Slinkskins New Zealand general manager Ray Watson said the number of dead lambs and calves collected since Saturday indicated some parts of coastal Southland and South Otago had been very hard hit.
"There have been some huge losses."
The total number of stock deaths would not be known for some days, Mr Watson said.
Inland and hill country areas of Otago and Southland seemed to have escaped relatively unscathed, he said.
Parts of South Otago between Clinton and the coast were still under snow yesterday morning, but Federated Farmers Otago meat and fibre chairman Rob Lawson said the storm appeared to have been localised, and he had had no reports of heavy losses.
However, there were many dead lambs awaiting the slinkskin truck outside one Waiwera farm.
Rain yesterday washed away most of the snow, leaving some surface flooding, saturated soils and mud.
Federated Farmers Southland meat and fibre chairman Andrew Morrison said he had no idea of the extent of losses.
But he, too, said the impact appeared to have been localised, with his Waikaka Valley farm also relatively unscathed.
Rural Southland was trying to get back to normal yesterday, with Fonterra milk tankers again on the road after being unable to collect milk from about half Fonterra's 850 suppliers, mostly south of Edendale, on Saturday or Sunday.
Some farmers were forced to dispose of their milk through shed waste effluent systems, but some, such as South Hillend sharemilkers Rex and Roslynne Kane, chose to store about 15,000 litres of milk.
They filled a second vat and then large drums with milk, which will be fed to their 180 calves over the next few days.
Mr Kane said Fonterra collected milk for factory processing up to 48 hours after it had been taken from the cows.
Fonterra would still pay farmers for the milk that could not be collected.
Mr Kane had also been spending long nights out on his farm checking the 60 cows he had that were yet to calve.
"I don't like the feeling of lying in bed when calves are being born. It is best to get out there and grab them," he said.
The federation's Southland dairy section chairman, Vaughan Templeton, said his Riverton farm had about 15cm of snow.
Rain yesterday meant most of this had melted but with the wet ground conditions, pasture was being turned into mud.
"It's a bog. There are lakes everywhere."
He was forced to dump 18,000 litres of milk on Sunday and while he has not had stock losses, his cows were starting to lose condition, he said.