Canola, the world’s second most produced oilseed crop , has a great potential to be a major protein ingredient in aquafeeds due to its high nutritional values and good amino acid profile. Recent advances in aqueous processing have enabled the scalable production of environmentally friendly and nutrient-rich canola protein concentrate (CPC : 75.8% crude protein, 4.4% crude lipid). The objectives of this study were to 1) determine the nutrient digestibility of CPC; and 2) evaluate the effects dietary inclusion levels of CPC on Atlantic salmon growth performance, feed efficiency, nutrient utilization, gut histology and fillet color.
Two digestibility trials using settling column and stripping method were conducted for juvenile (57.3 ± 6.7 g) and post-s molt ( 227.7 ± 4.1 g) Atlantic salmon, respectively . The results demonstrated that the nutrients in CPC were well digested by Atlantic salmon , with mean apparent digestibility coefficients for crude protein, crude lipid and essential amino acids of 87.1, 93.3 and 81.5-97.0% for juvenile fish and 95.7, 90.9 and 93.9-98.0% for post-smolt fish , respectively . In a long-term growth study, eight experimental diets containing 0% (Diets A, E), 10% (Diets B, F), 15% (Diets C, G), and 20% (Diets D, H) CPC were formulated to mimic commercial salmon feeds in different geographies: Americas-style diets (A through D) contained processed animal protein (PAP) , whereas Europe -style diets (E through H) did not include PAP. Each diet was randomly allocated to triplicate groups of 33 fish (228.0 ± 4.9 g) per 750-L tank. F ish were hand-fed to apparent satiation for 168 days . The result showed that thermal-unit growth coefficient and feed intake were comparable between treatments (Table 1). 10% CPC inclusion was optimal for feed conversion ratio . There was no significant difference in final whole-body composition or nutrient retention among treatments . Increased dietary CPC inclusion from 0-20% resulted in positive associations with intestinal villi length and fillet redness value . In conclusion , CPC is a highly digestible nutrient-dense ingredient that can be safely included in Atlantic salmon diets up to at least 20%.