RELATION BETWEEN STALLION SPERM BINDING TO HOMOLOGOUS HEMIZONAE AND FERTILITY

The hemizona assay (HZA) has been developed as a diagnostic test to pr edict the fertilisation potential of human spermatozoa. The aim of thi s study was to develop an HZA for stallion spermatozoa and to investig ate a possible relationship between fertility and the outcome of the H ZA in this species. Equine oocytes were obtained from ovaries collecte d at a slaughterhouse and by transvaginal, ultrasound-guided follicle aspiration. They were then denuded from cumulus cells and stored in sa lt solution at 4 degrees C until use. On the day of the experiments th e oocytes were bisected, thus providing 2 equal matching hemizonae fro m each oocyte. Semen samples from Dutch Warmblood stallions with known fertility data were used to assess the number of spermatozoa bound to the outer side of the hemizona after incubation in vitro. Sperm bindi ng to matching hemizonae of a particular stallion was similar and conf irmed the feasibility of using the HZA for the horse. Sperm hemizona b inding capacity of 10 pairs of stallions was compared by incubating 1 hemizona with the semen of a stallion and the matching hemizona with t he semen of another stallion from the same stud farm. Five matching pa irs of hemizonae were used for each pair of stallions. There was a sig nificant relationship between the mean number of spermatozoa bound to matching hemizonae and the fertility indices of stallions from each st ud farm (P<0.0001). It is concluded that HZA can be used as a valuable parameter in stallion semen analysis.