A Pukehina farmer is counting the cost of dead cattle as calving season approaches after a stock truck crate rolled killing six cows.

Strathallan Farms director John Cameron could only stand and watch while a McLeod crane righted the Pikowai Carriers stock truck's crate that overturned on the rural road with 35 heifers inside.

A farmer lost six cattle when the back trailer of the truck rolled on Old Coach Road. Photos: Bruce Barnard.

Police were called to the crash on Old Coach Road, about 300 metres from Ohinepanea Road on the Pukehina Station Road side, about 10.30am. The overturned trailer blocked the road for about three hours.

Tauranga Police Senior Sergeant Carl Purcell says the road has since been reopened to one lane.

John says the heifers were only being transported about 10km from one farm to another down the road for grazing.

'It's not much fun at all [seeing the dead stock on roadside],” says John.

'No one is hurt, that's the first priority.”

John is relieved it wasn't more of the herd, but remains worried about the flow on effects for the remaining cows in the crate.

The heifers were set to become part of John's herd of about 500 cows.

'It's the flow on effect that I'm worried about. The ones that are injured they are looking at abortion.”

Senior Constable Bruce Gordon says the driver was uninjured when the back trailer carrying the 35 cattle overturned.

About 20 stock were wandering on the grass verge next to the crash when SunLive arrived. Six in total were killed or put down as a result.

Police are still investigating the crash that occurred on a right-hand bend.