With a wet start to the Ontario growing season, the possibility of pre-harvest infection of wheat, barley and other small grains by Fusarium fungi is high this year. In addition to reducing quality and yield, Fusarium also produces mycotoxins, such as deoxynivalenol (DON) and zearalenone (ZONE), which contaminate the cereal crop. These mycotoxins, at high enough levels, produce toxic effects in livestock, especially swine.

Feeding Wheat to Swine

Economics and mycotoxin levels will determine the most cost effective amount of wheat to include in a ration. In general, starter and grower-finisher rations can include up to 100% of the grain portion of the ration as wheat. In lactation and gestation diets, wheat should be restricted to 50 per cent of the grain portion of the ration. When wheat is used in pig feeds, close attention to feed processing and fineness of grind is essential to avoid problems with palatability, bridging in feeders and incidence of stomach ulcers. Mycotoxins tend to be concentrated in the hulls or outer covering of grains. As a result, mycotoxins may be as much as five times higher in grain by-products, such as wheat middlings or wheat shorts. This may be a year to be extra careful feeding these types of by-products on farm or in complete diets. Another point to remember is that mycotoxin-contaminated straw can be a source of toxicity, especially for gestating sows housed on straw that are being limit-fed.

Guidelines for Feeding Mycotoxin-Infected Wheat

The optimum solution is to buy clean grain for swine and feed the contaminated grain to cattle. Feeder cattle should be able to safely consume levels five to ten times higher than swine. If contaminated wheat must be fed, the following table lists maximum levels in swine diets for DON and ZONE. Please note that these levels should be adjusted downward if feed intake is reduced or other obvious signs of toxicity are observed.

Initial Corrective Steps for Fusarium-Infected Wheat

• clean moldy grains, remove fines and light-weight grains suspected of mycotoxin contamination.
• dilute mold- or mycotoxin-contaminated wheat with mold-free grains. if moderate effects on animals are noted, reduce the inclusion of the suspected wheat by 50 per cent of the amount in the ration.
• if effects on animals are severe, discontinue use of the wheat for at least a week. If improvements are noted, sample the wheat and have it retested to determine the safe level to feed.

Practical Nutritional Steps That May Help

• if mild contamination is suspected, increase the nutrient levels of the ration to help compensate for the reduced intake.
• increase the levels of vitamins, minerals, and amino acids by 5-20 per cent,depending on severity of feed refusal.
• add an appropriate mold inhibitor (sodium or calcium propionate or organic acids) to stored grain to prevent further development of molds.

The extent to which this year's cereal crops are infected with mycotoxins is not yet known. However, if you are planning to feed new crop wheat or other small grains to swine, mycotoxin analysis and management steps to reduce contamination should be strongly considered.

For more information on mycotoxins and their effects on swine please visit the OMAFRA Swine Feeding and Nutrition web site.

August 2008