Biomarkers of exposure to cyanogens in horses with grass sickness.

The study investigates if equine grass sickness (a fatal disease affecting horses’ digestive system) is linked to the ingestion of cyanogenic glycosides (toxins found in many plants) from white clover. The researchers measured the concentration of cyanide and thiocyanate (byproducts of cyanide metabolism) in the blood and urine of horses with grass sickness and healthy control horses. Results suggest that horses with grass sickness may have been exposed to increased levels of these toxins before they fell ill.

Methodology and Participants

• The study involved a selection of horses suffering from acute and subacute variants of equine grass sickness. In total, 12 horses with acute grass sickness and 10 with subacute grass sickness were included.
• Additionally, 43 horses were kept as controls. Among the controls, 21 were co-grazing with cases of acute grass sickness while 12 grazed pastures where grass sickness had not been reported and 10 were stabled horses.

Measurements Taken

• The study conducted measurements on the concentrations of whole blood cyanide and plasma and urinary thiocyanate. These are indicators of exposure to cyanogens, compounds that release cyanide.
• The collection of these measurements was aimed to test the hypothesis that equine grass sickness may be associated with the ingestion of cyanogenic glycosides from white clover.

Results of the Study

• Findings suggested that healthy horses that grazed with cases of acute grass sickness had higher levels of blood cyanide, and plasma and urinary thiocyanate than the other control horses. This implies a heightened exposure to cyanogens.
• Horses suffering from grass sickness displayed no evidence of a recent cyanogen intake. It is hypothesized that these horses might have been exposed to increased cyanogen levels before they exhibited a loss of appetite – a symptom of grass sickness.

Conclusion and Implications

• This study indicates a potential link between ingestion of cyanogenic glycosides from white clover and the onset of grass sickness in horses.
• However, it is suggested that further research is needed to conclusively establish this link and elucidate the extent to which grass sickness may be preventable or mitigated through dietary control.