Application of Thymus quinquecostatus Celak essential oil in lamb diet: Effects on growth performance and meat quality.

This study aimed to evaluate the application value of Thymus quinquecostatus Celak essential oil (TEO) by examining its effects on growth performance, meat quality and oxidative stability, and rumen bacterial composition in lambs. Thirty-six lambs were randomly allocated to four dietary treatments supplemented with 0 (control, CON), 200 (low-dose TEO, LEO), 400 (medium-dose TEO, MEO), or 600 mg/kg (high-dose TEO, HEO) of TEO in the basal diet. Results showed that lambs receiving TEO exhibited higher average daily gain and improved feed conversion efficiency (P < 0.05). TEO supplementation could delay the decline in postmortem longissimus thoracis (LT) muscle pH (P < 0.05). The MEO group exhibited smaller muscle fiber diameters, lower shear force values, and higher ether extract content and water-holding capacity compared with the CON group (P < 0.05). Lambs fed the TEO diet promotes the deposition of flavor amino acids and unsaturated fatty acids in LT muscle and reduces saturated fatty acid content (P < 0.05). Additionally, supplementation with TEO significantly increased LT muscle catalase activity and reduced malondialdehyde content (P < 0.05). Meanwhile, TEO significantly modified the rumen bacterial composition (P < 0.05). These results suggest that dietary TEO supplementation can improve lambs' performance and meat quality by enhancing muscle oxidative stability and optimizing the rumen bacterial profile, with the medium-dose TEO showing the most favorable effects in this study.