Supplementing feed components is becoming increasingly difficult for various reasons, including increased shipping costs, decreased capture efficiency, and global warming. For this reason, much research has been conducted globally to find alternative protein sources. The black soldier fly (BSF; Hermetia illucens) is an important feed item for nutritional accumulation and has environmental consequences. Few studies have been conducted to determine the nutritional level of the substrate, but most of these studies have involved modifying the substrate material. The aim of this study was to determine the ideal crude protein(CP) content of a substrate for BSF rearing. The experimental treatment was separated into three CP levels (low, 13.5%; medium, 20%; high, 26.5%) in the substrate. The results showed that the BSF weight (6.46%) and protein conversion ratio (1.13%) increased as the substrate CP level increased (p<0.05). In addition, protein (14.38%) and lipid (13.12%) yields were significantly increased (p<0.05). The BSF CP level increased as the substrate CP level increased (p<0.05). CP levels in the substrate upregulated the levels of certain fatty acids, essential amino acids, and non-essential amino acids (p<0.05). In conclusion, the potential values of BSF as feed were improved as the CP level of the substrate increased; However, no difference was found between medium and high CP levels in the rearing substrate. These results suggested that the substrate CP level should be at the medium level for optimal product quality. In conclusion, BSF quality is influenced by substrate nutrient levels, necessitating the development of specialized substrates for effective rearing.

For sustainable livestock industry, black soldier fly as eco-friendly animal protein source is spotlighted for swine and poultry. However, most of black soldier fly is reared in dirty condition like food waste. In this study, we investigated the effects of fiber level on the growth performance and nutrient composition of black soldier fly reared in specific substrate. Treatments were divided in two as Low (fiber level: 7.1%), and High (fiber level: 14.2%) with a total of 50,000 eggs each. The rearing box had a dimension with 1064 × 507 × 320 cm (length × width × height). Black soldier fly survival rate (72.24 vs. 76.48) and substrate consumption (77.43 vs. 80.37) were greater in High than Low. However, bioconversion (10.59 vs. 9.80) and protein conversion (8.97 vs. 8.00) were increased in Low than High. Gross energy was higher in High compared with Low (4,133 vs. 4,208). Some of essential amino acid (Isoleucine, leucine, phenylalanine, threonine, tryptophan) were significantly higher in High compared with Low, and non-essential amino acid (alanine, aspartate, glycine, proline, serine, tyrosine) were higher in High compared with Low. Acids such as C12:0, C14:0, C15:0, and C20:1 were higher in High compared with Low, while C18:4 was higher in Low compared with High. As a result, black soldier fly reared in high fiber substrate might be a preferred option for rearing and producing a reliable animal protein source for monogastric animal.