Effects of supplementing with calcium salts of palm oil fatty acids or hydrogenated tallow on ewe milk production and twin lamb growth.

Two experiments were conducted with Polypay ewes nursing twin lambs to evaluate the effects of supplementing fat (calcium salts of palm oil fatty acids or hydrogenated tallow) on ewe lactation. In Exp. 1, ewes were fed a 52% concentrate:48% hay-based diet (as-fed basis) consisting of alfalfa hay (n = 4), endophyte-free fescue hay (n = 4), or fescue hay with 3.7% fatty acids (n = 4) from d 4 to 56 of lactation. In Exp. 2, ewes were fed similar diets that had endophyte-free fescue hay (n = 6), fescue hay with 3.7% fatty acids (n = 5), or fescue hay with 3.1% tallow (n = 6) from d 14 before lambing until d 57 of lactation. Diet formulations with supplemental fat were more nutrient dense, and treatments were fed to meet ewe nutrient requirements; this caused diets with added fat to be offered at 10 and 17% lower rates than unsupplemented diets in Exp. 1 and 2, respectively. Lambs were maintained to consume only ewe milk. Ewe milk production and composition were determined using a portable milking machine following a 3-h separation from lambs. In Exp. 1, milk fat content was increased (P < 0.01) when ewes consumed fescue hay with fatty acids vs. the fescue hay diet (11.4 vs. 8.3%). Ewes fed fescue hay with fatty acids lost the most (P < 0.05) weight over lactation (-8.6 kg) compared with ewes fed the alfalfa hay (-2.4 kg) and fescue hay (-3.8 kg) diets. Other milk measures, lamb gain, and production efficiencies were not changed. In Exp. 2, ewes supplemented with fatty acids produced more (P < 0.05) milk fat than those fed tallow (290 vs. 210 g/d). The proportion of synthesized milk fat 14:0 was decreased (P < 0.01), but the percentage of incorporated 16:0 increased (P < 0.05) when fatty acids were fed. Dietary fat digestibility by ewes was increased (P < 0.01) by fatty acid supplementation but decreased (P < 0.01) when tallow was added. Although ewe weight measures were not changed in Exp. 2, twin lamb gain per ewe organic matter intake was most efficient (P < 0.05) when ewes were supplemented with fatty acids. Results suggest that feeding hydrogenated tallow decreased nutrient availability for ewe milk fat production. A complete diet based on endophyte-free fescue hay can replace a traditional alfalfa hay diet, whereas supplementing with the calcium salts of palm oil fatty acids may be more feasible when energy is limiting during ewe lactation.

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

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.