Department of Anima/ Breeding and Genetic. University of Agriculture, Faisalabad;
^IDirectorate of Livestock and Dairy Development, Peshawar, NWFP

Abstract   

    Data on production performance of 90 imported Dutch Holstein-Friesian cattle and their 127 Pakistani- born progeny from 1982 to 1991 were analyzed. The mean first lactation 305-day milk yield for imported and Pakistani-born cows was 3196.7 ± 66.36 and 2418.3 ± 104.65 litres respectively (P<0.05). The overall 305-milk yield for the two groups was 3356.53 ± 244.25 and 2493.51 ± 106.89 litres, respectively. The effect of year of calving was non-significant on first lactation (305-day) milk yield, while it was significant (P<0.05) for 305-day overall average milk yield. For all lactations the cows calved in 1988 gave maximum (3370.0 ± 306.9 litres) average 305-day milk yield and 1984-calvers gave the minimum (2713.0 ± 67.35 litres) overall lactation milk yield. Month of calving had significant effect on first lactation 305-day milk yield and overall 305-day milk yield. Maximum first lactation milk yield was obtained from cows calved in April (4073.0 ± 181.31 litres) and minimum for cows calved in February (2259.9 ± 126.69 litres) in first lactation. An overall basis, cows calved in October yielded maximum (3397.4 ± 37.17 litres) milk and those calved in .June gave the minimum (2472.2 ± 61.35 litres) milk yield

Key words: Year and month of calving, 305-day milk yield, Holstein Friesian cows