Transcriptome and Metabolome Profiles Reveal the Underlying Mechanism of Fat Deposition Changes in Three-Way Crossbred Yak for High-Quality Beef Production

Yajiangxue cattle (XF) is three-way crossbred cattle developed specifically for producing high-quality beef in the Tibetan Plateau by introducing the bloods of Tibetan yellow cattle (HF) and Angus cattle into Tibetan yak (MF). In the present study, we mainly focused on fat deposition and metabolism changes and used RNA-seq and LC-MS/MS-based metabolomics to partially explain the meat quality improvement in Yajiangxue cattle. Differential expression analysis revealed 1762, 2949, and 2931 different expression genes in XF vs. HF, XF vs. MF, and XF vs. cattle-yak (PF), respectively, such as BMP2, WISP2, FGF1, IL1B, IL6, and WNT5B. Immune response, oxidation-reduction processes, and fatty acid metabolism were markedly enriched. Furthermore, an initial identification revealed 319 metabolites using positive ion mode and 289 metabolites using negative ion mode in bovine adipose tissue across four breeds/populations. Of these, 143 were differential metabolites in positive ion mode, while 166 were in negative ion mode. The main pathways of metabolism affected by breed/population were unsaturated fatty acid biosynthesis, tryptophan and tyrosine biosynthesis, primary bile acid biosynthesis, cholesterol metabolism, beta-alanine metabolism, etc. Similarly, both the transcriptome and the metabolome results highlighted fatty acid metabolism. These results could help elucidate the biological mechanisms involved in fat deposition and identify valuable biomarkers for specific metabolite accumulation.