Effect of cycling temperature on growth, energy metabolism and nutrient retention of individual male turkeys.

1. Each week, from 12 to 20 weeks of age, male turkeys of a heavy strain were subjected to cool (C; 16 degrees C), hot (H; 29 degrees C), and cycling temperatures, and fed on a standard diet ad libitum for 4 d. Lighting was intermittent, 3 h on, 3 h off. Food was given when lights were on. Those given cycling temperatures (3 h C; 3 h H) were given food and light during the cool (eat-when-cool, EC) or hot (EH) periods. 2. Birds in all treatments gained similar amounts of weight from 12-14 weeks of age. Thereafter, birds in C maintained gains, the body weight gains of birds in EC and EH declined moderately and birds in H lost weight. 3. Birds in C produced more metabolic heat. Those in H showed increased heat production as they became older. 4. Protein retention was greater in turkeys in C, EC and EH. It was lower in H, becoming negative between 18-20 weeks of age. Birds in H suffered body fat losses which increased with age. 5. Birds in EH and EC gained similar amounts of body weight. Birds in EH exhibited lower heat production and greater energy retention than those in EC. 6. Body temperatures were higher in H than in the other environments.