Around 4000 cattle will need to be culled, as the battle against the disease mycoplasma bovis continues.
The cull is part of the Ministry for Primary Industry's (MPI) control measures after the cattle disease was detected on seven properties since it was discovered on a Canterbury farm in July.
MPI's director of response, Geoff Gwyn, says they are cautiously optimistic that they're dealing with a very localised area of infection around Oamaru.
"To prevent further spread of the disease, around 4000 cattle on five of the seven infected properties will need to be culled and a programme put in place to decontaminate the properties and then re-populate the farms," Mr Gwyn said.
"The two other properties have had a small number of animals culled already and no cattle remain.
"Moving ahead with de-population of the affected farms will allow them to get back to normal business as soon as it is safe to do so."
Dairy NZ, Federated Farmers and Beef+Lamb New Zealand have supported the actions MPI are taking, while at the same time recognising that this is a difficult time for the farmers involved.
Federated Farmers President Katie Milne says they understand that the disease has come at a significant emotional cost to the affected farming families and their animals.
"The process of culling whole herds will be very stressful for the people concerned," Ms Milne said.
"But the disease does not respond to treatment and cannot be vaccinated against.
"Culling is the only logical option to prevent ongoing suffering of the animals."
MPI anticipates the first stage of the process, which is removing the animals, will start after consultation with affected parties.
Most of the cattle will be sent for slaughter in accordance with standard practice.