Cross relationships between growth performance, growth composition and feed composition in broiler chickens,...

The study presented here used experimental data obtained from 42 articles to calculate the cross relationships between daily feed intake (DFI), feed composition (AMEn and CP), BW, daily weight gain (DG), mean age (A), and composition (FCG and PCG; fat and protein, respectively) of growth in broilers. All of the experiments selected were conducted at standard temperature and with ad libitum feeding. The articles in this database were published from 1980 to 2015, and represented a total of 12,277 broilers, 57 trials, and 384 basic treatments. Data ranged from 3 to 66, 0.077 to 3.322, 7.10 to 15.37, and 7.3 to 35.0 for A (d), mean BW (kg), AMEn (MJ/kg) and CP (%), respectively. Equations were established from regression calculations to calculate daily heat production as a function of BW, daily AME intake (MEI) as a function of BW, DG, FCG and PCG, PCG as a function of A and FCG, and FCG as a function of BW, protein efficiency (PE), AMEn, and CP. The combination of these equations expressing MEI, PCG, or FCG with equations expressing the definitions of PE, AME (from AMEn), and DFI (from MEI) constituted a system of 6 equations which could be used to determine DFI values from the values of AMEn, CP, A, BW, and DG. Using the values of AMEn, CP, A, BW, and DG from the database, the DFI values calculated with this system of equations showed a reasonable correlation with the DFI values measured (R2=0.880). This system of 6 equations yielded values for DFI, PE, PCG, and FCG that were in agreement with the classical effects produced by increased CP values, or by reduced fat deposition associated with genetic selection for leanness. This system of 6 equations might thus be considered an interesting framework for future nutritional modelling systems. Regressions predicting feed efficiency as a function of AMEn, CP, DG, and BW, or as a function of AMEn, FCG, DG, and BW showed R2 values of 0.767 and 0.747, respectively.