Metabolome Combined with 16S rDNA Sequencing Reveals a Novel Mechanistic Insight into the Collaboration of Resveratrol and β-Hydroxy-β-Methylbutyric Acid in Regulating the Meat Quality of Tibetan Sheep Through Altering Rumen Microbiota

Resveratrol (RES), a natural polyphenol, and β-hydroxy-β-methylbutyric acid (HMB), a key metabolite of leucine, are emerging as potent feed additives in animal production. This study investigated the individual and combined effects of dietary RES and HMB on gut microbiota, metabolic profiles, and meat quality in Tibetan sheep. A total of 120 two-month-old male lambs were randomly assigned to four experimental groups: control (C, basal diet, n = 6), RES (basal diet + 1. 5 g/d RES, n = 6), HMB (basal diet + 1. 25 g/d HMB, n = 6), and RES-HMB (basal diet + 1. 5 g/d RES + 1. 25 g/d HMB, n = 6), with 16S rDNA sequencing and LC-MS/MS analyses performed on rumen fluid and longissimus lumborum (LL). Meat quality improved significantly in all supplemented groups, the RES-HMB co-administration exhibited the most pronounced effects, suggesting a synergistic interaction. These improvements were linked to the activation of amino acid (AA) and unsaturated fatty acid biosynthesis pathways, leading to increased levels of AAs and polyunsaturated fatty acids (PUFAs). Concurrently, dietary RES and HMB supplementation enriched the relative abundance of beneficial gut microbiota, notably ChristensenellaceaeR-7group and Solibacillus, which further promoted the production of short-chain fatty acids, AAs, and PUFAs. The study highlights the role of rumen microbiota in regulating muscle metabolism and meat quality, offering a new scientific basis of strategies for using green feed additives in Tibetan sheep.