Co-exposure of the Mycotoxins Lolitrem B and Ergovaline in Steers Fed Perennial Ryegrass ( Lolium perenne) Straw: Metabolic Characterization of Excreta.

Past research showed a strong linear correlation between levels of the mycotoxins lolitrem B (LB, a tremorgen) and ergovaline (EV, an ergot alkaloid and potent vasoconstrictor) in perennial ryegrass (PRG) forage. The purpose of this study was to characterize the excretion of these two compounds in beef cattle consuming PRG straw and to utilize liquid chromatography-tandem mass spectrometry to investigate the metabolism of LB and EV in excreta. Four groups of steers ( n = 6/group) were fed endophyte-infected PRG for 64 days (2256/638, 1554/373, 1012/259, or 247/<100 μg/kg LB/EV). Concentrations of LB and EV in both PRG straw and feces showed a linear relationship to each other. Feces reflected a dose-response for both mycotoxins, with values increasing most rapidly through 21 days then plateauing. Urine contained no detectable level of either compound or the ergoline lysergic acid. Screening for metabolites showed oxidation and reduction biotransformations for both toxins, with additional conjugation products detected for ergovaline.