Exploring the Effects of Oral Calcium Bolus Supplementation on Serum Minerals and Energy Balance Indicators in Simmental Cows Fed a Prepartum Anionic Diet

Calcium disorders remain a major challenge during the transition period of dairy cows, and oral calcium supplements are widely used to prevent postpartum hypocalcemia. This study evaluated the effects of administering an oral Ca-bolus containing calcium sulfate, acetate, and formate on postpartum mineral status and energy balance in multiparous Simmental cows. Twenty cows (mean parity 3.5 ± 0.51) were fed a prepartum diet with a negative dietary cation-anion difference (DCAD) and enrolled at calving if body condition score was between 3.0 and 3.5 and urine pH ranged from 6.2 to 6.8 during the wk before parturition. Animals were blocked by parity and randomly assigned to a control group (<i>n</i> = 10) or to a treatment group (<i>n</i> = 10) receiving two oral boluses (each 175 g; 45.14 g calcium plus 40,250 IU vitamin D₃), administered immediately after calving and 24 h later. Blood samples were collected up to 48 h postpartum for calcium, phosphorus, and magnesium analyses, and up to 14 d postpartum for glucose and β-hydroxybutyrate. Both groups were normocalcemic at calving, and no significant treatment effects were detected for any parameter at any time point. However, a short-lived numerical increase in calcium was observed 6 h after bolus administration. These results suggest that additional oral Ca supplementation may not be required in well-managed Simmental cows receiving a prepartum negative DCAD diet.