The objectives were to evaluate the potential effect of prepartum plane of nutrition during midor late gestation on cow BW, BCS, blood hormone concentrations and preimplantation embryos. In Exp. 1, multiparous Angus and Angus  Simmental cows (n ¼ 33; BW ¼ 664 ± 78 kg) were fed diets formulated to provide three planes of nutrition: 100% NRC energy and protein requirement (REQ), 70% NRC requirement (70%REQ) or 130% NRC requirement (130%REQ) during late gestation (91 ± 4 to 8 ± 4 d prepartum). Cows fed 130% REQ tended to have greater BW (p ¼ 0.06) at breeding, greater progesterone concentrations (p ¼ 0.09), and fewer total embryos recovered at 84 ± 5 d postpartum (p ¼ 0.07) when compared with cows fed REQ. In Exp. 2, multiparous Angus and Angus  Simmental cows (n ¼ 35; BW ¼ 601 ± 72 kg) were fed the same diets as Exp. 1, but were fed during mid-gestation (195 to 112 ± 4 d prepartum). Cows fed REQ and 130% REQ had greater (p ¼ 0.02) BW at breeding when compared with cows fed 70% REQ. Cows fed 70% REQ and 130% REQ during mid-gestation had a greater (p ¼ 0.03) count of total embryos recovered at 86 ± 4 d postpartum when compared with cows fed REQ. In conclusion, while prepartum nutritional treatments tended to affect cow BW and BCS at breeding, effects on embryo production differed depending on the stage of gestation at which nutritional treatments were applied. ARTICLE HISTORY

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