Evaluation of Kentucky 31, G1-306, G1-307 and Kenhy Tall Fescue as Pasture for Yearling Steers II. Growth, Physiological Response and Plasma Constituents of Yearling Steers

Abstract

Performance, physiological responses and plasma constituents were studied in yearling cattle grazing four varieties (selections) of tall fescue (Festuca arundinacea Schreb). Varieties Gl-306 and Gl-307 have been selected for high and low perloline concentration, respectively. Average daily gains for the grazing period from March 24 to September 3 were .42, .38, .29 and .40 kg for steers grazing Kentucky 31, Gl-306 and Gl-307 and Kenhy, respectively. Gains of steers grazing Gl-307 were lower (P<.05) than those of steers grazing the other three varieties. Mean overall values across all sampling times for plasma Na, K, Mg, P or PUN were not different (P>.10) due to variety of tall fescue. However, plasma Na, Mg, P and PUN were different at specific sampling times due to variety. Steers grazing Gl-306 had a higher (P<.01) blood hematocrit than steers grazing the other three varieties. Steers grazing Gl-307 had higher (P<.01) respiration rates, which averaged 66, 63, 82 and 65 breaths/min for Kentucky 31, Gl-306, Gl-307 and Kenhy, respectively. In addition to higher respiration rates and lower ADG, steers grazing Gl-307 were emaciated and had long, rough, dull haircoats. The steers grazing Gl-307 spent most of the day under shades, while steers grazing the remaining varieties spent more time grazing and seemed less sensitive to heat stress. Copyright © 1979. American Society of Animal Science . Copyright 1979 by American Society of Animal Science.