Pin holes are round, very local holes in the shell, perhaps with some cracks around it, but often its just a hole in the shell without further damage. Although it is mostly observed with laying hens in battery cages, it can happen in free-range broiler breeders as well.

Pin holes are caused immediately after the egg is laid, when the egg is still wet and warm and the shell matrix is not yet rigid. Moreover, pin holes are sometimes caused by birds pecking at them, but most often they are caused by the bird's toenail.

In a good laying nest (roll-away or litter) the egg is protected sufficiently and the hen will not have the opportunity to damage it. However, if the egg is not protected because there is not enough litter in the nest, or in case of a roll-away nest, the egg can not leave the nest towards the egg belt easily, then pin holes are sometimes observed.

Possible causes and solutions:

For litter nests:
- add more litter to the nests
- have sufficient number of nests

For roll-away nests
- make sure the angle of the nest bottom is high enough for the eggs to roll away quickly
- make sure the opening between nest and egg belt is sufficient for the eggs to roll away easily
- replace the nest bottoms when they are worn out, as holes can be formed in the middle of the nest that prevent the eggs from rolling away