Three thawing methods, milk somatic cell separation technique and SDS phenol method were used to separate and extract bovine genomic DNA from milk samples preserved at -80℃. The concentration and purity of the extracted DNA were measured by the ultra low volume spectrometer, and molecular weight of DNA was obtained by agarose gel electrophoresis. The DNA quality was further identified by PCR to amplify specific bovine gene fragment. The results showed that DNA obtained from the two-step thawing method was better in quality than that from the one-step thawing method and three-step thawing method. The concentration and purity of the DNA from the two-step method were (52.46±2.40) μg/mL and 1.85±0.80, respectively. The specific bovine gene fragment (729 bp) could be successfully amplified, and the strip on gel image was clear. This study established a novel bovine genomic DNA extraction method from milk preserved at ultra-low temperature, by optimizing method for thawing frozen milk.

milk; thawing method; DNA extraction; PCR