In vitro fermentation of sheep and cow milk using infant faecal bacteria

While human milk is the optimal food for infants, formulas which contain ruminant milks can have an important role where breast feeding is not possible. In this regard cow milk is most commonly used. However, recent years have brought interest in other ruminant milks. While many similarities exist between ruminant milks, there are likely enough compositional differences to promote different effects in the infant. This may include effects on different bacteria in the large bowel, leading to different metabolites in the gut. In this study sheep and cow milk were digested using an in vitro infant digestive model, followed by faecal fermentation using cultures inoculated with faecal material from two infants of one month and five months of age. The effects of the two milks on the faecal microbiota, short-chain fatty acids (SCFA) and other metabolites were investigated. Significant differences in microbial, SCFA and metabolite composition were observed between fermentations of sheep and cow milk using faecal inoculum from a one-month old infant, but comparatively minimal differences using faecal inoculum from a five-month old infant. These results show that sheep milk and cow milk can have differential effects on the gut microbiota, while demonstrating the individuality of the gut microbiome.