Effects of Hermetia illucens larvae full-fat meal and astaxanthin on the microbiome and histomorphology of the large intestine in piglets

This study evaluated the effects of Hermetia illucens (HI) larvae full-fat meal and astaxanthin (AST) on large intestine histomorphometry, microbiota activity, and composition in pigs. Forty-eight pigs (8.7 kg) were divided into six groups: control (0HI), 2.5% HI (2.5HI), 5% HI (5HI), 2.5% HI + AST (2.5HI+AST), 5% HI + AST (5HI+AST), and AST alone (AST). The experiment lasted from 35 to 70 days of age. HI meal increased mucosal thickness (p<0.01), crypt depth (p<0.05), and width (p<0.05). Goblet cell counts increased in the 2.5HI (p<0.05), while enterocyte numbers decrease in the AST group (p<0.01). Dietary HI meal reduced concentrations of total short-chain fatty acids (SCFA), including butyrate (p<0.05), whereas AST increased acetic acid levels in multiple intestinal regions (p<0.05). Both additives modified microbial populations: AST increased total bacterial counts (p<0.001), while 2.5% HI meal reduced the abundance of the Bacteroides–Prevotella cluster (p<0.001). Significant interactions were detected for Lactobacillus/Enterococcus spp. and Enterobacteriaceae (p<0.001). HI meal decreased p-cresol concentrations in the middle colon (p<0.05), whereas AST reduced phenol in the distal colon (p<0.05) and indole in the middle colon (p<0.05). AST increased ammonia levels in the proximal colon (p=0.001). These findings suggest that HI meal and AST modulate intestinal fermentation, exhibit anti-inflammatory effects, and regulate microbial populations, potentially reducing harmful metabolites and odor emissions. Their dietary combination may have positive implications for intestinal health.