Twelve steers were used to compare the blood gas and acid-base status. The animals were randomly divided in three equal groups according to the following diets: 1- adequate, for gaining 600g/head/d ; 2- protein and energy levels to meet the maintenence; 3- protein and energy 20% below the maintenance levels. One hundred thirty-two arterial blood (caudal auricular artery) or venous blood (jugular vein) were continuously sampled for 11 fortnights. At the end of the experiment steers from groups 2 and principally 3 presented a moderate level of metabolic acidosis. Higher pH and pO2 levels were found in arterial blood; conversely, higher level of bicarbonate, TCO2, BE and pO2 levels were found in the venous blood. High correlation was found in the pH (r = 0.81), bicarbonate and TCO2 (r = 0.94) between venous and arterial blood; median correlation but significant in the pCO2 (r = 0.56) and lack of correlation in the pO2 (r = -0.06). The higher the pCO2, the higher the bicarbonate (r = 0.54) and TCO2 (r = 0.56) concentration. In spite of the small differences of pH, bicarbonate, TCO2 and even pCO2 between venous and arterial blood the values of arterial blood can be predicted adequately from the venous blood either in healthy steers or steers with moderate metabolic acidosis. When respiratory changes are concerned arterial blood must be collected for evaluating pO2. It was easier to sample venous blood than arterial blood.
blood gas; pH; pO2; pCO2; TCO2; BE; bicarbonate; bovine
