Calcium Supplements for Chickens

When you Should Feed Oyster Shell to Chickens

Calcium Supplements for Chickens

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Calcium supplements for chickens can help you avoid shell quality issues in your flock, and it’s easy to feed. Farmers have been adding calcium to the diet of layers for generations to improve shell quality, and consequently, we’ve learned a few things about it.

Why Add Calcium?

Calcium is an essential nutrient in the diet of poultry. Not only do chickens need to build and support healthy bones, but they also need enough free calcium in their diet to produce a hard eggshell.

Shell Flaws

Not all shells are created equal. An ideal shell is relatively smooth, evenly colored, and maintains a consistent shell thickness. Sometimes you get bumps and deposits on your shells, which is no big deal. If, however, you see dark spots that crack easier than the rest of the shell, you have thin spots. Additionally, if your eggs are breaking too easily, you may be experiencing thin shells.

Soft Eggs

When the shell gland fails to produce a shell, a hen can lay an egg that appears to have a soft shell. If you’ve ever asked why is my chicken laying soft eggs, then you’ve seen this anomaly before.

“Soft-shelled” eggs are a bit of a misnomer. These eggs don’t have a shell that’s soft, but instead, they don’t have a shell at all. These eggs only have a shell membrane on the outside. The membrane usually holds the whole mess together, but it’ll feel like a wiggly ball of fluid.

Causes of Shell-less Eggs

Shell-less eggs are not usually caused by calcium deficiencies. Stress, illness, or lack of proper nutrition are more likely to be the reason your hen lays an occasional “soft-shelled” egg. Shell-less eggs do become more common as a hen ages, so don’t be surprised if you find one now and again.


When Not to Add Calcium

Young birds should never eat high calcium diets. Having more calcium than they can adequately absorb causes damage to their kidneys and therefore can shorten their lifespan.

It’s okay to feed grit for chickens to young birds, but don’t feed them oyster shell. Many people incorrectly think these two products should always be supplied together, so don’t make that assumption.

When to Add Calcium

If your birds are otherwise healthy, but you start seeing shell quality issues, it’s time to add calcium supplements for chickens to your feeding program. Routinely finding sub-par eggs in a healthy flock, such as thin shells, thin spots, and general malformations are all signs of poor shell quality. However, lumps, bumps, and extra calcium deposits on eggshells won’t be solved by adding calcium to a hen’s diet.

Molting chickens, or birds that have already molted at least once, are old enough to have free-choice calcium supplements for chickens. If you have shell quality issues in birds that have not experienced their first molt, look elsewhere for your problems.

Don’t Overlook Problems

Shell quality issues in first-year layers are usually because of management issues, so don’t assume that adding calcium will fix it. Some common issues that’ll result in reduced shell quality in first-year layers are changing over from chick feed too late, poor choice of feed, stress, and crowding. If you’re getting weak eggshells, make sure you’re feeding the right stuff and make sure all your bird’s needs are met.

Grit and oyster shell are two tools in our supplement toolkit. Each has their place, but don’t assume you need to supply both at the same time.

Diseases and Egg Shells

Infectious Bronchitis and other chicken diseases are also known to cause shell anomalies. Talk to your local or state veterinarian if you see odd shells consistently from your flock, and ask their opinion on the matter. Otherwise healthy looking flocks that routinely lay malformed eggs may have a low-level infection. Usually, blood or fecal tests will tell the vet what they need to know.

Calcium Supplements for Chickens

Crushed oyster shells are an excellent source of calcium, and are the most common way flock owners supplement calcium in their flock. Some people also clean and crush their used egg shells and feed them back to their hens. This works perfectly well, even though it may be a bit time-consuming.

If you believe it’s time to add calcium supplements for chickens to your flock’s diet, it’s an easy thing to do. I don’t suggest adding it directly to their regular grain because no one ever mixes it to their chicken’s liking. Birds will pick out and toss your oyster shell while looking for more grain, wasting your supplements.

Free Choice Oysters

Chickens are quite good at regulating themselves and know when they need a little more calcium in their diet. I suggest placing a dedicated feeder in your coop or outside run full of crushed oyster shell. When your hens need it, they’ll eat some. Just be sure the feeder is protected from rain because wet oyster shells will clump up.

Many people mix chicken grit to the mix, which is excellent if your birds don’t go outside. If your birds roam the great outdoors, don’t waste your time and money on grit, because they’re picking it up as they forage anyway.

Do you feed your birds calcium supplements for chickens? How do you feed it? Let us know in the comments below and join the conversation!

14 thoughts on “Calcium Supplements for Chickens”
  1. Mine get free choice oyster shell in a 7# feeder hung next to the feeders. I usually refill it about every 6-8 weeks. Also any eggs after 14 days are boiled, crushed and fed back. I chill them and they love them on hot days. I noticed my roosters won’t eat the egg shells but eat the egg itself. My ducks gobble them up too. All their eggs have nice strong shells.

  2. I have a chicken who recently started eating her eggs. She is an only chicken, has free choice oyster shells. So I am stumped as to why she started. A neighbor said she she is low on calcium and should be supplemented for more calcium. What do recommend?

    1. Chickens, as I understand it, will eat their own eggs if one, say, cracked one day, rolled out of the nest, or whatever – they will see it as food if cracked. That’s why even when we fed them scrambled eggs as a substitute, we are careful not to “clue in” the birds by cracking eggs and such where they could see us (sometimes if it’s super hot in Chicago, we give our 5 hens a break by letting them cool off in a partitioned spot in our kitchen/mud room. So they watch sometimes as I cook). Just be sure to get those eggs out of there as soon as you can each day. That, plus maybe a small treat (dried insects with added calcium – there’s a company called Grubbly which has soldier fly larva with 50x more calcium (1.5%) that mealworms. A treat near the laying time for your hen might help, too. But this is not a “behavior problem” — it is something that is quite natural if you have a super hungry hen!

  3. There is so much hype about not feeding calcium until they lay their first egg that I I searched for miles to finally find a feed store that sold low calcium feed for fear their livers would fail.

    Are we not to free range pullets? Garden forage is so rich in calcium, I’m wondering why I was sweating the 3% in feed.

    1. You’re supposed to feed chick feed until about 18 weeks but after 15 weeks you can feed an all flock type feed instead. Both types don’t have the extra calcium as layer feeds do.

      Due to cost, I often start my chicks out on a premium chick feed for 4 weeks, then switch to all flock feed until 16-18 weeks. My chicks are usually integrated with the main flock at that time and are only offered layer feed and oyster shell in separate feeders.

  4. Is it suitable to mix Lime ( Calcium carbonate ) with chook feed for free range chooks who dont eat she’ll grit ?

    1. No. Fertilizer lime ground limestone. Limestone comes from a wide variety of sources and in very different forms and degrees of hardness. Thus, its solubility, availability, and even its concentration in calcium can be unpredictable. For example, calcium concentration varies between 32 and 38 percent. Quite often, as is true in commercial practice, one batch of limestone might contain lower levels of calcium than assumed. Additionally, dolomitic limestone, which is also sold as “lime” contains high levels of magnesium (over 10 percent). Magnesium competes with calcium for absorption sites and as such, it is considered a problem in diets for layers. Excess levels of magnesium can also bind calcium in the gut, reducing thus its availability to the animal.

  5. I give my chickens corn pucks. Cut corn in a cupcake pan n fill with water. They really love it when it’s hot out. But they love it anytime really

  6. To deter egg eating I place a stone egg or glass egg in the nest. Also collect eggs often as every two hours or so if possible.

  7. My hens don’t eat oyster shell I got a coffee grinder because the oyster shell supplements that I had were very sharp I ground them up they take one or two bites and that was it. And they’re two years old they just finished molting so my question is this: the calcium pills that I take with vitamin D in it can I Crush those up and offer it to the hens? My hands don’t have a lot of dirt in their pen so what can I give them for Grit? Does any pet store sell small bags of grit for birds? I’m in Phoenix Arizona

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