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 ar ranged in a randomized complete block design and assigned to intramamm ary infusion of Ca (8 cows) or intramammary infusion of distilled, dei onized 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 collec ted via a jugular catheter; then, 40 ml of either a 50% Ca boroglucona te solution containing 1.6 g of Ca or 40 mi of distilled, deionized wa ter were infused in the right forequarter of the udder. Changes in pla sma Ca concentration were monitored every 10 min for the Ist h and the n hourly thereafter until the next milking. This infusion and sampling protocol was applied for three consecutive milkings (36 h). Milk Ca c oncentration from individual quarters for each milking also was monito red. Cows infused with water had lower milk Ca concentration in the in fused quarter than in the uninfused quarters during the third and four th milkings postpartum Milk Ca for cows infused with Ca was higher in infused quarters than in uninfused quarters at the second milking post partum However, this difference lessened during the third milking and was reversed during the fourth milking. Plasma Ca concentration of con trol 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 m ight translate into improved transition from nonlactating to lactating diets and could potentially reduce the incidence of metabolic disorde rs during the periparturient period. However, this response and potent ial side effects, such as the possibility that mastitis could accompan y intramammary infusion of Ca, should be evaluated further before adop ting this procedure.