How to Know If an Egg Is Unfertilized?

Hold the egg up to a bright light to determine whether it's been fertilized.

Hens that are over 20 weeks in age have the ability to lay eggs. For the eggs to be fertilized a rooster must mate with the hen. The difference between an unfertilized egg and a fertilized egg that does not develop is a mere 50,000 cells. At this stage the egg is edible and is nutritionally equivalent to an unfertilized egg.

Things You'll Need

• Egg
• Bright light

Instructions

1. Determine whether a rooster is present and has access to mate with the hens. If the hens do not have access to a rooster, none of the eggs will be fertilized. If a rooster is present, there is a chance the eggs may be fertilized.

2. Determine if incubation for the eggs is being provided either naturally or artificially. If no incubation is provided any fertilized eggs will fail to develop. These eggs are safe to eat and provide the same nutritional content as an unfertilized egg.

3. Hold the egg up to a bright light to illuminate the inside. A fertilized egg will have a dark center and a spider web appearance as the blood vessels begin to grow. An unfertilized egg will have a perfect yolk and should otherwise be transparent.

4. Recheck the egg in four days time to confirm fertilization status. After four days if no dark spots are present the egg is unfertilized.

Tips & Warnings

• If eggs are desired for consumption rather than breeding, remove them immediately if a rooster is present to prevent embryo development.

• A rooster's presence is not needed for a hen to begin egg laying.

References

• University of California: Egg Candeling and Breakout Analysis; R. A. Ernst, et al.
• University of California: Egg Basics for the Consumer; Francine A. Bradley
• Oklahoma State University: Often Asked Questions About Eggs and Poultry; Joe Berry