Effects of substitution between fat and protein on feed intake and its regulatory mechanisms in broiler chickens: energy and protein metabolism and diet-induced thermogenesis

Laboratory for Physiology and Immunology of Domestic Animals, Department of Animal Production, KU Leuven, Kasteelpark Arenberg 30, 3001 Leuven, Belgium.

The objective of this study was to investigate the effect of dietary macronutrient ratio on energy, protein, and lipid metabolism and on the involvement of diet-induced thermogenesis in feed intake regulation of broiler chickens. Male broilers were reared from 1 to 7 wk on isoenergetic diets with substitutions between fat and protein and similar carbohydrate content [low protein (LP): 126 vs. 242 g of protein/kg; low fat (LF): 43 vs. 106 g of fat/kg]. Every week from 21 d onward, 3 chickens per group were placed in open-circuit respiratory cells to measure energy and protein metabolism in fasting, short-term refeeding (5 h) and ad libitum conditions. As LP chickens had a significantly lower BW from 2 wk onward, all parameters were expressed per kilograms of metabolic BW. Feed intake, gross energy intake, and apparent metabolizable energy intake were significantly higher in LP than LF birds. The excessive energy relative to protein intake resulted in significantly increased heat production and energy retention as fat. The latter effect and a significantly increased respiratory quotient indicated higher de novo lipogenesis in the LP chickens. Furthermore, the efficiency of protein retention was significantly better in LP broilers. Neither diet-induced thermogenesis nor feed intake during a 5-h refeeding period was affected by diet composition. Our results indicate that isoenergetic substitution of fat for protein has a strong effect on growth and on energy and protein balance in broilers. The theory linking diet-induced thermogenesis to feed intake could not be corroborated or countered, and further research is warranted.

This article has been cited by other articles:

				J. L. Chen, G. P. Zhao, M. Q. Zheng, J. Wen, and N. Yang Estimation of Genetic Parameters for Contents of Intramuscular Fat and Inosine-5'-Monophosphate and Carcass Traits in Chinese Beijing-You Chickens Poult. Sci., June 1, 2008; 87(6): 1098 - 1104. [Abstract] [Full Text] [PDF]

				I. Bouvarel, A. M. Chagneau, P. Lescoat, S. Tesseraud, and C. Leterrier Forty-Eight-Hour Cycle Sequential Feeding with Diets Varying in Protein and Energy Contents: Adaptation in Broilers at Different Ages Poult. Sci., January 1, 2008; 87(1): 196 - 203. [Abstract] [Full Text] [PDF]

				Q. Swennen, P.-J. Verhulst, A. Collin, A. Bordas, K. Verbeke, G. Vansant, E. Decuypere, and J. Buyse Further Investigations on the Role of Diet-Induced Thermogenesis in the Regulation of Feed Intake in Chickens: Comparison of Adult Cockerels of Lines Selected for High or Low Residual Feed Intake Poult. Sci., September 1, 2007; 86(9): 1960 - 1971. [Abstract] [Full Text] [PDF]

				Q. Swennen, E. Delezie, A. Collin, E. Decuypere, and J. Buyse Further Investigations on the Role of Diet-Induced Thermogenesis in the Regulation of Feed Intake in Chickens: Comparison of Age-Matched Broiler versus Layer Cockerels Poult. Sci., May 1, 2007; 86(5): 895 - 903. [Abstract] [Full Text] [PDF]