Milk production, age at first calving, and calving-toconception interval in Holstein, Brown Swiss, and Holstein x Brown Swiss cows

The objective of this study was to evaluate milk production, age at first calving, and calving to conception interval in Holstein, Brown Swiss, and Holstein x Brown Swiss crossbred cows within a pasture-based dairy system in Argentina. The increasing global demand for more resilient and locally adapted dairy systems has led to a renewed interest in crossbreeding to enhance both reproductive and productive efficiency through heterosis. We analyzed data collected over 10 years (2014-2023) from 647 first-lactation cows, including Holstein, Brown Swiss, and Holstein x Brown Swiss crossbred cows. Data were examined using a mixed-effects linear model with breed, season, and their interactions as fixed effect and year as random effect. The results showed no significant differences in milk production between breeds or seasons. However, a significant interaction between breed and season was observed for the calving-to-conception interval, with a shorter interval for crossbred cows during spring-summer (102 days), compared to Holstein cows (156 days). This finding highlights a potential advantage of crossbreeding in reducing open days during the warmest months, thereby enhancing reproductive efficiency in pasture-based systems. This study suggests that crossbreeding can be a viable strategy for improving reproductive performance of dairy systems while maintaining similar milk yield compared to the other breeds, particularly in grazing systems. Highlights: • Crossbreeding is increasingly considered in Argentina to improve resilience and efficiency in pasture-based dairy systems. • Milk yield, age at first calving, and calving-to-conception interval in 647 first-lactation cows over a ten-year period were evaluated. • No significant differences were found among breeds (Holstein, Brown Swiss cows and their cross) for milk yield or age at first calving. • A significant interaction between breed and season was detected for calving-to-conception interval. • Crossbred cows showed a shorter calving-to-conception interval than Holstein cows during spring and summer (102 versus 156 days).