Digestible energy contents and apparent ileal amino acid digestibilities in regular or partial mechanically dehulled canola meal samples fed to growing pigs

A study was carried out to determine the influence of partial mechanical tail-end dehulling on apparent ileal amino acid (AA) digestibilities and digestible energy content in canola meal (CM) samples for growing pigs. Twenty Landrace x Yorkshire barrows, with an initial body weight of 35 kg, were fitted with a simple T-cannula at the distal ileum. Digestibilities were determined in 12 experimental diets with observations from five pigs per diet. Five batches of regular CM were obtained from five different crushing plants in Western Canada. A fraction of these batches was partially dehulled. The regular and partially dehulled CM samples were included at 20% in a barley-based diet. One pooled high-fiber CM sample and a straight barley diet were evaluated as well. Partial dehulling increased (P < 0.05) the digestible energy (DE) content from 12.2 to 13.3 MJ kg DM-1, respectively, and the level of crude protein (CP) from 40.6 to 43.8% in regular and partially dehulled CM samples, respectively. The digestibility of threonine was increased (P < 0.05) by partial dehulling, from 72.1 to 75.5%; the digestibilities of CP, lysine, methionine and cysteine were not affected (P > 0.05). Only the digestibilities of methionine and threonine were lower (P < 0.05) in the high-fiber CM sample than in the regular and partially dehulled samples. Digestible energy content, which ranged from 10.8 to 14.2 MJ kg DM-1, differed (P < 0.05) between crushing plants for both regular and partially dehulled CM samples. The digestibility of lysine did not differ (P > 0.05) between processing plants for the regular CM samples. The digestibility of lysine did not differ (P > 0.05) between processing plants for the regular CM samples. In contrast, there were differences (P < 0.05) in lysine digestibility, ranging from 74.8 to 83.8%, and methionine, ranging from 80.4 to 86.9%, between crushing plants for partially dehulled samples. There were low negative relationships between apparent ileal AA digestibilities and NDF, ADF and CF levels (r < 0.39) and between DE content and NDF, ADF and CF levels (r < 0.36) in the CM samples. In conclusion, the reduction in fiber content by mechanical tail-end dehulling increased the supply of DE and the level of CP, but did not influence apparent ileal CP or AA digestibilities, except for threonine which was slightly increased.