Supplementing metabolizable protein to ewes during late gestation: I. Effects on ewe performance and offspring performance from birth to weaning.

We hypothesized that a maternal diet greater in MP during the last third of gestation would yield improved offspring growth due to enhanced placental or mammary gland function. Our objective was to determine how MP intake during late gestation affected ewe and offspring performance from birth to weaning in ewes fed diets similar in total energy. In yr 1, maternal dietary treatments were applied at d 100 of gestation, were similar in total energy, and contained 60% of MP requirements (60MP1), 80% of MP requirements (80MP1), and 100% of the MP requirements (100MP1) on a DM basis during late gestation. In yr 2, maternal dietary treatments were similar in total energy and contained 60% of MP requirements (60MP2), 100% of the MP requirements (100MP2), and 140% of MP requirements (140MP2) on a DM basis during late gestation. In yr 1, there was no effect (P ≥ 0.30) of maternal MP restriction on gestation length, lamb birth weight, or milk production of the dam. At lambing, ewe BW (P = 0.02) and BCS (P = 0.01) increased linearly as MP in the diet increased. While there were no differences in lamb BW at birth, lamb weaning BW (P = 0.08) and ADG from birth to weaning (P = 0.10) tended to increase linearly as maternal MP intake increased. In yr 2, maternal BW increased with increased dietary MP. However, there were no significant effects (P ≥ 0.45) of maternal dietary treatment on maternal BCS or lamb birth weight. Moreover, lamb weaning weight and ADG were not influenced by maternal MP levels. These results suggest that ewes maintain and gain BW and BCS when consuming diets similar in total energy with increased MP during late gestation, but the increased MP had minimal effects on lamb performance through weaning.