Growth and Welfare Status of Giant Freshwater Prawn (Macrobrachium rosenbergii) Post-Larvae Reared in Aquaponic Systems and Fed Diets including Enriched Black Soldier Fly (Hermetia illucens) Prepupae Meal

Simple Summary The giant freshwater prawn culture is still challenged by dependence on diets containing high percentages of unsustainable and expensive marine-derived ingredients that are necessary to ensure the proper growth and welfare of this species. The present study proposed the replacement of fish meal and fish oil with black soldier fly full-fat prepupae meal enriched with spirulina in order to formulate two experimental diets intended for giant freshwater prawn, which were tested during a 60-day feeding trial in aquaponic systems. The present research represents an example of implementing more sustainable aquafeeds and farming techniques that promote both the valorization of circular economies and zero-waste concepts. Due to the limited application of insect meal in giant freshwater prawn (Macrobrachium rosenbergii) culture, the present study aimed to (i) produce spirulina-enriched full-fat black soldier fly (Hermetia illucens) prepupae meal (HM) and (ii) test, for the first time, two experimental diets characterized by 3% or 20% of fish meal and fish oil replacement with full-fat HM (HM3 and HM20, respectively) on M. rosenbergii post-larvae during a 60-day feeding trial conducted in aquaponic systems. The experimental diets did not negatively affect survival rates or growth. The use of spirulina-enriched HM resulted in a progressive increase in alpha-tocopherol and carotenoids in HM3 and HM20 diets that possibly played a crucial role in preserving prawn muscle-quality traits. The massive presence of lipid droplets in R cells in all the experimental groups reflected a proper nutrient provision and evidenced the necessity to store energy for molting. The increased number of B cells in the HM3 and HM20 groups could be related to the different compositions of the lipid fraction among the experimental diets instead of a nutrient absorption impairment caused by chitin. Finally, the expression of the immune response and stress markers confirmed that the experimental diets did not affect the welfare status of M. rosenbergii post-larvae.