Effects of Progestagen and Pmsg on Estrous Synchronization and Fertility in Kivircik Ewes during Natural Breeding Season

Age as a Determinant of the Effectiveness of Intravaginal Sponges Impregnated with Progestin and Equine Chorionic Gonadotropin for Multiple Births Induction of Awassi Ewes

The present study was conducted to evaluate the role of age in the effectiveness of intravaginal progestin-impregnated sponges (IPIS) along with equine chorionic gonadotropin (eCG) on the multiple birth rates of Awassi ewes. One hundred mature ewes (live weight was 35–40 kg and age 2–5 years) were allocated to three groups according to their ages (n = 29, 2-3 years;n = 34, 3-4 years; and n = 37, 4-5 years). All ewes were impregnated with IPIS, injected with 20 mg cronolone, for 14 days, and eCG (400 IU, i.m.) at sponges withdrawal. All treated ewes came to estrus (100%); the highest twining rate was recorded in ewes aged 2-3 years, while the highest triple rate were found in those aged 3-4 years. A negative correlation coefficient was recorded between the age of treated ewes and the multiple births. In conclusion, the best age of Awassi ewes for estrus synchronization programs and multiple birth outcomes using IPIS along with eCG is 2–4 years.

Biochemical and molecular characterisation of sialylated cervical mucins in sheep

Sialic acid occupies terminal positions on O-glycans of cervical mucins, where they contribute to the increased viscosity of mucin thereby regulating sperm transport. This study characterised the sialylated cervical mucins from follicular phase mucus of six European ewe breeds with known differences in pregnancy rates following cervical artificial insemination using frozen-thawed semen at both synchronised and natural oestrus cycles. These were Suffolk (low fertility) and Belclare (medium fertility) in Ireland, Ile de France and Romanov (both with medium fertility) in France and Norwegian White Sheep (NWS) and Fur (both with high fertility) in Norway. Expression of mucin and sialic acid related genes was quantified using RNA-sequencing in cervical tissue from Suffolk, Belclare, Fur and NWS only. Cervical tissue was also assessed for the percentage of cervical epithelial populated by mucin secreting goblet cells in the same four ewe breeds. Biochemical analysis showed that there was an effect of ewe breed on sialic acid species, which was represented by Suffolk having higher levels of Neu5,9Ac2 compared to NWS (P < 0.05). Suffolk ewes had a lower percentage of goblet cells than Fur and NWS (P < 0.05). Gene expression analysis identified higher expression of MUC5AC, MUC5B, ST6GAL1, ST6GAL2 and lower expression of ST3GAL3, ST3GAL4 and SIGLEC10 in Suffolk compared to high fertility ewe breeds (P < 0.05). Our results indicate that specific alterations in sialylated mucin composition may be related to impaired cervical sperm transport.

Approaches of estrous synchronization in sheep: developments during the last two decades: a review

The objective of the current review was to summarize the protocols used for estrous synchronization in ewes during the last two decades. Progesterone (P4) is a major hormone used in most protocols. P4 in the form of a controlled internal drug releasing (CIDR) device, medroxyprogesterone acetate (MAP), and fluorogestone acetates (FGA) has been used for estrous synchronization. Also, gonadotropins such as equine chorionic gonadotropin (eCG) and gonadotropin-releasing hormone (GnRH) are often administered at the end of P4-based protocols to improve fertility. Moreover, the administration of prostaglandins (PG) and ram effects have been used for estrus induction and synchronization of ewes. The findings of previous studies indicate that the outcome of administering various synthetics P4 analogues (CIDR, MAP, and FGA) in ewes is comparable in terms of estrous synchronization/induction. The supplementation of P4-based protocols with eCG, however, improves the estrus response and pregnancy rate during breeding and non-breeding season. On the other hand, PG is effective for successful estrous synchronization during the breeding season only. Often, two injections of PG are administered either 11 or 14 days apart along with P4-based protocols to lyse ovine corpus luteum (CL) when it is receptive to PG i.e., 3 days post-ovulation. Alternatively, the "ram effect" has been shown to improve the efficacy of P4-based protocols and can be used as an alternative to eCG in ewes. The current review describes the methods of synchronization and their outcomes during breeding and a non-breeding season in ewes.

A meta-analysis of the effects of synchronization protocols applied to sheep in Turkey on pregnancy rates during breeding and non-breeding seasons

This study aimed to determine common pregnancy rates and effect sizes with meta‐analysis of studies investigating the effect of different synchronization protocols applied to sheep during breeding and non‐breeding seasons on pregnancy rates. Common pregnancy rates were estimated by coalescing pregnancy rates of studies performed independently, and heterogeneity between the studies was investigated. The meta‐analysis included 24 studies that determined pregnancy rates in 78 different groups consisting of 1934 sheep with five different synchronization protocols in Turkey between 2001 and 2020. Among the different synchronization methods, the P4+PMSG group (90.37%) during the breeding season and P4+PGF2α (69.77%) and P4 (68.75%) groups during the non‐breeding season showed the highest pregnancy rate. Also, the effect size of P4+PMSG application during the breeding season was calculated as 0.934 (95% confidence interval: 0.901–0.967), and the effect size of P4+PGF2α application during the non‐breeding season was calculated as 0.709 (95% confidence interval: 0.406–1.013). To conclude, the combination of P4+PMSG during the breeding season and progestogen and other hormone applications during the non‐breeding season are the most effective methods for estrus synchronization and for achieving the desired pregnancy rates.

Effect of feeding greater amounts of dietary energy for a short-term with or without eCG injection on reproductive performance, serum metabolites and hormones in ewes

This study was conducted to compare the effect of transient high-energy diet in a short-term period with or without eCG injection on ovarian follicle development, twining rate, serum metabolites and hormones in ewes. A total of 45 estrous cyclic Naeini ewes were randomly assigned to three experimental groups: 1-Control (control), 2-High energy short-term feeding (HE), and 3-high energy short-term feeding + eCG injection (HEe). Ewes were housed in individual pens with free access to feed and water. The stage of the estrous cycle of all ewes was synchronized by insertion of intravaginal progesterone sponges. Focus feeding started from 4 days before until 1 day after sponge removal. Follicle development was monitored from 4 days before until 1 day after sponge removal and blood samples were taken during this time. Results showed that ewes fed high energy diets (HE and HEe) had greater (P < 0.05) large follicle numbers compared with the control group. Feeding high energy diets increased (P < 0.05) serum glucose, cholesterol and insulin, but had lesser (P < 0.05) serum urea nitrogen concentrations near the time of ovulation. After the start of experiment, ewes fed high energy diets had less (P < 0.05) serum estradiol. However, 1 day after sponge removal, serum estradiol in HE and HEe groups increased (P < 0.05). It was concluded that short-term (6-day) changes in amount of dietary energy with or without eCG injection increased twin births and had beneficial effects on the blood metabolites and hormone concentrations in Naeini ewes.

Effects of progestagen exposure duration on estrus synchronization and conception rates of crossbreed ewes undergoing fixed time artificial insemination

Synchronization of estrus and ovulation are of paramount importance in modern livestock improvement programs. These methods are critical for assisted reproduction technologies, including artificial insemination and embryo transfer, that can increase productivity. In the current study, subcutaneous implants containing norgestomet were placed for long (14 days), medium (9 days), and short (5 days) periods of time in 70 crossbred ewes undergoing fixed-time artificial insemination. The resulting effects on estrus synchronization and conception rates were subsequently evaluated. Among the synchronized ewes, 85.7% (60/70) underwent estrus over a period of 72 h after progestagen treatment ceased. The shortest mean interval between withdrawal of the device and onset of estrus (34.2 ± 8.9 h) was observed in the G14 days of P4 group (p < 0.05). The conception rate of the G14 days of P4 group was statistically higher than that of the other groups (83.3% vs. 60.9% vs. 47.8%; p < 0.05). In conclusion, 14 days of norgestomet treatment produced higher conception rates and a greater number of pregnancies at the beginning of the breeding season.