Abstract

The calving-to-first-service interval is crucial for dairy herd productivity. However, factors influencing this reproductive parameter remain understudied in modern dairy systems. The present study aimed to investigate the determinants of the calving-to-first-service interval in Danish Holstein cows, focusing on parity, age at first insemination, age at first calving, gestation length, gender of the born calf, and calving season. Data from 699 cows, managed on a single farm in Southwest Denmark, were collected and analyzed to identify risk factors associated with the calving-to-first-service interval. The mean calving-to-the-first-service interval was 87.6 ± 23.7 days. The present results indicated that parity, age at first calving, and calving season are key modifiable factors that affected the calving-to-first-service interval of the investigated Danish Holstein cows. The final multivariate linear regression model, which explained 13.7% of the variation in the calving-to-first-service interval, identified parity, age at first calving, and the gender of the born calf as significant risk factors for the interval. Parity and age at first calving were negatively related to the calving-to-first-service interval. Male calves were linked to an increased calving-to-first-service interval. Gestation length and age at the first artificial insemination indicated no association with the calving-to-first-service interval. Focusing on key factors such as parity, age at first calving, and gender of the born calf can improve reproductive success and profitability in dairy herds.