蛋鸡主要生产性状的表型分布特点及其对选择的影响

本文对1058只京白Ⅷ东选育群蛋鸡9个性状的表型分布特点进行了研究,并通过偏态对遗传参数估计和选择强度的影响,探讨偏态对选择的作用。结果表明,所有性状的表型频率分布均为单峰曲线,峭度都为极显著的正值,产蛋数和选择指数表现为极显著的负偏斜,体重和开产日龄的分布则显著的正偏斜,蛋重的偏斜度基本不显著。这些结果意味着群体内存在着过多不符合要求的个体。剔除极端记录可以有效地降低偏态的程度,而对多数性状的遗传参数估计值影响不大。当留种率低于70％时,表型分布偏态使实现选择强度低于理论选择强度,这是造成选择反应效率低的一个重要原因。剔除极端记录使指数值分布趋于正态,同时可使实际选择强度基本等于理论选择强度。

Normality of Some Productive Traits and Their Effects on Selection in Layers

The distributions of 9 productive traits in Line Ⅷ of the Beijing white Leghorn were examined, and the effects of non-normality on selection were studied. For all traits studied, frequency distributions with single peak and positive kurtosis were observed. Egg production and selection index showed negative skewness whereas positive skewness were found for body weight and age at first egg. The degree of non-normality could be effectively reduced by truncating extreme records. However, the genetic parameter estimates of most traits were not affected significantly. When the proportion of selected hens was below 70%, the realized selection intensity was smaller than the theoretical one due to non-normality, and this was concluded as an important cause which makes selection response inefficient. After truncating extreme records, the distribution of selection index tended to be normal with the realized selection intensity almost iden-ticl to the theoretical one.