However,this was not the case. High mean alveolar-arterial oxygen pressure gradients were found in clinically healthy calves (8.5–11.7 mmHg), indicating poor transfer of oxygen from the alveoli into the pulmonary blood. Previous estimates of alveolar-arterial oxygen pressure gradients vary greatly, but generally agree that alveolar-arterial oxygen pressure is above what should be expected (10 mmHg), even in healthy calves at sea level