Metabolism of aflatoxin, ochratoxin, zearalenone, and three trichothecenes by intact rumen fluid, rumen protozoa, and rumen bacteria

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Abstract
The effect of rumen microbes on 6 mycotoxins (aflatoxin B1, ochratoxin Az, zearalenone, T-2 toxin, diacetoxyscirpenol and deoxynivalenol) considered to be health risks for domestic animals was investigated. The myocotoxins were incubated with intact rumen fluid or fractions of rumen protozoa and bacteria from sheep and cattle in the presence or absence of milled feed. Rumen fluid had no effect on aflatoxin B1 and deoxynivalenol. The remaining 4 mycotoxins were all metabolized; protozoa were more active than bacteria. Metabolism of ochratoxin A, azearalenone and diacetoxyscirpenol was moderately or slightly inhibited by addition of milled feed in vitro. The capacity of rumen fluid to degrade ochratoxin A decreased after feeding, but this activity was gradually restored by the next feeding time. Ochratoxin A was cleaved to ochratoxin .alpha. and phenylalanine; zearalenone was reduced to .alpha.-zearalenol and to a lesser degree to .beta.-zearalenol; diacetoxyscirpenol and T-2 toxin were deacetylated to monoacetoxyscirpenol and HT-2 toxin, respectively. Feeding of 5 ppm (5 mg/kg) of ochratoxin A to sheep revealed 14 ppb (14 ng/ml) of ochratoxin A and ochratoxin .alpha. in rumen fluid after 1 h; neither was detected in blood. Whether such conversions in the rumen fluid may be considered as a 1st line of defense against toxic compounds present in the diet is briefly discussed.