Contribution a l'etude de l'hypercapnie aigue et chronique chez la poule ( Gallus domesticus)

Abstract

1. 1. We have determined the normal ranges of variations of H +, HCO − 3 and CO 2− 3 ion levels in the blood of 96 laying hens during acute and chronic hypercapnia. The atmospheric content of CO 2 was raised to 3 per cent and acute hypercapnia was studied during periods of 2–7 hr; the chronic condition was measured after the birds had been exposed to the same environment for 3 months. 2. 2. The relationship between venous blood [H +] and pCO 2 is shown in Fig. 1 with the significance band at an estimated 95 per cent probability; Fig. 2 presents similarly the increase of HCO − 3 level. The buffer capacity of the blood increases to a much higher level during a chronic respiratory acidosis than during a brief exposure to CO 2. 3. 3. In Fig. 3, the calculated CO 2− 3 blood level is plotted against the pCO 2; it appears that the CO 2− 3 level is enhanced by the chronic exposure to 3 per cent of CO 2 but reduced during the acute respiratory acidosis. 4. 4. These results show that laying hens, like mammals, react to chronic hypercapnia by increasing the body buffer capacity, probably through renal generation of bicarbonate. The importance of CO 2− 3 ion level in the blood is also discussed in relation to eggshell formation according to the previous hypothesis of Simkiss (1967).