Deoxynivalenol (DON) is mainly produced by strains of Fusarium graminearum and F. culmorum.6, 12 These fungi can tolerate a broad array of climate conditions with establishment being aided by cool, humid conditions.6, 10 The spores (conidia) that are transported with the wind, attach to the plants through the silks of the corn and the anthers of the male flowers.6, 8 The fungus uses these gateways and insect vectors including corn borer and thrips to penetrate the plant and generate the infection with the production of the mycotoxin. DON occurs as predominant mycotoxin in the northern part of the globe and due to the adverse effects in animals, this mycotoxins is known as one of the most significant for animal production.11 The total maximum concentration allowed in feed and foodstuffs is regulated in the EU (see table 1) and there are recommendations available in the USA.5 Due to its emetic (vomit causing) effect, DON is also known as vomitoxin and feed refusal is also common. DON is a polar and water-soluble chemical compound belonging to the group of type B trichothecenes. DON is heat-stable, being able to partially withstand temperatures within the range of 170°C to 350°C, with no reduction of DON concentration after 30 min at 170°C.1, 3, 4, 7
The toxic effects of DON are due to the free OH groups and the epoxide ring.8, 9, 10, 12 The latter is a common feature in all trichothecenes. Potential impacts on human and animal health occur after ingestion of contaminated material. Swine are the most sensitive specie and concentrations above 1000 ppb can be potentially harmful.2, 3, 4, 7 The main toxic effect of DON is the inhibition of protein synthesis and mitochondrial function. Because this affects fast growing cells in particular, DON leads to effects such as immunosuppression and immunomodulation (increased susceptibility to opportunistic and general pathogens) and cytotoxic effects.2, 3, 7, 8, 9, 12 Effects on the gastrointestinal tract include gastroenteritis (swelling of stomach and intestine); impairment of gut integrity and impact on intestinal microflora; diarrhea; intestinal bleeding; anorexia; decreased nutritional efficiency; increased liver size; severe immunosuppression; decrease in feed intake and reduced weight gain.2, 3, 7, 8, 9, 12 Other effects that are common among this class of trichothecenes are general weakness; destruction of bone marrow; decline in serum proteins and albumin levels; decrease in hematocrit (red blood cell concentration in blood); reduction of serum calcium and phosphorus; neurotoxic effects.2, 3, 7, 8, 9, 12
In the EU, the guidance values for DON in feed material are listed in table 1. In the USA the advisory levels for DON are as follows:13
USA FDA Advisory levels
1 ppm DON on finished wheat products, e.g. flour, bran, and germ, that may potentially be consumed by humans. FDA is not stating an advisory level for wheat intended for milling because normal manufacturing practices and additional technology available to millers can substantially reduce DON levels in the finished wheat product from those found in the original raw wheat. Because there is significant variability in manufacturing processes, an advisory level for raw wheat is not practical.
10 ppm DON on grains and grain by-products (on an 88% dry matter basis) and 30 ppm in distillers grains, brewers grains, and gluten feeds and gluten meals derived from grains (on an 88% dry matter basis) destined for ruminating beef and feedlot cattle older than 4 months and ruminating dairy cattle older than 4 months, with the added recommendations that the total ration for ruminating beef and feedlot cattle older than 4 months not exceed 10 ppm DON, and the total ration for ruminating dairy cattle older than 4 months not exceed 5 ppm DON. For chickens, 10 ppm DON on grains and grain by-products with the added recommendation that these ingredients not exceed 50% of the diet of chickens.
5 ppm DON on grains and grain by-products destined for swine with the added recommendation that these ingredients not exceed 20% of their diet.
5 ppm DON on grains and grain by-products destined for all other animals with the added recommendation that these ingredients not exceed 40% of their diet.
|Products intended for animal feed||Guidance value in mg/kg (ppm) relative to a feedingstuff with a moisture content of 12 %|
|Cereal and cereal products with the exception of maize by-products||8|
|Complementary and complete feedingstuffs with the exception of feed for pigs, calves lamb and kids||5|
|Complementary and complete feedingstuffs for pigs||0.9|
|Complementary and complete feedingstuffs for calves (<4 months), lambs and kids||2|