I recently had a 13-month old hen die unexpectedly. I noticed a feather stuck to her foot and picked her up to remove it. That she didn’t run off was a clue that something was amiss. I looked at the bottom of her feet for bumblefoot, felt her crop and gave her the once over. Other than her looking slightly ‘off’ I didn’t see anything obviously wrong.
In a pen of almost thirty birds it’s difficult to keep track of them as individuals. Was she still laying, eating, drinking? I thought so. Did she look sick, isolate herself, not go to the roost bars at night? No. That night I checked the pen to ensure she made it back to the coop before the automatic door closed. The next morning I found her dead on the floor where she had gone to sleep under the nest boxes. I was surprised as I’d never had an ‘unexpected’ loss in a bird that appeared pretty normal right up until her demise.
I took a day-long Small Flock Health Management workshop last spring facilitated by two avian veterinarians/pathologists who work for the provincial Animal Health Centre outside of Vancouver. I decided that I would send my next casualty to them for a necropsy, both to discover that individual’s cause of death, but also to see if there were any underlying health issues in my flock that I should be aware of.
When I got the post-mortem results back I was shocked: the cause of death was visceral gout. I didn’t even know there was such a thing as avian gout. So I did some research to educate myself about what it is and how she might have got it. I read through several journal articles and had to google the meaning of most of the terms.
Here’s my translated layman’s version of what I found:
Kidneys are vital organs with diverse metabolic and excretory functions: maintaining the chemical composition of body fluids; removal of waste and toxic products; regulation of blood pressure and conservation of fluids and electrolytes.
Uric acid, a waste product from protein breakdown, is produced in the liver and is the final product excreted from the kidneys into urine. Birds don’t urinate separately like mammals, but pass uric acid in a semi-solid form appearing as the white cap on poop.
Gout is the result of either the production of too much uric acid or, more commonly, decreased kidney function enabling excess uric acid to cause damage to various internal systems. Birds with impaired kidneys may not be able to get rid of uric acid as efficiently, leading to a buildup in their blood and uric acid deposits within the joints and in visceral organs or other tissues. Over time, these deposits will grow to form masses of uric acid crystals. The acid itself isn’t toxic but the resulting crystals cause damage – sometimes severe – to kidneys, heart, lungs, air sacs, intestines and joints.
Visceral Gout: uric acid crystals collect along the surface of internal organs and other sites within the body. A necropsy would reveal white chalky deposits around the heart, kidneys, gizzard, intestines, air sacs and liver, which damage the kidneys and impair their functioning. This is the most common form of avian gout and can affect chickens of all ages, including very young chicks.
Articular Gout: accumulation of urates in joints, ligaments and tendons, including the toes of the feet. Usually not found on it’s own, but in birds who also have visceral gout.
Unfortunately, like many things that affect chickens, the symptoms of gout are non-specific:
Depression; decreased appetite; dull, ruffled feathers; weight loss; lameness; unsteady gait; loss of yellow colour in beak and legs; moist vent and diarrhea.
As in my case, accurate diagnosis is made post-mortem, when lesions reveal urate deposits on the internal organs and tissues; inflammation of the intestine; and irregular and enlarged kidneys.
It appears there are more causes of gout than you can shake a stick at. Anything that causes damage to the kidneys and impairs their functioning can lead to gout. Here are a few:
- Healthy kidneys are not affected by high dietary protein levels, but if your bird has pre-existing kidney damage, feed containing more than 30% protein can lead to excessive uric acid production, worsening the kidney function.
- Low amounts of vitamin A and phosphorus can contribute to gout.
- Infectious Bronchitis virus (IBV): some strains affect the kidneys; can be transmitted via eggs, leading to gout in young chicks.
- Avian Astrovirus: two strains of this virus, avian nephritis (ANV) and astrovirus (CAstV) can impair kidney function. These viruses can also be transmitted from eggs to chicks.
- Infectious Bursal Disease (IBD)
- Molds, pesticide and insecticide residues can damage kidney tissue, causing inflammation.
- Anything that affects adequate water intake is a potential issue for kidney damage: additives; competition for, or inaccessible, waterers; inconsistent access; low pH; improper hatchery management.
- Chicks held for long periods in a hatchery or transported for long distances without water.
- Antibiotics that are excreted through kidneys put an extra load on them, especially when given in excess of the recommended dosage
- Ascites: Initial stages (oxygen deprivation) can lead to symptoms of gout.
- Make sure you’re feeding the correct formulated feed at age appropriate stages.
- Provide balanced feed with proper ratios of calcium-phosphorus, Vitamins A, D3, sodium, and protein.
- Too much calcium can produce urate crystals. Don’t give your birds layer pellets, which contain higher amounts of calcium required for egg production until they are at least 20 weeks old, or laying. Make sure not to feed vulnerable chicks high calcium diets.
- Don’t feed salty human foods or large amounts of fish meal, which stress the kidneys.
- Ensure your coop is well ventilated and that your birds do not become dehydrated.
- Always have easily accessible clean water available, especially in hot weather, freezing conditions or during transport.
- Use urine acidifiers, such as apple cider vinegar, added to their water
- Be aware that antibiotics, sulpha drugs and anticoccidials can cause kidney damage.
- Never feed moldy food.
I have no idea what was the cause of this hen’s kidney damage. I adopted her when she was about four months old and don’t know if she was fed layer pellets until then. If so, that might have been enough to impair her kidneys, leading to gout.
FYI: I didn’t understand all the terminology from the necropsy report, but here’s an excerpt of the salient points, if you’re interested:
Bird is in fair general body condition with mild reduction in muscle mass and marked reduction in hydration. Feed is present in crop. No external parasites seen. The ovary has recently regressed and there is mild chronic egg yolk peritonitis. There are moderate visceral urate deposits (heart, liver, lungs) and the kidneys are swollen, pale and mottled with urate.