Early results from Countdown research indicate that a new milk molecular test could have an important role in testing for the presence of the mastitis bug, Streptococcus agalactia (Strep. ag.), in Australian dairy herds. It will be of particular use when sourcing cows for purchase.
The new test, known as a 'milk PCR', has been available in Australia for the past 12 months, through some milk companies, herd improvement centres and vets. The test uses, as an example, the routine milk vat sample collected by the tanker driver for BMCC analysis. In many instances it can be arranged through the company field staff or local vet.
Because there was limited knowledge of how this test performed when used on bulk vat milk under Australian conditions, Countdown examined its application in a research project with funding from the Gardiner Foundation.
Dr John Penry, who manages Dairy Australia's Countdown project, said the results suggest it should be a convenient surveillance tool for Strep. ag. mastitis, if the results are available prior to purchasing cows.
"The test is likely to be useful for managers of herds in an expansion phase who are unable to maintain a closed herd," he said.
"In this situation testing milk from the seller's herd before purchase will help assess the risk of importing Strep. ag. infected cows.
"The cost of the test is very small compared to the potential cost of importing cows infected with Strep. ag. and having it potentially spread to other cows in the herd," Dr Penry said.
Strep. ag. has long been a cause of mastitis in Australia dairy cows. Although it was believed to have become very uncommon, this bug is becoming more prevalent again.
It lives in the teat canal or milk collecting ducts of infected cows and spreads between cows during the milking process. It can spread quite rapidly within a herd, resulting in an elevated bulk milk cell count (BMCC).
The good news is that Strep. ag. is one of the few mastitis bacteria that can be eliminated from a herd using the correct control options.
"This test adds another mastitis control tool to our armoury. If cows, to be purchased are identified as coming from a strep. ag. positive herd, consult your adviser or vet to decide what steps can be taken to minimise your risk," Dr Penry said.
For more information, please visit Countdown 2020 mastitis guidelines.
Countdown is an example of your levy at work. For more information on this and other examples of your levy at work visit Dairy Australia.