Efficacy of using previously used controlled internal drug release (CIDR) insert on the reproductive performance, hormone profiles and economic measures of sheep

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.

Induction of fertile estrus without the use of steroid hormones in seasonally anestrous Suffolk ewes

Objective

To evaluate the efficacy of treatments based on GnRH, GnRH-PGF2α, and/or intense exposure to novel rams to induce fertile estrus without the use of steroid hormones in seasonally anestrous Suffolk ewes.

Methods

In the first experiment, ewes were treated with one injection of GnRH, two injections of GnRH administered 7 days apart, or a sequence of GnRH-PGF2α-GnRH. In the second experiment anestrous ewes were exposed, for 36 days starting on the day of weaning, to groups of four rams of three different breeds that were alternated every day. Besides exposure to the males, the ewes were injected with saline solution (ME group, n=20), with GnRH (ME-GnRH group, n=20) or with a sequence of GnRH-PGF2α-GnRH (ME-GPG group, n=20). The rams used for male-effect were fitted with aprons to prevent mating, and ewes detected in estrus were bred to selected fertile rams. Ovarian activity was monitored by progesterone determinations in both experiments.

Results

In the first experiment sustained induction of ovarian activity was not achieved and no ewe was detected in estrus. In the second experiment induction of sustained ovarian activity was achieved in all groups. Most of the ewes were detected in estrus, 76.7 % of the ewes were mated during a 36-d breeding period and 71.7 % of all the ewes became pregnant during that period. No significant differences between groups were found for any of these variables. However, estrus detection efficiency was higher in the ME-GnRH group than in the ME group (p<0.05).

Conclusion

An intense male-effect, that included the continuous presence and frequent alternation of several rams of different breeds, was sufficient to induce ovarian activity and fertile estrus in Suffolk ewes during the period of deep anestrus without the use of hormones, although addition of GnRH improved the efficiency of estrus detection.