Effect of Intramuscular Administration of Selenium and Vitamin E in Dairy Heifers on Erythrocyte Glutathione Peroxidase Activity and Blood Selenium Levels

Abstract

Two experiments were conducted to examine the response of red blood cell (RBC) glutathione peroxidase (GSH-Px) following a single injection of selenium and vitamin E and to determine the value of this enzyme as an indicator of both pre-and post-treatment selenium status in dairy cattle. In Experiment 1, five Holstein heifers were given an intramuscular injection of 5 mg selenium as sodium selenite and 68 IU vitamin E per 60 kg of body weight and five heifers were left untreated. Blood samples, taken at 2-week intervals for 14 weeks, were assayed for RBC GSH-Px activity to determine if a single injection of selenium would produce a measurable change. In Experiment 2, five heifers were assigned randomly to each of two treatment groups and injected as in Experiment 1. Blood samples, drawn at 10-day intervals for 30 days, were assayed for both RBC GSH-Px and whole blood selenium. Heifers in both experiments had been maintained on a low-selenium (<.02 ppm Se) all-forage diet and had relatively low initial levels of RBC GSH-Px activity. In Experiment 1, RBC GSH-Px activity of the treated heifers increased 16% (P<.05), reaching 23.0±2.6 enzyme units/mg hemoglobin 4 weeks post-treatment. Meanwhile, enzyme levels for the untreated heifers had decreased 10%. This decline in activity was linear (P<.01) over the 14-week observation period. Enzyme activity in the treated heifers had returned to a level equivalent to that of the untreated heifers by 12 to 14 weeks post-treatment. In Experiment 2, RBC GSH-Px activity of treated heifers increased (P<.01) more dramatically, reaching 167% (24.4 ± 3.0 enzyme units/mg hemoglobin) of initial levels by 30 days post-treatment while whole blood selenium concentrations increased (P<.05) from .016 µg/ml pre-treatment to an average of .043 µg/ml from day 10 through 30. Copyright © 1978. American Society of Animal Science . Copyright 1978 by American Society of Animal Science.