Ergopeptine Alkaloids in Grazed Tall Fescue

Endophyte (Acremonium cotnophiaJum Morgan-Jones et Gams) -Infected tall fescue (Festuca arundinacea Schreb.) produces ergopeptiDe alkaloids (EP) that may be associated with fescue toxicosis symptoms in cattle (B03 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 O.7-ha tall fescue paddocks. Treatments included iow (LF) and high (HF) endophyte infectioo frequency lKentucky-31' (KY·31) tall fescue fertilized with 134 or 336 kg N ha I (2x2 factorial) replicated three times. The cuJtivars 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-I. Mid·summer concentrations were about one-third the autumn maximum Cor 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 I) 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; howel'er, there was no sig. nificant 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.