SAFETY, EFFICACY, AND EFFECTS ON COPPER-METABOLISM OF INTRARETICULARLY PLACED SELENIUM BOLUSES IN BEEF HEIFER CALVES

Intrareticularly placed sustained-release selenium boluses were administered to 1 group of selenium deficient heifer calves (n = 16), and a second group (n = 16) was left as nontreated controls, Age range for all calves was 83 to 156 days. These boluses release 3 mg of selenium each day, as sodium selenite. Measurements of blood selenium concentration, plasma copper concentration, hepatic copper concentration, and body weight were made over a 188 day study. The treated group of calves had significantly higher mean blood selenium concentration at posttreatment days 68 (P < 0.0001), 112 (P < 0.0001), and 188 (P < 0.005) than did the control group. Mean blood selenium concentration in the treated calves was > 0.10 mu g/ml for 188 days. These boluses were observed to be clinically safe; signs of selenium toxicosis were not detected and untoward effects were not seen in the selenium-treated calves. There were no differences between control and treatment groups with respect to mean hepatic copper concentration or mean plasma copper concentration. There were no observed differences between the control and treatment groups with respect to weight gain during the study.