Ablation of Rostral Conchae does not affect Heat Exchange in the Upper Respiratory Tract of the Domestic Chicken

SMSU Event Center BC

Respiratory turbinates in the nasal cavities of endothermic vertebrates are known to play an important role in heat conservation and dissipation. In birds, cartilaginous rostral and middle conchae protrude inward from the nasal capsule, increasing the surface area of the respiratory epithelium, decreasing the distance to the respiratory airstream, and thus improving the efficiency of heat and water exchange. How important either of the conchae is to heat conservation at low ambient temperatures and dissipation at high temperatures is not known. To determine the role of the rostral concha, we performed a bilateral surgical excision in hatchlings of the domestic chicken, and sham operated control animals. We measured exhaled air temperatures in adult chickens (n=5 per treatment) under mild sedation across a 10-40°C range and at 30% relative humidity. With the animals breathing with a closed beak, there were no significant differences in exhaled air temperatures at the external nares between experimental and control animals at any of the tested ambient temperatures. When breathing with an open beak, exhaled air temperatures at the glottis were significantly different only at ambient 40°C, with the experimental animals having a slightly (1.0°C) warmer breath, but also a slightly higher (0.9°C) core temperature (t-test, p<0.05). Our results suggest that either the rostral concha does not participate in heat exchange in the nasal cavity, or the middle concha compensates for the loss of its rostral counterpart. Loss of the rostral concha may exert an effect on the trachea’s ability to dissipate heat at high ambient temperatures, but does not improve its countercurrent exchange at low temperatures.