Predicting energetic values of cereal grains and byproducts using a computer-controlled simulated digestion system for growing pigs

Abstract

The objective of this study was to predict the apparent total tract digestibility (ATTD) of gross energy (GE), digestible energy (DE), and metabolizable energy (ME) of cereals and byproducts using an in vitro digestion procedure automatically progressed in a computer-controlled simulated digestion system (CCSDS) for growing pigs. In in vivo test to determine the ATTD of GE, DE and ME of feed ingredients, 15 barrows (30.2 ± 2.4 kg of initial body weight) were allotted to a 15 × 6 Youden square design with 15 experimental diets in 6 periods to give 6 replicates per diet. Diets included a corn-soybean meal-based basal diet and 14 test diets formulated with 14 samples of cereals and byproducts. The in vitro digestible energy (IVDE) and IVDE/GE were determined using CCSDS with 5 replicates for each sample. Principal components analysis showed that similar positions of samples were observed on a two-dimensional plot of PC1 and PC2 extracted from chemical composition and each of DE, ME, or IVDE. The ratios of IVDE to DE or ME among 14 samples ranged from 87.7–110.4 % and 91.1–112.9 %, but ranged from 97.8–103.5 % or 100.2–105.7 % when both paddy rice and wheat shorts were excluded in consideration of lever effect. Models to predict DE and ME from IVDE were DE = 0.7428 × IVDE + 945 (R² = 0.71, root mean square error (RMSE) = 157 kcal/kg DM, P < 0.01), ME = 0.7465 × IVDE + 839 (R² = 0.76, RMSE=139 kcal/kg DM, P < 0.01) when 14 samples were included, but regression equations were DE = 0.6924 × IVDE + 1173 (R² = 0.91, RMSE = 49 kcal/kg DM, P < 0.01) and ME = 0.6876 × IVDE + 1098 (R² = 0.95, RMSE = 34 kcal/kg DM, P < 0.01) when paddy rice and wheat shorts were excluded. Our results indicate that IVDE determined with a novel CCSDS can precisely predict the DE and ME of cereals and byproducts with lower fiber content (ADF < 6.01 % DM) for growing pigs.