Does gastrointestinal digestion affect low level thiouracil residues upon Brassicaceae derived food and feed consumption?

In recent years, endogenous formation of thiouracil (TU) has been reported in the urine of livestock upon consumption of glucosinolate-rich crops, belonging to the Brassicaceae (Pinel et al., 2006). This has been a staggering discovery, since the European Union in 1981 banned the use of thyreostatic drugs for fattening purposes in livestock. Previously, TU has been demonstrated in various Brassicaceae-derived foods and feeds (<1.0 µg kg-1 - 5.98 µg kg-1) upon myrosinase addition (Vanden Bussche et al., 2011). The impact of bacterial myrosinase produced during digestion has however not been evaluated before in relation to TU production in livestock. Therefore, during this study in vitro bovine and porcine digestive simulations of various Brassicaceae-derived foods and feeds were performed. Derivatization and LC-MS2 analysis of the digestive samples resulted in the detection of TU in the large intestine and the rumen for various Brassicaceae matrices. In stomach and small intestinal digestive fluids, however, TU remained unfound. The influence of autoclavation on the inoculum and the feed was compared to a control, resulting in a significantly minor TU yield for the autoclaved inoculum (p<0.05). In conclusion, these results confirm the active involvement of intestinal microbiota in TU formation during gastro-intestinal digestion of Brassicaceae-derived feed, thus demonstrating plant-myrosinase is not the only possible mediator.

ISBN:9789461733184

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