ShelfLife.ie reports that according to a report in trade publication The Grocer, the Animal Health and Veterinary Laboratories Agency (AHVLA) of the UK Department for Environment, Food and Rural Affairs (Defra) is able to detect cage marks on eggs by examining them under a UV lamp. These appear in the form of parellel white lines running down the length of the shell.

Mark Jones, a technical expert for the AHVLA explained: “When an egg is laid, it picks up an imprint of the ground it’s laid on, which shows up under the light.

“By looking at the marks on the shells, we can tell what kind of system the egg is from.”

For example, an egg that has pimples on its surface when held under the UV lamp is an indication of an Astroturf floor, which is what certain nest box manufacturers use.

Eggs laid in other legal “enriched” cage systems may have different marks such as loop effects or webbing, which indicate they were laid on different types of plastic flooring.

By contrast, eggs produced in illegal non-enriched cages show only wire marks under the UV light, as well as “belt marks” left by the belts that transport the eggs from the cages.

However if an importer’s batch of eggs shows only a single egg with cage marks, this does not mean they will automatically fail the inspection. Enriched cages are still cages nevertheless, so it’s normal to see some eggs with cage marks in a legally produced batch.

However if over 14 per cent out of a batch of 90 eggs have wire marks and no nest box marks, the inspectors will put a hold of the consignment. They will carry out additional sampling and consult a confidential list of compliant producers, which each EU member state has had to compile, in an attempt to verify if the eggs were produced legally.

“If the producer isn’t on that list, we would then put a stop on the eggs and issue a compliance notice, which instructs the importer that they cannot move or market those eggs,” said Mr Jones. The inspectors subsequently carry out follow-up checks, and if they discover the importer has breached the compliance notice, they could face prosecution.

However, while it would be illegal to sell or market such eggs as the Class A eggs that consumers buy in shops, due to a regulatory loophole it is still possible for such eggs to be sold on as Class B eggs rather than be destroyed. Class B eggs are not fit for direct human consumption but can be used in food processing if they undergo heat treatment.

Meanwhile, Irish egg producers are reported to be breaking long-standing contracts with their buyers to cash in on prices which have risen by as much as 75 per cent following the EU-wide egg shortage caused by the ban on battery cages.