By Travis Peardon, Regional Livestock Specialist, Outlook
When it comes to feeding grain to livestock, the concern is not necessarily about Fusarium; the issue is with the mycotoxins that F. graminearum may produce. This particular species produces a number of mycotoxins, including zearalenones and trichothecenes. Zearalenone is a compound similar to estrogen. Its presence in feed can disrupt the estrus cycle. It has been associated with early embryonic death in some cases.
Trichothecenes are comprised of several metabolites, including deoxynivalenol (DON or vomitoxin), diacetoxyscirpenol (DAS), T2 toxin and HT2 toxin. By far, DON is the toxin most commonly produced. In fact, the industry uses DON as a marker. It is an indicator that other toxins may be present. DON is a relatively mild toxin. Animals consuming feed containing high levels of DON may have a reduced immune response. Feed refusal is common. DON is found in the infected grain and chaff covering that grain. Little, if any, is found in the straw and leaves of the plant. Studies have shown that DON is rapidly metabolized in the body. DON does not accumulate in meat, milk or eggs. Tissue residues are not a concern. DON is not carcinogenic.
Agriculture and AgriFood Canada has regulatory guidelines for maximum tolerated levels of DON in livestock diets. Rations for beef cattle and poultry may contain up to 5 parts per million (ppm) DON or 5,000 parts per billion (ppb). Diets for swine, young calves and lactating dairy animals may contain up to 1 ppm or 1,000 ppb DON.
If a mature beef cow was fed five lbs of grain that contained 20 ppm DON and 30 lbs of hay and other forage, the cow would be eating a total of 2.8 ppm DON (total diet) which is well within the regulatory guidelines.
Keep in mind that other factors come into play: poor health, stress, inadequate feeding programs, over-crowding and other things may make animals more susceptible to the effects of DON. As was mentioned, other mycotoxins may be present. The effects of the mycotoxins are, at least, additive, and some may act in a synergistic manner.
If Fusarium-contaminated grain is going to be fed to livestock, it is advisable to have it tested at a feed testing laboratory for the presence of mycotoxins. A number of labs, elevators, terminals and pelleted feed companies are using ELISA (enzyme-linked immunosorbent assays) tests to measure DON levels in suspect grain samples. This technology is relatively inexpensive, quick and accurate. It does not detect the presence of other mycotoxins when using the test strip for DON. For example, HT2 can be present at high levels in infected grain with no DON in the sample. It is recommended to have a complete mycotoxin panel screen performed, as other mycotoxins may be present.
For complete mycotoxin analyses, producers should contact one of the labs on our Water Testing and Feed Laboratories page.
For more information, please contact your nearest Saskatchewan Agriculture Regional Office or the Agriculture Knowledge Centre at 1-866-457-2377.