IN-VITRO MATURATION AND FERTILIZATION OF OOCYTES RECOVERED FROM FREE-RANGING BURCHELL ZEBRA (EQUUS-BURCHELLI) AND HARTMANN ZEBRA (EQUUS-ZEBRA-HARTMANNAE)

A noninvasive repeatable method to harvest oocytes for in vitro fertil ization (IVF) could potentially be used to assist reproduction in enda ngered equid species. The objectives of this study were to evaluate a specific transvaginal ultrasound-guided oocyte recovery procedure for use in zebra mares and the general applicability of IVF procedures in zebra. Ovaries were collected from Burchell's zebra (Equus burchelli) and Hartmann's zebra (Equus zebra hartmannae) mares at routine culling for Expt. I. Of the 144 oocytes recovered from these ovaries, 70% wer e of excellent quality. No significant difference in oocyte quality wa s found between the two zebra species. Zona drilling was performed on in vitro-matured oocytes prior to IVF. Epididymal sperm from culled Bu rchell's zebra stallions were used for IVE The sperm either were expos ed to calcium ionophore or were not treated and served as a control. I n vitro fertilized oocytes were then co-cultured with zebra granulosa cells (ZGC) or with bovine oviduct cells (BOG) for up to 8 days. Overa ll, a 38% cleavage rate was obtained with 16% of sperm-exposed oocytes developing to the morula or blastocyst stage. All of the embryos that developed to at least the morula stage were cultured on BOG; whereas, none of those cultured on ZGC reached the morula stage during the sam e interval. Cleavage rates of oocytes inseminated with ionophore-treat ed or with control sperm were not significantly different, suggesting that ionophore treatment of epididymal sperm for IVF in these zebra sp ecies may be redundant. In Expt. II, 10 transvaginal ultrasound-guided oocyte aspiration procedures on five captive Burchell's zebra mares r ecovered a total of 33 oocytes (6.6 oocytes/female) of which 94% were considered viable. This approach may be an attractive means of produci ng gametes for assisted reproduction in endangered species. Furthermor e, results from this study indicate that IVF may become a means of pro ducing offspring from zebra and other equid species in the future.