Age and gender influence the cardiorespiratory function and metabolic rate of broiler chicks during normocapnia and hypercapnia.

Pulmonary ventilation (V˙(E)), body temperature (Tb), mean arterial pressure (MAP), heart rate (f(H)) and metabolic rate (V˙(O2)) were measured in 10 (d10)- and 21 (d21)-day-old male and female chicks exposed to 7% CO2. Under normocapnia, V˙(E) was higher in d10 chicks than in d21 due to a higher tidal volume; in females a higher respiratory frequency (f(R)) was also observed. The d10 birds presented higher f(H) and V˙(O2).