Shall we re-feed 5-day-old Black Soldier Fly larvae?
A widespread practice is once-feeding 5-day-old-larvae (5-DOL) for 6-9 days until harvesting. While such long time and amount of substrates exposure to air, microorganisms might contribute to substrate spoilage and volatilization and leads to limited substrate availability for BSF larvae. A precise feeding strategy, i.e., re-feeding (multiple-feeding) might be needed.
As shown in Parodi et al. (2020), by adding fresh substrate to BSF larval residues (frass + uneaten substrate), CO2 production takes place due to microbial activity, accounting for 34% of overall emissions. Thus, the contribution of microbial respiration is substantial, leading to inefficient feed conversion and excess heat production (a high substrate temperature).
Re-think Feed-Conversion Efficiency, it is better to lower down the microorganism-related substrate consumption as shown in once-feeding; and to offer more feed availability for BSF larvae by re-feeding. Although adding beneficial bacteria can help to increase conversion efficiency, excessive fermentation could also have a negative impact on larval growth.
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