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

Intrareticularly placed sustained-release selenium boluses were admini stered to 1 group of selenium deficient heifer calves (n = 16), and a second group (n = 16) was left as nontreated controls, Age range for a ll calves was 83 to 156 days. These boluses release 3 mg of selenium e ach day, as sodium selenite. Measurements of blood selenium concentrat ion, plasma copper concentration, hepatic copper concentration, and bo dy weight were made over a 188 day study. The treated group of calves had significantly higher mean blood selenium concentration at posttrea tment 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 treat ed 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. The re were no differences between control and treatment groups with respe ct to mean hepatic copper concentration or mean plasma copper concentr ation. There were no observed differences between the control and trea tment groups with respect to weight gain during the study.