Alterations in milk and blood metabolomes during the first months of lactation in dairy cows

The molecular composition of milk is influenced by various genetic and environmental factors. Time is one important factor, and the fact that certain milk components change over the course of lactation is widely accepted. Untargeted global metabolomics is an approach to study hundreds of low molecular weight compounds simultaneously. In this study, mass spectrometry-based global metabolomics was used to follow the course of changes in milk (n=133) and blood plasma (n=133) during the early stage of lactation. Little correlation was found between the molecular composition of blood plasma and milk. Blood showed a higher dependence on animal individuality than did milk, in which common evolutions in time resolved. Citrate and lactose had the greatest effect on these changes; however, the most significant changes in milk during the first months of lactation were associated with phosphorylated saccharide levels, whereas the most significant changes in blood plasma were associated with levels of polyunsaturated fatty acids containing phosphatidylcholine. In conclusion, a new systemic approach was used to search for minor metabolites whose concentrations were significantly altered in milk and blood during the first months of lactation.