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 degrees C f increased in direct relation to the severity of the heat stress reaching a maximum values of 273 +/− 12 min-1; VT fell uniformly in all three climates to a minimum of 9.0 +/− 0.5 ml. Total ventilation (V) showed a linear relation with f during first-phase panting. Second-phase panting occurred only at Ta 40 degrees C; V increased at first but subsequently fell as the decline in f became more pronounced.

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