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

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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.

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