Fusarium Head Blight (FHB) is a fungal disease of various grasses. It is found most often in wheat but can also affect barley, oats, rye and some forage grasses. Under certain environmental conditions, the fusarium mould may produce a mycotoxin called DON (deoxynivalenol). DON is a mild toxin compared to other toxins which canform in grains and forages. Reduced feed intake, and the accompanying decrease in performance, are the only symptoms of DON toxicity livestock producers will likely encounter.
This response to DON appears to occur through the central nervous system. DON belongs to a class of mycotoxins (tricothecenes) which are strong protein inhibitors. Inhibition of protein synthesis following exposure to DON causes the brain to increase its uptake of the amino acid tryptophan and, in turn, its synthesis of serotonin. Increased levels of serotonin are believed to be responsible for the anorexic effects of DON and other tricothecenes. Irritation of the gastrointestinal tract may also play a role in reducing feed intake.
Because DON functions as a protein inhibitor, it may also reduce the production of antibodies by the immune system and increase an animal’s susceptibility to disease.
Different livestock species respond differently to DON. In pigs, DON is efficiently absorbed, poorly metabolized, widely distributed through body tissues and excreted at a comparatively slower rate than in other farm species. This makes pigs quite susceptible to the effects of DON. With ruminants and poultry though, DON has been shown to be poorly absorbed, extensively metabolized, and rapidly cleared from tissues and fluids.
The effects of DON on different livestock species and the Agriculture Canada guidelines for DON intake are discussed below.