Ergopeptine Alkaloids in Grazed Tall Fescue

Abstract

AbstractEndophyte (Acremonium coenophialum Morgan‐Jones et Gams) ‐infected tall fescue (Festuca arundinacea Schreb.) produces ergopeptine alkaloids (EP) that may be associated with fescue toxicosis symptoms in cattle (BOS taurus). A study was conducted during 1983 and 1984 at Watkinsville, GA, to determine the effects of endophyte infection, season, and N fertilization on EP concentration and steer average daily gain (ADG) in grazed 0.7‐ha tall fescue paddocks. Treatments included low (LF) and high (HF) endophyte infection frequency ‘Kentucky‐31’ (KY‐31) tall fescue fertilized with 134 or 336 kg N ha−1 (2✕2 factorial) replicated three times. The cultivars AU Triumph and Johnstone were also evaluated. Animals were managed using put‐and‐take grazing system. Ergopeptine alkaloid concentration (ergovaline was 80% of total) was greater in HF KY‐31 than LF KY‐31 in both years. Peak ergovaline concentrations occurred in spring and again in autumn (1984) when concentrations in HF KY‐31 approached 1 mk kg−1. Mid‐summer concentrations were about one‐third the autumn maximum for HF and LF KY‐31. Nitrogen fertilization had minimal effect on ergovaline concentration in the spring‐summer of 1983 but increased concentrations in LF KY‐31 in 1984. Ergopeptine alkaloids were not detected in endophyte‐free AU Triumph, and were detected in low amounts (< 0.1 mg kg−1) in a pre‐varietal release of Johnstone containing 7 to 10% endophyte. Increased ergovaline was associated with decreased ADG in the spring‐summer of 1983 and 1984; however, there was no significant association between ergovaline and ADG when the entire (April‐December) 1984 growing season was considered, suggesting that ergopeptine alkaloids may operate in conjunction with other environmental and nutritional factors to elicit fescue toxicosis symptoms.