Effects of feeding black soldier fly larvae with yellow wine lees on growth performance, nutrient composition, and gut microbiota.

INTRODUCTION: Yellow wine lees (YWL) are a nutrient-rich by-product of yellow wine brewing and have potential as a feed substrate for black soldier fly larvae (BSFL, Hermetia illucens); however, their effects on larval growth, nutrient composition, and gut microbiota remain unclear. METHODS: Six diets containing 0% (T0), 10% (T1), 20% (T2), 30% (T3), 40% (T4), and 50% (T5) YWL (w/w) were fed to four-day-old larvae for 16 days until the prepupal stage. Larval average dry weight, feed reduction rate, crude protein (CP), and ether extract (EE) were measured; gut bacterial communities were characterized by 16S rRNA high-throughput sequencing. RESULTS: Larvae fed the T3 diet (30% YWL) achieved the highest average dry weight (83.69 mg) and feed reduction rate (68.49%); inclusion levels of 40% or higher significantly inhibited larval growth (p < 0.05). CP content peaked in the moderate-inclusion groups (T2 and T3; 47.96-48.37%), while EE increased with the YWL inclusion level. Inclusion of 10-30% YWL maintained microbial species richness, whereas inclusion of 40-50% caused species loss and community imbalance. Moderate inclusion increased the relative abundance of Firmicutes, notably Terrisporobacter, which correlated positively with growth indicators; conversely, high inclusion enriched Fusobacterium and Lachnoclostridium, correlating with growth inhibition and fat accumulation (p < 0.05). DISCUSSION: Replacing cornmeal and wheat bran with 20-30% YWL improved gut microbial structure, BSFL growth efficiency, and larval crude protein content. In contrast, inclusion levels of 40% or higher, accompanied by dietary acidification and ethanol accumulation, induced gut microbial dysbiosis and suppressed larval growth.