r. 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 Cody.Wright@sdstate.edu.