Farmers are butting heads and turning on one another as stress takes its toll over the battle to contain the cattle disease Mycoplasma bovis.

The number of farms under question has accelerated over the past week from 129 to almost 300 properties, with 38 farms so far having been confirmed as infected.

Another 40 are considered highly likely to be infected.

About 11,000 cows have been killed so far, in an attempt to stop the spread of the cattle disease, and that number will rise to 22,000 by the end of the month.

Biosecurity Minister Damien O'Connor told Morning Report today about 60,000 cows were likely to be infected and were under scrutiny.

Federated Farmers dairy chair Chris Lewis said the uncertainty had caused a lot of stress for affected communities.

"It has turned neighbour against neighbour."

He said some farmers had lost their cool after discovering their neighbour was having cattle tested for the illness and had not told them.

"People are just under pressure and they don't react very well when they're under pressure."

Such behaviour was "just not warranted," Mr Lewis said, but he encouraged farmers to be upfront with their neighbours as there was a risk that livestock could pass the disease over a boundary fence.

"It's not something to be ashamed of. Just about all the farmers who've got it - they've done nothing wrong. They've probably got it by accident," he said.

"It's tough. There are no easy solutions, but these days you've got to support your fellow farmers. We're all in it together to get rid of this."

Southland farmer Bevan Collie said he understood the ill feeling and tension within communities.

"There'd be some frustration ... if you had a neighbour that was blasé to the disease and you're next door and you're not blasé to it."

However, Mr Collie said neighbours had to rally together. He has set up a support group for farmers and vets in the Southland region.

"Something like M bovis will be putting a lot of pressure behind some farmers and their systems ... neighbours just need to be mindful of that."

Biosecurity officials yesterday told MPs that efforts to wipe out Mycoplasma bovis had been hampered by a minority of farmers selling cattle on the black market.

Mr Lewis had a stark message for those farmers whose behaviour "hadn't been top-notch".

"Some individuals will need to pull up their socks and sort their shit out - or get out of the industry."

'Casual approach' to animal tracing made things worse - Minister

Mr O'Connor told Morning Report his focus was still on eradicating the disease if possible, but it was becoming more challenging.

He said the situation had been made worse by some farmers' "casual approach" to the animal tracing system, and the cow disease showed why a better was needed.

"I think each and every farmer now understands why we need a system that works and functions effectively so that you can go and push a button ... and work out where animal movements have gone.

"Relying on farmers' memory and notebooks has complicated this."

"It's a very unfortunate and difficult situation, we have absolute sympathy for every farmer involved in this.

"It's something that no government, no country wants to deal with."