Look out for these eggshell abnormalities

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There is a reason why the egg is often described as nature’s little nutritional package.

Eggs are an excellent source of high-quality protein and provide many essential nutrients needed for good health.

They contain all the essential amino acids the body needs and are also an important source of choline, which is particularly important for brain development. Eggs are also among the few foods that naturally contain vitamin D.

For the poultry farmer, however, an egg is more than food—it is the final product of a very carefully organised biological production line.

A healthy hen can produce an egg almost every day. The process takes about 25 hours, as the egg moves through the reproductive tract, or oviduct, where the yolk, egg white, membranes and shell are gradually added.

Under good management, a well-performing commercial layer can produce more than 300 eggs in a year.

But just like any production line, things can occasionally go wrong. The result may be a cracked, soft, rough, tiny, pale or oddly shaped egg.

These abnormalities are not simply cosmetic problems. When they occur frequently, they can indicate problems with nutrition, disease, management, housing or environmental conditions.

Blood-stained eggs: Finding blood on the outside of an egg can be alarming, but it is often associated with injury around the cloaca—the common opening through which the hen passes both eggs and faeces. Vent pecking by other birds is a common cause. It can also occur when immature pullets start laying too early, particularly following premature light stimulation. Avoid stimulating pullets with light before they are ready. Maintain appropriate lighting programmes, reduce factors that encourage pecking and ensure birds have adequate space, feed and water.

Misshapen eggs: Young pullets may occasionally produce oddly shaped eggs when they first come into lay. Older hens may also produce more abnormal eggs towards the end of the production cycle. However, if misshapen eggs suddenly become common, disease should be considered. Infectious bronchitis, Newcastle disease and egg drop syndrome can interfere with normal egg formation. The lesson is simple: prevention is better than trying to correct the problem after it has started. Follow a sound vaccination programme and monitor the flock closely for signs of disease.

Extremely small eggs: Very small eggs may be seen when pullets begin laying too early, particularly when immature birds are exposed to light stimulation prematurely. Heat stress can also reduce feed intake. When a hen eats less, it may not receive enough nutrients to maintain good egg size and production. During hot weather, make sure birds have plenty of clean, cool water and good ventilation. Feeding during the cooler parts of the day can also help maintain feed intake. Where appropriate, the diet should provide adequate nutrient and energy density.

Rough or corrugated shells: Rough, ridged or corrugated shells can occur particularly in older flocks. They may be associated with nutritional problems, certain diseases, stress and disturbances during shell formation. Mycoplasma infections, for example, may affect egg quality. Excessive calcium intake can also contribute to some shell abnormalities, so simply adding more calcium is not always the answer.

Thin, soft, porous or shell-less eggs: Few things frustrate a layer farmer more than collecting eggs that crack at the slightest touch—or worse, finding an egg with little or no shell.

Shell quality depends on a proper balance of calcium, phosphorus, vitamin D and trace minerals such as zinc and manganese. Poor feed intake, heat stress and sudden disturbances can also interfere with shell formation. Diseases like Infectious Bronchitis may also cause this problem; check with your local veterinarian to rule out disease complications.

Pale or discoloured shells: Most Kenyan consumers are familiar with brown eggs, largely because many commercial layers kept in Kenya are brown-egg strains. The brown colour comes from pigments deposited on the shell during its formation. Disease, stress and some medications can affect the intensity of this colour. Infectious bronchitis, for example, can cause brown eggs to become unusually pale. Certain medications may also alter shell pigmentation.

A sudden change in shell colour across many birds should, therefore, be treated as a flock management or health warning, rather than simply an unusual-looking egg.

Cracked eggs are money lost. If many eggs are arriving cracked at the egg store, start by checking the basics. Are there enough nest boxes? When too many hens compete for limited nesting space, eggs can be stepped on or damaged. Aim for adequate nesting space—around 4–5 hens per nest when individual nest boxes are used. Collect eggs frequently, particularly in busy periods. Five to six collections per day can significantly reduce the time eggs spend exposed to breakage. Handle eggs gently and avoid throwing or dropping them into trays. Do not stack trays excessively; keep stacks stable and within the recommended height for the trays being used.

As hens age, shell quality may naturally decline. Ensure that the flock receives an appropriately balanced layer diet and that calcium is available in a form and at a time that supports shell formation.

[Dr Messo is the company veterinarian, Kenchic; messo@kenchic.com]