Effect of supplementing periparturient cows with vitamin E on distribution of alpha-tocopherol in blood.

Holstein cows were fed 0 or 1000 IU/d of supplemental vitamin E during the dry period and injected with placebo or 3000 IU of vitamin E at 10 and 5 d prior to anticipated calving. Blood was collected at various times, starting at 60 d prepartum (dry off) and concluding 30 d postpartum, and separated into plasma, red blood cells, and neutrophils. Oral supplementation increased concentrations of alpha-tocopherol in plasma and red blood cells on 10 d, but not on 5 d prepartum. Injection of vitamin E increased alpha-tocopherol in plasma, red blood cells, and neutrophils at d 5 prior to and on the day of parturition. Concentrations of alpha-tocopherol and cholesterol in plasma were correlated, and both were at their nadir at parturition. Concentrations of alpha-tocopherol in plasma and red blood cells were correlated, but the correlation increased when plasma alpha-tocopherol was expressed per unit of cholesterol. alpha-Tocopherol in plasma and neutrophils had a low correlation. Injection of alpha-tocopherol increased its concentration in plasma, red blood cells, and neutrophils during the periparturient period. Concentration of alpha-tocopherol in plasma of periparturient cows may be limited by its low lipid content, and transport mechanisms for alpha-tocopherol may differ between red blood cells and neutrophils.