Effect of protein and carbohydrate feed concentrations on the growth and composition of black soldier fly (Hermetia illucens) larvae

Black soldier flies (Hermetia illucens) can be used for a wide range of applications, from screening their anti-microbial properties, entomophagy through to waste management. Although the use of black soldier flies for these purposes has been widely studied, mass-rearing black soldier flies is still in the preliminary phase. This study focussed on the nutritional composition of black soldier fly larvae over the course of their life history, and the impact of manipulating dietary protein and carbohydrate on the growth and composition (protein and fat) of the larvae. Larvae were collected every 24 h over the course of this life-stage to test for differences in composition. To test the effect of dietary protein and carbohydrate differences, larvae were fed 25 diets with varying concentrations of protein and carbohydrates. Overall, the composition of larvae changed very little over their life history, with the higher concentration of protein mostly observed in the earlier instars of the larvae. The pre-pupal stage reduced the fresh and dry weight of the larvae, whereas the ash concentration was very stable throughout their life history. Both dietary protein and dietary carbohydrate had a significant effect on the fresh and dry weight of the larvae, but dietary protein was a stronger indicator of larval fresh and dry weight than dietary carbohydrate. Larval composition was also influenced by the feed-type, with heavier larvae producing significantly more fat than the lighter ones.