Introduction
With a favourable nutritional profile and consistent supply, canola meal (CM) stands out as a promising ingredient for salmonid feeds. While several studies have examined CM inclusion in feeds for rainbow trout and Chinook salmon, its application in Atlantic salmon remains underexplored. The objective of this study is to assess the nutritional value of solvent-extracted CM by evaluating its digestibility, effects on the growth and health of Atlantic salmon, and environmental impact when used in salmon feeds.
Materials and methods
A freshwater digestibility trial was conducted to determine the apparent digestibility coefficient (ADC) of the nutrients in CM . A reference diet was blended with CM at 90:10, 80:20 , 70:30 , and 60:40 ratios to create a series of test diets. Each diet was fed to triplicate groups of juvenile fish (49.0 ± 1.3 g), reared in 100-L tanks equipped with passive-feces collecting columns .
In a saltwater grow-out trial, four diets containing 0, 5, 10, or 15% CM were randomly assigned to three replicate 700-L tanks and hand-fed to post-smolt fish (245.6 ± 2.8 g) for 103 days. At the study’s conclusion, a pooled sample of five fish per tank was collected for whole-body composition analysis. Blood, liver, and distal intestine samples were obtained from an additional five fish per tank to assess plasma biochemistry, liver and intestinal histology .
A life cycle assessment (LCA) following ISO and PAS 2050 standards was performed to evaluate the environmental impacts of salmon production across four scenarios: cage systems without and with 10% CM in the feed, and recirculating aquaculture systems (RAS) without and with 10% CM .
Results
Results from the digestibility trial indicated that the ADC of nutrients was positively correlated with CM inclusion. At 40% CM, energy, protein, and essential amino acids ADC were 57.7%, 77.1%, and 83.0–93.9%, respectively. The feeding trial showed good growth performance across dietary treatments, with fish nearly tripling in body weight and maintaining a favorable feed conversion ratio (FCR) of approximately 1.0. F ish fed diets containing 5 and 10% CM had similar feed intake, growth, and FCR compared to the control, whereas 15% CM inclusion resulted in reduced growth and poorer FCR . Whole-body composition (i.e., protein, lipid, and ash) and plasma chemistry (i.e., immunoglobulin, lysozyme, glutathione peroxidase, catalase, and thyroid hormones) were similar across all diets (P>0.05). Intestinal and liver histology remained largely normal in all treatments. The LCA indicated that incorporating 10% CM into the diet, compared to a CM-free diet, led to 17% and 5% reduction in CO₂-equivalent emissions during salmon production in cage (1,683 vs. 1,390 kg CO₂-eq/MT salmon live weight) and RAS (5,763 vs. 5,460 kg CO₂-eq/MT salmon live weight) systems, respectively . Similar trends were observed for water use and land use, with impacts decreasing when CM was included. In conclusion, CM can be incorporated in salmon feed at levels up to 10% without compromising growth or health performance, while offering potential environmental benefits.