Eitan Y, Soller M, Rozenboim I
Department of Genetics, The Silberman Life Sciences Institute, The Hebrew University of Jerusalem, Israel.
Poult Sci. 1998 Nov;77(11):1593-600. doi: 10.1093/ps/77.11.1593.
The time course of comb development and estrogen levels were compared in broiler (BX) and layer (LX) females that consumed feed ad libitum (A) or were subjected to quantitative feed restriction (R). The chicks were reared under short photoperiod [(6 h light (L):18 h dark (D)] until 22 wk of age. At this time, photoperiod was increased in one step to 8L:16 D, and then gradually increased until 14L:10D at 34 wk. There was a significant interaction between genetic type and feeding treatment, such that entry into lay of the LX-R and BX-R females was delayed by 1 and 4 wk, respectively, relative to the LX-A and BX-A birds. Mean comb size of LX-A birds began to increase while still under 6L:18D photoperiod; that of the other treatment groups did not begin to increase until photoperiod was shifted to 8L:16D. Comb size of individual LX-A, LX-R, and BX-A birds began to increase about 8 wk prior to individual onset of lay; that of BX-R birds about 11 wk prior to onset of lay. In all groups, estrogen levels remained low until 3 to 4 wk prior to onset of lay, when they showed a sharp increase. Following onset of lay, estrogen levels of all groups remained high. Critical day length of LX-A birds appears to be lower than that of BX-A birds. In addition, feed restriction per se appears to decrease photoperiod responsiveness of BX birds.
对自由采食（A）或定量限饲（R）的雌性肉鸡（BX）和蛋鸡（LX）的鸡冠发育时间进程和雌激素水平进行了比较。雏鸡在短光照周期[6小时光照（L）：18小时黑暗（D）]下饲养至22周龄。此时，光照周期一次性增加到8L：16D，然后逐渐增加，直到34周时达到14L：10D。遗传类型和饲养处理之间存在显著交互作用，因此，相对于LX-A和BX-A组的母鸡，LX-R和BX-R组的母鸡分别延迟1周和4周进入产蛋期。LX-A组母鸡的平均鸡冠大小在仍处于6L：18D光照周期时就开始增加；其他处理组的母鸡直到光照周期转变为8L：16D时才开始增加。LX-A、LX-R和BX-A组个体母鸡的鸡冠大小在个体开始产蛋前约8周开始增加；BX-R组母鸡在开始产蛋前约11周开始增加。在所有组中，雌激素水平在开始产蛋前3至4周一直保持较低水平，之后急剧上升。产蛋开始后，所有组的雌激素水平都保持在较高水平。LX-A组母鸡的临界日长似乎低于BX-A组母鸡。此外，限饲本身似乎会降低BX鸡对光照周期的反应性。
