The role of dietary Clostridium autoethanogenum protein in the growth, disease resistance, intestinal health and transcriptome response of Pacific white shrimp under different stocking densities

Abstract

With the rapid development of intensive farming mode and the high price of fishmeal (FM), finding alternatives to FM and exploring the application under different stocking densities has become a focus of current research in aquaculture. In this research, the ability of Pacific white shrimp (Litopenaeus vannamei) to utilize Clostridium autoethanogenum protein (CAP) at different stocking densities was investigated from the aspects of growth, disease resistance, intestinal health and transcriptome response. A 3 × 2 factorial design stocking experiment was conducted, using L. vannamei fed diets of two protein sources (FM and CAP) at three stocking densities with 100 per m3 (low, LSD), 200 per m3 (medium, MSD) and 300 per m3 (high, HSD) for 8 weeks. At the end of the feeding trail, the growth performance and the resistance to Vibrio parahaemolyticus of shrimp decreased with the increase of stocking density, and dietary CAP could promote the effects at the same stocking density when compared with the FM group, with more notable enhancement effect at high stocking density was observed. There was a significant interaction between stocking density and protein source on the activities of alkaline phosphatase (AKP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), catalase (CAT), superoxide dismutase (SOD), lysozyme (LYS), amylase and lipase, most of which were significantly different between CAP and FM groups only at high stocking density. Analysis of 16S rDNA sequencing showed that dietary CAP increased the alpha diversity of intestinal microbiota, inhibited the colonization of pathogenic bacteria and enhanced the abundance of beneficial bacteria. Transcriptomics results showed that DEGs in the FM vs CAP group at the same stocking densities were mainly enriched in immune and metabolism-related pathways including Toll and Imd, PI3K-Akt, and JAK/STAT signaling pathway. Pearson correlation analysis revealed significant correlation between the top ten intestinal bacteria at the genus level and markedly enriched DEGs, also more were detected under high density situations. In conclusion, dietary CAP could not only promote the growth of shrimp, but also improves the immunity and metabolism, and maintains the intestinal health of shrimp when compared with dietary FM, along with more pronounced improvement effect at high-density stocking. The results implied that CAP had a great potential as a novel protein source in shrimp intensive aquaculture.