Effect of tail-end dehulling of canola meal on apparent and standardized ileal digestibility of amino acids when fed to growing pigs

The aim was to determine the effect of tail-end dehulling (dehulling after oil extraction) of canola meal (CM) on apparent (AID) and standardized (SID) ileal digestibility of amino acids (AA) when fed to growing pigs. Three ileal cannulated barrows (initial BW 58 ± 3.6 kg) were assigned to the 3 experimental diets in a replicated 3 × 3 Latin square design using 6 periods to provide 6 replicates per treatment. The use of sieve size 355 μm resulted in the production of 2 CM fractions, a dehulled fraction (DCM) and a coarse fraction (CCM). Diets consisted of a cornstarch-based diet with either regular canola meal (RCM), DCM, or CCM as the only source of protein. All diets contained titanium dioxide (0.3%) as an indigestible marker. In general, there was no effect (P >  0.10) of dehulling on the AID of most AA. However, AID of Phe was higher (P <  0.05) in RCM, compared to DCM and CCM. The AID of Thr and Trp was greater (P <  0.05) in RCM and DCM compared to CCM. However, the AID of Ile and Leu was higher (P < 0.05) in RCM and CCM compared to DCM. The SID of indispensable AA was not affected (P > 0.10) by dehulling. However, the SID of Phe was greater for RCM (P <  0.05) compared to DCM and CCM. Whereas, SID for Thr was higher in RCM and DCM compared to CCM. By removing the fibrous component, dehulling increased (P < 0.05) the standardized ileal digestible AA content of DCM compared to RCM by an average of 9%. The standardized ileal digestible His and Lys contents were similar between RCM and CCM, whereas, values for digestible Arg, Leu, Phe, and Thr contents were lower (P <  0.05) for CCM than CCM than for RCM and DCM. In conclusion, the results indicate that for most AA, the AID and SID in CM were not affected by dehulling. However, the content of ileal digestible AA can be increased with tail-end dehulling of CM.