The Horse Works - Horse Sense with Cathy Dee

A major problem in ridden horses and the leading cause, I believe of horse riding accidents and of horses being put down because of dangerous behaviour.

Rye Grass staggers

Rye Grass Staggers is becoming a major problem in NZ pasture since the rampant growth of the dairy industry caused rye grass to be planted everywhere, it is a neurological disease that can affect sheep, cattle, horses and ponies, deer and alpacas.
It occurs commonly throughout the North Island and as far south as North Ota go. It is prevalent in North Canterbury. It is most common in summer and autumn.

The disease is caused by the ingestion of a toxin produced by a fungus (or endophyte) in perennial ryegrass. The highest concentrations of toxin are in the leaf sheath and seed head

In horses, the most common sign is an increase in spooky behaviour. It is thought that the toxin causes the horse to hallucinate. This can become very dangerous as the horses reaction to the most mundane thing - such as a blade of grass moving, can be extreme.

What can you do?

Remove the horse from hazardous pasture if you can.
If safe pasture is not available, put the horse into yards and feed them non rye grass hay (or silage/baylage) and plenty of clean water.
The best long term solution in areas where the disease is a problem is to replace the affected ryegrass pasture with endophyte-resistant grasses.
I find a product called Feed Aid works very well and is reasonably priced.