Quite a few pig farmers in the US and also in other countries grow their own corn. Depending on harvest conditions the crop can be infected by Aspergillus flavus, causing aflatoxin contamination.
Also 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-middlings can carry high mycotoxin levels as well.
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%).
Store at less than 15% moisture (13% 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% 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 DDGS 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 5kg per tonne, 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, US 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.