Let Hermetia illucens free (from hunger and discomfort)! Welfare evaluation on larval stage.

Welfare evaluation is raising concerns about traditionally farmed animals, where 5 Freedom of Brambell’s report (5F) are applied. Despite no guidelines are present for insects yet, the International Platform of Insects for Food & Feed (IPIFF) recommends applying these principles. Insect welfare during their rearing can be indirectly evaluated considering performance parameters, as a suitability indicator of the conditions applied. Black soldier fly (Hermetia illucens L., BSF) is increasing in popularity as innovative feed and large-scale farming is expected to grow. This study determined the best dietary regime (T1), feeding rate (T2), rearing density (T3) for BSF larvae (L), integrating the 5F into the rearing process. Both small- (100 L in T1 and T2, 320 –960 L in T3) and large-scale (2000 L in T1 and T2, 3045 –9135 L in T3) experiments were set-up, with four replicates for each treatment. We evaluated performance parameters (growth rate, FCR, final larval weight, substrate reduction, survival rate) and BSF chemical composition. In T1, vegetarian (V), carnivorous (M), and omnivorous (O) diets was compared, with a control (C). Then, three feeding rates (T2: 50, 100, and 200 mg/day/larva) were evaluated, and compared rearing density values of 5, 10, and 15 larvae/cm2 (T3). The data were elaborated using one way ANOVA and Tukey HSD, or Kruskal-Wallis rank sum test and Dunn test. Even if the survival rate did not register significative differences, the omnivorous diet was the most efficient for BSF analyzing the growth parameters (growth rate +20% and +9% if compared to V and M diets, respectively). Optimized rearing can be achieved by applying a feeding rate of 100 mg/day/larvae (FCR -8% and -40% if compared with O50 and O200, respectively) and with density of 10 larvae/cm2 (final larval weight + 7% and growth rate +10% if compared with O15) ensuring both efficiency and the welfare of the insect. This holds a key role, especially from an industrial perspective, considering the future development of the sector.