ABSTRACT
The avian oviduct is a tubular organ extending from the ovary to the cloaca. In laying hens, the oviduct is 40-80 cm long, consisting of five portions: infundibulum, magnum (albumen-secreting portion), isthmus, uterus, and
passage of the egg and secretes extracellular matrix components to surround the egg albumen. The yolk enters the oviduct and is surrounded by two layers of thin white, and two layers of thick white. Initiation of calcification occurs in the shell gland (uterus). The egg stays in the uterus for about 21-26 hr to complete the process of calcification (5). The high rate of calcium secretion returns to basal level approximately 2 hr before expulsion of the egg. It takes approximately 2 grams of calcium to form an eggshell. Prior to calcification, the egg takes up water and pigments into the albumen from the tubular glands. Pigment deposition occurs in the last three to five hours the egg spends in the shell gland. It is believed that light colored eggs spend a shorter amount of time in the shell gland, and therefore have less shell deposition. The laying of an egg is known as oviposition, which occurs in sequences. Sequences are consecutive days of laying that are separated by a “pause”
TABLE 153.1 Major Hormones Involved in Egg Productiona
changes through the egg production year. The longest sequences are seen during the time of peak production at about 30 to 35 weeks of age (3,4).
