Abstract The main aim of this study is to estimate genetic parameters and (co) variance components for body weights at various ages in Nellore sheep born during the period from 1993 to 2016 (23 years). A total of 4822 lambs with pedigree descended from 144 sires and 1299 dams were included in this study. Bayesian analysis using Gibbs sampler multi trait animal model with and without maternal effects was studied. Traits included in this study were birth weight (BW), weaning weight (WW), six months body weight (6MW), nine months body weight (9 MW), Yearling weight (YW). Year-season of birth and sex of lamb (contemporary groups) were considered as fixed effects with ewe weight at lambing as a covariate. Estimates of direct heritability estimates for birth weight, WW, 6MW, 9MW and YW based on best model were 0.17, 0.28, 0.27, 26 and 0.23, respectively and the corresponding maternal heritability estimates were 0.12, 0.14, 0.14, 0.12 and 0.13, respectively. The direct-maternal genetic covariance was negative for all the studied traits. Strong and positive estimates of direct additive genetic correlations were observed in growth traits and they ranged from 0.16 to 0.83, whereas the direct-maternal genetic correlations were negative for all the traits and these estimates ranged from ˗0.89 to ˗0.08. Moderate estimates of heritability for the growth traits obtained in this study suggested the presence of better genetic variability and the possibility for genetic improvement of Nellore sheep through selection. Maternal genetic effects were significant in all the traits. Hence, it is recommended to incorporate these effects in the genetic analysis by including it as a genetic or environmental effect or both. The environmental variance obtained in the study suggested that the growth performance of Nellore sheep may be enhanced by improving the feeding and management aspects. Correlations among traits and effects should be considered while implementing breed improvement program.

中文翻译：

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使用贝叶斯方法对印度半干旱地区牧场饲养的 Nellore 绵羊生长性状进行多性状遗传评估

摘要 本研究的主要目的是估计 1993 年至 2016 年（23 岁）期间出生的 Nellore 绵羊不同年龄体重的遗传参数和（co）方差分量。共有 4822 只具有谱系的羔羊来自 144 个公牛和 1299 只水母被纳入本研究。研究了使用吉布斯采样器多性状动物模型进行的贝叶斯分析，有和没有母体效应。本研究中包括的性状是出生体重 (BW)、断奶体重 (WW)、六个月体重 (6MW)、九个月体重 (9 MW)、一岁体重 (YW)。出生年份和羔羊性别（当代组）被认为是固定效应，母羊产羔体重作为协变量。基于最佳模型的出生体重、WW、6MW、9MW 和 YW 的直接遗传力估计值为 0.17、0.28、0.27、26 和 0.23，分别为 0.12、0.14、0.14、0.12 和 0.13。所有研究性状的直接母系遗传协方差均为负。在生长性状中观察到直接加性遗传相关性的强和正估计，其范围为 0.16 至 0.83，而所有性状的直接母本遗传相关性均为负，这些估计值范围为˗0.89 至 ˗0.08。本研究中获得的生长性状的遗传力的中等估计表明存在更好的遗传变异性和通过选择对 Nellore 绵羊进行遗传改良的可能性。母系遗传效应在所有性状中均显着。因此，建议将这些影响纳入遗传分析，将其作为遗传或环境影响或两者兼而有之。研究中获得的环境差异表明，Nellore 绵羊的生长性能可以通过改善饲养和管理方面来提高。在实施品种改良计划时，应考虑性状和效果之间的相关性。