Working Up Reproductive Disease in Birds

Working Up Reproductive Disease in Birds

The ratio of male to female birds is approximately 1:1 in most species. The sex chromosome of birds is designated Z, and female birds have ZW chromosomes, while males are ZZ. As in mammals, gonads originate from the mesonephric duct. Germ cells are distributed equally right and left, and then migrate primarily to the left in female psittacines to become a single left ovary and uterus. Hermaphrodites, and parrots with a portion or intact right reproductive tract have been reported (1).

The early ovary contains a cortex and medulla, but this organizational structure is lost and the mature cortex contains immature follicles, while the medulla contains a prominent vascular zone. Follicles have a blood and nerve supply, and endocrine connection with the uterus (1). The infundibulum catches the egg after ovulation and directs it to the uterus. Abberations in anatomy or function can result in an “ectopic” yolk deposited directly into the celomic cavity (internal laying). In some cases the ovum is reabsorbed, or can result in yolk peritonitis. Fertilization occurs in the infundibulum, and in chickens must occur during a short time frame prior to laying down of albumin. The oviduct consists of the magnum (addition of albumin), isthmus (deposition of inner and outer shell membranes) and shell gland (plumping, or addition of water and electolytes, and actual calcification); after passage of the egg through the oviduct the egg passes through the vagina to the cloaca and out the vent. […]