Bohren B B, Rogler J C, Carson J R
Poult Sci. 1982 Sep;61(9):1804-8. doi: 10.3382/ps.0611804.
Two replicates of four lines of White Leghorn chickens previously selected for fast and slow gain from 5 to 9 weeks of age in a hot (32.2 C) and cold (21.1 C) selection environment were grown from 5 to 9 weeks in the hot and cold temperature environments and then subjected to high temperature stress at 40.6 C. Four different experiments were run. The percent mortality was analyzed when approximately 50% of the birds had died. Birds reared in the cold environment were heavier and consistently had higher mortality than those reared in the hot environment when both were subjected to acute heat stress (40.6 C). The importance of acclimation to mild heat stress on response to acute heat stress was demonstrated by the mortality difference. No significant differences in survival under heat stress were found between lines selected in the hot and the cold selection environments. Lines selected for fast growth had significantly higher mortality rates under high temperature stress than lines selected for slow growth in replicate 1 but not in replicate 2. Estimates of the genetic correlation between weight gain from 5 to 9 weeks of age and percent mortality under heat stress after two generations of selection in replicate 2 was -.004, and after three generations of selection in replicate 1 was +.076.
选取了四系白来航鸡，在热（32.2摄氏度）冷（21.1摄氏度）两种选择环境下，从5周龄到9周龄分别针对快速增重和缓慢增重进行选育，每种选育环境下的四系鸡各有两个重复组。这些鸡在热、冷两种温度环境下从5周龄饲养至9周龄，然后在40.6摄氏度下经受高温应激处理。共进行了四项不同的实验。当约50%的鸡死亡时，分析死亡率。在急性热应激（40.6摄氏度）下，饲养在寒冷环境中的鸡体重更重，且死亡率始终高于饲养在炎热环境中的鸡。死亡率差异证明了适应轻度热应激对急性热应激反应的重要性。在热选择环境和冷选择环境中选育的品系，在热应激下的存活率没有显著差异。在重复组1中，高温应激下快速生长选育品系的死亡率显著高于缓慢生长选育品系，但在重复组2中并非如此。在重复组2中经过两代选择后，5至9周龄体重增加与热应激下死亡率百分比之间的遗传相关估计值为-.004，在重复组1中经过三代选择后为+.076。
