Growth and hematological and immunological responses of Arapaima gigas fed diets supplemented with immunostimulant based on Saccharomyces cerevisiae and subjected to handling stress

Abstract Saccharomyces cerevisiae is rich in bioactive ingredients and nutrients such as essential amino acids, peptides, cell wall carbohydrates, nucleotides and B vitamins. Diets with this immunostimulant product may offer improves in growth performance and immune of farmed fish. This study evaluated the effects of a commercial immunostimulant based on S. cerevisiae on growth performance, hematology and immunity of Arapaima gigas subjected to handling stress after 30 days of supplementation (0, 4, 6 and 8 g kg−1). Diet with 6 and 8 g kg−1 of immunostimulant increased final biomass, final length, body weight gain, daily weight gain, daily feed intake, specific growth and decreased the cholesterol levels. After handling stress, supplemented fish with 4, 6 and 8 g kg−1 of immunostimulant had increase in glucose levels and decrease in globulin levels, while supplemented fish with 4 and 6 g kg−1 had decrease in cholesterol, and supplemented fish with 4 and 8 g kg−1 in globulin levels. Protein levels decreased in supplemented fish with 4 g kg−1, while hematocrit decreased in all treatments and lymphocytes number and burst respiratory of leukocytes decreased in supplemented fish with 8 g kg−1 and submitted to handling stress. For A. gigas, since 6 to 8 g kg−1 of immunostimulant has not negative impacts on the hematological and biochemical parameters, thus such concentrations may be used as a growth promoter in A. gigas.