and prompt delivery (or freezing for delayed delivery) of the samples to the laboratory are very important steps to get right. The biggest problemthe laboratories have year-on-year is with contamination at the time of sampling. This can happen very easily and is usually the result of bacteria getting into the sample from the milker’s hands or from the skin on the teat or udder. It is also common when bulk tank samples are submitted as there are likely to be bacteria included from the cluster, milk line and bulk tank itself. When contamination happens, culture at the laboratory will result in the growth of a mixture of bacteria, and it is not easy for the laboratory technician to identify the ‘significant’ ones. The percentage of contaminated samples received by testing laboratories has been reducing year-on- year through the building of awareness on proper sampling technique. Many half-day farmer milk quality workshops have been organised in association with CellCheck. They have focused on a small number of areas identified as being key to achieving the most effect on improving milk quality. Identifying infected cows (using milk recording), infected quarters (using the California mastitis test (CMT)) and the preparation of the teat prior to quarter sampling for culture are three of the topics covered in the workshop. Management NoteA in theCellCheck ‘FarmGuidelines for Mastitis Control’ gives a clear list of steps to be taken when collecting milk samples for culture. Some farmers have a routine of collecting and freezing amilk sample from every cow that develops clinical mastitis. These samples can be stored and only submitted to the laboratory for culture if there is concern about a higher than expected mastitis rate within the herd. In such a situation the culture results may indicate a consistent cause and point the farmer towards the control measures that could achieve the best results.
Figure 1: Agar plate showing a growth of Staphylococcus aureus
Figure 2: Antimicrobial sensitivity plate showing sensitivity to five antimicrobials and resistance to one
CELLCHECK NEWSLETTER | JUNE EDITION 2018
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