Kühn E R, Darras V M, Gysemans C, Decuypere E, Berghman L R, Buyse J
Leuven Poultry Research Group, University of Leuven, Heverlee, Belgium.
Poult Sci. 1996 May;75(5):595-600. doi: 10.3382/ps.0750595.
Male and female broiler chicks were raised separately in nearly continuous lighting [23 h light (L):1 h dark (D), CL] and consumed feed ad libitum. At 7 d of age, the intermittent lighting schedule (1L:3D, IL) was imposed on half of the chicks, whereas the other chicks remained under CL. In addition to performance characteristics, several parameters of the somatotrophic and thyrotrophic axes were studied together with plasma concentrations of testosterone. Males had a higher growth rate than females regardless of the imposed lighting schedule and this pronounced growth difference is reflected by higher plasma concentrations of growth hormone (GH), and a better GH receptor occupancy. Differences in growth rate between sexes could not be attributed to differences in circulating 3,3',5-triiodothyronine (T3) levels or to hepatic deiodination activities. However, from 3 wk of age onwards, males had significantly higher plasma testosterone levels than females. Plasma GH and T3 levels decreased whereas plasma insulin-like growth factor-I and thyroxine levels increased with age in all experimental groups. The age-related decline in plasma GH levels were less pronounced for males than for females. No major changes in other hormonal parameters or deiodination activities could be observed as a result of imposing IL, except for the higher plasma GH levels of IL chickens, and for plasma testosterone concentrations in IL males at Day 41, which were twice the levels found in their CL counterparts. These results therefore suggest that the somatotrophic axis as well as circulating testosterone levels mediate the sex-related differences in growth rate and the compensatory growth as present in males.
雄性和雌性肉鸡雏分别在近乎持续光照[23小时光照（L）：1小时黑暗（D），持续光照（CL）]条件下饲养，并自由采食。7日龄时，对一半雏鸡实施间歇光照制度（1L：3D，间歇光照（IL）），而另一半雏鸡仍处于持续光照条件下。除了生产性能特征外，还研究了生长激素轴和促甲状腺轴的几个参数以及血浆睾酮浓度。无论采用何种光照制度，雄性的生长速度都高于雌性，这种明显的生长差异表现为血浆生长激素（GH）浓度较高以及GH受体占有率较高。两性之间的生长速度差异不能归因于循环三碘甲状腺原氨酸（T3）水平的差异或肝脏脱碘活性的差异。然而，从3周龄开始，雄性的血浆睾酮水平显著高于雌性。在所有实验组中，血浆GH和T3水平随年龄下降，而血浆胰岛素样生长因子-I和甲状腺素水平随年龄增加。雄性血浆GH水平随年龄的下降不如雌性明显。实施间歇光照后，未观察到其他激素参数或脱碘活性有重大变化，但间歇光照组鸡的血浆GH水平较高，在第41天时，间歇光照组雄性的血浆睾酮浓度是持续光照组雄性的两倍。因此，这些结果表明，生长激素轴以及循环睾酮水平介导了生长速度方面的性别相关差异以及雄性中存在的代偿性生长。
