The prolonged reproductive response to immunization against inhibin and manipulating ovarian hyperactivity for timed ovulation in camels

• The long-term effects of immunization against inhibin in camels were investigated after 5 months from initial immunization.
• A hormonal protocol was established to control the continuous ovarian hyperstimulation and synchronize ovulation time in the immunized camels.
• The efficiency of the previously mentioned protocol on synchronizing ovulation was validated compared to conventional hormonal superovulation and timed ovulation.
• The results revealed that immunization against inhibin has a prolonged effect in camels, with a superovulatory response comparable to conventional hormonal superovulation.
• The present investigation provides a regimen to successfully control continuous ovarian hyperstimulation and synchronize ovulation time in the immunized camels.
• Considering disadvantages of using exogenous gonadotropin to induce superovulation, inhibin immuneneutralization may represent a sufficient alternative to achieve this goal.

The current study aimed: a) to investigate the extended effects of immunization against inhibin on dromedary camel ovarian function and b) to determine the efficiency of manipulating ovarian hyperactivity in the actively-immunized camels on synchronization of ovulation time compared to conventional hormonal superovulation. Sixteen pluriparous camels, Camelus dromedarius, were used during the breeding season (January-February), and were divided into 3 groups: immunized camels (n = 5) were previously immunized against inhibin (100 μg recombinant bovine inhibin-A subcutaneously followed by two boosters of 50 μg/dose each at 2-week intervals) during the former transition period (August–September), and was further subjected to a synchronization of ovulation regimen (5000 i.u. hCG intramuscularly (i.m) (1st ovulation induction, day 0) followed by 789 μg Cloprostenol acetate i.m. seven days later, and then inducing ovulation on day 17) five months after immunization; eCG-treated camels (n = 6) were superovulated by 2500 i.u. eCG (i.m.) after administration of progesterone for 13 consecutive days; control (n = 5) received 1 ml saline (i.m.). Ovarian dynamics were monitored by transrectal ultrasonography throughout the experimental period, and the changes in reproductive hormones were determined. At the peak of the mature phase of follicular development, total no. of follicles was higher (P < 0.05) in both immunized (9.0 ± 1.0) and eCG-treated camels (7.0 ± 0.6) compared to that of control (3.0 ± 0.7), whereas no significant difference was observed in dominant follicle size. Meanwhile, FSH concentration recorded higher (P < 0.05) mean values in the immunized camels than in both eCG-treated and control camels. Further, both of circulating inhibin and E2 concentrations were higher (P < 0.05) in immunized and eCG-treated camels compared to the control. Triple ovulation rates were higher (P < 0.05) in both immunized and eCG-treated camels compared to that of control with values 100, 100 and 0%, respectively. These results imply that, after 5 months from initial immunization, active immunization against inhibin originated extended ovarian hyperactivity, which could be effectively controlled for timed ovulation in camels. The results also demonstrate the efficiency of this technique as a sufficient alternative to traditional hormonal superovulation in dromedaries.