Influence of injected selenium in dairy bulls on blood and semen selenium, glutathione peroxidase and seminal quality.

Abstract

A 9 month study was conducted to determine the influence of selenium (Se) injections on blood and semen Se and glutathione peroxidase (GSII-Px) levels in bulls that were moderately Se-deficient. The effects of Se injections on semen production and quality were also examined. Five Holstein bulls were assigned to either a Se or no Se treatment based on their pretreatment seminal production and quality characteristics. Three bulls were given i.m. injections of 5, 10, 20, or 40 mg Se as sodium selenite per 90 kg BW at 6, 16, 22, and 28 weeks, respectively, after initiation of the experiment. Two bulls received sham injections at the same times and served as controls. Blood samples were collected weekly from each bull and assayed for GSII-Px and selenium. Semen was collected 3 times weekly from each bull and assayed for GSII-Px activity in the seminal plasma. Thirteen weeks after initiation of the experiment, semen from each bull was analyzed for Se on a weekly basis. Ejaculates from each bull were evaluated for volume, concentration of spermatozoa, percentage of motile spermatozoa, percentage of intact acrosomes and spermatozoal morphology immediately postcollection. Post-thaw semen quality was determined from two ejaculates from each bull per week. Frozen semen was thawed, incubated for 4 h at 37#{176}C, and spermatozoa were evaluated for post-thaw percentage of motile spermatozoa and percentage of intact acrosomes. Selenium injections increased blood Se (P<0.05), blood GSII-Px (P<O.005), semen Se(P<0.06), and seminal plasma GSII-Px (P<0.05). Blood Se and GSFI-Px did not increase until after the 10mg injection. Seminal plasma GSH-Px appeared highly sensitive to changes in Se status since enzyme levels tripled within 48 h following the 5 mg injection. Subsequent increases in seminal plasma GSII-Px were observed with each Se injection. Neither postcollection nor post-thaw semen quality was influenced by Se injections.