Optimising bio-conversion efficiency using exogenous Bacillus probiotic strains in black soldier fly larvae (Diptera: Stratiomyidae)

Thaddeus Zaabwe; Elias Chirwa; Kumbukani Mzengereza; Jeremiah Kang'ombe; Abigail Ndhlovu; Robert Nyirenda; Chimango Mtekateka

doi:10.5455/EJSRR.20250606103652

Abstract
Aim: Black soldier fly larvae (Hermetia illucens) have beneficial microbiota that help them convert organic waste into valuable nutrients such as proteins and lipids, essential in animal growth and health. Despite growing interest in probiotic applications in black soldier fly culture, most existing studies focus on naturally occurring microbial communities or generalized probiotic blends without evaluating the specific contributions of exogenous probiotic strains. The current study focused on using exogenous Bacillus probiotic strains on black soldier fly larvae growth, nutrient accumulation and survival.
Methods: A total of 1500 manually counted 4-day-old black soldier larvae per treatment in triplicate were used. These were subjected to exogenous Bacillus probiotic strain inoculation levels per kilogram of poultry feed in a 12-day experiment. Inoculation levels were designated as P0 as a control, P1 as treatment 1, P2 as treatment 2 and P3 as treatment 3. The experiment was carried in the laboratory in a completely randomised design. Larvae were raised under ambient conditions, with an average temperature of 28 ± 1.09 °C and relative humidity of 70 ± 8.1%, using poultry feed with a pH of 8.2 ± 1.0.
Results: Significant differences across inoculation levels for length, weight, survival and proximate composition of larvae were observed, P <.001. Larvae fed P2 inoculated feed showed significantly higher length, weight, survival rates, and protein content.
Conclusion: The study indicated that exogenous Bacillus probiotic strains inoculation at P2 levels not only improves black soldier fly larvae growth and survival rates but also nutrient accumulation, thus increasing their overall production.

Key words: Probiotics, bioconversion, nutrient accumulation, inoculation, black soldier fly larvae, optimisation, proximate analysis