The use of cytological examination of vaginal smears (CEVS) in the selection of rabbits for superovulation

Abstract

In the present study, we examined two factors associated with the reproduction of rabbit does, cytology of vaginal smears and color of vulva, as potential predictors of the success of superovulation treatment. Vulval color and vaginal smear cytology were assessed in 55 young New Zealand does. Superovulation was then induced by a single administration of eCG (20 IU/kg BW i.m.). Does were artificially inseminated 3 days later, followed by intravenous administration of hCG (120 IU per animal). Does were classified with regard to vulval color (white, rose, red, purple), and the predominant cell type in the vaginal smear (i.e. parabasal, intermediate, superficial, or anuclear). Furthermore, we categorized cells into two groups because we usually observed parabasal and intermediate cells (Group A), and superficial and anuclear cell (Group B) in the same smear. Does were humanely killed 19 h after administration of hCG and the total numbers of corpora lutea (CLs), oocytes, and zygotes (i.e. 1-cell embryos) were determined. The zygotes were assessed by morphological appearance and classified as normal or abnormal. The color of the vulva at the time of eCG treatment did not predict the success of superovulation in terms of the number of CLs, oocytes or zygotes. Does with predominantly superficial cells in vaginal smears yielded significantly fewer CLs and oocytes–zygotes (OZ) compared to does with predominantly parabasal, intermediate, or anuclear cells ( P<0.05). Does with predominantly superficial cells in vaginal smears tended to yield fewer normal zygotes (nZ), but this reached significance only when compared to does with predominantly parabasal cells ( P<0.05). Does in Group A yielded significantly more ( P<0.05) CLs, OZ and nZ compared to does in Group B. Does with predominantly parabasal and intermediate cells in vaginal smears and rose color vulva tended to yield more OZ and nZ ( P<0.05). These results suggest that the cytology of vaginal smears may help identify does with a significantly higher likelihood of yielding low numbers of CLs, oocytes, or nZ.