Impact of Artificial Diet Versus Mulberry Leaves on Silkworm Growth, Nutrient Composition, and Gut Microbiota

Silkworms (Bombyx Mori) are traditionally reared on mulberry leaves; however, artificial diets have been developed to enable year-round rearing and automation. The physiological performance and cocoon yield of silkworms fed artificial diets remain inferior to those reared on mulberry leaves. We compared growth and nutrient composition in larvae reared on mulberry leaves (ML) and antibiotic-free artificial diet (ADS), and profiled gut microbiota in ML, ADS, and antibiotic-supplemented artificial diet (ADSA) to assess dietary effects on host physiology and microbial ecology. Proximate analysis revealed that protein accumulation was greater in ML-fed larvae, while ADS-fed larvae showed relatively higher fat content at the late fifth instar. Amino acid profiling showed consistently higher silk-related residues (Gly, Ala, Ser) and the derived Silk Amino Acid Index in ML-fed larvae, indicating enhanced fibroin synthesis potential. Microbiome analysis using 16S rRNA amplicon sequencing demonstrated dominance of Enterococcus mundtii in ADS groups, resulting in reduced alpha diversity and uneven community structure. In contrast, ML-fed larvae harbored diverse taxa, including Methylorubrum and Methylobacterium, while ADSA groups exhibited intermediate profiles with occasional dominance of Bacillus cereus. These findings highlight that artificial diet alters host nutrient metabolism and drives dysbiosis of gut microbiota, underscoring the need for optimized formulations and microbiome-stabilizing strategies, such as probiotics or prebiotics.