The widespread and sporadic incidence of ear mold in the Ontario corn crop may result in quantities of mycotoxin-contaminated corn being available as livestock feed.

Guidelines for feeding mycotoxin-infected corn

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 10 times higher than swine. If contaminated corn must be fed, the following table lists maximum levels in swine diets for vomitoxin and zearalenone.

 Age Group
Vomitoxin (DON), ppmZearalenone, ppm

These levels should be adjusted downward if feed intake is reduced or other obvious signs of toxicity are observed.

Source: Kansas Swine Nutrition Guide

The practical level of corn in a ration depends on several factors

  • all classes of pigs may consume corn at levels up to 100% of the grain portion of a ration.
  • the economics.
  • the mycotoxin levels will ultimately determine the acceptable amount in a ration.

Initial corrective steps for Fusarium infected corn

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

Sampling method for dry feeds (Penn State University)

  • Take 8 - 12 samples at each of 3 - 5 feedings or feed removal from storage, or take 12 - 20 stream samples from an entire delivery, or 12 - 20 deep probe samples from a bin. Include samples from the sides of bins or edges of storage where mold is likely to occur.

Mix the subsamples well, take a 500 g composite sample for submission to the laboratory. Some labs recommend taking a composite sample of 1 kg for mycotoxin analysis.

  • Keep an additional 500g sample for confirmation or other analyses.
  • Store all samples in clean double layer paper (grocery store) or cotton bags.
  • Store in a cool dry place. Submit to the lab as soon as possible.
  • Always check the basis on which results are given - often they are on an as-fed basis. Correct these to a dry matter basis so that inclusion rate can be calculated.
    eg. Corn with 15% moisture analyzed at 5 ppm DON as-fed.
    100 - 15 = 85% dry matter
    5 / 0.85 = 5.9 ppm DON on a dry matter basis.
  • Results may be expressed in a number of different ways
    ppm = mg/kg = ug/g = 1,000 ppb

Calculate the maximum inclusion level of moldy corn

  • In the total ration dry matter (TRDM),
    % maximum inclusion rate = safe level in TRDM / level in corn DM x 100
    eg. for lactating sows, maximum level DON is 1 ppm
    if corn analysis is 5 ppm DM then:
    1 / 5 x 100 = 20% maximum inclusion level in TRDM based on DON level.
    This does not exceed the nutritional limits listed above. Corn DON levels above 5 ppm will reduce the maximum inclusion level below 20% corn in TRDM.
  • Use the limits for the other toxins analyzed and repeat the same calculations as above to determine if they may be more limiting to acceptable inclusion rates for corn.
  • Despite these calculations, poor palatability of moldy corn may lower feed intake. Palatability of the corn may ultimately determine acceptable inclusion rates. If in doubt, err on the conservative side and watch for problems!

Practical 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% 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.

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