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Effects of conventional and delayed postpartum calcium bolus strategies on milk production, serum metabolic status, and reproductive outcomes in high-producing Holstein cows
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DOI：10.1016/j.anifeedsci.2026.116831.png)
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Abstract
En 中文
Postpartum hypocalcemia remains a significant challenge in high-producing dairy cows, with most calcium (Ca) supplementation protocols targeting the first 24 h after calving. This study evaluated the effects of conventional oral Ca bolus supplementation and a repeated dose administered later during the first week of lactation on production, metabolic, and reproductive outcomes in Holstein cows. A total of 200 cows (305-d milk yield = 13,506 ± 3,331 kg; parity = 2.78 ± 1.32) were randomly assigned to 4 groups: control (CON, no bolus) and 3 treatment groups receiving a bolus at calving only (B0), at calving and day 3 postpartum (B0+3), or at calving and day 7 postpartum (B0+7). Average milk yield during the first 100 d postpartum was higher in cows receiving two Ca boluses at calving and 3 d later (43.7 kg/d) compared with cows supplemented only at calving (40.3 kg/d; P < 0.01), and was similar to CON (43.3 kg/d). Fat- and energy-corrected milk (FCM = 41.4; ECM = 41.3 kg/d) were also significantly higher in the B0+3 group than in cows receiving a single bolus at calving (FCM = 38.9; ECM = 38.8 kg/d; P < 0.01). No treatment effects were detected for milk fat, protein, or somatic cell count (P > 0.05). Parity-stratified analysis showed that multiparous cows (≥3) in the B0+3 group produced more milk (47.8 kg/d) compared with both the B0 group (43.1 kg/d; P < 0.01) and the CON group (43.3 kg/d; P < 0.01). Cows in the B0+3 group had higher (P < 0.05) blood glucose on d 4 and 8 postpartum, and higher total protein and albumin concentrations (P < 0.01), indicating improved metabolic status. Serum Ca concentration on d 4 postpartum was greatest (P = 0.03) in B0+3 cows (2.22 mmol/L), and repeated dosing reduced the incidence of hypocalcemia on day 4 postpartum (P = 0.01). Reproductive outcomes did not differ across treatment groups (P > 0.05), although B0+3 cows had a numerically shorter calving-to-first-insemination interval (P = 0.10). Overall, administration of a second oral Ca bolus on day 3 postpartum was associated with improved metabolic indicators and greater milk production in Holstein cows, particularly in multiparous cows (≥3).
Keywords:
calcium bolus
postpartum hypocalcemia
milk production
metabolic status
Holstein cows
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