Ambient temperature: a factor affecting performance and physiological response of broiler chickens.

An experiment was conducted to elucidate the influence of four constant ambient temperatures (20 degrees, 25 degrees, 30 degrees and 35 degrees C) on the performance and physiological reactions of male commercial broiler chicks from 3 to 7 weeks of age. A 12 h light-dark cycle was operated, while relative humidity and air circulation were not controlled. Exposure of broiler chickens to the 20 degrees, 25 degrees, 30 degrees and 35 degrees C treatments showed highly significant (P less than 0.0001) depression in growth rate, food intake and efficiency of food utilization, and a significant increase in water consumption for the 30 degrees and 35 degrees C groups. Mortality was, however, not affected by the temperature treatments. Changes in physiological status, such as increased rectal temperatures, decreased concentration of red blood cells, haemoglobin, haematocrit, and total plasma protein were observed in birds housed in the higher temperature (30 degrees and 35 degrees C) environments. Moreover, in these broiler chickens, there was an increased blood glucose concentration and a decreased thyroid gland weight. These results indicate that continuous exposure of broiler chickens to high ambient temperatures markedly affects their performance and physiological response.