Risk assessment of mycotoxins in ruminants and ruminant products

Mycotoxins are secondary metabolites produced by several fungi, more specifically those of the genera Aspergillus, Fusarium and Penicillium. They were discovered in the early 1960s, when more than 100,000 young turkeys died in the United Kingdom from an apparently new disease, which was named "turkey × disease". The toxin-producing fungus was identified as A. flavus and the toxin was given the name aflatoxin by virtue of its origin. Forages, cereals and protein sources such as peanuts and cottonseed are potential mycotoxin vectors in ruminant diets. New techniques for preserving wet forages, such as silages or wrapped bales, are unsafe when anaerobic conditions are not strictly controlled. Fresh grasses can also be contaminated with mycotoxins including fungal endophytes that produce toxins such as ergovaline, lolitrem B, peramins and swainsonine. It is generally considered that ruminants are less sensitive to mycotoxins than other animals. This may be due to the capacity of the ruminal microbial ecosystem to degrade or convert mycotoxins into less toxic compounds. However, there is some evidence that ruminants can be poisoned by mycotoxins, causing lower animal production or even death of animals. Part of mycotoxins ingested by ruminants can be recovered in milk or animal tissues, either in the parent form or as metabolites. The transfer rate, usually very low, is estimated at less than 1% for the major toxins. Thus animals are considered as "filters" of mycotoxins in the food chain. However, there is a risk for infants fed only on a milk diet of being exposed to mycotoxin levels that exceed the regulated limits. Although not currently authorised in Europe, some mycotoxin inactivators, based on sequestering or degrading properties, have been tested in vitro and in vivo. The mode of action of yeast く-Dglucans against mycotoxins is presented, together with measures to limit the level of feed contamination by mycotoxins.