Many potential mycotoxins can impact cattle feeds.
“We have many different geographic origins for cattle feeds and maybe 10 to 20 different mycotoxins potentially present,” said Trevor Smith, adjunct professor of animal biosciences, University of Guelph, Guelph, Ontario. “And there’s the potential for additive or synergistic responses.”
Extreme weather patterns could increase the frequency of mycotoxin challenges in livestock, Smith said during a presentation at the Driftless Region Beef Conference organized by the University of Illinois Extension, Iowa State University Extension and Outreach, University of Minnesota Extension and University of Wisconsin Extension.
“Excess moisture is a key factor in promoting mold growth that could lead to mycotoxin production,” Smith said. “Dehydration is one of the best tools we have to minimize the potential for mycotoxin contamination of feedstuffs.”
Drought conditions also may increase mycotoxin contamination of feeds.
“Drought stress will cause cracking and shriveling of corn kernels, which will break down the waxy outer coat and allow fungal spores to invade and produce mycotoxins,” Smith said.
The Silent Killer
Aflatoxin is produced by Aspergillus flavus, which is a tropical fungi that prefers high humidity and temperature conditions.
“It affects the liver of animals and causes liver cancer,” Smith said. “We don’t find it in Canada, except in imported feedstuffs.”
“Fusarium is produced in temperate climates of most of the U.S. and all of Canada,” he said. “Fusarium is really the challenge because there are several hundred different chemical structures, which are very difficult to analyze.”
Horses, dogs and cats are the most sensitive species for fusarium mycotoxins, Smith said.
“As little as 3 parts per million of fumonisin can be fatal to horses,” he said. “For pigs, there can be lesions on the lungs, and that takes 40 parts per million.”
“With poultry, they seem to be doing fine, and then we start to see the loss of immunity and then damage to the digestive tract,” he said. “Levels of 100 parts per million can reduce the growth rate of broilers.”
Dairy and beef cattle are the most resistant to fusarium because of the action of the rumen, but there still can be effects on performance and immunity, Smith said.
“At 200 parts per million, there can be a reduction in milk production of dairy cows,” he said.
One study conducted at the University of Missouri with Holstein cattle, Smith reported, showed that as much as 440 parts per million of fumonisin was required to reduce the performance.
“You will never find that high of a concentration in a complete ration,” he said.
The challenge is the indirect impact of fumonisin that can contribute to immunosuppression.
“Beef cattle can become sensitive and have a loss of immunity,” Smith said. “There can be lingering health problems in the herd with animals that don’t respond to medications, uneven growth rates and possible failure of vaccination programs.”
Trichothcecenes are a family of toxins that are most commonly found in DON.