Can Baby Chickens Eat Adult Chicken Feed? Not Layer Feed, and Here’s Why

My call: no, not if the adult feed is layer feed. Chicks and growing pullets stay off it until about 18 to 20 weeks, or their first egg, whichever comes first. The thing is, adult chicken food can mean three different bags at the feed store. Layer feed is the one to keep from them. An all-flock or flock raiser feed is made to be fed from hatch, so check its label, and you’re most likely fine. Scratch isn’t a complete feed at all, and it waits. Here’s the short reason on layer feed. It’s built for hens putting calcium into eggshells, so by my math on Purina’s tags, its layer feed carries about three to four times the calcium of its chick starter (and a little less protein). Merck’s vet manual says “It is critical not to feed layer diets to nonlaying, growing birds”. The reason it gives is “the inadequate protein concentrations and high calcium content (3.5–6%)”, which “can result in irreversible renal damage”. Renal means the kidneys.

I rewrote this page from 17 sources, all listed at the bottom. The vet lines are from two Merck Veterinary Manual pages, one on backyard flocks and one on gout. The feed numbers come off three Purina feed tags: two for young birds (Start & Grow and Flock Raiser), and Layena, the layer feed. Four Purina how-to pages by Patrick Biggs, Ph.D., give the timing and the switch. Oregon State’s guide by James Hermes sorts out the feed types. Dr. Jacquie Jacob of the University of Kentucky wrote the extension.org page I used on feeding for eggs. The laying hen lines are from Alabama Extension, and the chick lines are Cackle Hatchery’s. The four trials ran in Poultry Science (three on young pullets, one on young chicks), and I read them as PubMed abstracts.

A word on the photos. Five are Tamsin Cooper’s, and three of Tamsin’s titles give the young bird’s age. The one up top is titled as a 4-week-old chick out with the flock, from 2019. The chick beside the white hen is titled 4 weeks old too, and it was shot two days before the one up top, while the buff pullet is 15 weeks. The two young birds on the plank are from 2013, and that title is just “chicks4nov5”, so no age there. The blue hen’s title is just a file number, so I can’t tell you her age or what she eats either. The eggs in the nest box are Lance Cheung’s, taken for the U.S. Department of Agriculture at an organic farm in Maryland in 2013. I didn’t find a real photo of a dish of oyster shell or a bag of layer feed that passed my checks, so neither one is pictured.

The old page opened with a scene I can’t back up. It started with collecting eggs and spotting “the little brood of new chicks cheeping loudly beside the mother hen”. Then the feed bin turned out to hold only “a big bag of the standard layer pellets I give to the full-grown hens”. And there was “I don’t think I’ve ever seen the mother hen herself eating feed pellets either”. I can’t show you any of that happened, so it’s gone. So is “It was time to do some research”, since that research was never named. But the question underneath it is a fair one, and you’ll find the broody hen part in its own section below.

Plenty of the numbers were wrong, too. On protein, it said “I’m talking 25-30% of their diet”. Purina’s Start & Grow guarantees 18%, and Jacob’s table puts chick starter at 20 to 22%. It said “Their starter feed contains around 1.5% calcium – way more than your average layer feed”. Honestly, that’s backwards. Purina’s starter tag says 0.75% to 1.25% calcium, and its layer tag says 3.25% to 4.25%. It said layer “calcium can be as low as 3%, which definitely ain’t enough to build strong skeletons at a young age”. Nope. For a chick, that much calcium is the problem, not the fix. Its plan for running short of starter was to “mix about 1 part starter to 3 parts layer chow”. That puts your chicks mostly on layer feed. And “Come 6 weeks you can start transitioning them fully to layer feed” is way early. Purina and Oregon State put the switch at 18 to 20 weeks or the first egg, and Jacob says about 20 weeks. The line “So while layer feed is fine as a supplement” went too.

A few more had to go. “Grit and oyster shell should also be offered once chicks are a week old” is out. Cackle Hatchery and Purina both say chicks on a complete starter don’t need grit. And oyster shell is extra calcium for laying hens. “Dissolving electrolytes in their water weekly” is out as well. Cackle says you can add them for about a week, to help chicks over the stress of hatching in an incubator and shipping, and “After that, provide only fresh, clean water”. Moving chicks in with the big birds “Once fully feathered at 6 weeks” runs into Purina, which says to keep them apart until they’re the same size. I also cut the brooder heat schedule and the line that “Chicks are tropical creatures after all”. The health list went, starting with “pasted vent or caked poop – can indicate coccidiosis”. So did the rooster aside about “once sexually mature at 5-6 months”. Most of it wasn’t about feed, so it doesn’t belong on this page.

The short version.

• My call: no layer feed for chicks or growing pullets. It waits until about 18 to 20 weeks, or the first egg (Purina, Oregon State, Jacob).
• By my math on Purina’s tags, its layer feed carries about three to four times the calcium of its starter. Layena says 3.25% to 4.25%, against 0.75% to 1.25% on Start & Grow.
• Merck says high-calcium layer diets “can lead to irreversible renal damage” in growing birds. Trials found urinary stones in young pullets and kidney lesions in young chicks.
• An all-flock or flock raiser feed is fine from hatch, if its label says so. Purina’s Flock Raiser tag does.
• Scratch isn’t a complete feed. Purina would have scratch and treats wait until 18 weeks if you can.
• Chicks under a broody hen, or in a mixed flock? Everyone eats an all-flock feed like Flock Raiser. The layers get oyster shell in a feeder of their own (Oregon State, Purina).
• Switch over four or five days, with the two feeds mixed evenly (Purina).
• My call: if a chick got into the layer feed for a day or two, put the starter back today. If a chick looks sick, call a vet who sees poultry.

Adult Feed Is Really Three Different Bags

Walk into a feed store and you’ll find the bags for grown birds aren’t all the same thing. Here’s how my sources sort them, plus the in-between bag for growing birds.

• Layer feed. This is the one for hens that are laying. Oregon State’s guide says “Layer feeds contain about 16 percent protein and extra calcium (3 to 4 percent)”. Purina’s Layena tag is plain about who it isn’t for: “Do not feed to birds less than 18 weeks of age. Do not feed to male birds”.
• All-purpose feed, sold as all-flock or flock raiser. Oregon State says “All-purpose feeds are formulated as the sole ration for chickens of all ages, from hatch through egg laying”. Purina’s Flock Raiser tag says to feed it to chickens at hatch. It guarantees 20% protein and 0.80% to 1.30% calcium.
• Grower or developer feed. That’s the in-between bag, not an adult one. Oregon State calls the two “virtually interchangeable”, for birds from 6 weeks old until they start laying.
• Scratch grains. These aren’t a complete feed. Jacob writes “When scratch grains are fed with complete feeds, they dilute the nutrition levels in the carefully formulated diets”.

So if the bag in your shed says layer, the answer is no. If it says all-flock or flock raiser, check the label for the ages, and you’re most likely fine. Jacob is a bit more careful about it. Jacob’s feed table lists an all-purpose feed for all ages, with a note to “Feed only if a single feed is available and use during the entire growing period”. Now, the catch with all-purpose feed comes once your hens lay. Oregon State says to “read the label carefully”, since hens on it “will generally not receive enough calcium for proper eggshell formation”. So they get oyster shell on the side. More on that below.

Layer Feed Carries Several Times the Calcium

Calcium is most of the story here. A laying hen needs a lot of it, because it goes into her eggshells. Merck says “formation of a typical egg requires approximately 2 g of dietary calcium”. A growing chick needs far less. Here’s what my sources give for each.

• Merck: diets for growing birds “are typically 0.8–1.2% calcium”, and “Laying birds require 3.5–6% calcium”.
• Purina’s tags: Start & Grow guarantees 0.75% to 1.25% calcium, and Flock Raiser 0.80% to 1.30%. Layena, the layer feed, guarantees 3.25% to 4.25%.
• Jacob: “Laying mashes typically contain 2.5% to 3.5% calcium. Growing chickens require only 1.2% calcium in their feed”.
• Oregon State and Alabama Extension both put layer feed at 3 to 4% calcium.

By my math on Purina’s own tags, its layer feed carries about three to four times the calcium of its starter: the middle of Layena’s range is 3.75%, and the middle of Start & Grow’s is 1%. That’s a big gap. Purina’s page on teenage chickens says to look for a starter-grower with “no more than 1.25% calcium for laying breeds”. It also says “Too much calcium can have a detrimental effect on growth”. Layer feed is lower in protein, too. Layena guarantees 16% protein, against 18% for Start & Grow and 20% for Flock Raiser.

Cackle Hatchery’s answer to this exact question is to “never feed layer ration to baby chicks”. It says starter “is higher in protein and lower in calories than layer ration”. And it warns that “the higher calcium content in layer ration can seriously damage young kidneys”. Merck’s backyard flock page says the same thing in vet terms: “Nonlaying, growing birds should not be fed high-calcium layer diets, which can lead to irreversible renal damage”. That’s why layer feed for chicks is on the list of what not to feed chickens too.

What the Trials Found in Young Pullets and Chicks

If you think this is just a feed company playing it safe, look at the trials. Back in the 1980s, poultry scientists fed young pullets and chicks layer ration, or a feed just as high in calcium, on purpose, to see what it did to their kidneys. I read these as PubMed abstracts, not full papers, so here’s only what the abstracts say, and you can click through to each one at the bottom.

• A Penn State trial raised 800 White Leghorn chicks on starter. At 6 weeks, half went on a grower ration with about 1.0% calcium, and the other half got a layer ration with about 3.25%, until 18 weeks. The abstract says “The layer ration also caused an 11.5% incidence of urolithiasis”. It also found more “kidney asymmetry in 18-wk-old pullets” on the layer ration.
• Wideman and Cowen fed young chicks, not just pullets, a pullet grower with 1% calcium or a layer ration with 3.25%, and a third group got that layer ration with an acidifier added. Their abstract says “The layer ration induced a 60% incidence of kidney lesions”. It also “caused a 25% reduction in the number of filtering nephrons”. Nephrons are the kidney’s filters.
• A third trial split 1,000 White Leghorn pullets into four diets from 50 days old. They got normal or high calcium (1% or 3.25%), and normal or low phosphorus. With normal phosphorus, 1% of the high-calcium pullets had urolithiasis at 18 weeks. None on normal calcium did. At 18 weeks, 368 of them were necropsied (examined after death), and the rest went on a commercial layer ration until 51 weeks. By then, none of the hens raised on normal calcium and normal phosphorus had it, but 12% of those raised on high calcium with normal phosphorus did. Low phosphorus pushed it up: 14% on high calcium at both ages, and 2% on normal calcium by 51 weeks (none at 18).

Urolithiasis means stones. Merck’s gout page says swollen ureters “often contain brittle, white, staghorn calcium urate calculi or uroliths”. It says “Progressive obstruction of the ureters by uroliths causes kidney atrophy”. The same page lists “ingestion of feed containing > 3% calcium by nonlaying chickens” among its causes. Some birds in those first two trials were also given a bronchitis virus on purpose, since the researchers were studying both. The numbers above are the ones the abstracts give for the layer ration. Honestly, that third trial is the one that sticks with me. On high calcium with normal phosphorus, the harm looked small at 18 weeks (1%). Then it showed up later, in the laying hens (12%).

Now the other side, because it matters for timing. A Cornell trial fed pullets 3.5% calcium starting anywhere from 14 to 18 weeks old, up to 20 weeks. The abstract found no “significant adverse effects” on how the pullets grew or ate, or on deaths, while they were growing. Kidney weight and blood uric acid weren’t significantly different from the control birds either. It adds that “Sexual maturity was advanced”. So in that trial, 2 to 6 weeks of it right before laying did no significant harm to growth, kidney weight or uric acid, or to laying later on. The two trials that found harm and gave a start age (6 weeks and 50 days) kept the high-calcium feed going for 11 to 12 weeks, by my math.

Maybe your chicks already got into the layer feed. None of my sources tested a day or two of it in a chick. The three abstracts that give a length ran for weeks. My call: put the starter back today, and don’t lose sleep over a day or two. If a chick looks sick, call a vet who sees poultry.

Chicks Under a Broody Hen, or in a Mixed Flock

This is the setup the old page started with, and it’s the one that trips folks up. Say a hen hatches a clutch in your coop, and the only feeder you’ve got holds layer pellets. Merck’s backyard flock page points right at it: “One of the most common problems in mixed-age flocks is urolithiasis (gout)”. Of the causes it lists, the one it says happens more often is “feeding a high-calcium (adult layer) diet to an immature bird”.

The fix is to turn it around. Everyone eats an all-flock feed that’s fine for the chicks, and your laying hens get their extra calcium on the side. Purina’s page on teenage chickens says “Meat birds and mixed flocks should be fed a diet containing at least 20% protein”. Flock Raiser is sold for pretty much this job. Purina’s page for it says “Sustain an entire mixed flock of poultry”. Its tag says to give laying birds oyster shell on top. For the oyster shell, Oregon State says to “provide a separate feeder to allow for free-choice feeding (the hen decides if she needs calcium)”. I came down the same way in the Rhode Island Red feeding guide. And the post on raising baby chicks lands close, with one feed for the whole flock (grower, on that page) and oyster shell on the side.

Roosters and cockerels never lay, so they never need layer calcium. Purina’s Layena tag says “Do not feed to male birds”. Alabama Extension is softer about it, and says most backyard flocks can feed roosters what the hens eat. Then it adds “Rarely the rooster’s extra consumption of nutrients (especially protein and calcium) can negatively affect the kidneys”. So my call is that the all-flock bag with oyster shell on the side covers a rooster too.

How long does the whole flock stay on the all-flock feed? My call: until the youngest reach the age you’d switch them anyway. That’s around 18 to 20 weeks, or their first egg. With no roosters, everyone can move to layer feed then. With a rooster, I’d stay on all-flock with oyster shell. And if your chicks came from a brooder, not a hen, Purina has a rule for that. It says “Keep young chicks separate from older birds until they reach the same size – typically around 16 weeks of age”. The post on moving chicks into the flock goes through the move itself, with its own rule of thumb on size.

Switch at 18 to 20 Weeks, or at the First Egg

My sources land in about the same window for layer feed.

• Purina: “Switch laying hens to a complete chicken layer feed when they start laying eggs around 18 weeks of age”.
• Oregon State: “Start feeding layer feeds at about 18 to 20 weeks of age or when the first egg is laid, whichever occurs first”.
• Jacob: “Once your chickens start laying eggs (around 20 weeks of age) they should be switched to a layer feed”.
• Merck calls anything under 16 to 18 weeks old the prelay period.

Until then, Purina’s chick feed page says to keep them on the same starter “from day 1 to week 18”, or on a grower made for that age. If your chicks started on a medicated starter, it says to “keep feeding the same medicated feed until their first eggs”. And pullets can be late. Alabama says slower growing breeds like the Rhode Island Red and the Plymouth Rock, along with day length and season, “can delay first egg production”. It adds “Generally, most pullets will lay their first egg at 20 to 25 weeks”. It says poor nutrition or disease can hold a pullet back too. That’s why I like Oregon State’s “whichever occurs first”, since you don’t have to wait on a late egg. The beginner’s guide to raising egg-laying chickens says the same thing: layer feed waits until your birds are close to laying.

Make the switch slowly. Purina says “We mix the starter-grower feed and layer feed evenly for four or five days”. Match the form, too: “If birds are used to crumbles, start with a crumble layer feed. The same goes with pellets”. Turns out it doesn’t take long, since Purina says “most birds adjust within a couple days”. It also says “Ideally, make your layer feed decision by week 16 of age, so you’re ready to make the transition at week 18”. That gives you time to find the bag before you need it.

Hold the Grit and Oyster Shell, and Let Scratch Wait

The old page told you to put out grit and oyster shell for week-old chicks. Here’s what my sources say instead.

• Grit. Cackle Hatchery says “Chicks that are fed only starter do not need grit”. Purina agrees that chicks on a complete starter “do not need grit”. Once they eat anything fibrous, Cackle says “they need grit to help with digestion”.
• Oyster shell. It’s extra calcium for laying hens, not chicks. Jacob writes “Oyster shell should not be used as grit since it is too soft and does not aid in grinding”. Then: “growing chickens have a lower calcium requirement, and too much calcium can adversely affect their kidneys”. Even for hens on a good complete layer feed, Alabama says “supplementing a layer flock with oyster shell is probably unnecessary”. It also says oyster shell is cheap, and that giving it to hens “will not have negative consequences”.
• Scratch and treats. Purina says “Ideally, wait until birds are 18 weeks old before introducing treats and scratch”. If you can’t wait, it says at least 12 weeks, and it caps them at “no more than 10% of total daily intake from treats”. And Jacob says scratch dilutes a complete feed, as above.

My sources don’t agree on treats for chicks, so here’s the spread. Cackle Hatchery says treats can start at about two weeks, in moderation. Alabama wants a complete starter-grower as the only food from 1 to 6 weeks. Purina says 18 weeks ideally and 12 at the least, though the same page later suggests scratch as a treat once birds go out to the coop at 6 to 8 weeks. In the post on baby chicks and rice I went with Alabama’s 6 weeks. Scratch I’d hold to Purina’s 18 weeks, as my call.

Sources

• Yuko Sato, Merck Veterinary Manual: Management of Backyard Poultry.
• Rocio Crespo, Merck Veterinary Manual: Urate Deposition (Gout) in Poultry.
• Purina Animal Nutrition: Purina Start & Grow, feed tag.
• Purina Animal Nutrition: Purina Flock Raiser Crumbles, feed tag.
• Purina Animal Nutrition: Purina Layena Pellets, feed tag.
• Patrick Biggs, Purina Animal Nutrition: Six Milestones of Chicken Growth Stages.
• Patrick Biggs, Purina Animal Nutrition: How to Switch to a Chicken Layer Feed.
• Patrick Biggs, Purina Animal Nutrition: Chick Starter Feed, What to Feed Baby Chicks for a Healthy Life.
• Patrick Biggs, Purina Animal Nutrition: Is Your Chick a Pullet or Cockerel? Frequently Asked Teenage Chicken Questions.
• James Hermes, Oregon State University Extension (a Pacific Northwest Extension publication): How to Feed Your Laying Hens, PNW 477 (September 2016).
• Jacquie Jacob, University of Kentucky, on extension.org: Feeding Chickens for Egg Production in Small and Backyard Flocks.
• Wilmer Pacheco with Joseph Gulizia and Kevin Downs, Alabama Cooperative Extension System: Feeding the Laying Hen, ANR-2913.
• Cackle Hatchery: What to Feed Baby Chicks.
• Glahn, Wideman and Cowen (Penn State), Poultry Science 1988: virus and high dietary calcium on the kidneys of White Leghorn pullets (PubMed abstract).
• Wideman and Cowen, Poultry Science 1987: kidney damage in immature chickens from excess calcium (PubMed abstract).
• Wideman with Closser, Roush and Cowen, Poultry Science 1985: Urolithiasis in pullets and laying hens (PubMed abstract).
• Keshavarz (Cornell), Poultry Science 1987: a high calcium diet late in the growing period (PubMed abstract).

Sources checked November 3, 2026. Jacob’s extension.org page turned away a plain download, so I read it in a browser. I read the four trials as PubMed abstracts, not as full papers. Calling an all-flock feed fine from hatch rests on Oregon State’s guide and Purina’s Flock Raiser tag, so read your own bag. Putting the starter back after a day or two of layer feed is my call. So is keeping a mixed flock on an all-flock feed until the youngest reach laying age. Covering a rooster with all-flock and oyster shell is my call too. Holding scratch to 18 weeks is my pick among my sources. And every ratio I worked out from the feed tags or the trials is my math. We aren’t vets. If a chick or a hen looks sick, call a vet who sees poultry.

Related read: How to Raise Chickens for Eggs — Instant PDF download. Secure checkout by Stripe