BACKGROUND/AIMOlive mill wastewater (OMW) is a byproduct of olive oil production. The aim of the study was to estimate the redox profile of lambs' vital organs after consumption of an OMW-supplemented feed. MATERIALS AND METHODSTwenty-four lambs received breast milk until day 15. Then, they were divided in two groups: control and OMW, n=12 each. The control group received standard ration, while the OMW group received OMW enriched feed along with mother's milk until day 42 and animals (n=6 per group) were sacrificed. The remaining 12 received the feeds until day 70 and sacrificed. Tissue samples were collected at day 42 and 70 and specific redox biomarkers were assessed. RESULTSOverall, the OMW feed improved tissue redox profile by affecting the glutathione S-transferase (GST) activity and γ-glutamate-cysteine ligase (γ-GCL) expression in all tested tissues. Superoxide dismutase (SOD) activity was not affected. CONCLUSIONThe polyphenol-rich byproduct reinforced lamb redox profile and may putatively improve their wellness and productivity.