Effects of Nano Zinc Oxide Supplementation on Oxidative Stress and Selected Metabolic Parameters During the Transition Period in Lacaune Ewes

BACKGROUND: The transition period in small ruminants is characterized by marked metabolic and oxidative changes. Nano zinc oxide (nZnO) has potential antioxidant-related properties, but its effects in dairy-type ewes remain unclear. OBJECTIVES: This study evaluated the effects of nZnO supplementation on oxidative stress and selected metabolic parameters in pregnant Lacaune ewes during the transition period. METHODS: Fourteen clinically healthy pregnant ewes were randomly assigned to a control group or an nZnO group (25 mg/kg body weight). Blood samples were collected 21 days before lambing, within 1-12 h after lambing and 21 days postpartum. Serum total antioxidant status (TAS), total oxidant status (TOS), oxidative stress index (OSI) and selected biochemical variables were measured. Data were analysed using a linear mixed model for repeated measures. RESULTS: No significant effects of treatment, time or treatment × time interaction were detected for TAS, TOS or OSI (p > 0.05), although non-significant numerical differences were observed. Significant effects of time were observed for albumin (p = 0.006), ALT, AST, BUN, total calcium, total protein and triglycerides (all p < 0.001). Treatment effects were detected for BHBA (p = 0.009), phosphorus (p = 0.035) and total cholesterol (p = 0.035), and total cholesterol also showed a treatment × time interaction (p = 0.033). No significant effects were detected for NEFA. CONCLUSIONS: At the tested dose, nZnO did not significantly alter oxidative stress indices. The effects on selected metabolic variables should be interpreted cautiously because of the small sample size and lack of zinc status assessment. Larger multi-dose studies are needed before practical recommendations can be made.