Non-Genetic Factors Affecting Stillbirth and its Effects on Longevity, Production, and Reproductive Performance in Holstein Cows of Iran

The aim of this study was to determine the factors affecting stillbirth and the consequences of stillbirth on longevity, production, and reproductive performance in Holstein cows of Iran. Calving records from March 2000 to April 2009 comprising of 220,043 calvings on 102,199 cows in 33 herds were used. The results showed that 4.06% of the newborn calves died within 48 h of birth. The stillbirth rate was significantly higher for first parity cows (P<0.01). Calving difficulty significantly increased the risk of stillbirths (P<0.01). The frequency of stillbirth was lower for female calves than for males and was higher for twins than for singletons (P<0.01). Stillbirth significantly (P<0.01) reduced 305 d milk, fat and protein yield by 222 (±31), 8 (±1.12), and 6 (±1.01) kg per cow per lactation,respectively. Milk protein percentage, but not fat percentage, was affected by stillbirth (P<0.01). The mean calving interval for cows experiencing stillbirth was significantly longer than for those with live calves [410.3 (±1.17) vs. 405.5 (±1.05) d (P<0.01), respectively]. The overall mean longevity was affected by stillbirth while the shortest lifetime was observed for cows with stillbirth at their first parity (P<0.01).