When it comes to feeding your chickens scraps and treats, one of the biggest challenges is filtering through all the information out there. The advice is often wrong and different sites have conflicting information. One site will say certain food is toxic to chickens and another will say it’s ok.

In this post I'm going to review and fact check some of the food that is commonly listed as toxic to chickens

What makes food toxic?

To start with, I think it's useful to step back to understand what makes food toxic. Most of the food thought to be toxic to chickens, relates to food that contains potent phytochemicals:

  • Avocado: Persin
  • Tomatoes: Tomatine
  • Onions and Garlic: Sulfur
  • Potatoes: Solanine
  • Apple seeds: Amygdalin
What are phytochemicals?

These chemicals are the plants defences, such as naturally occurring pesticides, antibacterials and anti-fungals. Some of these can be toxic at high doses. However at low doses, there's plenty of research to show that some of these are beneficial.

Which means:

“the poison is in the dose”

Stress kicks in natural defences

Recent research and theories on nutrition suggest that some of the health benefits from fruit and vegetables come from minute exposure to stress from the chemicals produced by plants. And when we eat them and when chickens eat them, they cause a small amount of stress which kicks in natural defences, making the body and the immune system healthier and better prepared. Without this stress, our cells become complacent and less able to defend itself against disease.


1. Avocado

Can chickens eat Avocado?

Can chickens eat Avocado?

Photo Source: www.kjokkenutstyr.net

Common advice

Avocado is often listed as a food that’s toxic to chickens. Sometimes the whole avocado is listed as toxic. And sometimes only the skin and seeds are listed as toxic.

My recommendation

Avocados are toxic to chickens because they contain a natural fungicide called persin, which birds are particularly sensitive to. Err on the side of caution and don’t feed your chickens any avocado, including the pulp. 

The facts

Toxicity: Avocados contain a natural fungicide called persin, which birds are particularly sensitive to. Persin is mainly found in the leaves, pit and skin of avocados, but it’s also found in the pulp in small amounts. While avocado pulp seems to be ok (based on my own experience and reports from others), some varieties of avocado have higher amounts of persin than others. 

Symptoms:  Persin toxicity in chickens can include difficulty breathing, appearing weak and lack of movement. Death can occur within 1 to 2 days

References:

2. Apple seeds

Can chickens eat apple seeds?

Common advice

Apple seeds is often listed as a food that’s toxic to chickens because they contain cyanide.

My recommendation

Apple cores and their seeds are perfectly safe to feed your chickens.

The facts
Apple seeds contain a small amount of Amygdalin which can possibly break down during digestion to release trace amounts of Cyanide.

So it's true that apple seeds contain cyanide.

But the amount and concentration of cyanide is so small it doesn’t harm chickens. And cyanide doesn’t build up over time and is quickly removed by the liver and kidney.

A 1kg chicken would need to eat over 500 apple seeds in one sitting for it to be toxic.

There are also lots of other nuts, fruit and vegetables seeds that contain similar amounts of amygdalin. This includes almonds, sunflowers, courgette, cucumber and squash.

References

3. Potato skins / peels

Can chickens eat potato skins / peels?

Common advice

Potato skins contain solanine which can kill your chickens.

My recommendation

Potato skins are perfectly safe to feed your chickens. However solanine is produced in toxic amounts in the green parts of the potato, so you should avoid green potato skin, shoots, leaves and stems.

To prevent potatoes from going green, store them in a cool, dark place.

If potatoes are green and spouted, throw it out.

The facts

It’s true that Potatoes contain Solanine and is concentrated in the potato skin (30 to 80%). 

And it’s true that high amounts of Solanine destroys red blood cells and can cause diarrhea and heart failure. Solanine is part of the plant’s defence against insects, disease and other predators.

But there isn't enough Solanine in potatoes to cause harm.

Studies show potato waste meal can be used as a substitute for maize (corn) for up to 30% of a chickens diet without any negative effects.

It’s actually green potato skin and sprouting potatoes that contains much higher amounts of Solanine (100 times more) and should be avoided. The green colour is chlorophyll which isn’t toxic. However solanine is produced in the green parts of the potato. So this includes green skin, shoots, leaves and stems. 


References

4. Green tomatoes and leaves

Can chickens eat green tomatoes and leaves

Common advice

You shouldn’t feed your chickens green tomatoes or tomato leaves, because they contain toxic levels of solanine.

My recommendation

Green tomatoes and tomato leaves are perfectly safe for your chickens to eat and are an excellent part of a varied and healthy diet.

The facts

Toxicity

The common advice that green tomatoes contain solanine is wrong. Tomatoes are a member of the nightshade family but don’t contain solanine.

Tomatoes contain tomatine. There are significant quantities of tomatine in green tomato and tomato leaves, but tomatine isn’t toxic. As stated by Dr. Mendel Friedman of the federal Department of Agriculture, who has studied potato and tomato alkaloids for two decades:

“Commercial tomatoes contain tomatine. Solanine, is a potato alkaloid. There are significant quantities of tomatine in green tomato fruits, which people have long eaten fried and pickled. And tomatine appears to be a relatively benign alkaloid.”

Benefits

Rather than being toxic, studies reported by Dr. Friedman show tomatine has lots of health benefits:

  • Improves the cholesterol profile of animals: Tomatine ingested by animals passes through unabsorbed. It binds to cholesterol, ridding the body of both alkaloid and cholesterol.
  • Protects against cancer: Green tomato extract was shown to lower the incidence of cancer in animals and inhibits the growth of various human cancer cells.
  • Stimulates the immune system: Purified tomatine was found to stimulate the immune system in desirable ways.

References

5. Onions

Can chickens eat onions?

Image Source: Stilleben on Flickr 

Common advice

You shouldn’t feed onions to your chickens because they contain high amounts of sulfur which is toxic to chickens.

My recommendation

Avoid feeding your chickens onion, except in very low doses as a supplement (2-3 grams). Onion contains sulfur which is toxic to chickens in sufficient amounts (more than 5 grams). However at low doses (2-3 grams) there is some evidence that onion and garlic has positive effects such as improved growth and feed intake. 

The facts:

Toxicity

Onions are toxic to chickens in sufficient amounts. This includes all forms of onion: raw onion, cooked onion, onion powder and other plants of the Allium family (e.g. garlic, leeks, shallots).

Sulfur in onions decomposes to disulfides through digestion which can destroy red blood cells and can cause anemia or even death.

The toxic dose of onions hasn’t been well studied in chickens, however a good guide is to keep it to less than about 5% of feed (about 5 grams a day). If a chicken eats a bit more than this as a one-off, it’s not likely to be affected. But a chicken that regularly eats large amounts of onion could be affected.

In practice, chickens don’t generally eat raw onions but will eat cooked onions. So you need to be especially careful when feeding leftovers to your chickens. So don't go feeding your chickens onion soup.

Symptoms
  • Pale Comb And Wattles
  • Loss Of Appetite
  • Rapid Respiratory Rate
  • Difficulty Breathing
  • Weakness
  • Diarrhea
  • Depression
Benefits

The interesting thing about onion and garlic is that at low doses (2-3 grams), studies show it has positive effects. This is roughly about a quarter of an average sized clove of garlic. For commercial operations, garlic and onion are being explored as an alternative to antibiotics for growth promotion.

Some of the positive effects that have been studied from low doses of onion and garlic include:  Improved growth, improved feed intake, decrease in bad cholesterol and improved meat quality. These positive effects are thought to come from the antibacterial and anti-fungal properties of onion and garlic.

References

5. Uncooked Rice

Can chickens eat uncooked rice?

Image Source: Rob & Dani on Flickr

Common advice

Uncooked rice expands in your chicken's stomach, causing digestive issues and can even cause your chickens to explode.

My recommendation

Uncooked rice is safe to feed your chickens. It doesn't expand or blow up and is a nutritious option to include in your chickens diet.

The facts

Chickens can eat uncooked rice, it doesn’t expand or blow up inside them. This is an Urban myth that just won’t go away.

This seems to have started from the myth that wedding rice causes pigeons to blow up and has carried across to advice for chickens.

Uncooked rice is actually part of a chicken's natural diet. Jungle fowl (the chicken's wild ancestor) eat a lot of bamboo rice when bamboo goes to seed, which is similar in a lot of ways to normal rice.


References

  • steve anderson says:

    Tomatoes are on the list. I let my small flock (6 hens) free-range during the day. My observation is that all my Hens move to my tomato patch as soon as they are released. I have never seen them peck or eat tomato leaves or tomatoes. Just wondering, if they are dangerous why do my heds move towards them? The loose soil?

    Thanks, I will continue to read and when tomatoes are up, I will enjoy,

    Reply

    • My chickens love tomatoes and the leaves. They are perfectly safe for chickens to eat. More detail in the upcoming post.

      Reply

  • Thanks Marcus for this series – very useful, very informative, especially the avocado and uncooked rice sections.

    Reply

  • And could you please advise whether it is OK to give chickens left over sliced bread/toast? I have been told that it clogs them up and affects their excretory function, but I haven’t noticed that with mine.

    Reply

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