The Effects of Porphyra yezoensis Polysaccharides on Intestinal Health of Spotted Sea Bass, Lateolabrax maculatus

Abstract

Porphyra yezoensis polysaccharides (PPs) have biological activities such as promoting digestion, functioning as antioxidants, and improving intestinal health. The aim of this study was to investigate the effects of PPs on the intestinal health of spotted sea bass (Lateolabrax maculatus). A total of 360 spotted sea bass (10.53 ± 0.02 g) were randomly divided into six groups. Fish in each group were fed with varying PP concentrations (0, 3, 6, 9, 12, 15 g/kg) for 52 days. The results showed that 12 g/kg PPs significantly increased the body weight gain, specific growth rate, and condition factor, while there was no significant change in the feed conversion ratio. A supplementation dosage of 9 g/kg PPs significantly increased intestinal amylase activity, and 12 g/kg PPs supplementation significantly increased intestinal trypsin activity. In addition, compared with the control group, there was no difference in lipase in the experimental groups. When fed 9 g/kg, the intestinal glutathione content was significantly increased, and the malondialdehyde content was significantly decreased; the effect of PPs on the catalase activity was not significant. PPs improved intestinal morphology, specifically by improving the intestinal villus morphology and increasing the intestinal lining surface area. Compared with the control group, PPs increased the abundance of Firmicutes and Bacteroides. At the genus level, Cyanobacteria, Muribaculaceae, and Lachnospiraceae were the main flora in the intestinal tract of spotted sea bass. In addition, PPs increased ACE and Chao1 indices of the intestinal microorganisms, while the Simpson index and Shannon index did not change significantly, indicating that intestinal microbial composition and abundance had increased to a certain extent. The results indicated that different levels of PPs in feed can improve the intestinal physiological and biochemical indexes, intestinal morphology, and microbial composition, and thus improve the intestinal health of spotted sea bass.