Over 10% of milk samples, sent by farmers to Regional Veterinary Laboratories to check for mastitis, are contaminated on farm and could not give definite answers to the cause of bacteria.

Some 11.8% of over 3,000 milk samples received in 2013 by the Regional Veterinary Laboratory’s (RVLs) were considered to be contaminated, Alan Johnson, Senior Research Officer at the RVL in Limerick, says in the AHI newsletter.

“The biggest problem the laboratories have year-on-year is with contamination at the time of sampling,” Alan says.

Alan says that this can happen very easily and that it is usually a result of bacteria getting into the sample from the milkers’ hands or from the skin of the teat or udder.

It is also common when bulk tank samples are submitted there are likely to be bacteria included from the cluster, milk line and bulk tank itself, Alan says.

“When this happens culture at the laboratory will result in the growth of a mixture of bacteria and it is not possible for the laboratory technician to identify the ‘significant’ ones,” Alan says.

According to the Senior Research Officer this percentage is reducing year on year through the building of awareness on proper sampling technique.

“Culturing milk samples costs money so it is important to get the maximum possible value for the effort put in.

“Care taken in the sampling process, refrigeration and prompt delivery (or freezing in the event of delayed delivery) of the samples to the laboratory are important steps to get right,” Alan explains.

Milk culturing can be used as part of a mastitis control programme and bacterial infection is responsible for virtually all cases of mastitis therefore by identifying the agent responsible the farmer can have important information about the possible source of the infection, Animal Health Ireland (AHI) says.

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