Secret camera footage from New Zealand reveals the cruel fate suffered by cows in the dairy industry with mothers chasing quad bikes taking away their calves only hours after they are born.

The video was aired on TV One's Sunday program and has caused outrage across New Zealand with the Ministry for Primary Industries launching an investigation, TVNZ reports.

The Sunday piece focused on the calves of milking cows, which are routinely killed in the most horrific of circumstances so they do not drink the milk that sustains the lucrative dairy industry.

Confronting vision shot in various locations across Waikato shows hours-old calves being separated from their mothers with disregard for their well-being.

The animals are tossed into the back of caged vehicles as their mothers watch on before giving chase.

Many of the calves are then taken to abattoirs were they are tossed around and eventually killed by blows to the head from a pole and a slash of the throat.

Farmwatch investigator John Darroch told the New Zealand Herald he witnessed "calves being torn from their mothers and left in the hot sun for hour after hour, thrown into trucks and then beaten to death".

He said he did not expect the level and scale of abuse he filmed.

"We have been getting calls from people in rural communities -- including farmers -- for many years asking us to look into the treatment of bobby calves," he said.

"But I had no idea that every time we posted a hidden camera we would get brutal treatment of calves. The scale and the frequency absolutely stunned me."

He said that the dairy industry viewed calves as byproducts because milking cows need to give birth at least once a year to continue to produce the substance that keeps the industry going.

In a statement New Zealand's Ministry of Primary Industries said it has launched an immediate investigation.

MPI Deputy Director General Regulation and Assurance Scott Gallacher said the treatment of calves shown on the Sunday program was unacceptable.

"Anybody seeing this type of abuse would be appalled. We share that view," Mr Gallacher said.

DairyNZ chief executive Tim Mackle said the industry and farmer were "shocked" by the footage.