Dietary fat and protein interactions in the broiler

An experiment was conducted to study the interrelationships between dietary fat and protein levels in the regulation of lipid metabolism in the broile r chicken, Birds were fed diets containing 300, 600, or 1,200 kcal ME from fat (corn oil) with either 124 or 190 g CP/kg. Two additional experimental diets contained 234 or 285 g CP and 300 kcal ME from fat. Regardless of fat lever, birds fed the diets containing 124 g CP/kg weighed less and were le ss efficient than birds fed diets containing 190 g CP/kg. The diet containi ng 600 kcal as fat decreased Lipogenesis and malic enzyme activity (P < 0.0 5) in birds fed the diet containing 190 g CP/kg diet, but not in birds fed the diet containing 124 g CP/kg. Birds fed the latter level of protein requ ired at least 1,200 kcal as fat to express any significant decrease in lipo genesis or malic enzyme activity (P < 0.05). Dietary fat did not affect pla sma levels of triiodothyronine (T-3), thyroxine (T-4), or insulin-like grow th factor-I (IGF-I). Feeding diets containing 124 g CP/kg resulted in decre ased plasma T-4 and IGF-I and elevated T-3 (P < 0.05). Increasing dietary p rotein (compared to increasing dietary fat) increased body weights, IGF-I, T-4 and decreased lipogenesis, malic enzyme activity, and T-3. Both of thes e regimens involve decreasing dietary carbohydrate at equal rates, but resu lts differed. Although replacement of dietary carbohydrates with either fat or protein reduce precursors for fat synthesis, both energy sources have a dditional unique effects on metabolism. Dietary protein levels modulate met abolic effects of dietary fat.