Supplementation with increasing doses of selenium associated with vitamin E in the treatment of bovines with enzootic hematuria

Abstract

Bovine enzootic hematuria (BEH) is a clinical form of poisoning in cattle caused by the consumption of Pteridium spp. (bracken fern), which has no treatment. However, selenium (Se) and vitamin E supplementation are feasible. The aim of this study was to evaluate the effects of supplementation with increasing doses of selenium associated with vitamin E in cattle with BEH, compare the levels of Se in whole blood and blood serum, and evaluate the activity of glutathione peroxidase, total antioxidants, and the relative activity of the enzyme monoamine oxidase (MAO). Four groups of cattle with BEH were supplemented parenterally for 13 weeks with increasing doses of Se: Control group, Treatment group 1 (0.05mg/kg), Treatment group 2 (0.1mg/kg), and Treatment group 3 (0.2mg/kg). All groups received 500mg of vitamin E in combination with the Se supplementation. The measured variables included weight, hematuria intensity, hematocrit, total plasma protein, plasma fibrinogen, blood glutathione peroxidase activity, and total antioxidant levels. The blood concentrations of Se and relative MAO activity were evaluated every two weeks. Kruskal-Wallis and Friedman tests (P<0.05) were used to assess treatment and time effects, respectively, followed by Dunn’s multiple comparison test. For weight, total antioxidant concentration, and relative MAO, there was no significant difference (P>0.05) between the treatments, but there was a significant difference over time (P<0.05). For hematuria and hematocrit, there were significant treatment differences (P<0.05) but no significant time differences (P>0.05). For glutathione peroxidase, there was no significant difference (P>0.05) among the treatments, but there was a significant difference (P<0.05) between treatments M8 and M14 in Treatment group 3. There were no differences in the total plasma protein and fibrinogen levels between treatments or over time (P>0.05). Selenium levels were higher in Treatment group 1, reaching the highest concentration (235.3µg/L) in the blood serum at eight weeks. Therefore, supplementation with Se at a dose of 0.05mg/kg associated with vitamin E improved the clinical condition of hematuria but did not interfere with glutathione peroxidase activity or with levels of total antioxidants. MAO activity was reduced by vitamin E supplementation. These results indicate that the serum is the best site for measuring Se levels.