Comparison of different models for the estimation of genetic parameters of wool traits in intercross sheep

Abstract

The quality and yield of wool determine the economic value of the fine-wool sheep, therefore this study aimed to estimate the (co)variance components and genetic parameters for direct and maternal influences on greasy fleece yield (GFY), staple length (SL) and fibre diameter (FD) of Inter-cross sheep maintained at North Temperate Regional Station, Garsa, Kullu (Himachal Pradesh), India. Data file consisted of first six monthly shearing records of 1084 hoggets descended from 513 ewes and 153 rams over a period of 11 years (2012–2022). Univariate analysis was carried out by average information restricted maximum likelihood (AI-REML) procedure fitting six different animal models with various combinations of direct and maternal effects. Improvement of log-likelihood values were used to evaluate the best fit models for fibre traits. Analysis revealed that year of birth was significant (P < 0.05) on all traits, while sex and types of birth on GFY and SL only. It indicates specialized care and management of lambs across significant effects to avoid production losses. Model 3, incorporating direct additive genetic, maternal additive genetic and their covariance showed the maximum Log-Likelihood estimate for all traits. The direct heritability for GFY, SL and FD were 0.11 ± 0.06, 0.10 ± 0.06 and 0.06 ± 0.05 and corresponding maternal heritability for respective traits were 0.06, 0.03, and 0.08, respectively. The correlations between direct and maternal effects ranged from −0.47 ± 0.07 (GFY) to −0.89 ± 0.31 (FD) for wool traits, which have inflated the heritability estimate. The total heritability estimates were very low indicating very low additive genetic variance for these traits. Genetic correlations among various wool traits were low and positive. These results suggest little scope of direct selection for these traits, however care and management of lambs during critical phase of growth, that affects the wool production and quality may help in reducing wool production losses.