ESTIMATION OF THE GENETIC PARAMETERS FOR CROSSBRED DAIRY COWS

Abstract

The study was conducted to investigate the phenotypic performances and to estimate the genetic parameters of five dairy traits such as age at first calving, post partum heat period, calving interval, lactation length and lactation milk yield for crossbred cows under Chittagong metropolitan area, Chittagong, Bangladesh. A total of 480 different crossbred of Friesian × Local (F × L), Friesian × Shahiwal (F × SL) and Friesian × Shahiwal × Local (F × SL × L) cows data were used. Mean of calving interval was 442.59±7.78, 449.86±8.64 and 457.88±8.20 days in F × L, F × SL and F × SL × L crossbreds, respectively. The study reveals that the mean AFC and PPHP were lowest for F × L cross. The average lactation milk yield was 1506.75±71.37, 1351.00±79.25 and 929.10±75.23 liters for F × L, F × SL and F × SL × L crossbreds, respectively. Lactation length was longer for F × L than the F × SL and F × SL × L crossbreds. Breed groups had significant (P<0.05) effects on most of the traits except PPHP and LL. All traits differed due to differences in farm, season, year of birth and number of lactation. The overall heritability estimates in crossbreds were 0.10, 0.07, 0.05, 0.27, and 0.30 for the AFC, PPHP, CI, LL and LMY, respectively. Higher heritability for LL and LMY in different crossbreds was attributed due to additive gene action. F × L crossbred exhibited higher h2 estimates for most of the traits. Genetic and phenotypic correlation coefficients between traits were low to medium. Considering all the phenotypic parameters studied F × L showed better performance than other crossbreds. Therefore, the chosen cows of this crossbred would be more beneficial for future selection programme. Low heritabilities for AFC, PPHP and CI in this study indicated that improvement programmes for these traits should focus on management rather breed groups. This study will assist the animal breeders and farmers for future selection decision and crossbred cattle rearing under existing farming conditions.