Most lists of foods you shouldn’t give chickens run long. This page used to be one of them, with 32 sections and a hazard score for every food. When I went back to the vet manuals and the extension pages, the list got shorter. And the order changed.
Here’s the part that stuck with me. The Merck Veterinary Manual’s chapter on poisonings in poultry barely touches kitchen scraps. Its key points name disinfectants and rodenticides, plus insecticides and feed additives, as “common causes of poisoning in poultry”. That’s not your kitchen. That’s your shed. Avocado and chocolate, the foods most lists open with, don’t have an entry in that chapter at all.
So I read 20 sources for this page, and you’ll find them all at the bottom. That’s seven Merck chapters, seven extension pages from five universities, four Feedipedia entries on feeds, the FDA’s chapter on bean lectins and one study of caffeine in eggs. I sorted the foods by how strong the case is for chickens, not for dogs or parrots. Where the sources split, you get both sides and the one I’d go with. If you’re checking one food, our free Can Chickens Eat It? checker has the rest.
The short version.
- Moldy feed and moldy scraps are out, every time. Once mold toxins form, they stay in the feed.
- Salty food is out: chips, fast food and salted leftovers. So is the salt block you put out for other livestock.
- Raw or dried beans are out. Cooked beans are fine if they really boiled, and a slow cooker doesn’t count.
- Green potato skins and sprouts are out, and so is the potato plant. Plain cooked potato is fine in small amounts.
- Avocado skin and pits are out, and so are the leaves. The flesh is where the sources split, and I’d skip it.
- Chocolate and cocoa are out, and coffee goes with them. That includes cocoa-hull mulch and your spent coffee grounds.
- Fatty scraps and alcohol are out. Go easy on onions, and keep rhubarb leaves out of reach.
- The worst poisons in the vet book aren’t food at all. Think lead paint chips, zinc, antifreeze or rat bait.
- Chicks don’t get layer feed. And a laying hen’s treats stay near 10 grams a day, all of them added together.
Moldy Feed and Moldy Scraps: Out, Every Time
If you only keep one rule from this page, keep this one. Molds growing on the grain your hens eat make toxins, and Merck’s poultry chapter lists several of them. Aflatoxin is the best known. In poultry it brings “decreased weight gain, drops in egg production” and more, and Merck says ducks and turkeys are “particularly sensitive”.
The trouble is that you can’t treat it away. Merck’s chapter on mycotoxins says that once formed, the toxins “are chemically stable and persist” in the grain, right through to the finished feed. And antifungal agents added to feed “have no effect on toxin already formed”. So a bag that went bad stays bad, whatever you add to it. Toss it.
Mold doesn’t need a feed mill, either. The same chapter says the toxins “can form in decayed, crusted feed in feeders”. It adds that temperature swings put condensation in storage bins. So the crust in the bottom of your feeder counts. Clean it out before you top it up.
Merck’s backyard poultry page covers the storage side. Keep feed “in a dry, cool area” and use it by its expiration date. Most feeds expire in 3 to 6 months, Merck says, or “as little as 2 months in the summer”. A big bag from the feed store that’s cheaper by the pound isn’t a deal if it outlasts its date.
For scraps, UF/IFAS Extension in Holmes County has the plainest test I found. It says, “If food is moldy enough that you would not eat it yourself, do not feed it to your chickens”. Colorado State and UC Davis say the same in fewer words. Moldy bread and fuzzy fruit go in your trash, not the run. (I went through the grain side of this in the post on horse oats.)
Salt: Chips, Fast Food and the Livestock Salt Block
Salt is on every list, and here the vet book has real numbers. Merck recommends adding 0.5% salt to a chicken ration. It says amounts over 2% “are usually considered dangerous”. By my arithmetic, that’s only four times the recommended level.
If you raise chicks, they’re the touchiest. Merck says chicks under 21 days old are more susceptible, because their kidneys aren’t fully developed. The signs it lists are labored breathing, lethargy, swollen fluid-filled bellies, watery droppings and wet litter. If the bedding in the brooder turns soggy overnight, that’s one more reason to look at what went in the feeder.
The salty foods UF/IFAS names are the ones you’d guess: chips, fast food, canned foods and heavily salted leftovers. Merck adds one I hadn’t thought about. It reports poisoning from “rock salt or salt provided for other food animals”. So if you keep goats or a steer, their salt block belongs where the hens can’t reach it. The same goes for a bag of rock salt by the door in winter.
Cheese is a salty one too, and I worked through its numbers in the post on chickens and cheese.
Raw or Dried Beans, and Why the Pot Has to Boil
Dry beans straight from your pantry are out. UF/IFAS names the toxin, phytohemagglutinin (PHA for short), and says cooked beans “are generally safe”. Colorado State says to avoid “under cooked or dried beans”. UC Davis puts raw beans on its avoid list.
Feedipedia is a feed database from four research and farm bodies, the FAO among them. It says poultry are “sensitive to antinutritional factors contained in raw common beans, though less so than pigs”. In broiler chickens fed raw beans, the studies it cites found damage in the liver and kidneys. Beans cooked in water did better in those trials than toasted ones.
Here’s the catch I didn’t expect. Warm isn’t the same as cooked, and warm can make it worse. Feedipedia, citing the FDA, says cooking above 100°C (212°F) brings the lectin down. But cooking at 80°C (176°F) “increased lectin content and toxicity”.
The FDA’s own chapter spells it out. Boiling beans for 10 minutes at 100°C destroyed the toxin in one study, and the FDA tells people to boil them for at least 30 minutes. It also says not to use slow cookers, because casseroles cooked in them often reached only 75°C (167°F) or less. Those numbers are for people. But if beans go to your flock, give them the same real boil. Then you’re fine.
Potatoes: Green Skin and Sprouts, Plus the Plant Itself
Potatoes carry glycoalkaloids, mainly solanine and α-chaconine. Feedipedia says the level is “3 to 10 times greater in the peel than in the flesh”. Light pushes it up a lot in sprouts and green peel, especially when it’s warm. It describes animals poisoned on “peelings and sprouts from old potatoes left at sunlight”. The signs run from trembling and staggering to diarrhea. At worst, it’s convulsions and sudden death.
NC State’s plant pages go further. “All green parts of the potato plant are inedible,” they say. The toxin shows up in the sprouts and stems, in the leaves and berries, and in the green skin. The berries get a warning in capital letters. So when you clear the potato patch, don’t toss the vines over the run fence. UC Davis puts the leaves of the whole family on its avoid list: tomato, pepper, potato, eggplant or any other nightshade.
Colorado State says to be cautious with potato peelings. And Feedipedia says frozen, dirty or rotting potatoes “should not be fed to livestock”.
Cooked potato is a different food, though, and you can share it. Raw potato carries a protease inhibitor, and Feedipedia says heat breaks it down, so it’s “absent in cooked potato”. UF/IFAS calls plain cooked potatoes “generally safe in moderation”. Researchers have even fed cooked potatoes to poultry at up to 40% of the ration. Laying hens did fine on 15% potato meal and laid fewer eggs at 20%.
I wouldn’t take any of that as a reason to fill your feeder with spuds. It just means a few plain cooked leftovers, with no green on them, aren’t a worry. A sweet potato isn’t a potato, by the way, and its skins have their own page.
Avocado: The Sources Split, So I’d Skip It
This is the one where the experts don’t agree. Merck’s avocado chapter puts chickens and turkeys on its list of susceptible animals. In the next breath, it says caged birds “seem more susceptible to the effects of avocado, whereas chickens and turkeys seem more resistant”.
The caged-bird numbers are grim. Merck says budgerigars fed 1 g of avocado fruit showed agitation and feather pulling. And 8.7 g of mashed fruit killed them within 48 hours. In birds, the signs are lethargy, labored breathing, poor appetite, swelling under the skin of the neck and breast, and death. There’s no test to confirm it, and the heart damage “can be extensive, especially in birds”. Merck also says the leaves are the most toxic part.
The extension pages don’t line up, either. Colorado State says the skins and pits “are toxic to chickens” but “The avocado flesh is fine”. UF/IFAS says the flesh is “less dangerous” and still best avoided entirely. UC Davis just says to avoid avocado. Merck’s page for bird owners lists it among household hazards, too.
My call is to skip it. I’d guess chickens are tougher than budgies, and Merck seems to agree. But nothing I read gives a safe amount for a hen, and plenty of treats don’t come with a warning. Your hens won’t miss it. If you grow avocados, keep fallen leaves and pits out of the run as well.
Chocolate and Coffee, Cocoa Mulch Included
Chocolate’s problem is a pair of methylxanthines: theobromine and caffeine. Merck says poisoning “occurs most commonly in dogs, although many species are susceptible”. It also reports deaths in livestock fed cocoa byproducts and in animals that ate mulch made from cocoa bean hulls. Feedipedia says untreated cocoa beans and oil cake “can be hazardous to poultry”.
How much is in it depends on the chocolate. Merck’s figures, per gram:
- Cocoa powder: 28.5 mg.
- Unsweetened baking chocolate: 15.5 mg.
- Cocoa bean hulls, the stuff in the mulch: 9 mg.
- Semisweet and dark chocolate: 5.3 to 5.6 mg.
- Milk chocolate: 2.3 mg.
- White chocolate: 0.04 mg, which Merck calls “a negligible source”.
So cocoa powder carries about 12 times what milk chocolate does, by my arithmetic. Merck gives doses for dogs only, and I didn’t find a dose for chickens in anything I read. So I won’t put a number on it for a hen.
The mulch is the one to watch if your flock free-ranges, since hens scratch through garden beds. Merck notes that some cocoa hull mulches have had the methylxanthines taken out during manufacturing. Unless the bag says so, keep cocoa mulch out of any bed your birds can reach.
Coffee belongs here too. UF/IFAS says “Coffee grounds, energy drinks, tea bags, and other caffeinated products are dangerous for chickens”. And a 2024 study in the journal Animals fed hens caffeine in their rations. Caffeine and three compounds the body makes from it all turned up in the eggs. There was about twice as much in the white as in the yolk. So the caffeine a hen eats doesn’t stop with her.
The Rest of the Usual List: Onions, Rhubarb, Citrus, Fat, Alcohol
Onions. Merck’s onion and garlic chapter describes a kind of anemia in cats and dogs, and in farm animals fed onions. Cats are the most susceptible, and chickens aren’t named. UF/IFAS says large amounts can damage red blood cells and “may cause anemia in chickens”. It says onions may change the taste of the eggs, too, while small amounts “are usually not harmful”. Colorado State says to avoid them. So if you tossed out leftovers with a bit of onion in them, it isn’t an emergency. But I wouldn’t hand your hens a bowl of onion trimmings.
Rhubarb. The leaves are the part to keep away. NC State’s plant page marks rhubarb toxic only when large amounts are eaten. It names oxalates among the toxins and says the leaves and roots are the most toxic parts. Colorado State and UC Davis both put rhubarb on their avoid lists. So if you grow rhubarb, keep the patch on the far side of the run fence.
Citrus. Here the extension advice and the feed research part ways. Colorado State says scraps shouldn’t “have citrus”. But Feedipedia says limonene, the oil that gives citrus peel its smell, “is practically non-toxic to birds and mammals”. In one study it cites, laying hens on 10% dried citrus peel kept laying with no real harm to egg weight. A 15% diet cut how well they used their feed. The seeds are the bigger worry: lots of them can make citrus pulp toxic to non-ruminants at just 2.5% of the diet. So citrus isn’t the poison some lists make it. I’d still keep it small and seedless, since Colorado State says no.
Fat. Fat scraps get a stronger warning than most foods on this page. Merck’s backyard poultry page says they “promote the development of fatty liver and acute death from liver rupture”. UC Davis says chickens “don’t require high amounts of fat”. So your bacon grease and the trimmings off the roast stay out of the scrap bucket.
Alcohol, apple seeds, fruit pits. UF/IFAS says chickens should never get alcohol “or heavily fermented foods”. UC Davis lists alcohol and tobacco as toxic. And UF/IFAS says apple seeds and fruit pits hold compounds that “release cyanide when crushed or chewed”. So core the apples and pit the peaches before they go out.
The Worst of It Isn’t Food: Lead Paint, Zinc, Antifreeze, Rat Bait
Go back to Merck’s poultry poisonings chapter and look at what it covers. Lead, zinc, ethylene glycol, rodent bait, insecticides. For a flock that ranges the yard, those are the poisons with real numbers attached.
Lead. Merck says lead poisoning in backyard birds “usually is caused by consumption of old flakes of lead-based paints”. Lead objects are the other big source, along with a few other things, from lubricants to electronics. Metallic lead “at ≥ 7.2 mg/kg is lethal”, and young birds can die within 36 hours. And it can reach your kitchen. Merck says birds with lead poisoning “may accumulate lead in eggs”.
If your coop or barn might have old lead paint on it, the University of Maine’s extension has the most practical list I found. It comes from a New York City study.
- Feed in feeders, and don’t scatter scratch or scraps on bare ground where the soil may carry lead.
- Keep the birds away from buildings painted with lead-based paint.
- Don’t feed them unwashed garden scraps from high-lead soil.
- Think about a calcium supplement, which “may help to reduce the amount of lead that gets into chickens’ eggs”.
- Get the soil tested, and ask for a lead screen.
Zinc. Merck says backyard birds may swallow zinc-coated metal objects and some rubber products. Seizures and green diarrhea are among the signs it lists, along with fewer eggs. So if you drop screws or washers on the coop floor, pick them up. All of them.
Antifreeze. It’s ethylene glycol, and Merck says the same stuff is in transmission fluid and solvents like rust remover. “Free-ranging chickens can accidentally ingest the liquid from these sources,” it says. The minimal lethal dose in poultry is 7 to 8 mL per kilogram of body weight. By my arithmetic, a 2 kg (4.4 lb) bird would need only 14 to 16 mL, about a tablespoon. If you change your own coolant, clean up the spills right away.
Rat bait. Merck says free-ranging backyard poultry may accidentally eat rodent bait. With the blood-thinning kind, it usually shows up as sudden death. Merck also says bait can be used safely around poultry houses, as long as it’s kept away from the flock. So any bait you set out for the rats has to sit where your hens can’t reach it. The same goes for granular insecticide on the lawn, since Merck notes that chickens will eat diazinon crystals.
Fire ants show up on some lists of foods not to feed chickens. They’re not a food, and they have their own page.
How Much Is a Treat? About 10 Grams a Hen
The last two items on this list aren’t poisons at all. They’re about how much, and who gets what.
Colorado State says treats “should make up no more than 10% of their daily diet”. It also says to give no more than the birds finish in 5 to 10 minutes, so you don’t draw in nuisance animals. (Think rats, or a raccoon at night.) Merck says an adult laying hen “should eat no more than 0.1 kg (0.25 pound) of feed per day”. Put those together and a hen’s treats come to about 10 grams a day, by my arithmetic.
Here’s why I’d stick to it. Merck’s backyard page names diluting a balanced ration with scratch or extra feed as one of the common problems in backyard flocks. UC Davis says it more kindly: “treat the scraps like a treat not like the main course”. A hen you fill up on treats eats less of the feed that was built for her. Our chicken feed calculator does the feed side for your flock’s size.
Chicks Don’t Get Layer Feed
Layer feed is for laying hens, and Merck is blunt about it. It calls it “critical not to feed layer diets to nonlaying, growing birds”, because the high calcium (3.5 to 6%) can cause kidney damage it calls irreversible. Its poisonings chapter adds that more than 3% calcium before laying starts brings on gout in pullets. Merck also lists feeding the wrong diet for a bird’s age among the common backyard mistakes. So chicks and growing pullets stay on a starter or grower feed. (Here’s how medicated and non-medicated starter compare.)
That’s the short list. Most of it you’d never mean to feed a hen in the first place. The ones I’d watch hardest are a crusty feeder and a flake of old paint, because the vet book puts real numbers on those.
Updated October 2026: rewritten from the sources below and checked line by line. The old version told a story about one keeper’s 12 hens getting sick from a cheap bag of moldy pellets, with a vet visit and probiotics. That’s gone, and so is every first-hand line. So is the hazard score for each food, which no source gives. It said chickens lack the enzymes for alcohol and caffeine. It said citrus peel blocks the throat and that dried fruit’s sulfites stop oxygen getting around. It also blamed cat food for gout. The sources I read don’t back any of that, so it’s cut. The same goes for its warnings on raw eggs, pickle juice, mushrooms, sugar or iron pills. Fire ants and wasps aren’t food, so they’re gone too. And its 17 illustrations are now real photos, each one credited under it.
Sources
- Merck Veterinary Manual: Poisonings in Poultry (Carmen Jerry, DVM; reviewed January 2024, updated September 2024).
- Merck Veterinary Manual: Mycotoxicoses in Poultry (Dulmelis Sandu, DVM; reviewed December 2023, updated September 2024).
- Merck Veterinary Manual: Management of Backyard Poultry (Yuko Sato, DVM; reviewed November 2024).
- Merck Veterinary Manual: Avocado (Persea spp) Toxicosis in Animals (Cristine Hayes, DVM; reviewed September 2024).
- Merck Veterinary Manual: Chocolate Toxicosis in Animals (Cristine Hayes, DVM; reviewed September 2024).
- Merck Veterinary Manual: Garlic and Onion (Allium spp) Toxicosis in Animals (Cristine Hayes, DVM; reviewed September 2024).
- Merck Veterinary Manual, bird owners: Household Hazards for Pet Birds (Laurie Hess, DVM; reviewed April 2025).
- UC Davis School of Veterinary Medicine and UC Cooperative Extension: Feeding your Flock (Dr. Maurice Pitesky and Dr. Nancy Reimers).
- UC Davis School of Veterinary Medicine: A Question of Lead (Poultry Science column).
- Colorado State University Extension: Raising Poultry the Organic Way: Disease Control and Feeding (Howard Enos; reviewed August 2025).
- UF/IFAS Extension Holmes County: 10 Foods You Should Never Feed Chickens (Kalyn Waters, with Jewellyn Owens; May 25, 2026).
- University of Maine Cooperative Extension: What do I do if my chickens consumed paint with lead in it? (New Farmers).
- NC State Extension Gardener Plant Toolbox: Solanum tuberosum (potato).
- NC State Extension Gardener Plant Toolbox: Rheum rhabarbarum (rhubarb).
- Feedipedia (INRAE, CIRAD, AFZ, FAO): Common bean (Phaseolus vulgaris).
- Feedipedia: Potato (Solanum tuberosum) tubers.
- Feedipedia: Citrus pulp, dried.
- Feedipedia: Cocoa (Theobroma cacao) beans and by-products.
- US Food and Drug Administration: Bad Bug Book, second edition (2012; the Phytohaemagglutinin chapter).
- Transfer of Caffeine and Its Major Metabolites to Chicken Eggs (Teixeira and colleagues, Animals, 2024; the abstract).
Sources checked October 26, 2026. The treat allowance and the cocoa ratio are my arithmetic from these sources, and so are the salt ratio and the antifreeze tablespoon. We aren’t vets. If you think a bird ate something on this list, call a vet who sees poultry.
Related read: How to Raise Chickens for Eggs — Instant PDF download. Secure checkout by Stripe
