A metabolomics comparison between sheep's and goat's milk

Despite the worldwide consumption of bovine milk, dairy products from small ruminants, such as goat's and sheep's milk, are gaining a large interest especially in the Mediterranean area. The aim of this work was to study the metabolite profiles of 30 sheep's and 28 goat's milk using an untargeted metabolomics approach by a gas chromatography coupled with mass spectrometry (GC-MS) analysis. Results showed several differences in the metabolite profiles: arabitol, citric acid, α-ketoglutaric acid, glyceric acid, myo-inositol, and glycine were more abundant in sheep's milk, while goat's milk had higher levels of mannose-6-phosphate, isomaltulose, valine, pyroglutamic acid, leucine, and fucose. Associations between metabolite profile and milk compositional traits were also found. Predictive capabilities of statistical models indicated a good correlation between the metabolite profile and the protein content in sheep's milk, and with the fat content in goat's milk. This work leads to a better understanding of milk metabolites in small ruminants and their role in the evaluation of milk properties.