Synchronization of follicular wave before superovulation in dromedary camel by means of transvaginal follicle ablation

Abstract

The synchronization of follicular waves prior to the initiation of superovulation is a prerequisite for successful results. This study investigates the feasibility of applying transvaginal follicle ablation (TFA) as an alternative to hormonal treatments for synchronization in dromedary camels.

In experiment 1, the follicular cycle of pre-synchronized and naturally cycling camels (n = 24) was monitored and all structures > 4 mm were ablated in subgroups of animals (n = 4 each) at early, mid, and late stages of the follicular cycle. The appearance and characteristics of the next follicular wave as well as the occurrence and the fate of residual structures were investigated. In experiment 2, sixteen camels were used for superovulation subsequent to follicle ablation or conventional hormonal synchronization in a changeover design and the result of superovulation was compared among the methods. A subset of 88 embryos was transferred to recipients and pregnancy rates and pregnancy loss rates were compared between the synchronization methods.

On average, more structures were ablated from naturally cycling camels than pre-synchronized camels. Ablation of larger structures (> 10 mm) resulted in the formation of remnant structures (26.1 %) out of which 52.9 % showed structural and functional luteinization. The next follicular cohort emerged at day 2.16 ± 0.20 and 2.33 ± 0.22 after the ablation, and established dominance at day 9.33 ± 0.35 and 9.16 ± 0.32, in naturally cycling and pre-synchronized animals, respectively, with no significant difference among them (P > 0.05). All camels responded to ovulation induction at day 14 while camels ablated at mid-cycle had smaller follicles (12.88 ± 0.46 mm) at this time point compared to camels ablated at dominance or early cycle (14.13 ± 0.70 and 14.81 ± 0.42 mm, respectively; P < 0.05). A similar number of developed follicles prior to mating (13.81 ± 1.62 vs. 15.12 ± 1.65), corpus luteum (9.75 ± 1.24 vs. 10.43 ± 1.35), transferable (7.56 ± 1.06 vs. 8.50 ± 1.30), and spherical embryos (5.87 ± 1.07 vs. 6.12 ± 089) were obtained in synchronized camels by hormonal and TFA methods, respectively (P > 0.05). Embryos of the TFA group showed a trend for higher embryonic loss rate after transfer compared to the hormonally synchronized group (34.4 % vs. 17.2 %, P < 0.10).

In conclusion, follicle ablation was followed by the development of a new follicular wave capable of establishing dominance and ovulation, irrespective of the stage of the follicular cycle in which the procedure is undertaken, and can be used as an alternative way of synchronization in dromedary camels.