These hens ovulate normally, but the yolk is dropped into the abdominal cavity rather than being collected by the oviduct due to inflammation and resulting obstruction of the oviduct after infection with E coli or Mycoplasma gallisepticum. The yolk is absorbed from the abdominal cavity. The hen looks like a normal layer but does not produce eggs. Hypoplasia of the ovary and oviduct has been associated with infectious bronchitis virus infections (see Infectious Bronchitis) at an early age (1–2 wk). Atresia or even atrophy of the ovary are caused by severe stress, chronic infections, insufficient feed intake, inadequate feeder space, and feed refusal due to mycotoxins in the feed.
Last full review/revision March 2012 by A. Gregorio Rosales, DVM, MS, PhD, DACPV