Abstract
The present study was designed to find out the productive and reproductive potentials of cows using 50% and 75% Frisian breeding bulls with the view to judging the breeding bulls through their genetic merit of their progenies. The research work was conducted from July 2012 to June 2015 in different areas of the country using the semen of bulls maintained at the Central Cattle Breeding Station, Savar, Dhaka. Statistical analyses were performed using Statistical Analysis System, heritability and genetic parameters using variance component estimation, and breeding value was estimated using prediction and estimation computer program. The overall productive performance of the progenies using 50% Friesian breeding bulls were 257.55±0.46 days, 1746.24±17.34, 6.74±0.06 and 10.48±0.07 liters, respectively for the lactation length, lactation yield, daily milk yield and test day milk yield whereas 263.08±0.57 days, 2343.53±25.58, 8.84±0.08 and 12.59±0.09 liters, respectively for the lactation length, lactation milk yield, daily milk yield and test day milk yield of the progenies when using 75% Friesian breeding bulls. On the other hand, the overall reproductive performance of the progenies using 50% Friesian breeding bulls were 22.47±0.15 and 31.72±0.16 months for age at first service and age at first calving, 276.69±0.24 and 82.93±0.35 days for gestation length and post-partum heat period and 1.47±0.02 number for service per conception. When using 75% Friesian breeding bulls, it was 21.02±0.11 and 30.22±0.02 months, 276.06±0.06 and 91.93±0.31 days and 1.41±0.02 number for the age at first service and age at first calving, gestation length and post-partum heat period, and service per conception. The overall non-return rate of 50% and 75% Friesian breeding bulls was found to be 62.41 and 60.49%. The estimated heritability of lactation length and lactation yield was 0.28 and 0.36 for 25%; 0.34 and 0.38 for 37.5%; 0.28 and 0.28 for 50%; 0.30 and 0.32 for 62.5% Holstein crossbred progenies, respectively. But the estimated heritability of daily milk yield was 0.25, 0.25, 0.26 and 0.27 for 25%, 37.50%, 50% and 62.50% Friesian progenies, respectively. The strongest genetic (0.91) and phenotypic correlation (0.91) was found between daily milk yield and lactation yield of 25% Friesian progenies but when 50% and in 75% Friesian breeding bulls used, it was (0.96 and 0.99). It was revealed that 62.50% perform better than 37.50% Friesian progenies. So this 62.50% Friesian progenies could be used in commercial dairy farming. On the other hand, 50% Friesian progenies found superior to 25% Friesian progenies. But 50% Friesian progenies is found to be more sustainable than 62.50% Friesian progenies in farmer's level. Thus it may be suggested to maintain 62.5% crossbred cows in farm level and 50% crossbred in rural areas for maximizing productive and reproductive potentialities.