A metabolomics approach to characterize phenotypes of metabolic transition from late pregnancy to early lactation in dairy cows

Introduction: Dairy cows experience metabolic stress during the transition from late pregnancy to early lactation, due to the complex adaptation processes affecting energy homeostasis in support of milk production, collectively referred to as homeorhesis. According to the individual efficiency of this adaptation, some cows develop severe metabolic diseases while others are able to maintain metabolic health. Objectives: This study aimed to characterize patterns and changes of metabolic phenotype during the transition period, and to identify how far different metabolic pathways are affected by or contributing to the complex system of homeorhesis. Methods: Blood samples were collected from 26 German Holstein cows, repeatedly during the transition period: 42 and 10 days before calving and 3, 21 and 100 days after calving. Blood serum samples were subjected to a liquid chromatography–mass spectrometry based targeted metabolomics analysis using the AbsoluteIDQ p180 Kit of Biocrates Life Science AG (Innsbruck, Austria). Processed metabolomics data were evaluated by multivariate data analysis techniques such as principal component analysis (PCA) and partial least squares-discriminant analysis and by heatmap visualization. Results: The PCA revealed a clear separation according to sampling days, indicating a notable shift of the metabolic phenotype during the transition period. The heatmap showed that acylcarnitines provided a consistent clustering within sampling days, while the concentration of glycerophospholipids and sphingolipids were remarkably decreased 10 days before and 3 days after calving than earlier and later in the transition period. Conclusion: Analyzing longitudinal changes of the blood metabolome and identifying new biomarkers by this approach can help understanding the multifaceted metabolic adaptation of transition dairy cows.