Can Chickens Eat Onion? Is it Safe?

Everyone but the newest, greenest chicken keeper knows that these birds will eat just about anything.

Highly omnivorous, chickens have the most varied diet there is out of all the common species of livestock: All kinds of meat, every kind of bug and worm, plants, fruit and vegetables, including vegetables that people eat.

However, there are some vegetables that are highly contentious among keepers regarding their safety for chickens. By far the most contentious is the onion.

Some people say onions are completely safe and healthy, others say they are deadly poisonous for chickens. What’s the truth? Can chickens eat onions safely?

Chickens can only eat onions safely in very small amounts because onions have toxic compounds that cause anemia and other problems, including egg quality issues. However, some studies have shown that limited amounts of onions may benefit chickens.

This is one subject that is bound to get confusing, and seemingly anywhere you go on the internet you’ll find conflicting answers.

The best answer I can give you, and the one supported by much of the scientific research, is that onions are generally harmful to chickens unless eaten in strict moderation.

I’ll tell you everything you need to know about onions as they concern your chickens below…

Bottom Line: Onions Contain Toxic Compounds

Before we go any further, we must clear up one thing: onions are indeed toxic to chickens. This is because they contain significant amounts of disulfide and sulfoxide compounds.

These compounds cause damage to the circulatory system by disrupting red blood cells, the same blood cells that carry oxygen to the tissues of the chicken.

In a high enough dose, or with repeated ingestion, these compounds will result in anemia, along with other negative outcomes in chickens from other components in the onion.

So, knowing that onions contain these toxic, harmful compounds, how is it ever okay to feed them to chickens? Like many things, the difference between something beneficial and something poisonous often comes down to the dosage, and onions are no different.

However, it might not take very much onion at all in a chicken’s diet for there to be problems.

Eating Even a Small Amount of Onion Can Have Negative Consequences

Concerning onions, it is true that just a little bit in their diet is highly unlikely to cause any negative problems, either for the bird or for its eggs in the case of a laying hen.

However, a “little bit” in this case might be a very, very small amount indeed!

Generally, anytime a chicken eats more than half a percent of their bodyweight in onions (or any other plant in the allium genus) they’re likely to start experiencing damage to the bloodstream among other things.

Let me put it another way: if you have an average chicken that weighs 5 pounds, and they eat less than half an ounce of onions, it can cause problems, and the problems will get worse the more onions they eat.

Onion Toxicity in Chickens

Okay, so onions are toxic. But what are we talking about here, what are the consequences? Watery eyes and an upset stomach? Something worse?

As I mentioned above, it can be something way worse in the form of anemia which can be fatal or have lasting health consequences for a chicken.

When the bloodstream loses its ability to carry oxygen to the tissues in the chicken’s body that need it, the effects are total and devastating!

The stress will usually cause chickens to lose their appetite, and initially, they may start acting depressed and have diarrhea since their system cannot cope with onions well in general.

That’s bad enough, but a significant amount of onions (or a small amount of onion rich in the harmful compounds) will manifest rapid or difficult breathing as the chickens struggle to get more oxygen into their bodies to compensate for the loss of red blood cells.

Chickens might also have combs and wattles that appear pale or bluish in color since they will not be suffused with oxygen-rich blood. In the end, chickens will collapse and die from a lack of oxygen, a bad way to go.

This 2004 study shows how devastating onions can be to birds, with the control group being an unfortunate group of White Chinese geese.

That’s the worst that can happen. Other significant but less severe outcomes include tainted eggs and meat.

That’s right- the sulfurous compounds present in onions can make the meat and the eggs that your chickens produce taste oniony, and not in a good way! This has all been known as folk wisdom for some time, but a fairly recent 2011 study confirms it.

And there are many more studies of onion toxicity in animals including chickens. You can find a short list of them here on PoultryDVM, a site that coincidentally rates onions as a 6-out-of-10 threat factor for chickens.

Nonetheless, Studies Have Shown Onions Can Still Benefit Chickens

But, for all of that, it is possible to feed onions to chickens without harming them, and indeed onions can have certain benefits for your chickens.

Although, whether or not these benefits are worth the risk and then worth the painting of their eggs and meat is an entirely different conversation!

Consider this study that showed considerable benefits for chickens fed onions as part of their diet concerning nutrient uptake, overall blood health and meat quality.

And we cannot entirely discount the tons of anecdotal evidence from chicken keepers around the world that routinely feed their chickens onions, onion greens or other plants in the allium genus with seemingly no ill effects.

So, at least some of the time, chickens can have onions in their diet.

Onion Nutritional Info

So is there anything else about onions that are beneficial for chickens? In terms of raw nutrients, yes, onions do contain several nutrients that chickens need, vitamins and minerals alike.

Looking at the vitamin content of onions, we see they have a good assortment of the B-complex ones, including lots of B6 and lesser amounts of niacin, riboflavin, thiamine, and pantothenic acid. Onions also contain a good shot of folate and vitamin C.

The mineral intake is likewise varied, but somewhat limited, with manganese being the standout offering, along with phosphorus and lesser amounts of magnesium, iron, calcium, potassium and zinc.

These minerals are definitely of benefit for chickens, but remember that chickens will not be able to eat onions in any quantity significant enough to make these minerals worthwhile before they start to suffer the negative consequences of the sulfides and dioxides present in onions.

Are Onions Safe for Chickens Raw?

Only in tiny amounts. Raw onions contain the best overall profile of vitamins and minerals but they also have the most harmful compounds that can sicken or kill your chickens.

Are Onion Greens Safe for Chickens?

Again, only in very limited amounts, and eaten infrequently. Although onion greens typically contain smaller amounts of harmful compounds overall compared to the bulb, they still have them and these can harm your chickens if they eat too much.

Is Onion Powder Safe for Chickens?

No. Onion powder is still made of onions and it still contains the aforementioned sulfides and such that will hurt chickens.

Can You Cook Onions to Give Them to Chickens?

Yes, but you can only feed them cooked onions very sparingly as with all other kinds of onions.

Cooking onions will reduce the vitamin and mineral profile, but it also reduces the amounts of harmful compounds. That being said, it does not render onions truly safe for chickens.

Are Onions Safe for Baby Chicks?

No! Never give onions, in any form, to chicks. Chicks are simply too small, too delicate and way too sensitive to toxins to eat onions at all.

Even a few tiny bites from an onion could be enough to kill your chickens.

How Frequently Can Onions be Fed to Chickens?

Onions should only be fed to your chickens in tiny amounts and occasionally, no more than one small serving per week.

There are many chicken owners who have reported it giving their flock onion scraps, onion greens, and more with some regularity and have reported no ill effects.

That’s fine, but if that’s the route you want to go remember that you might be gambling with the life of your birds.

Whatever you decide, keep a close eye on your chickens, and observe for any negative effects and other symptoms of onion toxicity.

What’s the Best Way to Serve Onions to Your Flock?

The best way to give onions to your flock is finely chopped, not only to make them easier to eat but also to make it much easier for you to control the portions precisely.

Do the same for onion greens, too, if you are giving those to your birds.

Don’t Feed Your Chickens Any Onions with Other Ingredients

Onions are basically a constant in a lot of foods and other dishes that we prepare. Even if there aren’t whole onions in the food in question, there is probably onion powder!

It lends everything a delicious, savory taste that you’ll definitely notice once it’s missing.

Unfortunately, you can’t give any of these foods to your chickens. Not only will the toxicity of the onion persist, whatever form it is in, but other ingredients like salt, sugar, oils, butter, and the like are all very bad for your birds and together with onions can be a nasty one-two punch for their system.

These ingredients on their own can make chickens seriously sick, or even kill them: sodium poisoning is a real condition!

Don’t Leave Onion Scraps Around the Run or Coop

The last tip I can give you about onions: if you’re going to feed them to your chickens, don’t leave any scraps or leftovers lying around the run, coop or other areas.

Not only will they stink terribly, but that pungent aroma will also attract pests and predators, particularly mice and rats.

They might be attracted to the smell, but they’ll probably start eating chicken feed, eggs and chicks assuming they do not attack adult chickens outright!

If you’re going to feed onions to your chickens clean up those scraps when they are done!