with Phil Rennie
Both rye grass and paspalum plants can cause similar neurological conditions – commonly referred to as staggers.
As opposed to ‘grass staggers’ which relates to low magnesium in livestock soon after birth, these two fungal-neurotoxin-induced diseases can cause generalised tremors in all ages of cattle, sheep, deer, alpacas and horses.
Ryegrass staggers occurs when animals grazing perennial ryegrass eat large amounts of a toxin, lolitrem B, produced by ryegrass endophyte, a fungus that grows inside the plant. This endophyte also produces another toxin that protects the plant from destruction by insects, in particular the Argentine stem weevil.
Toxicity is increased as the animals graze lower, if they are forced to eat short grass they are more at risk of ryegrass staggers.
Paspalum staggers occurs when animals eat seed heads of paspalum that have been infected with an ergot fungus. These can be seen as dark masses that are larger than the normal seeds.
The clinical signs of these poisonings are similar and are usually seen when animals are disturbed and forced to move. The initial symptoms are subtle head tremors and skin twitching. These can become more pronounced as head nodding, swaying, with a staggering motion that can become a stiff-legged, jerky walk and eventually collapse.
Deaths tend to be accidental following injury such as drowning after a fall into water or being caught in fences.
Recognising affected animals and taking preventative steps against ryegrass and paspalum staggers is important to prevent accidental injuries. In addition, affected animals can show reduced production such as poor growth rates and reduced milk production.
Both of these diseases are usually seen late-summer to early-autumn, in different types of paddocks. In contrast ‘grass staggers’ – due to a lack of magnesium – is mainly seen in winter and spring in older cows and sheep.
The key to treatment of both these diseases is to slowly and quietly remove the animals from the affected pasture and to provide supplementary feed such as hay, silage or nuts. Anecdotally treatments such as Nutrimol and Summer Tonic can be given to help affected animals. If removed from the toxic pasture and left quietly for a while, the animals will usually fully recover.
Prevention is essentially stopping animals from getting access to affected pastures. Avoiding hard grazing of ryegrass, topping paspalum before the fungus can grow on the seeds.
Longer term management would include resowing pastures using ‘safe’ endophyte grass strains, like AR37, which have an endophyte that kills weevil but does not produce the staggers toxin.
While common at this time of year, these neuro diseases are not the only reasons for animals to stagger. If you suspect your animals may be suffering from one of these diseases or something else, please contact your local vet clinic for advice.