Influence of day of oestrus on egg viability and comparative efficiency of in vitro fertilization in domestic cats in natural or gonadotrophin-induced oestrus

• Published in: Journal of reproduction & fertility Vol. 98; no. 1; pp. 85 - 90
• Main Authors: Donoghue, A.M, Johnston, L.A, Goodrowe, K.L, O'Brien, S.J, Wildt, D.E
• Format: Journal Article
• Language: English
• Published: England Society for Reproduction and Fertility 01.05.1993
• Subjects: Animals; Cats; Cell Survival; Chorionic Gonadotropin - pharmacology; estrus; Estrus - drug effects; Estrus - physiology; Female; fertilization (reproduction); Fertilization in Vitro - methods; Gonadotropins, Equine - pharmacology; human chorionic gonadotropin; in vitro culture; induction; maturation; Oocytes - cytology; Oogenesis - drug effects; ova; pregnant mare serum gonadotropin; Time Factors; viability
• ISSN: 0022-4251; 1470-1626; 1741-7899
• DOI: 10.1530/jrf.0.0980085

Thirty-six domestic cats received 100 iu hCG (i.m.) on day 1, 2 or 3 of a natural, behavioural oestrus. Twenty-two anoestrous cats were injected with 150 iu pregnant mares' serum gonadotrophin (PMSG; i.m.) followed 84 h later by 100 iu hCG. Twenty-four to 26 h after hCG, all cats were examined laparoscopically to determine the number of ovarian follicles and to recover follicular eggs. Mature eggs were cultured with conspecific spermatozoa and examined 30 h later for cleavage. Within the natural oestrus group, cats on day 1 produced fewer ( P < 0.05) follicles and total eggs than females on day 2 or 3, and 88.9% of the day 1 eggs were degenerate or immature and unsuitable for in vitro fertilization (IVF). Although only 54.5% of the cats in the PMSG/hCG group exhibited overt oestrus, mean (± sem ) numbers of follicles (9.7 ± 0.8) and oocytes recovered (8.7 ± 0.8) were at least twofold greater ( P < 0.001) than those measured in the natural oestrus group (3.7 ± 0.6; 3.4 ± 0.6, respectively) or subgroups on day 2 (3.7 ± 0.4; 3.3 ± 0.4) and day 3 (5.7 ± 0.8; 5.3 ± 0.8). Overall, the proportion of eggs cleaving in vitro was similar ( P > 0.05) between the natural oestrus group (48.3%) and the PMSG/hCG group (50.9%), but the latter group produced more than twice the number of embryos per donor. Embryo quality was unaffected ( P > 0.05) by day of hormone treatment, and more than 80% of all two-cell embryos were rated good-to-excellent quality. In summary, there is a temporal relationship between day of sexual receptivity and follicular egg viability in the domestic cat: eggs on the first day of oestrus are not optimally responsive to an LH-like stimulus. There is also no evidence that PMSG/hCG treatment compromises egg quality or subsequent fertilizability in vitro . On the contrary, use of these gonadotrophins markedly improves overall IVF efficiency by increasing the total number of high quality embryos produced.