Dietary Energy Levels Impact on Skin Microbiota and Metabolites of Yaks

The study aims to investigate the skin microbiome composition of Yaks and the effects of different dietary nutrient levels on the skin microbiome diversity and metabolites. A total of 19 healthy Tianzhu White Yaks at two age stages (2.5 and 4.5 years old) were selected and fed either a high-energy diet (<i>n</i> = 9) or a low-energy diet (<i>n</i> = 10). After 90 days of feeding, skin microbiota and skin tissue metabolites were detected using 16S rRNA sequencing and LC-MS/MS untargeted metabolomics, respectively. The results showed: (1) the phyla Firmicutes, Actinobacteriota, Proteobacteria, and Bacteroidetes exhibited relatively high abundances in the skin of yaks, and the total abundance of these four phyla reached as high as 99.3%. Alpha diversity analysis indicated that the alpha diversity index of yak skin microbiota was significantly higher (<i>p</i> < 0.05) in the low-energy nutritional level group than in the high-energy nutritional level group in yaks of both 2.5 and 4.5 years of age. Principal coordinate analysis (PCoA) revealed a distinct separation of all skin microbiota samples into two clusters: the high-energy (H) and low-energy (L) groups. (2) A total of 114 differentially expressed metabolites were screened across both groups, significantly enriched (<i>p</i> < 0.05) in pathways including synaptic vesicle trafficking and glycerophospholipid metabolism; (3) Correlation analysis between microbiota and metabolites revealed significant positive correlations (<i>p</i> < 0.01) between <i>Psychrobacter</i> and choline, and between <i>Corynebacterium</i> and palmitic acid. In conclusion, A low-energy diet increases skin microbial diversity, which is beneficial for maintaining community stability; In contrast, a high-energy diet enriches bacterial genera such as <i>Corynebacterium</i> and <i>Psychrobacter</i>, enhancing functions related to antibacterial activity and barrier protection.