Ovarian Cancer in Backyard Chickens

February 24, 2020

I’ve wanted to write this post on ovarian cancer in backyard chickens for a while. But it has taken me some time to do the research so that I can share it with you today. Lately, there is quite a deal of discussion on social media forums about how to deal with hens that experience ascites. Please realize ascites, or “water-belly”, is a symptom, not a diagnosis. Often when drained, the ascites will return because the underlying problem is still present.  Sadly in many egg laying hens, ascites is due to ovarian cancer. Ovarian cancer in hens is not uncommon. In fact, it is thought that approximately 5-35% of egg laying hens will develop this condition in their lifetime.

Understanding Ovarian Cancer in Chickens

Let’s look at the background. This will explain what is happening and explore possible ways to prevent ovarian cancer. I might be turning some of the information from the backyard chicken world upside down. But these discussions are important for us to have, because these are more than “just a chickens” These are our pets.

As many of you know, chickens live an average to 5-8 years. Naturally, pullets begin to lay eggs around 5 months of age and continue to lay (depending on their breed) anywhere from 200-400 eggs until they turn 2 years of age.  After the age of 2, hens will continue to lay approximately 200 more eggs in their natural lifetimes. Currently available research on ovarian cancer in egg laying hens begins at the age of 2.  Subsequently, this is when hens begin to become susceptible.  By far the biggest risk factors that it comes down to is– the more eggs produced in your lifetime, the higher the risk for development of ovarian cancer.

The chicken is the only animal in the world that develops spontaneous ovarian cancer as humans do.

Oyster Cracker developed ovarian cancer

Ovarian Cancer in Backyard Chickens: Risk Factors

Egg Laying

There have been a few studies done in which hens are divided into two egg laying groups. For example, in one group, some hens received an injection of progestin. This hormone ceases egg laying production. Not surprisingly, this treatment was shown to decrease the development of ovarian cancer by 90%.  In another study, a researcher examined wild-type birds verses birds whose ovulation had been restricted. Similar results were seen that have allowed researches to correlate that a higher egg laying rates with a higher risk of developing ovarian cancer².


When studying diet, researchers examined a caloric diet restriction that cause a decrease in the number of eggs produced by hens. In this study, they found a five fold decrease in the development of ovarian cancer. Furthermore, the chickens that had an unrestricted diet produced approximately 64% more eggs.  In another study involving hens, some were fed a diet that consisted of 10% flax seed enriched diet for four years. These hens showed a reduction in the severity and incidence of ovarian cancer.  Incidentally, flax seed is what the commercial egg companies feed their hens to get Omega-3 fatty acids into the eggs.  Lastly, there is some thought that having a diet high in soybeans can effectively “turn on” genes that are associated with reproductive cancers. Soy is high in plant estrogens (phytoestrogens) called isoflavones.

Hens in the wild, unaffected by man’s breeding, lay 10 – 15 eggs per year.

Genetics/Breeding for Characteristics

Finally, genetics play a key role. As you know, chickens are prized for their eggs and often the more productive a hen is, the higher her worth to the farmer or chicken keeper. Often, I hear stories from folks that keep chickens primarily for their eggs. Consequently,  they turn over their flocks every two years or so. This is the same practice with commercial farmers. For example, egg laying hens in factories are considered “done” at about 18 months of age. As a result, hens have been selectively bred to produce eggs, up to 240 eggs per year on average for the typical backyard chickens. Lastly, did you know that chickens in the wild only lay 10-15 eggs per year?

How to Prevent Ovarian Cancer in Hens

I have lost a couple of hens to ovarian cancer over the years. For some, one of the first signs is that they will begin to walk with a wider gait. Their legs appear further apart. Subsequently, when you feel their bellies, they feel like a water balloon. Sadly, it’s hard to tell at first as, they can hide a lot under all those feathers. A regular exam of their abdomen can help assess for fluid.

Unfortunately, there is no cure for ovarian cancer in hens. But some of these things may help. Perhaps these steps might curtail the development of ovarian cancer.

  1. Consider purchase of breeds that are not heavy egg layers.
  2. Allow hens a natural break in the winter from laying eggs.
  3. Omit artificial lighting in the chicken coop to stimulate egg laying.
  4. Allow hens to go broody because this also allows for an egg laying rest period.
  5. Consider adding flax seed to their diet.
  6. Consider restricting their caloric intake. (Approximately 1/4 cup chicken feed per day/hen)
  7. Consider feeding your flock a soy-free alternative.
  8. Explore alternative protein sources for your flock other than soybeans.
  9. Consider reaching out to the major national chicken feed manufacturers and requesting them to develop/provide a soy-free feed or one that includes flax seed.
  10. Weigh going organic to avoid exposing your flock to unnecessary pesticides and harvesting by-products including glyphosate (a known carcinogen) and GMOs (genetically modified organisms).
  11. Likewise, increase free-ranging your flock to diversity and supplement their diet.
  12. Furthermore, share this information with fellow chicken keepers.


Oyster Cracker developed ovarian cancer.
In memory of Oyster Cracker

Please know that this post is intended for informational purposes only and does not substitute for advice from a licensed veterinarian.



1: Oral contraceptives decrease the prevalence of ovarian cancer in the hen.
Treviño LS, Buckles EL, Johnson PA
Cancer Prev Res (Phila). 2012 Feb; 5(2):343-9.
2: The restricted ovulator chicken: a unique animal model for investigating the etiology of ovarian cancer.
Giles JR, Elkin RG, Trevino LS, Urick ME, Ramachandran R, Johnson PA
Int J Gynecol Cancer. 2010 Jul; 20(5):738-44.
3: Reduction of ovarian and oviductal cancers in calorie-restricted laying chickens.
DK, Barnes HJ, Anderson KE, Petitte JN, Whitaker R, Berchuck A, Rodriguez GC
4: Long term consumption of flaxseed enriched diet decreased ovarian cancer incidence and prostaglandin E₂ in hens.
Eilati, Erfan; Bahr, Janice M; Hales, Dale Buchanan
Gynecologic oncology, ISSN: 1095-6859, (2013)Vol: 130, Issue: 3, Page: 620-8
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10 thoughts on “Ovarian Cancer in Backyard Chickens”

    • There are many feed brands that are soy free. A quick google search will help you to discover brands that are available to you based on your geographic location. Keep me posted with what you decide. Always so good to share with one another.

  1. Melissa, I believe that is what happened to my Sunshine. It showed up when she was 2 1/2. Thank you for this article. I will take some of your suggested steps. My old girls (two remaining of my first flock) will be seven in April. Interestingly, they were the two who spent a lot of time being broody. My little girls will be one year the end of March. I wonder how much flax seed I could give them as a supplement.

    • Hello Susan, I’m so sorry to hear about Sunshine and happy to hear that some of your girls are doing well at 7. The Flaxseed in the studies was given at a rate of 10% of the feed. I hope that this helps and I’m so excited for your little ones too! It is fun to have a flock of mixed ages.

  2. Not sure why doodle died. But she didn’t have any of the signs of the common chicken illnesses. She did have a prolapsed vent about 4 months ago. I took care of that. She laid enormous eggs. I did notice her belly looked swelled. Her appetite was good until the night she died. It looks liked she went in her sleep. The rest of the flock looks fine. She died have a grayish diarrhea. She was also listless with ruffled feathers. She was 1.5 to 2 years old.

  3. I’m pretty sure my Buff Orpington Goldie had ovarian cancer. Everything you mentioned about the gait and water belly sound just like Goldie. I had researched and found the info on ascites. I never had the courage to drain her though. She was always such a spunky little lady. She was a little over 5 years when she passed.


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