The effect of constant and diurnal cyclic temperatures on performance and blood system of young turkeys

At high ambient temperature (T-a = 35 degrees C) weight gain and feed intak e declined significantly. At 15 degrees C weight gain was similar to that a t 25 degrees C, at the cost of increased feed intake. Under diurnal cyclic temperature, weight gain and feed intake were significantly lower than in t he average corresponding temperature. In all treatments the turkeys' body temperature (T-b) was at the lower leve l of normothemia known for broiler chickens at a similar age. The blood system compensated for changes in T-a by increasing hematocrit, h emoglobin concentration and heart muscle weight at low T-a, and by plasma e xpansion and increased panting at high T-a. Plasma (T-3) concentration was positively correlated with feed intake and w eight gain. (C) 1999 Elsevier Science Ltd. All rights reserved.