Virtual Chicken: Part 1: The Female Reproductive Tract

Summary

This presentation, brought to you by Auburn University's Department of Poultry Science, explains the intricate process of egg formation in hens. It covers the journey of nutrients from the hen's diet to the production of egg yolk, the role of follicles in yolk development, and the formation of egg whites and shells in the oviduct. It also discusses the role of bacterial contamination and its risks, egg fertilization, and the final stages of egg laying. The video concludes with the egg's journey to processing or hatcheries, highlighting the care taken in ensuring egg safety and quality.

Takeaways

• 😀 Hens convert nutrients from food into egg yolk components (1/3 protein, 1/3 fat, 1/3 water) that are transported via the bloodstream to the ovary.
• 😀 The largest follicle in the ovary releases the yolk, which will be laid as an egg, while the next largest produces the yolk for the following day.
• 😀 A follicle grows from under 1 millimeter to 25 millimeters in about 1-2 weeks before releasing the yolk during ovulation.
• 😀 The yolk is caught by the infundibulum, a funnel-shaped structure at the top of the oviduct, marking the start of a 24-hour journey through the reproductive tract.
• 😀 Fertilization, if it occurs, happens in the infundibulum before the yolk is covered by albumin.
• 😀 Salmonella and other bacteria can infect the reproductive tract of hens, leading to contamination of the egg and potential human disease.
• 😀 The yolk stays in the infundibulum for around 15 minutes before moving to the magnum, where it gets coated with albumin over about 3 hours.
• 😀 As the yolk moves through the magnum, it spins and forms two pigtail-like structures called chalazae, which keep the yolk centered in the egg.
• 😀 In the isthmus, the yolk and albumin are surrounded by two shell membranes, and the egg takes on a shape similar to a prune before entering the shell gland.
• 😀 The shell forms in the shell gland over 20 hours, with calcium carbonate crystals creating the shell, leaving pores that allow gas exchange.
• 😀 After the shell is formed, the egg goes through oviposition, where muscular contractions push it out of the hen's body.
• 😀 Once laid, the egg cools and contracts, forming an air cell between the membranes, which is vital for chick development if fertilized.

Q & A

What nutrients are primarily used to form the egg yolk in laying hens?

The egg yolk is primarily composed of one-third protein, one-third fat, and one-third water, which are derived from the food the hen eats.

How does the yolk travel through the hen's reproductive system?

The yolk is carried by the bloodstream from the liver to the ovary, where it matures. Once mature, the yolk is released from the follicle and enters the infundibulum, then moves through the magnum, isthmus, and shell gland before being laid.

What is the function of the infundibulum in the egg-laying process?

The infundibulum is the funnel-shaped upper end of the oviduct that catches the mature follicle from the ovary. It is also the location where fertilization can occur if sperm are present.

How does the egg white (albumin) form around the yolk?

As the yolk moves through the magnum, it is coated with albumin, which is formed through the secretion of proteins. The yolk spins in the magnum, causing the formation of two twisted structures called the chalazae that help keep the yolk centered.

What role do the chalazae play in the egg?

The chalazae are two pigtail-like structures that keep the yolk suspended in the center of the egg, preventing it from moving around inside the egg.

How does the shell form around the egg?

In the shell gland, a solution of calcium carbonate is secreted onto the egg's surface. The crystals of calcite form and expand, eventually bonding together to form a solid shell. Tiny pores are left between the crystals to allow gas exchange.

What is the function of the cuticle on the egg shell?

The cuticle is a protein layer deposited on the egg shell after it is formed. It helps protect the egg from harmful bacteria while allowing gas exchange through the pores in the shell.

What happens to the egg after it is laid?

After the egg is laid, it begins cooling, which causes the inner portion of the egg to contract, forming an air cell between the shell membranes. If fertilized, the egg goes to a hatchery; if not, it is processed for human consumption.

How does the hen's body temperature affect the egg after it is laid?

The hen's body temperature is around 106°F, which is significantly warmer than the environment where the egg is laid. As the egg cools, the inner contents contract, creating an air cell that will be used by a chick for breathing before hatching.

What are the potential risks associated with bacterial contamination in eggs?

Bacterial pathogens, such as Salmonella, can colonize the hen's reproductive tract. If these bacteria become associated with a developing egg before the shell forms, they can infect humans who consume the contaminated egg.