Feed supplemented with byproducts from olive oil mill wastewater processing increases antioxidant capacity in broiler chickens

•A ceramic membrane microfiltration method was used for the separation of two products from olive mill wastewater (OMWW).•These two products were examined for their antioxidant activity in vivo by incorporating them into broilers' feed.•Broilers' feed supplemented with OMWW products reduced protein oxidation and lipid peroxidation in plasma and tissues.•Broilers' feed supplemented with OMWW products increased catalase activity and GSH levels in erythrocytes and tissues.•Broilers' feed supplemented with OMWW products increased total antioxidant capacity in plasma and tissues. In the present study, a ceramic membrane microfiltration method was used for the separation of two liquid products, the downstream permeate and the upstream retentate, from olive mill wastewater (OMWW). These liquid products were examined for their antioxidant activity by incorporating them into broilers' feed. Twenty four broilers 13 d old were divided into two feeding groups receiving supplementation with OMWW retentate or permeate for 37 d. Blood was drawn at 17, 27 and 37 d, while tissues (muscle, heart, liver) were collected at 37 d. The antioxidant effects were assessed by measuring oxidative stress biomarkers in blood and tissues. The results showed that broilers given feed supplemented with OMWW retentate or permeate had significantly lower protein oxidation and lipid peroxidation levels and higher total antioxidant capacity in plasma and tissues compared to control group. In both OMWW groups, catalase activity in erythrocytes and tissues was significantly increased compared to control group. OMWW retentate administration increased significantly GSH in erythrocytes in broilers with low GSH, although both OMWW products significantly reduced GSH in broilers with high GSH. Thus, it has been demonstrated for the first time that supplementation with OMWW processing residues could be used for enhancing broilers' redox status.