Equine dysautonomia (grass sickness) is associated with altered plasma amino acid levels and depletion of plasma sulphur amino acids

To determine whether equine dysautonomia (ED) is associated with alteration s in plasma amino acid metabolism, plasma amino acid profiles were determin ed for horses with acute (n = 10), subacute (n = 6) and chronic (n = 7) ED and for healthy cograzing horses (n = 6) and control horses (,n = 10). Hors es with acute ED had perturbations in plasma amino acid profiles resembling those of severe protein malnutrition. In addition, horses with ED and cogr azing healthy horses had depletion of the plasma sulphur amino acids cyst(e )ine and methionine. As similar plasma amino acid perturbations occur in su bacute/chronic cyanide toxicity, the role of cyanogenic glycosides in the a etiology of ED warrants further study. Unfortunately, amino acid analysis c annot be used as a definitive premortem diagnostic test for ED, since there was overlap in the individual amino acid levels of control, cograzing and ED horses.