Influence of astaxanthin-enriched Haematococcus pluvialis microalgae on the growth efficacy, immune response, antioxidant capacity, proinflammatory cytokines, and tissue histomorphology of hybrid red tilapia

Astaxanthin, a natural ketone carotenoid, is among the environmentally friendly antioxidants and immunopotentiators. A 60-day feeding experiment was proceeded to assess the feasibility of astaxanthin-rich Haematococcus pluvialis as a growth promoter, antioxidant, and immunostimulant in the hybrid red tilapia (Oreochromis niloticus x O. mossambicus). Experimental diets containing grade amounts of Haematococcus pluvialis powder (0, 0.5, 1.0, and 1.5 g kg−1 feed) were formulated to be fed to red tilapia (Initial weight 27 ± 0.5 g) and designated as control, HP0.5, HP1, and HP1.5, respectively. The results indicated that the HP1 and HP1.5 promoted growth performance by decreasing FCR and increasing FBW, WG, WGR, and SGR confirmed by better intestinal morphology. Moreover, the HP1 and HP1.5 diets improved non-specific immunity via enhancing phagocytic activity, IgG and IgM contents, and nitric oxide, while decreasing MPO values compared to the control. Additionally, the H. pluvialis diets boosted antioxidant ability through elevating serum SOD and GSH activities, unlike the control group. The HP0.5, HP1, and HP1.5 diets also exerted hepatoprotective effects via histological sections as well as, suppressing liver enzymes (ALT, AST, ALP, and GGT) and reducing serum TG and cholesterol contents confirmed our data. Besides, a notable decrease in the serum levels of IFN-γ and IL-4 along with hepatic mRNA levels of TNF-α, IL-1β, IL-8, and caspase-3 with the increasing doses of H. pluvialis. These results proposed that a diet supplemented with 1 and 1.5 g kg−1 H. pluvialis is exhorted to augment the growth performance, hepatoprotection, antioxidant capacity, immunity, and anti-inflammatory response of red tilapia.