Effect of selenium and vitamin E supplementation on blood glutathione peroxidase activity and selenium in moderately exercised horses

Abstract Text:

The objective was to evaluate the effect of selenium (Se, Se-yeast) and vitamin E (E, α-tocopheryl acetate) supplementation on red cell glutathione peroxidase activity (GPx) and Se blood concentrations in moderately exercised horses. Institutional Animal Care and Use Committee of the School of Veterinary Medicine, National University of Mexico approved the experimental procedures. Twenty-four clinically healthy horses (5-15 yr, 450kg BW) of Mexico City’s Police, without physical activity the month prior to this trial, were used. They were individually stabled and randomly allocated in a factorial experiment (2 Se × 2 E levels) with repeated measures. Groups, with 6 experimental units each one, were: LSeLE, HSeLE, LSeHE and HSeHE (LSe, 0.1; HSe, 0.3 mg Se/kg DM and LE, 1.6; HE, 2 IU vitamin E/kg BW; NRC, 2007).  Se and E were given to supplement the deficient daily ration (Se, <2μg; E, 14.4IU by kg DM, respectively). The study lasted 77 days distributed in 3 periods: adaptation (d0 to d32); moderate exercise (d33 to d56) and re-adaptation (d57 to d77). Exercise period consisted of 30 min (5:20:5 min. warm up: gallop: cool down) in 3 consecutive days and 4 days without exercise. At d64, supplementation was stopped. Once a week, jugular blood samples were taken; during the exercise period it was taken 10 min after activity of the third day. Day zero corresponded to baseline measurement of studied variables. GPx was quantified by spectrophotometry (Randox Daytona™) while Se was quantified by hydride generation atomic absorption spectrometry. Data were analyzed by a mixed model (PROC MIXED, SAS 9.1.3) with the design described above. Day, Se, E and their interactions were the fixed effects, while horse nested in treatment was the random effect. Statistical significance was set at P<0.05. Tukey-Kramer’s test was used to compare LSM. The interaction: day×Se×E affected (P<0.05) blood GPx; differences were observed at d35-49 between HSeHE and LSeHE groups (1915.0±65.9 U/L; 1510.1±54.1 ng/mL, respectively). Day and Se affected blood Se (P<0.05). Values from d0-14 were not different (P>0.05) from d63-77 (61.4±2.1 ng/mL). Blood Se increased at d28 (210.8±7.0 ng/L), and decreased again at d35 (118.38±7.0 ng/L). In general, Se was higher in HSe (97.5±3.8 ng/mL) than in LSe horses (82.01±3.8 ng/mL). Conclusion: supplementation levels of both Se and E affect blood GPx and Se, and are closely related to physical activity.

Keywords: selenium, alpha-tocopheryl, glutathione-peroxidase