Human breast milk (HM) is the gold standard for feeding newborns and infants. In situations where this is not possible, commercial infant formulas (IF) are normally used. However, IFs contain lower amounts and diversity of oligosaccharides compared with HM, which contains at least 200 different types of human milk oligosaccharides (HMOs). These are a key component of HM and play a critical role in shaping the development of the infant gut microbiota, protecting against infection, and enhancing immune development in breastfed infants. Consequently, today, IFs are often supplemented with oligosaccharides (including a small number of permitted synthetic HMOs) in attempts to bridge this nutritional gap. This study investigated the effect of cow’s (CIF) and goat’s (GIF) milk-based IFs (reconstituted CIF and GIF) versus HM on gut microbiota diversity and short-chain fatty acid production using an in vitro gut model simulating the digestive tract of an infant. Oligosaccharide fractions were prepared from these milks and used as carbon sources (along with controls) for the gut model.
Results showed that all three types of milks (HM, CIF and GIF) promoted bacterial growth, with significant differences in the relative abundances of Bifidobacterium, Lactobacillus, Escherichia-Shigella, other Enterobacteriaceae and other bacterial taxa determined by qPCR and 16S rRNA gene sequencing-based profiling. Alpha- and beta-diversity analysis of the latter results revealed different levels of microbial diversity. Fermentation of all three types of milk oligosaccharides increased production of acetic and propionic acids, but caused a reduction in isobutyric, butyric, 2-methylbutyric, isovaleric and valeric acids. Reconstituted GIF caused higher levels of butyric acid production than did CIF and HM. Results further showed that inter-individual differences for HM between mothers had a major influence on the diversity of the gut microbiota, and that microbial composition and SCFA profiles for GIF and HM were more similar to each other than to those for CIF. This finding is consistent with earlier observations that goat’s milk oligosaccharides are relatively more similar to those found in human milk compared with those in cow’s milk.