**5. Conclusions**

We can conclude that organic Zn sources, zinc chelate of glycine hydrate, and zinc chelate of protein hydrolysate, given adequate levels of dietary Zn, were absorbed and utilized in a similar way as inorganic Zn feed additive zinc sulphate in growing lambs, and Zn supplementation increased antioxidant status in the pancreas regardless of Zn source. Relative bioavailability of zinc did not differ among the Zn feed additives; however, the effect of Zn from organic sources on mineral deposition and antioxidant status may differ slightly in lambs. Further research is needed in order to elucidate the differences in post-absorptive metabolism of Zn from organic sources.

Similarities in bioavailability of Zn sources indicate that the lambs' Zn requirements were met (33 mg Zn/kg of DM), regardless of Zn supplemental source. However, feed supplementation with Zn from the inorganic and organic sources at 80 mg of Zn/kg of complete feedstuffs might improve the antioxidant status of growing ruminants without any effect on the growth performance.

**Supplementary Materials:** The following are available online at https://www.mdpi.com/article/ 10.3390/agriculture11111093/s1, Table S1. Trace mineral concentrations in plasma after 30, 60 and 90 days of Zn supplementation (80 mg Zn/kg).

**Author Contributions:** Conceptualization, L'.G. and K.C.; methodology, L'.G. and K. ˇ C.; validation, ˇ L'.G. and K.C.; formal analysis, L'.G., K.T. and K. ˇ C.; investigation, L'.G. and K. ˇ C.; data curation, L'.G. ˇ and K.C.; writing—original draft preparation, L'.G.; writing—review and editing, L'.G. and K. ˇ C.; ˇ project administration, L'.G. and K.C.; funding acquisition, K. ˇ C. All authors have read and agreed to ˇ the published version of the manuscript.

**Funding:** This research was funded the Slovak Research and Development Support Agency APVV (grant number: 17-0297) and by the Slovak Grant Agency VEGA (grant number: 2/0008/21).

**Institutional Review Board Statement:** This study was conducted according to the guidelines of European Union Directive 2010/63/EU for animal experiments and approved by the Ethics Committee of the Institute of Animal Physiology of the Slovak Academy of Sciences and by the State Veterinary and Food Office (Ro-4160/13-221, 2.12.2013).

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The datasets used and analyzed in this survey are available from the corresponding authors upon reasonable request.

**Acknowledgments:** We thank Andrew Billingham for providing language support that greatly improved the manuscript. Thanks go to Renata Gerocova for their excellent assistance in data collection.

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