Dairy NZ says a cull of infected cattle herds near Oamaru could not have been done any earlier.

The Ministry for Primary Industries has announced 4000 cattle from five farms will be destroyed to eradicate the disease.

It's been found on 7 properties in Canterbury and Otago in the last three months.

Mycoplasma bovis causes udder infections, abortions, pneumonia and arthritis.

Dairy NZ Chief Executive Dr Tim Mackle said although the scare started three months ago, MPI needed to map the spread before culling large herds.

"It's really important to do extensive testing not only within the affected group..of farms, but also much wider."

The MPI will soon assess compensation claims from the Mycoplasma bovis scare.

Mackle said those farms can get financial help through the Biosecurity Act.

"Most farmers don't have insurance against this kind of event, when an animal typically gets diseased then that's something that farmers deal with."