False layer hens look normal and ovulate normally but do not produce eggs. Typically, hens appear healthy, with fully developed secondary sex characteristics and an active ovary but a nonfunctioning oviduct.
They are found at the peak of egg production.
Courtesy of Dr. Rodrigo Espinosa.
The yolk is dropped into the abdominal cavity rather than being collected by the oviduct, and once in the abdominal cavity, the yolk is absorbed.
Oviduct dysfunction can occur after infections with Escherichia coli or Mycoplasma gallisepticum, resulting in inflammation and obstruction of the oviduct, and also from early infection (at 1–2 weeks) with an infectious bronchitis virus (IBV) that can cause hypoplasia of the ovary and oviduct.
Originally reported in Asia in 1996–1998, where the virus was designated as QX, and in Europe in 2004, classified as D388 (genetically similar to QX), variant IBV has spread through a vast territory and has also been found in North and Latin America.
Timing of infection with IBV viruses is a key factor in determining whether cystic oviduct formation will occur or not (see cystic oviduct photograph). Susceptible birds infected at ≤ 7 days old have increased incidence of cystic oviduct formation (1).
Reference
Mueller Slay A, Franca M, Jackwood M, Jordan B. Infection with IBV DMV/1639 at a young age leads to increased incidence of cystic oviduct formation associated with false layer syndrome. Viruses. 2022;14(5):852. doi:10.3390/v14050852
