Intestinal microbiota and transcriptomic alterations in the jejunum following supplementation with probiotic strain Lacticaseibacillus paracasei NSMJ15 in early-age broiler chickens

This study aimed to assess the effects of probiotic Lacticaseibacillus (Lc.) paracasei NSMJ15 supplementation on both the microbiota and transcriptome profiles in the small intestine of ten-days-old-broiler chickens. A total of 160 one-day-old male Ross 308 broiler chicks were randomly assigned to two dietary groups: a non-supplemented control group and an NSMJ15-supplemented group (8 pens per group, ten birds per pen). The diets consisted of a corn-soybean meal-based control diet and a test diet in which NSMJ15 (10⁶ cfu/g) replaced 5 g/kg of ground corn. On day 10, one broiler per cage was euthanized, and jejunal contents and tissue samples were collected for microbiota and transcriptomic analyses. 16S rRNA amplicon sequencing demonstrated that NSMJ15 supplementation altered the bacterial community composition and increased bacterial diversity. Notably, the genus Lacticaseibacillus (=Lc. paracasei NSMJ15) reached an average relative abundance of 16.5% in the jejunum. However, the variation was observed among the samples, ranging from 0.16% to 51.79%, suggesting that the extent of NSMJ15 colonization may be influenced by the indigenous microbial community. To investigate the transcriptomic responses associated with NSMJ15 colonization, RNA-seq was performed on six selected samples (three control and three NSMJ15-supplemented). Mapping the RNA-seq reads to the chicken (Gallus gallus) genome revealed 287 differentially expressed genes (DEGs), including 140 upregulated and 147 downregulated genes. KEGG pathway enrichment analysis revealed that the cytokine-cytokine receptor interaction (CCRI) pathway was the most significantly enriched and several immune-related genes including IL8, IL22, IFNL3A, and CCL4 were differentially expressed. In addition, indigenous genera such as Mediterraneibacter, Blautia, Bacillus, Monoglobus, Lactococcus, and Pseudoescherichia were altered in association with NSMJ15 colonization and showed significant correlations with host DEGs. Collectively, our data suggest that Lc. paracasei NSMJ15 supplementation may modulate jejunal microbiota composition and host immune- and nutrient metabolism-associated gene expression, highlighting coordinated microbiota-host interactions in early-age broiler chickens.