2009 corn will carry a reputation for many years about the significant problems with molds, potential toxins and the quandary that it put livestock producers in determining whether to feed it. The ill-fated growing season resulted in a myriad of mold problems throughout the Cornbelt. Farmers, livestock producers and elevator managers all became familiar with a vernacular that included: diplodia, gibberella, DON, vomitoxin and a variety of other biological agents that are rarely found in typical years. But the primary question that continues to arise is whether the corn that is being delivered to the feedlot, the dairy barn or the confinement building should be fed.
A livestock producer does not want to take any chances either with loss of animals or a small decline in growth, milk production, breeding schedule or any other performance issue. University of Wisconsin (UW) dairy specialists Patrick Hoffman and Randy Shaver and UW plant pathologist Paul Esker prepared a lengthy research advisory to help livestock producers obtain answers to critical mold-related feed questions.
Since a majority of their constituents are feeding silage, the Wisconsin researchers looked at the abilities of the primary field molds to survive and grow in a silage environment. They say when corn is ensiled, the environment will not likely allow the molds in question to survive because of pH and lack of oxygen, and incapable of producing toxins. However, they say there are options for oxygen to enter the silage through holes in bags, bunkers, and silos and create the opportunity for the molds to produce toxins. They say high-moisture corn in an oxygen-rich atmosphere would become moldy, caked and discolored and should not be fed to dairy cattle, but discarded.
They report that if the surface of the high-moisture corn is heating, it does not imply that molds are growing and producing toxins. They say some yeasts can survive in such an environment, but will not produce toxins. However, they may cause the corn to become unpalatable to the animal, and performance will decline. Some producers have considered the use of organic acids to kill the molds, but the researchers say if the toxins were in the corn initially, they will remain.
If you have concerns that toxins might be present, the researchers’ recommendation is to have the corn or silage tested, and treat with caution any tests that indicate mycotoxins are not present. A serious mold may not have had the environment to produce the toxin, and the toxin could be present, but evidence of the mold may have deteriorated. The researchers say many producers have tried to use a black light to identify a mold, but black lights only cause aspergillus to fluoresce. While aflatoxin may not be present, other toxins may be that won’t fluoresce with a black light.
Suppose a mycotoxin was found at a specific level in shelled corn. Your course of action would be to calculate the feeding rate of the corn in the total ration and determine whether the concentration of the toxin was beyond the limits of safety. Do not feed the corn if the threshold has been surpassed. If it hasn’t been surpassed, the grain can be fed, but only with careful monitoring of animal health and performance. Corn that is beyond the threshold could be fed if blended with safe corn to reduce the overall level of toxicity. Corn that may have multiple toxins should only be fed based on the most limiting threshold.
Producers who have toxins in corn have been inquiring about the use of mycotoxin binders or adsorbents that prevent digestibility. The researchers say there are no such products approved by the U.S. Food and Drug Administration (FDA) as a mycotoxin binder, even though some companies that produce feed additives indicate their product may address your needs. They report that any attempt to address a mycotoxin issue with a binder would have 14,400 potential outcomes based on all of the variables that must be considered.
Asked if the presence of DON or vomitoxin at a level of 1 part per million (ppm) was a concern, the specialists indicated that 50% of all corn silage samples contained more than 0.5 ppm of vomitoxin, and its impact on dairy cattle was not well-established but was linked to poor performance. They report that DON may have gotten the name of vomitoxin because it was detected in feeds that caused hogs to vomit. They suggest that whenever total dietary levels of DON are above 0.5 ppm the livestock should be closely monitored for any ill effects or poor performance.
The Wisconsin researchers, knowing that some livestock producers may consider pro-active nutritional strategies when mycotoxins are in the feed, indicate the advantages of supporting the immune system of dairy cattle are not well-known. They report on Vitamin E and selenium needs, but say that is expensive and should be monitored. They warn about “going overboard” with supplements that enhance immunity. To manage the use of corn, which may contain mycotoxins, the researchers suggest that suspect corn be kept away from high-producing lactating dairy cows, but could be given to a less economically important animal, such as heifers.
Livestock operators with potentially toxic corn from the 2009 harvest should be wary of the molds that may produce mycotoxins that will be detrimental to livestock performance. They urge testing to determine which toxins are present and to know the threshold levels of how much of the toxin can be in the feed before livestock health is jeopardized.