Tri-State Swine Nutrition Guide

Bulletin 869-98

Mycotoxins

Several mycotoxins are reported to be present in grains and in stored feedstuffs, but only five have been shown to cause much difficulty with swine in the United States. Those mycotoxins, their causative organism, and their most important effects are discussed and presented (Table 19).

The most serious mycotoxin threat to swine is from aflatoxin. This mycotoxin is not generally present in the feed grains grown in the tri-state area, but is common in feeds from the South. Aflatoxin is produced by the common soil microorganism Aspergillus flavus and is a major problem in peanuts and their by- product feeds. Aflatoxin can, however, occur in corn and other grains when growing conditions are hot and dry. Aflatoxin is a toxic product, causing liver damage, reduced growth, and feed conversion at levels above 100 ppb. It can be carcinogenic, and FDA regulates the maximum dietary level at 20 ppb.

Deoxynivalenol (DON) is often called vomitoxin because of its strong emetic effect on the animal. Because of the very strong feed refusal response which DON elicits, pigs are seldom seen vomiting. The pig seems to be more sensitive to the presence of this mycotoxin in feed than other livestock species. Starvation is the condition usually observed. Poor performance associated with poor feed intake occurs above a dietary level of 1 ppm.

Zearalenone is produced by the same organism as DON but usually is formed under different conditions. The two metabolites (DON, zearalenone) may therefore be found together or separately in feeds. Zearalenone consumption will produce vulva swelling, prolapse, pseudopregnancy, false heat symptoms, and other estrogenic problems in the reproductive process. The organism that produces DON and zearalenone has been a source of confusion in taxonomy, and its name and classification have been changed more than once. Fusarium roseum is now the accepted name, but a particular stage of the organism, Gibberella zeae, produces the toxins and has been used by many to avoid some of the confusion with other terms. It is from this latter name of the organism that the term "Gib corn" originates.

Fumonisin is a recently discovered mycotoxin that is extremely toxic to horses and often is fatal. It can affect swine, causing pulmonary edema and liver damage. The organism producing this mycotoxin, Fusarium moniliforme, is a very common organism often present with no production of fumonisin. There is limited evidence regarding toxic levels, but dietary concentrations below 10 ppm appear to be without discernible effect in swine.

Ergot is a parasitic fungus of the Claviceps genus. Claviceps purpurea grows mainly on rye, wheat, triticale, and barley. Rye and triticale seem to be most susceptible. The fungus replaces the seed in the heads of these cereal grains and produces several (four primary) alkaloids that are toxic to pigs and most other animals. This mycotoxin (alkaloids) causes vasoconstriction of blood vessels and eventually gangrene of the limbs. Ergot-infested grain should never be fed to pregnant animals and should be used sparingly in grower/ finisher pig diets.