Estimates of genetic and phenotypic parameters for dairy traits in Friesian-Bunaji crossbreds

Genetic and phenotypic parameters for dairy traits were computed using data on Friesian-Bunaji crossbred cows collected over a twenty-three year period (1967-1989) from the dairy herd of the National Animal Production Research Institute Shika, Zaria, Nigeria. Estimated repeatabilities computed from variance components were 0.72 ± 0.06,0.60 ± 0.10,0.73 ± 0.02,0.53 ± 0.24 and 0.56 ± 0.18 for total lactation yield, lactation length, 305-day yield, calving interval and dry period, respectively. Heritability estimates were 0.44 ± 0.07,0.52 ± 0.12,0.30 ± 0.13,0.18 ± 0.02,0.26 ± 0.08 and 0.27 ± 0.10 for total lactation yield, lactation length, 305-day yield, calving interval, dry period and age at first calving,respectively. Genetic and phenotypic correlation coefficients between traits were medium to high, ranging from 0.30 to 0.95. The results of this study showed that the genetic response to selection in Friesian-Bunaji crosses for total lactation yield, 305-day yield and lactation length could be moderately high since the proportion of additive genetic variance was fairly high. Improvement programmes for age at first calving, calving interval and dry period should focus mostly on management, given their low heritability estimates.