Supplemental Allium mongolicum Regel reduces key mutton flavor 4-alkyl-branched chain fatty acids in longissimus dorsi muscle by regulating rumen microbiota and metabolism of lambs

Allium mongolicum Regel ( AMR ) can reduce mutton gamey flavor and mediate changes in rumen microbiota and metabolism, but how it achieves this effect is unclear. This study investigated the effects of dietary supplementation with AMR on rumen microbiota and key 4-alkyl-branched chain fatty acids ( KBCFA) , including 4-methyloctanoic acid ( MOA ), 4-ethyloctanoic acid ( EOA ), and 4-methylnonanoic acid ( MNA ) in longissimus dorsi ( LD ) muscle of lambs. Twenty Small-tailed Han sheep × Dorper sheep (28 ± 2.2 kg) were randomly assigned to two groups: control group (a basal diet, CON ); treatment group (a basal diet supplemented at 15 g/d per lamb of AMR powder, AMRP ). The experiment uses a complete randomized design. In the AMRP group, the level of KBCFA in LD muscle was significantly reduced, and the concentrations of propionate and total volatile fatty acids in the rumen were significantly decreased ( P < 0.05). All carbohydrate-binding module families decreased, glycosyltransferase families increased by 60 %, and most carbohydrate esterase families remained unchanged or decreased. The relative abundance of the species Prevotella sp. Rep29 was significantly reduced ( P < 0.05). The MNA negatively correlated with several bacteria, while MOA positively correlated with P. sp. Rep29 ( P < 0.05). Co-occurrence networks indicated bacterial stability surpassed that of archaea and fungi in the rumen. Metabolic pathways tied to pantothenate and CoA biosynthesis were significantly upregulated in the AMRP group ( P < 0.05). The experiment demonstrates that supplementing with 15 g/d per lamb of AMR powder can effectively reduce KBCFA levels in LD muscle, which is related to rumen carbohydrate-degrading bacteria. • Allium mongolicum Regel reduced the 4-alkyl branched fatty acids in lamb meat. • Allium mongolicum Regel altered the rumen microbiota. • Allium mongolicum Regel altered the rumen metabolic profile. • Rumen carbohydrate-degrading bacteria are associated with the mutton flavor.