Estimation of genetic, phenotypic and environmental trends for birth weight and weaning weight in Najdi calves

In this research, in order to predict genetic parameters and genetic and environmental trends of birth weight and weaning weight of Najdi calves, 1249 records collected during the period of 1989 - 2004 in Najdi cattle Research Station of Khuzestan were used. Variance components, genetic parameters and predicted breeding values were estimated for traits, using animal model with direct and maternal additive genetic effects as the best model and restricted maximum likelihood method based on a derivative-free algorithm. Phenotypic, genetic and environmental trends were calculated as the regression of average phenotypic values, predicted breeding values and environmental values on year of calf birth, respectively. Direct and maternal heritability for birth weight and weaning weight were estimated 0.37±0.11, 0.08±0.04, 0.13±0.06 and 0.1±0.06, respectively. Phenotypic trends of traits were 0.07±0.05 kg/year and 0.21±0.3 kg/year for birth weight and weaning weight, direct additive genetic trends for these traits were 0.06±0.01 kg/year and 0.13±0.04 kg/year, and maternal additive genetic trends for these traits were 0.03±0.005 kg/year and 0.13±0.01 kg/year, respectively. Environmental trends were estimated as 0.02±0.06 kg/ year and 0.04±0.3 kg/year, respectively.