| A total of72crossbred barrows (Duroc×Large White×Landrace) were used to determine the net energy (NE) value and establish the NE prediction equations of seven ingredients in growing pigs using open-circuit respiratory chambers, five energy metabolism experiments were conducted in this study. In Exp.1,6crossbred barrows with an initial body weight (BW) of43±1.4kg were used to evaluate the fasting and regression methods to predict fasting heat production (FHP) in growing pigs. Six pigs were housed in open-circuit respiratory chambers for20d. A typical corn-soybean meal ration was fed throughout the experiment. The first7d were an adaptation to the diets, the next5d pigs were fed at2600kJ ME/kg BW0.6·-1, then fed at2×ME for maintenance (MEm) for3d, then fed at1RMEm for3d, and then fasted for2d. Fasting and regression methods were used to predict FHP. The predicted FHP for fasting and regression methods were774and694kJ/kg BW0.6·-1, respectively. In Exp.2,18barrows (initial BW=34±1.1kg) were selected to determine the NE value of corn using direct and substitution methods. Pigs were randomly allotted to3diets. The first diet (Corn) was formulated to contain97.5%corn and was used to determine the energy content in corn directly, while the second diet (Corn-Soybean meal-Basal diet) was formulated to contain72.5%corn and25.0%soybean meal, and the third diet (Corn-Soybean meal-Test diet) substituted40%of the energy supplied by the Corn-Soybean meal-Basal diet with corn. These2diets were used to calculate the energy content in corn using the substitution method. The DE, ME, NE content and k value in corn determined by the direct method were16.65,16.31,13.21MJ/kg DM, and80.99%, respectively, which were not different from the DE, ME, NE content and k value in corn determined by the substitution method which were16.42,16.15,13.69MJ/kg DM, and84.77%, respectively. In Exp.3,24barrows (initial BW=36±1.4kg) were used to determine the NE of soybean meal by the different basal diets methods for growing pigs. Pigs were randomly allotted to4diets. Three diets (1,2, and3) and two diets (3and4) were used to determine the energy value of soybean meal by using the corn basal (Corn-Basal) diet or the corn-soybean meal basal (Corn-SBM-Basal) diet method, respectively. The average DE, ME, NE, and RE content in soybean meal (17.36,16.52,10.62, and5.06MJ/kg DM, respectively) determined by the Corn-SBM-Basal diet method, was not different from the Corn-Basal diet method. In Exp.4,12barrows (initial BW=27±0.5kg) were used to determine the NE value of wheat bran, wheat, dried distillers grains with soluble (DDGS), canola meal, and cottonseed meal, and establish prediction equations for NE content of ingredients. Pigs received one corn-soybean meal basal diet and five experimental diets containing wheat bran, wheat, DDGS, canola meal, and cottonseed meal, respectively. Measurements were conducted on6pigs per experimental diets. The average values for wheat bran, wheat, DDGS, canola meal, and cottonseed meal were7.78,11.44,10.21,8.38, and7.32MJ/kg DM for NE, respectively. Stepwise regression analysis performed by the chemical composition and the NE value of the ingredients, the NE values could be accurately predicted from the chemical characteristics. The equation was as follows:NE=1.46+0.63GE-0.37ADF, with R2=0.94, residual standard deviation (RSD)=0.54MJ/kg, and P<0.01. In Exp.5,12barrows (initial BW=35±1.5kg) were randomly allotted to6mixed diets formulated by corn, soybean meal, wheat bran, wheat, DDGS, canola meal, and cottonseed meal, and each mixed diet was fed to six pigs. The chemical composition of each mixed diet was determined, and the results were used to establish prediction equations for the NE content from chemical characteristics. The equation for NE was established by the stepwise regression between chemical composition and energy value of the16diets (Include10diets in Exp.2,3and4), and the equation was as follows:NE=-10.19+0.97DE+0.08Starch+0.05ADF with R2=0.84, RSD=0.46MJ/kg, and P<0.01. |
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