Annual ryegrass toxicity risk for livestock

The Department of Agriculture and Food says annual ryegrass toxicity can occur at any time of the year if animals are fed hay containing affected seed heads. Picture: DAFWA

HORSE and other livestock owners are being advised to be aware of the risk of annual ryegrass toxicity following recent horse and cattle deaths linked to the consumption of affected hay.
Department of Agriculture and Food veterinary officer Anna Erickson said annual ryegrass toxicity was a serious and usually fatal disease that occurred when livestock ate annual ryegrass seed heads infected with a toxin-producing bacterium.
“Annual ryegrass is present in much of the oaten and meadow hay grown and sold for animal consumption in Western Australia,” she said.
“Although annual ryegrass toxicity occurs mainly in spring when stock graze pasture containing infected ryegrass seed heads, outbreaks can occur any time of the year from feeding hay that contains seed heads affected by annual ryegrass toxicity.”
Dr Erickson said the toxin was cumulative and signs did not appear until a near-fatal dose was ingested.
“The time taken for the animal to show signs of illness depends on the amount of hay or pasture being consumed and the amount of toxin present in the seed heads,” she said.
“Signs include weakness, muscle tremors, loss of coordination, staggering, convulsions and eventual death. The toxin also reduces appetite which can lead to colic or fatty liver syndrome in ponies. Occasionally animals may die before signs are noticed.
“There is no specific antidote to annual ryegrass toxicity, but some affected animals will recover with supportive care.
“Animals are sensitive to external stimuli so should be kept in a quiet area with easy access to feed and water, and handled as little as possible.
“The department recommends that all stock owners and feed sellers ensure hay containing annual ryegrass is tested for the presence of the bacterium that causes annual ryegrass toxicity, and testing has found the hay to be low risk – visual tests are not reliable.”
Dr Erickson said it was important to note that while feed testing reduced the risk of annual ryegrass toxicity poisoning, it did not eliminate it as annual ryegrass toxicity could be present in other untested parts of the bales.
“Requesting a vendor declaration from the hay supplier is a formal way of receiving a declaration about the feed quality and any testing conducted,” she said.
“Horse owners can obtain fodder vendor declarations from the Australian Fodder Industry Association website while red meat producers can access commodity vendor declarations through Meat and Livestock Australia’s Livestock Production Assurance e-DEC program.
“Landholders should also be aware that bringing infected hay onto their properties may infect their own pastures.”
Stock owners concerned about the safety of the hay already on the property can organise to have hay tested for annual ryegrass toxicity risk by the department’s diagnostic laboratory services .
Testing requires a 1kg hay sample to be submitted to the laboratory service at the department’s South Perth office or to any regional office.
Dr Erickson said the signs of annual ryegrass toxicity were similar to some reportable diseases not present in Australia.
“For this reason, we are always keen to have a private or department vet take samples to submit for laboratory testing from livestock with these signs.
“These reportable diseases can be ruled out with correct testing.
“Data from this testing helps to protect public health and our valuable livestock export markets, as trading partners ask us to provide proof that Australia is free of these diseases.”