The death of the embryo inside the egg can have several different causes. A prolonged absence of the parents from the nest can have different reasons for instance this can be caused by hormone disorders, causing the deterioration of the hatching instinct, or the birds might suffer from parasites making them restless, or sometimes a bird having very long claws might, in his over-enthusiasm or shyness during mating, damage the eggs. Embryos from sick, weak or old parents and those who do not have sufficient nourishment available in the egg, or who are the result of a failed inbreed-mating, often do not have the strength to crack the shell should this happen to be a little harder than normal. They will therefore die inside the egg, and we will find them completely developed when opening the egg later on. The dampening of the eggs with a very hard shell can assist the young birds to hatch.
Vitamins are essential for life.
Lack or deficiency cause specific diseases, the so-called Avitaminoses, or Vitamin Deficiency diseases. Vitamins often have a close relationship to hormones, and they act either in cooperation with, or in opposition to them. Vitamins are also essential for ensuring a complete development of the embryo, to prevent its death inside the shell, and to guarantee a normal growth of the young. Vitamin A - The simple addition of codliver oil to seeds will increase the number of hatchings. On the other hand, females who have received no or insufficient amounts of Vitamin A will lay eggs which do not hatch, even after they have been fertilized and have developed.