Three farms positive for M. bovis in spring milk testing

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Only three farms have been confirmed through bulk milk testing as having Mycoplasma bovis - but the Ministry for Primary Industries says it is too early to speculate about final results.

The second bulk milk surveillance programme was being undertaken now as spring was the best time to test for the disease, the ministry said.

Infected animals were more likely to shed the bacteria after a stressful period, such as calving and the start of lactation.

To date, almost 10,000 of the country's 12,000 dairy farms had completed two rounds of testing, MPI said in an update.

The three properties confirmed through testing were already part of the MPI's tracing programme and all had previously known links with the disease. While that was very encouraging, it was still too early to speculate about the final results, the ministry said.

Calving on some farms was still a few weeks later than expected, so full milk test results for the large majority of farms were now expected to be delivered to farmers in early December, rather than November as previously forecast.

MPI said it expected about 2 per cent of farms would still be undergoing testing in early December and results were expected to be delivered to those farmers by mid-January.

In the meantime, MPI said it would contact farmers immediately if any suspicious results were found in a milk test.

DairyNZ said farmers were using a range of tactics, including due diligence, quarantine and virgin bulls, to keep cows and farms safe from the disease this mating season.

The disease, which was mainly spread through close physical contact with infected animals, made using bulls which had been exposed to other stock an added risk.

That had made some farmers think twice about continuing to use a combination of artificial insemination and bulls and consider extending AI to remove bulls completely, or reduce the number required.

DairyNZ response manager Hamish Hodgson said the best thing farmers could do to protect their herd and farm was to "do their homework''.

"Unfortunately, there isn't a silver bullet - there are pros and cons associated with both AI and bulls.''

While a lot of farmers had been considering adapting their usual approach, most were not making drastic changes, he said.