A pregnant ewe has been caught in a gin-trap after sheep rustlers targeted flocks at Auckland's Cornwall Park.
The Federated Farmers said it was "shocked, but unsurprised" by what happened, and called for tighter legislation to penalise those who carry out such crimes.
"As we're on the cusp of main lambing I was shocked that they had targeted pregnant ewes, but they [the rustlers] probably do not care," Rick Powdrell, Federated Farmers rural security spokesman said.
"The current law offers no deterrent. We've seen sob stories being rewarded with community service and a few dollars in reparations. This doesn't reflect the gravity of the crime or the likely suffering of an animal being slaughtered by a rank amateur."
He described it as "bloody dangerous and stupid".
"At this time of the year a fair number of livestock are receiving animal remedies, as such, they are under a withholding period and until it clears their system should not be eaten. Anyone rustling will not have a clue so rustling is not easy meat," he said.
Attempts to steal sheep were a "daily reality" for many rural farms, Mr Powdrell said, but this attack on a central Auckland property was likely to "ram home to those in Auckland the magnitude of what our guys have to deal with".
Mr Powdrell said the federation had been in talks with politicians, and called on them to "stiffen penalties".
"In the meantime, farmers can provide information anonymously through the Crimestoppers line on 0800 555 111.
"In addition to online tools like Stop Stock Theft, farmers need to work together to report crimes and record suspicious behaviour," he said.