The effect of oral calcium boluses at parturition on blood metabolites and milk yield in grazing Holstein cattle

Abstract

The objective of this study was to assess the effect of oral calcium boluses at parturition on plasma total calcium (tCa), phosphorus (P), total magnesium (tMg), beta hydroxybutyrate (BHB) and milk yield during the postpartum (pp) of grazing Holstein cows. The study was conducted on a seasonal grazing dairy in Chile. Prepartum cows were fed an anionic diet (-86 mEq/kg DM). In 2019, 10 cows of parity 2, 3, and ≥ 4, respectively, were randomly assigned at parturition to a treatment group (n=30), receiving 2 boluses of oral Ca, (CaCl2, providing 44 g Ca) 24 h apart, and matched by parity to a control group (n=30). A blood sample was obtained at d 1, 2, 3, 4 and 7 pp. Milk yield was recorded until 30 d pp. Minerals and milk yield were analysed by ANOVA for repeated measures. Treatment had no effect on tCa in parity 2 cows. However, in lactation 3, Ca supplementation increased the concentration of tCa at d 2 and 3 pp, and in lactation ≥ 4 boluses tended to increase tCa at d 2 pp. Higher BHB concentrations at d 4 pp were found in treated cows than in the control cows. Milk yield in lactation 2 was lower in the treated than the control group. In lactations ≥ 3, milk yield was higher in the treated than the control group. In conclusion, two oral Ca boluses at parturition 24 h apart in grazing cattle fed anionic prepartum diets, improved Ca status and milk yield during the postpartum period in cows ≥ 3 lactations.