Steer Consumption and Ergovaline Recovery from In Vitro Digested Residues of Tall Fescue Seedheads

Ergot alkaloids produced by the endophyte [Neotyphodium coenophialum (Morgan-Jones and Gams) Glenn, Bacon, and Hanlin] of tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] are a common problem faced by livestock producers. These toxins are concentrated within seedheads of tall fescue, which cattle were observed to selectively graze. There appears to be little research showing the extent to which alkaloids are released from developing seedheads during digestion. Therefore, the objectives of this study were to determine the amount at which tall fescue seedheads were removed by cattle and to estimate the amount of ergovaline that is released from these tissues. Seedheads from tall fescue pastures were monitored for consumption by steers during summer 2010. Samples were digested with a two-stage procedure, and ergovaline concentrations were determined using high-performance liquid chromatography. By mean stage count 3.91 (Day of Year 155), 60.7 +/- 2.87% of seedheads within the pastures had been grazed, and 2 wk later increased to nearly 78.8 +/- 0.82%. Ergovaline concentrations of seedheads increased throughout the season and were highest in mid-June. The percentage of ergovaline released from seedheads collected in mid-June was lower than earlier dates, but the difference was small. Results of this study indicate that high concentrations of ergovaline are released from tall fescue seedheads during the growing season, and management strategies should be aimed at controlling reproductive growth of the grass.