Abstract

Little information is available regarding the Ca dynamics and how its concentration is influenced following the Ca treatment (injection or bolus) after calving in dairy cows. To evaluate the short- and long-term effects of different sources of calcium (Ca) supplement to animals fed anionic diets during the prepartum period, thirty-six multiparous Holstein cows were randomly assigned to one of three treatments: 1) control group without Ca supplement (CON); 2) subcutaneous injection of 500 ml of 40% w/v Ca borogluconate immediately post calving (SUB); and 3) oral supplement of Ca bolus containing 45 g Ca immediately and 24 h post calving (BOL). Serum concentrations of Ca, P and Mg were measured. Serum concentration of Ca was affected by treatments at 48 h of post calving (P < 0.01). The mean Ca at 6 h was greater in SUB compared to CON group (2.34 vs. 2.01 mmol/L; P < 0.002). The lowest Ca concentration at 12 h was related to CON cows compared with BOL and SUB cows (1.90, 2.16 and 2.14 mmol/L, respectively; P < 0.02); a similar trend was observed 24 h post calving (P < 0.02). Serum concentrations of P and Mg were not influenced by treatments. Yield of milk, milk protein, and fat corrected milk were lowest (P < 0.05) in SUB cows within 3 weeks of lactation in comparison to CON and BOL cows. However, milk yield and milk composition did not show any difference among treatments throughout the first 3 months post calving. In general, under conditions of this experiment, Ca supplements to fresh cows as an oral bolus is recommended in comparison to subcutaneous injection.