How to Improve Eggshell Quality in Laying Hens

The eggshell is not a simple wrapper but living tissue built in the shell gland over 18 to 20 hours, and it needs about two grams of calcium per egg. On Egyptian layer farms the problem usually appears as more cracked or broken eggs, or as pale, rough shells, a loss counted on every tray before it reaches the trader. Causes range from a simple nutritional gap to viral diseases of the reproductive tract, so adding more calcium alone rarely solves it.

How the shell is built

The shell starts as two thin membranes around the albumen, then layers of calcium carbonate are deposited over them in the shell gland. The hen draws calcium from feed and from the medullary bone reserve, which is mobilised mainly at night when feed is far away. Timing and particle size of calcium therefore matter as much as the percentage in the ration.

With age, egg size increases while the calcium available for the shell stays limited, so shells naturally thin after week seventy. Any inflammation of the shell gland leaves scars or irregular calcium deposits, a sign that must be read alongside the rest of the flock picture rather than alone.

Nutritional causes

A laying hen needs 3.8 to 4.2 grams of calcium a day, and part of it should come from coarse limestone or oyster shell with 2 to 4 mm particles so it stays in the gut overnight. Fine calcium is absorbed quickly and excreted before the shell gland needs it. Feeding in the evening or topping up calcium in the afternoon visibly improves shell strength.

Excess phosphorus blocks calcium absorption, vitamin D3 is needed to transport it, and shortages of manganese, zinc and copper cause deformities and rough shells. Mycotoxins damage the liver and prevent conversion of vitamin D to its active form, while excess salt causes diarrhoea and mineral loss. Review the ration with your veterinarian before adding any supplement.

Disease and environment

Infectious bronchitis, EDS virus and Newcastle disease attack the reproductive tract and leave thin shells or shell-less eggs, often preceded by a production drop or misshapen eggs. Bacterial salpingitis causes discharge and stained shells, while red mite drains blood and lowers both output and shell quality. These cases cannot be separated without veterinary examination and a clear vaccination history.

High heat reduces feed intake and causes respiratory alkalosis that pulls calcium from bone, so shells thin in summer. Crowding, frequent disturbance and irregular lighting raise cortisol and interfere with shell formation. Salty or contaminated water adds another factor, especially on farms using wells without routine analysis.

• Thin, translucent shells or eggs with no shell at all.
• More cracked eggs during transport and packing.
• Rough shells with irregular calcium deposits.
• Eggs stained with discharge or blood.
• A sudden production drop with a change in egg shape.
• Pale combs and weight loss where mites are present.

Measuring and improving in practice

Start by measuring the percentage of cracked and misshapen eggs weekly, plus egg weight, body weight and feed intake, because changes in these numbers come before economic loss. Shell strength can be checked with a simple gauge or a salt solution test, but a consistent record is enough to reveal the trend. Compare houses to see whether the problem is in the ration or in one particular flock.

Feed in the evening, add coarse calcium late in the day, keep water clean and cool, and reduce density and disturbance. Support with vitamin D3, manganese and zinc is a veterinary decision, and registered products can be ordered as poultry vitamins with water equipment from poultry supplies. Also review EDS in layers and medical supplies before changing the programme.

Conclusion

Shell quality is built with coarse evening calcium, vitamin D3, clean water and a calm environment, and destroyed by heat, disease and moulds. Measure the loss weekly, fix nutrition and environment first, then move to veterinary testing if the rate does not improve.

This article is general guidance and is not a substitute for examining your animal by a licensed veterinarian. In emergencies, contact your vet immediately.