Perennial ryegrass staggers is poisoning by peramine, lolitrem B, and other toxins that are contained in

perennial ryegrass ''Lolium perenne'', common name perennial ryegrass, English ryegrass, winter ryegrass, or ray grass, is a Poaceae, grass from the family Poaceae. It is native to Europe, Asia and northern Africa, but is widely cultivated and naturalised around th ...

(''Lolium perenne''), and produced by the

endophyte An endophyte is an endosymbiont, often a bacterium or fungus, that lives within a plant for at least part of its life cycle without causing apparent disease. Endophytes are ubiquitous and have been found in all species of plants studied to date; ...

fungus ''

Epichloë festucae ''Epichloë'' is a genus of ascomycete fungi forming an endophytic symbiosis with grasses. Grass choke disease is a symptom in grasses induced by some ''Epichloë'' species, which form spore-bearing mats (stromata) on tillers and suppress the de ...

'' which can be present in all parts of the grass plant, but tends to be concentrated in the lower part of the leaf sheaths, the flower stalks and seeds. This condition can affect

horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 mi ...

cattle Cattle (''Bos taurus'') are large, domesticated, bovid ungulates widely kept as livestock. They are prominent modern members of the subfamily Bovinae and the most widespread species of the genus '' Bos''. Mature female cattle are calle ...

sheep Sheep (: sheep) or domestic sheep (''Ovis aries'') are a domesticated, ruminant mammal typically kept as livestock. Although the term ''sheep'' can apply to other species in the genus '' Ovis'', in everyday usage it almost always refers to d ...

, farmed deer and

llama The llama (; or ) (''Lama glama'') is a domesticated South American camelid, widely used as a List of meat animals, meat and pack animal by Inca empire, Andean cultures since the pre-Columbian era. Llamas are social animals and live with ...

s. It regularly occurs in New Zealand and is known spasmodically from Australia, North and South America, and Europe.

Ecology

Perennial ryegrass staggers is caused by the ingestion of grass that is infected by the

fungus ''Epichloë festucae'' var ''lolli'', and this fungus produces a variety of toxins such as peramine, a pyrrolopyrazine alkaloid, and lolitrem B, an

indole Indole is an organic compound with the formula . Indole is classified as an aromatic heterocycle. It has a bicyclic structure, consisting of a six-membered benzene ring fused to a five-membered pyrrole ring. Indoles are derivatives of indole ...

diterpene Diterpenes are a class of terpenes composed of four isoprene units, often with the molecular formula C20H32. They are biosynthesized by plants, animals and fungi via the HMG-CoA reductase pathway, with geranylgeranyl pyrophosphate being a primary ...

compound. There is no external sign when perennial ryegrass is infected by this fungus. The Argentine stem weevil (''Listronotus bonariensis'') feeds on perennial ryegrass. When the grass on which they are feeding is infected by the fungus, the larvae of the weevil fail to develop fully. In an effort to breed perennial ryegrass that was resistant to the weevil, researchers in New Zealand inadvertently selected strains that were susceptible to the fungus. In fact the endophytic fungus forms a mutualistic association with the grass which grows more vigorously as a result and produces more tillers. With greater use of these susceptible cultivars, the fungus which is present in the seed, spread more widely with a consequent increase in perennial ryegrass staggers.

Symptoms

Symptoms are neurological and may develop one to two weeks after exposure to infected pasture. Symptoms may include head shaking and irregular eye movements, changes in gait, stiffness, staggering and falling. Recumbent animals may display tetanic spasms and may die through misadventure, dehydration, starvation, loss of

rumen The rumen, also known as a paunch, is the largest stomach compartment in ruminants. The rumen and the reticulum make up the reticulorumen in ruminant animals. The diverse microbial communities in the rumen allows it to serve as the primary si ...

function or predation. In the case of horses, the animal may quiver or tremble, be easily startled and be awkward to handle. More severely affected animals may repeatedly nod their head, show a tendency to splay their legs, and stumble and fall. The hind-quarters, moreover, may become paralysed.

Treatment

Recovery usually occurs when the animal is removed from the contaminated pasture. The chief danger to stock at this stage is caused by their lack of coordination, which may result in accidental death by falling in awkward places such as ditches and ponds.

Prevention

The disease is particularly prevalent in New Zealand. It may be prevented by avoiding grazing pastures containing perennial ryegrass, or seeding pastures with resistant strains of ryegrass. Horses are particularly prone to this disease because of their habit of biting close to the ground, and sparse pastures may encourage heavier grazing with greater intake of infected material. Supplementary feeding may help, but

hay Hay is grass, legumes, or other herbaceous plants that have been cut and dried to be stored for use as animal fodder, either for large grazing animals raised as livestock, such as cattle, horses, goats, and sheep, or for smaller domesticate ...

from infected pasture should not be used because it may contain further toxins.

References

{{reflist, 30em Animal fungal diseases Bovine diseases Animal welfare and rights in New Zealand