Comparative efficacy of three postpartum oral calcium formulations on metabolic dynamics, behavior, and performance in Holstein cows

This study aimed to evaluate the comparative efficacy of three oral calcium supplementation strategies of distinct chemical formulations (an active vitamin D 3 -based bolus, a calcium chloride/sulfate-based bolus, and a calcium formate/acetate/sulfate-based bolus) on acute blood gas dynamics, mineral kinetics, and metabolic profiles (at 0, 12, 24, and 48 h postpartum), as well as their long-term impacts on annual milk yield, electronic sensor-monitored behavioral patterns, and reproductive performance in primiparous and multiparous Holstein cows. Ninety cows (45 primiparous, 45 multiparous) were assigned to three equal treatment groups. Blood parameters were analyzed using Linear Mixed Models with 0-h baseline values incorporated as covariates. Continuous 1-year follow-up data for milk yield, eating/rumination durations, and fertility were evaluated. The active vitamin D 3 -based bolus sustained the highest and most stable ionized calcium (1.36 ± 0.03 vs. 1.39 ± 0.04 mmol/L) and total calcium (8.27 ± 0.23 vs. 8.20 ± 0.24 mg/dL) levels at 48 h postpartum in primiparous and multiparous cows, respectively. The calcium chloride/sulfate bolus induced an early peak in ionized calcium at 12 h (1.23 ± 0.03 mmol/L for primiparous; 1.25 ± 0.04 mmol/L for multiparous), followed by a steady decrease. Meanwhile, the calcium formate/acetate/sulfate bolus showed a slower release pattern, marked by a transient ionized calcium at 24 h. Despite these distinct acute physiological responses, no significant long-term differences were observed among treatment groups regarding annual milk yield, rumination time, inseminations per pregnancy, or pregnancy rates ( p > 0.05). Daily eating time was significantly longer in primiparous cows than in multiparous cows ( p = 0.012). In conclusion, while oral calcium formulations offer specific short-term metabolic advantages during early transition, these transient benefits may not necessarily translate into long-term performance improvements, suggesting that oral calcium bolus supplementation may be more beneficial for meeting acute mineral requirements rather than providing extended productivity enhancements.