Adaptation of Chickens to Cool Temperature Brooding

The response of various strains of chickens to brooding temperatures of 32.2 C and 26.7 C was compared. Variation in response was assessed by mortality, weight gain, feed consumption and feed conversion (FCR), rectal temperature, relative yolk sac and liver weights, packed cell volume (PCV), plasma glucose, and plasma cholesterol. Brooding at 26.7 C increased mortality, FCR, PCV, and plasma cholesterol and decreased weight gain, relative yolk sac weights, and temporarily reduced rectal temperatures but did not affect relative liver weight or plasma glucose. The magnitude of these differences was affected by both strain of bird used and method of attaining the cool temperature. Maximal effect of brooding at 26.7 C was obtained if there was excessive air flow over the chicks when feed and water were placed outside the heated area. Although feed consumption, gain, feed conversion, and mortality were affected by the cool temperature brooding, regardless of feed and water location, the magnitude of the effect was greatly diminished if feed and water were placed under the heated hover area.