Work

The physiological effects of induced prepartum subclinical hypocalcemia in multiparous Holstein cows

Year: 2026

Type: article

Abstract: Subclinical hypocalcemia (SCH) is prevalent during the periparturient period in dairy cows due to increased calcium (Ca) demand for milk and colostrum synthesis. Transient SCH has been shown to activate a negative feedback loop, thereby improving Ca homeostasis. Here, we investigate the impact of induced SCH during the prepartum period on Ca homeostasis pre- and postpartum, and milk production. Thirty multiparous Holstein cows were enrolled 21 d before the expected due date, in a randomized complete block design, and were assigned to receive either a 6-h continuous intravenous infusion of saline solution (CON) or 5% egtazic acid (EGTA) solution (n = 15/treatment) for a minimum of 3 d and a maximum of 14 d until parturition. Blood samples were collected daily from enrollment to the onset of infusion, and from 1 to 49 DIM (d 1 to 49). During infusions, blood samples were collected immediately before infusion, hourly during infusion, and 1 h post-infusion termination. Milk samples were collected weekly during the initial 3 wk of lactation, and milk weights were recorded daily from d 0 to 49. Results demonstrated that prepartum EGTA treatment led to decreased ionized Ca (iCa) and total Ca (tCa) concentrations compared with the control group during the infusion. Postpartum, EGTA-treated cows exhibited higher iCa on d 0 h 12 (12 h postpartum), d 1, and d 2, and higher tCa concentrations on d 0, d 0 h 12, d 1, d 2, d 3, and d 5. Additionally, EGTA-treated cows developed resistance to induced SCH, as indicated by an increased infusion rate (IR) on d -3, d -2, and d -1 compared with the first day of infusion (622.68 ± 40.19 mL/h). We observed a treatment × day × time interaction in parathyroid hormone (PTH) concentrations, with EGTA-treated cows having higher concentrations at d -2 h 0 and d -1 h 0 compared with CON-treated cows. During the postpartum period, EGTA-treated cows had increased PTH concentrations compared with CON-treated cows. Additionally, EGTA-treated cows tended to have higher serotonin concentrations during the prepartum period compared with CON-treated cows. A treatment × day interaction on milk production was observed, with EGTA-treated cows having decreased milk yield on d 16, and d 18 to 24; however, there were no significant differences in milk production over the entire lactation period. These findings indicate that prepartum SCH induction primes Ca homeostatic mechanisms, potentially mitigating postpartum SCH.

Source: Journal of Dairy Science

DOI: 10.3168/jds.2025-27370