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

TLDR

Whether rumen fluid conversions can serve as a first line of defense against dietary toxins is briefly discussed. The study investigated how rumen microbes affect six mycotoxins (aflatoxin B1, ochratoxin A, zearalenone, T‑2 toxin, diacetoxyscirpenol, and deoxynivalenol) that pose health risks to domestic animals. Mycotoxins were incubated with intact rumen fluid or with isolated rumen protozoa and bacteria from sheep and cattle, with or without milled feed. Rumen fluid did not alter aflatoxin B1 or deoxynivalenol, but metabolized the other four toxins—ochratoxin A, zearalenone, diacetoxyscirpenol, and T‑2 toxin—with protozoa more active than bacteria; feed addition slightly inhibited metabolism of OTA, ZEA, and DAS, and OTA was rapidly degraded to OTA‑α and phenylalanine in vitro and detected only in rumen fluid, not in blood, after in vivo feeding.

Abstract

The effect of rumen microbes on six mycotoxins (aflatoxin B1, ochratoxin A, zearalenone, T-2 toxin, diacetoxyscirpenol, and deoxynivalenol ) considered to be health risks for domestic animals was investigated. The mycotoxins 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 four mycotoxins were all metabolized, and protozoa were more active than bacteria. Metabolism of ochratoxin A, zearalenone, 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. Ochromatoxin 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, but neither was detected in the blood. Whether such conversions in the rumen fluid may be considered as a first line of defense against toxic compounds present in the diet is briefly discussed.