Addition of olive pomace to feeding substrate affects growth performance and nutritional value of mealworm (Tenebrio molitor L.) larvae

The well-recognized efficiency of Tenebrio molitor larvae to convert low quality organic matter into a nutritionally valuable biomass was exploited to manage solid wastes coming from the olive oil industry, which represent a severe environmental challenge in the Mediterranean area. Three organic pomace-enriched substrates (mixtures middlings/pomace 3:1, 1:1, and 1:3) were assessed, together with 100% organic wheat flour and 100% organic middlings as control feeds. A feeding substrate made up of 25% olive pomace and 75% wheat middlings appeared to be the best compromise between growth performance (larval and pupal weights, survival rate, development time) and nutritional properties of mealworm larvae. In fact, larvae fed the 3:1 feed showed the highest dry matter (DM) yield (38.05%), protein content (47.58% DM), and essential/non-essential amino acids ratio (1.16). Fat content (32.14% DM) and fatty acid composition were not significantly different than those of larvae fed more pomace-enriched feeds.