Hurwitz, S., Institute of Animal Science, Volcani Center, Bet Dagan, Israel.
Plavnik, I., Institute of Animal Science, Volcani Center, Bet Dagan, Israel.
Rosenberg, J., Institute of Animal Science, Volcani Center, Bet Dagan, Israel.
Ben-Gal, I., Institute of Animal Science, Volcani Center, Bet Dagan, Israel.
Talpaz, H., Institute of Animal Science, Volcani Center, Bet Dagan, Israel.
Bartov, I., Institute of Animal Science, Volcani Center, Bet Dagan, Israel.

Interactions between environmental temperature and dietary energy sources were evaluated in 6 to 9-wk and 9 to 12-wk-old turkeys using weight gain, feed efficiency, and carcass fat as response criteria. The dietary variables (soybean oil or glucose) were added in five or six increments at the expense of each other or of the fiber supplements, keeping the minima for protein and amino acid/energy constant. The resulting diets were fed to birds kept at 10 and 27 C. Duplicate experiments were conducted for each mode of dietary variable addition. Parallel increases in body weight gain and feed efficiency were obtained at the two temperatures when fat replaced carbohydrates or fiber, thereby raising dietary energy density. Some responses of weight gain and feed efficiency at the two temperatures were obtained also with a graded isocaloric addition of fat but the response was significant only at 27 C and not at 10 C. A greater response of gain and feed efficiency to energy supplied by dietary glucose was obtained at 10 C as compared with 27 C. Dietary fat supplementation resulted in increased deposition of carcass fat when given together with energy or isocalorically regardless of environmental temperature. Carcass fat was increased by glucose-energy at the low temperature only.