Cardio-pulmonary function values in double-muscled cattle during muscular exercise.

Eleven double-muscled calves of the Belgian White and Blue breed and eleven Friesian calves have been investigated at rest, during exercise on a treadmill (11% incline; speed 1.3 m.sec-1) and 10 and 30 minutes after the end of this exercise. Blood gases and acid-base status were determined in mixed venous and arterial blood sampled from the pulmonary and the carotid artery respectively. Expired gases were collected in a balloon. The time of collection, volume of expired gases and fractional O2 and CO2 concentrations in expired gases were measured. In double-muscled calves, inadequate oxygen intake and carbon dioxide elimination were demonstrated by the increase in the carbon dioxide tension (PaCO2) and in the hydrogen ion concentration [H+]a and the decrease in the oxygen tension (PaO2) in arterial blood during exercise. In Friesian calves, an adequate increase in oxygen intake occurred and no acidosis was recorded. A metabolic acidosis explained by only a 1.5-fold increase in the cardiac output and by the small increase in haemoglobin concentration was recorded in double-muscled calves. It was concluded that some aspects of the cardio-pulmonary and metabolic responses to exercise in double-muscled calves can be related to their inability to greatly increase their O2 consumption.