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Ryegrass Staggers in Horses – Causes, Symptoms & Management

Ryegrass Staggers in Horses – Causes, Symptoms & Management

What Is Ryegrass Staggers? 

 Ryegrass staggers is a neurological condition in horses caused by mycotoxins, specifically lolitrem B, produced by an endophyte fungus that lives within perennial ryegrass. This fungal toxin affects the cerebellum, the part of the brain that controls balance and muscle coordination. As a result, horses may show signs of trembling, unsteady gait, and difficulty standing or walking, hence the term "staggers." 

 Although commonly seen in horses due to their hindgut fermentation, ryegrass staggers can also affect cattle, sheep, alpacas, and deer. It's important to note that this condition is not related to magnesium deficiency, although the clinical signs can appear similar. Also, annual ryegrass toxicity is a different disorder involving bacteria and nematodes. 

 Why Are Endophytes in Ryegrass?

 Endophytes are fungi that live within certain grasses like ryegrass and help the plant resist pests, grow vigorously, and thrive under stress. Pasture grasses containing endophytes often offer better drought resistance, higher yields, and improved persistence, but unfortunately, some endophyte strains produce harmful mycotoxins that cause staggers. 

 There are several types of ryegrass to be aware of: 

  •  Standard endophyte ryegrass: Offers strong insect resistance but produces harmful mycotoxins. 
  •  AR1 endophyte ryegrass: Reduces the risk of staggers but is less resistant to pests like black beetle. 
  •  AR6 endophyte ryegrass: Offers both reduced risk of staggers and better insect resistance

 Choosing the right type of pasture grass is essential for both pasture resilience and animal safety. Consult with a local seed supplier for advice on the best pasture mix for your region. 

 Clinical Signs of Ryegrass Staggers in Horses 

 Symptoms can range from mild to severe and may include: 

  •  Muscle trembling (especially in the neck and shoulders) 
  •  Loss of coordination or staggering gait 
  •  Difficulty eating or drinking 
  •  Collapse or falling in serious cases 
  •  Behavioural changes like anxiety or agitation 

 In mild cases, only subtle tremors or nervous behaviour may be noted. Always consult your veterinarian to distinguish ryegrass staggers from conditions like magnesium deficiency, which presents with similar signs. With prompt removal from contaminated pasture and proper nursing care, most horses recover fully within 1 to 2 weeks. 

 How to Reduce the Risk of Ryegrass Staggers 

 While ryegrass staggers is a seasonal issue, often peaking in late summer and autumn, it can be managed with careful planning: 

  •  Identify high-risk horses: Young horses, pregnant or lactating mares have higher nutritional needs and are more likely to ingest larger amounts of pasture and therefore more toxins. 
  •  Practice rotational grazing: Avoid overgrazing, as endophytes concentrate in the base of the grass and seed heads. 
  •  Avoid seed head grazing: Endophyte concentration is highest in the seed heads, especially during dry periods. 
  •  Use older ryegrass seed: Endophyte viability declines significantly in seed that’s over two years old. 
  •  Check stored forage: Mycotoxins can persist in silage for over 200 days but tend to decrease in hay over time. Avoid visibly mouldy hay and be cautious with haylage or baleage. 
  •  Watch for mushrooms and fungi: These can indicate ideal fungal conditions in the pasture and may correlate with higher endophyte activity. 
  •  Explore alternative forage options: Incorporating species like cocksfoot and phalaris may reduce reliance on ryegrass. 

Toxin Binders 

  •  Use toxin binders: Some feed additives can bind mycotoxins in the digestive tract, reducing absorption. 
  • Organic and clay-based options are available, but clay products should be used cautiously as they may interfere with nutrient uptake.  
  • Multipurpose toxin binders such a Toxfree Toxin Binder  effectcily bind polar and non polar mycotoxins.

Conclusion

 Ryegrass staggers in horses is a serious but manageable condition. Recognising the early signs, choosing the right pasture species, and managing grazing practices can dramatically reduce the risk. With appropriate veterinary care and supportive management using toxin binders, affected horses usually recover well. 

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