Abstract

Records of 433 cows from 48 sires that had at least four daughters were used to study genetic parameters for age at first calving, 305 day milk yield, first lactation milk yield, first lactation length, first service period, first dry period and first calving interval. Data were analyzed by the procedures of Restricted Maximum Likelihood Method with animal model. Age at first calving had highest heritability of 0.53±0.116, and the estimate for all other traits found to be medium in magnitude ranged from 0.23 to 0.28. Very low phenotypic correlations of age at first calving with all other traits were observed. The phenotypic, genetic and environmental correlations of first lactation milk yield with 305 day milk yield were high and positive. All correlations of first lactation milk yield with first service period, first dry period and first calving interval were negative. High phenotypic, genetic and environmental correlations were found for service period with dry period and calving interval; and dry period with calving interval.

Key words: First lactation traits, Friesian, heritability, correlation, Holeta.