Effect of substituting fishmeal with black soldier fly and mealworm larvae meal on nutrient digestibility, body and mineral composition of Labeo rohita

Abstract

Background: Aquaculture is a cornerstone of global food security, offering an essential source of protein and nutrition to an ever-growing human population. Fishmeal is a high-protein feed ingredient typically made from wild fish, which increases the depletion of wild fish. Insects such as black soldier fly (BSF) (Hermetia illucens) and mealworm (MW) (Tenebrio molitor) larvae meal are promising alternative protein sources for aquafeeds. However, their effects on Labeo rohita remain underexplored. Aim: This study evaluated the impact of substituting fishmeal with BSF and MW larvae meal on the nutrient digestibility and body and mineral composition of L. rohita fingerlings. Methods: A 60-day feeding trial was conducted using varying levels (0%, 25%, 50%, 75%, and 100%) of BSF and MW diets. Growth performance was assessed using the following parameters: weight gain (WG), feed conversion ratio (FCR), and specific growth rate (SGR). Digestibility trials measured apparent digestibility coefficients for protein, lipid, and gross energy. The proximate and mineral compositions of the fish were also analyzed. Data were subjected to one-way analysis of variance and Tukey’s test at p < 0.05. Results: The 75% BSF and 50% MW diets exhibited the best growth performance, with significant improvements in WG, FCR, and SGR. Protein digestibility improved significantly, rising from 49.22% (control) to 75.15% in the BSF 75% group and from 50.91% (control) to 75.33% in the MW 50% group. BSF inclusion reduced body fat while increasing protein and ash content, whereas MW showed variable effects on lipid content. Both insect meals enhanced mineral retention, particularly calcium, sodium, phosphorus, and magnesium, with peak values observed in the 75% BSF and 50% MW diets. Conclusion: Replacing fishmeal with BSF and MW larvae meals improves the growth, nutrient digestibility, and mineral composition of L. rohita fingerlings. The BSF at 75% and MW at 50% inclusion levels yielded the best results. Therefore, insect meals are viable, sustainable alternatives to fishmeal in aquafeeds, although careful attention to inclusion levels and chitin content is required to optimize benefits.