Department of Animal and Veterinary Sciences, Scotland's Rural College (SRUC), Easter Bush, Midlothian, Scotland EH25 9RG, UK.
Department of Animal and Biosciences, Teagasc, Animal & Grassland Research and Innovation Centre, Moorepark, Fermoy, P61 P203 Co. Cork, Ireland.
Animal. 2020 May;14(5):899-909. doi: 10.1017/S1751731119002908. Epub 2020 Jan 7.
Lamb live weight is one of the key drivers of profitability on sheep farms. Previous studies in Ireland have estimated genetic parameters for live weight and carcass composition traits using a multi-breed population rather than on an individual breed basis. The objective of the present study was to undertake genetic analyses of three lamb live weight and two carcass composition traits pertaining to purebred Texel, Suffolk and Charollais lambs born in the Republic of Ireland between 2010 and 2017, inclusive. Traits (with lamb age range in parenthesis) considered in the analyses were: pre-weaning weight (20 to 65 days), weaning weight (66 to 120 days), post-weaning weight (121 to 180 days), muscle depth (121 to 180 days) and fat depth (121 to 180 days). After data edits, 137 402 records from 50 372 lambs across 416 flocks were analysed. Variance components were derived using animal linear mixed models separately for each breed. Fixed effects included for all traits were contemporary group, age at first lambing of the dam, parity of the dam, a gender by age of the lamb interaction and a birth type by rearing type of the lamb interaction. Random effects investigated in the pre-weaning and weaning weight analyses included animal direct additive genetic, dam maternal genetic, litter common environment, dam permanent environment and residual variances. The model of analysis for post-weaning, muscle and fat depth included an animal direct additive genetic and litter common environment effect only. Significant direct additive genetic variation existed in all cases. Direct heritability for pre-weaning weight ranged from 0.14 to 0.30 across the three breeds. Weaning weight had a direct heritability ranging from 0.17 to 0.27 and post-weaning weight had a direct heritability ranging from 0.15 to 0.27. Muscle and fat depth heritability estimates ranged from 0.21 to 0.31 and 0.15 to 0.20, respectively. Positive direct correlations were evident for all traits. Results revealed ample genetic variation among animals for the studied traits and significant differences between breeds to suggest that genetic evaluations could be conducted on a per-breed basis.
羔羊活重是绵羊养殖场盈利能力的关键驱动因素之一。爱尔兰之前的研究使用多品种群体而非单一品种基础来估计活重和胴体组成性状的遗传参数。本研究的目的是对 2010 年至 2017 年间在爱尔兰共和国出生的纯种泰泽尔、萨福克和夏洛莱羔羊的三个羔羊活重和两个胴体组成性状进行遗传分析。分析中考虑的性状（括号内为羔羊年龄范围）为：断奶前体重（20 至 65 天）、断奶体重（66 至 120 天）、断奶后体重（121 至 180 天）、肌肉深度（121 至 180 天）和脂肪深度（121 至 180 天）。经过数据编辑，对来自 416 个羊群的 50372 只羔羊的 137402 条记录进行了分析。分别为每个品种使用动物线性混合模型得出方差分量。所有性状的固定效应包括当代组、母羊首次产羔年龄、母羊胎次、羔羊性别与年龄的互作以及羔羊出生类型与饲养类型的互作。在断奶前和断奶体重分析中，随机效应包括动物直接加性遗传、母羊母体遗传、胎内共同环境、母羊永久环境和残差方差。在断奶后、肌肉和脂肪深度的分析模型中仅包括动物直接加性遗传和胎内共同环境效应。在所有情况下都存在显著的直接加性遗传变异。三个品种的断奶前体重直接遗传力在 0.14 至 0.30 之间。断奶体重的直接遗传力在 0.17 至 0.27 之间，断奶后体重的直接遗传力在 0.15 至 0.27 之间。肌肉和脂肪深度的遗传力估计值分别在 0.21 至 0.31 和 0.15 至 0.20 之间。所有性状之间均存在正的直接相关性。研究结果表明，研究性状在动物之间存在丰富的遗传变异，品种之间存在显著差异，这表明可以按品种进行遗传评估。
