Egg yolk peritonitis is an infection of the peritoneum, the thin lining of the main body cavity, caused by egg yolk material spilling out of the reproductive system. If untreated, peritonitis can lead to fluid buildup, organ failure, and death.
When birds ovulate, the ovary releases an ovum (yolk) into the infundibulum at one end of the salpinx (oviduct), which then leads at the other end to the shell gland (uterus) and eventually the vent, where it exits the body during laying.
Sometimes, however, yolk material spills out of the ovary-infundibulum passage and into the main body cavity. Yolk material is an excellent growth medium for bacteria, resulting in proliferation, inflammation, and infection.
The type of farming, the conditions on a farm, and dietary insufficiencies do not cause peritonitis. An absurdly unnatural laying rate does.
Modern laying hens lay between 200-300 eggs per year, meaning that each ovulation creates an opportunity for yolk to exit the reproductive system and cause infection. Selective breeding for an unnaturally hyperactive reproductive system is perhaps the reason that peritonitis was found to be the leading cause of death in commercial laying hens, according to one study by industry sources in 2017.
Peritonitis can be treated with fluid draining and medications (anti-inflammatory and antibiotic), but a hen who is actively ovulating is always at risk for potential peritonitis. The best way to prevent peritonitis is through cessation of ovulation, which is possible thanks to medications administered by veterinarians.
Caregivers at vegan sanctuaries know the dire risk of peritonitis all too well. Whether it’s finding a resident with sudden “water belly” or rescuing a hen with advanced, untreated infection, we see firsthand the direct connection between selective breeding for maximum egg production and the prevalence of peritonitis.
There is no such thing as an ethical egg.
SOURCES
“Egg Yolk Peritonitis.” https://www.theveterinaryexpert.com/backyard-poultry/egg-yolk-peritonitis/
“Causes of Normal Mortality in Commercial Egg-Laying Chickens.” https://doi.org/10.1637/11556-120816-RegR
“Eggs: What Are You Really Eating?” https://freefromharm.org/eggs-what-are-you-really-eating/
“Egg Yolk Peritonitis in Backyard Chickens.”
https://vcahospitals.com/know-your-pet/egg-yolk-peritonitis-in-backyard-chickens
“Egg Peritonitis in Poultry.” https://www.merckvetmanual.com/poultry/disorders-of-the-reproductive-system-in-poultry/egg-peritonitis-in-poultry