Feed is the most important variable cost for Atlantic salmon culture, representing around 47% in major salmon-producing countries. Traditionally, salmon feed has relied on fishmeal (FM) and fish oil (FO) as major ingredients. However, there is pressure to replace these increasingly expensive and finite resources with cheaper alternatives. One problem encountered when switching from FM/FO-based feeds, however, has been reductions in feed intake and subsequent growth penalties. Accordingly, the impact of replacing FM and FO from salmon feed, using blends of animal (A; poultry meal, blood meal) and plant (V; soy and corn concentrate) proteins, combined with FO replacement using canola and algal oil, was evaluated over a 63-day timeframe. The influence of krill meal (+; 2.5%) as an alleged palatant was also investigated with diets being compared against a FM/FO-based control feed. Diets were randomly assigned to one of 20 flow-through tanks (n = 4 tanks per diet) initially stocked with 60 fish (148.4±12.9 g; 23.3±0.8 cm; K = 1.16±0.08), reduced to 45 at day 42.
At trial termination differences in group weights (P < 0.05) were observed between salmon fed the control feed and those fed diets without krill meal (Table 1). Fish fed feeds containing krill had similar weights to those fish fed the control feed. Length gain was greatest (P < 0.05) in fish fed the control feed with all other groups exhibiting identical length growth. This resulted in measurable differences (P < 0.05) in final condition factor K (Table 1). Proximate analyses of whole animals at study end revealed no differences between treatments (P > 0.05).