By Rick Lundquist
I hate dealing with mycotoxins. Mycotoxins can theoretically be implicated in every health or production problem except maybe snakebite. We nutritionists may use mycotoxins as a scapegoat, but don’t let us do it without some proof. Mycotoxins in forages are particularly troublesome. With grains and byproduct feeds, it’s easier to identify the problem feed and deal with it. But what do you do with a bunker full of mycotoxin contaminated silage?
There are all kinds of mycotoxins that can infect forage. Aflatoxin is the most identifiable. About 1.7% of feed alflatoxin ends up in the milk, so 30 ppb of alflatoxin in the TMR will result in .5 ppb, the legal limit in the milk (30 x .017 = 0.5). Deoxynivalenol (DON or Vomitoxin) is also common and is a marker for other toxins. Zearalenone, an estrogenic compound, is not very toxic but can result in reduced conception and early mammary gland development in heifers. Fumonisins will be in all corn products. T-2 toxin is nasty stuff. I’m told it’s on the biological weapons list, so don’t tell anyone if you have it. Ochratoxin, PR toxin and roquefortine produced by Penicillium molds are also bad. I toured the Roquefort cheese caves in Roquefort, France, last winter. This is very good and expensive cheese purposely laced with Penicillium roqueforti mold. Go figure.
Testing for mycotoxins in forages is difficult. There may be hot spots in the forage, so sampling is a challenge. After you dig in the pile with your hands and take a big whiff of the forage, you send it to the lab and hope like heck it doesn’t contain some deadly toxin. The mycotoxin quick test or ELISA was developed for grains, not forages, and will give you false positives. Chromatography is more expensive and takes longer, but is the only reasonably accurate method for testing forages. I once checked a silage sample by ELISA that tested so full of toxins that you would need a HAZMAT suit to feed the stuff. When the chromatography results were finally complete, it came back clean. In the meantime, the dairy producer and I were going nuts trying to figure out what to do with his “toxic” silage crop. Here are three labs I’ve used for forage mycotoxin testing by chromatography: North Dakota State University Veterinary Diagnostic Lab (www.vdl.ndsu.edu), Romer Testing Lab (www.romerlabs.com) and Trilogy Analytical Lab (www.trilogylab.com).
The best way to deal with mycotoxins in forage is to try to prevent or minimize their growth. Use best management procedures to harvest, ensile, store and feed forages to prevent mold growth. Don’t feed visibly moldy hay or silage, and take the spoilage layer off the surface (see Spoiled Silage, Dairy Today, January 2005). A good mycotoxin binder will bind only 10%-15% of mycotoxins (40% for aflatoxin). That’s not very reassuring, so it’s better to prevent mold and mycotoxin growth than to try to deal with the consequences.
Reference: Mycotoxins in Forages. Duarte Diaz, et.al. Proceedings of Novus Presymposium Conference to the 20th Florida Ruminant Nutrition Symposium. Feb. 2009.
--Rick Lundquist is an independent nutrition and management consultant based in Duluth, Minn. You can contact him at firstname.lastname@example.org.
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