A Comparison of Long-Acting Progesterone and Intravaginal Device Priming Protocols for Inducing Ovarian Activity in...

The objectives of this study were to evaluate the efficacy of long-acting progesterone (P4) versus a P4-releasing intravaginal device (PRID) in restoring ovarian activity in dromedary camels with inactive ovaries, and to determine whether P4 priming is necessary before eCG administration. Seventy-five camels were equally assigned to three groups: a control group receiving only 1500 IU eCG; a PRID group treated with a 12-day PRIDΔ followed by eCG; and a P4 long-acting (P4 LA) group administered 1500 mg P4 LA followed by eCG on Day 12. Serum P4 and estradiol (E2) levels were measured on Days 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20, and reproductive outcomes were recorded. Results showed that the P4 LA group exhibited a rapid increase followed by a sharp decline in P4 levels, whereas the PRID group maintained more stable P4 levels, with a gradual decrease by Day 12. Moreover, from Day 16 onward, primed groups had significantly higher E2 levels than controls (p < 0.05). The response rate was 100% in the primed groups versus 60% in controls (p < 0.05), and the interval from eCG injection to ovulatory follicle development was shorter in primed groups (p < 0.05). The 18-day conception rate was highest in the PRID group (100%), followed by P4 LA (84%) and controls (53.3%). However, the pregnancy rate at Day 60 did not differ between PRID (84%) and P4 LA (80%) groups, both of which were significantly higher than controls (13.3%) (p < 0.05). In conclusion, P4 priming is essential before eCG administration, and LA P4 offers practical advantages for field veterinarians.