Toxicological evaluation of trichothecenes in animal feed

Abstract

Trichothecenes are mycotoxins commonly found in cereals world-wide. Fusarium fungi are the main producers of trichothecenes in cereals. Trichothecenes are rapidly excreted from animals and residues of trichothecenes in animal-derived food products are not considered to pose any threat to consumers. The toxins are toxic to all tested species, but the sensitivity varies considerably between toxins and between species. Available feeding studies with the trichothecenes deoxynivalenol (DON), nivalenol (NIV) and T-2 toxin in feed to production animals have been reviewed. There are not sufficient available data about the effects of trichothecenes in ruminant feed to allow a scientifically-based risk assessment. The available studies of the metabolism of trichothecenes in cattle indicate that trichothecenes to a large extent are transformed to the much less toxic de-epoxide metabolite in the rumen before absorption. Furthermore, no effect has been found on milk production, feed intake or other parameters measured at levels used in the studies. It is concluded that trichothecenes are not likely to cause any harm in ruminants unless fed visibly damaged feed and no guideline value is probably needed. Poultry are more sensitive to trichothecenes than ruminants. Levels from 9 mg DON/kg feed have lead to negative effects of chickens, while no effect was found in chicken fed 5 mg DON/kg feed, and a guideline value of 2.5 mg DON/kg feed is proposed. The available information about NIV does not allow a guideline limit to be set, but the finding of minor pathological changes in chicken fed 1 mg NIV/kg feed indicates that NIV may be more toxic to poultry than DON. Oral lesions are observed in chickens and hens fed 1 mg T-2 toxin/kg feed. Other effects, including a reduction in feed intake, are found with increasing levels of T-2 toxin. A guideline limit of 0.5 mg T-2 toxin/kg is proposed. Pigs are more sensitive to trichothecenes than other farm animals. The effects occurring at the lowest levels of trichothecenes are reduced feed intake and weight gain, normally occurring at levels from 0.6 mg DON/kg feed in naturally contaminated feed. Pigs fed 0.5 mg T-2 toxin/kg feed reduced their feed intake. Impairment of the immune system has also been observed in pigs at this level of T-2 toxin in the feed. Guidelines of 0.3 mg DON/kg feed and 0.2 mg T-2 toxin/kg feed is proposed in pig feed.