Partial fishmeal replacement with Nannochloropsis oculata microalgae on growth performance, and fillet pigmentation in rainbow trout (Oncorhynchus mykiss)

Abstract

Introduction: Microalgae are a very diverse group of autotrophic microorganisms that
have found a wide range of applications in the aquaculture industry today. In this study, the
effect of partial replacing of fishmeal with dry powder of the microalgae Nannochloropsis
oculata in the diet of juvenile rainbow trout was tested.
Materials & Methods: Five isonitrogenous (~40%) experimental diets with different
replacement levels of Nanochloropsis with fishmeal including 0 (control), 3, 6, 9, and 12
g/kg were formulated. The experimental period was 8 weeks and the number of the
experimental fish was 450 (initial weight: 100.5±2.3 g).
Results: The indices of final weight, weight gain, and specific growth rate were increased
with increasing the replacement level of fishmeal up to 9 g/kg Nannochloropsis and then
they were significantly decreased in the treatment of 12 g/kg Nanochloropsis (P<0.05). The
feed conversion ratio index also showed a significant decrease in the treatments with
Nannochloropsis powder except for the treatment of 12 g/kg compared to the control group
(P<0.05). Regarding the quality of the fillet, the lowest amount of red spectrum of the fillet
was observed in the control group and the highest amount was measured in the treatment
with 12 g/kg microalgae compared to a full fish meal diet (P<0.05).
Conclusion: Replacing 9 g of fishmeal with Nannochloropsis microalgae powder can not
only improve the growth performance, but also improve the pigmentation of the fillet in
rainbow trout.