Nutritionist > Pig
Trichothecenes
(T-2 toxin, Diaceptoxyscirpenol (DAS), Deoxynivalenol (DON), HT-2 toxin etc.)
Trichothecenes are a group of toxins produced by several Fusarium fungi, notably Fusarium graminearum and Fusarium sporotrichioides. The most important structural features causing the biological activities of the Trichothecenes are the 12, 13-epoxy ring, the presence of hydroxyl or acetyl groups and the structure and position of the side-chains.
Trichothecenes are typical field toxins. They are produced on crops and enter the feed via contaminated ingredients. Trichothecenes are proven tissue irritants with the major observation associated with their ingestion being oral lesions, dermatitis and intestinal irritation.
The major physiological response to trichothecenes mycotoxins is loss of appetite, thus earning them the name, feed refusal toxin. Trichothecenes are strong immune suppressive mycotoxins affecting cellular immune response by directly affecting bone marrow, spleen, lymphoid tissues, thymus and intestinal mucosa, where actively dividing cells are damaged.
Vomitoxin (Deoxynivalenol or DON)
Deoxynivalenol (DON) is commonly known as vomitoxin. This mycotoxin is produced by Fusarium graminearum that often occurs on corn (Gibberella ear rot), wheat and barley (Head scab). The mould usually develops during cool damp weather, resulting in a white or reddish fungus.
Levels above 1 ppm may reduce feed intake and subsequent rate of weight gain. Concentrations above 5 ppm result in feed refusal and above 10 ppm may result in weight loss and vomiting. When contaminated feed is replaced with clean, uncontaminated feed, pigs will generally resume consuming feed with no other visual apparent signs.
Vomitoxin:
- Affects the gastro-intestinal tract (for example lesions)
- Levels of 1-2 ppm cause a reduction in feed intake and, as a result, rate of gain
- As levels increase above 5 ppm, feed intake depression may become severe
- Levels of 10-20 ppm cause vomiting and complete feed refusal, resulting in reduced body weight gain or body weight loss
- Pigs will initially consume sufficient amounts of the ration to induce vomiting, but will voluntarily reduce intake to stop vomiting
- Sows are more tolerant than young pigs
- Low levels can suppress the immune system
- More potent but less common than vomitoxin
- More likely to be produced during long periods of cool wet weather
- 1 ppm or greater causes vomiting and decreased feed intake and growth rates
- Levels of 16-20 ppm cause complete feed refusal
DON or vomitoxins are the most common toxins and have a major effect on pigs. The large family of compounds is generally implicated when there is feed refusal, vomiting and lesions of the gastro-intestinal tract in pigs. The health of pigs is also affected due to the immuno-suppressive effects of the mycotoxins. Liver weight is increased, whereas hepatic protein synthesis is reduced. Brain serotonin concentration and activity may also be increased.
Several studies have shown that at 3-5 mg/DON/kg feed, appetite in pigs is greatly depressed, resulting in reduced pig performance. This has considerable consequences for the lactating sow, since reduced appetite influences milk yield and piglet growth rate and leads to greater weight loss and poorer body condition at weaning. This lengthens the wean-oestrus interval and affects subsequent reproductive performance.
Intervention level
Because of the decline in appetite and performance, as well as the immuno-suppressive effects, it is recommended that action be taken if the concentration of DON in animal feed is >0.2 ppm.
