Nutrient Digestibility of Extruded Canola Meal in Grower Pigs

Canola meal (CM) contains less CP and more fiber and anti-nutritional factors (ANF) such as glucosinolates than soybean meal, and has consequently a lower AA digestibility. Fiber and ANF may reduce DE value of CM and may interfere with digestion of other ingredient nutrients. Therefore, processing strategies that increase nutrient digestibility, and thereby increase the feeding value of CM, warrant study. This study assessed effects of extrusion of Brassica napus CM on apparent ileal digestibility (AID) of AA and GE, and apparent total tract digestibility (ATTD) of GE and DE value. In a double 4×4 Latin square, 8 ileal-cannulated barrows (68.1±9.4 kg initial BW) were fed corn starch-based diets containing 50% CM, or extruded CM prepared using a single-screw extruder (X-115; Wenger, Sabetha, KS). Extruder intensity was low, medium or high according to extruder speed (250, 350, 450 rpm) and related mechanical energy. Standardized ileal digestibility (SID) of AA for diets was calculated by correcting AID for endogenous losses measured feeding an N-free diet. Data were analyzed using MIXED model of SAS with diet as fixed effect, and pig and period as random effects. Pig was the experimental unit. The CM samples contained 42.1-43.2% CP, 26.0-33.9% NDF, and 19.7-23.4% ADF. On DM basis, CM, extruded CM at low, medium or high extruder intensity contained 8.87, 7.84, 7.30 and 7.86 µmol/g total glucosinolates. The AID, ATTD, and hindgut fermentation (ATTD-AID) for DM, CP and GE was not affected (P>0.05) by extrusion intensity. The SID of Met for raw CM (88.18%) was lower (P<0.001) than that for extruded CM (91.80-92.69%), and SID of Trp for raw CM (86.41%) was lower (P<0.050) than that for CM with low (89.43%) or high-speed extrusion intensity (90.29%). Similarly, extrusion increased the SID of Arg, His, Ile, Leu, Phe, and Val of CM. In conclusion, extrusion increased SID of most indispensable AA of solvent-extracted CM by 3.09-5.32%, indicating that extruded CM contributed more dietary AA to the pig than CM. However, increased extruder speed, hence increased mechanical energy, did not affect SID of AA of CM in growing pigs. Finally, extrusion slightly reduced total glucosinolates content in CM.