Abstract
An experiment was conducted to determine whether the administration of progesterone or medroxyprogesterone acetate (MPA) affects the recovery of the eggs from the vagina and the subsequent fertility and implantations in the rabbit. The does were divided into 6 groups according to dose and time of administration of the gestagen. Vaginal washings for recovery of eggs were carried out twice per day for 7 days following the mating.
Subcutaneous administration of 2.5 mg progesterone on day -2, -1 and 0 gave rise to a maximal recovery of vaginal eggs (40.8 ±14.8% in group 2), and intramuscular injection of 25 mg progesterone on day 0 (the day of mating) led to the lowest egg recovery (6.9 ±4.7% in group 5, p <0.01). The earliest eggs recovered from the vagina were obtained at the first vaginal washings 24 hours after mating in groups 1, 2, 3 and 6. And 80% in group 1, 96% in group 2, 77% in group 3, 71% in group 4, 0% in group 5 and 78% in group 6 of all eggs, which were collected vaginally for 7 days following the mating, were recovered by 72 hours after mating.
Implantation of eggs in the treated rabbits were examined on day 9 by laparotomy, and 24.3±15.7% and 55.6±16.1% of eggs were found to be implanted in group 4 and group 5, respectively. No implantations occurred in any other groups. Normal-looking cleaved or fertilized eggs were recovered only in group 3 and group 4; one 2-cell egg and two 4-cell eggs in group 3, one 32-cell egg, two morulae and one blastocyst in group 4. The proportions of unfertilized eggs were 80% for group 1, 88% for group 2, 46% for group 3, 50% for group 4, 20% for group 5, and 96% for group 6.
The results in the present study indicated that administration of progesterone or MPA greatly affected the fertilization and the egg transport in the rabbit.
