The egg is often referred to as nature’s perfect packaging, but it would seem that this is not always the case, with some doing a far better job at protecting their contents than others.

This may, however, be about to change.

Researchers are now looking at how the eggshell’s cuticle can be improved and so reduce the vertical transmission of pathogens.

A team at the UK’s Roslin Institute is putting genes that are linked to cuticle quality under the microscope, with a view to selectively breeding chickens with beneficial genes that may lead to eggshells better performing.

The cuticle, which is formed during the last 1.5-2 hours of eggshell formation in utero, functions not only as a regulator of gaseous exchange across the shell but also as the first line of defense against microbial penetration.

If the Roslin team is able to improve the cuticle it should lead to healthier chicks and safer eggs.

In birds that live in challenging environments, the cuticle tends to be thicker, suggesting evolutionary pressure, however, in domestic poultry, pressure for this trait has been removed.

As part of the work, the Roslin’s researchers will also look at how factors in the environment, stress, hormones and the age of the hen can impact cuticle quality. The Institute has developed ways of measuring the amount of cuticle that each hen deposits and has developed techniques that measure cuticle quality, including chemical structure.

These latest studies build on work published in 2013 that was able to quantify the cuticle layer and derive genetic parameters for the trait. That work found that micro-organisms almost never penetrated eggs from the best hens, while those from the worst were more likely to be infected.