Effects of Seaweed Polysaccharide on the Growth and Physiological Health of Largemouth Bass, Micropterus salmoides

A seven-week trial was designed to evaluate the effects of dietary seaweed polysaccharide (SP) supplementation on the growth performance and physiological health of largemouth bass. The results reveal that the 0.05SP group showed the best growth performance. The mRNA expression levels of tor, 4ebp1, and igf1 genes were remarkably down-regulated in the 0.15SP and 0.2SP groups compared to the control group. The CAT activities were significantly increased in the 0.05SP and 0.1SP groups, and the GSH-Px activity was increased in the 0.15SP group. The expression of the immune response-related gene nfκb was significantly down-regulated in the 0.1SP group, and those of tnfα and il-8 were at the maximum in the control group. Moreover, the expression of il-10 in the 0.15SP and 0.2SP groups was significantly down-regulated. Furthermore, endoplasmic reticulum stress (ERS)-related expression of atf6 was the highest in the control group. Furthermore, the chopα and bax expression levels in the 0.15SP and 0.2SP groups were significantly down-regulated compared with other groups. In addition, the highest expression level of bcl-xl was observed in the 0.15SP group. Finally, the quadratic regression analysis of antioxidant, immune, and ERS core parameters (CAT, nf-κb, and bcl-xl) determined 0.06–0.11% to be the optimal SP supplemental level in largemouth bass diets.