Digestion kinetics of protein sources determined using an in vitro chicken model

Abstract

This paper presents digestion kinetics data for commonly available high protein feed ingredients using an in vitro model that mimics the gastric and intestinal phases of chickens. Soybean meal (SBM), corn gluten meal (CGM), corn distiller dried grains with solubles (CDDGS), porcine meal (PCM), fish meal (FM), canola meal (CM), meat and bone meal (MBM), feather meal (FEM) and blood meal (BM) were digested in 6 replicate tubes. Meal sample equivalent to 500 mg crude protein (CP) was digested with 28,260 units of pepsin in 50 mL polyethylene centrifuge tubes for 30 min in a shaking water bath at 41 °C. After gastric digestion, tube pH was adjusted to 7 ± 0.5 using NaOH. A 9.5 mL volume of sodium acetate buffer (pH 12.5) and 6.5 mL pancreatin (trypsin = 30,667 BAEE units/mL, chymotrypsin = 2157 BTEE units/mL and elastase = 7 units/mL), and 3 glass marbles were placed in the tube which were incubated for 180 min at 41 °C in a water bath. Tubes were sampled at 0, 15, 30, 45, 60, 90, 120, 150 and 180 min of the intestinal phase and digestibility (DIG) determined calorimetrically with ninhydrin reagent per time point. The DIG data were fitted to the model P = A + B (1-e-kd*t) using the PROC NLIN procedure of SAS 9.4 and all constants were analyzed using the PROC Mix procedure. The modeled predicted (P) CP DIG (%) of the meals were SBM 87, FM 88, PCM 79, CGM 73, MBM 56, CM 82, BM 47, FEM 48 and CDDGS 58. Estimated fractional digestion rate (kd) values for BM and FEM were 0.062 and 0.054, respectively, while MBM, CGM, FM, PCM, CM, SBM and CDDGS were 0.046, 0.041, 0.040, 0.038, 0.035, 0.027 and 0.017, respectively. In conclusion, protein digestion of high protein meals was determined with an in vitro technique, which provided the opportunity to categorize the ingredients based on their digestion kinetics as well as extent of digestion.