Dietary sulfated polysaccharides extracted from Caulerpa sp. and Padina sp. modulated physiological performance, antibacterial activity and ammonia challenge test in juvenile rainbow trout (Oncorhynchus mykiss)

Abstract

Nowadays, the use of seaweed derivatives in aquaculture has drawn attention for their potential as an immunostimulant and growth promotor. The sulfated polysaccharide extracted (SP_E ) from green (Caulerpa sp.; SPC) and brown (Padina sp.; SPP) seaweeds with two concentrations (0.05% and 0.1%); nominated in four groups: SPC_0.05 , SPC_0.1 , SPP_0.05 , SPP_0.1 and control group (free of SP_E ) were used for juvenile rainbow trout (Oncorhynchus mykiss) diet. Fish (N: 150; 8.5 ± 0.2 g) were selected aleatory distributed in 15 circular tanks (triplicate for the group) and fed test diets for 56 days. The outcomes revealed that the supplementation of SP_E up to 1 g kg^-1 failed to show significant differences in the organosomatic indices as compared to the control group. The most inferior protein value of dress-out fish composition was observed in the fish fed the control diet, which was statistically lower than the SCP_0.1 group (p < 0.05), while no significant difference was observed in other macronutrient composition among the treatments. Total monounsaturated fatty acid (MUFA) had lower trend in the carcass of fish fed SP_E supplemented diets, so that lowest MUFA were observed in SPC_0.05 group (p < 0.05; 25.22 ± 4.29%). The lowest value of docosahexaenoic acid was observed in the control diet compared to the SP_E -supplemented diets (p < 0.05). The serum alternative complement pathway levels in all treatments tend to promote compared to the control treatment. A similar trend was observed for lysozyme activity. According to the results, the superoxide dismutase (SOD) value were highest in SPC_0.05 and SPC_0.1 compared to the other treatments (p < 0.05), while a further elevation of the SP_E Padina sp. extracted level (SPP_0.1 ) leads to a decrease in SOD value. Thiobarbituric acid reactive substances of plasma was indicated not to influence by sulfated polysaccharide extracts in the refrigerated storage. The lowest serum stress indicators were observed in fish fed SPP_0.05 group postchallenge test. Taken together, our outcomes revealed that SP_E of two species of seaweeds bestows benefits in some of the immunity and antioxidant system. Also, notable elevations in HUFA were observed in juvenile rainbow trout fed supplemented with SP_E .

Keywords: Caulerpa sp; Padina sp; growth performance; immunostimulants; nutraceutical; seaweeds.