Prior to giving specific information, some general concepts regarding the effect of mycotoxins on animals must be understood. The determination as to whether or not a given concentration of mycotoxin is safe will depend on at least the factors which follow (and there may also be other factors).

1. Chemical class and chemical structure of the mycotoxin in question. A partial list of known mycotoxins is shown in Table 1. The list includes mycotoxins from a number of chemical classes, each of which has different effects on the animals which consume them. However, the exact chemical structure of the mycotoxin involved is also vital. For example, aflatoxin B1 is reported to be the most potent naturally occurring carcinogenic substance known, but if just one chemical bond is changed in the structure of the molecule, its toxicity can be reduced dramatically.

2. Presence of other mycotoxins. A number of studies have demonstrated that mycotoxins occur simultaneously in field situations. This simultaneous occurrence can profoundly affect the toxicity of the mycotoxins present.

3. Species and strain of the animals involved. Ducklings are 5 to 15 times more sensitive to the effects of aflatoxin than are laying hens, but when laying hen strains are compared, certain strains of hens may be as much as 3 times more sensitive than other strains. This fact, along with the fact that there is continuous genetic improvement of farm animals, can mean that the exact sensitivity of a given animal to one or more mycotoxins is unknown.

4. Health status of the animals involved. Stress, physiological state, nutritional standing, and disease status will independently and collectively determine the response of a given animal to a specific mycotoxin level or complex of mycotoxins.

5. Criteria by which effects are determined. At a given dose, aflatoxin reduces weight gain in growing animals, but disease resistance in the same animal may be reduced by about half that dose.

6. Number of animals involved in judging the no effects level. It has been estimated that 400 groups of 10 broilers would be required to detect a 1 percent difference in growth rate. Yet, in integrated-poultry operations a 1 percent difference in growth rate would have a significant economic impact.

7. Sampling and assay procedures. It is imperative that sampling and assay procedures are accurate, since the results are the basis for deciding whether or not to use a given lot of feed or feed ingredient.

8. Length of time animals are exposed to the mycotoxin(s). The exact mycotoxin tolerance levels given elsewhere in this publication assume that animals are exposed for a limited period. Obviously, the risks of harm to animals from mycotoxins increase as exposure time increases.

           Table 1. A Partial List of Known Mycotoxins

    Aflatoxins            Fusaric Acid          Penicillic Acid
    Alternariol           Fusariocin            Penitrem
    Citreoviridin         Fusarins              Phomopsin
    Citrinin              Islanditoxin          Roridins
    Cyclopiazonic Acid    Luteoskyrin           Rubratoxin
    Deoxynivalenol        Moniliformin          Slaframine
    Diacetoxyscirpenol    Monoacetoxyscirpenol  Sporidesmin
    Dicoumarol            Neosolaniol           Stachbotryotoxins
    Ergotamine            Ochratoxins           Sterigmatocystin
    Ergo Toxins           Oosporein             T-2 Toxin
    Fumitremorgen         Paspalitrems          Tremorgens
    Fumonisins            Patulin               Zearalenone

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