Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061, USA.
J Anim Sci. 2009 Nov;87(11):3515-24. doi: 10.2527/jas.2008-1623. Epub 2009 Jul 31.
Records from 2,525 adult Targhee ewes and 10,099 lambs were used to estimate genetic parameters in an animal model for ewe stayability (STAY), productive life (PL), adult BW (AW) and BCS, fleece characteristics, and number of lambs born (NLB) and for lamb BW at birth and approximately 45 d, 120 d (120W; weaning), 12 mo, and 18 mo of age. Stayabilities were analyzed as overall stayability (STAYn|2), which indicated presence or absence of a ewe at n yr of age, given that she was present at 2 yr of age, or marginal stayability (STAYn|n-1) recording the presence of a ewe at n yr of age, given that she was present in the previous year. Productive life was measured as the age of ewe in years at her last lambing. Lamb BW were corrected for age at weighing; BW taken at or before weaning were adjusted for effects of type of birth and rearing, age of dam, and sex using National Sheep Improvement Program methods. The NLB was likewise adjusted for effects of ewe age before analysis. Birth year was included as a fixed effect for all traits. Year of record and, for AW and CS, the number of lambs born or born and reared were also included in models for adult traits. Models for all traits included random additive genetic and residual effects. Random maternal genetic and dam permanent environmental effects were also included in the model for lamb (pre)weaning BW, and random permanent environmental effects of the ewe were included in models for adult traits. The heritability estimate for PL was 0.05 (P < 0.10). Additive variance in STAY was only present after 5 yr of age (P < 0.05), with estimated heritabilities ranging from 0.04 to 0.10. Phenotypic correlations between STAY and other traits were near zero, ranging from -0.07 to 0.14. Estimates of genetic correlations of STAY5|4 and STAY6|2 with maternal genetic effects on 120W were positive (both 0.46; P < 0.05), suggesting that STAY and maternal effects on 120W both reflect genetic variation in ewe fitness characteristics. Genetic correlations between STAY5|4 and 120W, AW, and NLB were not different from zero (0.06, 0.13, and -0.06, respectively; P > 0.10). However, genetic correlations between STAY6|2 and 120W, AW, and NLB were all negative, with values of -0.17, -0.32 (P < 0.05), and -0.03, respectively, indicating a possible small antagonism between STAY and genetic effects on body size.
从 2525 只成年塔尔羊母羊和 10099 只羔羊的记录中，使用动物模型估计了母羊可留用性（STAY）、生产寿命（PL）、成年体重（AW）和体况评分（BCS）、羊毛特征以及出生羔羊数（NLB）和羔羊出生时和大约 45、120（断奶）、12 个月和 18 个月时的 BW 的遗传参数。可留用性分析为总体可留用性（STAYn|2），表示给定母羊在 2 岁时存在，n 岁时是否存在母羊，或边际可留用性（STAYn|n-1）记录给定母羊在前一年存在，n 岁时是否存在母羊。生产寿命被测量为母羊最后一次产羔时的年龄。羔羊 BW 经过年龄校正；断奶前 BW 采用国家绵羊改良计划方法校正初生类型和饲养方式、母羊年龄和性别的影响。NLB 也在分析前调整了母羊年龄的影响。出生年份被作为所有性状的固定效应。年份记录以及 AW 和 CS 的产羔数或产羔和育肥数也包含在成年性状模型中。所有性状模型均包含随机加性遗传和残差效应。羔羊（预）断奶 BW 模型中还包含随机母系遗传和母羊永久环境效应，成年性状模型中包含母羊的随机永久环境效应。PL 的遗传力估计值为 0.05（P < 0.10）。STAY 的加性方差仅在 5 岁后存在（P < 0.05），估计的遗传力范围为 0.04 至 0.10。STAY 与其他性状之间的表型相关接近零，范围为 -0.07 至 0.14。STAY5|4 和 STAY6|2 与 120W 母系遗传效应的遗传相关性为正（均为 0.46；P < 0.05），表明 STAY 和 120W 的母系效应均反映了母羊健康特征的遗传变异。STAY5|4 和 120W、AW 和 NLB 之间的遗传相关性均不显著（0.06、0.13 和 -0.06，分别；P > 0.10）。然而，STAY6|2 与 120W、AW 和 NLB 之间的遗传相关性均为负，值分别为 -0.17、-0.32（P < 0.05）和 -0.03，表明 STAY 和遗传对体型的影响之间可能存在较小的拮抗作用。
