Extender osmolality, glycerol and egg yolk on the cryopreservation of epididymal spermatozoa for gamete banking of the Cantabric Chamois (Rupicapra pyrenaica parva)

Abstract

Germplasm banking is a key technology enabling the ex-situ conservation of wild species. However, cryopreservation protocols must be tested to assure the applicability of the banked material. The objective of this study was defining a range of parameters for the composition of a semen extender for Cantabrian chamois epididymal spermatozoa (post-mortem collection). The freezing extender was based in a TES-Tris-fructose buffer, modifying its composition in three experiments: Osmolality of the buffer (320, 380 or 430 mOsm/ kg, 8% glycerol, 15% egg yolk), glycerol (4 or 8%, 430 mOsm/kg, 15% egg yolk), egg yolk (10 or 15%, 430 mOsm/kg, 4% glycerol). Sperm was extended at 100 mill. spermatozoa/ml, cooled at 5°C and frozen at −20°C/min. Sperm quality was assessed pre and post-thawing (CASA, HOS test, abnormal forms, cytoplasmic droplets, and viability and acrosomal damage by flow cytometry). Freezability was good overall, with total motility of 65.5% ± 2.4 initial and 55.8% ± 2.4 post-thawing. The extenders affected the post-thaw sperm quality marginally. Whereas osmolalities and glycerol concentrations seemed not to differ, 430 mOsm/kg and 4% glycerol might be preferred. Egg yolk concentrations only differed on sperm velocity (VCL: 84.0 ± 6.7 μm/ s in 10% vs. 70.7 ± 6.2 μm/s in 15%, P < 0.05). Our results suggest a good cryotolerance of chamois epididymal spermatozoa, with a preferred extender composition of hyperosmotic buffer, glycerol in the 4% range and lower egg yolk (10% range) than other ruminants.

Practical Method for Freezing Buck Semen

“…The bucks in our study were of known fertility in natural mating and post-thaw sperm motility was considered to be acceptable; therefore, we have no reason to suppose that the spermatozoa would not be fertile when used in AI [18]. However, one of the problems with semen banking is that the fertilizing capability of the sperm samples is not known until the samples are inseminated [19].…”

Recent Progress in Spermatology Contributing to the Knowledge and Conservation of Rare and Endangered Species

“…This is true for species as different as amphibians and carnivores (17,18). Testicular or epididymal sperm can also be collected and studied opportunistically in mammals and nonmammals by rescuing testicular and epididymal tissues postmortem (19,20). Sperm cells tend to be easier to collect than oocytes and usually represent the first attempts when studying gamete biology in a new species.…”