November 19, 2004
From: ABC [edited] <http://www.abc.net.au/rural/news/stories/s1245507.htm>

Ryegrass toxicity fears in South Australia

Livestock producers in South Australia fear a burst of hot weather will worsen outbreaks of ryegrass toxicity, which can kill sheep, cattle and horses.

The DPI [Department of Primary Industries] says there have been up to 16 cases of stock deaths on the Yorke and Eyre Peninsulas, including 100 sheep on one property, and 40 cattle on another.

Livestock advisor Brian Ashton says farmers need to keep a close eye on their stock, especially with today's forecast for 40 degree C temperatures.

"It's a toxin that affects the nervous system of the animal ... so that any stress on the animal will make it worse.  In fact if you go out to a mob and you're not stirring them up they just look quite normal.  But when you make them run, and you stress them a little bit; then that's when you see them falling over, trying to "climb stairs" and all the classic signs."

[The type of cultivar of ryegrass allows for mycotoxins to be produced by the endophyte which infects the plant. _Acremonium loliae_ is the fungus  that infects perennial ryegrass. The endophyte [in Australia]  affects the leaf, stem, and the seed head. In contrast, the endophyte in the US affects [only] the seed head.

Managment to prevent the disease includes planting cultivars that are not susceptible to the mycotoxins, and moving animals such that plants are not grazed closely to the ground. This type of grazing may still present
some cases, but grazing the grasses close to the ground seems to increase the incidence. Pastures that are older than 2 years old from planting may have less difficulty. The mycotoxin is generally short-lived, about 18-24 months in most cases.

Generally in Australia, ryegrass staggers  is a neurological disease affecting sheep and cattle. Clinical signs usually develop approximately a week  or 2 after animals begin grazing infected pastures.

Ryegrass staggers in Austraila has been documented to affect sheep, cattle and horses. Deer are thought to be succeptible but goats have not been reported as being susceptible.

Clinical signs in affected sheep may include trembling, staggering, swaying when prompted to move. These animals may be easily excited, and demostrate a stiff, tilted gait with muscle twitching and even convulsions.  Cattle may present with a trunk stiffness leading to difficulty in walking. They may be seen in unusual positions, such as kneeling with the   front legs but not the back legs, or sitting, much like a dog sits. When cattle collapse, they do so with legs in a flexed positions, where as other diseases produce rigidly extended legs.  Horses stand with splayed legs & are easily excited by noise or movement.  They are hypersensitive to most stimuli. They move slowly, in a drunken fashion, and fall easily. Horses [may] also develop a paralysis of the hindquarters.

If pastures contain a high proportion of non-infected plants, and animals are not severely affected, & may recover, [but] if the pastures are predominately affected by the endophyte and the animals are not removed from the pastures, then permenant neurological damage may occur. [Apart from] pasture mangement, treatment is symptomatic and may be unrewarding as the neurological damage may be permanent.- Mod.TG]