Comparative Full-Length Transcriptomic and Untargeted Metabolomic Profiling of Longissimus Dorsi Muscle in Female Ashdan Yaks at Three Postnatal Ages

To characterize age-associated molecular differences in the longissimus dorsi muscle of female Ashdan yaks, this study combined Oxford Nanopore Technologies (ONT) full-length transcriptomic sequencing and untargeted LC-MS metabolomics in 27 independent animals aged 10 days (M0), 6 months (M6), and 54 months (M54), with nine animals per group. At BH q < 0.05 and |log2FC| > 1, the three pairwise comparisons identified 1999, 3480, and 2350 differentially expressed genes, respectively, with the largest set between M0 and M54. Networks reconstructed from these gene sets identified high-connectivity candidates, including ENSBGRG00000003669 in comparisons involving M0 and MRTO4 and BYSL in M6 vs. M54. Of 1842 retained annotated LC-MS peak features, 1487, 1474, and 1285 were differential at BH q < 0.05; 676, 589, and 452 also showed at least twofold differences. Separate gene-overrepresentation and quantitative metabolite member-profile tests supported oxidative phosphorylation in both comparisons involving M0 and purine metabolism in M0 vs. M6. Alanine, aspartate and glutamate metabolism showed recurring metabolite-profile differences without significant gene overrepresentation. Among 1860 matched gene-feature pairs, 977 pooled associations passed BH q < 0.05. The transcript resource included 4642 novel candidates and 14 unique differential splicing candidates. These findings characterize age-associated transcriptional and metabolic variation and prioritize pathways and computational candidates for subsequent study.