Cool, damp weather during the 2009 growing season in the U.S. has resulted in significant mycotoxin contamination of corn and other feedstuffs, presenting a major challenge to poultry producers. The mycotoxins of concern are those produced by fusarium fungi with the most common being deoxynivalenol (DON, vomitoxin) and zearalenone. Zearalenone is an estrogenic mycotoxin that can cause infertility. Although mammals are sensitive to zearalenone, poultry appear to be quite resistant.
DON is a member of the trichothecene group of compounds which also includes T-2 toxin, DAS, nivalenol and perhaps as many as 100 others. DON can be found in free form as produced by the fungus and also in masked forms, which are metabolites produced by plants invaded by the fungi.
There are three modes of action of DON and the other trichothecenes
DON is pharmacologically active and this causes behavioral changes such as loss of appetite, loss of muscle coordination and lethargy.
- DON inhibits protein synthesis and this causes necrosis of epithelial cells. The tissue most affected in the manner is the lining of the intestinal tract. This can cause bleeding into the intestinal lumen, increased frequency of ulcers and damage to the absorptive surfaces causing reduced nutrient uptake.
- DON is immunosuppressive. This can cause lingering health problems in the flock, which becomes non-responsive to medication and vaccination.
Effects of mycotoxins
Recent studies have focused on the effects of feeding diets naturally contaminated with fusarium mycotoxins to turkeys and broiler breeder pullets. Growth depression, immunosuppression and changes in intestinal morphology were seen primarily in the first six weeks post-hatching with about 2.5 mg DON per kg of turkey feed. The major morphological changes were reduced villus height and reduced villus surface area in the duodenum and ileum.
In a similar study with broiler breeder pullets, feeding contaminated diets also reduced villus height in the duodenum but villus height was significantly increased in the ileum indicating that birds could compensate for the damage caused by the toxin. It was also shown that intestinal mucosal immunity was depressed by feeding contaminated diets.
The adverse effects of feed-borne mycotoxins were largely prevented in controlled studies by the feeding of a glucomannan-based, yeast derived mycotoxin adsorbent (Mysocorb from Alltech, Inc.). It can be concluded that the most cost effective approach available to the feed industry to combat the current mycotoxin challenge is to incorporate a suitable adsorbent in feed.