Milk could not be collected from Otago and Southland dairy farms yesterday because of treacherous road conditions, a Fonterra spokeswoman said last night.
About 1700 dairy farms' milk could not be collected across New Zealand, with nearly all the South Island affected.
Depending on milking cycle and storage capacity, some farmers' milk could be collected the next day, but some not collected would have to be dumped. She could not say how much would have to be disposed of.
Some farmers donated uncollected milk to local pig farmers, she said.
A decision on today's runs would be made early this morning.
"We have to make sure our [drivers] are safe. If the conditions are too treacherous, we can't let them go out."
Denis Aitken, who, with family, operates dairy farms at Maungatua and Momona on the Taieri Plain, said many thousands of litres of milk would be lost in Otago.
But it was "not a big drama", as farmers were compensated for milk not collected because of the weather, he said.
Because it was winter, dairy cows were not producing at full capacity and Fonterra was picking up milk every second day.
His next collection day was today.
Uncollected milk could not be tipped out into waterways or drains, Mr Aitken said. Instead, it was usually spread on to paddocks or used to feed calves.
While farmers did not like having to dump milk, there was nothing they could do, he said.
"The cows still have to be milked."
He estimated he had disposed of 7000-8000 litres of milk during the July snowfalls.
