The goiter (Latin ingluvies ) of birds is a bulging of the esophagus on the neck, immediately in front of the breast entrance. It is a food store and serves to pre-swell the saliva- fed food. The mucous membrane of the goiter contains glands, these are located in the "goiter street" in the chicken and in the fundus in the pigeon ; Digestive processes do not take place here (but see Hoatzin ).
The goiter is particularly well developed in bird species that have to be able to consume larger amounts of food discontinuously. In chicken birds (Galliformes) it represents a right-sided bulging of the esophagus. In pigeons (Columbiformes) the goiter is developed in the form of two lateral sacs.
In pigeons there is a thickening of the epithelium in the crop during the breeding season . Detached epithelial cells form a fatty, holocrine secretion , the so-called goiter milk or pigeon milk . In flamingos (Phoenicopteridae) this “milk” is not only produced in the crop but also in the rest of the upper digestive tract.
The goiter milk is a whitish cream cheese-like mass. It is choked up by the parent animals and serves to feed the nestlings during the first days of life. In pigeons it consists of 65–81% water, 13–19% protein and 7–13% fats .
Goiter diseases often show up in regurgitation .
A crop inflammation ( Ingluvitis ) is a relatively common disorder. It is rarely caused by bacteria, but mostly by yeast (→ macrorhabdiosis ) or trichomonads . Goiter infections caused by bacterial and yeast fungi are mostly secondary to damage to the mucous membrane caused by food or artificial nutrition. Seldom concrements ( goiter stones ) can form in the goiter . Like other foreign bodies, these may require a surgical opening of the head ( ingluviotomy ). A widening of the head occurs primarily as a result of incorrect feeding. Drop fistulas are especially dangerous when the overlying skin is intact. Goiter tumors can also occur.
- "Even pigeons produce - healthy - milk" report from 19 September 2011 at science.orf.at, last accessed in July 2012