Effects of late gestation supplementation of rumen undegradable protein, vitamin E, zinc, and chlortetracycline to ewes on indices of immune transfer and productivity.

Late gestation supplementation of feed additives, such as rumen undegradable intake protein (RUIP), vitamin E, Zn, and chlortetracycline, has inconsistently improved ewe/lamb productivity. In 3 experiments, Western white-faced ewes were supplemented for at least 30 d during late gestation with 204 g/(ewe.d) on a DM basis of high (HS; 12.5% RUIP, 880 IU/kg of vitamin E, 176 mg/kg of Zn supplied by an AA complex, and 352 mg/kg of chlortetracycline) or low (LS; 7.56% RUIP and no supplemental vitamin E, Zn, or chlortetracycline) supplements. Ewes of different age (Exp. 1; 3- vs. 6-yr-old; n = 52) and BCS (Exp. 2; good vs. poor BCS; 3.0 and 1.7 +/- 0.5, respectively; n = 40) were supplemented individually in a 2 x 2 factorial arrangement of treatments for 29 d. Thereafter, each ewe was group fed the appropriate supplement until lambing (14 +/- 7 d). Ewe intake, colostral IgG, ewe and lamb parainfluenza type 3 (PI(3)) titers, milk production, ewe BW and BCS change, and lamb production were measured in both experiments. In Exp. 3, approximately 600 ewes were group fed HS or LS over 2 yr. Ewe BW, ewe BCS, lamb production, and lamb survival was measured in Exp. 3 with groups within year as the experimental unit. In Exp. 1, lambs born to 3-yr-old ewes fed the HS had greater (P = 0.01) anti-PI(3) antibody titers than lambs born to 3-yr-old ewes fed the LS. Three-year-old ewes had greater (P < 0.01) DMI than 6-yr-old ewes. In Exp. 1 and 2, d 3 and 10 milk production differences (P <or= 0.10) were detected among treatments; however, lamb production did not differ among treatments in either experiment. In Exp. 3, late gestation supplementation did not affect indices of ewe or lamb production. Under the condition of these 3 studies, late gestation supplementation of HS or LS did not affect ewe productivity. Similarly, ewe age and BCS did not affect productivity, nor did ewe age or BCS interact with type of late gestation supplement.