PHYSIOLOGICAL RESPONSES OF RAINBOW TROUT (Oncorhynchus mykiss) FED DIETS INCLUDING Hermetia illucens PREPUPAE MEAL ENRICHED WITH SPIRULINA (Arthrospira platensis)

Over the last decades, the trend in the aquafeed formulation has been characterized by the reduction of fish meal (FM) and fish oil (FO) in favor of more sustainable alternatives. Insect meal has emerged as one of the most promising new aquafeed ingredients. More specifically, the black soldier fly (Hermetia illucens) represents an encouraging and increasingly studied insect species for aquafeed formulation due to its proper protein content and an essential amino acids profile similar to that of FM. The inclusion of full fat HM in fish diets is still limited by its unbalanced fatty acid profile (rich in saturated fatty acids and poor in polyunsaturated ones); however, it has been widely demonstrated that the HM fatty acid profile can be modified enriching the prepupae rearing substrate with potential sources of polyunsaturated fatty acids (PUFA). In this context, the addition of Spirulina (Arthrospira platensis) dried biomass to the insects’ growth substrate may represent an interesting way to improve the nutritional value of the prepupae and, thus, of HM. In light of this, the present study was aimed to: (i) improve the nutritional value of HM in terms of PUFA and bioactive molecules by adding A. platensis to the insect growth substrate (15% w/w), (ii) formulate two experimental diets characterized by two different dietary inclusion levels (3 and 20%) of “enriched” HM, (iii) investigate the physiological effects of the experimental diets in rainbow trout (Oncorhynchus mykiss) juveniles during a 42-days feeding trial.