Effects of Milk Yield, Blood β-Hydroxybutyrate Concentrations, and Parity on Oxidative Stress and Antioxidants in Uterine Flush Fluid During the Early Postpartum Period in Lactating Holstein Friesian Dairy Cows.

The high lactation performance or parity in dairy cows may affect intrauterine oxidative stress (OS) status. This study aimed to investigate the effects of milk yield, blood β-hydroxybutyrate (BHBA) concentrations, and parity on oxidative stress (diacron-reactive oxygen metabolites [d-ROMs]) or antioxidant activity (biological antioxidant potential [BAP]) in the uterine flush fluid of lactating Holstein Friesian dairy cows. Uterine flush fluid samples were collected at 4, 5, 6, and 8 weeks postpartum (n = 43), and d-ROMs and BAP were measured. d-ROMs, BAP, and oxidative stress index (OSI) were investigated in relation to the correlation between milk yield and BHBA concentrations. Cows were classified into primiparous cow groups (P group, n = 11), biparous cow group (B group, n = 5), and the third or more calving groups (M group, n = 27); d-ROMs, BAP, and OSI changes were evaluated across the groups. No significant correlations were noted between milk yield, blood BHBA concentrations, and d-ROMs, BAP, or OSI. The M group exhibited higher d-ROMs and OSI than the P group at 5 weeks, and the M group had a higher OSI than the B group at 6 weeks. Therefore, parity may influence uterine OS and antioxidant activity.