Less is More--Optimization of DNA Extraction from Canine Feces

Although most DNA crime laboratories may not encounter fecal samples often, they are a familiar sample type in non-human forensic laboratories due to their prevalence in the environment. Fecal matter can be challenging due to low numbers of nucleated cells and the presence of inhibitors that impede amplification success. Sampling location (internal vs. external), sampling quantity (10-200 mg), and various extraction protocols (silica matrix, bead beating, and clean-up column) were evaluated to maximize DNA yield. The greatest yield of intact DNA was obtained using a modified silica matrix extraction protocol (VGL-Fecal) on 30-50 mg of fecal matter collected from the external surface of a stool that had been dried for 24 h. This optimized sampling and extraction protocol was applied to a pilot study where DNA yield and genotyping success were evaluated. By optimizing our collection, sampling, and extraction procedures, a reliable method for maximizing the yield of canine fecal DNA was developed.