Effects of dietary supplementation of Macleaya cordata extract on inflammatory and oxidative status, liver function and milk yield in dairy cattle during the transition period.

Immune function and oxidative stress are crucial during the transition period (TP) in dairy cattle, influencing their metabolic adaptation to the new lactation. The supplementation with Macleaya cordata, an herb known for its anti-inflammatory, antibacterial, and antioxidant properties, may influence these processes. This study aimed to evaluate the effects of Macleaya cordata extract (MCE) on inflammatory and oxidative status and liver function during the TP, as well as on subsequent early lactation. On day 24 (± 3) before the expected calving date, sixty-four cows were randomly assigned to two groups: the MCE group (MCEG), which received a controlled-release oral bolus delivering 1.5 g of MCE daily for 70 days, and the control group (CG), in which bolus placement was simulated using a balling gun. Blood samples were collected at three time points: 24 days before calving, 7 and 21 days postpartum. Biomarkers of oxidative status, inflammation, energy balance and liver function were measured in plasma samples. A significant interaction effect (supplementation × time) was observed for milk yield (P < 0.05), with higher values in MCEG (51.3 ± 1.1 kg/day) than in CG (46.5 ± 1.1 kg/day) on days 25 postpartum. No significant differences were observed in body condition score, non-esterified fatty acids and beta-hydroxybutyrate concentrations. However, an interaction effect was observed for glucose concentrations (P < 0.05), with higher values in the MCEG on day 7 postpartum. Liver function biomarkers showed no significant differences between groups. Plasma 3-nitrotyrosine and serum interleukin-1 concentrations were lower in the MCEG (P < 0.05). These findings suggest that MCE supplementation may enhance milk production, potentially associated, among other mechanisms, with improvements in inflammatory and oxidative status in dairy cows.