The effect of a cannula milk sampling technique on the microbiological diagnosis of bovine mastitis.

Two methods of collecting milk samples from mastitic bovine mammary quarters were compared. Samples were taken in a consistent order in which standard aseptic technique sampling was done first, followed by insertion of a sterile cannula through the teat canal and collection of a second sample. Microbiological results of those two sampling techniques were compared. Milk samples were analysed using multiplex real-time polymerase chain reaction (PCR). The cannula technique produced a reduced number of microbial species or groups of species per sample compared with conventional sampling. Staphylococcus spp. were the most common species identified and were detected more often during conventional sampling than with cannula sampling. Staphylococcus spp. identified in milk samples could also have originated from the teat canal without being present in the milk. The number of samples positive for Trueperella pyogenes or yeasts in the conventional samples was twice as high as in the cannula samples, indicating that the presence of Trueperella pyogenes and yeast species should not necessarily be interpreted as being the causative agents of bovine intra-mammary infections (IMI).