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

Abstract

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.

Abstract

• Numbers and sizes of ovulatory follicles were not affected by the intravaginal device types.

• Ovulation was happened earlier in CIDR‐treated compared to sponge received females.

• Fixed time intrauterine insemination with frozen‐thawed samples near the time of ovulation resulted in greater conception in fat‐tailed females out of the breeding season.