Shell-less, Soft Shelled and Mis-shapen Eggs
The laying of soft shelled eggs can happen to both young hens, as their bodies change to get ready for egg production, and older hens as they reach the natural conclusion of their egg laying period, the egg shells can become thinner and weaker and therefore deformed.
In both these instances, the laying of soft shell eggs is fairly common, but in a middle aged chicken it can sometimes be a sign of a calcium deficiency. A calcium deficiency in a hen is easily solved, through either giving your hens Oystershell Grit to peck at, or through using a calcium supplement, like Flyte so Fancy Cal-Boost Poultry Calcium. Cal-Boost is a concentrated calcium supplement with added vitamin D3, which when added to drinking water will help improve shell strength, thickness and quality. Equally, oyster shell grit and making sure that their feed is a good quality, and well known feed, will help keep egg shells strong.
More common than a soft shell is for an egg to have a thicker band of shell around its middle. This is formed when a shock stops the egg in place. Extra layers of calcium are then deposited around this band, before the egg moves on. While fine for eating, these eggs shouldn't be used for hatching or selling.
Wind eggs or cock eggs are very small eggs, comprising of no yolk at all, just egg white. The opposite is what is called a double yolker, which is the reverse where there are too many yolks in one egg. Neither can be used for hatching.
There are other reasons that a hen might be laying a soft shelled egg. It can be something as simple as your girls are not getting enough daylight. Whilst they like somewhere dark to nestle down to actually lay an egg, they need to get plenty of daylight to get going. Convention says they need approximately twelve hours of daylight to produce an egg. Obviously during the short winter days your hens might go off lay, however, if your run or pen has a dark or black roofing on it, causing your hens to be in shade all day, this might have enough of an effect to stop them laying. A translucent roof covering is ideal. Equally some diseases, such as infectious bronchitis, can cause soft shelled eggs. A trip to the vet and some antibiotics can usually cure this, but obviously if you're using eggs for breeding, then the ones from the infected hen should not be used.
Perhaps rather than getting soft shelled or deformed eggs you are getting none at all. If the bird isn't too old or too young for laying eggs, then (as silly a question as it is) is your hen actually a hen? Through ignorance, poor sexing or deception, it's possible you have been given or sold a cockerel by mistake, therefore no eggs. Lastly, diet plays a big role in egg production. If a hen is fed too much of something that is bad for them, for example excessive amounts of treats, greenery, or a high protein feed, the bird can quickly become obese and stop laying.