Partial dietary fishmeal replacement with soy products in grow‐out‐stage Burbot

Abstract Objective The primary objective of this study was to determine how soy products affect Burbot Lota lota maculosa growth and gastric evacuation. The secondary objective was to determine the digestibility of common soy products in Burbot. Methods A 130‐day feed study was conducted with subadult (grow‐out stage) Burbot to evaluate performance with 25% of the dietary fish meal replaced with soybean meal or soy protein concentrate compared with a control diet formulated to resemble a salmonid diet. Additionally, diets from the feed study, along with chironomid meal (a natural forage item), were used to determine Burbot gastric evacuation rates using fish naive to soy. These diets, containing over 12% soy, were applied to fish from the same cohort of Burbot used in the initial feed study. A digestibility assessment was conducted using diets with 30% of the fish meal replaced with soybean meal, soy protein concentrate, and a fermented soybean meal. Result No differences in growth performance were observed. The gastric evacuation assessment revealed that soy protein concentrate was evacuated at a significantly higher rate than chironomid meal; however, no other differences in gastric evacuation rates among diets were detectable. Apparent digestibility of protein was significantly higher in the soybean meal, soy protein concentrate, and fermented soybean meal treatments relative to the control diet. Apparent lipid digestibility was significantly lower in the soybean meal diet relative to the control diet; however, neither diet was significantly different from the soy protein concentrate or fermented soybean meal treatments. Conclusion Soy protein is highly digestible in grow‐out‐stage Burbot, these fish can be produced to market size on diets with ≥25% of the fish meal (relative to the experimental control diet) replaced with soybean meal or soy protein concentrate with no impact on growth performance relative to a salmonid diet formulation.