Predicting metabolizable energy of soybean meal and rapeseed meal from chemical composition in broilers of different ages.

This study determined metabolizable energy (ME) and developed ME prediction equations for broilers based on chemical composition of soybean meal (SBM) and rapeseed meal (RSM) using a 2 × 10 factorial arrangement of age (11 to 14 or 25 to 28 d of age) and 10 sources of each ingredient. Each treatment contained 6 replicates of 8 broilers. The ME values were determined by total collection of feces and urine. Principal components analysis (PCA) of the chemical composition clearly revealed distinct differences in SBM and RSM based on a principal components (PC) score plot. The nitrogen-corrected apparent metabolizable energy (AMEn) of SBM was higher in broilers from 25 to 28 than 11 to 14 d of age (P = 0.013). Interactions between broiler age and ingredient source affected apparent metabolizable energy (AME) of SBM and ME of RSM (P < 0.05). The ME of SBM in 11 to 14 and 25 to 28-day-old broilers were estimated by crude protein (CP) content (R≥ 0.782; SEP ≤ 83 kcal/kg DM; P < 0.001). The AME and AMEn of RSM in 11 to 14-day-old broilers were estimated by ether extract (EE), ash and acid detergent fiber (ADF) (R = 0.897, SEP = 106 kcal/kg DM; P = 0.002), and by EE and ash (R = 0.885, SEP = 98 kcal/kg DM; P = 0.001), respectively. The AME and AMEn of RSM in 25 to 28-day-old broilers were estimated by ash and ADF (R = 0.925, SEP = 104 kcal/kg DM; P < 0.001) and by ash and neutral detergent fiber (NDF) (R = 0.921, SEP = 91 kcal/kg DM; P < 0.001), respectively. These results indicate that ME of these 2 plant protein ingredients are affected interactively by chemical composition and age of broilers. This study developed robust, age-specific prediction equations of ME for broilers based on chemical composition for SBM and RSM. Overall, ME values can be predicted from CP content for SBM, or EE, ash, ADF, and NDF for RSM.