**5. Conclusions**

This study demonstrated that the dietary inclusion of 0.3 g (per kg of DM) of OEO increases lamb tenderness and, similarly to monensin and low oregano oil (0.1 g/kg DM) supplementation, it preserves the meat colour after 7 d of storage. Thus, oregano oil could be an alternative to monensin in lamb diets. The supplementation of oregano essential oil also significantly a ffected the fatty acid profile, increasing the content of C16:1n7, C18:1n9c, C20:1n9, and C18:2n6 in meat. This study demonstrated that oregano essential oil was beneficial for lamb meat quality. Overall, this study confirmed the remarkable beneficial e ffect of oregano essential oil on the colour, tenderness, lipid oxidation, and fatty acid profile of lamb meat, which is of significant importance, aiming to evaluate the benefits of phytochemicals to replace monensin and obtaining advantages in lamb meat quality. Further research is needed to identify the main metabolic pathway of oregano essential oil as well as the crucial active components that favourably alter the quality characteristics in lamb meat.

**Author Contributions:** Conceptualization, I.A.G.-G. and A.D.A.-R.; methodology, I.A.G.-G., J.A.A.-A., A.L.R.-M.; formal analysis, I.A.G.-G., M.H.-J., and L.M.C.-L.; investigation, J.A.A.-A. and J.L.L.-O.; resources, A.D.A.-R.; writing—original draft preparation, I.A.G.-G., A.L.R.-M., J.L.L.-O. and A.D.A.-R.; writing—review and editing, M.H.-J., and J.M.T.-G.; project administration, I.A.G.-G.; funding acquisition, I.A.G.-G. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by PROMEP, SEP; clave UACH-PTC-216.

**Acknowledgments:** The authors would like to thank Guillermo Villalobos for providing the meat and the information from his research on oregano essential oils supplementation on performance and digestibility of sheep.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
