Balasundaram Balakrishnan, Thiruvenkadan Aranganoor Kannan, Murali Nagarajan, Muralidharan Jaganadhan, Cauveri Doraiswamy, Peters Sunday Olusola
Department of Animal Genetics and Breeding, Veterinary College and Research Institute, Tamil Nadu Veterinary and Animal Sciences University, Orathanadu 614 625, India.
Department of Animal Genetics and Breeding, Veterinary College and Research Institute, Tamil Nadu Veterinary and Animal Sciences University, Salem 636 112, India.
Animals (Basel). 2023 Jan 28;13(3):454. doi: 10.3390/ani13030454.
Determining the genetic and non-genetic sources of variation in a breed is vital for the formulation of strategies for its conservation and improvement. The present study was aimed at estimating the (co)variance components and genetic parameters of Mecheri sheep by fitting six different animal models in the restricted maximum likelihood method, with a preliminary investigation on the performance of animals for non-genetic sources of variation. A total of 2616 lambs were studied, and varying levels of significance were found for the effects of period, season, parity of dam, and birth type on different body-weight traits. Direct heritability estimates derived from the best animal model for body weight at birth, three months, six months, nine months, and twelve months were 0.21, 0.24, 0.10, 0.15, and 0.09, respectively, and the maternal heritability of the corresponding traits was 0.12, 0.05, 0.04, 0.04, and 0.04, respectively. The genetic correlations between the body-weight traits were all positive and moderate-to-strong, except for the correlation between birth weight and the other body-weight traits. The significance of non-genetic factors studied in this work demanded a correction to improve the accuracy of the direct selection of lambs for body-weight traits. The estimated genetic parameters identified the weaning weight as a selection criterion for the improvement in body weight of Mecheri lambs at different ages. Inbred individuals accounted for approximately 13% of the total population in the Mecheri sheep population studied. There were 877 founders in the population, and the actual effective population size was 128.48. The population's mean generation interval was 3.26. The mean inbreeding values ranged from 0.005 to 0.010 across generations. The population's average relatedness ranged from 0.001 to 0.014 across generations. Individual inbreeding was found to be 0.45 per cent for the entire population and 3.4 per cent for the inbred population.
确定一个品种变异的遗传和非遗传来源对于制定其保护和改良策略至关重要。本研究旨在通过在限制最大似然法中拟合六种不同的动物模型，估计梅切里羊的（协）方差成分和遗传参数，并对动物性能的非遗传变异来源进行初步调查。共研究了2616只羔羊，发现时期、季节、母羊胎次和出生类型对不同体重性状的影响具有不同程度的显著性。从出生时、三个月、六个月、九个月和十二个月体重的最佳动物模型得出的直接遗传力估计值分别为0.21、0.24、0.10、0.15和0.09，相应性状的母体遗传力分别为0.12、0.05、0.04、0.04和0.04。除出生体重与其他体重性状之间的相关性外，体重性状之间的遗传相关性均为正且中等至强。本研究中所研究的非遗传因素的显著性要求进行校正，以提高对羔羊体重性状直接选择的准确性。估计的遗传参数确定断奶体重为改善不同年龄梅切里羔羊体重的选择标准。在所研究的梅切里羊群体中，近交个体约占总人口的13%。该群体中有877个奠基者群体，实际有效群体大小为128.48。该群体的平均世代间隔为3.26。各世代的平均近交值范围为0.005至0.010。该群体的平均亲缘关系在各世代中范围为0.001至0.014。发现整个群体的个体近交率为0.45%，近交群体为3.4%。
