Watch for mycotoxins

As corn harvest winds down, farmers need to watch for potential molds and fungus in corn. Fields that were hit with late-summer hail could pose a particular risk. Also drought-stressed corn is susceptible to aflatoxin-- a toxic metabolite produced by the ear-rotting fungus Aspergillus flavus.

With the high levels of distillers dried grains with soluble fed to swine today, mycotoxin monitoring should always be on producers’ checklist. During the ethanol production process, mycotoxins become concentrated in DDGS to the tune of three to four times the level in the original corn source. With growing interest in alternative feedstuffs, it’s worth noting that wheat-mids can carry high mycotoxin levels as well. 

With harvest 65 percent complete, delays haven’t been a concern, but the risk of molds and toxins worsen as the crop remains in the field.

Kansas State University Extension swine specialists Mike Tokach and Joel DeRouchey offer the following advice  regarding mycotoxin issues and swine.

•If possible, clean the grain before storage. Removing damaged kernels lowers toxin levels (by about 50 percent).

•Store at less than 15 percent moisture (13 percent or less is ideal) to limit further fungal growth and toxin production.

•Flush to clean the system after handling contaminated corn (put flush in a contaminated bin).

•Consider adding propionic acid to corn before it goes into storage if fungus is present and a possible concern. 0.5 percent addition of propionic acid limits further fungal growth.

•Monitor grain bin temperatures as hot spots will increase fungal growth and toxin production.

•Segregate corn into high- and low-mycotoxin-level bins if possible. Corn with less than 20 parts per billion can be fed in sow, nursery and late finisher diets. Corn with greater than 20 ppb can be fed to finishing pigs.

•Use low-test-weight corn quickly. It does not store well.

•Monitor dried distillers grains with soluble supplies as Aflatoxin may be four times higher in DDGS than in the corn used to make it

“Keep in mind that aflatoxin is a carcinogen, and that levels build up in the body over time,” Tokach says. “So, when feeding corn that contains aflatoxin, there may be reduced feed intake in the short term, but it’s the long-term where the biggest negative impact can occur.” When feeding to grow/finish pigs, there’s often no adverse effect if corn contains less than 200 ppb aflatoxin, but at 200 to 400 ppb reduced growth can occur and immune systems can be compromised, he notes. At 400 to 800 ppb, liver lesions can occur.

Aflatoxin-infected corn at less than 100 ppb typically does not affect sows, Tokach says. However, at the 500- to 750-ppb range, piglets will grow more slowly due to aflatoxin in the sow’s milk.

For nursery pigs, there’s no effect if aflatoxin levels are less than 20 ppb.

Binders such as such as bentonite or aluminosilicate at 10 pounds per ton, can mitigate aflatoxin’s impact, DeRouchey adds. “Research shows that bentonite will bind up to 700 ppb of aflatoxin. You do not need to add a binder to finishing diets if levels are 200 ppb, except in the late-finishing diet,” he notes.

While research shows that higher aflatoxin levels can be tolerated when bentonite is added to the diet, U.S. Food and Drug Administration require that corn fed to young pigs contain less than 20 ppb, for breeding animals less than 100 ppb and for finishing pigs, less than 200 ppb.

FDA rule require corn exceeding 200 ppb, to be blended with other corn to drop the aflatoxin level before feeding. Blended corn must be used on-site and cannot be sold.

DeRouchey and Tokach advise producers to use clean corn (less than 20 ppb aflotoxin) for nursery and lactating sows, and use corn with levels exceeding  20 ppb for finishing-pig diets.

Iowa State University’s Iowa Pork Industry Center also offers publication, “Mycotoxin Contamination of Corn: What it is, what it does to pigs, and what can be done about it” (IPIC12). Written by John Patience, Iowa State swine nutritionist, and Steve Ensley, clinician with the veterinary diagnostic and production animal medicine department, it’s available to download at no cost from the IPIC website.

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