Last week I got a call from my friend Laurie: her favourite hen had died unexpectedly and she was looking for information on where to send her for a necropsy. She found Krista, a 9 month-old hen at bedtime lying under a tree where the flock usually gather. Upon closer inspection, it was clear that she was dead without a mark on her. Until that time she had appeared healthy with nothing amiss.

I’ve written previously about the importance of having a necropsy done when you experience an unexpected death or are curious about what is going on in your flock. Needless to say, both Laurie and I were interested in what could have killed Krista so suddenly. While we waited for the lab results I was secretly hoping there would be something new I could write about. The lab did not disappoint: her cause of death was a ruptured liver caused by Fatty Liver Syndrome (FLS), something that surprised the two of us.

FLS was on my long list of topics to research, now it had moved to the top.

Fatty Liver Syndrome is a metabolic disorder resulting in the sudden death of birds usually fed high-energy diets with limited exercise. Mammals synthesize fatty acids in tissue, while in chickens, 90% occurs in the liver. Metabolic and physical stress associated with egg-laying are believed to be factors that induce the final, fatal haemorrhage. A necropsy would reveal an enlarged liver with varying degrees of haemorrhage and the abdominal cavity often contains large amounts of oily, unsaturated fat.

It is a common condition in both commercial farms with production layers and backyard chickens alike. It’s no surprise in a world of overweight, sedentary people we also have overweight chickens eating things not on the traditional list of recommended foods that also don’t get enough exercise.

For many people small flock chickens are primarily pets. What that often means is feeding them snack food, household leftovers and high sugar or fatty treats, in addition to manufactured feed. At the same time, lots of folks keep backyard birds in small runs. Chickens are foraging animals and are designed to move around their territory throughout the day looking for food. Some penned birds don’t get the same level of exercise as free-range birds. It’s usually that combination of diet and lack of mobility that can lead to Fatty Liver Syndrome. Other, less common, causes include: exposure to mycotoxins (moldy feed), calcium deficiency or stress.

My friends Thomas and Elizabeth don’t feed their birds any manufactured feed. Their flock of 25 are given @3 cups of wheat twice daily along with produce gleaned from our local food recovery program. They free-range on ½ acre and have access to the compost bin. When I mentioned Krista’s death Thomas said that he noticed an interesting trend when he butchered chickens. They raise birds for their own consumption and are occasionally offered surplus cockerels and older hens as well. Thomas noted the birds that come from other flocks often have fatty deposits around their livers, while their own birds do not. Of course, this is anecdotal evidence, but it does suggest that birds who are active and eat low fat and low sugar diets are less likely to develop FLS.

Risk factors

  • Low-protein (less than 17.5%) and high-fat (more than 3.5%) diet: Birds have a unique method of removing lipids from the liver; when they have a protein deficiency, usually related to inadequate amino acids, it results in the build up of lipids and the formation of fatty liver.
  • High-energy diet: corn as the main ingredient.
  • Age: older hens are more likely to develop FLS than younger birds, regardless of their diet.
  • Hormone imbalance: egg production increases both estrogen levels and fat content in the liver.
  • Heat stress: exposure to excessive hot weather conditions.
  • Most common in spring and summer.


  • Abdominal swelling (ascites or enlarged liver)
  • Abnormally long beak and nails
  • Green or yellow poop caused by excessive biliverdin or bilirubin
  • Lethargy
  • Obesity
  • Decreased appetite
  • Increased water consumption
  • Pale comb
  • Decreased egg production
  • Dandruff on comb or wattle
  • Poor feather condition
  • Abnormal feather color caused by lack of pigment
  • Laboured breathing


  • Diet of at least 17.5% protein and less than 3.5% fat
  • Give B-complex vitamins (especially B4 and B12) and selenium
  • Provide antioxidant rich foods: blueberries, kale, red cabbage, cooked beans, spinach, collard and mustard greens, broccoli, Brussel sprouts
  • Avoid high sugar or fatty foods: human snack food, grapes, corn, bananas, mangos, pears, suet, fat, cheese
  • Ensure your birds have space to exercise

In some ways Krista’s was a classic case of Fatty Liver Syndrome: although she didn’t appear large, her necropsy indicated she was mildly obese and she died without warning. How it differs was she was able to free-range on ½ acre, was very active and that she was less than a year old.

In hindsight, Laurie had noticed a large green poop several days before, but had no way of knowing which hen it came from. She feeds her birds manufactured feed, but like many small flock owners gives them plenty of treats, including sunflower seeds, dried cranberries and fat. Their night time ritual involves more treats as an inducement to return to the coop.

Neither of us have knowingly had obese chickens or liver issues in our flock before, but Krista’s death was a bit of a wake-up call for us both, regarding what kinds of ‘extras’ we are giving our birds that might be detrimental to their health. We all love our birds, but it’s important that our well-meaning, but misguided, intentions don’t harm them.

Credits: Merck Veterinary Manual,  Poultry DVM and Poultry Hub.                           Featured Photo (at top): Nutrition Facts

2 comments on “Fatty Liver Syndrome

  1. Is this what is done on purpose to unfortunate geese to make foie gras? If it is, I can’t imagine the pain they must suffer.

    Liked by 1 person

    • In the case of chickens they end up with fatty livers due to too much of the wrong food and not enough exercise. Whereas geese are force fed and their livers become so enlarged they are six to ten times normal size.


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