An Ashburton farmer has received some flack after reporting the loss of around 500 cows.

The herd were scattered on a number of neighbouring properties, which is common in winter.

They were all about to calve and due to be brought back to the dairy farm.

Farmer Pennie Saunders reported the missing herd to police and a post went up on the NZ Farming Facebook page.

However the post was taken down after some unsupportive and nasty comments were posted.

Ms Saunders said it's not like losing your dog.

"There's some people out there who probably don't understand the dynamics of farming, you know, how can you just miss 500 cows?"

She said it's only when the cows are ready to give birth that they're brought back to the dairy farm.

"It wasn't like there was a herd there yesterday, and today they're gone, so it could have happened over a period of time. We just don't know."

Pennie Saunders said she doesn't have insurance for the cows, and they're in the process of working out how they'll handle the season.

Farmers are being advised to think of new ways of identifying their stock.

Federated Farmers Mid-Canterbury President, Michael Salvesen, said farmers shouldn't stop at the required registration tags pinned to the cow's ear - because they can be easily cut out.

"We should possibly be thinking about another form of identification, whether it is earmarks, or you could use freeze branding, which gives you a visible number on the outside of the animal, on the skin."

It's not the first time this has happened.

In December last year, more than one hundred cows went missing from several farms in mid-Canterbury.