The role of age at first calving in shaping production and reproductive outcomes in Italian buffaloes

The age at first calving (AFC) is a critical parameter in dairy herd management due to its impact on feeding costs, genetic progress, longevity, and thus, farm profitability. With the growing global demand for buffalo milk products, recent advancements in reproductive practices and feeding techniques have contributed to a reduction in AFC in Italy. This study investigates the impact of AFC on the productive and reproductive performance of primiparous Italian Mediterranean buffaloes. Data were collected from 50,661 animals across 115 herds, covering 362,703 first-lactation test-day records from 2013 to 2023. The study analyzed productive traits, including milk yield (kg/d), days to milk peak (DMP, d), ECM (kg/d), fat and protein contents (%), and SCS. Reproductive traits, such as calving interval (CIN, d) and days open (DO, d), were analyzed from 2013 to 2021. Repeated mixed linear models were used to assess the effects of AFC on the afore-mentioned traits, accounting for DIM, calving year and season, and, when applicable, their interactions. Results highlighted a significant reduction in AFC (from 36 to 35 mo), CIN (from 457 to 447 d), and DO (from 147 to 136 d) over the studied period. Buffaloes with AFC >42 mo produced 0.52 kg/d more milk and 0.90 kg/d more ECM, with slightly higher fat content (+0.04%) compared with those with AFC ≤32 mo. This trend was consistent throughout DIM categories. Somatic cell score was significantly lower in buffaloes with AFC between 32 and 35 mo (2.78), whereas higher SCS was observed in those with AFC ≤32 mo (2.81) or >35 mo (2.80). Buffaloes with AFC comprised between 34 and 37 mo had significantly lower CIN and DO (449–450 and 137–139 d, respectively) compared with those with both lower or greater AFC (454 and 143 d, respectively), whereas DMP was not significantly affected by AFC. As expected, likely due to the out-of-breeding technique, the highest values for both CIN and DO were observed in buffaloes calving the first time in winter and spring (on average 455 and 145 d, respectively), and lower values were recorded for those calving in autumn and summer (on average 449 and 138 d, respectively). Buffaloes with AFC ≤30 mo that calved during winter exhibited significantly greater DO (>150 d) compared with those calving with AFC >42 mo during the same period (140 d). This is likely due to the lower capacity to restore ovarian activity that may reduce fertility in younger buffaloes compared with older ones. Conversely, buffaloes with AFC >42 mo that calved in summer tended to have extended DO (139 d) in respect to those with lower AFC (≤30 mo) in the same period (135 d). This may be due to the interaction between the increased photoperiod and the reduced feed intake caused by summer heat stress, which may have an effect on older buffaloes' fertility. Therefore, AFC between 34 and 37 mo represents the optimal window for Italian Mediterranean buffaloes, combining shorter CIN and DO with sustained milk production. The reduction of AFC could significantly enhance farm profitability and may be achievable through the integration of breeding programs, better reproductive technologies across seasons, and targeted nutritional strategies during the preweaning and prepartum phases.