*Article* **Bioavailability of Dietary Zinc Sources and Their Effect on Mineral and Antioxidant Status in Lambs**

**L'ubomíra Grešáková \*, Katarína Tokarˇcíková and Klaudia Cobanov ˇ á**

> Institute of Animal Physiology, Centre of Biosciences of the Slovak Academy of Sciences, Šoltésovej 4, 040 01 Košice, Slovakia; tokarcikova@saske.sk (K.T.); boldik@saske.sk (K.C.) ˇ **\***

 Correspondence: gresakl@saske.sk; Tel.: +421-557922970

**Abstract:** This study investigated the relative bioavailability (RBV) of zinc from different sources used as feed additives in ruminant nutrition based on Zn concentration and the activity of Zn-dependent enzymes in lamb tissues. Thirty-two male lambs of Improved Valachian breed (three months old) were randomly assigned to four dietary treatments. For 120 days, the lambs were fed either the total mix ration (TMR) providing 29.6 mg Zn/kg or the TMR supplemented with either zinc sulphate (ZnSO4), zinc chelate of glycine hydrate (ZnGly), or zinc chelate of protein hydrolysate (ZnProt). The supplemented diets contained a total of 80 mg Zn/kg. Supplementation with ZnSO4 increased Zn concentration in the liver, while the highest Zn uptake was in the kidneys of lambs fed the ZnProt diet. The ZnGly supplemented diet elevated the activity of the Cu/Zn-dependent enzyme superoxide dismutase (Cu/Zn SOD) in the liver. Regardless of Zn source, Zn supplementation resulted in increased total antioxidant status (TAS) in the pancreas. The estimated RBV of Zn based on linear regression slope ratios did not differ among the Zn sources. Our results indicate similar availability of Zn from organic dietary sources as from commonly used zinc sulphate; however, their effects on mineral and antioxidant status may differ slightly in growing lambs.

**Keywords:** feed additives; trace minerals; bioavailability; lambs; antioxidant enzymes
