EFFECT OF VITAMIN-E SUPPLEMENTATION IN DIETS WITH A LOW CONCENTRATIONOF SELENIUM ON MAMMARY-GLAND HEALTH OF DAIRY-COWS

Sixty-six cows and heifers (Holsteins and Jerseys) were assigned to on e of three treatments at 60 d before anticipated calving. Treatment I consisted of 100 IU/d of supplemental vitamin E during the dry period and 100 IU/d during the first 30 d of lactation. Treatment 2 was 1000 IU/d of vitamin E during the dry period and 500 IU/d during lactation. Treatment 3 was 1000 IU/d of vitamin E during the first 46 d of the d ry period, 4000 IU/d during the last 14 d of the dry period, and 2000 IU/d during lactation. Plasma concentrations of alpha-tocopherol decre ased at calving for cows fed dietary treatments with low or intermedia te concentrations of vitamin E, but not for cows fed the high vitamin E treatment. High dietary vitamin E increased concentrations of alpha- tocopherol in blood neutrophils at parturition, but no difference was found for the other two treatments. The percentage of quarters with ne w infections at calving was not different (32.0%) between cows receivi ng treatments that contained low and intermediate concentrations of vi tamin E but was reduced (11.8%) in cows receiving the high vitamin E t reatment. Clinical mastitis affected 25.0, 16.7, and 2.6% of quarters during the first 7 d of lactation for cows receiving the low, intermed iate, and high vitamin E treatments, respectively. Cows with, plasma c oncentrations of alpha-tocopherol <3.0 mu g/ml at calving were 9.4 tim es more likely to have clinical mastitis during the first 7 d of lacta tion than were cows with plasma concentrations of alpha-tocopherol >3. 0 mu g/ml.