Steroid hormone profile of Markhoz does (Iranian Angora) throughout estrous cycle and gestation period

The present study aims were to determine the profiles of changes in progesterone (P4) and 17-β-estradiol (E2) in the peripheral blood of Markhoz goat (Iranian Angora) during estrous cycle, gestation, and parturition throughout natural breeding season. Gestation length averaged 145.3 ± 0.8 days, and the litter size was 1.1 ± 0.1. Birth weight ranged 2.4–2.8 and 1.5–2.5 kg in male and female kids, respectively. The mean estrous cycle lengths were 20.3 ± 0.4 and 20.9 ± 0.4 days for PGF_2α-induced and natural cycles, respectively. Blood sampling was carried out daily during estrous cycle and weekly during gestation till parturition. E2 attained higher level (24.7 ± 2.15 pg mL⁻¹) at estrus phase and dropped down to the lower level (18.80 ± 1.16 pg mL⁻¹) within 3 to 4 days post-estrus. Concomitantly, P4 started to increase from the mean basal value of 0.5 ± 0.03 ng mL⁻¹ on day 0 to 6.88 ± 0.95 ng mL⁻¹ on day 6 of estrous cycle and reached the peak value of 12.8 ± 0.61 ng mL⁻¹ on day 12. From day 15, a decline was observed in P4 values till the end of the cycle. P4 remained at lower concentrations for 20–50 days of gestation, then increased and reached to its maximum level (13.51 ± 0.279 ng mL⁻¹) in week 15 and returned again to its basal values within 1–2 weeks before parturition. The results will be discussed in terms of the usage of steroid hormone profile in several assisted reproductive technologies.