A possible theft of 500 dairy cows from a Canterbury farm has stumped police investigating their disappearance.
Pennie Ormsby-Saunders told Newshub she has a herd of 1300 cows but last week noticed more than a third of them were missing.
Rick Powdrell from Federated Farmers says stock thefts are a concerning trend.
"In recent times there've been a number of thefts in that area. Now whether these are connected, we don't know.
"You have the opportunists who take the odd animal here and there, then you have what I call the professionals. These people would have to be highly organised."
He estimates the theft would have taken around 10 truck and trailer loads, and says it will be very difficult for the farmers in already stressful times.
"Everyone will be worried about their own stock, particularly in that area. The particular farmer and the family, it'll be devastating for them, in light of the state of the dairy industry at the moment."
The cows were in calf and grazing over winter south of Ashburton. Each cow would be worth more than $1000.