Liu G, Dunnington E A, Siegel P B
Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061-0306, USA.
Poult Sci. 1995 Aug;74(8):1259-68. doi: 10.3382/ps.0741259.
Thirty-six generations of divergent selection for BW at 8 wk of age (BW8) resulted in approximately an eightfold difference between the high (HWS) and low (LWS) lines for this trait. Correlated traits included BW at 4, 24, and 38 wk of age (BW4, BW24, BW38, respectively), age at first egg (AFE), and percentage hen-day egg production (HDP). Responses of BW4 followed the same pattern as that for the selected trait, with the response about five times greater during the first 18 than the last 18 generations of selection in Line HWS and less than two times greater in Line LWS. For BW24 and BW38, correlated responses were greater for LWS than for HWS females without feed restriction, suggesting changes in growth curves after selection age. Although AFE was delayed in both lines, the delay was greater in Line LWS (some individuals of which were anorexic) than in Line HWS and greater in the second half than the first half of the experiment. For pullets that commenced lay, HDP declined slightly in both lines. Correlations between BW at 4, 8, 24, and 38 wk of age were moderate to high and positive in both lines. When feed intake was restricted in Line HWS, however, there were no correlations of BW4 or BW8 with BW24 or BW38. Correlations between AFE and BW at all ages were negative in Line LWS. In Line HWS there were negative correlations of AFE with BW24 and with BW38. Relaxed lines, established periodically during the experiment, were satisfactory monitors of environmental influences for primary and correlated traits.
对8周龄体重（BW8）进行了36代的 divergent 选择，该性状的高选系（HWS）和低选系（LWS）之间产生了约8倍的差异。相关性状包括4、24和38周龄时的体重（分别为BW4、BW24、BW38）、开产日龄（AFE）和母鸡日产蛋率（HDP）。BW4的反应与所选性状的模式相同，在HWS系中，前18代的反应比最后18代大约大5倍，而在LWS系中则不到2倍。对于BW24和BW38，在无饲料限制的情况下，LWS雌性的相关反应比HWS更大，这表明选择年龄后生长曲线发生了变化。尽管两个系的AFE都延迟了，但LWS系（其中一些个体厌食）的延迟比HWS系更大，且在实验的后半段比前半段更大。对于开始产蛋的小母鸡，两个系的HDP均略有下降。两个系中4、8、24和38周龄时体重之间的相关性为中度至高且呈正相关。然而，当HWS系限制采食量时，BW4或BW8与BW24或BW38之间没有相关性。在LWS系中，所有年龄的AFE与体重之间的相关性均为负。在HWS系中，AFE与BW24和BW38之间存在负相关。在实验期间定期建立的放松系，是对主要性状和相关性状环境影响的良好监测指标。
