2.4. Chemical Analysis of the Defatted BSF Larvae Meal And of the Experimental Diets

The chemical composition of the BSF larvae meal can be found in Table 2, whereas the chemical composition and the fatty acid (FA) profile of the experimental diets are provided in Table 3 and Table 4, respectively. Analyses of the defatted BSF larvae meal and the experimental diets were carried out in duplicate using Association of Official Analytical Communities (AOAC) (Official methods of analysis, 17th edition, Association of Official Analytical Chemists, Arlington, VA, United States) [21] methods to determine DM (method no. 934.01), CP (method no. 2001.11) and ash (method no. 967.05). Starch (amyloglucosidase-α-amylase, method no. 996.11) content was analyzed only in the experimental diets. Ether extract (EE) was determined after acid hydrolysis [22]. Gross energy (GE) was measured with an adiabatic bomb calorimeter [23].

Chemical composition (g/kg as is) and gross energy (MJ/kg) content of the defatted BSF (black soldier fly) larvae meal.

The methods to analyze the mineral content of larvae and experimental diets were: method 968.08 (Ca) and method 995.11 (P) of the AOAC [24]. Experimental diets were analyzed in triplicate for chitin content following the method by Zhang and Zhu [25] with the modifications described in Woods et al. [26].

Chemical composition and gross energy content of the experimental diets (g/kg as is).

BSF10 and BSF15 are diets corresponding to 10% and 15% BSF larvae meal inclusion levels, respectively.

Fatty acid profile (% of total fatty acid methyl esters (FAME)) of the experimental diets.

SFA = Saturated fatty acids; MUFA = Monounsaturated fatty acids; PUFA = Polyunsaturated fatty acids. BSF10 and BSF15 are diets corresponding to 10% and 15% BSF larvae meal inclusion levels, respectively.

The lipid extraction of the diets was performed by Accelerated Solvent Extraction (M-ASE) using petroleum ether as the solvent. The FA profile was determined as described by Cullere et al. [8]. Samples were trans-methylated using a methanolic solution of H₂SO₄ (4%), in order to determine fatty acid methyl esters (FAME). A biphasic separation was obtained by adding 0.5 mL of distilled water and 1.5 mL of N-heptane to each sample. FAME were quantified by gas chromatography (Shimadzu GC17A, 1, Nishinokyo-Kuwabara-cho, Nakagyo-ku, Kyoto 604-8511, Japan), equipped with an Omegawax® 250 column (30 m × 0.25 µm × 0.25 µm) (Supelco Inc., Bellefonte, PA, United States) and FID detector. Helium was used as the carrier gas at a constant flow of 0.8 mL/min. The injector and detector temperatures were both 260 °C. Peaks were identified based on commercially available FAME mixtures (37-Component FAME Mix, Supelco Inc., Bellefonte, PA, USA). The results are expressed as % of total detected FAME.