Molds and Mycotoxins - Alleviating Mold and Mycotoxin Problems

  • You should investigate and eliminate other possible causes of the problems experienced before concluding that molds and mycotoxins may be involved.
  • Expect improved production approximately 5 to 10 days one after corrective actions are taken in many cases. Several weeks to months may be needed to evaluate severe problems related to health and/or reproductive performance after corrective measures have been taken. At high levels, or after prolonged exposure (weeks or maybe months) to mycotoxins, exposure can lead to liver and/or kidney damage and lengthen the time taken for full recovery.
  • Initial corrective steps to be taken include:
    • clean moldy grains, removing fines and light weight grains suspected of mycotoxin contamination
    • reformulate rations to account for the energy levels of moldy feeds or light weight grains (5 - 10% lower)
  • Dilute contaminated feed with known toxin-free feeds. This requires that the contaminated feed is analyzed so that it is adequately diluted in the final ration dry matter to ensure tolerable levels of mycotoxin for the particular class of animal.
  • Wheat grain is typically limited to 15 - 20% of Total Ration Dry Matter (TRDM), 25 - 40% of grain ration for lactating dairy cows and up to 40% of TRDM for feedlot cattle. The actual practical level depends on what other grains are being fed; in particular how rapidly the starch breaks down in the rumen.
  • The maximum safe level of wheat that can be included is also influenced by feeding sequence, feed amounts and bunk/manger management.
  • Always check the basis on which laboratory results are given - often they are on a as-fed basis. Correct these to a dry matter (DM) basis so that inclusion rates can be calculated. eg. A "feed" with 65% moisture analyzed at 2.5 ppm DON as- fed should be interpreted as 100 - 65 = 35% dry matter basis. Therefore 2.5ppm / 0.35%DM = 7.1 ppm DON on a DM basis.
  • Mycotoxin levels may influence the amount of wheat that is acceptable in a ration. Calculate as follows:
    Safe level in TRDM level in wheat DM x 100 = % maximum inclusion rate eg. for lactating cows - maximum level DON is 1 ppm; if wheat analysis is 5 ppm; then: 1 / 5 x 100 = 20% maximum inclusion level in TRDM.
  • As a quick guide, for lactating dairy cows that tolerate a maximum of 1 ppm DON, wheat DON levels above 5 ppm will reduce the maximum inclusion level below 20% wheat in TRDM.
  • As a quick guide, for feedlot cattle that tolerate a maximum of 5 ppm DON, wheat DON levels above 12.5 ppm will reduce the maximum inclusion level below 40% wheat in TRDM.
  • In conventionally fed dairy cows, use the maximum grain level fed, not the average. The average ration may be 50:50 grain to forage but early lactation cows may be up to 60% grain. Calculate as above:
    eg. for lactating cows - maximum level DON is 1 ppm; if wheat analysis is 5 ppm; then: 1 / 5 x 100 = 20% maximum inclusion level in TRDM. then: 20% / 0.6 = 33% maximum in the grain ration. (this is within the acceptable range).
  • Use the limits for the other toxins and follow the same calculations as above to determine if other toxins analyzed may be more limiting than DON on acceptable inclusion rates for wheat.
  • Despite any of the above recommended levels or acceptable levels as calculated, palatability of the wheat may be reduced lowering feed intakes. Palatability may be the greatest determinant of an acceptable wheat (grain) inclusion level in the ration.
  • If in doubt, err on the conservative side and watch for problems!
  • Include aluminosilicate or bentonite in ruminant rations at 0.5% to reduce the effects of mycotoxins (or follow manufacturer's recommended rates). These compounds may bind mycotoxins in the digestive tract and reduce their absorption. Most effective against aflatoxin and to a lesser extent the other mycotoxins.
  • Aluminosilicate or bentonite in ruminant rations have improved performance in the field with Fusarium mycotoxins, but controlled research is either somewhat lacking or non supportive.
  • No products in Canada are registered yet by the Canadian Food Inspection Agency to have a label claim for mitigating the effects of toxins. You may wish to discuss additional options with your nutritionist or veterinarian.
  • In an attempt to alleviate the effects of mycotoxins, increase the levels of Vitamins A, E and B1 and trace minerals Selenium, Zinc, Copper and Manganese. Again there are only anecdotal suggestions that levels be increased by up to 25%. Note any overriding considerations; eg. copper levels in sheep rations.
  • Add an appropriate mold inhibitor (sodium or calcium propionate or organic acids) to stored grain to prevent further development of molds.
    • add 0.2 to 0.25% to non-ensiled feeds with 14 - 17% moisture
    • add 0.5 to 0.6% to non-ensiled feeds with 18 - 24% moisture (or follow the manufacturer's recommendations)
  • Other pointers to consider:
    • if moderate effects on animals are noted, reduce the inclusion of the suspected feed by 50% in the ration
    • more serious effects on animals require that the suspect feed be discontinued for at least a week. If improvements are noted, have the feed tested, if positive discontinue use or have level of mycotoxin tested so that appropriate levels of the feed can be fed
  • Avoid these potential pitfalls:
    • Mycotoxins tend to be concentrated in the red dog, husk, light grains, and broken kernels. Mycotoxins may be as much as five times higher in the screenings compared to the grain. This may be a year to be extra careful feeding "grain screenings".
    • Contaminated grains that may be used in the fermentation industry pose a potential problem. The fermentation process does not break down mycotoxins and they are concentrated up in the distillers by-products. In years with toxin problems (in Ontario or the United States, depending on the source of the by-product) you should ask about toxin status of the feed and to see a laboratory result for that load. Toxin levels in corn distillers grains are approximately three times higher than the toxin level in the original grain corn prior to the ethanol fermentation process.

For more information:
Toll Free: 1-877-424-1300
Author: Tom Wright - Dairy Cattle Nutritionist/OMAFRA
Creation Date: 08 August 1996
Last Reviewed: 12 February 2016