Three breeding cows were shot dead with one being butchered and the meat taken, while another two were left suffering bullet wounds, and one calf is dead, on a Northland farm.

Farm owner Ian Russell is devastated by yet another "cowardly" attack by ruthless cattle rustlers on his Pouto Peninsula farm.

The Angus cows and calf were in a mob of about 60 when they were shot between January 10 and 12.

Russell, who has been breeding Angus for more than 30 years in the area, was away from the farm at the time but was alerted to the killings by his farm manager.

On searching paddocks where the stock were shot Russell found a silencer and 308 bullet cases which police took when they were called to the farm.

"One was shot on the neck and the other in the thigh and rump."

He estimated the value of the breeding cows to be about $1800 each.

The animal that had been gutted and the meat taken had been shot in the head four times.

While the death of the cattle is a financial loss, the fact two animals were injured and left suffering was the biggest blow. They may have to be put down.

"The one that got it on the rump is struggling to walk and losing condition. It's cruel they were shot and left ... it's so cowardly," he said.

A vet would be called to determine the fate of the animals.

Russell said he had lost more than 800 cattle and 2700 sheep to stock thieves off his various farms over 30 years.

Previously he had even installed cameras to catch the culprits but when the cameras were discovered by men skulking around the yards they burned down his woolshed, valued at $600,000.

Russell said he had spoken with other farmers in the area and they too had similar experiences recently with stock being either stolen or slaughtered.

New Zealand police were unable to supply statistics on the number of stolen stock reports in Northland before deadline.

Russell hoped in light of the latest incident on his farm politicians would move more quickly to make law changes in relation to those guilty of cattle rustling.

Last year the Sentencing (Livestock Rustling) Amendment Bill, a private member's bill from Rangitikei National Party MP Ian McKelvie, has been adopted by the Government as a Supplementary Order Paper on the Crimes Amendment Bill.

The amendment to the law increases the seriousness of livestock rustling by making it an aggravating factor at sentencing.

"Stock rustling is a crime that cuts to the heart of many rural families and the farming community," McKelvie said.

"Theft of livestock from farms or property is estimated to cost the farming community over $120 million a year. More recently, the risk to farms of Mycoplasma bovis spreading through stock theft has added strength to the call to take action.

"This activity is not only a threat to farming businesses, but it also creates a risk to people's safety in rural parts of New Zealand, as rustlers are often armed and equipped with tools to assist them."

The law change proposes two new offences to be added to the Crimes Act - theft of livestock or other animal, carrying a maximum penalty of seven years' imprisonment.

It also introduces a new offence of unlawful entry to land used for agricultural purposes, where the offender intends to steal livestock or act unlawfully against specified things, such as buildings or machinery, on that land, that carries up to 10 years' imprisonment.