Effect of different dietary levels of protein on fat deposition in broilers divergently selected for high or low abdominal adipose tissue.

1. Male broilers selected for high (HF) or low (LF) abdominal fat were fed from 8 to 53 d of age on diets containing different concentrations of protein: according to N.R.C. (1984) recommendations (IP), 14% lower (LP) or 14% higher (HP). 2. The growth of LF birds fed on the LP diet was depressed until 35 d of age, but did not differ from the other groups later on. 3. The HF birds had heavier adipose tissues (AT) (g/kg body weight) than the LF birds. Significant line by diet interactions indicated a difference in magnitude of the response of the lines to dietary protein content. 4. Fat concentration of the AT and skin was higher, and in the tibia lower in the HF than in the LF birds. The fat concentration in liver and in breast muscle was not affected by line or by diet. 5. The ratio of saturated plus monoenoic fatty acids to polyenoic fatty acids, considered as an index of fat synthesis, was higher in the abdominal adipose tissue (AAT) of HF compared with LF birds. In AAT, liver and in breast muscle, this ratio was inversely related to dietary protein content.