Tags: Egg handling | Whitepaper
1 September 2014,
Eggshell is a well-organized structure, arranged in a matrix of organic matter (proteins) and a palisade layer of crystalline calcium carbonate columns. Between these columns, funnel-shaped openings, pores, are formed, which facilitate the exchange of gas, including water vapor, during the development of the embryo. The outer surface of the shell is covered by a waxy cuticle that protects the eggs from dehydration and invasion by micro-organisms.
From arrival in the shell gland, it takes approximately 20 hours for the egg’s shell to form completely. Albumen and shell membranes have developed while the yolk, with its embryo (blastoderm) on top, travelled through the magnum and isthmus, in the upper part of the hen’s oviduct. The shell gland is the part of the oviduct that secretes a highly concentrated solution of different minerals: calcium chloride, sodium bicarbonate, sodium chloride, potassium chloride and proteins. Shell formation begins with the precipitation of calcium carbonate crystals and glycoproteins on the outer shell membrane.
Calcium carbonate crystals are deposited at a constant rate of about 0.33 g/h. To facilitate smooth, regular shell formation, the egg rotates in the shell gland. Any disturbance of this rotation, for example when the female encounters an aggressive male during mating, produces abnormally formed shell. The shape and texture of the shells is therefore a good reflection of the health and well being of the breeder flock
This understanding is valuable to hatchery managers, not only to help evaluate the quality of the eggs delivered to the hatchery, but also to have valid input into discussions with breeder farm managers about ways in which to improve hatching egg quality. It is important to remember the influence of flock age on egg (shell) quality. Older flocks lay larger eggs with thinner shells - and the number of misshapen shells increases.
Poor hatching egg shell quality often results in increased weight loss and decreased hatchabilities, with an increased risk of cracks during handling leading to dehydration and contamination.
Broadly, there are three major classes of shell abnormality: