Eyes wide open As spring comes, be alert for mycotoxins

February 23, 2010 09:19 AM

Warm spring weather could bring its own set of nasty surprises as mold on stored grain starts growing again.

Dairyland Laboratories, Inc., based in Arcadia, Wis., tests grain samples from across the Upper Midwest. It reports that 77% of its corn samples were positive for vomitoxin last fall. But less than 5% exceeded 6 parts per million (ppm), the threshold for problems in dairy cows. The eastern Corn Belt was showing more problems than Illinois, Iowa, Minnesota or Wisconsin.

But testing grain isn't a perfect on-farm solution—it's both expensive ($40/sample/mold strain) and less than foolproof because of sampling errors, says Mike Hutjens, Extension dairy nutritionist with the University of Illinois.

"Instead of testing, watch the consistency of your cows' manure and dry matter intake,” he suggests. If manure becomes loose or if dry matter intake drops more than 2 lb./cow/day, you could be experiencing mold problems.

If you're having problems, consider using mycotoxin binders. Make sure the binders you use are effective for the specific toxin you have, Hutjens says.

For example, clay-based compounds will bind aflatoxins. Yeast cell wall extracts (MOS and glucomannans) are effective with T-2 toxins, DON and zearalenone.

Adding these binders to feed could become standard operating procedure in formulating rations for the rest of the year until the 2009 corn crop is fed up, Hutjens says. You might need to double the normal inclusion rate to get the desired effect, which doubles the cost from 8¢ to 16¢/cow/day. Again, watch manure consistency and dry matter intake to gauge the effectiveness of binders.

Adding propionic acid to corn as it comes out of storage will stop the growth of mold. But it will not destroy the toxins that have already been produced and are in the feed, Hutjens says.

Also be wary of distillers' dried grains (DDG). The distillation process actually concentrates mold spores into the feed portion. Of 49 DDG samples tested by Rock River Laboratory, Inc., of Watertown, Wis., 60% tested 5 ppm or above.

"Your distillers' grain supplier should provide you with test results on the feed they're selling you,” Hutjens says. 

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