Evaluation of microalgae concentrates as partial fishmeal replacements for hybrid striped bass Morone sp.

Processed microalgae concentrates recently have been considered potentially viable alternatives to partially replace fishmeal (FM) and fish oil in aquafeeds. Two feeding trials were conducted to evaluate incremental replacement of FM and soy protein concentrate (SPC) with different types of microalgae in the diet of hybrid striped bass. Microalgae evaluated in feeding trial 1 included dried products from monocultures of Phaeodactylum tricornutum and Nanochloropsis salina , as well as mixed cultures of those two species. Several preparations of Chlorella sp. lipid extracted by various means as well as bluegreen algae biomass (BGAB) also were evaluated. In feeding trial 2, the microalgae products supporting most efficient fish performance in feeding trial 1 were reassessed along with mixed cultures of Phaeodactylum tricornutum and Nanochloropsis salina as well as BGAB. Two additional mixed cultures of Nanochloropsis salina with Amphora sp. or Cylindrotheca sp. also were evaluated. Algae products were substituted to replace either 10, 15 or 20% of protein provided equally from menhaden FM and SPC in the Reference diet. All diets were isonitrogenous (40% crude protein) and isocaloric (3.3 kcal digestible energy g −1 ), and each were fed to triplicate groups of juvenile fish with average initial weights (+SEM) of 15.1 ± 0.6 g and 21.4 ± 1.3 g/fish in feeding trials 1 and 2, respectively for 7 weeks. Weight gain and feed efficiency ratio (FER) of hybrid striped bass were high (>330% of initial weight and 0.79) but significantly (P < 0.05) affected by diet in trial 1 with no mortality. Fish fed the Reference diet and the one containing BGAB had the greatest but similar weight gain. Substitution of the other algae meals significantly reduced weight gain by 8.2 to 14.7% compared to the Reference diet. Most diets containing algae meal yielded similar FER as the Reference diet except for those containing solvent-extracted Chlorella sp . (both 10% and 20% substitution), Phaeodactylum tricornutum (10%), and Phaeodactylum tricornutum  ×  Nanochloropsis salina (10% and 20%), in which FER was significantly reduced by 5.8 to 8.1%. Whole-body proximate composition and protein retention efficiency values revealed no significant differences among diets. In feeding trial 2, the various diets with algae products substituted at 10 or 15% of dietary protein did not significantly affect growth performance or whole-body composition of hybrid striped bass compared to the Reference diet. In conclusion, replacement of up to 15% crude protein in the Reference diet with BGAB, the Phaeodactylum tricornutum and Nanochloropsis salina mixture, as well as mixtures of Nanochloropsis salina with Amphora sp. or Cylindrothecatheca sp. was possible without affecting growth performance or body composition of hybrid striped bass. [ABSTRACT FROM AUTHOR]