Effect of a carbohydrase mixture on ileal amino acid digestibility in extruded full-fat soybeans fed to finishing pigs1,2

Abstract

Extrusion technology has been used successfully to improve the nutritive value of full-fat oilseeds via shear force and heat applied during passage through the extruder, exposing more peptide bonds to enzymatic hydrolysis. However, the fibrous portion of the seeds is largely intact after extrusion. Therefore, application of carbohydrase mixtures targeting nonstarch polysaccharides might further improve the nutritive value of extruded full-fat oilseeds. This hypothesis was investigated in a study involving 6 ileal-cannulated barrows (average initial BW = 75.0 kg) fed extruded full-fat, soybean- (FFSB) based diets, without or with a carbohydrase mixture (CM) to determine apparent ileal digestibility (AID) of energy and standardized ileal digestibility (SID) of AA. The CM supplement provided 500, 50, 400, 1200, 450, and 45 units of pectinase, cellulase, mannanase, xylanase, glucanase, and galactanase, respectively, per kilogram of diet. A basal diet was formulated to contain FFSB as the sole source of AA, whereas the CM diet was formulated by supplementing the basal diet with CM. Diets contained titanium dioxide as an indigestible marker. Diets were fed in a 2-period crossover design to give 6 observations per diet. Each experimental period lasted 7 d, including a 5-d adaptation period and 2-d ileal digesta collection period. The SID of N and AA were calculated using published values for ileal endogenous N and AA losses from our laboratory. Enzyme supplementation increased (P < 0.01) AID values of DM (68.7 vs. 65.7%), GE (74.6 vs. 70.5%), and N (64.2 vs. 58.5%). Greater (P < 0.05) AID values were recorded for Leu, Met + Cys, Thr, Cys, Ser, and Tyr in the CM diet compared with the basal diet. Compared with the basal diet, the CM diet had greater SID values for N (73.7 vs. 68.6%; P < 0.01), Met + Cys (59.9 vs. 52.2%; P < 0.05), and Thr (66.3 vs. 61.2%; P < 0.05). The average SID for indispensable and total AA increased by 3.4% and 3.8% units, respectively, after enzyme supplementation. In conclusion, enzyme supplementation increased the nutritive value of extruded FFSB for finishing pigs.