Towards a quantitative application of real-time PCR technique for fish DNA detection in feedstuffs

A real-time PCR method to detect fish DNA in feedstuffs was developed and optimised. A combination of primers and a Taqman-MGB probe was used to selectively amplify the fish mitochondrial 12S ribosomal RNA gene. Qualitative and also quantitative assessments were performed with different protocols: a relative quantification by a standard curve, and a ΔCT method, by total plant DNA as endogenous controls. Method specificity was evaluated analysing 40 different tissues (mammalians, avian, fish) and flour samples. Sensitivity was evaluated by LOD (limit of detection) estimation. The designed probe–primers set showed an increased sensitivity compared to previously published PCR end point method, reaching a limit of detection of 0.2 pg of fish DNA, and showing to be a robust assay for fish DNA detection. The quantification results, based on ΔCT method and the relative standard curve, are well reproducible in our experimental condition but, in lacking of separate pure raw materials of a tested feed, they cannot be applied for reliable and precise quantification on field samples but for now as a semi-quantitative PCR method only.