Tri-State Neighbor: South Dakota Farm Newspaper

Autumn spells the time to clean out old crop corn and harvest and store new crop. It's also a good time to evaluate whether mycotoxin contamination problems are present, especially if corn is going to be fed to swine. Mycotoxins are compounds produced in grain by specific molds or fungi as secondary metabolites. Molds in grains do not automatically indicate mycotoxin presence.

Mycotoxin production can occur during plant growth and maturity or during storage of grains, and is influenced primarily by moisture level, temperature and availability of oxygen. In addition, grain that is damaged, immature, drought-stricken or otherwise stressed is more susceptible to mold growth. Molds may also reduce the nutrient content and quality of the grain, but the toxic effects of metabolites are generally of primary concern.

Mycotoxins that have been shown to be detrimental to health and performance in swine include aflatoxin, deoxynivalenol, zearalenone, fumonisin, ochratoxin, ergot and T-2 toxin. Aflatoxin often receives the most attention, since it has been shown to be a carcinogen and is regulated by the FDA. The mold that produces it, however, is abundant primarily in the southeastern United States, and therefore it rarely is a problem in the Upper Midwest.

Mycotoxins that are more often observed in Minnesota corn include deoxynivalenol, zearalenone and fumonisin. The molds that produce these mycotoxins commonly develop during cool damp weather, similar to what we are now experiencing. Deoxynivalenol, commonly known as vomitoxin, reduces feed intake and growth at levels above 1 part per million, and may induce feed refusal and/or vomiting at levels above 5 parts per million. Zearalenone acts similar to estrogen, causing irregular estrous cycles and reducing litter size and overall reproductive performance in the breeding herd, while fumonisin has been shown to weaken immune system function and cause pulmonary edema.

Young pigs and breeding swine are generally the most susceptible to mycotoxins. Combinations of certain mycotoxins may produce elevated negative effects on performance above that normally expected for each of the mycotoxin levels evaluated individually, and therefore must be considered.

Once grain is contaminated with mycotoxins, there are no known methods of detoxifying the mycotoxins. There are management strategies that can minimize the effects of mycotoxins on swine health:

1. Feed the suspect feed or grain to a small number of "test" animals and closely watch for symptoms of mycotoxicosis. Pre-pubertal gilts are often good "test" animals when checking suspected feed for zearalenone (swollen vulvas) and vomitoxin (reduced feed intake).

2. Collect samples of the suspect grain and send to a commercial analytical laboratory for determination of levels of mycotoxins. Once the levels are known, contaminated grain can be blended with good quality grain to dilute the concentration of mycotoxins below critical levels.

3. Try marketing the grain to cattle (not dairy cows if aflatoxin-contaminated) or sheep producers. Ruminants are less sensitive to mycotoxicosis than pigs and poultry. Uncontaminated grain can then be purchased to avoid health problems and performance reductions.

4. Consider putting grain through a grain cleaner to remove fines. Broken and damaged kernels are generally highest in mycotoxin contamination. Avoid feeding grain screenings and fines to swine.

5. Sodium bentonite and a commercial feed additive called Novasilª have been shown to be effective in minimizing the adverse health and performance effects of pigs fed aflatoxin contaminated feeds. They may also have some benefit in partially alleviating negative effects from other mycotoxins.

6. Be sure that stored grain is dried and aerated to recommended moisture levels to prevent further mold growth and mycotoxin production. Consider adding commercially available additives or organic acids (propionic, fumaric, citric) to prevent mold growth.

7. Avoid feeding mycotoxin-contaminated grain to the breeding herd and young pigs. Grow-finish pigs fed for slaughter are the best candidates for tolerating mycotoxin-contaminated grain.

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