Ochratoxin A in ruminants−A review on its degradation by gut microbes and effects on animals

Ruminants are much less sensitive to ochratoxin A (OTA) than non-ruminants. The ruminal microbes, with protozoa being a central group, degrade the mycotoxin extensively, with disappearance half lives of 0.6–3.8 h. However, in some studies OTA was detected systemically when using sensitive analytical methods, probably due to some rumen bypass at proportions of estimated 2–6.5% of dosage (maximum 10%). High concentrate proportions and high feeding levels are dietary factors promoting the likeliness of systemic occurrence due to factors like shifts in microbial population and higher contamination potential. Among risk scenarios for ruminants, chronic intoxication represents the most relevant.

Effects of live yeast cell supplementation to high concentrate diets on the toxicokinetics of ochratoxin A in sheep

Previous studies have indicated that high concentrate feeding reduces the ruminal degradation of the mycotoxin ochratoxin A (OA) to the less-toxic ochratoxin alpha (Oalpha) in ruminants. This is due to a pH-induced decrease in ruminal protozoa and subsequent increasing transfer of OA into the systemic circulation. The present study investigated whether stabilization of rumen pH by the live yeast cell supplementation to high concentrate diets affects the toxicokinetics of OA in sheep. Sheep were fed diets consisting of 70% concentrates and 30% grass silage (dry matter basis) supplemented without or with live yeast cells (Saccharomyces cerevisiae CNCM I-1077). After an adaptation period of 3 weeks, animals were given a single dose of OA (2.46 mg) in the form of contaminated wheat. Even though live yeast cells accelerated the recovery of ruminal pH from the decrease in pH induced by feeding, no effect on ruminal degradability and systemic availability of OA was recorded. Based on in vitro studies, live yeast cells and extracts of live yeast cell walls have been suggested as a mycotoxin-binding agent. However, supplementation with live yeast cells had no effect on the excretion pattern of OA in sheep, indicating that binding of OA to yeast components may be limited in ruminants. With respect to the toxicokinetics of OA, our results are in agreement with earlier results demonstrating that the hydrolysis of OA in the gastrointestinal tract of sheep is substantially less than previously described, especially if OA is ingested in combination with concentrate-rich diets. Our study demonstrates that feeding a live yeast cells product, registered as a feed additive for improving zootechnical performance, had no impact on the toxicokinetics of OA under the chosen conditions.

Alkalinization of urinary pH accelerates renal excretion of ochratoxin A in pigs

The mycotoxin ochratoxin A (OA) is a cause of endemic nephropathy in farm animals and humans. Reabsorption of OA along the nephron results from nonionic diffusion and by carrier-mediated mechanisms, indicating that urine alkalinization may help to accelerate OA excretion and thus reduce its toxicity. The aim of the present study was to investigate the effect of a dietary sodium bicarbonate supplementation as a means of increasing urinary pH on the systemic availability and excretion of OA in pigs. Dietary supplementation of 2% sodium bicarbonate significantly increased urinary pH (5.7 +/- 0.2 to 8.3 +/- 0.1) and daily urine volume (1108 +/- 276 to 2479 +/- 912 mL). The systemic availability of OA and its dechloro-analog, Ochratoxin B (OB), calculated as the area under the curve (AUC) was reduced to 75 and 68%, respectively, of the control group (P < 0.05). This effect was due mainly to an accelerated elimination of OA and OB in the urine. The faster renal elimination may be due to reduced reabsorption of the ochratoxins by nonionic diffusion, and other H(+)-dependent mechanisms. Thus, urinary alkalinization may be an efficient means to partially reduce the toxic effects of OA in pigs.