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ARS Home » Midwest Area » Lexington, Kentucky » Forage-animal Production Research » Research » Publications at this Location » Publication #257105

Title: Performance and physiology of steers grazing toxic tall fescue as influenced by feeding soybean hulls and implanting with steroid hormones

item CARTER, JESSICA - University Of Kentucky
item Aiken, Glen

Submitted to: Agricultural Experiment Station Publication
Publication Type: Experiment Station
Publication Acceptance Date: 7/28/2010
Publication Date: 9/1/2010
Citation: Carter, J.M., Aiken, G.E. 2010. Performance and physiology of steers grazing toxic tall fescue as influenced by feeding soybean hulls and implanting with steroid hormones. Agricultural Experiment Station Publication. Pgs 27-32.

Interpretive Summary: Tall fescue is widely utilized as forage in the upper transition zone of the USA because of its agronomic qualities, including ease of establishment, tolerance of heat, drought, and insects. However, cattle grazing tall fescue infected with a fungal endophyte produce ergot alkaloids that cause a toxicosis. Cattle undergoing toxicosis typically have an unthrifty appearance and perform poorly. Beef calves grazing toxic tall fescue typically have very low daily weight gains do not achieve targeted growth rates (<1.0 lb/d), have reduced serum prolactin concentrations, and do not shed rough hair coats in the early summer. However, cattle could be implanted with steroidal hormones and fed concentrate or by-product feeds to improve growth rates and thriftiness. An experiment was conducted with steers grazing endophyte-infected tall fescue to determine if combining feeding of pelleted soybean hulls with steroidal implantation have additive effects on weight gain and severity of toxicosis. Combining feeding of soybean hulls with implantation provided a 71% increase in average daily gain over the control treatment. Steers fed soybean hulls also had higher serum prolactin concentrations and a higher percentage of these steers shed their rough hair coats during the summer. Results indicated that steers on endophyte-infected tall fescue can be fed soybean hulls and implanted with steroid hormones to substantially improve performance and reduce the severity of toxicosis.

Technical Abstract: A grazing experiment with steers grazing toxic tall fescue indicated that feeding pelleted soybean hulls in conjunction with steroid hormone implants can increase steer weight gain, and feeding soyben hulls can reduce the severity of fescue toxicosis Ergot alkaloids produced by a fungal endophyte that infects tall fescue adversely affect cattle weight gain and physiology. Sixty-four steers were grazed on endophyte-infected (E+) KY-31 tall fescue for 77 days in 2007 and sixty steers were grazed for 86 days in 2008 to evaluate the combined effects of implantation and feeding soybean hulls on performance and physiology. With or without feeding soybean hull treatments (5.0 lb/steer/day) were randomly assigned to 6, 7.5-acre pastures. Treatments of with or without ear implantation with steroid hormone (200 mg progesterone – 20 mg estradiol) were assigned to groups of five or six (4 pastures in 2007) steers within each pasture. Average daily gain, rectal temperature, serum prolactin, and hair coat rating responses to soybean hulls and hormone implants were measured. Combining feeding soybean hulls with hormone implants can provide cost effective increases in average daily gain and reductions in the severity of toxicosis to make it a management option in producing stocker calves on toxic tall fescue.