Fertilizing capacity of vitrified epididymal sperm from Iberian ibex (Capra pyrenaica)

Abstract

In this study, we successfully described for the first time a vitrification of epididymal Iberian ibex spermatozoa. Spermatozoa from epididymis were obtained from 15 Iberian ibex. The right epididymis' semen sample was vitrified and the left one was frozen. After thawing/warming, samples were selected by density gradient. Sperm characteristics from each treatment were evaluated. To test the spermatozoa fertilization ability, heterologous IVF was carried out using bovine oocytes. Despite of the observation of a decrease of about 40% for motility sperm between pre-freezing and post-thawing (75.0 ± 5.2 and 45.0 ± 6.0) and pre-vitrification and post-warming (78.2 ± 5.2 and 33.9 ± 6.2) (P < .05), after the washing, an improvement of sperm motility was found when using the vitrification treatment compared to frozen-thawed. Heterologous IVF showed that Iberian Ibex spermatozoa, either frozen-thawed or vitrified-warmed, were equally capable of penetrating ZP intact bovine oocytes, leading to pronuclear formation (%) and hybrid embryo cleavage (%), (31.3 ± 27.2 and 45.1 ± 24.4, respectively). As expected, in the homologous IVF group, higher percentages of penetration, pronuclei formation and cleavage were found compared to heterologous groups using Iberian ibex frozen and vitrified sperm (P < 0,5). The highest pronuclei formation was found after 20 h post insemination in both heterologous IVF groups (30.2 ± 6.7 and 31.7 ± 21.5 thawed and vitrified group). Consequently, the cleavage rate (48 h) followed the same results to homologous and thawed and vitrified groups (76.1 ± 15.9; 31.3 ± 27.2 and 45.1 ± 24.4, respectively) (P < .05). In conclusion, Iberian ibex sperm vitrification is a promising and useful alternative to conventional methods resulting in good quality spermatozoa post-thaw, and an adequate in vitro fertilizing ability.