The aim of this study was to estimate of ovulation time and parturition day at the same time as breeding in small dog by vaginal cytology and to confirm the accuracy by comparing the expected parturition day and the real one. Characteristic features of vaginal cytology during the estrous cycle were the high proportion of large intermediate cell, superficial cell, anuclear cell and erythrocyte in proestrus, superficial cell and anuclear cell in estrus, parabasal cell, small intermediate cell, large intermediate cell and leukocyte in diestrus, parabasal cell and small intermediate in anestrus, respectively. When day 0 was the parturition day, the period of pregnancy is 67.45(64~75) days when the cornification index (CI) is over 90%. Also, on the basis of ovulation day, 63.65(59~66) days was confirmed, and 57.0(52~60) days was confirmed based on the first day of diestrus. There are the gap of 4 days between the day being over 90% in CI and ovulation day. On the basis of this, when expecting parturition day based on the day being over 90% in CI by vaginal cytology, 18.1% was produced in the same of the expected parturition day and the real one, 30.3% and 33.3% were produced in the gap of one day and two days, respectively so, the accuracy within two days was 81.7%. In addition, based on the first day of diestrus, it also was identified to 81.7% as the difference between the expected parturition day and the real one within 2 days. It demonstrated there are any difference between any expected parturition day by vaginal cytology. Thus on the basis of the day of being over 90% CI, it is fully thought to using clinically due to the possibility of prediction the parturition day at the same time as the determination of the proper time of the optimal mating time.

Keywords: ovulation time, parturition day, vaginal cytology, estrous cycle, cornification index