Egg shell quality is mostly influenced before the egg is laid. The thickness of the shell is directly related to the time the egg spends in the shell gland—generally, the longer it remains in the gland, the thicker the shell will be. This means that eggs laid earlier in the day tend to have thicker shells compared to those laid later.
Calcium deposition also plays a key role in determining shell quality. If a hen’s diet provides adequate calcium and it is properly absorbed, the shell will be strong and well-formed. Darker-shelled eggs tend to have better shell quality than lighter ones. This difference may be linked to the health of the birds— hens that are unwell use nutrients to maintain their health rather than for producing robust eggs. Excess sunlight can also result in pale eggs, though the exact reason why too much sunlight affects shell pigmentation is not well understood.
Disease can also have a significant impact on shell quality. Infectious Bronchitis (IB) is a common cause, often resulting in rough, discoloured, or wrinkled shells. IB affects the entire reproductive tract, including the shell gland, leading to misshapen eggs and watery egg whites. Two to five days after exposure to IB, hens may start producing pale eggs as the virus disrupts normal pigmentation.
Good management practices, especially around nutrition and lighting, are essential for maintaining shell quality. There is a direct relationship between egg size and shell thickness: the bigger the egg, the thinner the shell. This is why it’s important to control egg size, even though larger eggs are in high demand. Extending daylight hours slowly helps hens mature properly before laying, which helps prevent oversized eggs. Regular egg weighing and adjusting diets accordingly can also help, and CMC can support producers with these practices.
Shell quality naturally declines as hens age. After 40 weeks, hens lose some of their ability to mobilise calcium from their bones, which reduces the production of calcium carbonate needed for forming shells.
Stress also negatively affects shell quality. When hens are under stress, they produce acidic secretions that damage cells lining the oviduct and uterus, resulting in thin or misshapen shells. In extreme cases, calcium deposits may appear on the shell surface.
Overall, maintaining good shell quality is crucial for successful egg production, as poor-quality shells can lead to financial losses. Careful management of diet, health, and environmental factors is key to ensuring hens produce consistently high-quality shells.