Egg Formation in the Oviduct

Egg Formation in the Oviduct

• Egg formation involves several stages within the oviduct
• The process begins in the infundibulum
• The yolk, ovulated by the ovary, is captured by the infundibulum ( funnel-shaped part of the oviduct)
• Fertilization ( if it occurs) takes place here.
• The ovum, now called an egg, transitions to the magnum

Magnum

• Albumen (egg white): One type of albumen is initially produced in the magnum.
• Layers of albumen: Water addition and egg rotation lead to different layers of albumen (e.g., liquid inner white, dense white)
• Dense white (albumen): Makes up the majority of the albumen; mucin holds it together.
• Thick vs. Thin White: Thick white is initially more abundant in the magnum, but water addition and mucin breakdown in the oviduct result in a higher proportion of thin white when the egg is laid.
• Egg quality changes: After laying, thick white loses viscosity, volume decreases, while thin white becomes more watery and increases. This change is affected by temperature, humidity, age, and illness.

Isthmus

• The isthmus: A relatively short section (10 cm) of the oviduct.
• Inner and outer shell membranes: In the isthmus, the final egg shape of the shell membranes is formed, starting with the inner membrane.
• Outer shell membrane: Three times thicker than the inner membrane.
• Air cell formation: Inner and outer membranes separate at the large end forming the air cell
• Air cell Purpose: The air cell gradually increases in size as moisture evaporates through the shell pores as the egg ages.

Shell Gland/Uterus

• Shell Formation: The egg shell is formed in the shell gland/uterus.
• Shell Color: Color is determined genetically.
• Shell Pigment: Porphyrin is the brown pigment in eggshells
• Cuticle: A protective layer on the outside of the shell, made mainly of organic material.
• Cuticle's Role: Lubricates laying, seals pores after laying to inhibit moisture loss and bacterial entry.
• Cuticle damage: Washing and sanding eggs damages the cuticle.
• Solution: Mineral oil applied to the shell surface helps slow moisture loss after processing for better quality.

Vagina

• Vagina role: The final section of the oviduct, approximately 12 cm long, expels the egg.
• Egg Positioning: Usually laid large end first. Rotation before laying aids in this.
• Disturbances effect: If the hen experiences disturbance, the egg can be laid small end first.