DEVELOPMENT OF EMBRYOS PRODUCED BY INTRACYTOPLASMIC SPERM INJECTION OF CAT OOCYTES

Development of cat oocytes following intracytoplasmic sperm injection (ICSI) and in vitro fertilization (IVF) was compared in two experiment s. Domestic cat donors (used as a model for wild felids) were treated with 150 IU equine chorionic gonadotrophin (eCG) on treatment day 1 or a total of 10-15 IU of follicle-stimulating hormone (FSH) over four d ays, followed by 100 IU human chorionic gonadotrophin (hCG) on day 5 a nd follicular aspiration 24-26 h later. A jaguarundi (Herpailurus yagu arondi) female was stimulated twice with FSH (20 IU) or eCG (300 IU) a nd hCG (250 or 300 IU) before oocyte recovery. After storage at 4 degr ees C, domestic cat semen was washed and processed. For ICSI, denuded oocytes were each injected with an immobilised spermatozoon. IVF oocyt es were co-incubated with 5 X 10(4) motile spermatozoa/0.5 ml for 4-6 h. Noncleaving oocytes were fixed and stained 24-28 h after injection or insemination. Presumptive zygotes were cultured before transfer on day 5 (experiment I only) or evaluation on day 7 (experiments I and II ). In experiment I, fertilization frequency was 67.9% (72/106) and 58. 1% (122/210) for IVF and ICSI oocytes, respectively (P > 0.05). Most n oncleaving ICSI oocytes (71/88, 80.7%) at 24 h were at metaphase II, o f which half (35/71, 49.3%) had an activated spermatozoon (n = 4) or p remature chromatin condensation (PCC, n = 31) of the sperm head. All 6 9 day 7 IVF embryos developed to morulae (> 16-cells, 46.7%) or blasto cysts (53.3%), and 59/63 (93.7%) ICSI embryos reached the morula (50.8 %) or blastocyst (42.9%, P > 0.05) stage. Mean cell number in IVF and ICSI embryos was 136 and 116 (P > 0.05); morulae had 77 and 46 (P < 0. 05) and blastocysts had 187 and 209 (P > 0.05) cells, respectively. Af ter transfer of 10 or 11 day 5 ICSI morulae to each of four recipients , a total of three kittens were born to two dams at 66 or 67 days. Of 18 fair-to-good quality oocytes recovered from a jaguarundi on two occ asions, 10 (55.6%) embryos were produced by ICSI with fresh (n = 5) or frozen (n = 5) conspecific spermatozoa, but no jaguarundi kittens wer e born after transfer of these embryos to domestic cat recipients. In experiment II, cleavage frequency following IVF (15/17, 88.2%) and ICS I (31/38, 81.6%) was higher (P < 0.05) than following sham ICSI (13/35 , 37.1%). Mean cell number (27 cells) and blastocyst development (0%) on day 7 was lower (P < 0.05) in the sham ICSI group than in the ICSI group (45 cells, 15.6% blastocysts) which, in turn, was lower(P < 0.05 ) than the IVF group (94 cells, 46.7% blastocysts). We have demonstrat ed that ICSI can be applied successfully in domestic felids and sugges t that the technique will effectively augment other biotechniques bein g developed for enhancing reproduction in endangered felids. (C) 1998 Elsevier Science B.V. All rights reserved.