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horses ryegrass staggersWhat is it?
  • A neurological disease of sheep, cattle, horses and ponies, deer and alpacas.
  • Alpacas appear to be particularly susceptible.
When and where does it occur?
  • It occurs commonly throughout the North Island and as far south as North Otago.
  • It is most common in summer and autumn.
What is the cause?

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.

The toxin has a specific damaging effect on the cells in the cerebellum of the brain that coordinate movement.

What are the signs?
  • The signs are most obvious when affected animals are disturbed and forced to move.
  • Affected animals become anxious about being approached.
  • In mild cases there is slight trembling of the head and of the skin of the neck, shoulder and flank.
  • More severe cases show head nodding and jerky movements, swaying while standing and staggering during movement.
  • In the most severe cases, they have a stiff legged gait, short prancing steps, and may collapse with rigid spasms that last for up to several minutes.
What happens to affected animals?
  • The disease itself is not fatal, but there is a real risk of injury or death as a result of accidents.
  • Affected animals lose weight as they don’t graze as much.
  • They may not be able to drink sufficient water.
  • They can become caught up in obstacles like electric fences.
  • They can fall into holes and ditches, and over bluffs.
  • They can drown in creeks, dams, drains and swamps.
  • Affected dairy cows produce less milk and become distressed when herded. Severely affected cows may fall over in the bail.
  • Horses and ponies become more difficult to handle, and even dangerous to ride.
What can you do?
  • Remove stock from hazardous pasture if you can.
  • If safe pasture is not available, put the stock into yards and feed them hay (or silage/baylage) and plenty of clean water.
  • Handle affected stock quietly.
  • Don’t disturb affected animals unnecessarily.
  • The best long term solution in areas where the disease is a problem is to replace the affected ryegrass pasture with endophyte-resistant grasses.
  • If you are have problems with ryegrass staggers, contact your veterinarian.
Commercial products available
  • A mixture of magnesium sulphate and sodium chloride has been found to be effective by VE Vets in Te Awamutu who have made up the mixture to treat affected stock. Phone (07) 871-3091
  • Mycosorb® by Alltech can used to control this issue in many animals including horses, cattle (dairy and beef), deer, sheep and alpacas.
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