RESUMO
The present study aims were to determine the profiles of changes in progesterone (P4) and 17-ß-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.