Extrusion and enzyme addition enhanced ileal and total tract digestibility of pulse-based diets fed to growing pigs

Abstract Field pea and lentil and their protein concentrates are sources of dietary starch and protein that may replace soybean meal in growing pig diets. However, these ingredients also contain fiber and anti-nutritional factors that can reduce nutrient digestibility. To determine if extrusion processing and addition of an enzyme blend before or after extrusion would increase nutrient digestibility of pulse diets, two diets were formulated: a Low Protein diet with 24% crude protein (CP) including 35% field pea flour and 15% lentil flour, and a High Protein diet with 43% CP including 50% field pea protein concentrate and 20% lentil protein concentrate. The two diets were processed as follows: raw (R), extruded (E), extruded with enzyme added prior to (P) extrusion (E + P), or enzyme added after (A) extrusion (E + A). The enzyme blend contained cellulase, xylanase, protease, and phytase. Eight ileal-cannulated growing barrows (22–23 kg) were fed the eight diets in an 8 × 8 Latin square with 8 periods of 9 d each. Feces and ileal digesta were collected for 2 d each during the last 4 d of each period. A N-free diet was fed for one period at the end of the experiment to measure ileal endogenous amino acid losses. All diets included 0.4% titanium dioxide as an indigestible marker. Extrusion increased (P < 0.05) the apparent total tract digestibility (ATTD) of gross energy (GE) and CP, and the standardized ileal digestibility (SID) of essential amino acids (AA) compared with R for both Low and High Protein diets. The E + A diets further increased (P < 0.05) SID of essential AA and ATTD of ash compared with E for both Low and High Protein diets. The ATTD of GE and SID of CP and essential AA for E + P diets was reduced (P < 0.05) compared with E diets likely due to overheating during drying after the enzyme treatment. In conclusion, extrusion and enzyme addition after extrusion increased the nutritional quality of diets based on field pea and lentil and their protein concentrates fed to growing pigs.