Utilization of squid (Loligo vulgaris) co-products meal as fishmeal replacer in the diet of European seabass (Dicentrarchus labrax) farmed in Morocco

In this study, we evaluated the effect of replacing fishmeal (FM) in the diet of seabass with squid co-product meal (SCM) on the zootechnical performance, quality of the farmed seabass, and the environmental and economic sustainability of the experimental diets. Four experimental diets were formulated to be iso -proteinic (50 %), iso -lipidic (19 %), and iso -energetic (22 MJ/kg), with FM replaced by SCM at rates of 0 %, 50 %, 75 %, and 100 % (SM0, SM50, SM75, and SM100, respectively). These were manufactured and tested on 240 fish with an initial average weight of 82.61 ± 1.40 g. The growth performance of sea bass significantly improved with the replacement of FM with SCM. Fish fed the SM50 diet exhibited the highest weight gain (96.24 g compared to 63.85 g for the SM0 control diet), and the best specific growth rate (SGR) was observed in fish fed the SM50 diet, followed by those fed the SM75 diet. Conversely, fish fed the SM100 diet demonstrated similar weight gain (WG) and SGR as those fed the SM0 control diet. The best feed conversion rate (FCR) was recorded in fish fed the SM50 diet (1.42 compared to 1.76 for those fed the SM0 control diet). The findings revealed that replacing 50 % FM with SCM considerably enhanced the zootechnical performance while maintaining the analytical composition of the whole fish and intestinal microflora. Furthermore, replacing 50 % of FM in the experimental diets significantly enhanced the environmental and economic sustainability indices. The environmental sustainability index was considerably reduced with the use of SCM (fish-in fish-out (FIFO) ≤ 1) and had a favorable economic impact, reducing feed costs by 24.3 % ($0.84/kg compared to $1.11/kg for the SM0 control diet), and saving 38.9 % on the cost of converting feed into fish biomass ($1.19/kg compared to $1.95/kg in the SM0 control diet).