Relative humidity at moderate ambient temperatures: its effect on male broiler chickens and turkeys.

1. The effect of relative humidity (RH, 40% to 75%) at moderate ambient temperatures (Ta, 28 degrees and 30 degrees C) on the performance and thermoregulation of male broiler chickens and turkeys was studied at the age of 4 to 8 weeks. 2. Weight gain and food intake of male broiler chickens were significantly higher at 60% to 65% RH but food conversion efficiency was not affected by RH. In male turkeys, no effect of RH on performance was recorded. 3. Both chickens and turkeys controlled body temperature at normothermic levels during exposure to the experimental environmental conditions. 4. The rate of panting estimated from blood pH and pCO2 was lower in chickens exposed to 28 degrees C than to 30 degrees C. In turkeys, the rate was lower than that recorded in chickens at both Ta(s). 5. Plasma T3 was positively and significantly correlated with food intake. 6. It may be concluded that RH plays a role in the performance of chickens exposed to 30 degrees and 28 degrees C. whereas male turkeys must respond to RH at Ta >30 degrees C.