Reducing milk production in ewes at weaning using restricted feeding and methscopolamine bromide.

Abstract

Restricted feed (RF) and methscopolamine bromide (MB), an anticholinergic agent reported to block growth hormone secretion, were evaluated as potential means for reducing milk production in ewes at weaning. On d 58 +/- 1 postpartum (d 0), 40 fall-lambing ewes were allotted to treatments in a 2 (RF vs full feed [FF]) x 2 (MB vs saline [SAL]) factorial arrangement according to breed, age, and number of lambs born and suckled. On d 0 at 0800, ewes were separated from lambs, injected with 40 IU of oxytocin, and machine milked 30 s later. Ewes remained separated from lambs for 3 h, and at 1100 they were milked and yields were determined. From d 0 through 6, FF ewes received a daily ration of 1.8 kg of alfalfa hay and .9 kg of corn; RF ewes received only 1.8 kg of alfalfa hay. On d 7 at 0800 and 1400, ewes were separated from lambs, milked, treated with a s.c. injection of either 96 mg of MB dissolved in 2 mL of SA or SA alone, and after 3-h separations were milked at 1100 and 1700 and yields determined. Lambs were weaned at 1400. After milking at 1700, all ewes were placed in drylot without feed or water. At 1100 on d 9, residual milk yields were collected. Milk samples were retained for compositional analysis at each collection time. The RF ewes produced less milk than FF ewes (106 vs 137.4 g; P < .01) at 1100 on d 7, but yields of MB and SA ewes were similar. At 1700 on d 7, milk yield was only 15.9 g less (74.3 vs 90.2 g; P < .10) for RF than for FF ewes, but it was 26 g less (69.2 vs 95.2 g; P < .01) for MB than for SA ewes. On d 9, there was no significant difference in yields of RF and FF ewes; however, MB ewes continued to produce less milk than SA ewes (96.6 vs 125.4 g; P < .10). No significant interactions between feeding regimen and MB treatment were found for milk yield. These data provide evidence that MB treatment of ewes is effective in reducing milk production. Furthermore, even greater reduction can be achieved when MB is combined with RF.