Swine Producers Urged to Guard Against Aflatoxin in Corn

by 5m Editor
31 August 2011, at 12:00am

Soaring temperatures and drought conditions through parts of Kansas and other states are sparking some cases of aflatoxin in corn, which means swine producers should be vigilant about what they are feeding, according to Kansas State University scientists.

"Aflatoxin is a toxic metabolite produced by the ear-rotting fungus Aspergillus flavus," said Doug Jardine, state plant pathology leader with K-State Research and Extension. It is favoured by hot, humid and drought conditions during the grain-fill period."

K-State extension swine specialists, Mike Tokach and Joel DeRouchey, outlined several points for producers to keep in mind regarding feeding corn to swine.

  • Harvest contaminated corn fields as quickly as possible. Once it appears, toxin levels appear to continue to increase in fields due to mould growth.

  • Clean the grain if possible, before storage. Removing damaged kernels lowers toxin levels (by about 50 per cent).

  • Store at less than 15 per cent moisture – 13 per cent 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 concern. 0.5 per cent addition of propionic acid limits further fungal growth.

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

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

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

  • Monitor DDGS (dried distillers grains with soluble). 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," Dr Tokach said. "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 in grow-finish situations, typically there is no adverse effect if corn contains under 200ppb aflatoxin but at 200 to 400ppb, reduced growth can occur and immune systems can be compromised, he said. At 400 to 800ppb, liver lesions can occur.

When feeding aflatoxin-infected corn to sows, there is typically no effect under 100ppb, Dr Tokach said. If levels are in the 500 to 750ppb range, pigs will grow more slowly due to aflatoxin in the sow’s milk. There does not appear, however, to be any effect on conception rates.

If feeding infected corn to nursery pigs, there is no effect if the aflatoxin is kept under 20ppb, he said.

"Producers who have high aflatoxin corn should use a binder, such as bentonite or aluminosilicate at 10 pounds per ton," Dr DeRouchey said. "Research shows that bentonite will bind up to 700ppb of aflatoxin. You do not need to add a binder to finishing diets, except last finisher situations, if levels are under 200ppb."

Even though research shows that higher levels of aflatoxin can be tolerated when bentonite is added to the diet, Food and Drug Administration regulations require that corn fed to young pigs contains less than 20ppb, for breeding animals less than 100ppb, and for finishing pigs, less than 200ppb. If the corn has greater than 200ppb, FDA rules indicate that it should be blended with other corn to lower the level to 200ppb or less before feeding. Blended corn must be used on-site and cannot be sold.

The swine specialists encouraged producers to use clean corn (i.e. less than 20ppb) for nursery and lactating sows and feed corn with over 20ppb aflatoxin to finishing pigs.

September 2011
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