Four experiments were conducted to evaluate the effectiveness of a computer-controlled simulated digestion system (CCSDS) for predicting apparent metabolizable energy (AME) and true metabolizable energy (TME) using in vitro digestible energy (IVDE) content of feeds for roosters. In Exp. 1, the repeatability of the IVDE assay was tested in corn, wheat, rapeseed meal, and cottonseed meal with 3 assays of each sample and each with 5 replicates of the same sample. In Exp. 2, the additivity of IVDE concentration in corn, soybean meal, and cottonseed meal was tested by comparing determined IVDE values of the complete diet with values predicted from measurements on individual ingredients. In Exp. 3, linear models to predict AME and TME based on IVDE were developed with 16 calibration samples. In Exp. 4, the accuracy of prediction models was tested by the differences between predicted and determined values for AME or TME of 6 ingredients and 4 diets. In Exp. 1, the mean CV of IVDE was 0.88% (range = 0.20 to 2.14%) for corn, wheat, rapeseed meal, and cottonseed meal. No difference in IVDE was observed between 3 assays of an ingredient, indicating that the IVDE assay is repeatable under these conditions. In Exp. 2, minimal differences (<21 kcal/kg) were observed between determined and calculated IVDE of 3 complete diets formulated with corn, soybean meal, and cottonseed meal, demonstrating that the IVDE values are additive in a complete diet. In Exp. 3, linear relationships between AME and IVDE and between TME and IVDE were observed in 16 calibration samples: AME = 1.062 × IVDE - 530 (R(2) = 0.97, residual standard deviation [RSD] = 146 kcal/kg, P < 0.001) and TME = 1.050 × IVDE - 16 (R(2) = 0.97, RSD = 148 kcal/kg, P < 0.001). Differences of less than 100 kcal/kg were observed between determined and predicted values in 10 and 9 of the 16 calibration samples for AME and TME, respectively. In Exp. 4, differences of less than 100 kcal/kg between determined and predicted values were observed in 3 and 4 of the 6 ingredient samples for AME and TME, respectively, and all 4 diets showed the differences of less than 25 kcal/kg between determined and predicted AME or TME. Our results indicate that the CCSDS is repeatable and additive. This system accurately predicted AME or TME on 17 of the 26 samples and may be a promising method to predict the energetic values of feed for poultry.

Two experiments were conducted to develop a computer-controlled digestion system to simulate the digestion process of duck for predicting the concentration of ME and the metabolizability of gross energy (GE) in corn. In a calibration experiment, 30 corn-based calibration samples with a previously published ME concentration in 2008 were used to develop the prediction models for in vivo energetic values. The linear relationships were established between in vivo ME concentration and in vitro digestible energy (IVDE) concentration, and between in vivo metabolizability of GE (ME/GE) and in vitro digestibility of GE (IVDE/GE), respectively. In a validation experiment, 6 sources of corn with previously published ME concentration in 2008 randomly selected from the primary corn-growing regions of China were used to validate the prediction models established in the calibration experiment. The results showed that in calibration samples, the IVDE concentration was positively correlated with the AME (r = 0.9419), AMEn (r = 0.9480), TME (r = 0.9403), and TMEn concentration (r = 0.9473). Similarly, the IVDE/GE was positively correlated with the AME/GE (r = 0.95987), AMEn/GE (r = 0.9641), TME/GE (r = 0.9588), and TMEn/GE (r = 0.9637). The coefficient of determination greater than 0.88 and 0.91, and residual SD less than 45 kcal/kg of DM and 1.01% were observed in the prediction models for ME concentrations and ME/GE, respectively. Twenty-nine out of 30 calibration samples showed differences less than 100 kcal/kg of DM and 2.4% between determined and predicted values for 4 ME (AME, AMEn, TME, and TMEn) and for 4 ME/GE (AME/GE, AMEn/GE, TME/GE, and TMEn/GE), respectively. Using prediction models developed from 30 calibration samples, 6 validation samples further showed differences less than 100 kcal/kg of DM and 2% between determined and predicted values for ME and ME/GE, respectively. Therefore, the computer-controlled simulated digestion system can be used to predict the ME and ME/GE of corn for ducks with acceptable accuracy.