Does graded substitution of soy protein concentrate by an insect meal respond on growth and N-utilization in Nile tilapia (Oreochromis niloticus)?

Besides fishmeal, soybean protein is the most common protein source in aquafeed. However, the sustainability of soybean production is criticized. Due to the rapid development of aquaculture, the increasing demand for high value feed proteins has initiated research into alternative and more sustainable proteins for aquafeeds. In order to evaluate one promising alternative protein source, a growth study (56 days) was conducted with juvenile Nile tilapia (Oreochromis niloticus, 35 g on average) with a partial substitution of soybean protein by a partly defatted insect meal from black soldier fly larvae (Hermetia illucens). Growth performance, feed utilization and dietary protein quality parameters were evaluated based on analysed body protein deposition. A control feed (8% fish meal, 37% soy protein concentrate (SPC)) and three iso-nitrogenous and iso-energetic experimental feeds with 25, 50 or 100% replacement of SPC by partly defatted Hermetia meal (HM) were formulated. All feeds supplied essential amino acids as recommended for Nile tilapia. Growth response and protein utilization were examined in a semi-closed in-door water recirculation system. A comparative slaughter technique was applied to generate N deposition data for protein quality evaluation based on the standardized net protein utilization (NPUstd) according to the “Goettingen approach”. All feeds were very well accepted. Replacement of SPC by HM up to 50% improved feed protein quality and result in similar specific growth rate and feed conversion ratio, respectively. However, a higher inclusion rate of HM tended to impair growth, but not the observed protein quality. In conclusion, the replacement of SPC by partly defatted HM up to a level of 50% had no negative effect on growth performance and improved the dietary protein quality of tilapia feeds under study. Insect protein from Hermetia illucens could be a promising option to make aquafeed formulation more flexible and sustainable.