Treatment of clinical signs of perennial ryegrass toxicosis in sheep

Summary

Perennial Rye Grass Toxicosis (PRGT) causes significant mortalities in sheep during severe outbreaks and subclinical losses estimated to be in the region of 63M p/a.  PRGT is caused by ingestion of a mixture of toxins present in Neotyphodium lolii infested perennial rye grass. The movement disorder 'Rye Grass Staggers' is the key clinical sign identifying high levels of the toxin lolitrem B being present in the pasture, a tremorgenic compound that causes the neurological signs, reaches levels sufficient to cause neurological effects. Alleviating the effects of PRGT in grazing livestock is of significant interest to producers and their economic partners alike; a therapeutic intervention effective in the most severe recumbent cases will increase survivability for animals during severe PRGT outbreaks. To identify a potential therapeutic agent a controlled clinical trial was undertaken in which clinical signs of 'Rye Grass Staggers' was induced in male lambs which were then treated with the anti-epileptic drug potassium bromide using one of two modalities. Animals receiving a single dose of potassium bromide showed significant improvement in their ability to maintain normal movement. Animals receiving a prophylactic dose over 22 days also showed improved mobility. This work suggests potassium bromide to be an effective treatment for Rye Grass Staggers, but more work is needed to confirm the correct application for prophylaxis.