Effect of Feeding Synthetic Antioxidants and Prepartum Evaporative Cooling on Performance of Periparturient Holstein Cows During Summer in Florida

ABSTRACT: The objective of this study was to evaluate the effect of supplementation with 0 or 250 mg of synthetic antioxidants (AO, Agrado Plus, Novus International, MO) per kg of dietary DM and prepartum evaporative cooling on periparturient Holstein cows (n = 35) from 21 days before through 49 days after parturition in a 2 by 2 factorial design. Uterine health was evaluated via metricheck at 7, 16, and 25 days in milk (DIM). Blood was collected at -15, 1, 8, 15, and 29 DIM for oxidative markers. Phagocytosis and oxidative burst of neutrophils were measured in whole blood collected at -15, 0, 7, and 14 DIM. Acute-phase proteins were measured in plasma collected three times weekly. A uterine horn was flushed at 40 ± 2 DIM for diagnosis of subclinical endometritis. Rectal temperature of cooled cows was lower prepartum (39.2 vs. 39.6°C). Prepartum cooling resulted in greater mean concentration of milk fat during 7 wk (3.54 vs. 3.32 ...) and mean production of 3.5 ... FCM during the first 4 wk postpartum (26.5 vs. 23.0 kg/d). Cooling reduced the concentration of circulating WBC postpartum (7864 vs. 10,199 per ... L of blood) and of circulating lymphocytes (3463 vs. 5432 per ... L of blood) and increased proportion of neutrophils undergoing oxidative burst (83 vs. 77 ...) isolated from cows fed the control diet. Prepartum cooling of multiparous cows resulted in less oxidative stress as evidenced by lower activity of GPx in RBC (8,854 vs. 12,247 nmol/min/mL) and of SOD in RBC (2503 vs. 3111 U/mL).