The dairy manufacturer Muller has ordered farmers across Scotland who supply them with milk to cut production because of an oversupply.
It has written to more than 250 dairy farmers asking them to reduce output because of changing consumer habits caused by the coronavirus crisis.
It has been estimated more than a million litres of unwanted milk is being produced across the UK each day.
This means some dairy product is having to be poured down the drain.
Even though demand from supermarkets has increased, that has not filled the gap left by the closure of cafes and restaurants.
Dairy farmer Ian Burgoyne from Crocketford, near Dumfries, said: "To have to do this after months and years of planning, large amounts of investment, it is a heartbreaking situation."
Muller has asked all dairy farmers to reduce their output by 3%.
It has suggested various ways this could happen such as feeding whole milk back to calves or retiring some cows from the herd early.
But there is also concern about the capacity to return to full production when lockdown conditions ease.
A spokesman for Muller said: "The Covid-19 pandemic has severely impacted the market for milk. We are asking farmers to temporarily reduce milk production by 3%.
"While supplying farmers will continue to receive their full contracted price, we hope that this collaborative approach will prevent the need for further and more serious measures."
Graham's Dairy has not restricted farm output but has admitted some milk has had to be thrown away.
Owner Robert Graham said: "We're working hard to find alternative uses and alternative capacity across UK for our product and we've been able to do that to some degree.
"Nobody wants to see waste but it's the volatility. It's the changes in customer behaviour and so much of the food service sector currently being closed."
Robert Hunter, from the Scottish Dairy Cattle Association, says margins are so tight for milk producers there is no wriggle room.
He added: "A lot of dairy farmers won't be able to ride this storm out. Because things have been so tight for so many years we have tightened everything down that we possibly can."
Dairy farmers have long complained that supermarkets undervalue milk and sell it too cheap.
The milk mountain is now pushing the price down further with some analysts saying those without a contract to supply it are finding that their milk is worthless.