The unusually wet weather experienced in many areas this fall not only put corn harvest way behind, but it provided ideal conditions for mold, and mycotoxins, to appear in corn—a potential headache for pork producers using the new-crop grain in swine rations.
Although mold itself found in grain does not cause problems for livestock, pigs can be very sensitive to the mycotoxins that molds can produce. In these cases, pigs may refuse to eat the affected feed, but often the symptoms may go unnoticed even as pig performance declines.
According to Bob Thaler, South Dakota Cooperative Extension swine specialist, the unpredictable nature of mycotoxins make it essential to know exactly how much is in the grain for any ratio formula to work. It’s also why producers should keep a close eye on the quality of corn, whether they harvest it themselves or purchase it.
Thaler says the mycotoxins to watch for include aflatoxin, zearalenone, vomitoxin (also known as DON), fumonosins and T2.
“We recommend that you take samples from several locations in the bin or load, and send them to a certified lab for analysis. Your county Extension educator can provide more information about proper sampling and where to send it.”
Know what you’re dealing with. To help make sense of the lab results, watch for the following mycotoxins:
- Vomitoxin. Gibberella ear rot fungus produces the mycotoxin called deoxynivalenol (DON), also known as vomitoxin. Vomitoxin does not cause health or reproductive problems, but when the total concentration in the diet reaches 1 ppm, pigs will eat less feed, Thaler says. “This decrease in feed intake will result in slower gains, but not death.” You can easily tell if there’s a problem with vomitoxins, because pigs will vomit and some may experience diarrhea, in addition to eating less feed, adds Hans Stein, swine nutrition specialist at the University of Illinois Extension. “If you have to feed grain with vomitoxin in it, mix it up as best you can so levels in the final diet are a maximum of 1 ppm in the final diet,” he says.
- Zearalenone. In contrast to vomitoxin, the mycotoxin Zearalenone has estrogen-like effects that tend to cause problems in the breeding herd. It can cause a number of health issues, from swollen vulvas to reduced birth weights, says Stein, who notes that Zearalenone seems to be less detrimental in grow-finish pigs. “If you have to feed it, try to get it into the diet of grow-finish pigs, and try to keep it out of the diet of the breeding herd and developing gilts."
- Ochratoxin. This mycotoxin is a concern in swine diets. Reduced performance has been reported with levels as low as 1.4 ppm, and high levels are toxic. Feed no more than 1 ppm of ochratoxin in the final diet, Stein says.
T2 toxin. Particularly in the diets of young pigs, T2 is very toxic and reduces feed intake and average daily gain. This mycotoxin also reduces the immune function of these pigs, says Stein, who recommends no more than 0.5 ppm of T2 in the final diet.
Fumonisin. Quite of bit of fumonisin has appeared in corn this fall. Don’t feed more than 10 ppm, Stein says. “If you are above this level, you need to blend it down.”
Diplodia. While the University of Illinois has received many calls about diplodia this fall, diplodia is not toxic and can be fed to pigs with no detrimental effects. “There are some reports that feed intake may go down a little when you feed diplodia corn, however,” Stein says. “Watch this, and try to blend it up as much as you can.”
Aflatoxin. This is the only mycotoxin regulated by the U.S. Food and Drug Administration. No more than 20 ppb of aflatoxin is allowed for interstate shipment of contaminated grain. At low levels (20 to 200 ppb), aflatoxin often decreases feed intake, depresses growth rate and can suppress the pig’s immune function.
Other Mycotoxin Rules of Thumb
Some products promise to “bind” mycotoxins in grain, but they’re not universal in scope. Thaler says, “Some bind aflatoxin, but they are not very effective in tying up DON or zearalenone. So, if you want to use DON- or zearalenone-contaminated grain, you’ll need to blend it with ‘clean’ grain to keep those levels in the complete feed below 1 ppm.”