There are many abnormalities of eggs but the most common are:
Double yolk eggs
These eggs have two yolks which is brought about by two ova ripening simultaneously and dropping into the funnel. This is common in pullets when they start laying.
Meat spots are inside the egg either in the yolk or albumen. Normally they are degenerated blood clots coming from the ovary which form on the yolk or the oviduct which form on the albumen.
This comes about as a result of internal bleeding occurring in blood vessels of the ovary or oviduct. If the bleeding occurs in the ovary the blood spots are seen yolk and if bleeding is in the oviduct, blood spots are seen in the albumen. This condition is common with birds that lack Vitamin A.
Soft shelled eggs
This is caused mainly by inadequate amount of calcium, phosphorous and vitamin D in the diet. Practically eggs with soft shells can easily break when being handled or even when birds lie on them. They can also be easily damaged by microbes and therefore cannot keep for long.
Small eggs/yolkless eggs
This arises out of a stimulus produced by foreign matter for example blood clot coming from the ovary. In the process albumen is added onto the foreign matter. Pieces of membranes, feathers and so forth being transported up through recto-peristalsis can stimulate production of an egg.
An egg within an egg
The egg goes through all the processes of egg formation and for unknown reasons it is forced back to the magnum, where it stimulates formation of an egg. The whole process of egg formation is repeated on its membrane thus forming an egg within the egg. If the formed egg falls back to the uterus and break it causes peritonitis and may cause death of the bird. The yolk my also fall back into the uterus and this will also cause peritonitis. The condition is mainly prevalent in birds that have not been vaccinated against fowl typhoid.
Foreign matters in an egg
Feathers are the most common foreign objects in an egg. This includes any other foreign material coming into the funnel through recto-peristalsis.
Eggs with pale yolk
This is mostly seen in birds with deficiency in carotene or anemic birds. It can be corrected by feeding birds with the correct diet.
Rotten newly laid egg
Such eggs are laid by over fattened birds or birds with defects or diseases in the oviduct. If fertilized eggs overstay in the oviduct, the embryo starts to develop due to the high body temperature of the bird. But if the egg had not been fertilized the temperatures initiate microbial activities thus it starts to rot. Also if the vent is too small eggs overstay and start to rot.
Off flavors in eggs
Flavors acquired from various diets given to the bird. For example too much fish meal will bring about fish flavor.
This comes about from laying boxes being too dirty. Environments full of feces, moist or wet laying boxes all results in dirty eggs.