A potential strategy for decreasing milk production in the ewe at weaning using a growth hormone release blocker2

Abstract

Following the loss or removal of ewes' lambs, ewes frequently continue to lactate for a short time, which potentially predisposes them to mastitis. Therapies that stop or reduce milk production in such situations would be beneficial. Milk production in ruminants is positively correlated with serum concentrations of growth hormone (GH). We sought to determine whether methscopolamine bromide (MB), an anticholinergic agent reported to block GH secretion, would selectively and reversibly reduce milk yield in lactating ewes. White-face ewes (n = 24) that were nursing lambs were assigned on d 59 +/- 2 postpartum (d 0) to receive s.c. injections of 96 mg of MB on d 2, 3, and 4 (1630). On d 0, 2, 5, and 7 (0900), ewes were sequentially separated from their lambs, treated with 40 IU oxytocin, and 30 s later were milked. Ewes remained separated from their lambs for 6 h, after which (1500) ewes were again milked and quantity of milk was determined. Milk yields at d 0, 2, 5, and 7 were 267 +/- 16.9, 266 +/- 15.5, 225 +/- 11.9, and 244 +/- 13.4 g, respectively. It was concluded that treatment of ewes with MB reduced milk yield (P < .01), and the effect was reversible. A second experiment was performed to determine the acute effects of MB on serum concentrations of GH. Hampshire ewes (n = 14) that were nursing lambs were assigned on d 55 +/- 1 postpartum to receive a.s.c. injection of saline (n = 7) or 96 mg of MB (n = 7) at min 0.(ABSTRACT TRUNCATED AT 250 WORDS)