title: [Study on application of the general selection index].
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 0.4 kg 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 traits 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 increasing the ram's half-sib sisters.
authors.forename: Y S
authors.initials: YS
authors.lastname: Chen
authors.forename: Z L
authors.initials: ZL
authors.lastname: Sheng
mesh_terms: D000818:Animals; D001947:Breeding / Q000379:methods; D005260:Female; D008297:Male; D008432:Mathematical Computing; D012641:Selection, Genetic; D012756:Sheep / Q000235:genetics*