The effect of maternal inbreeding on incidence of twinning, dystocia and stillbirth in Holstein cows of Iran

Abstract

The purpose of this study was to investigate the effect of maternal inbreeding on incidence of twinning,dystocia and stillbirth in Holstein cows of Iran. Calving records from March 2000 to April 2009 comprisingof 365,021 calvings on 153,802 cows from 86 dairy herds were used. The mean level of inbreeding was0.7%, less than 37% of all animals were inbred, and a small proportion (3.45%) of inbreed animals hadinbreeding coefficients greater than 5%, with a maximum inbreeding coefficient of 38%. The overall averagetwinning and stillbirth rates were 2.7 and 3.78%, respectively. Dam parity and calving season significantlyaffected the incidence of twinning (P4.51, 4.70 and 5.23%, respectively (Pparity, calving season, calf sex and twinning (Polder cows. Gender of the calf was significantly associated with dystocia, whereas the incidence of dystocia was higher in dams delivering male calves (Phigher parity cows (Pin Iranian Holstein herds does not seem to have a significant effect on the twinning, dystocia and stillbirth rates.