80 | nzdairy DAIRY SERVICES » Franklin Vets Crucial to interpret results correctly Aimee Wilson Over the past three decades, the bulk milk somatic cell count (BMSCC) of the national dairy herd has dropped, from ~700,000cells/ ml to ~175,000cells/ml. The biggest drop was seen in the early 2000s and the BMSCC has plateaued over the past 10 years, short of the national target of 150,000cells/ ml. According to veterinary consultant David Hawkins of Franklin Vets, achieving industry targets is worth it for farmers. “But to get the next drop, farmers need to know where mastitis is coming from,” he said. ”Milk sampling for bacterial culture helps identify which bacteria are causing mastitis. We can then target control efforts most efficiently.” Mastitis bacteria can be classified in numerous ways. David finds it useful to group bacteria as follows: Milk sampling for bacterial culture helps identify which bacteria are causing mastitis, enabling more targeted control. 1 - Environmental. Bacteria that live in the environment and cause mastitis when the udder becomes contaminated with mud, faecal matter or dirty water. Streptococcus uberis is the most common environmental cause of mastitis, but vets are also seeing more coliform infections as farm systems intensify. High rates of clinical mastitis are often seen with these infections. 2. Contagious. Bacteria that prefer to live in the udder and spread from cow to cow during milking. Staphylococcus aureus is the most common contagious cause of mastitis in New Zealand. While it is difficult to cure during the lactation, infections may be effectively treated by dry-cow therapy. 3. Commensal Bacteria. Bacteria that live on the cow’s skin and spread during the milking process from the skin to the udder, or from cow to cow. Mostly they cause mild to moderate mastitis, but some cases can be difficult to deal with. They are often associated with high somatic cell counts and can be controlled by effective teat-spray application. David says, “Understanding where the bacteria are coming from can avoid putting a lot of effort into things that aren’t making a difference.” There are a range of different testing options that help farmers identify where the bacteria causing mastitis are coming from. These include on-farm tests such as the Mastatest®, and off-farm options such as microbiology labs. A number of companies also provide milk sampling and culture services to identify which bacteria are infecting which cows. To interpret results correctly, David strongly “The generic reporting of some tests means interpretation of results can be oversimplified. As a result, major decisions such as culling, may not always be made correctly.” 0800 821 421 advises farmers contact their local vet clinic. “The generic reporting of some tests means interpretation of results can be oversimplified. As a result, major decisions such as culling, may not always be made correctly. Cell count data is valuable and should be used with bacteriological data when determining outcomes for cows.” Reducing cell counts and mastitis rates in cows to industry targets is worthwhile. Reductions require farmers to understand where bacteria causing mastitis are coming from. Fortunately, there are plenty of options available to help farmers with this. Correct interpretation of results from these options is paramount for good outcomes and your local veterinarian is happy to assist.
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