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Effects of Energy and Lasalocid on Productivity of First-Calf Heifers¹

Kansas State University, Manhattan 66506

Abstract

One hundred forty-three crossbred, fall-calving first-calf heifers were used to determine the effects of two levels of energy and two levels of lasalocid on cow-calf productivity. Diets fed for approximately 110 d prepartum were calculated to provide a daily intake of 15.3 (LE) or 18.0 (HE) Mcal ME; diets fed for approximately 130 d postpartum were calculated to provide a daily intake of 17.8 (LE) or 21.0 (HE) Mcal ME. Two supplements were fed with each energy level to provide a calculated 0 (C) or 200 mg·hd^–1·d^–1 lasalocid (L). Heifers fed HE gained .06 kg more (P = .08) per day prepartum than LE heifers. There was an interaction (P < .05) between treatment and prepartum days on trial for heifer weight approximately 2 wk prepartum and body condition at calving. Energy had no effect on heifer weight at 2 wk prepartum or condition score at calving when estimated and compared at 90 d on trial. However, regression estimates for 130 d on trial showed that HE heifers would have been 19 kg heavier (P < .001) and would have had .4 unit higher condition score (P < .01) than LE heifers. Energy and lasalocid had no effect (P > .05) on hip height or pelvic area at calving or on calf birth weight, calving ease score or gestation length. Cows fed HE weighed 17 kg more (P < .05) and had .5 unit higher (P < .001) condition score than LE cows at approximately 130 d postpartum. Lasalocid had little effect on postpartum changes in weight or body condition. Lasalocid supplementation to the LE diet tended to increase milk production and calf weight, whereas supplementation to the HE diet did not. Feeding the LE diet decreased (P < .05) cycling activity by 18 percentage points and decreased (P < .01) overall pregnancy rate by 25 percentage points. Lasalocid had no influence on reproductive performance.

¹ Contribution No. 89-57-J from the Kansas Agric. Exp. Sta.

² Present address: Dept. of Anim. and Range Sci., South Dakota State Univ., Brookings 57007.

³ Dept. of Anim. Sci. and Ind. Appreciation is expressed to Hoffmann-LaRoche Inc., Nutley, NJ for supplying lasalocid sodium (Bovatec^tm) and partial financial support and to L. A. Peterson, Hoffmann-LaRoche, for his assistance in conducting this trial.

⁴ Dept. of Stat.