Fungus causing gangrene spotted
Farmers in the south are being warned to look out for a toxic fungus while preparing baleage.
VetSouth Winton veterinarian and director Mark Bryan said there had been reports of farmers finding ergot in their pastures as they were preparing to mow baleage for winter feed. ‘‘It’s never been as bad a season as it is now,’’ Bryan said. Ergot thrives after a dry summer and wet autumn. Last year more than 100 cows in Southland and South Otago had to be put down after ergot poisoning.
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. Cattle tend to eat more seed heads than sheep and have a higher risk of poisoning. 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. Bryan said a lot of farmers had been asking about the fungus after finding it in their paddocks. If farmers found it in a paddock they could not feed it out as it was highly toxic, he said. Ergotism cuts off the supply of blood to the extremities.
Ergot spores are spread by the wind and there is no reliable test for the spores in stock feed. In silage it is difficult to determine whether ergot is through the entire stack. By the time the fungus was spotted last year, it had already been fed out to cattle in silage and baleage. Bryan hoped this year farmers would be on the lookout ahead of harvesting. ‘‘I’m very impressed with how vigilant the farmers have been.’’
While ergot may be present in some paddocks on properties, it may not be throughout the entire farm. Bryan wanted to reassure farmers that some of their paddocks could still be fine for mowing into baleage. Ryegrass infected with ergot can be identified by the presence of ergot bodies – long purple to black structures in place where seeds should be. .
Stock can handle a certain amount of ergot. However, under the Agricultural Compounds and Veterinary Medicines Act, this feed is not fit-for-purpose and should not be fed to them. 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. Another management option is to mow the paddock and let the seed heads rot into the soil where they are unable to be eaten.