Genetic analysis of average daily gain in Baluchi sheep

Abstract

The objective of the present study was to estimate genetic parameters and genetic trends for average daily gain (growth rate) and to investigate the genetic effect of body weight at different ages (birth (BW), weaning (WW), 6months (W6) and 9months (W9)) on growth rate of Baluchi sheep. Data were collected at the Abbasabad Baluchi Sheep Breeding Station (flock 2) from 1983 to 2009. Traits were average daily gain from birth to weaning (ADGa), from weaning to 6months of age (ADGb) and from weaning to 9months of age (ADGc). (Co) variance components and genetic parameters were estimated by univariate and multivariate animal models using Restricted Maximum Likelihood (REML) procedure. Genetic improvements over analyze were calculated as the differences between the means of estimated breeding values at the beginning and at the end of analyze. Genetic trends were obtained by regressing the means of predicted breeding values on year of birth for each trait. Direct heritability estimates were, correspondingly, 0.03, 0.11 and 0.05 for ADGa, ADGb and ADGc. Estimate of maternal heritability (m2) for ADGc was 0.11. Estimated value of maternal permanent environment variance as a proportion of phenotypic variance (c2) was 0.14 for ADGa. Negative genetic correlations were observed for BW-ADGb and BW-ADGc. Direct additive genetic correlations between traits ranged from −0.63 (BW-ADGc) to 0.91 (W9-ADGc). Phenotypic correlations ranged from −0.49 (BW-ADGb) to 0.88 (WW-ADGa). Maternal permanent environmental correlations ranged between 0.13 (W9-ADGa) to 0.99 (WW-ADGa). Genetic improvements were 0.033g, 0.36g and 0.31g for ADGa, ADGb and ADGc, respectively. Annual genetic gains (g/year) for ADGa, ADGb and ADGc, were 0.02, 0.03 and 0.04, respectively.