Effects of Ramulus mori oligosaccharides on growth performance, serum physiological and biochemical parameters, and immunomodulation in largemouth bass ( Micropterus salmoides )

This study examined the effects of dietary Ramulus mori oligosaccharides (RMO) supplementation on the growth, antioxidant capacity, and immunomodulatory capacity in largemouth bass ( Micropterus salmoides ). Fingerlings weighing 26.82 +/- 0.31 g were randomly divided into three groups that were fed either the basal diet, supplementation with 0.5% RMO, or supplementation with 1.0% RMO. The feeding trial lasted 80 days, after which the fish were experimentally challenged with largemouth bass iridovirus (LMBV). The integration of RMO into the diet resulted in a slower rate of weight gain for largemouth bass, and it also led to an elevation in the feed coefficient. RMO supplementation significantly declined the serum levels of triglycerides, total cholesterol, and low -density lipoprotein, and lowered the activities of aspartate aminotransferase and alanine aminotransferase ( P < 0.05); increased the levels of serum total protein, albumin, and lysozyme ( P < 0.05); and increased the survival rate of fish infected with LMBV. Additionally, RMO supplementation boosted the activity of superoxide dismutase in both serum and liver, decreased the malondialdehyde content, and enhanced the total antioxidant capacity of serum and liver. The addition of RMO to the diet can also lower the phenomenon of liver vacuolization and upregulate the gene expression of liver sod and cat , reduce the expression of pro -inflammatory factors tnf- alpha and il-8 , and regulate the intestinal microbiota structure. In summary, RMO supplementation to a pelleted compound feed could improve the antioxidant capacity, increase disease resistance, affect the gut microbial composition, and protect the liver health of largemouth bass, showing the potential for development of this aquafeed additive.