Association of Epichloe Typhina Fungus and Steer Performance on Tall Fescue Pasture

Abstract
Anti‐quality components factors associated with poor animal performance on tall fescue (Festuca arundinacea Schreb.) pasture may include mycotoxins produced by the fungus Epichloe typhina (Pers.) Tul. The original objectives of this study were to compare steer performance on pastures of different grass species, but large differences in animal performance occurred among paddocks in different replications of the tall fescue‐dallisgrass (Paspalum dilatatum Poir.) treatment. The experiment was conducted in west central Alabama on replicated 1.2 ha paddocks containing two calcareous soils, Sumter clay (Rendolic Eutrochrept, fine silty, carbonatic, thermic) and Houston clay (Typic Chromudert, very fine montmorillonitic, thermic). The tall fescue‐dalligrass pastures were fertilized with 336 kg N/ha annually and grazed with yearling steers for 225 days annually for 3 years. The three tall fescue‐dallisgrass paddocks contained very little dallisgrass, but animal performance differed greatly on them. Steers averaged 453 kg gain/ha on two paddocks with an average daily gain (ADG) of 0.68 kg, while steers on the other paddock averaged only 360 kg gain/ha with an ADG of 0.45 over the 3‐year period. Dry matter digestibility of the forage averaged 63% for the high performance paddocks and 58% for the low performance paddock. Mineral content of the forage was similar on all paddocks. Tall fescue forage in the low performance paddock was heavily infested with Epichloe typhina fungus while the other two paddocks were lightly infested with the fungus. Results of the study suggest that this fungus may be associated with low performance of steers on tall fescue pasture.

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