Cryopreservation of Spanish ibex ( Capra pyrenaica) sperm obtained by electroejaculation outside the rutting season

Abstract

The effectiveness of electroejaculation for obtaining Spanish ibex sperm samples for freeze preserving outside the rutting season was evaluated—the aim being to optimise biological resources for the establishment of germplasm banks. The effect of different egg yolk concentrations (6% or 12%, v/v) in diluents of different buffer composition (Tris–citric acid buffer or Tes–Tris buffer) on frozen-thawed samples of the above also investigated. Experiments were undertaken with six ibex males in February–May, and involved four different semen samples from each animal with four combination of extender, respectively: Tes–Tris–glucose (TTG)–6% egg yolk, TTG–12% egg yolk, Tris–citric acid–glucose (TCG)–12% egg yolk, TCG–6% egg yolk. The results show that electroejaculation is a useful way of obtaining sperm samples from Spanish ibex outside the rutting season (i.e., at a time coinciding with plasma testosterone levels of <0.4 ng/ml). According to the results of the eosin–nigrosin staining and the hypo-osmotic swelling test, the freezing–thawing process significantly reduced the viability and membrane integrity of the spermatozoa extended with TTG–6% egg yolk, TTG–12% egg yolk, and TCG–12% egg yolk, but did not affect these variables in spermatozoa extended with TCG–6% egg yolk. Therefore, the use of Tris–citric acid-based extenders containing low concentrations of egg yolk is recommended for cryopreserving Spanish ibex spermatozoa obtained by electroejaculation outside the rutting season.