The Mycoplasma bovis outbreak was the "rainy day" the government was planning for, Ardern said.
The slaughter represents only a fraction of New Zealand stock, a herd of 10 million cattle in more than 20,000 dairy and beef farms.
The Prime Minister of New Zealand, Jacinda Ardern, described as "difficult" the decision to implement this plan, which aims to curb a disease that affects farm animals but which could also be extended to wild animals.
A massive 150,000 cows will be culled as the Government pushes ahead with eradication attempts. Picture taken March 12, 2013.
The disease, which causes udder infections, pneumonia and arthritis in cows but has no effect on milk and meat for human consumption, was first discovered on a farm on the South Island last July.
These are indeed large figures but they should be placed against the $8 billion economic contribution of the dairy industry, $2 billion from the beef industry, the country's reputation as a food producer and, perhaps most importantly, animal and farmer welfare.
1 NEWS visited a Canterbury farmer hugely affected by the cattle cull, announced by the government yesterday. But the alternative is to risk the spread of the disease across our national herd.
Mr Peters says he isn't convinced with the Government's Mycoplasma bovis plan.
Katie Milne, the national president of the advocacy group "Federated Farmers", emphasised the support that will be needed for farmers, however, failed to mention the 150,000 cows that will be slaughtered.
Officials carrying out the cull "have the legal authority to forcibly enter farms and kill animals even in cases where a farmer might resist, but they said they hope they don't have to use those powers", Bloomberg reports. They support farmers with information and advice on the practical aspects of the controls. They say numerous cows will be slaughtered at processing plants and used for beef, but some cows will have to be killed and buried on the farms or dumped in approved landfills. The dairy herd of the country reportedly has around 6.6 million cows. It will only be clear by the end of year if the culling of the cows is working.