These are produced from the fungus aspergillus and are probably the most common and important of the mycotoxins in pigs. The aspergillus species commonly concerned grows in maize, soya beans and peanuts. The main species involved are A. flavus and A. parasiticus and countries where maize and peanuts are not fed aflatoxicosis is uncommon. The effect of the toxins are dependent upon the dose and the age of the pig, the younger the animal and the larger the dose the greater the effect. It is more common for pigs to be exposed to low levels of aflatoxins for long periods of time and the effects therefore tend to be sub-acute rather than acute. Feed levels up to 200ppb produce clinical signs and levels above 300ppb may be fatal.

Clinical signs

These include reduced growth and feed efficiency and at the upper levels the effects of liver damage and failure include jaundice. Aflatoxins do not have a direct effect on reproductive efficiency but abortion and agalactia may occur. They are immuno-suppressive and therefore increase the severity of concurrent diseases, such as PRRS, flu viruses and mycoplasma pneumonia. There are different types of aflatoxins designated B1, B2 and G1, G2 and the effects of the toxins are enhanced where poor quality, low protein diets are fed. If levels in the feed are low it can take four to six weeks for symptoms to appear.

Diagnosis

Wherever there is poor growth in a herd associated with poor nutrition and chronic infectious diseases the possibility of toxins in the feed should be considered and tested for. Post-mortem lesions include jaundice, anaemia, fluid in the abdomen, poor clotting of the blood and liver haemorrhage. Histological examinations of the liver may help to confirm the diagnosis. Follow the steps outlined at the beginning of the chapter and also see "Diagnosis of mycotoxicosis".

Treatment

• There is no specific treatment. Remove the suspect source until it has been tested.
• Raising the vitamin and protein levels in the feed by 10% for two to three weeks, could be beneficial, as could raising the lysine content of the diet to growing pigs by 0.2% for four weeks.