Sheep and cattle rustlers in Waikato are selling the animals they steal on the black market, according to Federated Farmers.
The comments come after cows were shot with a crossbow on a farm at the southern end of the Hunua Ranges.
The owner of the farm, David Olsen, said he suspected the shooters were trying to steal them to sell the meat or use it themselves.
Waikato Federated Farmers meat and fibre section chair Chris Irons said some Waikato farmers have lost up to 150 sheep to rustlers.
"A lot of rustling, especially the bigger numbers, are being rustled for the black market supply, for meat. The odd one or two that have gone missing, that's probably just people pinching them for themselves."
Mr Irons said farmers should report any suspicious activity around their properties immediately to police.