Effects of Allium mongolicum Essential Oil on Meat Quality and Flavor-Related Free Amino Acids in Finishing Lambs

The objective of this study was to evaluate the effects of dietary Allium mongolicum Regel essential oil (AMO) supplementation on growth performance, carcass traits, meat quality, and muscle amino acid profile in finishing lambs. A total of twenty male Dorper × Han crossbred lambs (body weight = 32.5 ± 2.5 kg, 4–4.5 months old) were randomly allocated into two dietary treatments (n = 10 per group): a control group fed a basal diet (roughage to concentrate ratio of 45:55) or an AMO group supplemented with 56 mg/d of AMO per lamb. The trial consisted of a 15-day adaptation period followed by a 60-day experimental period. At the end of the trial, six lambs were randomly selected from each group for slaughter. Samples of the longissimus thoracis (LT) muscle were collected to determine meat quality traits, proximate composition, and amino acid profiles. Supplementation increased average daily gain by 6.6% and improved feed conversion ratio by 4.6% (p < 0.05), whereas feed intake and final body weight were not affected (p > 0.05). In LT, GR tissue depth and loin muscle area were increased (p < 0.05). Drip loss was reduced (p < 0.05), whereas proximate composition, cooking loss, and shear force remained unchanged (p > 0.05). The hydrolyzed amino acid composition and protein nutritional value of LT were not affected (p > 0.05). However, total free amino acid (FAA), total essential FAA, and the concentrations of free leucine, isoleucine, lysine, valine, phenylalanine, tyrosine, alanine, glutamic acid, glycine, and cysteine were increased by supplementation (p < 0.05). Moreover, flavor-related FAA, including umami-, sweet-, and bitter/sweet/sulfurous-related FAA were also increased by supplementation (p < 0.05). These results indicate that AMO improves growth efficiency and enhances LT meat quality, particularly by increasing flavor-related FAA, without altering protein nutritional characteristics.