Rao S, Notter D R
Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061, USA.
J Anim Sci. 2000 Aug;78(8):2113-20. doi: 10.2527/2000.7882113x.
Data on litter size, weaning weights at 60, 90, and 120 d, postweaning gains from weaning to 120 or 365 d of age, fleece weight, and fiber diameter from Targhee, Suffolk, and Polypay flocks participating in the U.S. National Sheep Improvement Program were used to estimate genetic parameters for litter size and genetic relationships between early-life traits and future litter size. Records on 7,591 lambings by 3,131 Targhee ewes, 10,295 lambings by 5,038 Suffolk ewes, and 6,061 lambings by 2,709 Polypay ewes were used. Heritability estimates for litter size ranged from .09 to .11 across breeds; repeatability ranged from .09 to .13. Additive genetic effects on litter size were generally positively, and occasionally significantly, correlated with animal additive genetic effects on weaning weights and postweaning gains. Genetic correlations (r(a)) ranged from .08 to .48 in Targhee and from .17 to .43 in Suffolk but were close to 0 in Polypay (-.14 to .09). Additive maternal effects on weaning weight were positively associated with litter size in Suffolk and Polypay; this correlation was negative (-.23 to -.35), but not significant, in Targhee. Fleece weight was not strongly associated with litter size; (r(a) = -.09 to .21). However, fiber diameter had a significant undesirable correlation with litter size (.30) in Targhee. Estimates of phenotypic correlations of litter size with early-life traits were uniformly small (-.02 to .08). Thus, although occasional genetic antagonisms between litter size and early-life traits were observed in these data, none appeared large enough to prevent simultaneous genetic improvement in both traits.
参与美国国家绵羊改良计划的塔吉羊、萨福克羊和波吕佩羊群体的产仔数、60日龄、90日龄和120日龄的断奶体重、断奶至120日龄或365日龄的断奶后增重、羊毛重量和纤维直径数据，用于估计产仔数的遗传参数以及早期生活性状与未来产仔数之间的遗传关系。使用了3131只塔吉母羊的7591次产羔记录、5038只萨福克母羊的10295次产羔记录以及2709只波吕佩母羊的6061次产羔记录。不同品种产仔数的遗传力估计值在0.09至0.11之间；重复性在0.09至0.13之间。产仔数的加性遗传效应通常与动物断奶体重和断奶后增重的加性遗传效应呈正相关，偶尔也呈显著正相关。塔吉羊的遗传相关性（r(a)）在0.08至0.48之间，萨福克羊在0.17至0.43之间，但波吕佩羊接近0（-0.14至0.09）。萨福克羊和波吕佩羊断奶体重的加性母体效应与产仔数呈正相关；在塔吉羊中，这种相关性为负（-0.23至-0.35），但不显著。羊毛重量与产仔数的关联不强；（r(a)=-0.09至0.21）。然而，在塔吉羊中，纤维直径与产仔数存在显著的不良相关性（0.30）。产仔数与早期生活性状的表型相关性估计值均较小（-0.02至0.08）。因此，尽管在这些数据中观察到产仔数与早期生活性状之间偶尔存在遗传拮抗作用，但似乎没有一个大到足以阻止两个性状同时进行遗传改良。
