Survey of animal by-products in feedingstuffs before the reintroduction of processed animal proteins in aquafeed

Abstract

Description. Since 2001, the number of bovine spongiform encephalopathy cases has drastically declined. A gradual lifting of the feed ban for aquaculture was possible in 2013 but this partial relaxation makes its control much more complex. Objectives. The objective was to have a practical overview of the current analytical situation and to highlight current and foreseen analytical gaps in the context of a progressive lifting of the ban. Method. Feed samples, collected before the partial lifting as regards aquafeed in 2013, were firstly analyzed by light microscopy. All samples were additionally analyzed by PCR in order to study the difficulties which would be faced with feeds produced after the relaxation. ELISA for the detection of milk proteins was also performed on samples in which ruminant DNA was detected. Results. When keeping the interpretation to the sole light microscopy results, all samples were in accordance to the legal requirements. Adding the PCR results made the interpretation more difficult. DNA of terrestrial animals was detected in nearly 65% of the samples. Apart from aquafeeds, the presence of ruminant DNA could be explained by the use of dairy products confirmed in most cases by ELISA. In aquafeeds, 23% (13/57) of the samples tested positive for ruminant DNA but only three of them also tested positive for milk proteins. Conclusions. The study underlined the crucial need for complementary analytical solutions in order to identify the source of the detected DNA.