Detection of dog and cat traces in food, pet food and farm animal feed by real-time PCR

The identification of species presents in food is important due to many reasons. Some of them are economic fraud and/or sanitary problems, which could arise from inaccurate identifications of the composition of food products. Adulteration of processed meat generally occurs when there is a considerable price differential between raw materials from different species. Also, it occurs too when trying to introduce raw material of dubious origin, or even raw materials prohibited in some countries for cultural reasons. For example, dog traces were discovered in pet food in Spain in early 2013. This work describes development and validation of two real-time PCR methods, one for dog detection and other one for cat in foodstuffs. The method is based on specific primers/TaqMan probe sets that amplify a fragment of the Cytochrome oxidase subunit I sequences. TaqMan probes allow rapid and accurate assessment of even very small quantities of contaminants, even in thermally treated products. The detection limit was 2 and 0.2 pg of the target DNA from dog and cat, respectively. The methodology was validated to check how the degree of food processing affects the applicability of this technique. Additionally, a total of 100 samples from pet food, farm animal products and raw material were analyzed to apply the developed methodology to commercial samples. Possible applications of these methods are as process control, food security, traceability verification in commercial trade and the correct application of food labelling regulations. In conclusion, the real-time PCR methodology described herein represents a useful tool for the detection of dog and cat traces in all kind of products, including processed products that have undergone aggressive treatments (canned meals and feeds).