EFFECT OD DIETARY CALCIUM SOAPS ON MILK-YIELD, BODY-WEIGHT, REPRODUCTIVE HORMONES, AND FERTILITY IN 1ST PARITY AND OLDER COWS

The effects were determined of dietary Ca soaps of fatty acids fed to cows to 120 DIM on milk yield, BW, peripheral concentrations of reprod uctive hormones, and fertility in primiparous and multiparous cows. Mi lk yield was increased in primiparous and multiparous cows fed Ca soap s, and milk fat and protein yields were enhanced. Body weight losses w ere greater for all cows fed Ca soaps, and this trend was greater and longer lasting in primiparous cows than in multiparous cows. Plasma tr iglyceride concentrations were elevated in multiparous cows, but FFA t ended to be higher in primiparous cows fed Ca soaps. Conception rate a t first Al was lower for primiparous cows fed Ca soaps (33%) than for controls (74%), but differences were not significant for later AI or b etween multiparous groups. No differences were apparent for plasma pro gesterone or estradiol in the luteal or follicular phases preceding th e first AI, and differences in mean luteinizing hormone concentrations were small in a 6-h window in the follicular phase. The differences i n conception rate at first AI in primiparous cows could not be explain ed on the basis of changes in peripheral hormone concentrations. The e nhanced negative energy balance in primiparous cows fed Ca soaps appar ently was related to the decrease in their conception rate.