Effect of hypobaric hypoxia on slow- and fast-growing chickens fed diets with high and low protein levels.

The occurrence of pulmonary hypertension syndrome in fast-growing broiler chickens and slow-growing leghorns was studied. In two similar trials, broiler chickens and white leghorns were placed either at low altitude (295 m) or in hypobaric chambers (simulated high altitude of 2054 m) and fed either a high- (22%) or low-protein (17%) ration. Right ventricular hypertrophy as measured by right-ventricle:total-ventricle (RV:TV) weight ratio was used as an indicator of pulmonary hypertension. The leghorns did not develop pulmonary hypertension as the result of polycythemia induced by simulated high altitude. Compared with low-altitude broilers and leghorns, broilers reared at high altitude responded with significantly higher hematological values and 56% ascites mortality because of right ventricular failure from pulmonary hypertension, as measured by an increased RV:TV ratio.