Grazing and Subsequent Feedlot Performance by Steers That Grazed Different Types of Fescue Pasture

Toxicity symptoms manifested by cattle grazing tall fescue (Festuca arundinacea Schreb.) infected with the endophytic fungus Acremonium coenophialum are well documented. However, subsequent feedlot performance by these cattle has been variable. This study was conducted to compared grazing and subsequent feedlot performance of steers that grazed N‐fertilized, A. coenophialum‐infected ‘Kentucky 31’ tall fescue (IF); IF interseeded with ladino clover (Trifolium repens L.; IFL); or endophyte‐free ‘Missouri 96’ tall fescue (MO). Grazing experiments were conducted from 1986 to 1988 and followed by a dry lot phase with the cattle offered high‐concentrate rations for 124 to 134 d. Significant (P < 0.05) year effects and interactions were detected for weight and gain parameters and carcass quality grade. A pasture type × phase (grazing vs. feedlot) interaction also was observed for daily gain in 1986 (P = 0.07), 1987 (P < 0.05), and 1988 (P < 0.05). Cattle grazing IF had lower pasture daily gain than those grazing IFL in 1987 (P < 0.01) and MO in 1988 (P < 0.05), but higher feedlot daily gain from than from MO in 1986 (P < 0.10) and IFL in 1987 (P < 0.05). Feed‐to‐gain ratios from cattle previously grazing IF were lower (P < 0.05) than those from cattle previously grazing IFL and MO. Cattle that previously grazed IFL had greater (P < 0.01) fat thickness and USDA yield grades. Those cattle also had higher (P < 0.05) USDA quality grades than cattle that previously grazed IF and MO in 1986 and IF in 1988. Therefore, while steer performance was reduced while grazing A. coenophialum‐infected fescue compared with those grazing low‐endophyte fescue or infected fescue interseeded with ladino clover, those steers apparently recovered from the endophyte effects such that feedlot gain and feed efficiency were enhanced.