Estimation of genetic parameters for growth and feed utilization traits in Japanese Black cattle.

摘要

Performance test results of 3250 sire candidates were used to estimate the genetic parameters of growth and feed utilization traits in Japanese Black cattle. Growth traits analysed were six body measurements at the end of the performance test and daily gain (DG) during the test. Feed utilization traits were intakes and conversions of concentrate, roughage, digestible crude protein and total digestible nutrient (TDN). Genetic (co)variance components were estimated by the restricted maximum likelihood procedure using an expectation maximization algorithm under the two-trait animal model. Heritabilities for growth traits ranged from 0.40 to 0.70 and for feed utilization traits from 0.21 to 0.74. Genetic correlations of DG were positive with feed intake (0.15-0.77) and negative with feed conversions (-0.63 to -0.30). These relationships indicate that the selection based on DG improves feed efficiency but it simultaneously increases feed intake. Feed conversions showed genetic correlations ranging from -0.09 to 0.03 with total available energy consumption, TDN intake. Thus the results suggested that feed conversions were not efficient selection criteria to decrease TDN intake and to improve comprehensive feed utilization ability.