Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2000
Publication Date: 11/1/2000
Citation: Freetly, H.C., Ferrell, C.L., Jenkins, T.G. 2000. Timing of realimentation of mature cows that were feed-restricted during pregnancy influences calf birth weights and growth rates. Journal of Animal Science. 78:2790-2796.
Interpretive Summary: In many cow-calf management programs, supplemental feed is provided during periods of low-grazed forage availability. This supplemental feed can represent a large proportion of the total cost of a cow-calf production system. Feed restriction was imposed during the second trimester and cows were allowed to gain weight during the third trimester or after their calf was born. This study suggests that allowing mature cows to decrease to moderate body condition score during the second trimester of pregnancy and allowing them to regain the body condition score during the third trimester offers a potential management tool that modifies the time that feed resources are used without decreasing calf production.
Technical Abstract: The objective was to determine the effect of feeding strategies that allowed weight loss followed by weight gain on the efficiency of feed utilization for calf production. The first treatment (H-H-H) was designed to maintain body condition score of mature cows at 5.5 from the second trimester until the subsequent breeding season. The second treatment (L-H- -H) was designed such that cows lost body condition during the second trimester and regained it during the third trimester and were equal in weight and body condition scores at parturition to cows assigned to the H- H-H treatment. The third treatment (L-L-H) was designed such that cows lost body condition during the second trimester and gained body condition after 28 d of lactation so that they would be equal to the other two treatments at breeding. Forty-eight cows were assigned to each treatment. Total DM intake over the entire study did not differ between the H-H-H and L-H-H treatments (P = .23) but both were higher than the L-L-H treatment ( = .0001). Calf birth weight of the H-H-H treatment did not differ (P = .43) from those of L-H-H but both were greater than those of the L-L-H treatment. At 28 d H-H-H (P = .008) and L-H-H (P = .007) calves weighed more than the L-H-H calves but at 58 d of age there was no difference in calf BW among the treatments (P = .81). The percentage of cows that were diagnosed pregnant at weaning with their next calf did not differ (P = .71). The results of this study suggest that weight cycling in mature beef cows is a viable management tool for reducing feed cost.