Supplementing metabolizable protein to ewes during late gestation: II. Effects on ewe lamb performance and reproductive efficiency.

The objective of the current study was to determine the effects of maternal MP intake in isocaloric diets during late gestation on female offspring growth from birth to breeding and measure reproductive performance of those offspring in their first breeding season. In yr 1, maternal dietary treatments were applied at d 100 of gestation, were similar in total energy, and contained 60MP1, 60% of MP requirements; 80MP1, 80% of MP requirements; and 100MP1, 100% of the MP requirements on a DM basis during late gestation. In yr 2, maternal dietary treatments were similar in total energy and contained 60MP2, 60% of MP requirements; 100MP2, 100% of the MP requirements; and 140MP2, 140% of MP requirements on a DM basis during late gestation. While there was a quadratic effect ( = 0.003) for ewe lamb birth weight with the ewe lambs from 80MP1 ewes having increased birth weights compared with ewe lambs from 60MP1 and 100MP1 ewes in yr 1, there was no effect ( ≥ 0.22) of maternal diet on growth of ewe lamb offspring thereafter. A quadratic effect ( = 0.02) was observed for the percentage of ewe lambs bred during the first 17 d of the breeding season, with more ewe lambs born to ewes fed 80MP1 bred compared with ewe lambs born to ewes fed 60MP1 and 100MP1. Ewe lambs giving birth within the first 17 d of lambing season increased ( = 0.001) linearly as MP intake increased in the maternal diet. In yr 2, there was no effect ( ≥ 0.07) of maternal MP treatment during late gestation on growth of ewe lambs and reproductive performance except ADG from birth to weaning and lamb birth weight. There was a quadratic effect ( = 0.01) for ADG from birth to weaning of ewe lambs from ewes consuming 100MP2 being increased compared with ewe lambs from ewes fed 60MP2 and 140MP2. There was a linear ( = 0.04) reduction in birth weight of lambs born to ewe lambs as the dam's maternal dietary MP intake increased. The data from the current study suggest that feeding 80% or 100% of MP requirements during late gestation may have the greatest positive impacts on female offspring reproductive performance.