Causes of Normal Mortality in Commercial Egg-Laying Chickens

In a large population of animals, it is normal to have some die each day from causes not related to disease, which is often referred to as natural causes. In poultry production, this phenomenon is commonly referred to as daily mortality. In egg-producing chickens, many of the natural causes of death are associated with making an egg. The causes of normal mortality in commercial egg-laying chicken flocks have been described very little to date. A commercial chicken egg farm, housing approximately two million single-comb white leghorn chickens (Gallus gallus domesticus) in 16 egg-producing flocks, was visited on a monthly basis to monitor bird health, body conditioning, skeletal integrity, and causes of daily mortality in an attempt to provide early detection of health abnormalities. A representative sample of daily mortality from each flock was necropsied to determine the cause of death. Reported herein is a summary of visits for a period of 38 mo from June 2011 to July 2014. The top 15 causes of normal mortality, in rank order of prevalence, were determined to be the following: egg yolk peritonitis, hypocalcemia, gout, self-induced molt, salpingitis, caught by spur, intussusception or volvulus (twisted intestine), cannibalism (pick out), tracheal plug, septicemia, fatty liver syndrome, internal layer, layer hepatitis, persecution, and prolapsed vent. Other causes noted were hyperthermia (during summer), trauma, coccidiosis, ovarian neoplasia, being egg bound, urolithiasis, peritonitis (not egg yolk induced), leg fracture, caught in the structure, tumor (other than ovarian origin), wing fracture, exsanguination, and cardiomyopathy.