Fermented aquatic weed meal (FAWM) as a protein source in Asian Catfish Clarias batrachus diets: Impacts on growth, blood chemistry profile, liver and gut morphology and economic efficiency

Abstract

The global aquaculture industry is increasingly seeking sustainable alternatives to fishmeal (FM) due to its high price and shortfall in supply. In this context, fermented aquatic weed meal (FAWM) could emerge as a viable plant protein source for aquafeed. Four isoproteic diets [30 % crude protein (CP)] were formulated, incorporating 50 % total protein from FAWM comprising fermented Azolla diet (D1), Pistia diet (D2), and Eichhornia diet (D3). The control diet (D0) did not contain FAWM. At the end of the 90 days feeding trial, their growth performance, whole-body proximate composition, gut microbial load, haemato-biochemical indices, liver and gut health, and economic efficiency were determined. Fish fed with D0 had significantly (p < 0.05) improved growth performance and feed utilization compared to other treatment groups. Meanwhile, the fish supplemented with D1 diet exhibited significantly (p < 0.05) higher final weight (g), specific growth rate (%/day), weight gain (%), total biomass (g), and protein efficiency ratio among the FAWM dietary groups. The D1 group also demonstrated the significantly (p < 0.05) highest whole-body CP (64.27 ± 0.40 %) and lower crude lipid (8.24 ± 0.28 %) compared to other test diets. The total bacteria (TB) and lactic acid bacteria (LAB) in the fish gut were found to be significantly (p < 0.05) higher in D1 group. Furthermore, most of the hemato-biochemical indices of fish were significantly (p < 0.05) affected by FAWM inclusions, with few exceptions. The histological findings indicated that amongst the FAWM groups, D1 fish exhibited improved intestinal health. Nonetheless, the gut of the control fish demonstrated substantially (p < 0.05) lower villi width and crypt depth than other treatments. The D1 and D2 diet groups had significantly improved liver health. Moreover, FAWM inclusion enhanced economic efficiency by considerably reducing farm feed cost (US$/kg) and increasing return on investment (%). In summary, dietary inclusion of fermented Azolla pinnata (D1) protein at 50 % in aquafeed promoted feed utilization, growth, health, and farm economics of Asian catfish fingerlings compared to other FAWM diets.