The Effects of Different Feed Substrates on Production Performance, Digestibility, and Chemical Composition of Zophobas morio Larvae

Zophobas morio is a potentially promising insect species for mass rearing; however, available data on its production performance and nutritional utilization remain limited. In this study, larvae were reared on nine different feed substrates, of which seven were retained for complete quantitative analysis. Production performance was evaluated at both tray and the individual larva weight to reflect conditions relevant to intensive production systems. Significant differences in production performance were observed among diets. Wheat bran resulted in the best performance, with a feed conversion ratio (FCR) of 2.55, whereas breadcrumbs resulted in the poorest performance (FCR 17.50). In two treatments (soybean grits and field pea), production performance could not be evaluated due to severe mortality and cannibalistic behavior or complete mortality, respectively, and these treatments were excluded from further analyses. Digestibility parameters could not be determined for the breadcrumbs treatment due to extremely low feed intake, which was insufficient to allow excreta (frass) collection required for the digestibility trial. Digestible energy ranged from 5.54 MJ/kg dry matter in canola meal to 10.40 MJ/kg dry matter in wheat grain. Diet composition had a pronounced effect on larval chemical composition. It is possible that carbohydrate-rich diets were associated with higher lipid accumulation (up to 60.44% in breadcrumbs), whereas protein-rich substrates were associated with increased larval protein content (up to 59.79% in sunflower meal), indicating clear dietary modulation of nutrient deposition. Overall, the results confirm that both production efficiency and larval composition in Zophobas morio are strongly dependent on diet formulation, highlighting the importance of optimized feeding strategies for its potential industrial production.