Mycoplasma bovis cattle disease may be too far gone - expert

A farming expert says the Government needs to accept culling all cows affected by Mycoplasma bovis might no longer be an option, with the actual number of affected cattle unknown.

"I think it could be 10 times worse than it is," Forward Farming's managing director David Law told The AM Show.

"If you keep testing for it, we'll find it. If it's going to be 10 times more you've got to stop culling them... We'd keep them alive."

Prime Minister Jacinda Ardern told the show the Government is considering whether management of the disease is a better idea than eradication.

"We've got to try factor in the cost of living with bovis versus the cost of trying to eradicate it. And at the moment, to be honest, we're considering all the options.

"What I want to make sure we do though is factor in that we might take into account the cost of culling. But we also have to take into account the cost to productivity."

Arthritis and loss of calves caused by the disease would both have heavy hits on productivity, Ms Ardern says.

Tens of thousands of cows have been or are being culled since the disease was first discovered in July 2017.

Last week Agriculture Minister Damien O'Connor told Newshub Nation more than 70 farms are likely to be affected, 300 under investigation and 1700 of interest.

"At the moment, we're halfway through the process of culling 22,000 [cows], and there's up to 60,000 potentially in those affected properties already identified. So the numbers are very, very big."

But as more and more cases emerge the Government has been forced to consider alternatives.

"Unlike some other animal health issues, you can't really necessarily establish in one simple test that an animal has bovis," Ms Ardern says. "And that's been the really difficult thing."

Mr Law says instead of culling affected animals, we should be working on "trying to make the host stronger than the disease".

"You can get rid of it by growing better feed, and you can't grow a good feed until you have good soil. And I think that's where we've been lacking.

"The soils have got to a stage where the feed and the cows, the stress that they're under, is just pushing the cows to be under too much pressure. And it's affecting their immunity to fight a disease."

Ms Ardern says the Government will consider every option.

"We don't want to look back on this moment in time and have any regret that we didn't try something that we should have.

The disease had been confirmed on at least 38 farms across Southland, Otago, Canterbury, Hawkes' Bay and Manawatu.