The efficacy of the vaginal plug formation after mating for pregnancy diagnosis, and embyonic resorption in utero in the greater cane rat (Thryonomys swinderianus, Temminck)

Abstract

The efficacy of the detection of vaginal plug formation after mating for pregnancy diagnosis, and the degree of embryonic resorption were studied in 67 wild greater cane rats (Thryonomys swinderianus) at Esiam in the Ekumfi District, Ghana, over a period of 3 months. Vaginal plug formation was first observed on day 59 of gestation, and could be used for pregnancy diagnosis on or after that date. However, the vaginal orifice subsequently opened a couple of times prior to day 105 of gestation and further checks for pregnancy after day 59 of gestation are suggested. Animals with unplugged vaginas 105 days after mating could, however, be considered as not pregnant. The mean (+/- SE) number of implantation sites and litter size in the greater cane rat were 7.2 +/- 0.18 and 3.4 +/- 0.29, respectively, the embryonic resorption rate being 42.7 +/- 6.66%. The significant positive correlation between the number of implanted embryos and the bled-out carcase weight suggests a positive role of maternal nutrition in increasing the litter size in the greater cane rat. The incidence of post-partum oestrus during the study period was 42.1%, which suggests that the greater cane rat can be re-bred immediately after parturition.