Some Factors Affecting Twinning Rate and Its Effects on Postpartum Reproductive Performance of Friesian Cows

A total number of 1243 records of calving cases of 585 dairy Friesian cows during 8 consecutive years from 1997 to 2004 collected from Sakha Animal Production Research Station belonging to Animal Production Research Institute, Agriculture Research Center were used to study the effect of sire, live body weight (LBW) and age of dam and calving season on twinning rate and its consequent effects on postpartum reproductive performance of dairy Friesian cows. Results indicated that, the average of twinning rate was 4.67% and freemartin rate was 0.64%. Sire, live body weight, age of dam and calving season had significant (P<0.05) effects on twinning rate. Twinning rate increased significantly (P<0.05) with increasing live body weight and age of dams. Winter season significantly showed the lowest (P<0.05) twinning rate (3.76%) and autumn season had the highest rate (6.20%). Twins calving affected significantly (P<0.05) all the reproductive performance under consideration except the period from calving to the first service and gestation period. In this respect, the service period, days open and calving interval were longer, number of services per conception was higher, while conception rate was lower for twins compared with single calving. The percentages of retained placenta, dystocia, abortion and born death calf were significantly (P<0.05) higher with twins calving compared to single calving. These results indicated that, several factors (genetic and environmental) affected on twinning rate in dairy Friesian cows. Calving interval for cows calved single or twins was in rate accepted, while retained placenta, dystocia, abortion and born death calf were nearly duplicate in cows calved twins compared to that of single calving.