Effects of the total fish meal replacement by soybean meal on growth parameters, serum biochemistry, and hepatic and intestinal histology of juvenile blunt snout bream (Megalobrama amblycephala).

Fish meal is the main protein source in fish diet, but due to its unsustainability, it has to be replaced with more sustainable protein sources, such as soybean meal (SBM), in fish feeds. As SBM often produces negative effects on fish growth and health, we conducted an eight-week trial of complete fish meal replacement with SBM in the diet of juvenile (48.2 ± 0.55 g) blunt snout bream (Megalobrama amblycephala), a herbivorous cyprinid fish native to the Yangtze basin (China). SBM-fed fish exhibited: a worsened growth performance; improved survival rate (P > 0.05); elevated serum triglycerides and total cholesterol but reduced low-density lipoprotein in plasma (P < 0.05); mild lipid droplet accumulation and swelling of the liver; elevated goblet cell counts and mild signs of enteritis in the intestines. With negligible effects on growth and mild effects on health, M. amblycephala appears to be comparatively tolerant of SBM, but total fish meal replacement is not recommended. Future studies should aim to identify the SBM tolerance threshold in long-term growth trials. [ABSTRACT FROM AUTHOR]