Department of Animal Sciences, College of Agriculture, Shiraz University, Shiraz, Iran
The purposes of this study were to estimate the effects of risk factors on stillbirth parturition and evaluate the effects of stillbirth on lactation performance in Holstein dairy cows. Data were obtained from a dairy cattle herd located in Isfahan province, Iran. The logit of the probability of stillbirth was modeled using logistic regression and the effect of stillbirth on lactation performance was analyzed through mixed linear model using 12283 lactation records on 5201 cows. The results showed that 6% of the calves born die within 48 h of birth. The results of logistic regression analysis demonstrated that the frequency of stillbirth is significantly influenced (P<0.05) by calving year, parity number and calving difficulty. The stillbirth frequency was found to be significantly higher for first parity cows, (P<0.05). Also, calving difficulty was shown to be significantly associated with increased risk of stillbirth (P<0.05). Mixed linear model analysis results demonstrated that stillbirth significantly reduced milk and fat yield (P<0.05), but had no significant impact on milk fat percentage (P≥0.05). The 305-d milk and fat yields for cows with stillbirth were estimated to be 8274.17 ± 100.79 and 245.60 ± 3.7 kg compared to 8865.60 ± 88.16 and 259.36 ± 3.2 kg for cows that had a live calf, respectively.