Dietary Green Alfalfa Supplementation Reduces Backfat Thickness and Improves Muscle Water-Holding Capacity in Diqing Tibetan Pigs

Feed scarcity constrains livestock production, particularly on the Qinghai-Tibet Plateau. The effects of green alfalfa (GA) on Diqing Tibetan pig performance remain unclear. This study aimed to evaluate GA effects on Diqing Tibetan pig performance and to explore the potential underlying mechanisms through integrated metagenomic, transcriptomic, and metabolomic analyses. Thirty-six Diqing Tibetan pigs were randomly assigned to two groups and fed either a basal diet or a diet containing 90% basal diet and 10% GA. GA did not adversely affect growth performance but reduced 6–7 rib backfat thickness and muscle water loss rate by 19.79% (FDR = 0.027) and 17.80% (FDR = 0.036), while increasing muscle moisture content by 3.51% (FDR = 0.036). GA increased cecal microbial alpha diversity, Bacteroidota-related taxa, and functional genes related to lipid and vitamin metabolism, while decreasing Bacillota and Lactobacillus johnsonii. In the longissimus dorsi, TNNI1, MYL2 and MYL3 were upregulated, whereas FOS and FOSB were downregulated; GA increased vanillyl alcohol, L-histidine, LPE (0:0/22:5), and licochalcone B, but decreased glyceryl monostearate, benzaldehyde, cortisol, tryptamine, 4-ethyloctanoic acid, 8-methylnonanoic acid, and purine. Overall, 10% GA reshaped gut microbial, muscle transcriptomic, metabolomic profiles and collectively influenced 6–7 rib backfat thickness and muscle water-holding capacity in Diqing Tibetan pigs.