【摘要】 本文应用通用选择指数原理探讨了有关种公羊选种决策的几个问题。以提高净毛量、产羔数和体重为选育目标,毛长为选种辅助性状,利用种公羊,及其半同胞姐妹和半同胞女儿的资料,分别制定了综合选择指数、保持体重不变的约束指数以及净毛量每代改进量0.4kg(留种率20％)的最宜指数,并比较了这三个指数的预期选择效果。此外,还进一步讨论了:(1)短期内集中力量提高净毛量、产羔数或体重所能获得的改进量及总的选择效果,结论是尽力提高净毛量的效果最佳;(2)增加种公羊亲属数对提高选择效果的影响,结论是在已有一定亲属数的基础上再进一步增加,对选择效果的提高很有限,增加种公羊半同胞子女数比增加半同胞姐妹数更为有利。更多还原

【Abstract】 Several problems associated with selection strategies of breeder rams are discussed using the general selection index.Selection objective is to improve the aggregate breeding value of clean-fleece weight,number of lambs and body weight.Staple length is the assistant trait of selection.Aggregate,restrictive and optimal selection indices are constructed with the information of ram individual and the ram’s half-sib sisters and half-sib daughters.The restrictive selection maintains the genetic gain of body weight unchanged.The optimal selection keeps the genetic gain of the clean-fleece weight at 0.4kg in one generation(20% retention).The selection effects of the three indices are compared.Furthermore,two related-problems are discussed.First,if each single trait of the three objective trats is selected to permit the genetic gain of the trait to be as large as possible in a short time,the largest gain of the aggregate breeding value is obtained when the trait is clean-fleece weight.Secondly,when the number of ram’s relatives is more than enough,the selection effect of increasing the number is very limited However,increasing the ram’s half-sib daughters is more favorable than incresing the ram’s half-sib sisters.更多还原