How to Make Calcium Supplements for Livestock Using Eggshells

Calcium is essential for your livestock, especially laying hens, who need roughly 20 times more calcium than what’s stored in their own bones just to keep producing strong eggshells. Eggshell calcium supplements are a genuine, low-cost way to help meet that need, since eggshells are roughly 94-95% calcium carbonate. But most guides on this topic skip two real risks worth knowing before you start.

Why calcium matters this much

An adult laying hen needs approximately 4 to 5 grams of calcium a day to meet her body’s needs and build a strong eggshell. A standard commercial layer feed with around 4% calcium content generally covers this for a hen eating about 4 ounces of feed daily. Calcium deficiency shows up directly as weak, thin, or missing eggshells, and it affects other livestock too, not just laying hens, since calcium supports bone development and overall skeletal health across species.

The two risks most guides don’t mention

Feeding hens their own eggshells back carries two genuine risks:

• Salmonella contamination. Eggshells can carry salmonella, and improperly sterilized shells introduce that risk directly into your flock’s feed. Thorough baking is not optional, it’s the step that makes this method safe.
• Egg-eating behavior. If hens recognize the shells as eggshells, some flocks develop a habit of pecking and eating their own eggs, a difficult behavior to reverse once established. This is why grinding the shells into a fine, unrecognizable powder matters as much as sterilizing them.

Done correctly, with thorough sterilization and fine grinding, eggshell calcium is a legitimate supplement, a controlled study on laying hens found extruded eggshell performed comparably to limestone and oyster shell as a calcium source at 4-8% dietary inclusion. If you want a simpler, lower-risk alternative, crushed oyster shell or ground limestone are commercially available options that skip both risks entirely, worth considering if you’re not confident you can sterilize and grind shells thoroughly enough every time.

How to make eggshell calcium supplement safely

1. Collect and wash the shells. Save eggshells after cooking, and wash them thoroughly with soap and water before doing anything else.
2. Bake to sterilize. Spread the shells on a baking sheet and bake at 250°F (120°C) for about 30 minutes. This step kills bacteria, including salmonella, and is the most important part of the process for food safety.
3. Grind into a fine powder. Use a food processor, blender, or coffee grinder to reduce the baked shells to a fine, unrecognizable powder. Coarse pieces that still look like shell fragments are more likely to trigger egg-eating behavior in your flock.
4. Store properly. Let the powder cool fully, then store it in an airtight container to keep it dry and prevent contamination.
5. Mix into feed. Add the powder to your livestock’s regular feed rather than offering it separately, this helps prevent birds from associating the powder with actual eggs.

For the full picture on layer feed formulation, including how calcium fits into a complete diet at each growth stage, see our guide on poultry feed formulation for layers.

Key takeaways

• Laying hens need roughly 4-5 grams of calcium daily; eggshells are about 94-95% calcium carbonate, making them a genuine, low-cost supplement source.
• Thorough sterilization (baking) and fine grinding are not optional steps, they directly prevent salmonella risk and egg-eating behavior in your flock.
• Commercially available oyster shell or ground limestone are simpler, lower-risk alternatives if you’re not confident in your sterilization process every time.
• Mix calcium powder into feed rather than offering it separately, to avoid birds associating it with real eggs.

FAQ

Is it safe to feed chickens their own eggshells?

Yes, but only with proper preparation. The shells must be thoroughly baked to kill bacteria like salmonella, and ground into a fine, unrecognizable powder to prevent triggering egg-eating behavior in the flock. Skipping either step introduces real risk.

How much calcium do laying hens need?

Roughly 4 to 5 grams of calcium daily. A standard layer feed with about 4% calcium content generally meets this for a hen eating around 4 ounces of feed a day.

What’s a safer alternative to eggshell calcium?

Crushed oyster shell or ground limestone are commercially available calcium sources that avoid both the salmonella and egg-eating risks associated with feeding shells back to your own flock, worth considering if you want a simpler, lower-risk option.

Why do hens sometimes start eating their own eggs?

If a hen recognizes eggshell fragments as coming from an egg, it can trigger pecking and egg-eating behavior that’s difficult to reverse once established. Grinding any eggshell supplement into a fine, unrecognizable powder before feeding it back helps prevent this from starting.