Ryegrass Staggers

Ryegrass staggers can be prevented but it’s not easy on hill country farms.

Symptoms of the Disease/Condition

A nervous disease in sheep, cattle, horses & deer.

Animals are affected after grazing pastures (usually ryegrass dominant pastures under close grazing conditions) that contain a fungus which produces a toxin.

This condition should not be confused with “grass staggers” which is a nervous disease caused by a metabolic imbalance of magnesium.

Ryegrass staggers is part of the endophyte story. Endophyte is a fungus which is found in the leaf, sheath , stem and seed of perennial ryegrass. The fungus produces several toxins, one being lolitrem B which is the major toxin associated with ryegrass staggers. However these toxins are important for plant survival, for example one of the toxins (peramine) protects the ryegrass against argentine stem weevil.

In terms of grass production, endophyte infected ryegrass has pasture production advantages over endophyte free ryegrass. In animal friendly terms, endophyte free ryegrass will not cause ryegrass staggers.

There has been a vast amount of research to create cultivars of ryegrass that are infected with endophyte fungus which produces low levels of lolitrem B (so a low risk for ryegrass staggers in animals) while still producing high levels of peramine for protection against Argentine stem weevil. See photo comparing pasture growth of AR1endophyte ryegrass to the new novel AR37 endophyte which is low risk for ryegrass staggers in animals.

hoggetts web vet sheep iStock 91540695 Web
vet sheep
VetEnt disease landing page 9

Cost/Impact on Herd/Farm Revenue

The toxin affects nerves and muscles so when the animal moves it “staggers”. If they get a sudden fright they may fall over. Affected animals appear normal and will continue to graze until stimulated.

The condition tends to be more common during summer & autumn.

Animals develop signs within 7-14 days of being placed on toxic pastures.

Growth rate of weaned grazing calves may be reduced and in some cases they may lose weight for a while because of the effect on the calves ability to graze and compete for food effectively.

In severe seasons with many animals affected, stock losses may result from misadventure eg drowning in dams, caught in natural hazards such as gullies, ditches and fences.

Affected animals may be difficult to yard for routine procedures such as vaccinations and worm treatments.

Diagnosis is based on clinical signs – a normal looking animal that staggers and/or falls over after getting a fright.

VetEnt disease landing page 11

Management and control

There is no treatment for affected animals but they will recover in a few weeks depending on how long they continue to eat the infected pasture. Recovery will be faster if animals can be shifted to pastures that do not contain ryegrass.

Whenever possible shift the all the animals into paddocks where there is no risk of falling down banks or into water drains.

Ryegrass staggers can be prevented but it’s not easy on hill country farms.

Contact your nearest VetEnt clinic to learn more about how to manage ryegrass staggers in your animals.

VetEnt disease landing page 6

About VetEnt Group

Enjoy local service backed by nationwide support from NZ's largest vet group with over 75 vets nationwide, giving you more depth of expertise from shared knowledge and technical expertise.

Meet your local vet

Meet the team

Search For


I highly recommend VetEnt. They have been there with me for the past 5 years as my business has grown.  They are both proactive and leaders in their field. They are reliable and always go beyond the call of duty with their service

Make an Appointment

For urgent appointments within the next 24 hours, please phone the clinic directly.