Grazing and Finishing Performance of Steers that Grazed Nontoxic Endophyte-Infected Tall Fescue

Abstract

A total of 192 steers were used to evaluate grazing and subsequent finishing gains and forage availability from tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbyshire] pastures infected with nontoxic endophytes in 2004, 2005, and 2006. Cultivar-endophyte treatments evaluated were high-endophyte ‘Kentucky 31’ (HE31), low-endophyte Kentucky 31 (LE31), ‘HiMag’ infected with Strain 4 endophyte (HM4), and ‘Jesup’ infected with AR542 endophyte (‘MaxQ’). Pastures with LE31, HM4, or MaxQ produced higher (P < 0.05) steer grazing average daily gain (ADG), more (P < 0.05) gain per acre, and higher (P < 0.05) total BW gain per steer than HE31. Steer ADG, gain per acre, total BW gain per steer, and available forage were similar (P > 0.05) among pastures with LE31, HM4, or MaxQ. The HE31 had greater (P < 0.05) available forage than LE31, HM4, or MaxQ. USDA yield grade, marbling score, and percentage of carcasses grading choice were similar (P > 0.05) among fescue treatments. The toxic endophyte had a negative effect on performance of stocker steers grazing tall fescue pasture, but had no negative carryover effects on subsequent finishing performance other than steers that previously grazed these pastures had lower ending weight and yielded lighter carcasses.