**5. Conclusions**

The results of this study indicate that dietary supplementation with HM reduces dry matter digestibility (linear effect). However, the inclusion of up to 3 g HM kg−<sup>1</sup> DM does not affect productive performance, carcass characteristics, chemical composition, and meat colouration (lightness and redness) of lambs fed high concentrate diets during the final fattening period. Meat yellowness decreases (linear effect) in response to HM supplementation in the diet, which could be positive because consumers, in general, do not expect to find high yellowness in fresh meat. On the other hand, meat pH, cooking loss and drip loss increase linearly as the dose of HM in the diet increases (linear effect). In addition, Warner-Bratzler shear force decreases as the dose of HM increases (linear effect). Thus, Peptasan® HM could be used to improve meat tenderness of lambs fed high concentrate diets. However, this result must be carefully interpreted considering the low number of replicates used. In addition, the increased drip loss in response to HM supplementation could be a risk of microbial spoilage during meat storage. Therefore, it is convenient to carry out meat quality analyses at the muscle level to evaluate the impact of other doses of this HM in rations with different proportion of concentrate for lambs in different experimental periods and physiological stages.

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

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Animal care and handling procedures were conducted according to the technical specifications for the production, care and use of laboratory animals established in the Official Mexican Standard (NOM-062-ZOO-1995). The approval for this study was granted prior to commencement of the work by, Comisión Académica del Doctorado en Ciencias Agropecuarias de la Universidad Autónoma Metropolitana, Unidad Xochimilco.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The datasets used and analyzed during the current study are available from the corresponding author on reasonable request.

**Acknowledgments:** The first author, José Felipe Orzuna Orzuna is a Master of Science student of the Program of Animal Production of the Universidad Autónoma Chapingo and thanks the CONACyT Program for the scholarship. We appreciate the assistance of Nuproxa México S. de RL. de CV. Querétaro, México for providing the Herbal Plant Additive.

**Conflicts of Interest:** The authors declare no conflict of interest.
