Rumen Fluid Transplantation from Allium mongolicum Regel-Fed Donors Enhances Lamb Meat Quality and Reduces 4-Alkyl Branched-Chain Fatty Acids

The extent of consumer approval for lamb is intimately connected to meat quality standards. Within this context, the distinctive 'mutton taint' serves as a critical benchmark for assessment, a characteristic that is largely governed by the concentrations of three fundamental branched-chain fatty acids (KBCFA), specifically 4-methyloctanoic acid (MOA), 4-ethyloctanoic acid (EOA), and 4-methylnonanoic acid (MNA). While <i>Allium mongolicum</i> Regel (AMR)-an Allium species prevalent in arid Asian regions known for its abundant bioactive constituents-is known to improve meat quality and mitigate these off-flavors, the potential mediating role of the rumen fluid in this process remains unclear. This study investigated whether rumen fluid transplantation (RFT) from AMR-fed donors could mimic the impacts of directly adding AMR to the diet on KBCFA accumulation and meat attributes. Thirty male lambs (23 ± 2 kg BW) were allocated at random into three distinct treatments (<i>n</i> = 10): a control set (CON), a dietary supplementation group administered 15 g/d of AMR (AMG), along with a rumen fluid transplantation treatment (RTG) inoculated with rumen fluid from AMR-fed donors. The carcass traits, physicochemical properties, and makeup of amino acids, as well as the fatty acid constitution of the <i>longissimus thoracis</i> muscle, were subjected to analysis. Data revealed that the levels of KBCFAs associated with off-flavors were markedly lowered in both the AMG and RTG. Specifically, decreases ranging from 49% to 64% were observed in MOA, EOA, and MNA concentrations (<i>p</i> < 0.05). Relative to the control group, drip loss and cooking loss were reduced in the treatment groups (<i>p</i> < 0.05), whereas ash (<i>p</i> = 0.047) and crude protein (<i>p</i> = 0.001) were increased. Moreover, the interventions improved the composition of essential amino acids (EAA), flavor-enhancing amino acids, and polyunsaturated fatty acids (PUFAs). In conclusion, rumen fluid transplantation effectively replicates the beneficial effects of dietary AMR on meat quality, particularly in reducing taint-related KBCFA. Such outcomes imply that rumen microbial communities likely act as a crucial mediator in controlling meat flavor.