Carp growth, body composition, lipidomics, and flesh quality in response to replacing dietary fish meal with a complex protein source

Alternatives to fish meal (FM) in fish feed are urgently required in aquaculture. We therefore examined the effect of replacing FM with a complex protein source (CPS) comprising soybean meal, peanut meal, corn protein meal, feather meal, and yeast protein, on carp (Cyprinus carpio) growth, body composition, lipidomics, and flesh quality. Lipidomics analysis was conducted to reveal the impact of dietary changes on fish lipid composition and metabolism, which is closely related to flesh quality and nutritional value. Over an eight-week growth trial, fish meal was replaced with CPS at 0 % (FM only), 20 %, 40 %, 60 %, 80 %, or 100 %. Weight gain and other growth parameters did not differ significantly among the treatments. Lipid deposition (LD) was positively correlated, and protein deposition negatively correlated, with CPS levels. LD and fillet ether extract were significantly elevated at 100 % CPS, whereas superoxidase dismutase expression, claudin-1 expression, and lipase activity were significantly reduced. The n-3 PUFA level and n-3/n-6 PUFA ratio were significantly lower following CPS feeding, reducing flesh quality. These findings indicate that CPS successfully replaced 60–80 % of dietary FM in carp diets, while the 100 % replacement group provided insights into the comprehensive effects of total substitution. Future studies will further optimize formulations based on these results to resemble practical production more closely. CPS with nutrient supplementation may therefore present a viable and safe partial replacement for dietary FM.