Effects of the total fish meal replacement by plant meal on growth performance, nutrient utilization and intestinal microbiota of backcross F2 derived from blunt snout bream (Megalobrama amblycephala, 9) x topmouth culter (Culter alburnus, )

A two-month growth experiment was conducted to investigate the effect of the total fish meal replacement by plant meal on growth performance, nutrient utilization and intestinal microbiota in an improved bream (BBTB) obtained by multistep breeding technologies. Three diets were formulated to replace 0 (FM), 65% (MM) and 100% (PM) of dietary fish meal protein by plant meal (soybean meal and rapeseed meal), respectively. The results showed that the fish meal and plant meal diets could significantly increase the weight gain rate (WGR), specific growth rate (SGR) and feed efficiency ratio (FER) of BBTB compared to their mixed diet. Besides, BBTB fed with PM could significantly decrease the liver lipid contents, but the fish fed with FM showed the more complete microscopic structure in the intestine. Nevertheless, there was no significant difference between FM and PM groups in trypsin activity. In additional, the fish fed with PM showed the higher expression levels in ACC alpha, PPAR alpha, PPAR gamma, CPT1a, PepT1 and APN genes, which might affect its nutrient utilization. The results in intestinal microbiota showed that BBTB possessed the herbivorous fish characteristics of intestinal microbiota. These results indicated that BBTB possessed herbivorous characteristics. It is of great significance for the sustainable development of aquaculture.