UTILIZATION OF OPEN-FORMULA DIETS FED TO FLORIDA POMPANO Trachinotus carolinus TO EVALUATE MICROALGAE OIL SUBSTITUTION FOR FISH OIL

There is interest in reducing the use of rendered fish oil (FO) in fish feeds. There  are an increasingly diverse array of alternative s; however,  suitability requires  accurate information on the nutritive value of  a  prospective alternative. There is  increasing interest in utilizing microalgal oils as a partial replacement/supplement to FO, particularly the  heterotrophic microalgae Schizcochytrium

The specific objectives of the study were: 1) to evaluate performance of four experimental fishmeal (FM) free diets,  each  with different supplementary oil sources relative to an open-formula  FM  based diet; and 2) evaluate performance of the four different oil supplements relative to each other.

Five  experimental  diets were formulated as iso-nitrogenous and iso-lipidic. The control diet (FM) contained FM and FO and  other  ingredients common in commercial feeds. The remaining four diets were FM free and varied only in lipid containing either fish oil (FO), algal oil (AO), soy oil (SO), or  an algal/soy oil (50/50) blend (A/S). The AO (Veramaris^® ) is a liquid product extracted from whole cell, heterotrophic microalgae Schizochytrium sp.  The SO diet served as a negative control.  The A/S diet was evaluated to determine if the very high levels of DHA found in AO are necessary. Oil supplements were incorporated at 10.8% of the dry diet.

The experiment was a completely randomized design with four replicate tanks. Tanks were stocked with 20 pompano (  = 4.1g) and  fed four times/day ad libitum . The experiment lasted 85 days. D ata were analyzed as a one-way ANOVA. The FM control was tested against the other four experimental diets using Dunnett's t-test. The diets differing only in oil sources were tested against each other using orthogonal contrasts. Significant differences were declared at P<0.05.

Of the AO, SO, and A/S diets, only the SO diet was significantly different than the FM control in almost all parameters evaluated. The protein productive value  (PPV)  of AO was not different than the  FM  control, whereas  FO, SO, and A/S were.  The results of the contrasts indicate performance of the

SO fed fish were lower than the other oil sources (Table 1). The data suggest within the similar diets varying only between supplemental oil sources that Veramaris^® algal oil is a suitable alternative to FO, and that diluting it to a 50/50 blend with SO resulted in no decreases in performance other than in PPV.