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Chickens: What’s the Deal with Calcium?

What's the deal with calcium

People know calcium builds strong bones and teeth in hoomans. Did you know calcium is the most prevalent mineral in the hooman body? Calcium also supports the muscle and vascular systems. While many people pour themselves a glass of (plant-based) milk to ensure they get enough calcium, it's not that easy for chickens. In today's blog, we're going to address what's the deal with calcium and why egg chickens need it.

Why do Chickens Need Calcium?

Calcium is important

The biggest reason chickens and calcium go together is eggshell quality. If your laying hens aren't getting enough calcium, they can produce eggs with weak or irregular shells. You may even see shell-less eggs!

Each eggshell contains 95% calcium carbonate. Chickens need to eat 20 times more calcium stored in their bodies to produce hard eggshells.

Calcium is also vital to osteoporosis prevention in chickens. Obviously, if your flock's bones are weak, they won't be able to stand, causing injury.

Calcium Requirements

Can chickens have calcium? The answer is yes, but they have different calcium requirements for different life stages.

Chicks under 18 weeks don't need extra calcium. They get all the calcium they need in their feed. Giving young chickens more calcium than their fluffy bodies can absorb causes kidney damage and decreases their lifespan.

Young adult laying hens, called pullets, need less calcium than fully grown adults. Pullets require 2.75 grams daily. Adult laying hens, older than one year, need 4-5 grams of calcium daily. Correct calcium levels in hens mean they doesn't have to deplete their bones of calcium to make eggshells.

How Can Chickens Get Calcium?

Adult layer feed contains all the calcium and nutrients needed for hard eggshells. However, chickens create a lot of wasted feed and may not belong to the clean plate club. Additionally, if your chickens are free-range or get extra whole grains, their diet doesn't provide complete nutrition. To ensure correct calcium levels, supplements are necessary.

A quick note here: pay attention to the calcium to phosphorus ratio in your flock's diet and supplements. Calcium and phosphorus amounts need to be balanced to prevent shell issues.

Types of Calcium Supplements

There are two kinds of calcium supplements that chickens prefer: oyster shell and fine granular limestone. Both are easy to feed and will keep your chickens healthy. When providing calcium to your chickens, make sure you keep it separate from their feed. If you add it to their feed, this will increase the amount of feed and supplement waste. Chickens will throw out the supplement while searching for the feed they want.

Calcium carbonate is the third kind of supplement; however, it's not as pleasing to the chicken palate. It can also cause a drop in the amount of feed consumed.

Chickens intuitively know when they need more calcium. By providing calcium supplements in a separate, dedicated feeder, they can help themselves.

Why Oyster Shell, Specifically?

Crushed oyster shells are the most common calcium supplement for chickens. The calcium in oyster shell is digested at a different rate than that found in their feed, so they have some extra during those night hours when they are creating shells. Finally, it's inexpensive, and chickens love it! Therefore, we carry oyster shell for chickens in our full chicken product line.

P.S. Be sure to keep the feeder with the oyster shell in a dry place. If oyster shell gets wet, it clumps.

What Kinds of Calcium are Bad?

  • Eggshells: We're all for recycling, but this is one method we don't endorse. We've all been taught not to eat raw eggs. Raw eggs contain salmonella. Chickens can catch salmonella from raw egg remnants on the shells. In turn, the salmonella is passed to hoomans when they eat the eggs. Also, you don't want to teach your flock to eat their own eggs. 🤢
  • Dolomite limestone: Dolomite contains 10% magnesium. The magnesium competes with the calcium for absorption, leading to calcium deficiency.

Too Much Calcium is Bad Too...

As we stated earlier, calcium and phosphorus amounts need balance for shell issues prevention. If your chicken has too much calcium, like all vitamins and nutrients, the excess is released in urine. Additionally, calcium excretion causes phosphorus deficiency. The phosphorous deficiency can manifest in up to three ways:

  • Eggshell issues: eggs with sharp ends, pimply eggshells, or soft or no-shell eggs.
  • Reduced egg production
  • Reduced feed consumption

Excess calcium in a chicken's system can lead to extra uric acid in the kidneys, causing blockages. Additionally, too much calcium causes soft bones, more commonly known as rickets.


Well, there you have it… now you know what's the deal with calcium. What kind of success have you had with chickens and calcium? Please share with us on our socials or send us an email at hoomans@smallpetselect.com.

Here's a great guide to learn more about what type of chicken feed and chicken grit your hen needs. 🐤🐣🐥

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