Nutrient Digestibility of Mash, Steam Pelleted, and Extruded Barley and Faba Bean in Growing Pigs

Steam pelleting and extrusion are heat processing technologies that can increase the nutritional value of feedstuffs for pigs. Thus, the nutritional quality of barley and faba bean in mash, steam pelleted, and extruded forms was evaluated in a 2 × 3 factorial arrangement in growing pigs. The apparent ileal digestibility (AID) of GE, starch, CP, and AA, the standardized ileal digestibility (SID) of AA and CP, and the apparent total tract digestibility (ATTD) of GE were measured. The 2 feedstuffs were either fed as mash (2.8-mm hammer mill screen), steam pelleted (California Pellet Mill, Crawfordsville, IN), or extruded (X115, Wenger, Sabetha, KS). Seven crossbred ileal-cannulated barrows (54.3 ± 3.9 kg) were fed diets containing 96.5% of each of the 6 test feedstuffs and a N-free diet, in a 7 × 7 Latin square. Pigs were fed at 2.8 × maintenance DE for seven 9-d periods (sequentially 5 d adaptation and 2 d collections of feces and digesta). Data was analyzed by ANOVA using the mixed procedure. The 3 faba bean and 3 barley samples contained (DM basis) 28.2–29.7% and 12.0–12.3% CP, 8.62–9.90% and 4.66–5.73% ADF, and 4.37–4.39 and 4.44–4.46 Mcal/kg GE, respectively. Feedstuffs and processing interacted (P < 0.05) for AID and SID of CP, AA, AID of starch, ATTD of GE, DE value, and predicted NE value. Steam pelleting faba bean increased (P < 0.05) the AID of CP, Ile, Leu, Met, Val, and starch by 3-12%, the SID of these AA and Phe by 3–9% and of CP (84.9% vs. 89.2%), and the predicted NE value (4%), and tended to increase (P=0.06) the AID of GE (68.8% vs. 73.0%), compared to mash. Extruding faba bean increased (P < 0.05) the AID of Ile, Leu, Met, Phe, Thr, Val and starch by 3-10%, and the SID of these AA by 3-9%, and tended to increase (P=0.06) the AID of GE (68.8% vs. 72.8%), compared to mash. Steam pelleting barley increased (P < 0.05) the ATTD of GE (80.4% vs. 82.9%), DE value, and predicted NE value compared to mash. Extruding barley increased (P < 0.05) the ATTD of GE (80.4% vs. 83.1%), DE value, and predicted NE value compared to mash. The greater efficacy of heat processing for faba bean than barley indicates that the protein and starch matrix is more resistant to digestion in ground faba bean than in ground barley.