Effect of Dietary Selenium and Vitamin E Supplementation on Testicular Morphology and Serum Testosterone Concentration in Goats Following Scrotal Insulation

Abstract

Background: Heat directly applied to the testis has been providing information regarding the damage triggering mechanisms on spermatogenesis and possible treatments to prevent testicular changes. Testis submitted to heat-shock have inhibition of the local antioxidant defense mechanisms against lipid peroxidation and free radicals. Vitamin E and Selenium protect biological membranes against free radicals to prevent membrane lipid peroxidation. The current assay evaluated the effect of dietary supplementation with Selenium and Vitamin E on testicular parenchyma and testosterone levels of goats submitted to heat shock by scrotal insulation.

Materials, Methods & Results: The effect of dietary selenium and vitamin E supplementation on testicular parameters and serum testosterone concentration was evaluated in goats subjected to scrotal insulation. The animals were randomly allocated into two groups (n = 6) to receive either a control diet (CO) or a diet supplemented with selenium and vitamin E (SE). The animals received supplementation for 120 days: 60 days prior to scrotal insulation, 18 days during scrotal insulation and 42 days after scrotal insulation. Orchiectomy was performed on three animals from each group, immediately after the end of scrotal insulation. The remaining animals were neutered at the end of the experimental period (120 days). Testicles were routinely processed and embedded in glycol methacrylate, stained with toluidine blue/1% sodium borate and evaluated qualitative and quantitatively. Serum testosterone concentrations were determined by enzyme immunoassay at the time of the orchiectomy. Scrotal circumference was greater (P < 0.05) in goats of the SE group (23.0 ± 1.00 cm) than those of the control group (20.0 ± 1.00 cm) at the end of the scrotal insulation period (Day 18).  At the end of the experimental period (Day 42 post-scrotal insulation (PSI)), the seminiferous tubule diameter and seminiferous epithelium height were greater (P < 0.05) in the SE group than in control. Histological changes associated with testicular degeneration were detected after 18 days of scrotal insulation in the goats of the control group. The animals of SE group had some histological changes of seminiferous tubules but the majority of them had normal association of germ cells. Selenium and vitamin E supplementation did not seem to avoid testicular damage caused by scrotal insulation but accelerated testicular recovery after the removal of insulation. Testosterone serum levels were not changed in the animals submitted to scrotal insulation, with or without dietary supplementation with selenium and vitamin E.

Discussion: In the current study, scrotal insulation for 18 days caused testicular degeneration in both groups. However, selenium and vitamin E supplementation were capable of maintaining the scrotal circumference on the 18th day of insulation in the SE group. Previous reports suggested that selenium and vitamin E could protect cell membranes against the harmful effects of reactive oxygen species. However, the histopathological changes and morphometric data observed in the both groups after 18 days of insulation demonstrated that supplementation with these antioxidants did not prevent the damage caused by heat stress.  In turn, at 42 days after the removal of insulation, the tubular diameter and seminiferous epithelium height was greater in animals supplemented with selenium and vitamin E. In addition, the animals that received supplementation had most of seminiferous tubules with cell associations of the seminiferous epithelium cycle. Vitamin E and selenium may reduce testicle sensitivity to heat and thereby shorten the spermatogenesis recovery time by 10 to 20 days. Selenium plus vitamin E added to feed was unable to prevent the degeneration of the testicular parenchyma in these animals. Nonetheless, the supplementation with both antioxidants hastened the recovery of spermatogenesis after the thermal injury.