The Pathophysiology of Chronic Hypoxia in Chickens

Abstract

The debilitating effects of the hypoxia encountered at high altitude have been recognized for many hundreds of years, and have recently been the subject of numerous scientific investigations (8,9). Prolonged residence at high altitude leads to characteristic anatomic and physiological alterations (4,8), as well as special pathophysiological conditions such as "Brisket Disease" in cattle (3). The domestic fowl is particularly suited to studies of the pathophysiology of chronic hypoxia. Since it is the most sensitive of small homeotherms to hypoxia (1), effects may be rather severe at mountain altitudes.c Because of their ovipary, colonies of chickens can be maintained at reasonably high elevations by carrying out incubation (i.e., embryogenesis, the process most sensitive to hypoxia) at lesser and more suitable elevations. In 1955, a colony of Single Comb White Leghorn (SCWL) chickens was established at an elevation of 12,500 feet, at the White Mountain Research Station," with week-old chicks introduced from sea level. In 1956, a few of the chickens were sacrificed to determine the cause of a persistent mortality among adults. No evidence of contagious disease was encountered; however, there were obvious heart lesions and signs of chronic circulatory insufficiency. More detailed examinations were made in 1960, 1962, and 1964, and the results are reported herein.