Molds and Mycotoxins - Alleviating Mold and Mycotoxin Problems

• Investigate and eliminate other possible causes of the problems experienced before concluding that molds and mycotoxins may be involved.

• Expect improved production and/or health one to several weeks after corrective measures have been taken. Prolonged exposure to mycotoxins, weeks or maybe months, 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

  • adjust the energy levels of moldy feeds or light weight grains (5 - 10% lower) and reformulate rations

• Dilute contaminated feed with mold-free feed. This requires that the contaminated feed is analyzed so that it is adequately diluted in the final ration dry matter to ensure safe 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 results are given - often they are on a as-fed basis. Correct these to a dry matter basis so that inclusion rates can be calculated. eg. A "feed" with 65% moisture analyzed at 2.5 ppm DON as- fed. 100 - 65 = 35% dry matter 2.5 / 0.35 = 7.1 ppm DON on a dry matter 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. (= maximum recommended level above)

• 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 given above).

• 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 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.

• 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 time 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 the mycotoxins and they are concentrated up in the distillers by- products.

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