Introduction
Aquatic protein production plays a vital role in meeting the growing global demand for protein, which ensures food and nutrition security (Melenchón et al., 2022). According to FAO, more than 70% of aquaculture production currently depends on fishmeal (FM)-based feeds. As aquaculture expands rapidly, finding sustainable alternatives to traditional FM is becoming increasingly crucial (Fabrikov et al., 2021). The findings of Broeckx et al., (2021) and in line with the UNSDGs, insect meal (IM) has been emerged as promising and environmentally friendly substitute for aquafeeds (Quang et al., 2022). Studies reported that the novelty foods in many developed countries are insect-based and are now gaining attraction, particularly in Asia. This shift is supported by initiatives such as the establishment of the Asian Food and Feed Insect Association (AFFIA) in Bangkok, which promotes IM production across the region. Thus, IM has emerged as a promising and environmentally sustainable replacement for FM in aquafeeds (Quang et al., 2022), offering a renewable source of protein for food, feed, and biomaterials. In this context, sustainable and circular solutions required to ensure the long-term viability of aquafeeds. This study aimed to explore the potential of Hermetia illucens - black soldier fly larvae (BSFL) as an alternative protein source in fish diets through an integrated biowaste management approach using onion waste. The findings of the study focused on three primary objectives: (i) evaluating the feasibility of utilizing BSFL to upcycle onion waste, (ii) assessing the nutritional suitability of BSFL meal in fish feed, and (iii) comparing the environmental implications of BSFL meal inclusion versus conventional fishmeal.
Materials and Methods
In this study, BSFL were reared on a substrate composed of onion waste and poultry manure under controlled laboratory conditions. The bioconversion efficiency, larval growth, and compost quality were assessed through proximate analysis. Five isonitrogenous diets replacing fishmeal with BSFL meal at 0%-D0, 25%-D1, 50%-D2, 75%-D3, and 100%-D4 levels were formulated and analyzed for nutritional and physical properties, including sinking velocity and water stability. A feeding trial was conducted using Cyprinus carpio fingerlings for 30 days, during which growth performance, feed utilization, and survival were monitored. Blood samples were analyzed for hematological and biochemical parameters, while liver and intestinal tissues were examined for digestive enzymes (amylase, protease, trypsin) and antioxidant enzymes (SOD, CAT, GSH, GPx) activities. Histological analysis of the distal intestine was performed to observe structural changes due to BSFL inclusion. All tests were conducted in three biological triplicates. Data presented as mean ± standard deviation (SD). Data were compared using one-way analysis of variance (ANOVA) and post-hoc comparison test (DMRT) using GraphPad Prism version 9 (GraphPad Software, Inc., San Diego, CA, USA).
Results
BSFL were reared on a mixed substrate of onion waste and poultry manure under controlled laboratory conditions. Larval growth, bioconversion efficiency, survival rates, and compost quality were systematically evaluated. The rearing process demonstrated high larval survival (above 90%) and significant substrate degradation, highlighting the effectiveness of BSFL in waste valorization. Nutrient profiling confirmed that BSFL had high crude protein (38.47%) and lipid content (48.79%), making it a viable feed ingredient. Subsequently, five isonitrogenous diets (D0 to D4) were formulated by progressively replacing fishmeal with BSFL meal at 0%, 25%, 50%, 75%, and 100% levels, respectively. These diets were fed to C. carpio fingerlings over a 30-day period. Growth performance indicators such as weight gain, specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency ratio (PER), and viscerosomatic index (VSI) were significantly improved in fish fed the 50% and 75% BSFL diets (D2 and D3), without compromising survival. Hematological and biochemical parameters remained within physiological ranges across all diets, suggesting that BSFL inclusion did not induce systemic stress. Digestive enzyme activities (amylase, protease, trypsin) and antioxidant enzyme levels (SOD, CAT, GSH, GPx) were also enhanced in BSFL-fed groups, particularly D2, indicating better digestion and oxidative stress management. Histopathological analysis of intestinal tissues revealed mild to moderate inflammation in higher inclusion groups (D3 and D4), warranting careful monitoring of gut health when formulating high-BSFL diets. Nevertheless, the overall findings validate the use of BSFL meal as a sustainable protein alternative, capable of replacing up to 50–75% of fishmeal without adverse effects on fish growth or health. Moreover, the frass (larval compost) generated post-bioremediation proved to be a nutrient-rich organic fertilizer, supporting soil sustainability.
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