Individual and Combined Effects of 2′-Fucosyllactose and Bifidobacterium longum subsp. infantis on the Gut Microbiota Composition of Piglets

Background: Human milk is a source of oligosaccharides that promote the growth of beneficial bacteria, including Bifidobacterium longum subsp. infantis, which can utilize human milk oligosaccharides. Objectives: To evaluate the individual and combined effects of 2′-fucosyllactose (2′-FL), B. infantis Bi-26 (Bi-26) on piglet gut microbiota composition, and short-chain fatty acid (SCFA) concentrations. Methods: Intact male pigs (n = 63) had ad libitum access to milk replacer without (control; CON) or with 1.0 g/L 2′-FL (FL) from postnatal day 2 to 34/35. Pigs were further stratified to receive either 12% glycerol or 10⁹ CFU/d Bi-26 in glycerol (BI and FLBI). Gut microbiota and SCFA concentrations were determined in ascending colon contents (AC) and rectal contents (RC) by 16S ribosomal ribonucleic acid gene sequencing and gas chromatography, respectively. Microbiota composition and functional profiles were analyzed using QIIME 2 and Phylogenetic Investigation of Communities by Reconstruction of Unobserved States-2 (PICRUSt2). Results: Supplementation of 2′-FL increased valerate concentration in AC (P = 0.03) and tended to modulate the overall bacterial composition in RC (P = 0.06). Compared with CON, 2′-FL alone increased the acetate concentration in AC (P < 0.05). The addition of Bi-26 decreased Shannon indices and reduced propionate and butyrate concentrations in AC (P < 0.05). Bi-26 alone affected the relative abundances of several bacterial amplicon sequence variants (ASVs) in AC and RC, including the ASVs identified as Phocaeicola (Bacteroides) vulgatus and Faecalibacterium prausnitzii. Additionally, 2′-FL and Bi-26 individually increased the relative abundances of 9 PICRUSt2-predicted metabolic pathways related to fatty acid and lipid biosynthesis or carboxylate degradation/secondary metabolite degradation in the RC; however, these effects were negated, and the values were identical to the CON group when 2′-FL and Bi-26 were supplemented together. Conclusions: 2′-FL and Bi-26 added to milk replacer exerted distinct influences on gut bacterial composition and metabolic function, and 2′-FL alone increased specific SCFA concentrations, demonstrating its prebiotic potential.