Soft or missing egg shells are quite common in older older birds, especially high production hybrids and especially as they come out of lay for the season.

In younger hens, sometimes an egg stays in the shell gland for too long (see calcium coated shells) and the egg that follows it doesn't spend long enough. In these circumstances, the two eggs are laid closely together on the same day.

Thin egg shells can occur on hot days when the temperature rises. This is associated with a lower food intake and shell thickness will return to normal when the temperature drops and the food intake returns to normal.

Soft Shelled Eggs

Most people immediately think that Oyster shell grit is what a hen needs if she is laying soft shelled eggs but a dietary deficiency can also be the cause of a ‘soft' shelled egg. Whilst chickens need calcium in their diet which can be provided by soluble grit (such as Oystershell) to form egg shells, sufficient calcium can usually be found in modern formulated poultry feeds. Chickens need the correct level of protein in their diet as well as minerals and various other vitamins. Vitamin D3 (Cholecalciferol) for example is used for the metabolism of calcium and phosphorus so that they are able to form egg shells as well as strong bones. Vitamin D is found in Cod Liver Oil but they shouldn't normally need this if they are fed the correct formulated layers feed and have free range and sunshine on their backs.

Corn treats and kitchen scraps

Wheat found in mixed corn typically contains about 10% protein. This isn't a sufficient amount for a hen that is producing eggs. Keep corn as a treat only. Kitchen scraps are a bit of a mixed bag of what a hen needs so whilst this is an efficient way to recycle them and save on feed costs, scraps should not really exceed 25% of a hen's diet. Scraps should be mixed with layers mash to make a crumbly mixture. The best way to ensure a hen is getting the correct diet is to use a balanced layers feed and then supplement this with greens and a vitamin and mineral drink that can be added to their water during the peak months of production. More information can be read here about feeding chickens.

Free Range Hens

If hens can be allowed to free range on grass or rough ground then this is much better than having to add top up vitamin and mineral drinks. They will be able to pick up a lot of the extra grit, vitamins and minerals they need from and be a lot less prone to health problems as well as soft shelled eggs.

Some strains of birds can lay more soft egg shells as they age. This is particularly true of hybrid breeds that have been optimised to give as many eggs as possible during their first year such as the Bovan Goldline often found in ‘battery' farming. Once these birds reach 4 or 5 years old, you may find they start to lay eggs with soft shells.