Resumen

CHIHUAILAF VIVANCO, Ricardo Hugo; WITTWER MENGE, Fernando Germán  y  CONTRERAS BARRIGA, Pedro Alberto. Variations of the Erythrocyte Osmotic Fragility in Cattle Grazing on Pastures with Low Selenium Content with or Without Supplement with Selenium. Rev. Cient. (Maracaibo) [online]. 2006, vol.16, n.3, pp.227-231. ISSN 0798-2259.

Selenium is a part of antioxidant enzyme glutathione peroxidase (GSH-Px; E.C.1.11.1.9). In cattle, the selenium deficiency has been associated with decreased activity of glutathione peroxidase leading to an increase in oxidative damage of cells. The oxidative stress in erythrocytes from cows can be estimated by erythrocyte osmotic fragility test (EOF). To assess EOF as biomarker of oxidative stress in cattle grazing on pastures with low selenium content during different seasons of the year, two groups of sixteen heifers each were used. They were grazed on pastures with 0.04 ppm selenium content. In March one group (Se+) was supplemented with selenium (Deposel^®) and another (Se-) was maintained unsupplemented. Blood samples were obtained from each heifer prior to supplementation and then one time each month for ten months. The EOF was determined using a technique described by Schalm. The GSH-Px activity was measured using a commercial kit (Ransel^®). The GSH-Px activity was increased by selenium supplementation to adequate levels (> 130 U/g Hb). The GSH-Px activity in Se- group was 60-100 U/g Hb. No differences between groups were detected in the EOF values, at 0.55% NaCl concentration; however, both groups showed decreased EOF values after September, coincident with the spring season in the southern hemisphere. Seemingly in this period, the more rapidly growing pasture grass increased in levels of some others factors that lead to increased protection against oxidative damage to erythrocytes.

Palabras clave : Erythrocyte osmotic fragility; oxidative stress; selenium; cattle.