Influence of intramammary infusion of calcium on the calcium status of periparturient lactating dairy cows.

Sixteen multiparous pregnant cows (14 Holsteins and 2 Jerseys) were arranged in a randomized complete block design and assigned to intramammary infusion of Ca (8 cows) or intramammary infusion of distilled, deionized water (8 cows). Beginning 1 wk before expected calving, plasma Ca concentration was monitored daily until calving. Immediately after the first milking postpartum, an initial (0-h) blood sample was collected via a jugular catheter; then 40 ml of either a 50% Ca borogluconate solution containing 1.6 g of Ca or 40 ml of distilled, deionized water were infused in the right forequarter of the udder. Changes in plasma Ca concentration were monitored every 10 min for the 1st h and then hourly thereafter until the next milking. This infusion and sampling protocol was applied for three consecutive milkings (36 h). Milk Ca concentration from individual quarters for each milking also was monitored. Cows infused with water had lower milk Ca concentration in the infused quarter than in the uninfused quarters during the third and fourth milkings postpartum. Milk Ca for cows infused with Ca was higher in infused quarters than in uninfused quarters at the second milking postpartum. However, this difference lessened during the third milking and was reversed during the fourth milking. Plasma Ca concentration of control cows decreased toward the end of each 12-h sampling interval but was much more stable for cows infused with Ca. The enhanced ability of cows infused with Ca to maintain plasma Ca concentration postpartum might translate into improved transition from nonlactating to lactating diets and could potentially reduce the incidence of metabolic disorders during the periparturient period. However, this response and potential side effects, such as the possibility that mastitis could accompany intramammary infusion of Ca, should be evaluated further before adopting this procedure.