Milk yield and production traits in one intensive-managed dairy farm located in central Chile

This study described milk yield (MY), fat yield (FY), protein yield (PY), somatic cell score (SCS) and lactation persistency in Holstein Friesian cows managed in an intensive indoor system in central Chile. Data from 206 cows (329 lactations; 3,021 test-day records) collected between 2022 and 2026 were analysed using fourth-order Legendre polynomials and linear models to evaluate the effects of parity, calving season and stage of lactation (SL). Multiparous cows showed higher (P < 0.05) daily MY than primiparous cows during early lactation (35.4 vs. 30.9 kg/day in SL1; 36.1 vs. 33.0 kg/day in SL2), although accumulated MY did not differ between parities (9,940 vs. 10,248 kg for primiparous and multiparous cows, respectively). In contrast, primiparous cows exhibited greater lactation persistency than multiparous cows (-0.0378 vs. - 0.0514 kg/day for primiparous and multiparous cows, respectively), indicating flatter lactation curves. Calving season significantly affected MY, with winter-calving cows producing more milk than summer-calving cows (10,325 vs. 9,862 kg, for winter- and summer-calving, respectively), particularly during mid- and late-lactation (1.0-2.1 kg/day in SL2-SL4). However, these differences were not reflected in FY and PY. Across SL, SCS was higher in multiparous than primiparous cows (4.04-4.91 vs. 3.02-3.58), but was not affected by calving season. These findings highlight the importance of parity and calving season in interpreting milk traits and designing management strategies in intensive dairy systems.