Abstract
OBJECTIVES: Milk and dairy products are a major component of dietary intake, with milk consumption estimated at 6 billion people globally. Adults are reported to consume two or more portions of dairy daily. Cow's milk is composed of a variety of micro and macro nutrients, which is impacted by a range of factors, including lactation stage, and feeding system (indoor vs. pasture). Application of Metabolomics provides in depth analysis of the metabolite composition of milk. The objective was to examine the impact of lactation on bovine milk metabolite levels. METHODS: Metabolomic analysis of bovine milk powder samples across lactation (N = 18), was performed using (1)H-NMR. Metabolites were quantified using Chenomx software (7.7). One-way repeated measures of analysis variance (ANOVA) with Tukeys post hoc test, was preformed on NMR data using SPSS (version 24.0), to assess the impact of lactation stages. P-values were corrected for multiple comparisons using Benjamini and Hochberg false discovery rate (FDR) procedure. Multivariate statistical analysis of the (1)H-NMR data was carried out using SIMCA 13 (SIMCA Version 13.0.3.0 Umetrics, AB). RESULTS: 42 metabolites were identified and quantified in the (1)H-NMR spectra. Statistical analysis revealed that 17 metabolites were significantly different across lactation stages (FDR < 0.05). Of these 17 metabolites, the majority had higher concentrations in early lactation. Examples of metabolites that changed with lactation stage include the tricarboxylic acid cycle intermediates citrate and 2-oxoglutarate, amino acids, choline and phosphocholine. Interestingly choline and phosphocholine levels changed in opposite directions. CONCLUSIONS: Our results demonstrate significant differences in metabolites across the stages of lactation, with early lactation having a distinct metabolic profile. Future work will explore these compositional differences further, encompassing animal feeding practice. FUNDING SOURCES: Food for Health Ireland and Enterprise Ireland.