Antioxidant effect of aqueous and alcoholic extracts of olive leaves on performance, quality characteristics of eggs, biochemical blood, and immune response of laying hens.

Olive leaf extract (OLE) can be used as a rich source of antioxidants due to its polyphenol compounds. The purpose of this research was to measure the antioxidant activity and the effect of aqueous (AOLE) and alcoholic (HOLE) extracts of olive leaves on performance, quality characteristics of eggs, biochemical blood serum, hematology, and immune response of laying hens. This experiment was conducted with 440 high-line laying hens (25 weeks old) in the form of 11 experimental treatments, with 5 replications and each replication including 8 hens for three periods of 28 days in a completely randomized design with five levels of AOLE (200, 400, 600, 800 and 1000 mg/kg) and five levels of HOLE (200, 400, 600, 800 and 1000 mg/kg). The DPPH method was used to measure the antioxidant activity of the extract. Functional traits were measured periodically. Blood was taken from the wing vein for serum biochemical and hematological analysis. Injection of the Newcastle vaccine was performed on the 40th day of the experiment, and blood was taken from the wing vein seven days later. The results showed that birds receiving 1000 levels of AOLE and HOLE had the highest percentage of production compared to the control treatment. The highest number of white blood cells and heterophils and antibody titers against Newcastle virus were observed in birds treated with 1000 HOLE levels. In general, the use of 1000 mg/kg of aqueous and alcoholic extract of olive leaves improves the performance and quality of laying eggs.