Properly examined moldy feed can be used in beef diets with little risk

Tuesday, August 09, 2011

Mold does not pose risk to beef cattle, but the mycotoxins some molds can produce are frequently culprits in beef feeding operations.

That’s according to South Dakota Cooperative Extension Beef Specialist Cody Wright, who advises beef producers to analyze feed and get lab-tested information when it’s needed.

“Accumulation of mold and production of mycotoxins may present a risk for livestock producers, but with careful examination and analysis, moldy feeds may be able to be used in beef cattle diets with little or no risk,” Wright said. “Common molds frequently associated with mature corn ears including Fusarium or Gibberella, Penicillium, and Diplodia. A number of other fungi are only occasionally problematic such as Cladosporium and Aspergillus.”

Aspergillus is of the greatest concern to corn producers and livestock feeders. It is most commonly associated with drought, extreme heat, and insect injury. Aspergillus produces aflatoxin, a potent animal toxin that can be very problematic for livestock producers. This mold is generally light green or dark yellow and powdery in appearance.

A more common mold that poses a somewhat lower risk is the Fusarium/Gibberella complex, Wright said.  

“These molds range from white to pink or red in color and are associated with wet conditions and moderate temperatures,” Wright said. “They often are found in stalks and ears, especially during wet periods and following insect injury. The fungi can produce several mycotoxins including fumonisin, deoxynivalenol (DON or vomitoxin), and zearalenone.”

Wright said other molds pose much lower risks for toxin development. They include Diplodia, generally a white mold that begins forming at the base of the ear and grows toward the tip. It does not produce mycotoxins and is not a health risk to livestock, but can be confused with some of the Fusarium molds. Penicillium and Cladosporium molds are powdery or felt-like, range from dark blue-green to gray or black in color, and often grow between the husks and kernels or on injured areas of the ear. Cladosporium and Penicillium molds do not pose substantial risk to livestock.

Regardless of the feed being harvested, including dry or high-moisture grain, silage, earlage, or forage, Wright said it is a good idea to be aware of the mold risks in the feed source.

“Samples can be collected during the harvest and examined or analyzed for molds and mycotoxins, and sampling each load delivered would be an excellent protocol to ensure accurate representation across a given field,” said Wright. “Samples representing a field or storage unit might be mixed thoroughly to create a single, representative sample to be submitted for mycotoxin analysis.”

Approximately 5-10 pounds of grain are required for accurate analysis in the laboratory. Samples should be mailed in either cloth or paper sacks to prevent additional mold growth during shipment. Wright said that a thorough analysis can give beef producers the information they need to make proper judgments on feed. Recommended maximum total diet mycotoxin concentrations are as follows:

•    Aflatoxin: Should be kept at or below 300 parts per billion (ppb) in feedlot cattle, below 100 ppb for breeding beef cattle.
•    Fumonisin: Should be kept below 30 parts per million (ppm) in feedlot cattle and below 15 parts per million in breeding beef cattle.
•    Vomitoxin: Should be kept below 5 ppm in ruminating beef cattle
•    Zearelenone: Should be kept below 10 ppm in virgin heifers and below 20 ppm in mature cows.

Wright added that research suggests cattle can tolerate feeds with 50 ppm fumonisin and along with feeds that contain 20 ppm vomitoxin.

“If the results of the mycotoxin analysis indicate that the concentrations are below the maximum total diet concentrations, the grain can be fed without blending,” Wright said. “However, if the mycotoxin concentrations exceed the maximum total diet concentrations, then they must be blended with other feeds that have not been infected with mold to achieve total diet mycotoxin concentrations below the maximum concentrations.”

Wright said it is also important to note that mycotoxins may accumulate over time and the effects may not appear for several days to several weeks. “It is also possible that the presence of more than one mycotoxin may exacerbate the problems,” said Wright. “Mold and associated mycotoxins are often separated from the corn grain during the handling process. Consequently, it may be beneficial to analyze grains as they are removed from storage. Furthermore, grain screenings from mold-affected grains are likely very high in mycotoxins. Grain screenings should be thoroughly blended and analyzed for mycotoxin concentrations prior to feeding.”

A soon-to-be-published Extension Extra will provide information on rates of mycotoxins in beef diets. Ask for it at your county Extension office, or contact Wright directly at (605) 688-5448 or at