The serial replacement of fish meal (anchovetta) by canola meal (CM) (100, 200, 300 g kg−1 as either solvent extracted
(SE) CMor expeller extracted (EX) CMwas undertaken to investigate the effects of increasing dietary CM
levels on feed intake, growth, protein and energy retention, plasma biochemistry and the expression of a suite of
hepatic genes in barramundi (Asian seabass; Lates calcarifer) over an eight week feeding trial. An additional diet
using lupin kernel meal (LM) to replace the fish meal was also included as a comparative reference. Eight iso-digestible
nitrogenous (423 ± 29 g kg−1) and iso-digestible energetic (14.6 ± 8 MJ kg−1 DM) diets were formulated.
Each diet was randomly allocated to triplicate groups of fish in seawater tanks (600 L), and each tank was
stockedwith 15 fish (53.4±7.0 g). Fishwere fed once daily (9:00–10:00) to apparent satiation, and uneaten feed
was collected to determine feed consumption. The results showed that the survival, feed intake, growth, FCR, energy
and protein retention of fish fed the diet containing SECMwere similar or even higher to those of fish fed the
fish meal reference diet (FM) and the LM diet. Fish fed with the diet containing 300 g kg−1 SE CM did not show
any changes in biochemistry and gene expression in a suite of detoxification genes. However, the diet with
300 g kg−1 EX CM depressed feed intake, growth performance and increased feed conversion ratio (FCR). Transcription
of genes involving in fatty acid synthesis and the TCA cycle were not changed by different diets. The
down regulation of gene expression in certain detoxification genes (Lc CYP1A1, Lc CYP3A, Lc CYP2N and Lc GST)
was observed in fish fed with the diet containing 300 g kg−1 EX CM compared to the FM control diet and
other experimental diets. In general, the SE CMcan be used up to 300 g kg−1 dietwithout negative performance
effects or signs of clinical plasma biochemistry. By contrast the maximum acceptable level of the EX CM for barramundi
was only 200 g kg−1. Higher inclusion level of the EX CM induced negative effects on growth performance,
feed utilisation, plasma biochemistry and gene expression in relation to detoxification.
Statement of relevance: Previous research has demonstrated that canola meal is a potential plant protein source
for fish meal replacement in diets for many fish species. The present work is designed to be the first to assess
both two types of Australian canola meal in regard to different processing methods (solvent extraction and
expeller extraction) in use for barramundi (Asian seabass) diets. The research not only assesses effects of canola
meal on growth performance and feed utilisation but also investigate effects of canolameal use on fish health status
using broad approach including plasma chemistry, histology and gene expression analysis. The present findings
provide practical information for barramundi's diet formulation using canola meal as an additional plant
ingredient. T