Two further properties in Waimate and Southland have been confirmed with Mycoplasma bovis, bringing the total number to 20.

The number of properties under restricted place notice, which effectively placed them in quarantine, has risen to 35.

There are now six farms confirmed with the bacterial cattle disease in Southland, 11 in the Waitaki/Waimate districts, two in Mid Canterbury and one in Hawke's Bay.

About 5000 cattle were culled last year from properties in the Waimate district to prevent further spread of the disease.

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That operation was completed at the end of December and the Ministry for Primary Industries has deferred a decision on the need for further whole-herd culling until a more thorough picture of the disease's distribution in New Zealand was built.

MPI said a nationwide dairy surveillance programme would help inform those decisions in future.

Three samples of milk from every dairy farm would be tested, starting this week. Results would be back in February and March. Individual animals and small groups were still being culled for sampling.

This week's NZ Dairy Event at Manfeild Park, near Palmerston North, has gone ahead with only North Island exhibitors. South Island exhibitors were asked to withdraw show and sale entries.

On January 16, based on information from MPI, the NZDE committee advised there would be no exclusions unless they were identified as or under movement control and providing all normal biosecurity measures were complied with.

Late on January 18, NZDE chairman Lawrence Satherley received a letter from DairyNZ chief executive Tim Mackle advising that although NZDE was perceived to be low-risk, DNZ's advice was to avoid co-mingling cattle between islands as links with infected farms were not completed. NZDE deputy chairwoman Johanna Wood received a call from MPI advising it supported the advice.

Mr Satherley and Mrs Wood described it as a ''huge disappointment'' for the event, which was celebrating its 10th anniversary.