Effects of black soldier fly replacing fish meal on growth performance, serum parameters, and intestinal microbiota of weaned piglets

This study evaluated the effects of replacing fish meal (FM) with black soldier fly (BSF) at different levels on growth performance, nutrient utilization, serum parameters, intestinal microbiota, and microbial metabolites in weaned piglets. A total of 180 weaned piglets (28 days old) were randomly assigned to one of five dietary treatments (n = 6 pens/treatment; 6 pigs/pen): BSFF0 (basal diet), BSFF25 (25% FM replaced by BSF), BSFF50 (50% FM replacement), BSFF75 (75% FM replacement), and BSFF100 (100% FM replacement). Partial or complete replacement of FM with BSF had no adverse effects on the growth performance or diarrhea incidence of piglets. The apparent total tract digestibility of crude protein and ether extract increased linearly with increasing BSF levels (P < 0.05). Serum concentrations of immunoglobulin A, interleukin-10, high-density lipoprotein, Lys, and Asp increased linearly with increasing BSF levels, while blood urea nitrogen content decreased both linearly and quadratically (P < 0.05). Microbial analysis revealed that BSF inclusion modulated the intestinal microbiota, which was characterized by increased abundances of Lactobacillus and Bifidobacterium and a decreased abundance of Streptococcus (P < 0.05). Furthermore, concentrations of fecal valerate (P = 0.071) and acetate (P = 0.070) tended to increase quadratically with increasing BSF levels. The concentrations of biogenic amines (tryptamine, putrescine, cadaverine, and spermidine) decreased linearly with increasing BSF levels (P < 0.05). In conclusion, these findings demonstrate that replacing 25% to 100% of FM with BSF maintained growth performance while enhancing immune status and regulating microbial metabolites in weaned piglets.