Submitted to: Ag Research Reports - Project Summary Reports
Publication Type: Experiment Station
Publication Acceptance Date: 7/22/2008
Publication Date: 12/15/2008
Citation: Looper, M.L., Reiter, S.T., Nabhan, S., Flores, R., Bailey, C.R., Jr, B.A., Jr, R.C. 2008. Body condition and forage type influence intramuscular and rump fat, and reproductive performance of postpartum Brahman-influenced cows. Ag Research Reports - Project Summary Reports. 563:50-52.
Interpretive Summary: Thin beef cattle that do not get pregnant at the end of the breeding season reduce profitability of beef production. A 10% increase in the annual U.S. calf crop would allow production of the same amount of beef from 12% fewer cows. Body condition indicates a cow’s relative fatness. Cattle grazing toxic tall fescue usually exhibit fescue toxicosis that can reduce reproductive performance. The direct effect of toxic fescue on reproductive performance of cows is not fully understood. Scientists from ARS in Booneville, AR and the University of Arkansas compared estrus, body fat, and reproductive performance of fat and thin cows grazing either tall fescue or bermudagrass pastures. Cows grazing toxic fescue during the breeding season became thinner, and thinner cows that grazed tall fescue had lower pregnancy rates than fatter cows. Fatter cows were more tolerant of the negative effects of consuming toxic fescue. Knowledge of toxic fescue and cow body condition relationships during the breeding season may aide beef producers in increasing the number of pregnant cows in their herd. Producers should make certain that cows have adequate body condition, either by feeding grain or allowing cows to graze non-toxic pastures, if toxic fescue pastures are used in the breeding season. This information is important to livestock producers and extension personnel.
Technical Abstract: Multiparous Brahman-influenced cows were managed to achieve marginal (BCS = 4.9 ± 0.1; n = 55) or moderate (BCS = 6.5 ± 0.1; n = 55) body condition (BC) to determine the influence of forage type on estrous characteristics, intramuscular fat percentage (IMF), rump fat (RF), and reproductive performance. Cows within each BC were randomly assigned to graze either common bermudagrass (CB; n = 3 pastures) or endophyte-infected tall fescue (EI; n = 3 pastures) during a 60-d breeding season. Body weight and BC were recorded during the breeding season (d 0, 30 and 60). Cow IMF and RF were measured via ultrasonography at initiation and termination (d 60) of the breeding season. Cows grazing CB tended (P = 0.07) to have an increase in BC during the breeding season than cows grazing EI. At d 60, IMF and RF were less (P < 0.01) in marginal BC cows compared with cows in moderate BC. Cows grazing CB had increased RF during the breeding season while cows grazing EI lost RF (P < 0.05). Number of mounts, duration of estrus, and quiescence between mounts did not differ (P > 0.10) between forage type, BC, or both. Pregnancy rates were similar (P > 0.10) among moderate (90%) and marginal (87%) BC cows grazing CB and moderate BC cows grazing EI (88%); however, marginal BC cows grazing EI tended (P = 0.09) to have decreased pregnancy rates (68%). Cows grazing EI during the breeding season lost adipose stores, and pregnancy rates tended to be lower in marginal BC cows grazing EI.