322 INDUCTION OF SUPEROVULATION IN PROESTRUS DOGS USING SERUM GONADOTROPIN OF PREGNANT MARES AND HUMAN CHORIONIC GONADOTROPIN

Abstract

Several factors influence the limited application of assisted reproductive technologies (ART) in the canine species. Most problems arise because of the complex nature of reproductive physiology of the dog. For example, dogs are monoestrus, generally exhibiting oestrus only once every 6 month to 1 year. In the canine species, there has been little research on the ART because of difficulties associated with anatomy and reproductive physiology. Because in vitro maturation of canine oocytes has been particularly difficult, in vivo matured oocytes have been used in somatic cell nuclear transfer. However, the number of oocytes that can be obtained using this approach is limited, with ∼6 to 10 good oocytes being obtained per collection. The present study was undertaken to evaluate the effects of different dosages of eCG on folliculogenesis in the dog and to determine the number of oocytes that might be obtained after ovulation. The experimental design involved 3 groups that were treated with different dosages of eCG at the early stage of proestrus; Group A was a nontreatment (control) group, Group B received 200-IU eCG SC injections every day, and Group C was injected with 500 IU of eCG every 2 days until reaching 2 to 3 ng mL^–1 serum progesterone concentration, respectively. Dogs in Groups B and C received a 1 000-IU hCG SC injection when progesterone concentrations reached 2 to 3 ng mL^–1. The serum progesterone concentration was examined with a Radioimmunoassay Kit (Diagnostic Systems Laboratories Inc., Webster, TX, USA). The day of ovulation was considered as the day when serum progesterone concentration reached 4.0 to 7.2 ng mL^–1. Approximately 70 to 76 h after ovulation, the dogs were subjected to the oocyte collection procedure. One-way ANOVA followed by Duncan’s multiple range tests was performed. The significance level was <0.05. In total, 446 oocytes were recovered from 60 bitches, with an average of 6.4 oocytes/dog in Group A (from 49 bitches), 16.6 oocytes/dog in Group B (from 5 bitches), and 8.5 oocytes/dog in Group C (from 6 bitches). The oocytes collection rate (number of oocytes per dog) in Group B was higher (P < 0.05) than those in the other 2 groups. In conclusion, the results showed that eCG treatment with hCG in early-proestrus-stage bitches can result in a greater number of recovered in vivo matured oocytes. This technology could become a useful research tool for canine cloning and ART.