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Research Note: Hatching Time, Body Weight, and Thyroid Hormones in Male and Female Chicks from Lines Selected for High or Low Juvenile Body Weight
Research Note: Hatching Time, Body Weight, and Thyroid Hormones in Male and Female Chicks from Lines Selected for High or Low Juvenile Body Weight E. A. DUNNINGTON, P. B. SIEGEL, and F.M.A. MCNABB1 Poultry Science Department, and Biology Department, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061
1993 Poultry Science 72:1998-2000
INTRODUCTION
embryos are known to reach perinatal stages AC (pipped through the air cell), TS Several studies have been reported in (pipped through the shell), and H (hatched) which female chicken embryos hatch at 12, 7, and 5 h earlier than Line HW earlier than males during artificial incuba- embryos (EHrnnington et ah, 1992). tion (Hays, 1941; Zawalsky, 1962; Burke, For this experiment, all eggs were from 1992). Burke (1992) summarized conflict- age-contemporary parents (semen was ing results on whether there is a difference pooled within each line and dams were between sexes for body weight during artificially inseminated) and were inincubation and at hatching. The objective cubated in one machine. On Day 17 of of this study was to evaluate whether incubation, nine groups of 25 fertile eggs there were differences between sexes in from each line were placed in separate length of time from start of incubation to hatching trays and transferred to a hatcher. hatch, in body weights, or plasma triiodo- Eggs were sampled at the following times: thyronine (T3) and thyroxine (T4) in two 468,474,480,492,498,504,516,522, and 528 lines of chickens known to differ in h of incubation. At each sampling, one hatching times. group of eggs from each line was removed from the incubator, and each egg was classified as not pipped (NP), AC, TS, or H. MATERIALS AND METHODS Then sex and body weight (with yolk sac at all stages and without yolk sac at all stages Stocks and Sampling except H) of each embryo or chick were Embryos and chicks used in this experi- recorded, and individual blood samples ment were from the 32nd generation of were obtained for determination of plasma White Plymouth Rocks selected for high T3 and T4. Hormone concentrations were (HW) or low (LW) body weight at 8 wk of determined by RIA as described in McNabb age (Dunnington and Siegel, 1985). Line LW et al. (1989). Statistical Analyses Received for publication March 17, 1993. Accepted for publication June 15, 1993. 1 Biology Department.
Numbers of males and females reaching each perinatal stage were compared by 1998
Downloaded from http://ps.oxfordjournals.org/ at East Tennessee State University on June 23, 2015
ABSTRACT Comparisons between males and females were made for length of time from start of incubation to perinatal stages of hatching, body weight, and thyroid hormones in lines of chickens selected for high (HW) or low (LW) juvenile body weight. Although males appeared to pip through the air cell and through the shell earlier than females in Line LW, there were no consistent differences between the sexes in time to hatch in either line. Body weights and plasma triiodothyronine and thyroxine were not different for males and females at any stage. (Key words: hatching time, triiodothyronine, thyroxine, selection, body weight)
RESEARCH NOTE 100
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FIGURE 1. Percentages of male ( ) and female (—) embryos and chicks from the high-weight (•) and low-weight (A) lines at the following perinatal stages: pipped through the air cell (AC), pipped through the shell (TS), and hatched (H). There were no differences between males and females at any stage for these traits.
calculating percentage of total to reach the stage at each sampling time. Calculations were done for each line by sex by incubation stage group. For body weights and plasma T3 and T4, data were analyzed by ANOVA with line, sex, and incubation stage (NP, AC, TS, and H) as main effects along with interactions. Body weights were transformed to common logarithms prior to analyses.
**
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505 INCUBATION
-^-•-
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—•—«b
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TS Stage
P 3
RESULTS AND DISCUSSION
For each line by sex by incubation stage group, percentages of individuals reaching that stage are shown in Figure 1. Line LW embryos reached all perinatal stages and hatched earlier than Line HW chicks, as reported previously (Dunnington et ah, 1992). In general, within Line LW males reached stages AC and TS slightly earlier than females, and there were no consistent differences between sexes in Stage H for either line. Although there were no differences in body weights between the sexes, embryos and chicks from Line HW were consistently heavier than those from Line LW (Figure 2, top panel). These results were consistent with those of Anthony et al. (1989). In both lines the heaviest body weights (inclusive of yolk sac) occurred in
FIGURE 2. Body weights (top panel) in grams, plasma triiodothyronine [T3 (middle panel)] in nanograms per milliliter, and plasma thyroxine [T4 (bottom panel)] in nanograms per milliliter, for highweight (•) and low-weight (A) males (—) and females (—) at the following perinatal stages: not pipped (NP), pipped through the air cell (AC), pipped through the shell (TS), and hatched (H). Means on a line with no common letters differ significantly (P < .05). **Means of high-weight and low-weight lines at the same incubation stage are significantly different (P < .01).
Downloaded from http://ps.oxfordjournals.org/ at East Tennessee State University on June 23, 2015
490 HOURS OF
c
JL_-*~
2000
DUNNINGTON ET AL.
ACKNOWLEDGMENTS
The authors wish to thank T. Freeman, S. Suvarna, Aram Neuschatz, and N. O'Sullivan for their help in sampling and laboratory procedures. The project was supported in part by USDA grant Number 88-37265-3789.
REFERENCES Anthony, N. B., E. A. Dunnington, and P. B. Siegel, 1989. Embryo growth of normal and dwarf chickens from lines selected for high and low 56-day body weight. Arch. Gefltlgelkd. 53: 116-122. Burke, W. H., 1992. Sex differences in incubation length and hatching weights of broiler chicks. Poultry Sci. 71:1933-1938. Dunnington, E. A., and P. B. Siegel, 1985. Long-term selection for 8-week body weight in chickens— Direct and correlated responses. Theoret. Appl. Genet. 71:305-313. Dunnington, E. A., F.M.A. McNabb, T. B. Freeman, N. O'Sullivan, and P. B. Siegel, 1992. Genetic analyses of incubation time in weight-selected lines of chickens and their crosses. Arch. Gefltlgelkd. 56:77-80. Hays, F. A., 1941. The importance of the length of incubation period in Rhode Island Reds. Massachusetts Agricultural Experiment Station Bulletin No. 384, Amherst, MA. McNabb, F.M.A., E. A. Dunnington, T. B. Freeman, and P. B. Siegel, 1989. Thyroid hormones and growth patterns of embryonic and posthatch chickens from lines selected for high and low juvenile body weight. Growth, Develop. Aging 53:87-92. McNabb, F.M.A., E. A. Dunnington, P. B. Siegel, and S. Suvarna, 1993. Perinatal thyroid hormones and hepatic 5'deiodinase in relation to hatching time in weight-selected lines of chickens. Poultry Sci. 72:1764-1771. Zawalsky, M., 1962. The effect of sex, egg weight and preincubation storage on hatching time and chick weight. Poultry Sci. 41:1697.(Abstr.)
Downloaded from http://ps.oxfordjournals.org/ at East Tennessee State University on June 23, 2015
the TS stage of incubation. None of the interactions were significant. When body weight without yolk sac was analyzed (for the three incubation stages NP, AC, and TS), there were no differences between the sexes, but Line HW embryos were heavier than Line LW embryos (data not shown). Embryos of both lines, however, were heavier in the AC stage than NP or TS stages. Again, there were no interactions. For both T3 and T4 concentrations, there were no differences due to sex, and no interactions involving sex were significant. There were significant differences in T3 and T4 due to line and stage of incubation. There was also a significant line by stage interaction (Figure 2, middle and bottom panels), agreeing with previous results for these lines (McNabb et al., 1993). Line LW embryos had higher T3 and T4 values than Line HW embryos at all prehatching stages. For hatchlings, T3 concentrations were higher in Line LW than Line HW, but there was no difference in T4 concentrations. Peak plasma T3 and T4 occurred in the TS stage for embryos of both lines. This experiment used lines of chickens known to differ quantitatively and temporally in the traits measured but not previously investigated for possible differences between the sexes in these traits. The study shows that there were no consistent differences between the sexes within these lines for time to hatch, body weight at hatch, or amounts of plasma T3 and T4 at various stages of hatching.
1993 Poultry Science 72:1998-2000
INTRODUCTION
embryos are known to reach perinatal stages AC (pipped through the air cell), TS Several studies have been reported in (pipped through the shell), and H (hatched) which female chicken embryos hatch at 12, 7, and 5 h earlier than Line HW earlier than males during artificial incuba- embryos (EHrnnington et ah, 1992). tion (Hays, 1941; Zawalsky, 1962; Burke, For this experiment, all eggs were from 1992). Burke (1992) summarized conflict- age-contemporary parents (semen was ing results on whether there is a difference pooled within each line and dams were between sexes for body weight during artificially inseminated) and were inincubation and at hatching. The objective cubated in one machine. On Day 17 of of this study was to evaluate whether incubation, nine groups of 25 fertile eggs there were differences between sexes in from each line were placed in separate length of time from start of incubation to hatching trays and transferred to a hatcher. hatch, in body weights, or plasma triiodo- Eggs were sampled at the following times: thyronine (T3) and thyroxine (T4) in two 468,474,480,492,498,504,516,522, and 528 lines of chickens known to differ in h of incubation. At each sampling, one hatching times. group of eggs from each line was removed from the incubator, and each egg was classified as not pipped (NP), AC, TS, or H. MATERIALS AND METHODS Then sex and body weight (with yolk sac at all stages and without yolk sac at all stages Stocks and Sampling except H) of each embryo or chick were Embryos and chicks used in this experi- recorded, and individual blood samples ment were from the 32nd generation of were obtained for determination of plasma White Plymouth Rocks selected for high T3 and T4. Hormone concentrations were (HW) or low (LW) body weight at 8 wk of determined by RIA as described in McNabb age (Dunnington and Siegel, 1985). Line LW et al. (1989). Statistical Analyses Received for publication March 17, 1993. Accepted for publication June 15, 1993. 1 Biology Department.
Numbers of males and females reaching each perinatal stage were compared by 1998
Downloaded from http://ps.oxfordjournals.org/ at East Tennessee State University on June 23, 2015
ABSTRACT Comparisons between males and females were made for length of time from start of incubation to perinatal stages of hatching, body weight, and thyroid hormones in lines of chickens selected for high (HW) or low (LW) juvenile body weight. Although males appeared to pip through the air cell and through the shell earlier than females in Line LW, there were no consistent differences between the sexes in time to hatch in either line. Body weights and plasma triiodothyronine and thyroxine were not different for males and females at any stage. (Key words: hatching time, triiodothyronine, thyroxine, selection, body weight)
RESEARCH NOTE 100
AC
'y^r^
x^ TS
z o
A
r
50
<
1999
50-
'/
4i
*-
a
" "
UJ Q.
a 40-
H
~*j
/^ '
50
0
• a1*"**
-
i
FIGURE 1. Percentages of male ( ) and female (—) embryos and chicks from the high-weight (•) and low-weight (A) lines at the following perinatal stages: pipped through the air cell (AC), pipped through the shell (TS), and hatched (H). There were no differences between males and females at any stage for these traits.
calculating percentage of total to reach the stage at each sampling time. Calculations were done for each line by sex by incubation stage group. For body weights and plasma T3 and T4, data were analyzed by ANOVA with line, sex, and incubation stage (NP, AC, TS, and H) as main effects along with interactions. Body weights were transformed to common logarithms prior to analyses.
**
**
**
** 30
a
ab ab
b
*S
35-
i
505 INCUBATION
-^-•-
—BK=-
*—-
—•—«b
?5AC
TS Stage
P 3
RESULTS AND DISCUSSION
For each line by sex by incubation stage group, percentages of individuals reaching that stage are shown in Figure 1. Line LW embryos reached all perinatal stages and hatched earlier than Line HW chicks, as reported previously (Dunnington et ah, 1992). In general, within Line LW males reached stages AC and TS slightly earlier than females, and there were no consistent differences between sexes in Stage H for either line. Although there were no differences in body weights between the sexes, embryos and chicks from Line HW were consistently heavier than those from Line LW (Figure 2, top panel). These results were consistent with those of Anthony et al. (1989). In both lines the heaviest body weights (inclusive of yolk sac) occurred in
FIGURE 2. Body weights (top panel) in grams, plasma triiodothyronine [T3 (middle panel)] in nanograms per milliliter, and plasma thyroxine [T4 (bottom panel)] in nanograms per milliliter, for highweight (•) and low-weight (A) males (—) and females (—) at the following perinatal stages: not pipped (NP), pipped through the air cell (AC), pipped through the shell (TS), and hatched (H). Means on a line with no common letters differ significantly (P < .05). **Means of high-weight and low-weight lines at the same incubation stage are significantly different (P < .01).
Downloaded from http://ps.oxfordjournals.org/ at East Tennessee State University on June 23, 2015
490 HOURS OF
c
JL_-*~
2000
DUNNINGTON ET AL.
ACKNOWLEDGMENTS
The authors wish to thank T. Freeman, S. Suvarna, Aram Neuschatz, and N. O'Sullivan for their help in sampling and laboratory procedures. The project was supported in part by USDA grant Number 88-37265-3789.
REFERENCES Anthony, N. B., E. A. Dunnington, and P. B. Siegel, 1989. Embryo growth of normal and dwarf chickens from lines selected for high and low 56-day body weight. Arch. Gefltlgelkd. 53: 116-122. Burke, W. H., 1992. Sex differences in incubation length and hatching weights of broiler chicks. Poultry Sci. 71:1933-1938. Dunnington, E. A., and P. B. Siegel, 1985. Long-term selection for 8-week body weight in chickens— Direct and correlated responses. Theoret. Appl. Genet. 71:305-313. Dunnington, E. A., F.M.A. McNabb, T. B. Freeman, N. O'Sullivan, and P. B. Siegel, 1992. Genetic analyses of incubation time in weight-selected lines of chickens and their crosses. Arch. Gefltlgelkd. 56:77-80. Hays, F. A., 1941. The importance of the length of incubation period in Rhode Island Reds. Massachusetts Agricultural Experiment Station Bulletin No. 384, Amherst, MA. McNabb, F.M.A., E. A. Dunnington, T. B. Freeman, and P. B. Siegel, 1989. Thyroid hormones and growth patterns of embryonic and posthatch chickens from lines selected for high and low juvenile body weight. Growth, Develop. Aging 53:87-92. McNabb, F.M.A., E. A. Dunnington, P. B. Siegel, and S. Suvarna, 1993. Perinatal thyroid hormones and hepatic 5'deiodinase in relation to hatching time in weight-selected lines of chickens. Poultry Sci. 72:1764-1771. Zawalsky, M., 1962. The effect of sex, egg weight and preincubation storage on hatching time and chick weight. Poultry Sci. 41:1697.(Abstr.)
Downloaded from http://ps.oxfordjournals.org/ at East Tennessee State University on June 23, 2015
the TS stage of incubation. None of the interactions were significant. When body weight without yolk sac was analyzed (for the three incubation stages NP, AC, and TS), there were no differences between the sexes, but Line HW embryos were heavier than Line LW embryos (data not shown). Embryos of both lines, however, were heavier in the AC stage than NP or TS stages. Again, there were no interactions. For both T3 and T4 concentrations, there were no differences due to sex, and no interactions involving sex were significant. There were significant differences in T3 and T4 due to line and stage of incubation. There was also a significant line by stage interaction (Figure 2, middle and bottom panels), agreeing with previous results for these lines (McNabb et al., 1993). Line LW embryos had higher T3 and T4 values than Line HW embryos at all prehatching stages. For hatchlings, T3 concentrations were higher in Line LW than Line HW, but there was no difference in T4 concentrations. Peak plasma T3 and T4 occurred in the TS stage for embryos of both lines. This experiment used lines of chickens known to differ quantitatively and temporally in the traits measured but not previously investigated for possible differences between the sexes in these traits. The study shows that there were no consistent differences between the sexes within these lines for time to hatch, body weight at hatch, or amounts of plasma T3 and T4 at various stages of hatching.