Digestibility of canola meals in barramundi (Asian seabass; Lates calcarifer)

The influence of two different oil processing methods and four different meal origins on the digestibility of canola meals when fed to barramundi (Lates calcarifer) was examined in this study. The apparent digestibility coefficients were determined using the diet-substitution method with faeces collected from fish using stripping techniques. The protein content of the solvent extracted (SE) canola meals (370-423 g/kg DM) was higher than that of the expeller extracted (EX) canola meal (348 g/kg DM), but the lipid content was lower than that of the expeller extracted canola meal. Among the SE canola meals, the protein digestibility of the canola meals from Numurkah and Newcastle was similar (84.1% and 86.6% respectively), but significantly higher than that of the canola meal from Footscray (74.5%). The protein digestibility was lowest (63.1%) for the EX canola meal. The energy digestibility of the canola meals (43.1-52.5%) was similar to that of the lupin (54.8%) except for the lower of SE canola from Footscray (32.4%). The SE canola meals provide 276-366 g/kg DM of protein while that of the EX is only 220 g/kg DM. The digestible energy content of the SE canola meal Footscray (6.5 MJ/kg) was lower than the other canola meals (8.7-10.6 MJ/kg DM). This study shows that there can be significant variability in the digestibility of canola meals subject to potential processing and sourcing variables.