ABSTRACT
Respiratory rate (f) and tidal volume (VT) have been measured at normal and at warm ambient temperatures (Ta) in adult domestic fowl by means of a whole body plethysmograph. Resting values of f = 23 ± 9 min−1 and of VT = 25·6 ± 0·9 ml min−1 were found. At Ta 30, 35 or 40 °C f increased in direct relation to the severity of the heat stress reaching a maximum value of 273 ±12 min−1; VT fell uniformly in all three climates to a minimum of 9·0 ± 0·5 ml. Total ventilation 
showed a linear relation with f during first-phase panting. Second-phase panting occurred only at Ta 40 °C ; K increased at first but subsequently fell as the decline in f became more pronounced.
