Plant extracts supplied to pre-weaned dairy calves influence their redox status

This study aimed to evaluate the effects of the separate provision of green and oregano tea extracts on the biomarkers of the redox state and health condition in pre-weaned Jersey calves from birth to 60 days of life. Two experiments following the complete randomized design with measures repeated in time were carried out using 38 Jersey calves (17 and 21 calves in experiments 1 and 2, respectively). Calves were distributed according to date of birth into one of three groups: control (CON) - with no addition of extracts; oregano extract (OE) - addition of 70 mg of oregano extract/kg of body weight (BW) and green tea extract (GT) - addition of 35 mg of green tea extract/kg of BW. Eight biomarkers of the redox state were evaluated on days 1, 30, and 60 after birth, and variables measured on day 1 were used as covariates. Body temperature and occurrence of diarrhea were evaluated every two days. Regarding the main results, the supply of oregano extract reduced the concentration of oxidizing biomarkers, such as DCFP (oxidation of dichlorofluorescein in plasma) and carbonyl, and increased the activity of antioxidant enzymes, such as GPx and catalase. Green tea extract only reduced DCFP and tended to improve catalase activity. Calves remained healthy (no fever and only a few days with diarrhea), and plant extracts did not improve their health condition. The addition of green tea and oregano extracts into the diet has a positive effect on redox status in pre-weaned Jersey calves.