- Email: [email protected]
Selection for Body Weight at Eight Weeks of Age
741
EPICARDIUM AND PCB 's Kuratsune, M., 1972. An abstract of results ot laboratory examinations ot patients with yusho and of animal experiments. Environmental Health Perspectives, 1: 129-136. McCune, E. L., J. E. Savage and B. L. O'Dell, 1962. Hydropericardium and ascites in chicks fed a chlorinated hydrocarbon. Poultry Sci. 41: 295-299.
Rehfeld, B. M., R. L. Bradley, Jr. and M. L. Sunde, 1971. Toxicity studies on polychlorinated biphenyls in the chick. Poultry Sci. 50: 1090-10%. Simpson, C. B., W. R. Pritchard and R. H. Harms, 1959. An endotheliosis in chickens and turkeys caused by an unidentified dietary factor. J. Amer. Vet. Med. Ass. 134: 410-416.
Selection For Body Weight at Eight Weeks of Age H . P. V A N K R E Y AND P. B . SIEGEL
Department of Poultry Science, Virginia Polytechnic Institute and State University, Virginia 24061
Blacksburg,
(Received for publication July 13, 1973)
ABSTRACT Levels and duration of fertility were measured in two lines of White Rock chickens divergently selected for body weight, and in the reciprocal crosses between them. Although values consistently favored sires and dams from the low-weight line, differences between them were not consistently significant. Embryonic data indicated that the divergent selection for somatogenesis has not led to the correlated selection for lethal genes affecting embryogenesis. POULTRY SCIENCE 53: 741-745, 1974
INTRODUCTION
A
N important criterion in selection is that of fitness. Lerner (1954), in discussing genetic homeostasis, described how artificial selection for specific traits may be associated with characteristics that determine fitness. Most of the reports regarding chickens have dealt with fertility or other reproductive fitness components of either the male or the female. These have included semen quality parameters such as volume, concentration, motility, metabolism and fertilizing capacity (e.g., Allen and Champion, 1955; Soller et al., 1966; Marini and Goodman, 1969) and facets of egg production such as age at sexual maturity, egg size, and intensity of lay (e.g., Japp et al., 1962; Merritt et al., 1962; Maloney et al., 1967). Periodically, experiments have used a different theme (e.g., Jones and Lamereux, 1942; Verghese and Nordskog, 1968; Hassan and Nordskog, 1971). Our interest in this area has centered upon
the correlated responses of male and female reproductive traits in lines selected for high and low juvenile body weight. Reported here are the levels of fertility and the duration of fertility of these lines as well as the reciprocal crosses between them. MATERIALS AND METHODS Lines. The males and females were randomly selected from S14 and S15 generation White Rock lines that had been selected for high (HW) and low (LW) body weight at 8 weeks of age (Siegel, 1962). Since the beginning of selection the mean body weight of the HW line had increased to about 2.5 times greater than that of the LW line. Also, pullets from the HW line matured earlier, had a lower hen-day egg production, and produced more defective eggs than those from the LW line (Siegel, 1970; Udale etal., 1972). In addition, there were not line differences in the numbers of uterovaginal sperm host glands, but fol-
Downloaded from http://ps.oxfordjournals.org/ at East Carolina University on April 22, 2015
13. F E C U N D I T Y
742
H. P. VAN KREY AND P. B. SIEGEL
TABLE 1.—Number and sex of birds by line and by generation Fem ales
Males Gen. SM
Line
n
Line
n
HW
12
LW
12
HW LW HW LW
32 32 32 32
S,5
HW
12
LW
12 24
HW LW HW LW
39 39 39 39 156
lowing artificial insemination, a significantly greater number of glands remained empty in the HW line (Van Krey et al., 1971). Semen from the HW line contained more abnormal spermatozoa than that of the LW line (Edens et al., 1973b). Spermatozoal metabolism studies indicated no differences between lines in exogenous metabolism, but spermatozoa in the LW line did maintain a greater rate of endogenous metabolism (Edens et al, 1973a). Procedure. Birds for each generation were hatched in March and fertility was measured in the late fall. Housing and management procedures were similar for both generations. Females within a line were randomized into two equal groups. Hens from one group were each inseminated with .05 cc. of pooled semen from that line and those of the second group each received .05 cc. of semen from the other line. Semen within a line was pooled to minimize individual male influences. Two trials were conducted for each generation with the number of males and females listed in Table 1. Eggs, identified by hen and date of lay, were gathered daily for 20 consecutive days commencing the second day after insemination. Eggs were incubated at weekly intervals. On the 18th day of incubation, eggs were removed from the incubator, candled, and
Yijk = u + R, + T. + (RT);j + eijk where i = 1,2 replications; j = 1,2,3,4 treatment combinations and k = 1,2 . . . r pullets per replication per treatment combination. The treatment combinations were broken down into a male line effect, a female line effect and a male line-female line interaction. Because of the many difficulties associated with detecting early embryonic mortality after 18 days of incubation an adjunct experiment was conducted to test for the incidence of preoviposital mortality. A total of 40 hens, 10 for each selected line and 10 for each reciprocal cross, were each inseminated with .05 cc. of pooled semen. This experiment differed from the previous experiments in that the eggs were incubated for only 24 hours after which time the blastodiscs were examined macroscopically for evidence of development. Any blastodisc not obviously fertile was processed histologically for a microscopic examination. An intact, syncytiumlike, layer of cells was interpreted as a potentially viable, albeit retarded embryo, whereas a disorganized cellular development was interpreted as a potentially non-viable embryo. A lack of any cellular development was
Downloaded from http://ps.oxfordjournals.org/ at East Carolina University on April 22, 2015
Total
128
24
Total
the live embryos were transferred to the hatcher. The remaining eggs were broken out and examined macroscopically for evidence of embryonic development. Fertility data were summarized for each pullet for the first 7 days post-insemination in the S 14 generation, the first 6 days in the S l 5 generation, and the overall period in both generations. The Freeman-Tukey arc-sine transformation for binomial proportions (Mosteller and Youtz, 1961) was made prior to analyses of variance. The duration of fertility was measured in numbers of days post-insemination. Analyses were within generations; the statistical model, with replications considered random and treatment combinations considered fixed, was:
743
SELECTION FOR BODY WEIGHT
TABLE 2.—Means and standard errors—SI4 generation
Male line HW LW
1-7 Days % Fertility
% Fertility
82.3 : 2.9"a 87.6: 2.6
45.4 53.2
1-20 Days Duration of fertility
2.6ab 2.1
9.7 : 0.5a 11.4: : 0 . 4 b
Female line 10.2 ± 0.4aa HW 44.2 2.1ab 80.2 ± 3.1" LW 10.9 ± 0.4 54.3 2.6 89.6 ± 2.4" Within an experiment any two means on the vertical which do not have the same superscript are significantly different (P s 0.05). None of the male line x female line interactions were significant.
RESULTS AND DISCUSSION Fertility. The trend over both generations was for the fertility of the LW line males to exceed that of the HW line males (Tables 2 and 3). Although these trends were consistent for both generations, only the fertility for the 20-day period of the S14 generation was significantly different (LW > HW). The duration of fertility for the LW line males was also significantly longer than for HW males in that generation. As mentioned, differences in semen quality have been reported between these selected lines (Edens et al., 1973b). High-weight line semen contained twice as many morphologically abnormal spermatozoa which resulted in approximately 20% fewer functional sperm cells. Such a large discrepancy in numbers of viable spermatozoa might be expected to reflect adversely on fertility patterns, espe-
cially if other insemination conditions are less than ideal. In view of the above, the data reported here indicate that a great deal of latitude exists in the numbers of spermatozoa required to attain high levels of fertility. Also, our earlier quantification studies (Van Krey et al., 1971) showed that considerably more spermatozoa are normally artificially inseminated than are necessary for optimum fertility. Hens possessing 33% less sperm-storage tissue exhibited fertility levels comparable to those of hens possessing relatively greater complements of such tissue. This concept of surplus spermatozoa agrees with Munro (1938) and van Tienhoven and Steel (1957). Their data also indicated a relatively wide degree of latitude with respect to the effects of sperm numbers on fertility. Thus, it would appear that the higher incidence of abnormal spermatozoa in the HW line semen merely served to reduce the margin for error during inse-
TABLE 3.—Means and standard errors—Sls generation
Male line HW LW
1-6 Days % Fertility
% Fertility
a 91.4 : 2.3 1.5" 95.6:
57.9: 2.0as 60.9: 2.4
1-20 Days Duration of fertility 11.0 ± 0.3a 10.8 ± 0.3a
Female line 90.8 ± 2.5ab HW 58.6 ± 2.4a 10.2 ± 0.4ab 96.1 ± 1.2 11.6 ± 0.3 60.2 ± 1.9" LW Within an experiment any two means on the vertical which do not have the same superscript are significantly different (P < 0.05). None of the male line x the female line interactions were significant.
Downloaded from http://ps.oxfordjournals.org/ at East Carolina University on April 22, 2015
interpreted to mean an infertile egg.
744
H. P. VAN KREY AND P. B. SIEGEL
Mortality. No male line effect was observed for embronic mortality for either generation. A significant female line difference (LW > HW) in mortality did occur in the S 14 generation but not in the S15 generation. Although reasons for this inconsistency are unknown, it was not due to the selective development of visibly detectable genetic lethals (i.e., lethals expressed relatively late in the course of the development). All dead embryos were carefully examined and classified with respect to age at death and discernible anatomical abnormalities. No consistent symptomatic or temperal trends were established. A randomized mortality pattern was observed suggesting that the incidence of detectable genetic lethals was not influencing the female line differences in mortality. Pre-oviposital and/or early post-oviposital mortality were also investigated because mortality during either of these periods may very easily be incorrectly interpreted as infertility. Line differences in mortality during these times could aid in explaining line differences in fertility. They would also indicate
whether or not there had been a correlated selection for lethal genes having an effect early in the course of embryonic development. To answer these questions, the adjunct experiment was designed. All the macroscopically infertile eggs were processed for a microscopic examination. Ninety such eggs wereexamined, of which 15.6% showed some degree of cellular development. There were, however, no differences between the various pure and reciprocal crosses; indicating male or female line differences in early acting genetic lethals did not exist among mating combinations. This latter information, along with the previously mentioned absence of genetic lethals acting late in the course of embryonic development, point out that 15 generations of divergent selection for somatogenesis has not led to the correlated selection for lethal genes affecting embryogenesis. REFERENCES Allen, C. J., and L. R. Champion, 1955. Competitive fertilization in the fowl. Poultry Sci. 34: 1332-1342. Edens, F. W., H. P. Van Krey and P. B. Siegel, 1973a. Selection for body weight at eight weeks of age. 9. Spermatozoal respiration. Poultry Sci. 52: 977-981. Edens, F. W., H. P. Van Krey and P. B. Siegel, 1973b. Selection for body weight at eight weeks of age. 10. Spermatozoal morphology. Poultry Sci. 52: 2287-2290. Hassan, G. M., and A. W. Nordskog, 1971. Effects of egg size and heterozygosis on embryonic growth and hatching speed. Genetics, 67: 279-285. 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. 41: 1439-1446. Jones, D. G., and W. F. Lamoreux, 1942. Semen production of White Leghorn males from strains selected for high and low fecundity. Poultry Sci. 21: 173-184. Lerner, I. M., 1954. Genetic Homostasis. John Wiley and Sons, New York. Maloney, M. A., J. C. Gilbreath, J. F. Tierce and R. D. Morrison, 1967. Divergent selection for twelve-week body weight in the domestic fowl. Poultry Sci. 46: 1116-1127. Marini, P. J., and B. L. Goodman, 1969. Semen
Downloaded from http://ps.oxfordjournals.org/ at East Carolina University on April 22, 2015
mination, and was not necessarily affecting fertility per se. The fertility data for females showed that the LW line consistently exceeded the HW line with respect to both levels of fertility and duration of fertility (Tables 2 and 3). While the trends were consistently in favor of the LW line females, differences between lines were significant in only four of the six comparisons. These data resemble somewhat those of Jones and Lamoreux (1942), who found that both sexes responded similarly to a unisexual selection program. As a result of the bisexual response, they concluded that semen production and egg production were expressions of comparable genotypes for high and low fecundity. In our experiment, it was found that the generalized response, reproductive fitness, was also similar for both sexes.
745
SELECTION FOR BODY W E I G H T
tability of semen quality, concentration and motility in White Rock roosters and their genetic correlation with rate of gain. Poultry Sci. 44: 1527-1529. Udale, R. W., P. B. Siegel and H. P. Van Krey, 1972. Rates of ovulation and oviposition in growth selected lines of chickens. Poultry Sci. 51: 20982100. Van Krey, H. P., P. B. Siegel and A. T. Leighton, Jr., 1971. Repeatability estimates and quantification of uterovaginal sperm-host gland numbers and population patterns. Biol. Reprod. 4: 31-34. van Tienhoven, A., and R. G. D. Steel, 1957. The effect of different diluents and dilution rates on fertilizing capacity of turkey semen. Poultry Sci. 36: 473-479. Verghese, M. N., and A. W. Nordskog, 1968. Correlated responses in reproductive fitness to selection in chickens. Genet. Res. 11: 221-238.
Lipovitellins in Fresh and Stored Shell Eggs ! ROBERT JOHN E V A N S , DORIS H . BAUER AND C A L J. FLEGAL
Departments of Biochemistry and Poultry Science, Michigan State University, East Lansing, 48823
Michigan
(Received for publication July 13, 1973)
ABSTRACT Lipovitellins were isolated from fresh eggs and from eggs which had been kept in cold storage for 6 months. No differences in structure were observed when studied by the procedure of progressive proteolytic digestion. Both the lipovitellins of fresh eggs and those of stored eggs were composed of 23% alpha-lipovitellin and 77% of beta-lipovitellin. No changes in lipids of the lipovitellins occurred during storage of the eggs. An increase in electrophoretic mobility of part of the lipovitellins was previously observed to occur during cold storage of shell eggs, but no changes were observed in lipovitellin during storage which would account for the change in electrophoretic properties of the lipovitellins. POULTRY SCIENCE 53: 745-750, 1974
INTRODUCTION
S
TUDIES of changes in the chemical composition of shell eggs during cold storage have been in progress at Michigan State University for about 25 years. Early studies of changes in egg proteins which occur during cold storage of shell eggs were made with the egg-white proteins because suitable
1. Michigan Agricultural Experiment Station Journal Article No. 6459 Supported in part by Public Health Service Grant AM 10214 from the National Institute of Arthritis and Metabolic Diseases.
procedures were not available for the study of egg yolk proteins (Evans et al., 1949). Evans et al. (1958) studied the distribution of proteins in the yolks of fresh and stored shell eggs, following the development of a procedure for separation of egg yolk proteins by paper electrophoresis (Evans and Bandemer, 1957). Yolk protein from 12-month old eggs appeared to contain less lipovitellin and more very low density lipoprotein than that from fresh eggs, and the very low density lipoprotein from 12-month old eggs moved almost twice as fast electrophoretically as
Downloaded from http://ps.oxfordjournals.org/ at East Carolina University on April 22, 2015
characteristics as influenced by selection for divergent growth rate in chicks. Poultry Sci. 48: 859-865. Merritt, E. S., M. Zowalsky and S. B. Slen, 1962. Direct and correlated responses to selection for 63-day body weight in chickens. 13th World's Poultry Cong. 86-91. Mosteller, F., and C. Youtz, 1961. Tables of the Freeman-Tukey transformations for the binomial and Poisson distributions. Biometrika, 48: 433-440. Munro, S. S., 1938. The effect of dilution and density on the fertilizing capacity of fowl sperm suspensions. Canadian J. Res. 16: 281-299. Siegel, P. B., 1962. Selection for body weight at eight weeks of age. 1. Short term responses and heritabilities. Poultry Sci. 41: 954-962. Siegel, P. B., 1970. Selection for juvenile body weights in chickens. World Poultry Cong. Sci. Comm. 2: 465-471. Soller, M., N. Snapir and H. Schindler, 1966. Heri-
EPICARDIUM AND PCB 's Kuratsune, M., 1972. An abstract of results ot laboratory examinations ot patients with yusho and of animal experiments. Environmental Health Perspectives, 1: 129-136. McCune, E. L., J. E. Savage and B. L. O'Dell, 1962. Hydropericardium and ascites in chicks fed a chlorinated hydrocarbon. Poultry Sci. 41: 295-299.
Rehfeld, B. M., R. L. Bradley, Jr. and M. L. Sunde, 1971. Toxicity studies on polychlorinated biphenyls in the chick. Poultry Sci. 50: 1090-10%. Simpson, C. B., W. R. Pritchard and R. H. Harms, 1959. An endotheliosis in chickens and turkeys caused by an unidentified dietary factor. J. Amer. Vet. Med. Ass. 134: 410-416.
Selection For Body Weight at Eight Weeks of Age H . P. V A N K R E Y AND P. B . SIEGEL
Department of Poultry Science, Virginia Polytechnic Institute and State University, Virginia 24061
Blacksburg,
(Received for publication July 13, 1973)
ABSTRACT Levels and duration of fertility were measured in two lines of White Rock chickens divergently selected for body weight, and in the reciprocal crosses between them. Although values consistently favored sires and dams from the low-weight line, differences between them were not consistently significant. Embryonic data indicated that the divergent selection for somatogenesis has not led to the correlated selection for lethal genes affecting embryogenesis. POULTRY SCIENCE 53: 741-745, 1974
INTRODUCTION
A
N important criterion in selection is that of fitness. Lerner (1954), in discussing genetic homeostasis, described how artificial selection for specific traits may be associated with characteristics that determine fitness. Most of the reports regarding chickens have dealt with fertility or other reproductive fitness components of either the male or the female. These have included semen quality parameters such as volume, concentration, motility, metabolism and fertilizing capacity (e.g., Allen and Champion, 1955; Soller et al., 1966; Marini and Goodman, 1969) and facets of egg production such as age at sexual maturity, egg size, and intensity of lay (e.g., Japp et al., 1962; Merritt et al., 1962; Maloney et al., 1967). Periodically, experiments have used a different theme (e.g., Jones and Lamereux, 1942; Verghese and Nordskog, 1968; Hassan and Nordskog, 1971). Our interest in this area has centered upon
the correlated responses of male and female reproductive traits in lines selected for high and low juvenile body weight. Reported here are the levels of fertility and the duration of fertility of these lines as well as the reciprocal crosses between them. MATERIALS AND METHODS Lines. The males and females were randomly selected from S14 and S15 generation White Rock lines that had been selected for high (HW) and low (LW) body weight at 8 weeks of age (Siegel, 1962). Since the beginning of selection the mean body weight of the HW line had increased to about 2.5 times greater than that of the LW line. Also, pullets from the HW line matured earlier, had a lower hen-day egg production, and produced more defective eggs than those from the LW line (Siegel, 1970; Udale etal., 1972). In addition, there were not line differences in the numbers of uterovaginal sperm host glands, but fol-
Downloaded from http://ps.oxfordjournals.org/ at East Carolina University on April 22, 2015
13. F E C U N D I T Y
742
H. P. VAN KREY AND P. B. SIEGEL
TABLE 1.—Number and sex of birds by line and by generation Fem ales
Males Gen. SM
Line
n
Line
n
HW
12
LW
12
HW LW HW LW
32 32 32 32
S,5
HW
12
LW
12 24
HW LW HW LW
39 39 39 39 156
lowing artificial insemination, a significantly greater number of glands remained empty in the HW line (Van Krey et al., 1971). Semen from the HW line contained more abnormal spermatozoa than that of the LW line (Edens et al., 1973b). Spermatozoal metabolism studies indicated no differences between lines in exogenous metabolism, but spermatozoa in the LW line did maintain a greater rate of endogenous metabolism (Edens et al, 1973a). Procedure. Birds for each generation were hatched in March and fertility was measured in the late fall. Housing and management procedures were similar for both generations. Females within a line were randomized into two equal groups. Hens from one group were each inseminated with .05 cc. of pooled semen from that line and those of the second group each received .05 cc. of semen from the other line. Semen within a line was pooled to minimize individual male influences. Two trials were conducted for each generation with the number of males and females listed in Table 1. Eggs, identified by hen and date of lay, were gathered daily for 20 consecutive days commencing the second day after insemination. Eggs were incubated at weekly intervals. On the 18th day of incubation, eggs were removed from the incubator, candled, and
Yijk = u + R, + T. + (RT);j + eijk where i = 1,2 replications; j = 1,2,3,4 treatment combinations and k = 1,2 . . . r pullets per replication per treatment combination. The treatment combinations were broken down into a male line effect, a female line effect and a male line-female line interaction. Because of the many difficulties associated with detecting early embryonic mortality after 18 days of incubation an adjunct experiment was conducted to test for the incidence of preoviposital mortality. A total of 40 hens, 10 for each selected line and 10 for each reciprocal cross, were each inseminated with .05 cc. of pooled semen. This experiment differed from the previous experiments in that the eggs were incubated for only 24 hours after which time the blastodiscs were examined macroscopically for evidence of development. Any blastodisc not obviously fertile was processed histologically for a microscopic examination. An intact, syncytiumlike, layer of cells was interpreted as a potentially viable, albeit retarded embryo, whereas a disorganized cellular development was interpreted as a potentially non-viable embryo. A lack of any cellular development was
Downloaded from http://ps.oxfordjournals.org/ at East Carolina University on April 22, 2015
Total
128
24
Total
the live embryos were transferred to the hatcher. The remaining eggs were broken out and examined macroscopically for evidence of embryonic development. Fertility data were summarized for each pullet for the first 7 days post-insemination in the S 14 generation, the first 6 days in the S l 5 generation, and the overall period in both generations. The Freeman-Tukey arc-sine transformation for binomial proportions (Mosteller and Youtz, 1961) was made prior to analyses of variance. The duration of fertility was measured in numbers of days post-insemination. Analyses were within generations; the statistical model, with replications considered random and treatment combinations considered fixed, was:
743
SELECTION FOR BODY WEIGHT
TABLE 2.—Means and standard errors—SI4 generation
Male line HW LW
1-7 Days % Fertility
% Fertility
82.3 : 2.9"a 87.6: 2.6
45.4 53.2
1-20 Days Duration of fertility
2.6ab 2.1
9.7 : 0.5a 11.4: : 0 . 4 b
Female line 10.2 ± 0.4aa HW 44.2 2.1ab 80.2 ± 3.1" LW 10.9 ± 0.4 54.3 2.6 89.6 ± 2.4" Within an experiment any two means on the vertical which do not have the same superscript are significantly different (P s 0.05). None of the male line x female line interactions were significant.
RESULTS AND DISCUSSION Fertility. The trend over both generations was for the fertility of the LW line males to exceed that of the HW line males (Tables 2 and 3). Although these trends were consistent for both generations, only the fertility for the 20-day period of the S14 generation was significantly different (LW > HW). The duration of fertility for the LW line males was also significantly longer than for HW males in that generation. As mentioned, differences in semen quality have been reported between these selected lines (Edens et al., 1973b). High-weight line semen contained twice as many morphologically abnormal spermatozoa which resulted in approximately 20% fewer functional sperm cells. Such a large discrepancy in numbers of viable spermatozoa might be expected to reflect adversely on fertility patterns, espe-
cially if other insemination conditions are less than ideal. In view of the above, the data reported here indicate that a great deal of latitude exists in the numbers of spermatozoa required to attain high levels of fertility. Also, our earlier quantification studies (Van Krey et al., 1971) showed that considerably more spermatozoa are normally artificially inseminated than are necessary for optimum fertility. Hens possessing 33% less sperm-storage tissue exhibited fertility levels comparable to those of hens possessing relatively greater complements of such tissue. This concept of surplus spermatozoa agrees with Munro (1938) and van Tienhoven and Steel (1957). Their data also indicated a relatively wide degree of latitude with respect to the effects of sperm numbers on fertility. Thus, it would appear that the higher incidence of abnormal spermatozoa in the HW line semen merely served to reduce the margin for error during inse-
TABLE 3.—Means and standard errors—Sls generation
Male line HW LW
1-6 Days % Fertility
% Fertility
a 91.4 : 2.3 1.5" 95.6:
57.9: 2.0as 60.9: 2.4
1-20 Days Duration of fertility 11.0 ± 0.3a 10.8 ± 0.3a
Female line 90.8 ± 2.5ab HW 58.6 ± 2.4a 10.2 ± 0.4ab 96.1 ± 1.2 11.6 ± 0.3 60.2 ± 1.9" LW Within an experiment any two means on the vertical which do not have the same superscript are significantly different (P < 0.05). None of the male line x the female line interactions were significant.
Downloaded from http://ps.oxfordjournals.org/ at East Carolina University on April 22, 2015
interpreted to mean an infertile egg.
744
H. P. VAN KREY AND P. B. SIEGEL
Mortality. No male line effect was observed for embronic mortality for either generation. A significant female line difference (LW > HW) in mortality did occur in the S 14 generation but not in the S15 generation. Although reasons for this inconsistency are unknown, it was not due to the selective development of visibly detectable genetic lethals (i.e., lethals expressed relatively late in the course of the development). All dead embryos were carefully examined and classified with respect to age at death and discernible anatomical abnormalities. No consistent symptomatic or temperal trends were established. A randomized mortality pattern was observed suggesting that the incidence of detectable genetic lethals was not influencing the female line differences in mortality. Pre-oviposital and/or early post-oviposital mortality were also investigated because mortality during either of these periods may very easily be incorrectly interpreted as infertility. Line differences in mortality during these times could aid in explaining line differences in fertility. They would also indicate
whether or not there had been a correlated selection for lethal genes having an effect early in the course of embryonic development. To answer these questions, the adjunct experiment was designed. All the macroscopically infertile eggs were processed for a microscopic examination. Ninety such eggs wereexamined, of which 15.6% showed some degree of cellular development. There were, however, no differences between the various pure and reciprocal crosses; indicating male or female line differences in early acting genetic lethals did not exist among mating combinations. This latter information, along with the previously mentioned absence of genetic lethals acting late in the course of embryonic development, point out that 15 generations of divergent selection for somatogenesis has not led to the correlated selection for lethal genes affecting embryogenesis. REFERENCES Allen, C. J., and L. R. Champion, 1955. Competitive fertilization in the fowl. Poultry Sci. 34: 1332-1342. Edens, F. W., H. P. Van Krey and P. B. Siegel, 1973a. Selection for body weight at eight weeks of age. 9. Spermatozoal respiration. Poultry Sci. 52: 977-981. Edens, F. W., H. P. Van Krey and P. B. Siegel, 1973b. Selection for body weight at eight weeks of age. 10. Spermatozoal morphology. Poultry Sci. 52: 2287-2290. Hassan, G. M., and A. W. Nordskog, 1971. Effects of egg size and heterozygosis on embryonic growth and hatching speed. Genetics, 67: 279-285. 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. 41: 1439-1446. Jones, D. G., and W. F. Lamoreux, 1942. Semen production of White Leghorn males from strains selected for high and low fecundity. Poultry Sci. 21: 173-184. Lerner, I. M., 1954. Genetic Homostasis. John Wiley and Sons, New York. Maloney, M. A., J. C. Gilbreath, J. F. Tierce and R. D. Morrison, 1967. Divergent selection for twelve-week body weight in the domestic fowl. Poultry Sci. 46: 1116-1127. Marini, P. J., and B. L. Goodman, 1969. Semen
Downloaded from http://ps.oxfordjournals.org/ at East Carolina University on April 22, 2015
mination, and was not necessarily affecting fertility per se. The fertility data for females showed that the LW line consistently exceeded the HW line with respect to both levels of fertility and duration of fertility (Tables 2 and 3). While the trends were consistently in favor of the LW line females, differences between lines were significant in only four of the six comparisons. These data resemble somewhat those of Jones and Lamoreux (1942), who found that both sexes responded similarly to a unisexual selection program. As a result of the bisexual response, they concluded that semen production and egg production were expressions of comparable genotypes for high and low fecundity. In our experiment, it was found that the generalized response, reproductive fitness, was also similar for both sexes.
745
SELECTION FOR BODY W E I G H T
tability of semen quality, concentration and motility in White Rock roosters and their genetic correlation with rate of gain. Poultry Sci. 44: 1527-1529. Udale, R. W., P. B. Siegel and H. P. Van Krey, 1972. Rates of ovulation and oviposition in growth selected lines of chickens. Poultry Sci. 51: 20982100. Van Krey, H. P., P. B. Siegel and A. T. Leighton, Jr., 1971. Repeatability estimates and quantification of uterovaginal sperm-host gland numbers and population patterns. Biol. Reprod. 4: 31-34. van Tienhoven, A., and R. G. D. Steel, 1957. The effect of different diluents and dilution rates on fertilizing capacity of turkey semen. Poultry Sci. 36: 473-479. Verghese, M. N., and A. W. Nordskog, 1968. Correlated responses in reproductive fitness to selection in chickens. Genet. Res. 11: 221-238.
Lipovitellins in Fresh and Stored Shell Eggs ! ROBERT JOHN E V A N S , DORIS H . BAUER AND C A L J. FLEGAL
Departments of Biochemistry and Poultry Science, Michigan State University, East Lansing, 48823
Michigan
(Received for publication July 13, 1973)
ABSTRACT Lipovitellins were isolated from fresh eggs and from eggs which had been kept in cold storage for 6 months. No differences in structure were observed when studied by the procedure of progressive proteolytic digestion. Both the lipovitellins of fresh eggs and those of stored eggs were composed of 23% alpha-lipovitellin and 77% of beta-lipovitellin. No changes in lipids of the lipovitellins occurred during storage of the eggs. An increase in electrophoretic mobility of part of the lipovitellins was previously observed to occur during cold storage of shell eggs, but no changes were observed in lipovitellin during storage which would account for the change in electrophoretic properties of the lipovitellins. POULTRY SCIENCE 53: 745-750, 1974
INTRODUCTION
S
TUDIES of changes in the chemical composition of shell eggs during cold storage have been in progress at Michigan State University for about 25 years. Early studies of changes in egg proteins which occur during cold storage of shell eggs were made with the egg-white proteins because suitable
1. Michigan Agricultural Experiment Station Journal Article No. 6459 Supported in part by Public Health Service Grant AM 10214 from the National Institute of Arthritis and Metabolic Diseases.
procedures were not available for the study of egg yolk proteins (Evans et al., 1949). Evans et al. (1958) studied the distribution of proteins in the yolks of fresh and stored shell eggs, following the development of a procedure for separation of egg yolk proteins by paper electrophoresis (Evans and Bandemer, 1957). Yolk protein from 12-month old eggs appeared to contain less lipovitellin and more very low density lipoprotein than that from fresh eggs, and the very low density lipoprotein from 12-month old eggs moved almost twice as fast electrophoretically as
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