Siopes T D
Department of Poultry Science, North Carolina State University, Raleigh 27695-7608.
Poult Sci. 1994 Dec;73(12):1906-13. doi: 10.3382/ps.0731906.
Critical day lengths (CDL) for ovarian growth, egg production, and photorefractoriness were estimated in turkey hens during winter and summer seasons. In two experiments, one in each season, fixed day length treatments ranging from 10.5 to 16 h/d were applied to photosensitive hens at 30 wk of age. Daily egg production was used to estimate CDL for the induction of egg production as well as optimal egg production. After 24 wk on light treatments, hens used during the winter season were exposed to 20 h light: 4 h dark and subsequent changes in egg production were used to evaluate photorefractoriness. In two additional experiments, a night-interruption design was used to evaluate CDL and ovarian photoresponsiveness during winter and summer. The CDL for inducing egg production varied by season and was estimated to be 10.5 h or less during winter and about 11 h during summer. Likewise, the CDL for optimal egg production varied by season, being 11 to 11.5 h during winter and > 14 h during summer. The CDL for photorefractoriness in winter photostimulated hens was between 12 and 12.5 h. It was concluded that CDL vary by season and are not fixed, but are dynamic characteristics of photoperiodic processes. Thus, photoresponsiveness of turkey hens changes by season. In addition, CDL for initiating egg production, stimulating egg production, and inducing photorefractoriness are all different, with the CDL for photorefractoriness being longest.
在冬季和夏季对火鸡母鸡的卵巢生长、产蛋量和光不应性的临界日长（CDL）进行了估计。在两个实验中，每个季节各一个，对30周龄的光敏母鸡施加10.5至16小时/天的固定日长处理。每日产蛋量用于估计诱导产蛋以及最佳产蛋量的CDL。经过24周的光照处理后，冬季实验中使用的母鸡暴露于20小时光照：4小时黑暗条件下，并利用随后产蛋量的变化来评估光不应性。在另外两个实验中，采用夜间中断设计来评估冬季和夏季的CDL以及卵巢的光反应性。诱导产蛋的CDL因季节而异，估计冬季为10.5小时或更短，夏季约为11小时。同样，最佳产蛋量的CDL也因季节而异，冬季为11至11.5小时，夏季大于14小时。冬季光刺激母鸡的光不应性CDL在12至12.5小时之间。得出的结论是，CDL因季节而异，不是固定不变的，而是光周期过程的动态特征。因此，火鸡母鸡的光反应性随季节变化。此外，启动产蛋、刺激产蛋和诱导光不应性的CDL均不同，其中光不应性的CDL最长。
