Metabolomic Analysis of Wu Ranke Sheep Liver

A total of 28 LCu, SCu, LCG, and SCG Wu Ranke sheep liver samples were extracted metabolites by standard procedures [20 (link)]. The sample extracts were analyzed by a Vanquish UHPLC system coupled with an Orbitrap Q ExactiveTM HF mass spectrometer (ThermoFisher, MA, USA). The chromatographic and mass spectrometric conditions are shown in Table S5.
The raw data files generated by UHPLC-MS/MS were processed using the Compound Discoverer 3.1 (CD3.1, ThermoFisher) to perform peak alignment, peak picking, and quantitation for each metabolite. After that, peak intensities were normalized to the total spectral intensity. The normalized data were used to predict the molecular formula based on additive ions, molecular ion peaks and fragment ions. And then peaks were matched with the mzCloud, mzVault and MassList databases to obtain accurate qualitative and relative quantitative results.
Variable importance in projection (VIP) ≥ 1, |log₂ fold change|≥ 1 and p < 0.05 were identified as the significantly accumulated metabolites (DEMs) between LCu and LCG, SCu and SCG. The functions of the DEMs enriched pathways were studied using the Kyoto Encyclopedia of Genes and Genomes (KEGG) database (https://www.genome.jp/kegg/pathway.html). When the metabolic pathway p value was less than 0.05, the metabolic pathway was considered statistically significant enrichment [18 (link), 21 (link)].