Key Points:

Sheepdogs have been banned from herding sheep at the processing plants of New Zealand's biggest meat company because of overseas concerns about the stress it places on the animals.

Silver Fern Farms has promised to stop using dogs at its plants by next year because overseas customers are worried over animal rights and meat quality.

The decision has angered shepherds, who fear it is only a matter of time before overseas pressure leads to dogs disappearing from farms as well.

"Sheep have had dogs around them from the day they were born. They were brought up with dogs - it's the New Zealand way," said mid-Canterbury shepherd Mick Petheram.

Silver Fern Farms spokesman Brent Melville said the company had been reducing the use of sheep dogs "in the international belief that the dogs frighten lambs and cause them stress going into the works".

"It's very sad in some respects, I think. It's the end of an era," he said.

"At the plant level, we use dogs in the same capacity that a farmer would use them on his farm. We have found in our plants that don't use dogs that we need just a minimal manpower to do the same sort of job."

But Mr Petheram is not sure how sheep will be herded around without the dogs through the likes of a wash, where the sheep are reluctant to move.

"In the end, people will have to push them physically. I know from my experience ... to shift stock, the frustration will build up and these sheep will be inhumanely handled."

Federated Farmers animal welfare spokesman Lachlan McKenzie said use of dogs in confined places was different to large paddocks, where there was distance between sheep and dogs.

"If we didn't have a little bit of stress in all of our lives, we would die. Too much is bad, but none is also bad."

SPCA Auckland chief executive Bob Kerridge said an untrained dog could stress stock, but those used in the farming were generally well-trained.

"I can't imagine for one minute the quality of meat or stock is altered in any way, shape or form by use of well-trained dogs."

Mr Petheram, who is not sure about his future once his six dogs are no longer needed, said big retailers wanted to label their meat as having come from "stress-free sheep" as a selling ploy.

"Which is complete and utter bullshit. If they could actually see what is happening ... they would be blown away."

He said he faced having to put his own dogs down.