Using of NMR Milk Metabolomics to Evaluate Mammary Gland Health Status in Dairy Cows

Objectives. Milk of mammal origin is an important food in the diet during infancy as well as in adulthood. It contains lipids, proteins, carbohydrates, essential nutrients, bioactive compounds (immunoglobulins, oligosaccharides), organic acids, nucleotides, micronutrients, and metabolites. Milk metabolites may originate from multiple cell types or metabolisms. The milk quality is affected by different factors, such as lactation stage, feed, genetic background, and cow health. Somatic cell count (SCC) is normally used as an indicator of mastitis. Here we proposed to use milk metabolites as indicators of mammary gland health status. Methods. A total of 44 dairy cows of four different breeds (Holstein, Simmenthal, Simmenthal x Holstein crossbred, and Podolica) were enrolled for this study. Immediately after morning milking, milk samples (around 60 days after calving) were collected and placed on ice for transport to the laboratory. Once in the laboratory, the milk samples were aliquoted, and frozen at −80 ℃. Nuclear magnetic resonance (NMR) spectroscopy was used to determine milk metabolites. Samples were classified as “high” (≥400.000) or “low” (≤400.000) SCC content. The metabolite profiles in the two classes were analysed to identify differences. A General Linear Model (GLM) procedure was used to identify the statistically significant differences of metabolites content. Results. NMR spectra confirmed milk metabolites associated with a high number of SCC, already identified in previous studies, where many milk samples were analysed. In this study, four new metabolites (N-acetyl-lysine, N-acetyl-glutamine, creatinine, phosphocreatine,) were associated to high somatic cell count and could be used as biomarkers of mammary gland health status.n