Development of Prediction Equations for Digestible and Metabolizable Energy in 15 Cereal Processing By-Products Fed to Growing Pigs

The study was conducted to determine the nutrient digestibility and digestible (DE) and metabolizable energy (ME) of 15 cereal processing by-products and to develop prediction equations for DE and ME based on the chemical composition in growing pigs. A total of 36 crossbred pigs were chosen and divided into three blocks according to a three 12 x 3 Youdin square experimental design. Twelve pigs in each block were allocated into six diets including a basal diet and five test diets. The feeding experiment included three periods, and each dietary treatment contained six replicates. Each period lasted 12 days, including 7 d of dietary adaption and 5 d of total feces and urine collection. The results showed that the coefficients of variation for EE, NDF, ADF, CP, and GE among 15 cereal processing by-products were 86.78%, 49.82%, 51.14%, 14.95%, and 6.26%, respectively. There were significant differences in DE, ME, and ME/DE (DM basis) among 15 cereal processing by-products (p < 0.05), ranging from 11.55 MJ/kg to 17.64 MJ/kg, from 10.90 MJ/kg to 17.40 MJ/kg, and from 89.41% to 98.63%, respectively. The digestibility of GE, DM, NDF, ADF, and CP showed a significant difference among 15 cereal processing by-products (p < 0.05). The DE and ME contents showed a negative correlation to NDF and ADF (p < 0.05), and the prediction equations for DE and ME (as-fed basis) were DE (MJ/kg) = -0.4597 x ADF (%) + 0.5988 x GE (MJ/kg) + 6.0138 (R-2 = 0.74; p < 0.05) and ME (MJ/kg) = 1.0440 x DE (MJ/kg) - 1.1235 (R-2 = 0.98; p < 0.05). On a DM basis, the optimal prediction equations for DE and ME were DE (MJ/kg DM) = -0.1451 x NDF (%) + 0.3026 x CP (%) + 13.8595 (R-2 = 0.72; p < 0.05) and ME (MJ/kg DM) = 1.1155 x DE (MJ/kg DM) + 0.0363 x ADF (%) - 2.3412 (R-2 = 0.99; p < 0.05). In conclusion, there were large variations in the chemical composition, nutrients digestibility, and available energy among the 15 different samples of cereal processing by-products. It is reasonable to develop prediction equations for DE and ME based on the chemical composition of cereal by-products for growing pigs.