When an egg is laid, the vagina everts through the cloaca to deliver the egg. If there has been injury to the vagina, such as from a large or double-yolk egg, or if the hen is fat, the vagina may not retract immediately, leaving it exposed for a short time. This may result in cannibalism (see Cannibalism in Poultry). When the protruding organ is pecked by other hens, the complete oviduct and parts of the adjacent intestinal tract may be pulled from the abdominal cavity (“peckout”). Bleeding from the vent is observed as a result of pecking. Alternatively, the vagina swells, cannot retract, and remains prolapsed (“blowout”). The hen dies from shock. Prolapse has been associated with excessive/premature photostimulation, poor body weight uniformity, early laying (inadequate body size), large eggs, double-yolked eggs, and obesity. Cannibalism may be prevented by beak trimming, managing light intensity, maintaining appropriate stocking density, and avoiding nutritional deficiencies.
Last full review/revision May 2013 by A. Gregorio Rosales, DVM, MS, PhD, DACPV