Dr Andrew Tucker CS Vet
Mycotoxicoses occurs as a result of fungal growth on feed fed to pigs. Many different moulds have been incriminated in causing mycotoxicoses. The following toxins are the more commonly seen ones that produce clearly defined syndromes.• Zearalenone
Zearalenone is a toxin produced by a fungus of the genus Fusarium. These fungi grow on various grains, including maize, and produce various toxins, including zearalenone. Zearalenone levels are highest in grain when rain occurs at the end of the ripening period. Problems with grain storage can also lead to high zearalenone levels.
Zearalenone is absorbed from the ration, inside the pig’s digestive tract. It can then be detected in the pig’s blood and gets excreted via the urine. Levels in the blood remain detectable for five days post administration. Zearalenone is oestrogenic and once in the blood can affect the reproductive system. It does this by depressing certain reproductive hormones which then have an effect to stimulate others. These hormonal changes obviously have an effect on the reproductive system and then potentially disrupt reproductive performance.
Clinical signs seen depend on the level of zearalenone in the feed and include enlargement of the vulva, uterine prolapse, mammary oedema, small litters, lowered conception rate, substandard piglets at birth, increased stillborn piglets, splay-legged piglets and extended weaning to service interval.
Vomitoxin (deoxynivalenol) also referred to as DON is rapidly absorbed and distributed to all tissues. It is also rapidly excreted with plasma being negative 12-24 hours after withdrawal. Ingestion of DON results in vomiting, feed refusal and growth depression, depending on the inclusion level in the feed. Feed refusal can then have a secondary effect on reproduction as well.
Fumonisin toxicity is also known as Porcine Pulmonary Oedema Syndrome. Clinical signs begin about five days after ingestion of the toxin. First signs of toxicity are depression and a rapid decrease in feed intake. At low levels clinical signs are those typical of liver disease. At higher levels pigs show respiratory distress, lung oedema and death.
How do you know if it’s on your farm?
Clinical signs on the farm can be confused with some infectious conditions as well as management problems. The diagnosis of mycotoxin poisoning therefore needs to be made by looking at the whole picture and ruling out other causes. Zearalenone, DON and Fumonisin can all be tested for and confirmed from feed samples.
How do you treat or prevent it?
Ensuring non contaminated feed is the simple answer to prevention and cure. This is however not always as simple as it seems. Avoiding old or poorly stored raw materials goes a long way to preventing the problem. Various sieving and blowing mechanisms also help to reduce the mycotoxin levels. There are various mycotoxin binders on the market which can help if you doubt the quality of the incoming product.
Pig Diseases – D.J. Taylor; Diseases of Swine – Straw, Zimmerman, D’Allaire, Taylor; *Code of practice for the control of mycotoxins in the production of animal feed for livestock (AFMA – June 2003)