Comparison of four methods of inducing pseudopregnancy in rabbits

Abstract

This study was conducted to compare several methods for inducing pseudopregnancy in local rabbits. The study used 25 clinically healthy rabbits of local breeds, aged 1-1.5 years, with a bodyweight of 1.8-2.2 kg. The rabbits were divided into five treatment groups (n = 5): R1, R2, R3, R4, and R5. Each group was given a different treatment. Group R1 was injected intramuscularly with 100 IU PMSG and mated with males three days later, which was followed by an intravenous injection of 75 IU hCG. Pseudopregnancy in group R2 was induced through artificial copulation by inserting a 1 cm long cotton bud into vaginal lumen at 5 a.m. Pseudopregnancy in group R3 was induced using 50 IU hCG intramuscularly. Group R4 was injected intravenously with 5 g GnRH and then intramuscularly with 100 IU PMSG and three days later with 75 IU hCG. Blood samples were collected on days 2, 4, 6, and 8 for estrogen and progesterone measurement, whereas an ovarian histological observation of all groups was performed on day 8. The results show that the highest concentration of estrogen was obtained in group R2, which was significantly different from the other groups (P <0.05), but the difference in examination time was not statistically significant (P > 0.05). Furthermore, the concentration of progesterone in all groups fluctuated at various times of the day. Progesterone concentrations were higher in group R5, in which pseudopregnancy was induced with PMSG and hCG. Group R5 showed a significant difference (P <0.05) with R2, R3, and R4, but the difference with the positive control group (R1) was not significant (P > 0.05). The numbers of corpora lutea in groups R1, R2, R3, R4, and R5 were, respectively, 6.87 ± 1.58, 6.22 ± 2.71, 6.74 ± 1.94, 5.98 ± 2.04, and 8.8 ± 1.90, and the largest diameter was obtained in R5 (1.65 ± 0.37 mm). In conclusion, the best method of inducing pseudopregnancy in local rabbits is the administration of PMSG and hCG.