Summer Fescue Toxicity in Dairy Steers Fed Tall Fescue Seed

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Abstract
Seeds of the tall fescue (Festuca arundinacea Schreb.) cultivars Kentucky 31 and an experimental ryegrass ✕ tall fescue hybrid derivative strain (Gl-307), and orchard grass (OG) seed were fed in a carrier diet to calves in controlled environmental rooms (31 to 32 C). Both tall fescue varieties produced symptoms of summer toxicosis in dairy steers. Total feed intake (P<.01) and water intake (P<.01) of calves were reduced by the tall fescue seed diets when compared with orchard grass. Steers fed Gl-307 and Kentucky 31 tall fescue lost (NS) 17.5 and 7.8 kg of body weight, respectively, while those consuming orchard grass gained (P<.01) 6.2 kg during the experiment. Rectal temperatures were lower (P<.05) in the calves fed OG (39.4 C) when compared with those fed Gl-307 (40.6 C) and Kentucky 31 (40.8 C) tall fescue seed, respectively. In a second trial Kentucky 31 seed was fed in a carrier diet to Holstein steers at graded levels of 0, 350, 700 and 1,050 g seed/d. Consumption of 700 and 1,050 g seed/d adversely affected performance of steers. Total feed intake was lower and water intake was reduced (P<.05), with rectal temperatures being elevated (P<.01) in these two groups when compared with 0- or 350-g treatments. No significant differences were detected in body weight changes in this trial. Respiration rates were not significantly affected in either trial. Results of these trials with the young bovine indicate that a toxic substance(s) is present in tall fescue seed. Copyright © 1984. American Society of Animal Science . Copyright 1984 by American Society of Animal Science.

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