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

The research article is about an exploration into equine dysautonomia, a disease in horses, and its relation to changes in plasma amino acid levels, focusing particularly on sulfur-containing amino acids.

Study Introduction

• The study was designed to investigate whether equine dysautonomia (ED), also known as grass sickness, is associated with changes in the metabolism of plasma amino acids in horses.
• This disease, which usually affects young horses, results in severe damage to the neurons in the horse’s nervous system controlling digestive functions.

Methods and Participants

• Plasma amino acid profiles were taken from horses diagnosed with acute ED (10 horses), subacute ED (6 horses), and chronic ED (7 horses). Healthy horses co-grazing with the affected ones (6 horses) and control horses (10 horses) were also studied for comparison.

Findings

• The research found that horses with acute ED showed significant changes in their plasma amino acid profiles. Those changes resembled signs of severe protein malnutrition.
• Horses with ED and their healthy counterparts grazing on the same fields showed a depletion in certain sulphur-containing amino acids – specifically cy(e)ine and methionine.

Implications and Future Research

• This research indicates that there are similarities in the plasma amino acid changes seen in horses with ED and those seen in subacute/chronic cyanide toxicity. This similarity suggests that cyanogenic glycosides, which release cyanide when metabolized, may play a role in triggering ED.
• However, the amino acid analysis for detection of ED contains limitations, as no definitive premortem diagnostic test for ED was discovered. This is attributed to the overlapping individual amino acid levels among the control group, co-grazing, and ED horses.
• Thus, this study brings new insights but also asks for further exploration into the etiology of ED and the potential role of cyanogenic glycosides in it.