"The industry are hanging out and waiting for a decision so they have some certainty."
He said either decision would be hard but unsurprising to farmers.
"They understand that tough calls have to be made for the greater good of the long-term industry."
Ardern said there around 40 properties with confirmed infection and potentially up to 70 more, but hundreds more were being tested so that figure would change.
DairyNZ chairman Jim van der Poel said farmers had been living with uncertainty for some time and he expected some concern would be relieved with a decision.
Beef+Lamb New Zealand chairman Andrew Morrison said farmers would be helped, no matter what the decision was.
The acceleration of the disease's spread comes as farmers prepare for Gypsy Day on June 1, when sharemilkers move their cows to new farms.
Ardern and O'Connor yesterday met farmers in Waikato, where a case of M. bovis was detected last week for the first time.
Ardern told farmers there the crisis had not yet reached the point where the Government response would change from eradication to containment.
She said the costs of the crisis were likely to easily exceed the $85 million the Government had already put aside but would not say what share of the costs would be covered by farmers.
Meanwhile, police have begun an investigation into the source of the outbreak.