Analysis of Differential Muscle Metabolites in Bactrian Camels Slaughtered at Different Ages by Non-Targeted Metabolomics Based on Ultra-high Performance Liquid Chromatography-Mass Spectrometry

In this study, non-targeted metabolomics based on ultra-high performance liquid chromatography Q-Exactive-mass spectrometry (UPLC-Q-Exactive-MS) was used to explore the differences in the metabolite profiles of muscles from Bactrian camels slaughtered at different ages. The results showed that a total of 710 differentially expressed metabolites (DEMs) were identified in the longissimus dorsi muscle of camels from three age groups: Ⅰ (3–4 years old), Ⅱ (6–7 years old), and Ⅲ (9–10 years old). In total, 78 DEMs were found in groups Ⅰ vs Ⅱ, of which 47 were upregulated in group Ⅰ and 31 were upregulated in group Ⅱ. Totally, 49 DEMs were identified in groups Ⅱ vs Ⅲ, of which 18 were upregulated in group Ⅱ and 31 were upregulated in group Ⅲ. In addition, 65 DEMs were identified in groups Ⅰ vs Ⅲ, of which 29 were upregulated in group Ⅰ and 36 were upregulated in group Ⅲ. The results of Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that the DEMs were mainly enriched in pathways such as protein and amino acid metabolism, fatty acid metabolism, and vitamin and mineral metabolism, indicating that the digestion and metabolism of various nutrients in camels were different at different growth stages. The contents of polyunsaturated fatty acids (PUFA) (especially n-6 PUFA and n-3 PUFA) and the PUFA/unsaturated fatty acid (UFA) ratio were significantly higher in group Ithan Ⅲ, which was mainly related to the significant upregulation of arachidonic acid, linoleic acid and 13-L-hydroperooleic acid concentrations in relevant metabolic pathways. Meanwhile, DEMs such as L-leucine, L-valine, and L-glutamine could serve as potential markers for evaluating the quality change of camel meat at different slaughter ages.