GC/MS and LC/MS Based Serum Metabolomic Analysis of Dairy Cows With Ovarian Inactivity

Metabolic disorders may lead to the inactive ovaries of dairy cows during early lactation. However, the detailed metabolic profile of dairy cows with inactive ovaries around 55 days postpartum has not been clearly elucidated. The objective of this study was to investigate the metabolic difference in cows with inactive ovaries and estrus from the perspective of serum metabolites. According to clinical manifestations, B-ultrasound scan, rectal examination, 15 cows were assigned to the estrus group (E; follicular diameter 15-20 mm) and 15 to the inactive ovary group (IO; follicular diameter <8 mm and increased <2 mm within 5 days over two examinations). The blood was collected from the tail vein of the cow to separate serum 55-60 days postpartum, and then milked and fasted in the morning. Serum samples were analyzed using gas chromatography time-of-flight mass spectrometry technology (GC-TOF-MS) and ultra-high-pressure liquid chromatography-quadrupole-time-of-flight mass spectrometry (UHPLC-QTOF-MS). Differences in serum metabolites were identified using multivariate statistical analysis and univariate analysis. Thirty differentially abundant metabolites were identified between the two groups. In cows with inactive ovaries compared with cows in estrus, 20 serum metabolites were significantly higher (beta-cryptoxanthin (p = 0.0012), 9-cis-retinal (p = 0.0030), oxamic acid (p = 0.0321), etc.) while 10 metabolites were significantly lower (monostearin (p = 0.0001), 3-hydroxypropionic acid (p = 0.0005), D-talose (p = 0.0018), etc.). Pathway analysis indicated that the serum differential metabolites of multiparous cows in estrus obtained by the two metabolomics techniques were mainly involved in β-alanine metabolism and steroid biosynthesis metabolism, while other involved metabolic pathways were related to metabolism of glyoxylate; dicarboxylate metabolism; fructose, mannose, glutathione, glycerolipid, glycine, serine, threonine, propanoate, retinol, and pyrimidine metabolism. This indicates that the abnormalities in glucose metabolism, lipid metabolism, amino acid metabolism, and glutathione metabolism of postpartum dairy cows obstructed follicular development.