Development of a practical soy-based diet for California yellowtail, Seriola lalandi

Abstract

Two feeding trials were conducted to initiate the development of a practical soy-based diet for California yellowtail (YT), Seriola lalandi. The first trial evaluated fish meal (FM), FM + solvent-extracted soybean meal (SBM) or FM + soy protein concentrate (SPC)-based diets and a commercial reference diet (Skretting Marine Grower). Final weights (31.8–67.6 g), per cent gain (492.8–1059.9%) and feed conversion ratio (1.11–1.59) all followed a similar response in that fish offered the commercial diet performed significantly better than fish maintained on the other diets. The second trial was designed to evaluate the replacement of FM with increasing levels of soy protein. The basal diet contained 400 g kg−1 FM and 240 g kg−1 SBM. The FM was then reduced to 300 g kg−1, 200 g kg−1 and 150 g kg−1 of the diet using SPC as the replacement protein. Final weight (41.2–64.1 g) and per cent gain (110.5–226.5%) followed similar trends with decreases in performance as the FM level was reduced. No gross signs of enteritis were noted, indicating that reduced performance was likely due to nutrient deficiencies or palatability problems rather than an allergic response. Results demonstrate that there is potential to develop reduced FM diets for this species using soy protein.