Evaluating the effects of late-gestation supplementation on timed-artificial insemination pregnancy rates and body composition in beef cattle

Nonlactating Angus cross beef cows were used to evaluate pregnancy rates and postpartum performance following late-gestation liquid protein or dried distillers grains (DDG) supplementation. In Exp. 1, 166 multiparous cows were stratified by BW, BCS, age, and pregnancy status to receive a free-choice liquid-protein or DDG supplement fed to be isonitrogenous for 77 d during late gestation. In Exp. 2, 53 nulliparous and 36 primiparous cows were stratified similar to Exp. 1 and fed DDG at maintenance (DDG-1) or 1.2 times maintenance (DDG-1.2) energy requirements for 44 d during late gestation. Body weight and BCS were measured at initial supplementation, calving (except BW), timed AI, and weaning to determine BW and BCS change. Cows were sorted into 3 age groups (Exp. 1) and evaluated for BW and BCS change at weaning. All females were synchronized with a 7-d CO-Synch plus controlled intravaginal drug-release protocol with 72 h of timed AI. In Exp. 1, cows fed DDG had greater (P < 0.01) BW change at timed AI and weaning and greater BCS change (P < 0.05) at calving compared with cows fed liquid protein. Cows that were 3 and 4 yr old had the greatest (P < 0.01) BW and BCS change at weaning. In Exp. 2, there was no treatment effect (P > 0.10) on BW or BCS change. Timed-AI pregnancy rates were similar (P > 0.10) across treatments for both experiments. Late-gestation supplementation with DDG had positive effects on animal performance, with the greatest effect in the younger females.