Optimizing Larval Density for Efficient Bioconversion of Swine Manure Using Black Soldier Fly ( Hermetia illucens ; Diptera: Stratiomyidae) Larvae

ABSTRACT Swine manure management poses significant environmental challenges, and black soldier fly, Hermetia illucens L. (Diptera: Stratiomyidae) larvae, offer a sustainable alternative by converting manure into insect biomass while reducing waste volume. This study evaluated the optimum larval density on BSF performance during swine manure conversion under controlled laboratory conditions. Larvae were reared on 100 g of swine manure at seven densities (0, 20, 40, 60, 80, 100, 200 per container) for 14 days at 30°C ± 1°C, with a zero‐larva control maintained to assess natural manure degradation and moisture loss. Increasing larval density significantly increased total larval biomass and waste reduction index (WRI) but reduced individual larval weight by 56% from 0.60 to 6.03 larvae/cm 2 . Survival remained consistently high across all treatments (> 90%). However, prepupation rates decreased as density increased, suggesting that crowding delayed larval transition to the prepupal stage. In contrast, collective metabolic efficiency increased with larval density; the efficiency of conversion of digested feed (ECD) was highest at 6.03 larvae/cm 2 , while the feed conversion ratio (FCR) reached its optimum at 3.02 larvae/cm 2 . High larval activity also facilitated residue drying, resulting in a substantial reduction in final moisture content to 51%. This study reveals a clear trade‐off between individual larval growth and bioconversion efficiency. While high larval densities maximize waste reduction parameters, intermediate densities at 1.81–3.02 larvae/cm 2 provide a favourable balance between maintaining individual larval growth and achieving effective manure reduction.