Effect of two-day temperature exposure of neonatal broiler chicks on growth performance and body composition during two weeks at normal conditions.

Newly hatched chicks were allotted to five different climatic treatment groups (28 to 32, 32 to 34, 34 to 35, 35 to 37, and 37 to 40 C) for 2 days after hatch during which feed and water were withheld. Their performance was measured for 2 wk and compared with control chicks kept under normal conditions. During the 2 days of climatic treatment, chicks lost weight of 5.3, 5.4, 6.7, 8.5, and 10.1 g, respectively, but control chicks grew 16.0 g. During 14 days of feed intake, chicks of the highest treatment group grew significantly less (217.5 g) than controls (267.7 g). Also, feed intake was significantly lower (292 versus 386 g). In the group exposed to 37 to 40 C, feed conversion decreased significantly from 1.43 to 1.37 g:g and mortality increased to more than 49%. Body composition of DM, protein, fat, and ash was also estimated. Chicks previously exposed to 37 to 40 C had significantly lower values for the gain in body components: DM (18.49 g), protein (7.13 g), fat (8.75 g), and ash (2.62 g) per chick at 2 wk. The ratios water:protein gain and fat:protein gain after posthatching heat exposure were decreased from 3.82 to 3.45 g:g and .76 to .67 g:g, respectively, whereas the ratio of gain in energy retention:weight gain was similar to that of controls.