Potential beneficial effects of dietary replacement of fish meal with Black soldier fly (Hermetia illucens) larvae meal on growth, general physiology, and microanatomy of Nile tilapia (Oreochromis niloticus).

The ongoing growth of aquaculture and reduced fish meal supply leads fish nutritionists to seek alternative protein sources for sustainable aquaculture development. Black soldier fly larvae meal (BSFLM) is gaining importance due to its high protein content with a well-balanced amino acid profile. A 90-day triplicate feeding trial was executed to evaluate the impact of partial and complete replacement of fish meal (FM) with BSFLM in the diet of Oreochromis niloticus. Fingerlings (average body weight:1.23 g) were divided into five groups and reared on 32% CP experimental diets with replacement of FM with BSFLM at 0%, 25%, 50%, 75%, and 100%, respectively. Results indicated the significant effect of FM replacement with BSFLM on growth performance, nutrient digestibility, FCR, activity of digestive enzymes, biochemical indices, intestinal and liver morphology, and expression of growth hormone, myoblast determination protein 1, and Myostatin genes. The 50% followed by 75% replacement of FM demonstrated the most significant positive effect on these parameters, while 100% replacement showed the most notable negative impact. In addition, some parameters like proximate composition, the status of antioxidant enzymes, and expression of stress-related genes heat shock proteins (HSP-70 and HSP-90) did not show any statistical difference among groups except a D100 (100% FM replacement) group, which showed higher activity of CAT, SOD, and mRNA levels of HSPs. Based on current findings, replacing 50% of FM with BSFLM in the diet of O. niloticus is recommended to reduce production costs.