Reproductive technologies for conservation of genetic resources of endangered equidae: A review

Abstract

This review presents data on the use of assisted reproductive techniques to obtain offspring and preserve the ge-netic resources of wild Equidae including the Przewalski’s horse Equus ferus przewalskii. Some results and ap-plied techniques in obtaining and cryopreservation of sperm, embryo transfer, including interspecies, as well as the possibility of studying and regulation of the oestrous cycle in rare and endangered equids are described. The main method of collecting sperm from wild equid species was electroejaculation of immobilised males. Some parameters of sperm are given: pH, volume, osmotic characteristics of the semen. The influence of various cryo-protectors and diluents on the survival of spermatozoa during cryopreservation is considered in a few papers. Cryopreservation of sperm of Przewalski’s horses and Grevy’s zebras E. grevyi were conducted. After artificial insemination of frozen-thawed spermatozoa of a Grevy’s zebra, one mare of the domestic horse E. f. caballus be-came pregnant. For transplantation of blastocysts from Przewalski’s horses and Grant’s zebras E. quagga boehmi to domestic donkeys E. africanus asinus and ponies E. f. caballus, both surgical and non-surgical methods were used. Four foals were born as a result the surgical transplantation of nine embryos from Przewalski’s horses to ponies. Twelve zebra’s embryos were transplanted into five ponies and seven donkeys. These ponies gave birth to two foals, no embryos in the donkeys had fully developed till the birth. The only experiment of non-surgical transplantation of a zebra embryo was unsuccessful. Results of a study of the oestrous cycle of the Przewalski’s horse and Grevy’s zebra by methods of ultrasound examinations and analysis of samples of urine and faeces were showed. For some species of other wild equids, the cycle was determined by behavioural reactions. The possibility of influencing the cycles of mares of Przewalski’s horses by prostaglandins given orally or with injec-tions was discussed. Results of assisted reproductive techniques applied to domestic horses are recommended as a possible model for the creation of the Genome Resource Bank for wild equids. Further optimisation of current methods used in the reproduction of domestic horses, such as intracytoplasmic sperm injection, cloning, make their use promising for the conservation of rare species of equids.