Abstract   

    The data on 659 and 681 records of different crosses of Holstein-Friesian X Sahiwal crossbreds on age at maturity (first observed heat) and age at first conception respectively were analyzed. The data was spread over 17 years from 1974 to 1990. The overall least squares means and SE for age at maturity and age at 1^st conception were 618.42, 6.78 and 697.51, 8.03 days, respectively. The significant effect of year of birth and genetic groups was observed in both the traits while the effect of season of birth was non significant for age at I SI conception and significant for age at maturity .It was observed that 3/4 crosses has significantly lower age for both the traits.    

Key words: Holstein-Friesian X Sahiwal cows, maturity age, conception, factors affecting.