Relationship between the size of the dominant follicle, vaginal electrical resistance, serum concentrations of oestradiol and progesterone and sexual receptivity during the follicular phase of the dromedary camel (Camelus dromedarius)

Thirteen dromedaries were used to study the relationship between the size of the dominant follicle, vaginal electrical resistance (VER), sexual receptivity, and serum concentrations of oestradiol-17β (E2) and progesterone (P4) throughout the follicular phase. On a daily basis, the animals experienced teasing with a vasectomised camel, trans-rectal ultrasound examination of the ovaries, and measurement of VER and blood collection for serum E2 and P4. Results revealed no significant differences between the mean VER in the animals that had a follicle of 5-10 mm (group I, n = 11), 11-15 mm (group II, n = 12) and 16-20 mm (group III, n = 13). The VER did not correlate with the follicular size. The E2 concentrations in the animals in groups II (60.14 pg/ml) and III (66.52 pg/ml) were significantly (P < 0.05) higher than those of animals in group I (48.31 pg/ml). E2 was positively correlated (r = 0.50; P < 0.05) with the overall size of the follicles. The P4 concentration was significantly (P < 0.05) lower in the animals of group II than in those in groups I and III. Serum P4 concentrations were inversely correlated (r = −0.40; P < 0.05) with the overall size of the follicles. Complete sexual receptivity was reported in 63.64%, 16.67% and 76.92% of the animals in groups I, II and III, respectively. In group III, significant (P < 0.05) complete sexual receptivity was confirmed. However, 23.08% of the animals were incompletely receptive. In conclusion, impedometric characteristics of the vaginal mucosa were not a reliable method for predicting the dominant follicular size during the follicular phase in dromedary camels.