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Effects of Prepartum Energy Intake on Steroids During Late Gestation and on Cow and Calf Performance¹

University of Georgia, Athens 30602

Abstract

At 50 d prior to predicted calving, 37 multiparous Angus cows were grouped by sire of mating, age and weight of cow and placed on either a high energy (HE, n=19) diet or a moderate energy (ME, n=18) diet. Objectives were to determine the effect of prepartum nutrition on: 1) prepartum serum concentrations of estrone (E₁), estrone sulfate (E₁ SO₄) and progesterone (P₄); 2) pre- and postpartum cow body weight changes; 3) calf birth weight and 4) cow and calf postpartum performance. The ME cows were group-fed Coastal bermudagrass hay ad libitum and dormant pasture; HE cows were group-fed 2.7 kg ground corn·head^-1 ·d^-1 in addition to the ME treatment. Both groups were combined and fed identically after calving. Cows fed HE were heavier (P<.01) than cows fed ME at d 10 prepartum and their calves were heavier (P<.05) at birth and weaning than calves from cows fed ME. Serum E₁ concentrations were not significantly different between groups, but serum E¹ S0⁴ was higher (P<.01) at d 10 prepartum in ME cows compared with HE cows. Serum P₄ concentrations of ME cows were higher (P<.05) than those of HE cows. Cow body weights were greater (P<.01) for the HE group than for the ME group during the first 6 mo postpartum. Cow rebreeding performance was identical for both groups.

¹ This research was supported by State and Hatch funds allocated to the Georgia Agr. Exp. Sta. The authors thank Dr. George B. Rampacek, Dept. of Anim. and Dairy Sci., Univ. of Georgia and Dr. Robert R. Kraeling, Richard B. Russell Agr. Res. Center, USDA, for their help in the preparation of this manuscript. The authors also thank Dr. David Guthrie, USDA, Beltsville, MD for E₁ and E₁ SO₄ antisera; Mr. Ken Dorough for assistance in the E₁ and E₁ S0₄ validation procedure; and Ms. Del Little for statistical help.

² Dept. of Anim. Sci., Kansas State Univ., Manhattan 66506.