Appraisal of leaf protein concentrate derived from sugar beet and carrot as a novel fish meal substitute for juvenile Nile tilapia (Oreochromis niloticus)

Carrot and sugar beet are among the crops that produce a significant amount of leafy biomass, which raises environmental concerns. Therefore, this study aimed to evaluate the impact of replacing fish meal (FM) with sugar beet and carrot leaf protein concentrate (LPC) on performance, body composition, and blood metabolites in Nile tilapia (Oreochromis niloticus) for 84 days. Randomly, 225 tilapia fish (5.03 +/- 0.006 g) were distributed into five groups having different replacement proportions of FM protein with LPC: 0 % (control diet), 25 %, 50 %, 75 % or 100 % (LPC-0, LPC-25, LPC-50, LPC-75, and LPC-100, respectively). The study found that increasing LPC replacement levels up to 75 % did not significantly alter growth performance parameters (P > 0.05). In contrast, substituting with 100 % LPC resulted in a notable reduction in the relative growth rate when compared to the control group (P = 0.043). Furthermore, fish fed the LPC-100 diet exhibited impaired trends in terms of final body weight (P = 0.064), daily weight gain (P = 0.055), and feed conversion ratio (FCR; P = 0.054). The best FCR value was observed in fish fed the LPC-75 diet. There were no significant differences in serum lipid and protein profile, liver and kidney function indicators, and hematological parameters among all groups (P > 0.05). The total replacement of FM with LPC adversely impacted the crude protein (P = 0.007) and ash (P = 0.002) contents of O. niloticus bodies. Replacing FM with 75 % LPC resulted in the highest relative margin (P = 0.008) and final margin (P = 0.005) compared to the other groups. Overall, the results indicate that 75 % of FM can be effectively replaced with LPC in O. niloticus diets, with no adverse effects observed on growth and health. Additionally, from an economic point of view, the use of LPC at 75 % instead of FM protein had more efficiency in producing healthy and low-cost aquafeed.