Metabolism and excretion of ochratoxin A fed to sheep.

Abstract

Hydrolysis of the mycotoxin ochratoxin A (OA) to ochratoxin alpha (Oalpha) by microorganisms within the gastrointestinal tract leads to the excretion of OA as the nontoxic alpha form. The Oalpha form is the principal means for the detoxification of OA. In the current experiment, three groups of four sheep were fed diets consisting of 70% concentrates and 30% hay (dry matter basis, energy to supply 1.1 times the requirement for maintenance) for 4 wk with three dietary concentrations of OA (0, 2, or 5 mg/kg of concentrate feed). The OA content did not affect feed intake or nutrient digestibility. In a preliminary experiment, an OA dose of 20 mg/kg of concentrate feed greatly reduced feed intake. After 1, 2, 3, and 4 wk of the trial, significant concentrations of OA were detected in the serum of the animals fed 2 or 5 mg of OA/kg feed. This suggested that even at a dosage of 2 mg of OA/kg of concentrate feed, considerable amounts of OA were not degraded by ruminal and intestinal microorganisms. The analysis of the feces and urine samples reflected these findings; OA and Oalpha were found in significant concentrations, escaping fermentation in the rumen and in the hindgut. The current experiment demonstrates that OA hydrolysis in the gastrointestinal tract of sheep is substantially less than previously described, especially if OA is ingested in combination with concentrate-rich diets.

Ochratoxin A in Ruminants–A Review on Its Degradation by Gut Microbes and Effects on Animals

“…However, other studies found no ( in vivo , [10]) or only slight indications ( in vitro , [121]) for a negative influence of OTA on digestibility. Using four toxin concentrations of 5.0, 20.0, 200 and 1,400 μg/L of incubation medium, a significant decrease of in vitro digestibility was found only at the highest concentration [122].…”

“…Clear signs of discomfort and starting intoxification (polyuria, reduced feed intake) are first reported at repeated doses of 225 μg/kg bw [10] or at a single dose of 500 μg/kg bw (polyuria; [73]) for sheep. At a single, but very high dose of 13,300 μg/kg bw a cow showed severe clinical signs like difficulties in arising, diarrhoea, anorexia and cessation of milk production, the latter only recovering to one third of normal during this lactation [126].…”

“…In fact, based on improved and more sophisticated analytical methodology and equipment, some more recent evidence is available that the effect of OTA on ruminants in this respect is generally underestimated. At concentrations described to be safe, OTA occurs systemically in significant amounts [10,11,105]. Therefore, although no obvious pathological effects occur, the common view that OTA is degraded completely by an active rumen microbial population under all circumstances does not hold true.…”

“…However, recently some doubts and discrepancies have been raised to what extent and in which amounts OTA is sufficiently detoxified by ruminants under all feeding regimes/circumstances [10,11]. It is not clear to what extent particular microbial groups like protozoa contribute to OTA degradation and factors like the degree of contamination of typical feedstuffs need to be quantified.…”

Presencia de hongos y contaminación con micotoxinas en ensilajes para alimentación de rumiantes. Artículo de Revisión

“…Por este motivo, la aparición clínica de toxicosis en esta especie es poco frecuente (Battacone et al 2010). La excreción se da generalmente por orina y heces (Höhler et al 1999), y la excreción por orina de ocratoxina alfa se socia principalmente a la recirculación entero hepática. Debido al metabolismo de la ocratoxina en el rumen, su excreción en leche es muy poca, al igual que el paso a través de la barrera placentaria.…”