Wilma and Aad van Leeuwen at one of their dairy farms in 2015.

The distress of battling Mycoplasma bovis and trying to keep a multimillion-dollar farm business has been laid to bare in emails between the Van Leeuwen Dairy Group (VLG) and the Ministry for Primary Industries.

The strain VLG owners Aad and Wilma van Leeuwen were under as they battle to eradicate the cattle disease while saving their farm business during, at times, a tense relationship with the MPI was shown in the release of more than 250 pages of documents released under the Official Information Act to Stuff.

Parts of the documents were heavily redacted for privacy or commercial reasons.

JOHN HAWKINS/STUFF "I have personally sat in their living room on at least six occasions and spent 12-15 hours with [the van Leeuwens]," said MPI response director Geoff Gwyn.

The van Leeuwens own 16 farms in North Otago. The disease was discovered on one of their farms on July 21 last year. Since then it has spread to 25 properties, mostly in the South Island.

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M bovis is a disease affecting dairy cows which causes mastitis, lameness, pneumonia and abortions. Once a cow is infected, it is impossible to be cured and has to be put down.

Examples of the correspondence includes:

An email sent from MPI to a person associated with VLG detailed a request to meet and discuss how the disease may have arrived on the VLG farm 'Tainui'. The person told MPI they were unable to attend until later that month.

When further pressed, the writer wrote: "You have provided us with another tiring answer. We have been so many times over this so what is the point. I am sorry our time is now fully devoted to saving somehow our farming business which has pretty well been ruined."

VLG was denied a request to transport breeding bulls from one of their farms to mate a mob of heifers after waiting 13 days for an answer from MPI.

After granting VLG permission to buy bulls, VLG requested confirmation that MPI would cover the cost, estimated to be $180,000. In an email to VLG, MPI demanded extensive information regarding the purchase before it could be justified.

In response, VLG said: "There is no time for this bureaucratic nonsense you put us into this situation. We are not trying to rip you off we are trying to run our operation in the hope we will survive this onslaught."

In another email sent earlier to MPI the unidentified writer reported "severe verbal abuse" during a conversation over a restricted place notice being placed on two properties in the VLG's district.

Major concerns were expressed over the actions of a person who was going to administer used needles when taking blood samples from bull calves. The person was persuaded to wait for fresh needles to arrive.

MPI responded two days later, thanking the people for bringing it to their attention and explained they had changed how samples were taken.

Other correspondence showed: blacked out letters from nearby farmers including an unidentified person "which had the first outbreak and are about to go broke".

In a statement this week, the van Leeuwens said working with MPI had at times, been a "frustrating exercise". They said the outbreak had put the business and its people under enormous mental and financial pressure. VLG's income had been slashed 25 per cent from livestock being culled while the business had to incur extra costs because it was locked down on restricted place notices, restricting animal movements.

"We believe [MPI] have no understanding of a dairy farming business and are unable to organise themselves to complete work in a timely organised manner to satisfy farmers' timelines and believe there is no consideration for the farmer's business and its ability to get up and running again."

MPI director of readiness and response Geoff Gwyn said that was unfair. Many of the staff involved were veterinarians and MPI had brought in people from organisations such as DairyNZ to assist them.

"I have personally sat in their living room on at least six occasions and spent 12-15 hours with them."

Gwyn said he was incredibly empathetic to VLG's situation.

"They have taken a hit for the team and all of the farmers out there under regulatory control, and while it may be cold comfort, what we are trying to do here is what is best for the entire dairy and beef and lamb sector, and unfortunately they are at the sharp end of that decision."

MPI and VLG had "learned together" because their farm was the first to find the disease, he said.

"I fully understand that this is causing huge stress and uncertainty for rural communities, but what I can assure you is that my team and myself are using our best judgment at any given point in time."