Abstract
Effects of genetic group, period and season of calving and lactation order on milk and fat-corrected milk (FCM) yield, age at first calving and yields and percentages of fat and non-fat solids (SNF) were studied on 808 lactation records of crossbred cows. Heritabilities and genetic and phenotypic correlations were calculated after adjusting the data for significant effects, using data from 15 Friesian, nine Brown Swiss and nine Jersey sires with at least five daughters per sire. Genetic group and period of calving significantly affected all the traits under study (P < 0.01), whereas order of lactation significantly affected the yields of milk, FCM, fat and SNF only. Age at first calving was shortest (890. days) for Jersey-Hariana halfbred cows. Friesian-Hariana cows were superior in terms of yield of milk, FCM, fat and SNF, while Jersey-Hariana cows were superior for percentage of fat and SNF. Animals which calved during the first and second periods were better, for all the milk quantity and quality traits. Yields of milk, FCM, fat and SNF increased with parity up to third lactation. Heritability estimates of all milk quantity and quality taits were high (0.47-0.50). Genetic and phenotypic correlation between yields of milk, FCM, fat and SNF were high and positive.
