This co-fermented protein (CFP) shows promise in improving the growth performance, feed utilization, immune status, and hepatic and intestinal health of largemouth bass, claim the Chinese team.
Functional feeds, which include bioactive compounds like polysaccharides and protein complexes from mushrooms, are being actively explored for their potential to transform aquaculture into a more sustainable industry.
Various studies have demonstrated the effectiveness of functional soybean meal fermented by microbes like Aspergillus, Saccharomyces, Lactobacillus, and Bacillus in enhancing the growth and immunity of fish, note the researchers in a paper published in Fish and Shellfish Immunology.
Similarly, Pleurotus ostreatus byproduct fermented with Lactobacillus and yeast has been shown to improve body weight and immune response in Amur catfish, while fermented mushroom bran hydrolysate boosts the antioxidant capacity of carp.
The king oyster mushroom, already recognized for its health benefits, has been noted for its ability to modify gut microbiota and reduce inflammation in models of chronic colitis, and to alleviate oxidative damage in Caco-2 cells, they outline.
While mushroom root waste has been evaluated in livestock feed, research into its application in aquaculture has been limited—until now.
Methodology
The study evaluated largemouth bass, a highly profitable fish in China, where production reached 802,500 tons in 2022.
Fish were divided into five groups and fed diets containing 0%, 5%, 10%, 15%, and 20% CFP over seven weeks.
Key findings
Supplementation with CFP led to slight improvements in growth performance and feed utilization, report the authors.
Increased levels of immunoglobulin M and lysozyme activity, particularly in the 20% CFP group, indicated enhanced immunity. Significant increases in liver glutathione content were observed in the 10% and 15% CFP groups.
There was a slight improvement in total antioxidant capacity and superoxide dismutase activity, with a reduction in malondialdehyde content.
Upregulation of lipolysis-related genes and downregulation of lipid synthesis-related genes in the 20% CFP group suggested improved lipid metabolism.
Improved intestinal morphology was consistent with increased expression of structural integrity genes while pro-inflammatory cytokines were suppressed, and anti-inflammatory cytokines were activated in the treated groups.
Slight upregulation of antimicrobial peptides and immune effectors was noted.
Meanwhile, an increase in beneficial bacteria (Firmicutes) and a decrease in potential pathogenic bacteria (Fusobacterium and Proteobacteria) indicated a reorganization of the intestinal microbiota.
Conclusion
The study concludes that CFP derived from king oyster mushroom root waste and soybean meal significantly enhances the growth, immunity, and overall health of largemouth bass.
The researchers say the findings support the use of CFP as a sustainable, low-cost, and efficient functional protein source in aquaculture, paving the way for its broader application in the industry.
Source: Fish and Shellfish Immunology
Title: Pleurotus eryngii root waste and soybean meal co-fermented protein improved the growth, immunity, liver and intestinal health of largemouth bass (Micropterus salmoides)
