Analysis of Calving Ease and Stillbirth and Their Impact on the Length of Functional Productive Life in Slovak Holstein Cattle

SIMPLE SUMMARY: One of the important goals of cattle breeding is increasing the longevity of cows, which is one of the most important economic traits. In our work, we focused on investigating the effects of factors that could be the cause of cow culling before they reach their maximum potential. Calving difficulty and the proportion of stillborn calves reduce the length of the productive life because cows with problematic calving are often culled from the herd. For the farmer, these traits represent additional costs for veterinary procedures and related treatment after calving. We found that factors such as milk production level, parity, age at first calving, herd size, calf sex, herd–year–season, calving ease, and stillbirth had a significant effect on the longevity of cows. The research confirmed that the incidence of difficult births and the proportion of stillborn calves was higher in primiparous cows than in multiparous cows. Our analysis showed that female calves were born more easily than male calves. By selecting animals aimed at reducing the number of difficult calving and the number of stillborn calves, a higher functional, productive life in cows could be achieved. ABSTRACT: The aim of the study was to determine the frequency of births according to the categories of calving difficulty and stillbirths and to evaluate the effect of these factors on the longevity of cows. Longevity is one of the traits that affect the overall profit in the dairy industry. A Weibull proportional hazard model was used to evaluate the influence of functional traits such as calving ease and stillbirth. Longevity was expressed as the length of a functional, productive life from the first calving to death or censoring, which was corrected for milk yield. The database included 918,568 calvings, where calving without assistance represented 83.34%, calving with the assistance of one person or the use of a slight mechanical pull represented 14.47%, difficult calving with the assistance of several people, the use of mechanical traction or the intervention of a veterinarian represented 2.16%, and cesarean section represented 0.03%. The mortality of calves, stillborn or dead within 48 h of birth, represented 1.07% and 6.59%, respectively. The frequency of alive female calves was higher (46.84%) than male calves (45.50%). Cows with higher lactations had almost half as many stillborn calves as heifers. The most stillborn calves were found in difficult births (59.48%). In easy calving, this proportion was 2.48%. Using survival analysis, we estimated the significant influence of the factors such as parity, milk production, herd size, age at first calving, herd × year × season, sex of calf, calving ease, and stillbirth on the length of the functional, productive life of cows. The risk of early culling of the cows with moderately difficult calving was 1.259 times higher than in the cows with easy calving. Difficult calving and cesarean section shorten the productive life, and the risk of culling reached 1.711 and 1.894, respectively. Cows that gave birth to a dead calf achieved a 2.939 times higher risk of culling compared to cows that gave birth to a live calf. In this study, a higher risk of early culling was found in cows that gave birth to a male calf. Evaluation of the calving ease and stillbirth can be used as indirect indicators at an earlier age of the animal in the selection process for long-lived animals with good productive and reproductive performance.