Prevention of Subclinical Hypocalcemia in Holsteins Fed an Anionic Diet and Treated With Two Calcium Boluses at the Time of Calving

ABSTRACT Background The incidence of subclinical hypocalcemia (iSCH) based on blood ionized calcium (iCa < 1.00 mmol/L) has not been investigated in Holsteins fed an anionic diet (AD) and non‐AD prepartum and treated or not treated with calcium bolus (CB) around the time of calving. Hypothesis Anionic diets supported with CB at 12 h after calving should increase iCa and reduce iSCH better than AD + non‐CB and non‐AD + CB. Animals One hundred Holsteins were allocated to 4 groups: Group 1 (AD + CB), group 2 (AD + non‐CB), group 3 (non‐AD + CB) and group 4 (non‐AD and non‐CB). Methods The animals were randomly selected according to calving order. The iCa and iSCH were analyzed at calving before CB application on postpartum days (PPD) 1, 3, and 10. Urine pH was analyzed at calving and PPD1. Results Urine pH (6.43 ± 0.26), iCa (0.90 ± 0.16 mmol/L) and iSCH (50%) were significantly different in the combined AD groups compared to the non‐AD groups at calving. Multiparous cows in combined AD groups had higher iCa and lower iSCH at calving. Group 1 had a higher iCa than groups 3 and 4. Group 2 had a higher iCa than Group 4 at PPD3. The iSCH of group 1 at PPD3 and 10 was lower than that of other groups. The iSCH decreased from 50% (PPD1) to 17% (PPD3) and 4% (PPD10) in group 1. Group 4 showed milk fever of 12%, 4%, and 4% at PPD1, 3, and 9, respectively. Conclusion Group 1 was the most appropriate protocol to increase iCa, reduce iSCH, and prevent milk fever.