HERMETIA ILLUCENS MEAL AS A PARTIAL SUBSTITUTE FOR FISHMEAL IN THE DIET FOR SPARUS AURATA L. FARMED OFFSHORE: CHEMICAL AND MICROBIOLOGICAL INVESTIGATIONS ON FEED QUALITY. PART II.

Despite the nutritional value of H. illucens meal (HIM), its successful inclusion level in aquafeeds depends on fish species, characteristics of insect derivatives and growth substrate. Aim of this study was to characterize the chemical and microbiological composition of two diets, one (HIM0) with fish meal as exclusive protein source of animal origin, and the other (HIM35) containing HIM as a partial replacement (35%) for fish meal, formulated to satisfy the nutritional needs of Sparus aurata L. farmed offshore. Diets were isonitrogenous (42 g/100g, as fed) and isolipidic (19 g/100g, as fed). Fatty acids and amino acids were analyzed by gas chromatography, minerals via ICP-MS, aflatoxins by liquid chromatography, microbial flora following the ISO methods. Data were evaluated using a one-factor ANOVA of XLSTAT statistical package. HIM35 diet showed significantly higher percentage of SFA (22.45% vs. 19.07%), mainly due to the higher lauric acid content (2.81% vs. 0.06%), and lower percentages of n3-PUFA (13.14% vs. 14.15%), mainly due to the lower EPA+DHA content (7.68% vs. 8.41%). Significantly higher atherogenic and thrombogenic indices and lower peroxidation index and hypocholesterolemic:hypercholesterolaemic fatty acid ratio were observed in the HIM35 diet. HIM35 diet showed significantly higher values of valine (2.33% vs. 2.05%) and isoleucine (2.32% vs. 2.13%) and lower values for phenylalanine (2.87% vs. 3.29%), lysine (4.34% vs. 4.65%) and arginine (2.29% vs. 2.81%). The indispensable/dispensable amino acid ratio was significantly lower in the HIM35 diet (1.19 vs. 1.27). In both diets, arsenic, cadmium, mercury and lead were below the permitted toxic heavy metal content limits in feed (Directive 2002/32/EC) and aflatoxin B1 levels were below the permitted level on undesirable substances in animal feed (Directive 2002/32/EC). In both diets similar aerobic mesophilic bacteria counts were observed (3.5 Log CFU/g); Enterobacteriaceae, coliforms, clostridia, molds, Salmonella spp. and Listeria monocytogenes were not detected. Although HIM has influenced the chemical composition of feeds, it has proven to be a safe ingredient to achieve safe feed.