Calcium status of multiparous Holstein cows during early lactation and its association with the health and production of 3 grazing dairies in Antioquia, Colombia.

Periparturient hypocalcemia in dairy cows is known to negatively affect health and milk production. The grazing-based dairy industry of Colombia is the fourth largest milk producer in Latin America and is rapidly growing. However, with renewed commitments to sustainable intensification, Colombia may be disproportionately affected by poor forage quality and periparturient diseases due to limited access to technology and infrastructure. The primary objective was to assess the prevalence of subclinical hypocalcemia (SCH) across 3 commercial dairy farms in Antioquia, Colombia, and its association with milk production. Second, the study sought to evaluate associations of SCH with risk of disease and culling. Multiparous Holstein cows (n = 136) were enrolled in a prospective cohort study design on 3 farms in Antioquia, Colombia, from July to December of 2023. Serum concentrations of total calcium were analyzed prepartum, between 1 and 10 d before expected calving, as well as postpartum at 1, 2, 4, and 7 DIM. Cows were assigned either as eucalcemic (EU) or SCH based on the mean total calcium serum concentration at 4 DIM in this study (EU >2.40 mmol/L and SCH ≤2.40 mmol/L). Milk production was recorded daily. The SAS MIXED procedure with repeated measures was used to analyze differences between EU and SCH cows and respective milk production. The prevalence of SCH was 39%. Pre- and postpartum blood total calcium were greater in EU than SCH (differences prepartum = 0.23 mmol/L and postpartum = 0.37 mmol/L). Cows classified as EU had greater milk yield (difference 1.3 kg/d) and ECM (difference 1.0 kg/d) than SCH cows, without changes in risk to disease or culling. Overall, SCH is a relevant challenge in grazing systems in Colombian dairy herds and may affect the production and may unduly affect disease, culling, and reproduction outcomes.