Timing of ovulation in the fat‐tailed Qezel ewes after synchronization with vaginal devices containing endogenous or exogenous synthetic progestogens during out of the breeding season

BACKGROUND: Wide range of ovulation distribution is the main restricting factor in establishing the pregnancy following oestrus synchronization (ES) and fixed time insemination (FTI) in sheep. OBJECTIVES: Determining the ovulation time (OVT) following ES with two different vaginal devices, its relation to progesterone and conception upon FTI with frozen/thawed semen. METHODS: Oestrus was synchronized using either controlled internal drug release (CIDR) (ewe, n = 6; ewe lamb, n = 5) or vaginal sponge (ewe, n = 6; ewe lamb, n = 5) insertion for 12 days, plus Equine chorionic gonadotropin (eCG) at devices removal (Day 0). Sizes of the ovarian follicles were measured using transvaginal probe at −12, 0 and 30–33, 53 h and continued every 3–4 h until 75 h after eCG treatment. Serum progesterone amounts were measured at −12, 0, +2 and +11. Laparoscopic FTI was done at 60.5 ± 0.5 h. RESULTS: The CIDR‐treated group initiated and completed ovulations earlier compared to sponge‐treated females (median: 64 vs. 71 h; p < 0.05). Ewe lambs were ovulated earlier compared to ewes in the sponge‐treated group (66.71 vs. 71.5; p = 0.017). Mean sizes of ovulatory follicles and corpora lutea were not affected by device types. Higher amounts of progesterone were observed in CIDR group compared to sponge‐treated group at device removal (2.68 ± 0.12 vs. 0.30 ± 0.01 ng/mL; p < 0.001). The conception was confirmed in 2/10, and 5/11 females of sponge and CIDR‐treated females, respectively. CONCLUSIONS: Types of progestogens influence the OVT, and consequently the result of FTI with frozen/thawed semen. The optimum timespan for FTI should be chosen according to the device types during non‐breeding season.