Estimation of genetic and phenotypic parameters and environmental trends of pre-weaning growth traits of Japanese Black calves using animal model.

Data were collected on 1739 records of Japanese Black calves during the period 1937-2002 at the Department of Livestock and Grassland Science, National Agricultural Research Centre for Western Region, Oda City, Shimane Prefecture. The objectives were to estimate heritability, maternal effect and genetic and phenotypic correlations between birth weight, weaning weight and average daily gain from birth to weaning; to evaluate calf breeding values and to evaluate the genetic and phenotypic trends for these traits. Heritability estimates of birth weight, weaning weight and average daily gain were 0.39, 0.17 and 0.26, respectively. The corresponding maternal components were 0.10, 0.10 and 0.11, respectively. Genetic correlations between birth weight and weaning, birth weight and average daily gain and weaning weight and average daily gain were 0.30, -0.17 and 0.86, respectively. The corresponding phenotypic correlations were 0.19, -0.33 and 0.90, respectively. Calf breeding values ranged between -17.93 and 2.83, between -4.72 and 18.08 and between -0.070 and 0.182kg for birth weight, weaning weight and average daily gain, respectively. Regression coefficients of breeding values of birth weight, weaning weight and average daily gain on year of calving were not significant and accounted for 0.011±0.012, -0.02±0.02 and -0.0002±0.0002, respectively. The corresponding regression coefficients of the phenotypic values of weaning weight and average daily gain on year of calving were significant and accounted for 2.16±0.31 and 0.013±0.002, respectively. However, that of birth weight was not significant (0.18±0.10). Breeding values fluctuated across years of study with no clearly defined pattern or trend. A similar trend was observed for phenotypic values. It was concluded that the environment rather than genetics, might have had a higher influence on the performance of calves since no selection had been previously applied in this herd