Environmental temperature and choice feeding of the broiler.

1. Broilers were kept under environmental temperature regimens of 16, 21, 26 or 31 degrees and given, 22--57 d of age, either a complete diet or free-choice of whole wheat and a higher-protein food containing either 252 or 516 g crude protein (nitrogen x 6.25)/kg. 2. Broilers maintained at 16 and 21 degrees consumed food at a significantly higher rate than those kept at 26 degrees and the latter had a significantly higher food intake rate than broilers kept at 31 degrees, for each feeding treatment. Compared with 21 degrees the 57 d body-weight of broilers kept at 26 degrees and 31 degrees was significantly reduced. 3. When kept under the 16, 21, 26 and 31 degrees regimens, the amount of whole wheat in the food consumed by the broilers choice-fed with wheat and the 252 g crude protein/kg food was 56, 55, 48 and 46% respectively. The corresponding values for the broilers on the second choice-feeding treatment were 80, 76, 79 and 72%. 4. Except for a single instance the choice-fed broilers grew at a significantly slower rate than broilers given the complete diet.