Valorization of chicken manure with bread waste, yeast and cyanobacterium Spirulina platensis to enhance black soldier fly larval performance

Abstract

Chicken manure (CM) is a nutrient-rich agricultural byproduct, yet its imbalanced composition, notably high ash and low energy, makes it unsuitable as a sole substrate for black soldier fly (BSF) larvae. This study evaluated a two-part valorization strategy: co-substrate blending with bread waste (BW) and microbial supplementation with yeast (Saccharomyces cerevisiae) or the cyanobacterium Spirulina platensis. Eleven dietary treatments were tested, revealing significant performance differences (P < 0.001). The 1CM:1BW + Yeast diet emerged as the most effective formulation, yielding the highest larval biomass (10.6 g dry weight/100 larvae) and the most efficient feed conversion ratio (FCR) of 4.1. Conversely, the CM + S. platensis group performed even worse than the CM control, demonstrating that a high-protein supplement can create a metabolic “energy trap” in an energydeficient substrate. Proximate analysis confirmed a strong diet-larva correlation; the most effective diet produced larvae with a more balanced proximate composition (~31% fat), whereas CM-fed larvae accumulated excessive ash (43.3%). These findings demonstrate that blending CM with an energy-rich co-substrate like BW is a critical prerequisite. This strategy not only dilutes inhibitory components like ash but also unlocks the potential of microbial supplements, offering a practical pathway to transform low-value waste into high-quality insect biomass for animal feed.