It’s a bad – very bad – idea to take mycotoxin-infected feed unsuitable
for hogs and feed it to poultry, according to Canada’s foremost
authority on mycotoxins, Dr. Trevor Smith from the University of
Guelph.
It’s a bad – very bad – idea to take mycotoxin-infected feed unsuitable for hogs and feed it to poultry, according to Canada’s foremost authority on mycotoxins, Dr. Trevor Smith from the University of Guelph.
Smith told poultry producers and industry representatives at a recent Ontario meeting that decades-old research indicating that fusarium mycotoxins are well tolerated by poultry is wrong. He recently completed research that shows that fusarium reduces birds’ immune systems and can result in a host of problems. He found that fusarium can depress growth rates in broilers, productivity and feed consumption in layers, make turkeys more susceptible to disease and lower the productivity of broiler breeders.
For almost 30 years the accepted procedure for utilizing mycotoxin-infected feeds has been to feed it to the birds. But Smith’s research has changed that practice or procedure to a single word advisory: “Don’t.”
It’s been known for decades that hogs cannot tolerate fusarium-infected grain. Neither can horses. But it was thought — and some limited research supported the theory — that feeding infected grain to poultry was OK. The birds will eat infected grain and it doesn’t immediately make them sick.
But Smith’s research shows that mycotoxins repress the birds’ immune system, making them susceptible to a host of other pathogens. This will result in at best poor performance, and at worst outbreaks of other seemingly unrelated diseases.
Smith presented his research finding to producers at an update sponsored by the Ontario Ministry of Agriculture and Food. He said that feeding birds grains contaminated with fusarium mycotoxins “can lead to significant financial losses for producers.”
“It is a bad idea to direct these feeds to poultry,” he said.
In Ontario this year, an extremely wet fall delayed harvest and consequently huge volumes of corn have come off the fields infected with fusarium, and problems are being detected in Ontario flocks.
“I suspect in Ontario that immuno-supression is the most important factor,” he said.
While the problems can show up as weaker, sicker layers, in broiler breeders it can result in thin eggs and dead chicks. With layers the birds eat more but produce fewer and fewer eggs. “There is a severe loss in production efficiency,” he said.
The research shows that layers are the most sensitive to fusarium, followed by turkeys, and then broilers, he said.
Adding to the problems, current tests for mycotoxins understate the actual amount of fusarium in the grain. Some of it is bound up with glucose and isn’t picked up by the tests, but is nevertheless released in the birds’ digestive tracts.
The grain can be diverted to less susceptible species such as sheep or goats, but there aren’t enough of them to consume much of the grain. Shifting the grain from hogs to poultry “is not a good move,” he said.
Mycotoxins in feed is a problem that seems to be increasing and it’s because of the weather.
Smith said that global warming is resulting in unusual weather patterns such as drought, flooding and temperature extremes that increase the chance of mycotoxin contamination of feed grains.
The increased global trading of feed grains also increases the chance that blends of grains will result in combinations of mycotoxins in a given diet.
The most common mycotoxins are aflatoxin and the fusarium toxins. Analytical procedures to identify aflatoxin are well established, but fusarium mycotoxins are more difficult to analyze due to the large number of compounds with widely varying chemical structures. For this reason, vomitoxin, also known as Deoxynivalenol (DON), is used as a marker compound because it is more easily identified.
Research in Slovakia has shown that there are biologically active, yet undetectable fusarium mycotoxins in glucose conjugates. These undetectable conjugates can represent up to 30 per cent of total mycotoxins.
Some of the fusarium mycotoxins in feed include the fumonisims. In pigs, fumonism at 40 parts per million (ppm) can result in pulmonary edema. In layers, 100 ppm will result in growth depression.
Another mycotoxin is trichothecenes. This is a family of more than 100 related toxins with the most common being vomitoxin. The trichothecenes alter brain chemistry by increasing tryptophan and seratonin levels. They are also dermal necrotic agents and inhibit cellular protein synthesis. They cause hemorrhaging of the intestinal tract, ulcers and gizzard erosion, and this can lead to malabsorption syndrome and sticky litter, he said.
The trichothecenes are also immunosuppressive which makes animals susceptible to secondary mycotoxic diseases.
Also found in grain is zearalenone, an estrogenic fusarium. In pigs, it can bind to estrogen and cause enlargement of the uterus and rectal and vaginal prolapse. Poultry are much more resistant to this mycotoxin than pigs.
Fusaric acid is also found. It has low toxicity but is pharmacologically active, he said.
Fusaric acid results in a drop in blood pressure. It also works together with vomitoxin to reduce feed consumption and induce vomiting, loss of muscle coordination and lethargy.
Research shows that fusaric acid levels in whole feeds are higher (at 35.8 mg/kg) than in dry corn (11.8 mg/kg), high moisture corn (26.4 mg/kg), wheat (11.6 mg/kg) or barley (12.2 mg/kg). This was surprising because soybean meal is refined and doesn’t contain mycotoxins. However, soybean hulls do carry toxins and when the hulls are added to the meal the meal can be contaminated.
Dealing with contaminated grain is complicated, Smith said. One strategy is to dilute the infected grain with sound grain, which will lower the mycotoxin load. The grain can also be cleaned or heated and dried, which will reduce the volume of mycotoxins, but not enough to resolve the problem, he said.
It’s also possible to add enzymes to the diet, but the enzymes are specific for the structure of the mycotoxin. As a result, Smith said that producers would have to add four or five enzymes, which is both costly and difficult.
Another alternative is to feed the birds a mycotoxin absorbant. These feed additives are nondigestible and have large fibres that bind to the mycotoxins and carry them through the birds’ systems before they can be absorbed through the digestive tract.
Several absorbants have been tested, including bentonite (a clay), alfalfa and a polymer made from the cell wall of yeast. The bentonite worked well in tests, but had to be introduced at a high content level and make up five to six per cent of the feed by volume, which isn’t too practical, said Smith.
Alfalfa also had to be fed at a high level and there is a concern that alfalfa may bind with the fusarium, and that it could be infected itself, introducing even greater amounts into the bird’s system.
The research showed that an absorbent polymer tested in the trials could offer significant benefits in dealing with mycotoxins.
Strategies for Preventing Mycotoxicoses
• Dilution with sound grain
• Diversion to less susceptible species
• Processing methods such as cleaning
• Physical treatments such as heat
• Use of mold inhibitors such as propionic acid
• Use of enzymes
• Use of mycotoxin adsorbents
Overall conclusions
• The feeding of grains contaminated with fusarium mycotoxins can alter metabolism and lower productivity of poultry.
• This can lead to significant financial losses for producers.
• Such losses can often be prevented by the use of an appropriate mycotxin absorbent.
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