The efficacy of controlled internal drug release (CIDR) in synchronizing the follicular wave in dromedary camels (Camelus dromedarius) during the breeding season

The present study aimed to evaluate the efficacy of controlled internal drug release (CIDR) to synchronize the follicular wave in dromedary camels (Camelus dromedarius) during the breeding season through ovarian monitoring, evaluating sexual receptivity, and measuring progesterone (P4) and estradiol (E2) levels during and after CIDR treatment. Sixteen camels received a new CIDR containing 1.9 g of P4 for 14 days. Ultrasound ovarian monitoring was performed on the day of insertion and every 3 days until the CIDR was withdrawn. Ultrasound examinations were continued day in day out after the CIDR was withdrawn for 10 days. According to the ultrasound examinations, the percentages of camels in the breeding (follicles: 12–18 mm) and nonbreeding phases were calculated. Blood samples were collected day after day during the experimental period (24 days) from the day that the CIDR was inserted. The serum P4 and E2 concentrations were analyzed using ELISA kits. The sexual receptivity of the camels was tested daily during the course of the experiment. The results revealed that 2 and 4 days after the CIDR was withdrawn, the percentage of camels in the breeding phase (68.75% and 75.00%, respectively) was significantly (P < 0.05) higher than that in the nonbreeding phase (31.25% and 25.00%, respectively). The percentage of camels that were abstinent during CIDR treatment was significantly (P < 0.05) higher than that observed for those who were incompletely receptive or completely receptive. The P4 levels increased significantly (P < 0.05) 2 days after CIDR insertion (1.73 ng/mL) and reached maximum values (2.94 ng/mL) at Day 12. Significant (P < 0.05) decreases in the P4 levels were observed 2 to 4 days after CIDR withdrawal (1.01 and 0.80 ng/mL, respectively). The P4 levels reached minimum values (0.18–0.22 ng/mL) at Day 20 through the end of the experiment. The E2 levels differed insignificantly during and after CIDR treatment in dromedary camels. In conclusion, the treatment of dromedary camels with CIDR produced a uniform increase in serum concentrations of P4 that could completely prevent sexual receptivity but could not suppress the follicular wave. After CIDR withdrawal, the P4 levels fell and induced the emergence of a new follicular wave, and most of the camels were in the breeding (ovulatory) phase 2 to 4 days after withdrawal. Therefore, CIDR can be used to synchronize the follicular wave in dromedary camels.