Do Chicks Care About Calcium? Or is it about companies and outdated studies

[CabritaChicks]

People love to debate calcium and salt content in a chicken’s diet. Some claim that too much calcium for young birds is dangerous, but have you ever stopped to question where that idea comes from?

I live in a place where feral chickens rule the land—quite literally. Toss a stone, and you’ll probably hit one (not that you should). These birds thrive on the sea, not just near it, but on the coral reef itself. Not sandy Florida beaches—actual reef. And guess what? They multiply like cockroaches, and we watch them grow up, and they are healthy.

The idea that too much calcium is harmful to young chickens has been around since at least the 1960s, with studies showing that excess calcium could reduce growth, disrupt nutrient absorption, and cause mineral imbalances (I do not dispute that!). Research from the '90s reinforced this, linking high calcium intake to issues like hypercalcemia and poor performance in broilers.

But here’s the thing—my findings don’t line up with this narrative. Feral chickens in my area thrive while pecking at coral and shells, with no signs of these supposed calcium-related issues. It makes me wonder: Are these studies overlooking the bigger picture of a natural, varied diet? Or is the problem more about artificial feed formulations rather than calcium itself?

Now, let’s be fair—calcium can be bad. Too much, in isolation, can cause kidney damage or mess with a bird’s ability to process other nutrients. But here’s the thing: calcium is just one piece of the puzzle. Saying "young chickens shouldn’t get calcium" is like saying humans should eat more avocados. Sure, avocados are great, but they’re still just fat. You don’t live on just fat, and chickens don’t live on just calcium. Their diet is a whole recipe, and nature has been mixing that recipe long before we started overanalyzing it.

So when I hear warnings about "excess calcium harming young chickens," I can't help but raise an eyebrow. These birds peck at shells, coral, and whatever else nature provides, and they seem just fine. So I dug deeper. As a scientist, I wanted real answers. And what did I find? Many of those "calcium overload" studies are backed by pet food companies—the same industry that once force-fed Purina dog food to canines (and let’s be real, that’s not exactly gourmet nutrition).

The real issue? A bad diet makes the perfect storm. If a chick is already on an imbalanced, artificial diet, then yes, adding too much of one thing—like calcium—could cause problems. But personally, I think the sooner they get used to their natural environment, the better. Feral chicks don’t get some carefully measured calcium supplement—they get whatever nature hands them, and they’re thriving.

So, is calcium really the villain? Or is this another case of corporate-driven misinformation?

What do you think?
.... not here to start an argument, just a conversation as I am interested.

BTW, these are some of the studies I was specifically looking at:

• Maxwell, M.H., Robertson, G.W., and Mitchell, M.A. In 1993, they published a study titled "Ultrastructural demonstration of mitochondrial calcium overload in myocardial cells from broiler chickens with ascites and induced hypoxia," examining calcium deposits in heart cells of broilers under hypoxic conditions. AGRIS+1AGRIS+1
• Shafey, T.M. Also in 1993, Shafey authored "Calcium tolerance of growing chickens: effect of ratio of dietary calcium to available phosphorus," exploring how excess calcium intake affects growth, feed efficiency, and bone strength in growing chickens. Cambridge University Press & Assessment+1NCBI+1
• Sebaei, M.G.E., El-Shafei, R.A., El-Adl, M.A., Farag, A., and Eladl, A.H. In 2020, they conducted a study titled "Biochemical and molecular investigation of oxidative stress associated with urolithiasis induced by increased dietary calcium or protein in chickens," evaluating the impact of high dietary calcium or protein levels on various health parameters in chickens. PubMed
• Honarbakhsh, S., Zaghari, M., and Sang, B. Their research, "Effect of excessive calcium feeding on health of gastrointestinal tract in broiler breeder hens," investigated the impact of high calcium diets on the gastrointestinal health of broiler breeder hens. Brill

 

[nuthatched]

The glaring difference being the matter of choice.
Nonlaying birds such chicks, pullets, molting/broody hens and males shouldn't eat high calcium layer feed since there's no where for the calcium to go as opposed to egg laying females.
There's a big difference between pecking at coral as needed and have relatively high levels of calcium forced into Every. Single. Bite.

another case of corporate-driven misinformation?

Hmm, honey.
If you don't like corporate-funded research, you're going to find limit options on peer reviewed papers.
Most corpate entities do fund research for their own benefit. Does that make the research wrong? No.
The majority of poultry research is short term [less than 2 years] because meat and egg companies don't keep birds longer than that.
If the consensus among scientific papers, the knowledge of Veterinarians (who's purpose is to keep the animal healthy) and the experience of your little ol' backyard keeper all indicate that a diet of no-choice high calcium diet to a non-laying bird is harmful to their long term health, then it better to error of the side of caution and provide them with calcium they can take if they need.
For some birds, the daily high calcium is better, such as for high production birds.

Poultry Science is the most researched area of Agriculture on the planet, you can pick any country you wish for research.

I'm just going to point out that your local feral chickens are likely more akin to a jungle fowl at this point, probably pretty lanky, alert, slim and sporty, can fly fairly well, less production per hen, than your average backyard hen.

 

[U_Stormcrow]

People love to debate calcium and salt content in a chicken’s diet. Some claim that too much calcium for young birds is dangerous, but have you ever stopped to question where that idea comes from?

I live in a place where feral chickens rule the land—quite literally. Toss a stone, and you’ll probably hit one (not that you should). These birds thrive on the sea, not just near it, but on the coral reef itself. Not sandy Florida beaches—actual reef. And guess what? They multiply like cockroaches, and we watch them grow up, and they are healthy.

The idea that too much calcium is harmful to young chickens has been around since at least the 1960s, with studies showing that excess calcium could reduce growth, disrupt nutrient absorption, and cause mineral imbalances (I do not dispute that!). Research from the '90s reinforced this, linking high calcium intake to issues like hypercalcemia and poor performance in broilers.

But here’s the thing—my findings don’t line up with this narrative. Feral chickens in my area thrive while pecking at coral and shells, with no signs of these supposed calcium-related issues. It makes me wonder: Are these studies overlooking the bigger picture of a natural, varied diet? Or is the problem more about artificial feed formulations rather than calcium itself?

Now, let’s be fair—calcium can be bad. Too much, in isolation, can cause kidney damage or mess with a bird’s ability to process other nutrients. But here’s the thing: calcium is just one piece of the puzzle. Saying "young chickens shouldn’t get calcium" is like saying humans should eat more avocados. Sure, avocados are great, but they’re still just fat. You don’t live on just fat, and chickens don’t live on just calcium. Their diet is a whole recipe, and nature has been mixing that recipe long before we started overanalyzing it.

So when I hear warnings about "excess calcium harming young chickens," I can't help but raise an eyebrow. These birds peck at shells, coral, and whatever else nature provides, and they seem just fine. So I dug deeper. As a scientist, I wanted real answers. And what did I find? Many of those "calcium overload" studies are backed by pet food companies—the same industry that once force-fed Purina dog food to canines (and let’s be real, that’s not exactly gourmet nutrition).

The real issue? A bad diet makes the perfect storm. If a chick is already on an imbalanced, artificial diet, then yes, adding too much of one thing—like calcium—could cause problems. But personally, I think the sooner they get used to their natural environment, the better. Feral chicks don’t get some carefully measured calcium supplement—they get whatever nature hands them, and they’re thriving.

So, is calcium really the villain? Or is this another case of corporate-driven misinformation?

What do you think?
.... not here to start an argument, just a conversation as I am interested.

BTW, these are some of the studies I was specifically looking at:

• Maxwell, M.H., Robertson, G.W., and Mitchell, M.A. In 1993, they published a study titled "Ultrastructural demonstration of mitochondrial calcium overload in myocardial cells from broiler chickens with ascites and induced hypoxia," examining calcium deposits in heart cells of broilers under hypoxic conditions. AGRIS+1AGRIS+1
• Shafey, T.M. Also in 1993, Shafey authored "Calcium tolerance of growing chickens: effect of ratio of dietary calcium to available phosphorus," exploring how excess calcium intake affects growth, feed efficiency, and bone strength in growing chickens. Cambridge University Press & Assessment+1NCBI+1
• Sebaei, M.G.E., El-Shafei, R.A., El-Adl, M.A., Farag, A., and Eladl, A.H. In 2020, they conducted a study titled "Biochemical and molecular investigation of oxidative stress associated with urolithiasis induced by increased dietary calcium or protein in chickens," evaluating the impact of high dietary calcium or protein levels on various health parameters in chickens. PubMed
• Honarbakhsh, S., Zaghari, M., and Sang, B. Their research, "Effect of excessive calcium feeding on health of gastrointestinal tract in broiler breeder hens," investigated the impact of high calcium diets on the gastrointestinal health of broiler breeder hens. Brill

I think you've drawn improper inference from your anecdote, and need to read more studies. Maybe give some consideration to control of variables, as well..

There is a marked difference between a free range bird self-regulating calcium intake (as in your anecdote, and the experience of all of us who offer oyster shell or another calcium source in separate dish) and birds whose calcium intake is directly determined by the quantity of their homogenized feed intake. And there are studies to back our experience an anecdotes.

Birds eating a homogenized feed will eat to meet their dietary energy needs as their first priority - even if that means eating an excess of calcium. Numerous health consequences can result. Most pronounced in very young birds (as are most other nutritional deficiencies), but also time and dose dependent.

To the extent your comment above might suggest that the calcium needs of hatchlings and prime production hens during their laying periods are similar, I'd suggest you rethink that assumption, which is implicit in your suggestion.

but if you would like to fund your own research for publication (here or elsewhere), please do. As your peers, we'd be happy to review.

 

[saysfaa]

...

What do you think?
.... not here to start an argument, just a conversation as I am interested.
...

I think there is something to what you are saying about calcium being one piece of the puzzle.

I've been doing quite a lot of research about osteoporosis in people and have a dairy farm background. One of the things about calcium is that what else is eaten when calcium is eaten has a lot to do with how much of the calcium is absorbed by the digestive system. In people and cattle, anyway. I assume also in chickens. So, your feral birds may be able to eat much higher amounts of calcium without detrimental effects than the studies indicate if they are also getting different amounts of vitamin D, vitamin K, vitamin C, etc, or something that changes the pH of the digestive tract so that they absorb less of the calcium they are eating.

Researchers tend to hold most of the things constant and change just one or just a few variables - change one (or a few) of the pieces of a given puzzle, if you will. But there could be more puzzles - combinations with many the pieces very different.

 

[U_Stormcrow]

I think there is something to what you are saying about calcium being one piece of the puzzle.

I've been doing quite a lot of research about osteoporosis in people and have a dairy farm background. One of the things about calcium is that what else is eaten when calcium is eaten has a lot to do with how much of the calcium is absorbed by the digestive system. In people and cattle, anyway. I assume also in chickens. So, your feral birds may be able to eat much higher amounts of calcium without detrimental effects than the studies indicate if they are also getting different amounts of vitamin D, vitamin K, vitamin C, etc, or something that changes the pH of the digestive tract so that they absorb less of what they are eating.

Researchers tend to hold most of the things constant and change just one or just a few variables - change one (or a few) of the pieces of a given puzzle, if you will. But there could be more puzzles - combinations with many the pieces very different.

What kind of Calcium matters. non-phytate Phosporus matters A LOT. Some vitamins matter.

Time, Age, and Dosage matter.

and there's some failure to diagnose as well.

 

[saysfaa]

Another possibility is you aren't seeing quite what you think you are seeing.

Are they pecking the coral? Or bits of edibles on the coral. If they are pecking the coral itself, do all parts of the coral have the same calcium composition?

Are they as healthy as you think they are? As prey animals, they are very good at hiding ill health. And several of the ill effects of too much calcium are quite silent and/or attributable to other things with casual observation.

 

[saysfaa]

Another part of what else is being eaten is that the calcium that is absorbed is handled differently within the bones, blood, kidneys, and maybe other tissues depending on what else is going on in the body (which is usually related to nutrients in this case). Milk fever is not a calcium deficiency. Neither is osteoporosis. Well, usually, in both cases, anyway. Both are the results of where the calcium is in the body and what it is doing that is more important than being in the blood (during milk fever) or bones (during osteoporosis).

 

[saysfaa]

I lean toward all of the above are factors. Probably, any one factor could be all of the difference in some cases but most a probably a combination of these and others.

 

[BlindLemonChicken]

Are they pecking the coral?

I would be interested to know this as well. They might be eating the polyps on the calcium carbonate skeleton of the coral reef. I imagine they access the reef when the tide is very low? In which case there are also a bazillion creepy crawly crabs and other sea critters that I’m sure chickens find delicious and easy to catch. I know you (@CabritaChicks) have more observational experience with these feral chickens than we possibly can so I am sure you have watched them so you can tell us what leads you to believe they are consuming the coral skeleton itself. Very interesting discussion. I have noticed my pullets eating the “oyster shell” i have left out for the laying hens although none of them are laying yet. I just assume they are getting ready to lay and know what’s good for them. They are also free range and have been eating clover. I have been doing free-choice oyster shell for years not because of chicks but because of various aged hens and lower-production breeds. Now I have a rooster as well. I haven’t noticed him digging into the calcium.

 

[ColoradoChicken89]

TBH my biggest thing is, it's that chick starter/grow or even all flock feeds DO have calcium, just a lot less than layer feeds. Its around .8-1.8% calcium for starter/grower typically, similar for all flock feeds, whereas layer feeds have closer to 3-4%. So it's not like they are adviced to have 0 calcium, it's just at lower rates when all they have is bones and beaks.

So the thing is, are the wild chicks getting around 1-2% of their diet to be calcium? Because if it is, it's they are getting essentially the same amount of calcium as a chicken fed on commerical chick starter/grower, it would essentially just look a little different. Which is understandable because they wouldn't have a diet that is scientifically made to have the right amount of calicum per bite, so they would have to have a legit source for that small bit of calicum.

Now if you could prove they ARE getting closer to 3-4% caclium (or more) of their diet, my question would be then, how many of these wild birds have been necropied for kidney and various other issues? Likely not many... Which would beg to then ask, how do we know these chickens DON'T have kidney or various other issues, but we just don't know, because it's not like there are obvious outward signs to a dead chicken with kidney issues unless you cut it open and look at the kidneys.

Then again, even after all of that, if you could prove they are getting 3-4% as chicks AND didn't have any kidney issues, you could also question how much genetics have to do with that. Wild and feral bird populations are known to have unique genetic characteristics that are just unique to them specifically, and we would to study those differently to really know how that compares to the domesticated version.