More than 100 cows euthanised after ergot poisoning in Southland and Otago
Southland and Otago farmers have just put down more than 100 dairy cows suffering from ergot toxicity.
Ergot is a naturally occurring fungus which can infect grains and grasses, and after entering the blood of humans or animals leads to gangrene and death.
VetSouth Winton veterinarian Hayden Dore said four cases of ergot toxicity had been reported in Southland and South Otago, with large numbers of cows affected.
A 900-cow herd had between 120 and 140 cows infected by the poisonous fungus and 61 of them had to be put out of their misery by farmers. Another herd of 400 cows had 56 affected, and 41 of them were euthanised, he said.
The fungus, which produces potent alkaloids poisonous to animals, has been around for thousands of years and affects native and ryegrasses, as well as cereal grains. Ergot toxicity occurs sporadically in New Zealand when environmental conditions are right.
Dore said a dry summer and wet autumn contributed to the appearance of the fungus in the region, with many of the cases he had seen affecting the hind limbs of cows.
Ergotism cuts off the supply of blood to the extremities.
"Over time it effectively causes one or more of the limbs to become gangrenous," Dore said.
Signs of ergot toxicity generally started with a disinterest in feed, before moving to lameness in the limbs, which presented similarly to footrot, but without the separation of the toes, he said.
It took about 10 days for one of the farmers to spot the lameness in his cows, he said.
Once the limbs go cold from lack of blood supply, it would take about a week before the limbs began to fall off, he said.
"It's a serious animal welfare issue."
While some cows were able to recover fully, Dore drew the line with animals which had cold limbs because they could not recover.
Ergot spores are spread by the wind and there is no reliable test for the spores in feed.
Ryegrass infected with ergot can be identified by the presence of ergot bodies – long purple to black structures in place where seeds should be. The ergot bodies contain concentrated ergot alkaloids, which can be toxic to animals.
Dore said it could take as little as three ergots to kill a cow.
Under the Agricultural Compounds and Veterinary Medicines Act, this feed is not fit-for-purpose and should not be fed to animals. Furthermore, responsibilities under the Animal Welfare Act and the Animal Products Act include preventing access to the feed, providing veterinary treatment, and not transporting affected animals.
Feed should be disposed of by burying it deeper than four centimetres. Burying the ergot suppresses the spores and prevents them from spreading.
Farmers and veterinarians should report suspected cases of ergotism to MPI at ACVM-AdverseEvents@mpi.govt.nz.