Changes in Antioxidant Enzyme Activities and Metabolic Parameters in Dairy Cows during different reproductive periods

Abstract Our study aimed to monitor the alterations in antioxidant enzyme activities and the metabolic profile parameters and their relationships in dairy cows during different reproductive stages (gestational-, dry-, pre- and post-partum). The collection of blood samples from thirty healthy pregnant Holstein cows took place at a commercial dairy farm, between September 2015 and June 2016. The cows covered eight different reproductive stages (4-6 weeks before the dry period (D4-6w)), at the beginning of the dry period (D0; on day 210 of gestation), the first month of the dry period (D1m), antepartum day 8 (APd8), postpartum (PP) day 3 (PPd3), PP day 8 (PPd8), PP between 3rd-4th weeks (PP3-4w) and PP between 80-90 days (PP80-90d). The activities of glutathione peroxidase (GPx) and superoxide dismutase (SOD) were analysed to monitor and evaluate the antioxidant system. Concentrations of beta-hydroxybutyrate (BHBA), non-esterified fatty acids (NEFA), albumin, glucose, total bilirubin, cholesterol, calcium (Ca) and the enzyme activities of aspartate aminotransferase (AST), glutamate dehydrogenase (GLDH), gamma-glutamyl transferase (GGT) were also determined as metabolic profile parameters. GPx activities increased in D1m (P