzed factorially for a completely randomized design
SIEGEL
(Snedecor and Cochran, 1967, p. 346). The fixed effect model for lines, comb types, and line X comb type interaction used was: Y i j k = n + A; + Bj + A B ( i j ) + e i i k where, Y;jk is the k t h replication of the i t h line and the j t h comb type. Males of the S n and S12 generations were randomly chosen from the progeny of the parents selected to reproduce the lines. Individuals were reared in bisexual flocks until 56 days of age and then placed in individual cages. Based on d a t a from the Sio generation, comb phenotypes were not considered in either of these generations. Procedures for measuring sexual m a t u r i t y were the same as those used in the Sio generation except t h a t stimulations began at 56 days instead of 63 days of age. Comparisons among lines within the S n and S12 generations were by a one way analysis of variance. Means were ranked by D u n c a n ' s multiple range test (Kramer, 1956). Reproductive traits of females. H . M . and L . M . line females of the Sio, S n and the S12 generations were progeny of the parents selected to reproduce the lines. Pullets were reared in heterosexual flocks until placed in unisexual flocks at 56 days of age. T h e y were trapnested 3 days per week through 300 days of age. Comparisons among lines for female sexual maturity and hen-day egg production were tested by a one way analysis of variance, and D u n c a n ' s multiple range test was used to rank the means (Kramer, 1956). Weights of eggs laid at 241, 242, and 243 days of age were obtained in the S12 generation. Each egg was weighed to the nearest g. the morning after it was laid. Egg weights were subjected to hierarchal analysis for differences among lines and among females within lines. Snedecor and Cochran (1967, p. 291) present an ap-
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 17, 2015
of the high mating (H.M.) and the low mating (L.M.) lines developed by Siegel (1965, 1972) from the AC randombred population. T h e base population for the selected lines consisted of the AC randombreds in which all 4 of the classic comb phenotypes for the rose and the pea loci were present (rose, pea, walnut and single). T h e selection criterion was the cumulative number of completed matings ( C N C M ) b y a male in 8, tenminute observation periods. Details of selection and general management procedures have been given (Siegel, 1965; 1972). Briefly, chicks were hatched in M a r c h of each year, and hot-air brooded in floor pens with wood shavings. Food and water were given ad libitum, and there was no artificial lighting after 14 days of age.
B.
EVALUATION OF REPRODUCTION TRAITS
propriate analysis for a mixed model, since lines were considered fixed and females within lines were random. The model used was: Y i i k = fi + Ai + Bij + eijk
Multiple male matings were made in the Sn generation. T h e y involved all combinations of the 3 lines. Twelve females per line were randomly chosen and randomly assigned to each male line. Eggs t h a t did not hatch were broken out, and macroscopic determinations were made for fertility. Percentages were converted to arc sines and analyzed by factorial plan with a fixed effect model: Y i i k = ji + Si + Dj + S D ( i i ) + eij k where, Yij k is the k t h observation of the i t h sire line mated to the j t h d a m line. D u e to disproportionality, analysis was made by the method of weighted squares of means (Bancroft, 1968; sec 1.8).
RESULTS AND DISCUSSION
Sexual maturity—males. Means and standard errors for sexual m a t u r i t y of males by lines and comb types are presented in Table 1 for the Sio generation. The comb type X line interaction was not significant showing t h a t the response among comb types was similar for all lines. No differences were found among comb types for age at male sexual maturity. There were significant differences among lines with L . M . males maturing earlier than H . M . and AC males. T h e latter two lines were not significantly different from each other. T h e relationship observed among lines in the Sio generation was confirmed in the S n and S12 generations where males from the L . M . line again matured at significantly earlier ages than those from the H . M . and AC lines (Table 2). McCollom (1967), using only single comb phenotypes, found t h a t males from the L . M . line had combs comparable to or larger than those in the H . M . and AC lines. His results, and ours, suggest t h a t there are differences in the pituitary-gonadal axis of these lines. T h e results of this study are consistent with and extend those of Tindell and Arze (1965) who observed t h a t S2 generation males in lines selected for low mating matured earlier than those selected for high mating. Their lines came from the same genetic base as ours. Since the difference between the AC randombred TABLE 1.—Means and standard errors for age (days) at sexual maturity of Sio males by lines and comb phenotypes Comb type Rose Pea Walnut Single Pooled
Lines H.M. 101±13 96+ 5 100+ 7 97 ±10 b 98 ± 4
AC
L.M.
Pooled
97 + 21 112+11 110+ 6 99+ 9 105+ 3 b
83±5 92±7 85 + 5 79 + 3a 85±3
94+8" 100+ 4 a 98 + 4" 92 + 4"
Any two marginal row or column means with the same superscript are not different (P<.05),
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where, A ; is the effect of the i t h line and Bij is the random variable for the j t h females within the i t h line. Fertility and hatchability. Incubation data for the selected lines were based on weekly artificial inseminations, and eggs were incubated in 3 bi-weekly hatches. Ten sires, selected for C N C M , were each mated with 3 to 5 randomly chosen females to reproduce each selected line. Presented here are the percentage fertility and hatchability of fertile eggs for t h e H . M . a n d L . M . l i nes for the S io, S ii, and S12 parental generations. Fertility was determined by candling at 16 days of incubation. Percentages were obtained for each individual mating and converted to arc sines as suggested b y Mosteller and Youtz (1961) for individuals with less than 50 observations. Comparable fertility and hatchability d a t a were not available for the AC randombreds because chicks were hatched from unpedigreed eggs received from the parent population.
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W. T. COOK AND P. B. SIEGEL TABLE 2.—Means and standard errors for age at sexual maturity of males and females by line and generations n
Sex
x + se (days)
Gen H.M.
AC
L.M.
H.M.
L.M.
AC b
b
105 ± 3 107 ± 3 b 100 ± 5 b
85+3" 92 ± 3 " 85 ± 3 "
174±2" 170 + 2" 40 91 79 5io 188 ± 3 b 179 + 2" 52 59 110 186 ±4" 177 + 2" 73 64 106 Sn Sl2 Any two means in a row with the same superscript are not different (P<0.5).
175 + 5" 175 ± 3 " 180 + 4"
Male
Sio Sn Sl2
20 15 20
20 15 20
Female
98 + 4 103+4 b 98±4b
for social dominance. Sexes in our study were maintained differently; males were placed in individual cages prior to the formation of stable peck orders while females were maintained in flocks. Therefore, the different ranking of the lines for age at sexual maturity of males and females may reflect an interaction of sex by method of rearing. The second possibility is that, although age at sexual maturity of males and females depends on an association of hornomes and threshold levels, the components of the relationship in the sexes are different (Nalbandov, 1964). Thus, a selection criterion that modifies the hormonal-threshold relationship for both the primary and correlated traits in one sex may not necessarily alter the correlated responses of reproductive traits in the opposite sex. Therefore, selection for CNCM in males may have caused a correlated response in age at first spermatozoa production without affecting age at first egg. Related traits. Eggs were weighed during a 3-day period in the S12 generation for 43 H.M., 40 AC and 32 L.M. females. Mean egg weights were 51.3, 49.4 and 49.1 g. for H.M., AC and L.M. lines, respectively. Differences among lines and among females within lines were not significant. Egg production of the H.M. and L.M. lines was significantly higher than for the AC females in the Sn, but not the
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population and the L.M. line was also significant, it may be hypothesized that the difference among lines is due to a change in age at maturity for L.M. line males and not for the AC and H.M. lines. Sexual maturity—females. Differences among lines were not significant in the Sio and S12 generations, whereas in the Sn generation the control pullets matured significantly later than those of the selected lines (Table 2). Only once during the first 9 generations of selection was there a significant difference between selected lines for age at first egg. The lack of consistent differences between lines suggests that bidirectional selection for CNCM had little influence on the age of sexual maturity of females. The consistency of differences among lines for age at sexual maturity of males contrasts with the absence of differences among lines for age at first egg. Two hypotheses may be proposed to explain the inconsistency between sexes. First, there is the possibility of differential effects of social behavior for individually caged males and flock-reared females. Lowry et al. (1956) and Biswas and Craig (1970) observed that pullets maintained in cages matured earlier than those kept in floor flocks. Further, Biswas and Craig observed a significant interaction for age at first egg between rearing methods and lines that had been divergently selected
20 14 20
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EVALUATION OF REPRODUCTION TRAITS TABLE 3.—Means and standard errors for percentage hen-day egg production by lines arid generations
TABLE 5.—Means and standard errors for percentage fertility in natural matings Sire line
n
x±se
Dam line
Gen H.M. Sio S« Su
AC
79 110 106
91 59 64
L.M.
H.M.
AC
L.M.
45 52 73
47 + 2" 62±lb 59+2a
4 9 ± 3 aa
48+3a 60+3b 59 ± 2 "
53±3 60+3"
Any two means in a row with the same superscript are not different (P<.05).
H.M. AC L.M. Pooled
H.M.
AC
L.M.
Pooled
95 + 4 92 + 1 97 + 2 95 + 2"
98±1 98±1 95±3 97±la
98±1 98±3 99 + 1 98±la
97 + 2a 96 + 2a 97 + 2a
Any two marginal row or column means with the same superscript are not different (P<.05).
TABLE 4.—Means and standard errors for percentage fertility and hatch of fertile eggs by lines and generations
1
x + se 1
n
Parental gen.
H.M.
L.M.
H.M.
L.M.
SlO Sn Si.
27 39 43
24 32 38
8 7 ± 3 ba 81±3a 74±4
70±5a 81 + 4aa 74+4
Sio Su Su
27 38 41
21 31 38
74 + 5" 69 + 4 a 58 + 5"
72+6a 77 + 3" 64+4a
Matings were produced by artificial insemination. Any two means in a row with the same superscript are not different (P<.05).
and hatchability. The fertility data suggest that the lower mating frequency of the L.M. line in comparison to the H.M. line may be compensated for by the superior semen quality of the former (Siegel, 1965, 1972). Cook (1971), using these same lines noted that raising juvenile males with or without females had little influence on the number of completed matings at 32-34 weeks of age. The results of that study and this one suggest that percentage fertility and hatchability of breeding flocks would not be altered by rearing sexes separately or intermingled and by the behavioral modifications made to date through selection for CNCM. REFERENCES Bancroft, T. A., 1968. Topics in Intermediate Statistical Methods. Iowa State Univ. Press, Ames. Biswas, D. K., and J. V. Craig, 1970. Genotype-environment interactions in chickens selected for high and low social dominance. Poultry Sci. 49: 681-692. Blom, E., 1950. A one minute live-dead sperm stain by means of eosin nigrosin. Fertility Sterility, 1: 176-177. Cook, W. T., 1971. Quantitative and qualitative genetic analyses of mating behavior in chickens. Ph.D. Dissertation, Vir. Poly. Instit. & State Univ. Hess, C. W., 1962. Randombred populations of the Southern Regional Poultry Breeding Project. World's Poultry Sci. J. 18: 147-152. Kramer, C. Y., 1956. Extension of multiple range tests to group means with unequal class numbers of replications. Biometrics, 12: 307-310. Lowry, D. C , I. M. Lerner and L. W. Taylor, 1956.
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Sio and S12 generations (Table 3). Divergent selection for mating ability of males thus had relatively minor effects on these two traits. Differences between the H.M. and L.M. lines for percentage fertility in matings used to reproduce the lines were significant in the Sio but not in the Sn and S12 generations (Table 4). Matings were made by artificial insemination. There were no significant differences between lines for percentage hatchability of fertile eggs in the three generations. Differences among dam and sire lines were not significant in the natural mating flocks (Table 5). Similarly, the sire line X dam line interaction was not significant, suggesting that the influence on percentage fertility of the line of one sex was not dependent on the line of the opposite sex. Thus, the results from both artificial insemination and natural mating indicate that divergent selection for CNCM had relatively minor, if any, effects on fertility
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W. T. COOK AND P. B. SIEGEL Siegel, P. B., 1965. Genetics of behavior: selection for mating ability in chickens. Genetics, 52:12691277. Siegel, P. B., 1972. Behaviour-genetic analyses of male mating in chickens. Anim. Behav. 20: (in press). Snedecor, G. W., and W. G. Cochran, 1967. Statistical Methods, 6th ed. Iowa State Univ. Press, Ames. Tindell, D., and C. G. Arze, 1965. Sexual maturity of male chickens selected for mating ability. Poultry Sci. 44: 70-72. Wood-Gush, D. G. M., 1960. A study of sex drive of two strains of cockerels through three generations. Anim. Behav. 8: 43-53.
Observations on Hypervitaminosis A and Hydropericardium in Chicks L. W. MCCUAIG 1 , H. C. CARLSON2 AND I. MOTZOK1 University of Guelph, Guelph, Ontario, Canada (Received for publication October 29, 1971)
STRACT Male chicks developed severe hydropericardium when fed a 20% tallow diet for the first four weeks of life followed by a tallow-free ration containing 3,250,000 I.U. of vitamin A per kilogram. A small incidence of moderate hydropericardium was found in chicks fed a tallow-free ration for the first four weeks, followed by a 33% tallow diet containing excessive vitamin A. Neither excessive vitamin A nor tallow (20% for the first or 3 3 % for the second four weeks of life) produced the cardiac abnormality, when fed separately. Histopathological studies on the chicks with severe hydropericardium showed various lesions in the myocardium, brain and kidneys. All of these organs were edematous with diffuse cellular degeneration and infiltration with inflammatory cells. The lesions in the cerebellum were characteristic of a vitamin E deficiency. POULTRY SCIENCE 51: 1206-1210,
D
URING preliminary studies of hypervitaminosis A in chicks it was observed that some of the birds had developed severe hydropericardium. This condition appeared in chicks which had previously been fed, to four weeks of age, a 20% tallow diet and were subsequently fed toxic levels of vitamin A in a tallow-free ration. The symptoms appeared similar to those characterizing the "chick edema disease"
1972
which may be caused by a toxic principle found in certain preparations of animal fat (Allen, 1964). There appears to be no reference in the literature to an association between hypervitaminosis A and hydropericardium, therefore a further investigation was made of this relationship. The original findings and further experiments are the subject of the present communication. EXPERIMENTAL
1
Department of Nutrition, College of Biological Science. 2 Department of Pathology, Ontario Veterinary College.
Day-old White Plymouth Rock or White Leghorn cockerels were obtained commercially. They were housed in electrically
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Intra-flock genetic merit under floor and cage managements. Poultry Sci. 35: 1034-1043. McCollom, R. E., 1967. Genetics of behavior: endocrine responses in lines selected for mating behavior. M.S. Thesis, Virginia Polytechnic Institute. Merritt, E. S., and R. S. Gowe, 1962. Development and genetic properties of a control strain of meat type fowl. 12th World's Poultry Cong. Sec. Papers, 66-70. Mosteller, F., and C. Youtz, 1961. Tables of the Freeman-Tukey transformations for the binomial and Poisson distributions. Biometrika, 48: 433440. Nalbandov, A. V., 1964. Reproductive Physiology. 2nd ed. W. H. Freeman and Co., San Francisco.
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Soliman, K. F. A., and T. M. Huston, 1972. Effect of dietary protein and fat on the hematocrit and plasma cholesterol of chickens at different environmental temperature. Poultry Sci. (In press). Stahl, P., G. W. Pipes and C. W. Turner, 1961. Time required for low temperature to influence thyroid secretion rate in fowls. Poultry Sci. 40: 646-650. Turner, C. D., 1966. General Endocrinology. 4th ed. W. B. Saunders Co., Phil. Lond. p. 579. Waldmann, T. A., S. M. Weissman and E. H. Levin, 1962. Effect of thyroid administration of erythropoiesis in the dog. J. Lab. Clin. Med. 59: 926-931. Washburn, K. W., and T. M. Huston, 1968. Effect of environmental temperature on iron deficiency anemia in Athens-Canadian Randombred. Poultry Sci. 47: 1532-1535.
Evaluation of Certain Reproductive Traits in Lines of Chickens Selected for Mating Ability W. T. C O O K 1 AND P . B.
SIEGEL
Department of Poultry Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 (Received for publication October 25, 1971) ABSTRACT An evaluation was made of age at sexual maturity, egg production, egg weight, fertility and hatchability in lines of chickens divergently selected for 10 to 12 generations for cumulative number of completed matings of males. Males of the low mating line matured at earlier ages than those of the unselected control and high mating lines. The four comb phenotypes involving the rose and the pea loci did not influence age at sexual maturity in males. In females no differences were found among lines for age at sexual maturity, hen-day egg production, and egg weights. The selected lines were not different for percentage fertility and hatchability of fertile eggs. POULTRY SCIENCE 51: 1201-1206, 1972
" D I D I R E C T I O N A L selection for com•*-* ponents of sexual behavior results in lines of chickens in which males have different mating propensities (Wood-Gush, 1960; Tindell and Arze, 1965). Siegel (1965, 1972) using the Athens-Canadian (AC) R a n d o m b r e d population as a base, established distinct high and low mating lines by selecting for number of complete
matings. T h e AC randombreds exhibit segregation of alleles at the rose and pea loci (Hess, 1962; Merritt and Gowe, 1962). Reported here are the effects of Siegel's continuous selection for high and low male mating behavior on certain reproductive traits, and the effects of comb phenotypes on one of those traits. MATERIALS AND METHODS
1 Present address, Research Headquarters, HyLine Poultry Farm, Johnston, Iowa 50131.
General. T h e d a t a used in this paper are from the 5 1 0 , S H and Si 2 generations
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 17, 2015
Johnson, P. M., 1955. Hematocrit values for the chick embryos at various ages. Amer. J. Physiol. 180:361-362. McClellan, J. E., C. Donegan, O. A. Thorup and B. S. Leavell, 1958. Survival time of the erythrocyte in myxedema and hyperthyroidism. J. Lab. Clin. Med. 51: 91-96. Moye, R. J., Jr., K. W. Washburn and T. M. Huston, 1970. Effect of environmental temperature on erythrocyte number and size. Poultry Sci. 49: 1683-1686. Rodnan, G. P., F. G. Ebaugh, Jr. and M. R. S. Fox, 1957. The life span of the red blood cell and the red blood cell volume in the chicken, pigeon and duck as estimated by the use of Na251Cr04. Blood, 12: 355-366. Shemin, D., 1948. The biosynthesis of prophyrins. Cold Spring Harbor Symp. Quant. Biol. 13: 185-192.
SURVIVAL
1202
W.
T.
COOK AND P.
Sexual maturity of males. T h e Sio generation cockerels were produced by approximately 30 randomly selected dams from each line. Within lines, 10 to 12 randomly selected sires were rotated among pens of dams to ensure t h a t all comb phenotypes were present among the progeny. Chicks were sexed a t one day of age and lines were intermingled in unisexual flocks. At 56 days of age, 20 males per line (5 per comb phenotype) were randomly selected and randomly assigned to individual cages. Commencing at 63 days of age, males were artificially stimulated thrice weekly until 133 days of age, and weekly thereafter until 150 days of age. Sexual m a t u r i t y was considered as the age at which the second of two consecutive semen samples were obtained. This procedure was satisfactory based on microscopic examination of the semen (Blom, 1950). Aspermatozoic males were assigned 150 days as their age at maturity. D a t a for sexual m a t u r i t y of the Sio generation males were analyzed factorially for a completely randomized design
SIEGEL
(Snedecor and Cochran, 1967, p. 346). The fixed effect model for lines, comb types, and line X comb type interaction used was: Y i j k = n + A; + Bj + A B ( i j ) + e i i k where, Y;jk is the k t h replication of the i t h line and the j t h comb type. Males of the S n and S12 generations were randomly chosen from the progeny of the parents selected to reproduce the lines. Individuals were reared in bisexual flocks until 56 days of age and then placed in individual cages. Based on d a t a from the Sio generation, comb phenotypes were not considered in either of these generations. Procedures for measuring sexual m a t u r i t y were the same as those used in the Sio generation except t h a t stimulations began at 56 days instead of 63 days of age. Comparisons among lines within the S n and S12 generations were by a one way analysis of variance. Means were ranked by D u n c a n ' s multiple range test (Kramer, 1956). Reproductive traits of females. H . M . and L . M . line females of the Sio, S n and the S12 generations were progeny of the parents selected to reproduce the lines. Pullets were reared in heterosexual flocks until placed in unisexual flocks at 56 days of age. T h e y were trapnested 3 days per week through 300 days of age. Comparisons among lines for female sexual maturity and hen-day egg production were tested by a one way analysis of variance, and D u n c a n ' s multiple range test was used to rank the means (Kramer, 1956). Weights of eggs laid at 241, 242, and 243 days of age were obtained in the S12 generation. Each egg was weighed to the nearest g. the morning after it was laid. Egg weights were subjected to hierarchal analysis for differences among lines and among females within lines. Snedecor and Cochran (1967, p. 291) present an ap-
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 17, 2015
of the high mating (H.M.) and the low mating (L.M.) lines developed by Siegel (1965, 1972) from the AC randombred population. T h e base population for the selected lines consisted of the AC randombreds in which all 4 of the classic comb phenotypes for the rose and the pea loci were present (rose, pea, walnut and single). T h e selection criterion was the cumulative number of completed matings ( C N C M ) b y a male in 8, tenminute observation periods. Details of selection and general management procedures have been given (Siegel, 1965; 1972). Briefly, chicks were hatched in M a r c h of each year, and hot-air brooded in floor pens with wood shavings. Food and water were given ad libitum, and there was no artificial lighting after 14 days of age.
B.
EVALUATION OF REPRODUCTION TRAITS
propriate analysis for a mixed model, since lines were considered fixed and females within lines were random. The model used was: Y i i k = fi + Ai + Bij + eijk
Multiple male matings were made in the Sn generation. T h e y involved all combinations of the 3 lines. Twelve females per line were randomly chosen and randomly assigned to each male line. Eggs t h a t did not hatch were broken out, and macroscopic determinations were made for fertility. Percentages were converted to arc sines and analyzed by factorial plan with a fixed effect model: Y i i k = ji + Si + Dj + S D ( i i ) + eij k where, Yij k is the k t h observation of the i t h sire line mated to the j t h d a m line. D u e to disproportionality, analysis was made by the method of weighted squares of means (Bancroft, 1968; sec 1.8).
RESULTS AND DISCUSSION
Sexual maturity—males. Means and standard errors for sexual m a t u r i t y of males by lines and comb types are presented in Table 1 for the Sio generation. The comb type X line interaction was not significant showing t h a t the response among comb types was similar for all lines. No differences were found among comb types for age at male sexual maturity. There were significant differences among lines with L . M . males maturing earlier than H . M . and AC males. T h e latter two lines were not significantly different from each other. T h e relationship observed among lines in the Sio generation was confirmed in the S n and S12 generations where males from the L . M . line again matured at significantly earlier ages than those from the H . M . and AC lines (Table 2). McCollom (1967), using only single comb phenotypes, found t h a t males from the L . M . line had combs comparable to or larger than those in the H . M . and AC lines. His results, and ours, suggest t h a t there are differences in the pituitary-gonadal axis of these lines. T h e results of this study are consistent with and extend those of Tindell and Arze (1965) who observed t h a t S2 generation males in lines selected for low mating matured earlier than those selected for high mating. Their lines came from the same genetic base as ours. Since the difference between the AC randombred TABLE 1.—Means and standard errors for age (days) at sexual maturity of Sio males by lines and comb phenotypes Comb type Rose Pea Walnut Single Pooled
Lines H.M. 101±13 96+ 5 100+ 7 97 ±10 b 98 ± 4
AC
L.M.
Pooled
97 + 21 112+11 110+ 6 99+ 9 105+ 3 b
83±5 92±7 85 + 5 79 + 3a 85±3
94+8" 100+ 4 a 98 + 4" 92 + 4"
Any two marginal row or column means with the same superscript are not different (P<.05),
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where, A ; is the effect of the i t h line and Bij is the random variable for the j t h females within the i t h line. Fertility and hatchability. Incubation data for the selected lines were based on weekly artificial inseminations, and eggs were incubated in 3 bi-weekly hatches. Ten sires, selected for C N C M , were each mated with 3 to 5 randomly chosen females to reproduce each selected line. Presented here are the percentage fertility and hatchability of fertile eggs for t h e H . M . a n d L . M . l i nes for the S io, S ii, and S12 parental generations. Fertility was determined by candling at 16 days of incubation. Percentages were obtained for each individual mating and converted to arc sines as suggested b y Mosteller and Youtz (1961) for individuals with less than 50 observations. Comparable fertility and hatchability d a t a were not available for the AC randombreds because chicks were hatched from unpedigreed eggs received from the parent population.
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1204
W. T. COOK AND P. B. SIEGEL TABLE 2.—Means and standard errors for age at sexual maturity of males and females by line and generations n
Sex
x + se (days)
Gen H.M.
AC
L.M.
H.M.
L.M.
AC b
b
105 ± 3 107 ± 3 b 100 ± 5 b
85+3" 92 ± 3 " 85 ± 3 "
174±2" 170 + 2" 40 91 79 5io 188 ± 3 b 179 + 2" 52 59 110 186 ±4" 177 + 2" 73 64 106 Sn Sl2 Any two means in a row with the same superscript are not different (P<0.5).
175 + 5" 175 ± 3 " 180 + 4"
Male
Sio Sn Sl2
20 15 20
20 15 20
Female
98 + 4 103+4 b 98±4b
for social dominance. Sexes in our study were maintained differently; males were placed in individual cages prior to the formation of stable peck orders while females were maintained in flocks. Therefore, the different ranking of the lines for age at sexual maturity of males and females may reflect an interaction of sex by method of rearing. The second possibility is that, although age at sexual maturity of males and females depends on an association of hornomes and threshold levels, the components of the relationship in the sexes are different (Nalbandov, 1964). Thus, a selection criterion that modifies the hormonal-threshold relationship for both the primary and correlated traits in one sex may not necessarily alter the correlated responses of reproductive traits in the opposite sex. Therefore, selection for CNCM in males may have caused a correlated response in age at first spermatozoa production without affecting age at first egg. Related traits. Eggs were weighed during a 3-day period in the S12 generation for 43 H.M., 40 AC and 32 L.M. females. Mean egg weights were 51.3, 49.4 and 49.1 g. for H.M., AC and L.M. lines, respectively. Differences among lines and among females within lines were not significant. Egg production of the H.M. and L.M. lines was significantly higher than for the AC females in the Sn, but not the
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population and the L.M. line was also significant, it may be hypothesized that the difference among lines is due to a change in age at maturity for L.M. line males and not for the AC and H.M. lines. Sexual maturity—females. Differences among lines were not significant in the Sio and S12 generations, whereas in the Sn generation the control pullets matured significantly later than those of the selected lines (Table 2). Only once during the first 9 generations of selection was there a significant difference between selected lines for age at first egg. The lack of consistent differences between lines suggests that bidirectional selection for CNCM had little influence on the age of sexual maturity of females. The consistency of differences among lines for age at sexual maturity of males contrasts with the absence of differences among lines for age at first egg. Two hypotheses may be proposed to explain the inconsistency between sexes. First, there is the possibility of differential effects of social behavior for individually caged males and flock-reared females. Lowry et al. (1956) and Biswas and Craig (1970) observed that pullets maintained in cages matured earlier than those kept in floor flocks. Further, Biswas and Craig observed a significant interaction for age at first egg between rearing methods and lines that had been divergently selected
20 14 20
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EVALUATION OF REPRODUCTION TRAITS TABLE 3.—Means and standard errors for percentage hen-day egg production by lines arid generations
TABLE 5.—Means and standard errors for percentage fertility in natural matings Sire line
n
x±se
Dam line
Gen H.M. Sio S« Su
AC
79 110 106
91 59 64
L.M.
H.M.
AC
L.M.
45 52 73
47 + 2" 62±lb 59+2a
4 9 ± 3 aa
48+3a 60+3b 59 ± 2 "
53±3 60+3"
Any two means in a row with the same superscript are not different (P<.05).
H.M. AC L.M. Pooled
H.M.
AC
L.M.
Pooled
95 + 4 92 + 1 97 + 2 95 + 2"
98±1 98±1 95±3 97±la
98±1 98±3 99 + 1 98±la
97 + 2a 96 + 2a 97 + 2a
Any two marginal row or column means with the same superscript are not different (P<.05).
TABLE 4.—Means and standard errors for percentage fertility and hatch of fertile eggs by lines and generations
1
x + se 1
n
Parental gen.
H.M.
L.M.
H.M.
L.M.
SlO Sn Si.
27 39 43
24 32 38
8 7 ± 3 ba 81±3a 74±4
70±5a 81 + 4aa 74+4
Sio Su Su
27 38 41
21 31 38
74 + 5" 69 + 4 a 58 + 5"
72+6a 77 + 3" 64+4a
Matings were produced by artificial insemination. Any two means in a row with the same superscript are not different (P<.05).
and hatchability. The fertility data suggest that the lower mating frequency of the L.M. line in comparison to the H.M. line may be compensated for by the superior semen quality of the former (Siegel, 1965, 1972). Cook (1971), using these same lines noted that raising juvenile males with or without females had little influence on the number of completed matings at 32-34 weeks of age. The results of that study and this one suggest that percentage fertility and hatchability of breeding flocks would not be altered by rearing sexes separately or intermingled and by the behavioral modifications made to date through selection for CNCM. REFERENCES Bancroft, T. A., 1968. Topics in Intermediate Statistical Methods. Iowa State Univ. Press, Ames. Biswas, D. K., and J. V. Craig, 1970. Genotype-environment interactions in chickens selected for high and low social dominance. Poultry Sci. 49: 681-692. Blom, E., 1950. A one minute live-dead sperm stain by means of eosin nigrosin. Fertility Sterility, 1: 176-177. Cook, W. T., 1971. Quantitative and qualitative genetic analyses of mating behavior in chickens. Ph.D. Dissertation, Vir. Poly. Instit. & State Univ. Hess, C. W., 1962. Randombred populations of the Southern Regional Poultry Breeding Project. World's Poultry Sci. J. 18: 147-152. Kramer, C. Y., 1956. Extension of multiple range tests to group means with unequal class numbers of replications. Biometrics, 12: 307-310. Lowry, D. C , I. M. Lerner and L. W. Taylor, 1956.
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Sio and S12 generations (Table 3). Divergent selection for mating ability of males thus had relatively minor effects on these two traits. Differences between the H.M. and L.M. lines for percentage fertility in matings used to reproduce the lines were significant in the Sio but not in the Sn and S12 generations (Table 4). Matings were made by artificial insemination. There were no significant differences between lines for percentage hatchability of fertile eggs in the three generations. Differences among dam and sire lines were not significant in the natural mating flocks (Table 5). Similarly, the sire line X dam line interaction was not significant, suggesting that the influence on percentage fertility of the line of one sex was not dependent on the line of the opposite sex. Thus, the results from both artificial insemination and natural mating indicate that divergent selection for CNCM had relatively minor, if any, effects on fertility
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W. T. COOK AND P. B. SIEGEL Siegel, P. B., 1965. Genetics of behavior: selection for mating ability in chickens. Genetics, 52:12691277. Siegel, P. B., 1972. Behaviour-genetic analyses of male mating in chickens. Anim. Behav. 20: (in press). Snedecor, G. W., and W. G. Cochran, 1967. Statistical Methods, 6th ed. Iowa State Univ. Press, Ames. Tindell, D., and C. G. Arze, 1965. Sexual maturity of male chickens selected for mating ability. Poultry Sci. 44: 70-72. Wood-Gush, D. G. M., 1960. A study of sex drive of two strains of cockerels through three generations. Anim. Behav. 8: 43-53.
Observations on Hypervitaminosis A and Hydropericardium in Chicks L. W. MCCUAIG 1 , H. C. CARLSON2 AND I. MOTZOK1 University of Guelph, Guelph, Ontario, Canada (Received for publication October 29, 1971)
STRACT Male chicks developed severe hydropericardium when fed a 20% tallow diet for the first four weeks of life followed by a tallow-free ration containing 3,250,000 I.U. of vitamin A per kilogram. A small incidence of moderate hydropericardium was found in chicks fed a tallow-free ration for the first four weeks, followed by a 33% tallow diet containing excessive vitamin A. Neither excessive vitamin A nor tallow (20% for the first or 3 3 % for the second four weeks of life) produced the cardiac abnormality, when fed separately. Histopathological studies on the chicks with severe hydropericardium showed various lesions in the myocardium, brain and kidneys. All of these organs were edematous with diffuse cellular degeneration and infiltration with inflammatory cells. The lesions in the cerebellum were characteristic of a vitamin E deficiency. POULTRY SCIENCE 51: 1206-1210,
D
URING preliminary studies of hypervitaminosis A in chicks it was observed that some of the birds had developed severe hydropericardium. This condition appeared in chicks which had previously been fed, to four weeks of age, a 20% tallow diet and were subsequently fed toxic levels of vitamin A in a tallow-free ration. The symptoms appeared similar to those characterizing the "chick edema disease"
1972
which may be caused by a toxic principle found in certain preparations of animal fat (Allen, 1964). There appears to be no reference in the literature to an association between hypervitaminosis A and hydropericardium, therefore a further investigation was made of this relationship. The original findings and further experiments are the subject of the present communication. EXPERIMENTAL
1
Department of Nutrition, College of Biological Science. 2 Department of Pathology, Ontario Veterinary College.
Day-old White Plymouth Rock or White Leghorn cockerels were obtained commercially. They were housed in electrically
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Intra-flock genetic merit under floor and cage managements. Poultry Sci. 35: 1034-1043. McCollom, R. E., 1967. Genetics of behavior: endocrine responses in lines selected for mating behavior. M.S. Thesis, Virginia Polytechnic Institute. Merritt, E. S., and R. S. Gowe, 1962. Development and genetic properties of a control strain of meat type fowl. 12th World's Poultry Cong. Sec. Papers, 66-70. Mosteller, F., and C. Youtz, 1961. Tables of the Freeman-Tukey transformations for the binomial and Poisson distributions. Biometrika, 48: 433440. Nalbandov, A. V., 1964. Reproductive Physiology. 2nd ed. W. H. Freeman and Co., San Francisco.