**4. Conclusions**

The GP addition to the ruminants' daily diet increased the digestibility of nutrients without the negative effect on the biochemical profile of animals. The digestibility of crude protein, NFC, NDF, and OM in wethers was significantly higher at a higher dose of dried grape pomace (2% of GP). The addition of GP into the daily diet did not affect the nitrogen, enzymatic, mineral, and energetic profile of wethers blood serum except Cl- and glucose (2% of GP). Dried grape pomace in an amount of 2% diet dry matter can be considered as a suitable source of nutrients in sheep feeding, which in addition should improve the digestibility of diet crude protein.

**Author Contributions:** Conceptualization, M.R., D.B. and B.G.; data curation, O.H. and E.M.; formal analysis, M.K.; funding acquisition, B.G.; investigation, M.R., P.V. and R.K.; methodology, M.R. and M.J.; project administration, B.G.; resources, B.G.; software, O.H. and E.M.; supervision, M.Š., P.M. and A.K.; validation, D.B., M.K. and B.G.; visualization, M.J. and M.R.; writing—original draft, M.J., O.H. and E.M.; writing—review and editing, D.B., M.Š. and M.J. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research and APC were funded by the Slovak Research and Development Agency, gran<sup>t</sup> number APVV-16-0170 (by-products from grape processing as a bioactive substance source in animal nutrition).

**Institutional Review Board Statement:** The conditions of animal care, manipulations and use corresponded with the instructions of the Ethics Committee of the Slovak University of Agriculture in Nitra, Protocol No. 48/2013. According to the State Veterinary and Food Administration of the Slovak Republic, the given study is evaluated as inexperienced agricultural practices that do not fall under the legislation of Government Regulation of the Slovak Republic 377/2012 of 14 November 2012, laying down requirements for the protection of animals used for scientific or educational purposes.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.

**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.
