This presented itself as chronic pneumonia with the "worst coughing you've ever seen", bad upper respiratory problems and ear infections with pus running out of their ears.
"It didn't matter what penicillin we gave them, it wouldn't work."
"The reason we were so badly infected is we didn't start with one or two infected animals, we started with 61 infected animals and it snowballed at a hell of a speed from there, that's why we lost so many animals.
"We had over 400 animals shot or [that] died on the farm."
Duncum asked about the toll on Walling's family.
"Pretty harsh, to understate it."
Walling said despite going through the compensation process "you're never going to get back to where you were."
"We would have had over 2200 animals by now. It will be another couple of years before we get back to that stage."
He said that moving forward, they'd be a lot less naive.
"We can't farm the way we used to.
"Sick livestock is not farming, it's not an option."
Walling said he wasn't sure how people thought they could manage the disease.
"If you've been through it, you'd realise how wrong that is. People overseas do not farm like we do."
Duncum asked, after all he'd been through, how had the experience not killed his desire to farm.
"You ask yourself that quite a bit," he said.
"You go farming expecting tough times, this is a tough time you've got to work your way through. That's how I look at it.
"Keep the right attitude, do your bit for farming and keep moving forward."
"If you don't have the right attitude you just make it worse for other people."
Latest numbers
The Ministry for Primary Industries says there are 33 currently infected properties, made up of 16 dairy farms, 15 beef farms and three other properties.
Fifty-nine properties are under Restricted Place Notice. All infected farms and farms suspected of having Mycoplasma bovis have a Restricted Place Notice, which prohibits all unauthorised movements of farm stock and other risk goods on to and off the property to minimise the chance of the disease spreading from the property.