- Email: [email protected]
Extended Storage of Quail, Chicken, and Turkey Eggs
722
K . SlTTMANN, H . ABPLANALP AND U . K . ABBOTT
Sittmann, K., 1967. Pedigree analysis of apparent phenodeviants in Japanese quail. Genetics; 56: 590. Sittmann, K., H. Abplanalp and C. F. Meyerdick, 1971. Extended storage of quail, chicken, and turkey eggs. 1. Hatchability and embryonic mortality. Poultry Sci. 50: 681-688. Steinberg, A. G., 1959. Methodology in human
genetics. Am. J. Human Gen. 11: (2, part 2 ) : • -315-334. Steinke, L., 1967. Uber den Einfluss von Erschiitterungen auf die Brutfahigkeit von Huhnereiern. Arch. Gefliigelk. 3 1 : 94-110. Willis, R. A., 1962. The Borderland of Embryology and Pathology, 2nd Ed. London, Butterworths.
3. TERTIARY SEX RATIO IN QUAIL K. SITTMANN* AND H. ABPLANALP Department of Avian Sciences, University of California at Davis, Davis, California 95616 (Received for publication October 2, 1970) INTRODUCTION without turning
W
HILE analyzing observations on embryos in stored and unstored Japanese quail eggs, some trends in sex ratio became apparent that, to our knowledge, have not been reported before. MATERIALS AND METHODS
The quail used in this study belonged to generation 13 of line 908 which was maintained by pedigreed single-pair matings. Non-inbred progeny, i.e. controls, were produced by random matings among noninbred parents. Deliberately inbred progeny (F = 0.3125) were produced in the present trial by non-inbred parents in a cyclical mating system. Data from non-inbred progeny in the cyclical mating system were pooled with those of the controls. Eggs were collected daily for a total of five weeks starting March 2, 1966. At that time, birds were still recovering from a cold weather period which was reflected in substantial increases of egg production and fertility during the early weeks of the trial (Sittmann et al., 1971). Eggs were stored * Present address: Biology Department, McGill "University, Montreal 110, Quebec.
at 60°F. (15.5°C.) for less than one week at the poultry farm and then at 56°F. (13.3°C.) in the coldroom of the hatchery. Pre-incubation storage lasted from 4 to 38 days; this period was divided for the present analysis *into weekly intervals such that eggs of week 1, for example, had actually been stored for 4 to 10 days. Eggs were incubated for 18 days under routine hatchery conditions. They hatched April 26, 1966. Family size of chicks of weeks 1 and 2 was restricted at hatch by random culling to eight or, rarely, nine chicks. All chicks of week 3 were culled, but those of weeks 4 and 5 were banded to assess their post-hatch viability. Sex was determined only in birds surviving to five weeks of age by inspection of their plumage. Equality of the primary sex ratio is assumed for quail based on conclusive evidence for it in chickens. Sex ratios were very close to 50% in two studies involving hens with 100% fertility and 100% survival of progeny to either day 18 of incubation (Landauer, 1957), or to eight weeks post-hatch (Hays, 1945). These results have been confirmed by chromosomal analyses of 242 embryos at 16 hours of incuba-
Downloaded from http://ps.oxfordjournals.org/ at Swinburne University of Technology on May 15, 2015
Extended Storage of Quail, Chicken, and Turkey Eggs
723
EGG STORAGE AND SEX RATIO TABLE 1.—Post-hatch mortality to five weeks of age by holding lime and mating type Eggs stored for 4 and 5 weeks
Eggs stored for 1 and 2 weeks Mating type
Non-inbred Inbred**
Chicks hatched 724* 174
Cripple
Died
Total loss (%)
hatehed
20 6
33 26
7.3 18.4
139 23
Cri
PPle
Total loss (%)
Died
8 4
10.8 30.4
7 3
* Chicks remaining after 147 chicks were eliminated by random culling. ** F of parents=0%, F of chicks=31.25%.
RESULTS AND DISCUSSION
The increases in post-hatch mortality due to storage of hatching eggs beyond two weeks (Table 1) were statistically not significant. The following analysis concerns the 671 non-inbred survivors to five weeks that had hatched from eggs stored for two weeks or less. The 671 chicks had been produced by 109 single-pair matings. The deficiency of males in the total sample (48.1%, Table 2) was not significantly different from an even sex ratio. The sex ratio of chicks, however, was found to follow a specific trend when the 109 families were divided into four groups, W2 to W5, according to how long the oldest hatching egg of a given full-sib
family had been stored (Table 2). For example, each of the 33 families in group W3 had at least one chick hatching in week three of storage but none in weeks four and five. The four groups of families were alike in several respects: hatchability (x2 = 6.01, df = 3, p = .11), proportion of random culls (x2 = 2.56, df = 3, p > .05), and proportion of cripples or chicks that died after hatching ( x 2 = 1.91, df = 3, p > .05). In contrast, the sex ratio was heterogeneous among the four groups (xh2 = 9-34, df = 1, p < .01); there was a highly significant trend (x2 = 8.86, p < .01) from an excess of females in W2 families (x2 = 3.61, p = .06) to an excess of males in W5 families (x2 = 3.07, p = .08). Thus, the tertiary sex ratio in full-sib families was clearly related to the maximum length of storage tolerated by chicks of these families. The failure of a family in groups W2, W3, and W4 to have had a chick hatching after storage for more than 2, 3, or 4 weeks, respectively, may be attributed to either the parents or the offspring. This could be
TABLE 2.—Hatchability, post-hatch mortality, and tertiary sex ratio of non-inbred quail hatched from eggs that were stored for two weeks or less. Families are grouped according to the week of storage with the oldest egg that hatched Hatchability Eggs fertile Group Number Number % Families
Random culls
Crippled
Number
%
Survivors
Sex Males Females ratio
%
Number
W2 W3 W4 W5
22 33 38 16
219 362 403 166
157 276 319 119
71.7 76.2 79.2 71.7
23 54 53 17
14.6 19.6 16.6 14.3
12 18 15 8
7.6 6.5 4.7 6.7
50 90 127 56
72 114 124 38
41.0 44.1 50.6 59.6
Total
109
1150
871
75.7
147
16.9
53
6.1
323
348
48.1
Downloaded from http://ps.oxfordjournals.org/ at Swinburne University of Technology on May 15, 2015
tion of which 122 were males (Fechheimer etal., 196&). Chi-squares for trends were calculated with one degree of freedom according to Armitage (19SS); contingency chi-squares with one degree of freedom include Yates' correction for continuity.
724
K . SlTTMANN AND H . ABPLANALP TABLE 3.—Sex ratio of quail hatching from eggs stored for two weeks or less. Data of Table 2 divided according to whether failure of a family to hatch a chick after longer storage was due to the parents or to the offspring Parents Number of families
2 3 4
6 13 11
Total
30
Embryo
Sex ratio
Sex ratio
(%)
Number of families
32
22 54 40
33.3 37.9 44.4
16 20 27
39 57 95
50 60 84
43.8 48.7 53.1
76
116
39.6
63
191
194
49.6
Males Females 11
Males Females
(%)
done unequivocally in case of the dam when no eggs were produced in earlier weeks (14 families) and in case of offspring when fertile eggs were present none of which had hatched (63 families). The failure was attributed to the sire (16 families) when none of the eggs present prior to the week with the oldest hatching egg was fertile; this category may include some cases of very early embryonic mortality in eggs that were classified as infertile. Total sex ratio did not differ significantly between the two parental categories (x2 = 0.458, p > .05) which were, therefore, combined. Table 3 shows that the overall trend in sex ratio was present in both sets which differed significantly in total sex ratio (x2 = 4.786, p = .02). The tendency towards an excess of females was consistently stronger when the failure of hatching a chick after prolonged storage was due to the parents; thus, the parents' reproductive state appears to have influenced the tertiary sex ratio of chicks emerging from their eggs, presum-
ably by means of a sex differential in embryonic mortality. Arrangement of the 671 chicks into families that either did or did not survive intact from hatching to five weeks of age (Table 4) shows that post-hatch losses likely involved more females than males. This effect too was of the same magnitude in the four groups of families. Thus, the observed trend in sex ratio over the four groups of families cannot be explained by differential post-hatch mortality of chicks. The 671 chicks were also arranged according to family size at hatch (Table 5). Large families had a higher percentage of females and this was true in all four groups. In large families high hatchability was combined with a significant excess over 50% of females ( x 2 = 4.22, p < .05); this led to the conclusion that females were better able to hatch than males within the 18-day incubation period used in this study. An excess of females at hatch is inferred
TABLE 4.—Sex ratio in groups of families arranged according to presence or absence of post-hatch losses
TABLE 5.—Sex ratio in groups of families arranged by family size at hatch
Groups of families
Crippled and Survivors dead chicks per family Males Females
Sex ratio
Random culls
Groups
Number of Family Number of sizes families Males Females
Sex ratio
Hatchability
(%)
(%)
(%)
(%)
W2+W3
0 >1
75 65
108 78
41.0 45.5
19.7 15.6
W2+W3
1-8 9-14
31 24
68 72
75 111
47.6 39.3
60.2 87.7
W4+W5
0 >1
129 54
121 41
51.6 56.8
15.8 16.3
W5+W5
1-8 9-14
28 26
86 97
63 99
57.7 49.5
65.2 86.0
Total
0 >1
204 119
229 119
47.1 50.0
16.7 17.1
Total
1-8 9-14
59 50
154 169
138 210
52.7 44.6
62.5 86.7
Downloaded from http://ps.oxfordjournals.org/ at Swinburne University of Technology on May 15, 2015
Oldest chick hatched in week of storage
EGG STORAGE AND SEX RATIO
It is apparent that the sex ratio varied considerably between families produced by different pair matings. A greater proportion of females hatched from conventionally stored eggs in families in which hatchability of stored eggs was low than in families in which hatchability of stored eggs was high. Inbred quail showed a similar trend. The cause of this relationship would seem to lie in the more rapid development of female quail embryos.
ACKNOWLEDGEMENT
This work was supported in part by U.S. Public Health Services grant TIGM 701-04 /05. The authors acknowledge the competent assistance of C. F. Meyerdick and Lynn Kaplansky. REFERENCES Armitage, P., 1955. Tests for linear trends in proportions and frequencies. Biometrics, 11: 375386. Fechheimer, N. S., D. L. Zartman and R. G. Jaap, 1968. Estimates of the primary and subsequent embryonic sex ratios in the chicken. VI e Cong. Intern. Reprod. Anim. Insem. Artif., Paris, 1: 417-419. Hays, F. A., 1945. The primary sex ratio in domestic chickens. Am. Nat. 79: 184-186. Homma, K., T. D. Siopes, W. O. Wilson and L. Z. McFarland, 1966. Identification of sex of dayold quail (Coturnix coturnix japonica) by cloacal examination. Poultry Sci. 45: 469-472. Ichinoe, K., E. Ohta and S. Suzuki, 1968. The relation between the hatching time and the sex-ratio in chicks. III. Distribution of the hatching time in relation to the age of breeding stock and the season. Jap. Poultry Sci. 5: 190-197. Landauer, W., 1957. Primary sex ratio of fowl. Nature, 180: 1139-1140. Landauer, W., 1967. The hatchability of chicken eggs as influenced by evnironment and heredity. Storrs. Agric. Exp. Sta. Monograph 1 (Revised). MacLaury, D. W., and W. M. Insko, 1968. Relation of pre-incubation factors and post-hatching performance to length of incubation period. 2. Relation of length of incubation period to posthatching performance. Poultry Sci. 48: 330336. Sittmann, K., H. Abplanalp and C. F. Meyerdick, 1971. Extended storage of quail, chicken, and turkey eggs. 1. Hatchability and embryonic mortality. Poultry Sci. 50: 681-688. Sittmann, K., W. O. Wilson and L. Z. McFarland, 1966. Buff and albino Japanese quail: Description, inheritance, and fitness traits. J. Heredity, 57: 119-124.
JULY 4-8. TWENTY-FIRST ANNUAL MEETING, CANADIAN SOCIETY OF ANIMAL PRODUCTION, LETHBRIDGE, ALBERTA
Downloaded from http://ps.oxfordjournals.org/ at Swinburne University of Technology on May 15, 2015
from the tertiary ratio of 48.1% (Table 2) combined with the presumed higher female than male post-hatch mortality. In contrast, Homraa et al. (1966) working in the same laboratory and with stocks in part closely related to ours, observed an excess of males (52.51%, p < .025) among 2453 hatched quail chicks. The difference in results may be due to the fact that in some trials of Homma et al. (1966) eggs were incubated one day longer than in our case thus permitting more males to emerge; it will be argued elsewhere that in quail, as in chickens (Landauer, 1967, p. 185; MacLaury and Insko, 1968; Ichinoe et al. 1968), males are generally slower to hatch than females. Secondly, some of the sires of the Oklahoma stock of Homma et al. (1966) may have been segregating for imperfect albinism, a sex-linked condition which reduces hatchability (Sittmann et al., 1966), resulting in a deficiency of daughters at hatch. Finally, part of the difference between our result and that of Homma et al. (1966) may be real, since Ichinoe et al. (1968) have shown that season and parental age affect developmental rates of male and female embryos as well as the secondary sex ratio in a strain-specific manner.
725
K . SlTTMANN, H . ABPLANALP AND U . K . ABBOTT
Sittmann, K., 1967. Pedigree analysis of apparent phenodeviants in Japanese quail. Genetics; 56: 590. Sittmann, K., H. Abplanalp and C. F. Meyerdick, 1971. Extended storage of quail, chicken, and turkey eggs. 1. Hatchability and embryonic mortality. Poultry Sci. 50: 681-688. Steinberg, A. G., 1959. Methodology in human
genetics. Am. J. Human Gen. 11: (2, part 2 ) : • -315-334. Steinke, L., 1967. Uber den Einfluss von Erschiitterungen auf die Brutfahigkeit von Huhnereiern. Arch. Gefliigelk. 3 1 : 94-110. Willis, R. A., 1962. The Borderland of Embryology and Pathology, 2nd Ed. London, Butterworths.
3. TERTIARY SEX RATIO IN QUAIL K. SITTMANN* AND H. ABPLANALP Department of Avian Sciences, University of California at Davis, Davis, California 95616 (Received for publication October 2, 1970) INTRODUCTION without turning
W
HILE analyzing observations on embryos in stored and unstored Japanese quail eggs, some trends in sex ratio became apparent that, to our knowledge, have not been reported before. MATERIALS AND METHODS
The quail used in this study belonged to generation 13 of line 908 which was maintained by pedigreed single-pair matings. Non-inbred progeny, i.e. controls, were produced by random matings among noninbred parents. Deliberately inbred progeny (F = 0.3125) were produced in the present trial by non-inbred parents in a cyclical mating system. Data from non-inbred progeny in the cyclical mating system were pooled with those of the controls. Eggs were collected daily for a total of five weeks starting March 2, 1966. At that time, birds were still recovering from a cold weather period which was reflected in substantial increases of egg production and fertility during the early weeks of the trial (Sittmann et al., 1971). Eggs were stored * Present address: Biology Department, McGill "University, Montreal 110, Quebec.
at 60°F. (15.5°C.) for less than one week at the poultry farm and then at 56°F. (13.3°C.) in the coldroom of the hatchery. Pre-incubation storage lasted from 4 to 38 days; this period was divided for the present analysis *into weekly intervals such that eggs of week 1, for example, had actually been stored for 4 to 10 days. Eggs were incubated for 18 days under routine hatchery conditions. They hatched April 26, 1966. Family size of chicks of weeks 1 and 2 was restricted at hatch by random culling to eight or, rarely, nine chicks. All chicks of week 3 were culled, but those of weeks 4 and 5 were banded to assess their post-hatch viability. Sex was determined only in birds surviving to five weeks of age by inspection of their plumage. Equality of the primary sex ratio is assumed for quail based on conclusive evidence for it in chickens. Sex ratios were very close to 50% in two studies involving hens with 100% fertility and 100% survival of progeny to either day 18 of incubation (Landauer, 1957), or to eight weeks post-hatch (Hays, 1945). These results have been confirmed by chromosomal analyses of 242 embryos at 16 hours of incuba-
Downloaded from http://ps.oxfordjournals.org/ at Swinburne University of Technology on May 15, 2015
Extended Storage of Quail, Chicken, and Turkey Eggs
723
EGG STORAGE AND SEX RATIO TABLE 1.—Post-hatch mortality to five weeks of age by holding lime and mating type Eggs stored for 4 and 5 weeks
Eggs stored for 1 and 2 weeks Mating type
Non-inbred Inbred**
Chicks hatched 724* 174
Cripple
Died
Total loss (%)
hatehed
20 6
33 26
7.3 18.4
139 23
Cri
PPle
Total loss (%)
Died
8 4
10.8 30.4
7 3
* Chicks remaining after 147 chicks were eliminated by random culling. ** F of parents=0%, F of chicks=31.25%.
RESULTS AND DISCUSSION
The increases in post-hatch mortality due to storage of hatching eggs beyond two weeks (Table 1) were statistically not significant. The following analysis concerns the 671 non-inbred survivors to five weeks that had hatched from eggs stored for two weeks or less. The 671 chicks had been produced by 109 single-pair matings. The deficiency of males in the total sample (48.1%, Table 2) was not significantly different from an even sex ratio. The sex ratio of chicks, however, was found to follow a specific trend when the 109 families were divided into four groups, W2 to W5, according to how long the oldest hatching egg of a given full-sib
family had been stored (Table 2). For example, each of the 33 families in group W3 had at least one chick hatching in week three of storage but none in weeks four and five. The four groups of families were alike in several respects: hatchability (x2 = 6.01, df = 3, p = .11), proportion of random culls (x2 = 2.56, df = 3, p > .05), and proportion of cripples or chicks that died after hatching ( x 2 = 1.91, df = 3, p > .05). In contrast, the sex ratio was heterogeneous among the four groups (xh2 = 9-34, df = 1, p < .01); there was a highly significant trend (x2 = 8.86, p < .01) from an excess of females in W2 families (x2 = 3.61, p = .06) to an excess of males in W5 families (x2 = 3.07, p = .08). Thus, the tertiary sex ratio in full-sib families was clearly related to the maximum length of storage tolerated by chicks of these families. The failure of a family in groups W2, W3, and W4 to have had a chick hatching after storage for more than 2, 3, or 4 weeks, respectively, may be attributed to either the parents or the offspring. This could be
TABLE 2.—Hatchability, post-hatch mortality, and tertiary sex ratio of non-inbred quail hatched from eggs that were stored for two weeks or less. Families are grouped according to the week of storage with the oldest egg that hatched Hatchability Eggs fertile Group Number Number % Families
Random culls
Crippled
Number
%
Survivors
Sex Males Females ratio
%
Number
W2 W3 W4 W5
22 33 38 16
219 362 403 166
157 276 319 119
71.7 76.2 79.2 71.7
23 54 53 17
14.6 19.6 16.6 14.3
12 18 15 8
7.6 6.5 4.7 6.7
50 90 127 56
72 114 124 38
41.0 44.1 50.6 59.6
Total
109
1150
871
75.7
147
16.9
53
6.1
323
348
48.1
Downloaded from http://ps.oxfordjournals.org/ at Swinburne University of Technology on May 15, 2015
tion of which 122 were males (Fechheimer etal., 196&). Chi-squares for trends were calculated with one degree of freedom according to Armitage (19SS); contingency chi-squares with one degree of freedom include Yates' correction for continuity.
724
K . SlTTMANN AND H . ABPLANALP TABLE 3.—Sex ratio of quail hatching from eggs stored for two weeks or less. Data of Table 2 divided according to whether failure of a family to hatch a chick after longer storage was due to the parents or to the offspring Parents Number of families
2 3 4
6 13 11
Total
30
Embryo
Sex ratio
Sex ratio
(%)
Number of families
32
22 54 40
33.3 37.9 44.4
16 20 27
39 57 95
50 60 84
43.8 48.7 53.1
76
116
39.6
63
191
194
49.6
Males Females 11
Males Females
(%)
done unequivocally in case of the dam when no eggs were produced in earlier weeks (14 families) and in case of offspring when fertile eggs were present none of which had hatched (63 families). The failure was attributed to the sire (16 families) when none of the eggs present prior to the week with the oldest hatching egg was fertile; this category may include some cases of very early embryonic mortality in eggs that were classified as infertile. Total sex ratio did not differ significantly between the two parental categories (x2 = 0.458, p > .05) which were, therefore, combined. Table 3 shows that the overall trend in sex ratio was present in both sets which differed significantly in total sex ratio (x2 = 4.786, p = .02). The tendency towards an excess of females was consistently stronger when the failure of hatching a chick after prolonged storage was due to the parents; thus, the parents' reproductive state appears to have influenced the tertiary sex ratio of chicks emerging from their eggs, presum-
ably by means of a sex differential in embryonic mortality. Arrangement of the 671 chicks into families that either did or did not survive intact from hatching to five weeks of age (Table 4) shows that post-hatch losses likely involved more females than males. This effect too was of the same magnitude in the four groups of families. Thus, the observed trend in sex ratio over the four groups of families cannot be explained by differential post-hatch mortality of chicks. The 671 chicks were also arranged according to family size at hatch (Table 5). Large families had a higher percentage of females and this was true in all four groups. In large families high hatchability was combined with a significant excess over 50% of females ( x 2 = 4.22, p < .05); this led to the conclusion that females were better able to hatch than males within the 18-day incubation period used in this study. An excess of females at hatch is inferred
TABLE 4.—Sex ratio in groups of families arranged according to presence or absence of post-hatch losses
TABLE 5.—Sex ratio in groups of families arranged by family size at hatch
Groups of families
Crippled and Survivors dead chicks per family Males Females
Sex ratio
Random culls
Groups
Number of Family Number of sizes families Males Females
Sex ratio
Hatchability
(%)
(%)
(%)
(%)
W2+W3
0 >1
75 65
108 78
41.0 45.5
19.7 15.6
W2+W3
1-8 9-14
31 24
68 72
75 111
47.6 39.3
60.2 87.7
W4+W5
0 >1
129 54
121 41
51.6 56.8
15.8 16.3
W5+W5
1-8 9-14
28 26
86 97
63 99
57.7 49.5
65.2 86.0
Total
0 >1
204 119
229 119
47.1 50.0
16.7 17.1
Total
1-8 9-14
59 50
154 169
138 210
52.7 44.6
62.5 86.7
Downloaded from http://ps.oxfordjournals.org/ at Swinburne University of Technology on May 15, 2015
Oldest chick hatched in week of storage
EGG STORAGE AND SEX RATIO
It is apparent that the sex ratio varied considerably between families produced by different pair matings. A greater proportion of females hatched from conventionally stored eggs in families in which hatchability of stored eggs was low than in families in which hatchability of stored eggs was high. Inbred quail showed a similar trend. The cause of this relationship would seem to lie in the more rapid development of female quail embryos.
ACKNOWLEDGEMENT
This work was supported in part by U.S. Public Health Services grant TIGM 701-04 /05. The authors acknowledge the competent assistance of C. F. Meyerdick and Lynn Kaplansky. REFERENCES Armitage, P., 1955. Tests for linear trends in proportions and frequencies. Biometrics, 11: 375386. Fechheimer, N. S., D. L. Zartman and R. G. Jaap, 1968. Estimates of the primary and subsequent embryonic sex ratios in the chicken. VI e Cong. Intern. Reprod. Anim. Insem. Artif., Paris, 1: 417-419. Hays, F. A., 1945. The primary sex ratio in domestic chickens. Am. Nat. 79: 184-186. Homma, K., T. D. Siopes, W. O. Wilson and L. Z. McFarland, 1966. Identification of sex of dayold quail (Coturnix coturnix japonica) by cloacal examination. Poultry Sci. 45: 469-472. Ichinoe, K., E. Ohta and S. Suzuki, 1968. The relation between the hatching time and the sex-ratio in chicks. III. Distribution of the hatching time in relation to the age of breeding stock and the season. Jap. Poultry Sci. 5: 190-197. Landauer, W., 1957. Primary sex ratio of fowl. Nature, 180: 1139-1140. Landauer, W., 1967. The hatchability of chicken eggs as influenced by evnironment and heredity. Storrs. Agric. Exp. Sta. Monograph 1 (Revised). MacLaury, D. W., and W. M. Insko, 1968. Relation of pre-incubation factors and post-hatching performance to length of incubation period. 2. Relation of length of incubation period to posthatching performance. Poultry Sci. 48: 330336. Sittmann, K., H. Abplanalp and C. F. Meyerdick, 1971. Extended storage of quail, chicken, and turkey eggs. 1. Hatchability and embryonic mortality. Poultry Sci. 50: 681-688. Sittmann, K., W. O. Wilson and L. Z. McFarland, 1966. Buff and albino Japanese quail: Description, inheritance, and fitness traits. J. Heredity, 57: 119-124.
JULY 4-8. TWENTY-FIRST ANNUAL MEETING, CANADIAN SOCIETY OF ANIMAL PRODUCTION, LETHBRIDGE, ALBERTA
Downloaded from http://ps.oxfordjournals.org/ at Swinburne University of Technology on May 15, 2015
from the tertiary ratio of 48.1% (Table 2) combined with the presumed higher female than male post-hatch mortality. In contrast, Homraa et al. (1966) working in the same laboratory and with stocks in part closely related to ours, observed an excess of males (52.51%, p < .025) among 2453 hatched quail chicks. The difference in results may be due to the fact that in some trials of Homma et al. (1966) eggs were incubated one day longer than in our case thus permitting more males to emerge; it will be argued elsewhere that in quail, as in chickens (Landauer, 1967, p. 185; MacLaury and Insko, 1968; Ichinoe et al. 1968), males are generally slower to hatch than females. Secondly, some of the sires of the Oklahoma stock of Homma et al. (1966) may have been segregating for imperfect albinism, a sex-linked condition which reduces hatchability (Sittmann et al., 1966), resulting in a deficiency of daughters at hatch. Finally, part of the difference between our result and that of Homma et al. (1966) may be real, since Ichinoe et al. (1968) have shown that season and parental age affect developmental rates of male and female embryos as well as the secondary sex ratio in a strain-specific manner.
725