**5. Conclusions**

This study provides new information about the effect of HT supplements in the diet of bulls on growth pattern, carcass and meat quality, and reduction of pathogenic strains of *Clostridia* in feces. It demonstrated that tannins had a significant effect on increasing growth rate when bulls averaged 538 kg BW to slaughter maturity. In addition, tannin supplementation decreased meat drip losses and was very effective in reducing *C. perfringens* in the selective test. Therefore, given the same energy content in the diet of fattening bulls, the addition of HT can affect protein synthesis in the rumen, thereby increasing the availability of amino acids in the amino acid pool for body protein synthesis and consequently ADG. Our research on large ruminants under practical breeding conditions allowed us to approach a statistically balanced experiment. In practice, a cheaper meal with a lower protein content together with the addition of hydrolyzable tannins can increase nutrient utilization efficiency, improve growth intensity, and effectively reduce *Clostridia*l pathogens in bulls without adverse effects on carcass and meat quality. Our results sugges<sup>t</sup> that the addition of hydrolyzable tannins is justified in practice because their activity is effective against pathogenic bacteria and could be very promising in controlling ruminant diseases, reducing antibiotic use, and improving overall welfare of domestic animals. Further research should elucidate the response of the microbiome and the methane reduction potential in bull fattening.

**Author Contributions:** Conceptualization, M.J., M.B. and A.M.; methodology, M.B., M.J., T.K.Š., D.Š. and A.M.; data curation, M.B., T.K.Š. and A.M.; funding acquisition M.J. and M.B.; investigation, A.M., M.J. and M.B.; project administration, M.J. and M.B.; supervision, M.J. and M.B.; writing—original draft A.M., writing—review and ending D.Š., M.B. and M.J. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was funded by Tanin Sevnica d.d. The authors also would like to thank the SLOVENIAN RESEARCH AGENCY for financial support through research grants from the Research Group for Food Safety and Health Assurance, gran<sup>t</sup> number: P1-0164.

**Institutional Review Board Statement:** Feed additives were used in this study (European Union Register of Feed Additives, 2013). No animal procedures were performed, which would require ethics approval according to Directive 2010/63/EU of the European Parliament and of the Council on the protection of animals used for scientific purposes.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available within the article.

**Acknowledgments:** The authors are grateful for the technical support at the farm level. The authors gratefully acknowledge the full support. Meta Candek-Potokar and Andreja Žabjek for their practical ˇ and professional research assistance.

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