Effect of roughage:concentrate ratio in the diet on systemic availability and excretion of ochratoxin A in sheep

Risks for animal health related to the presence of ochratoxin A (OTA) in feed

In 2004, the EFSA Panel on Contaminants in the Food Chain (CONTAM) adopted a Scientific Opinion on the risks to animal health and transfer from feed to food of animal origin related to the presence of ochratoxin A (OTA) in feed. The European Commission requested EFSA to assess newly available scientific information and to update the 2004 Scientific Opinion. OTA is produced by several fungi of the genera Aspergillus and Penicillium. In most animal species it is rapidly and extensively absorbed in the gastro-intestinal tract, binds strongly to plasma albumins and is mainly detoxified to ochratoxin alpha (OTalpha) by ruminal microbiota. In pigs, OTA has been found mainly in liver and kidney. Transfer of OTA from feed to milk in ruminants and donkeys as well as to eggs from poultry is confirmed but low. Overall, OTA impairs function and structure of kidneys and liver, causes immunosuppression and affects the zootechnical performance (e.g. body weight gain, feed/gain ratio, etc.), with monogastric species being more susceptible than ruminants because of limited detoxification to OTalpha. The CONTAM Panel considered as reference point (RP) for adverse animal health effects: for pigs and rabbits 0.01 mg OTA/kg feed, for chickens for fattening and hens 0.03 mg OTA/kg feed. A total of 9,184 analytical results on OTA in feed, expressed in dry matter, were available. Dietary exposure was assessed using different scenarios based on either model diets or compound feed (complete feed or complementary feed plus forage). Risk characterisation was made for the animals for which an RP could be identified. The CONTAM Panel considers that the risk related to OTA in feed for adverse health effects for pigs, chickens for fattening, hens and rabbits is low.

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.