Mycotoxin Contamination of Corn – Impact on Swine

October 12, 2011 — 

Mycotoxins in corn are produced by certain molds which infect the ears of corn. Molds may be present without the production of mycotoxins, but mycotoxins cannot be produced in the absence of molds. The mycotoxins of greatest interest to pork producers are aflatoxin, deoxynivalenol (also known as vomitoxin or DON), fumonisin, zearalenone and occasionally ochratoxin and T-2 toxin. A number of ear rots are capable of producing mycotoxin-producing molds. These include Fusarium Ear Rot, Gibberella Ear Rot and Aspergillus Ear Rot. Diplodia Ear Rot is common in Iowa, but so far, it has not been observed to cause formation of mycotoxins. The various ear rots are favored by different environmental conditions, so each may occur in different years.

While weather conditions are an important contributor to mold infection, producers do have some control over the extent of infection that might occur. For example, insect control in corn will help to prevent damage to kernels that encourage mold growth. Screening corn to remove broken or otherwise damaged kernels and storing corn at 14% moisture or less will also discourage mold growth. Cleaning grain storage by removing old grain before new crop corn is added will help to avoid contamination from one year to the next.

Aflatoxin is perhaps the mycotoxin of greatest concern because it represents a risk to human as well as animal health. Because aflatoxin can accumulate in the meat, this is a public health issue that cannot be ignored. Feed for market pigs cannot contain more than 20 parts per billion (ppb) of aflatoxin, in order to remove risk to the final pork product.

Vomitoxin, or DON (deoxynivalenol,) causes reduced feed intake and weight gain when present in the feed at 1-3 parts per million (ppm), with younger pigs being most susceptible. Cattle and poultry can tolerate much higher levels of DON than pigs. DON is often found in association with another mycotoxin, zearalenone, because both are produced by the same mold.

Fumonisins comprise a family of mycotoxins to which horses and donkeys are most susceptible. For pigs, feed levels of total fumonisins below 10 ppm are recommended.

Ochratoxin affects the kidney first, but also can attack other tissues and organs as well. Feed levels below 0.2 ppm are recommended for swine to protect their health.

T-2 toxin is less common than DON, but more toxic, causing feed refusal, vomiting and damage to the gut. In some cases, it can be fatal. For pigs, levels of T-2 toxin in the feed below 2 ppm are recommended.

Finally, zearalenone is an estrogenic toxin meaning it mimics the effects of estrogen, leading to infertility, pseudopregnancy and prolapse. Levels should be kept below 1 ppm for piglets and 3 ppm for growing pigs.

Source: ISU swine nutrition specialist John Patience and clinician Steve Ensley with ISU’s Veterinary Diagnostic and Production Animal Medicine department. Available for download at no charge from the IPIC website http://www.ipic.iastate.edu/publications/IPIC12.pdf