A commercial laying hen produces one egg approximately every 24–26 hours through a highly coordinated hormonal and physiological process:

• Ovulation: A follicle in the ovary releases a yolk into the infundibulum. This is triggered by a surge of Luteinizing Hormone (LH).
• Albumen deposition (Magnum): The egg white proteins (ovalbumin, ovomucin, lysozyme) are secreted around the yolk in the magnum — the longest segment of the oviduct (34 cm, ~3 hours).
• Shell Membrane formation (Isthmus): Two shell membranes are deposited around the albumen (1–1.5 hours).
• Eggshell calcification (Uterus/Shell Gland): The eggshell (94% calcium carbonate, CaCO3) is deposited over approximately 17–20 hours. The hen mobilizes calcium from medullary bone and feed during this phase.
• Oviposition: The completed egg is laid through the cloaca. A new ovulation typically occurs 15–30 minutes after laying.

Commercial layer flocks follow a predictable egg production curve:

• First egg (Week 16–18): Production ramps up rapidly. First eggs are small (38–45g) and irregular.
• Peak production (Week 24–28): Hen-Day Production (HDP%) reaches 93–96%. This is the most critical phase for nutrition and management.
• Sustained production (Weeks 28–55): HDP% drops gradually at a rate of approximately 0.5–1% per week.
• Late lay (Weeks 55–72): Production declines to 65–75% HDP%. Eggshell quality may deteriorate as the shell gland ages.

Track your flock's production curve against breed standards using the Hen-Day Production Calculator.

Poor eggshell quality is a major economic problem. Common causes and solutions:

• Calcium deficiency: Thin, soft shells. Provide 4.0–4.5% calcium in layer diet. Use coarse limestone (2–4 mm) for overnight shell deposition.
• Phosphorus excess: Disrupts the Ca:P ratio for shell deposition. Ensure avP is not above 0.45% in layer feed.
• Heat stress: Reduces feed intake, lowering calcium consumption. Panting exhales CO2, raising blood pH and reducing carbonate available for shell formation.
• Infectious Bronchitis (IBV): Misshapen, wrinkled, or rough eggs. Caused by nephropathogenic IBV strains damaging the shell gland. Prevent with species-matched live and killed vaccination.
• Age of hen: Shell gland efficiency declines after Week 55, producing larger but thinner-shelled eggs.

Layer farming profitability depends on five key factors:

• Feed cost per dozen eggs (the largest cost driver)
• Hen-Housed Production % (total eggs per hen placed)
• Mortality rate throughout the laying cycle
• Market egg price and grading standards
• Pullet replacement cost and rearing age

Model your complete layer flock financial returns with the Layer Egg ROI Simulator.