Performance and Physiology of Steers Grazing Toxic Tall Fescue as Influenced by Concentrate Feeding and Steroidal Implants.

Fescue toxicosis has a negative influence on animal performance and physiology, but concentrate feeding and ear implantation with steroid hormones could mitigate problems in grazing yearling cattle on toxic tall fescue.  Sixty-four steers were grazed on endophyte-infected ‘KY-31’ tall fescue for 77 days to evaluate effects of implantation with steroid hormones and concentrate feeding on performance and physiology of yearling steers.  Steers were stratified by body weight for assignment to six, 3.0-ha toxic tall fescue pastures. Treatments of with or without feeding pelleted soybean hulls (SBH) were randomly assigned to pastures as the main-plot treatments.  Steers on SBH treatment were group-fed to provide daily consumptions of 2.3 kg (as fed) steer^-1.  Sub-plot treatments of with or without ear implantation with steroid hormones (200 mg progesterone – 20 mg estradiol) were assigned to groups of five or six steers within each pasture.  Unshrunk body weights were measured at the start and finish of the grazing experiment to calculate average daily gain, and rectal temperatures and hair coat ratings were recorded at the conclusion of grazing.  Feeding SBH provided a 36% increase (P < 0.05) in average daily gain and implanting with steroid hormones improved average daily gain by 37%, but there was no interaction between the two variables in effecting performance.  Rectal temperatures were greater (P < 0.05) in cattle being fed SBH (39.2 vs 38.9°C).  There was a trend (P < 0.10) for a greater frequency of sleek hair coats with either feeding SBH or steroid implants.  Results of the experiment indicated that steers grazing toxic tall fescue can be fed SBH or implanted with steroid hormones to increase weight gain and the incidence of summer shedding of rough hair coats.