Effects of replacing fishmeal with Spirulina platensis powder on the Zig-zag eel (Mastacembelus armatus): Growth performance, flesh quality, digestibility, and gut microbial composition

Abstract

Protein demand from aquaculture exacerbates environmental pressures. Zig-zag eel (Mastacembelus armatus, MA) is a new aquaculture species in southern China and has great potential for future promotion. In this study, we used Spirulina platensis powder (SPP) to replace 0–20 % of fishmeal in the feed, respectively. A 10-week aquaculture experiment was conducted on 600 MAs with five groups of F0 (0 %), F1 (5 %), F2 (10 %), F3 (15 %), and F4 (20 %) set up with equal nitrogen (approximately 50.00 % crude protein) and equal fat (about 5.50 % crude fat) feeds. The experimental results showed that replacing fishmeal with different proportions of SPP significantly reduced FCR (p < 0.05), increased WGR and SGR (p < 0.05), and reduced the feeding cost, with the best performance in F2. Polynomial analysis combining WGR and SGR showed that the optimum percentage of substitution was 10.93 % and 11.09 % in MA diets, respectively. The addition of SPP significantly reduced the levels of EPA and DHA content (p < 0.05), significantly increased the proportion of C14:0, C16:1, C20:5n3, and C22:6n3 (p < 0.05), and a high proportion of SPP addition significantly decreased saturated fatty acid content (p < 0.05). The length of intestinal villi and the secretion levels of Chymotrypsin and Pepsin were significantly increased (p < 0.05), and the secretion level of Lipase was significantly decreased (p < 0.05) in the experimental group. A low percentage of SPP increased microbial diversity in MA’s gut. Functional pathways related to metabolic functions were the most obvious broad groups with the most significant changes in relative abundance in the experimental group, and Plesiomonas and Aeromonas may be the key microorganisms involved in regulating the digestion and metabolism of SPP in the gut of MA.