Metabolic adaptation of the chick embryo to chronic hypoxia

In a colony of white leghorn chickens maintained at 3,800 m successive generations exhibited an increasing hatchability of fertile eggs incubated at elevation of 3,100m. Embryonated eggs produced by the high-altitude-adapted line (WM) and by genetically similar but unselected stocks at sea level (D) were incubated at 3,100 m and at sea level, and the oxygen consumption was measured on individual eggs after the 17th day of incubation. At sea level, oxygen consumption rates of WM strain were less than that of SL stocks during late embryonic development. At 3,100 m, embryonic respriation of all strains was reduced, but to a much lesser degree in the high-altitude strain. It appears that a decreased metabolic activity of the late embryo coupled with a slower rate of embryonic developement is an important factor in the adaptation of the domestic fowl to high altitude.