Farmers have mixed emotions about how the Ministry for Primary Industries is dealing with a cattle disease outbreak.

It comes as an eighth South Island farm's tested positive for Mycoplasma bovis- a small cell-wall deficient bacterium, which causes arthritis and pneumonia.

Dairy farmer John Gregan attended an MPI meeting in Waimate last night, and said there was a fair amount of concern amongst farmers.

"The farmers said it's difficult to monitor but they're doing their best and feel it wasn't unexpected on the properties that it had spread to."

Around 300 people attended the meeting in Waimate, for the disease that doesn't affect meat or milk produced by the infected cows.

"We have to trust MPI at the end of the day.

"They've got professionals doing the work and hopefully they do the right thing, but it's a bit like playing rugby from the sideline."

Mr Gregan said 1700 cows have already been culled - with 5000 expected to be gone by Christmas.

Cattle infected with a bacterial disease will be culled with extreme care.