Free range eggs are set to disappear from the supermarket shelves now that bird flu has kept Dutch hens indoors for more than 16 weeks.

The restriction was introduced last October in an effort to stop the spread of the disease. If a hen has not been outdoors for the 16-week period, its eggs can no longer be classified as free range.

Aldi has already stopped with the sale of free range eggs and Albert Heijn, Jumbo and Plus have until January 25 to make it clear that their eggs are not free range either, news website Nu.nl reported on Tuesday.

The supermarkets say they will continue to pay farmers the price of a free range egg as long as the ban on outdoor pens continues, Nu.nl said.

Inflation and high energy costs have also helped push up the price of eggs by up to 28%, according to the Dutch poultry association.

A poultry board spokesman told Nu.nl that talks are underway within the EU about relaxing the 16 week rule as long as the bird flu epidemic continues, but that discussion has been postponed until the third quarter of this year.

Over four million birds have been killed because of bird flu since the start of the present outbreak. On Tuesday, the farm ministry said 60,000 layer hens have been culled on a farm in Duiven, in the east of the Netherlands, in what is the first case of 2023.