Investigations are underway into the sudden death of 120 cows on a farm in south Taranaki.
Owner John Murphy is distraught after the cows began dropping dead yesterday afternoon, 30 minutes after water troughs had been topped up using a portable tank.
Twenty vets from the area rushed to the farm to help, but there was little they could do.
The Ministry of Primary Industries has begun investigations centred around the portable tank.
Federated Farmers dairy chair Willy Leferink says the loss represents about a quarter of the farm's herd.
"These people would never have wanted to do anything negative, so it must be soul-destroying to see your cows die like that."
Willy Leferink says Federated Farmers is offering all the support it can.
If you can help in any way, register your details here at the Farming Show.
Whakatane dairy farmer Rod McPherson is mobilising help, and has already got a small group of farmers to pledge a cow each and has managed to get a local trucking company onboard.
He says if it had happened to him, he'd be out of the business.
"As soon as I heard the story, I thought I could afford [to give] one cow, and I'm sure many farmers around New Zealand could do the same."
Mr McPherson says those who want to help should contact their local Fonterra representative.