Evaluation of the potential effects of abortion on the productive performance of Iranian Holstein dairy cows

Calving records from the Animal Breeding Center of Iran collected from January 1983 to December 2007 and comprising 1 163 594 Holstein calving events from 2552 herds were used to evaluate the potential effect of abortion occurrence on 305‐day milk yield, milk fat yield, fat percentage of milk and milk protein yield in Iranian Holsteins. Statistical analyses of production traits were performed using a linear mixed model procedure. Normal‐calved cows had greater 305‐day milk production, fat yield and protein yield of milk than abortive‐calved cows (P < 0.05). However, abortive‐calved cows had the greater milk fat percentage than normal calved cows (P < 0.05). The linear and quadratic effects of age of dam were significant on all of the studied traits (P < 0.05). The results of regression analysis showed that increase in the quadratic effect of age can cause an increase in the fat percentage of milk for all calvings including normal and abortive calvings. Because abortion is one of the most important conditions that limit a cow's ability to produce, maintaining the general health of cattle is important in minimizing the risk of abortion problems.