Fusarium graminearum (sexual state Gibberella zeae) growing in the ears of corn and on the heads of cereal grains before harvest may produce other toxins besides zearalenone. These include deoxynivalenol (DON), which makes the grain unpalatable to swine. Field-infected corn with visibly more than 5 percent damaged kernels is refused by pigs. Feed refusal may be accompanied by swollen vulvas and reproductive problems from zearalenone and DON in the same ration, and sometimes a complex of effects can occur. Swine producers often encounter serious problems when they attempt to make such corn palatable by applying molasses or other similar materials.
Wet, rainy, warm, and humid weather from flowering time on promotes infection of corn and cereals by Fusarium species, resulting in ear rot in corn and scab or head blight in wheat, barley, oats, and rye. Low temperatures following infection may increase the production of DON. The toxin already present in corn at harvest may increase in ear corn stored in cribs, as does zearalenone. Shelled grains free of the toxin at harvest have not been observed to develop either DON or zearalenone mycotoxins in storage.
Feeds that contain 1 ppm of DON may result in significant reductions in swine feed consumption and weight gain. Vomiting is rather uncommon in field cases because pigs usually will not eat enough of the contaminated feed.
In Illinois, cool, wet weather before and during the 1981 harvest of corn and small grains was followed by reports in late 1981 and 1982 of feed refusal and clinical signs of ill health in farrowing operations, feeder pigs, and breeding sows. DON was found in 80 percent of the nearly 400 samples taken, in concentrations of 0. 1 to 41.6 ppm. Zearalenone was found in 12 percent of the samples, at concentrations of 0. 1 to 8 ppm. Some samples contained both toxins. Clinical signs and lesions in affected swine included feed refusal, a few instances of vomiting, lack of weight gain, poor feed efficiency, failure of mature sows to return to estrus, reduced efficiency, high mortality of nursing pigs, intestinal tract inflammation, and acute diarrhea in young pigs.
Autopsies of young pigs revealed hemorrhaging into the abdominal cavities and pale, friable livers. In all cases investigated in detail, the problems were reduced or disappeared when the pigs were given sound feed. Dairy cattle and poultry are relatively insensitive to the dietary concentrations of DON likely to be found in feeds.