Prediction of digestible energy of feed ingredients for growing pigs using a computer-controlled simulated digestion system.

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The objectives of this experiment were to evaluate in vitro DE (IVDE) of selected feed ingredients using a computer-controlled simulated digestion system (CCSDS) and predict DE of ingredients for growing pigs. Samples of 6 ingredients with a wide range in energy and nutrient profile were collected. The CP and GE contents ranged from 9.9 to 50.9% and 4,493 to 4,841 kcal/kg (DM basis), respectively. Two control diets were formulated to achieve different CP contents (12.5 and 20.0%). Three experimental diets were formulated by replacing 20% of the high-CP control diet with corn, wheat, or wheat bran, whereas 3 additional diets were formulated by replacing 20% of the low-CP control diet with soybean meal, rapeseed meal, or cottonseed meal. The DE was determined using barrows (n = 24; initial BW = 35.9 ± 1.9 kg) in 2 periods with 6 observations per diet treatment and ranged from 2,769 to 4,368 kcal/kg. The equation for the DE content (kcal/kg of DM) using chemical components as independent variables was DE = 4,186 + 0.06 × CP + 79.33 × ether extract - 14.57 × NDF - 47.99 × ADF, with R(2) = 0.995, residual SD (RSD) = 89.5 kcal/kg, CV = 2.4%, and P = 0.10 (chemical component values; %). The IVDE ranged from 2,289 to 3,724 kcal/kg and was highly related to the determined DE content of the ingredients (R(2) = 0.91, RSD = 193 kcal/kg, and CV = 5.2%). The relationship between IVDE:GE and DE:GE was very high (R(2) = 0.93, RSD = 3.8%, and CV = 4.7%). The average values of CV for IVDE (0.75%) and IVDE:GE (0.73%) were less than that for determined DE (2.58%) and DE:GE (2.54%), respectively. In conclusion, the IVDE content determined, using a CCSDS with relatively high accuracy and acceptable repeatability, might be used to predict DE of feed ingredients for growing pigs.