Effect of dietary polyunsaturated/saturated fatty acid ratio on heat production and growth performance of chicks under different ambient temperature

Two trials were conducted to investigate the influence of dietary polyunsaturated/saturated fatty acid ratio (P/S) on growth performance and heat production (HP) of chicks under different ambient temperature (Ta). With the exception of Ta, all other treatment processes for two trials were the same. In each trial, 120 Arbor Acres 1-day-old male chicks were allotted to 2 (P/S, 0.6 or 2.4) x 2 (high or low Ta) factorial design with six replicates of five chicks each treatment. Chicks were reared in wire-floored metabolism cages in two temperature-con trolled chambers, and were exposed to high Ta (37 and 38 degrees C at the first day for trial 1 and 2, respectively, and decreased 0.2 degrees C/day) or low Ta (33 and 28 degrees C at the first day for trial 1 and 2, respectively, and decreased 0.3 degrees C/day), for 3 weeks. Chicks were fed ad libitum. Body weight, feed intake and gain:feed were recorded. Excreta were collected for determining metabolizable energy. Energy retention was measured by the comparative slaughter technique; HP was calculated as the difference between metabolizable energy intake and body energy retention. The results showed that high Ta decreased weight gain (P < 0.01) and feed intake (P < 0.01) in both trials, improved gain:feed in trial 2 (P < 0.01), and decreased HP in trial 2 (P < 0.01) of chicks during 0-3 weeks of age. Increasing dietary P/S did not affect the growth performance and HP of chicks during 0-3 weeks of age. No Ta x dietary P/S interaction among growth performance and HP in chicks was observed. In summary, increasing dietary P/S did not affect HP, therefore, it is neither detrimental to the growth of chicks reared under high Ta nor is beneficial to the growth of chicks reared under low Ta. (c) 2004 Elsevier B.V. All rights reserved.