Cryopreservation of feline epididymal spermatozoa from dead and alive animals and its use in assisted reproduction.

Cryopreservation of gametes is an important tool in assisted reproduction programmes; long-term storage of oocytes or spermatozoa is necessary when in vitro fertilization (IVF) or artificial insemination is to be performed at a future date. Cryopreservation of epididymal spermatozoa offers a potential tool for rescuing genetic material from males of endangered populations. The objectives of this work were to: (1) examine sperm motility, viability, abnormality and acrosome integrity of frozen-thawed domestic cat epididymal spermatozoa; and (2) evaluate the same cryopreservation method on wild feline spermatozoa, needed to preserve their genetic resources. Epididymides were collected from 20 domestic cats during routine neutering procedure and from two wild felines at autopsy. The sperm samples, diluted with 4% glycerol/Tris/egg yolk, were loaded into 0.25 ml mini-straws, exposed to nitrogen vapour and stored in liquid nitrogen. After 4 weeks, samples were thawed and re-evaluated. The quality of each fresh and frozen-thawed sperm sample was tested by determining the motility (54.7 +/- 11.3% and 32 +/- 13.1% respectively for cat spermatozoa; 38.3 +/- 18.7% and 21.5 +/- 16.8% respectively for tiger spermatozoa), viability (74.3 +/- 8.6% and 45.2 +/- 9.4% respectively for cat spermatozoa; 42.4 +/- 14.5% and 33.5 +/- 12.9% respectively for wild felid spermatozoa), morphology and acrosomal status. The present study showed that feline epididymal spermatozoa can be frozen in egg-yolk extender with 4.0% glycerol in 0.25 ml straws. The procedure used in the present study for epididymal cat sperm cryopreservation may be applied to bank the genetic resources of wild felid species.