Cervical relaxation for non-surgical uterus access in Santa Inês ewes

Transcervical uterine flushing and embryo transfer in sheep: Morphophysiological basis for approaches currently used, major challenges, potential improvements, and new directions (alas, including some old ideas)

At present, the success of non-surgical embryo recovery (NSER) and transfer (NSET) hinges upon the cervical passage of catheters, but penetration of the uterine cervix in ewes is problematic due to its anatomical structure (i.e., long and narrow cervical lumen with misaligned folds and rings). It is a major obstacle limiting the widespread application of NSER and NSET in sheep. While initial attempts to traverse the uterine cervix focused on adapting or re-designing insemination catheters, more recent studies demonstrated that cervical relaxation protocols were instrumental for transcervical penetration in the ewe. An application of such protocols more than tripled cervical penetration rates (currently at 90-95 %) in sheep of different breeds (e.g., Dorper, Lacaune, Santa Inês, crossbred, and indigenous Brazilian breeds) and ages/parity. There is now sufficient evidence to suggest that even repeatedly performed cervical passages do not adversely affect overall health and reproductive function of ewes. Despite these improvements, appropriate selection of donors and recipients remains one of the most important requirements for maintaining high success rates of NSER and NSET, respectively. Non-surgical ovine embryo recovery has gradually become a commercially viable method as even though the procedure still cannot be performed by untrained individuals, it is inexpensive, yields satisfactory results, and complies with current public expectations of animal welfare standards. This article reviews critical morphophysiological aspects of transcervical embryo flushing and transfer, and the prospect of both techniques to replace surgical methods for multiple ovulation and embryo transfer (MOET) programs in sheep. We have also discussed some potential pharmacological and technical developments in the field of non-invasive embryo recovery and deposition.

The pFSH dose affects the efficiency of in vivo embryo production in Santa Inês ewes

This study compared the follicular growth, superovulatory response, and in vivo embryo production after administering two doses of porcine follicle-stimulating hormone (pFSH) in Santa Inês ewes. The estrous cycle of 36 multiparous ewes was synchronized with the Day 0 protocol and superovulated with 133 mg (G133, n=18) or 200 mg (G200, n=18) of pFSH. Ultrasonographic evaluations of the ovaries were performed, ewes were mated and submitted to non-surgical embryo recovery. Viable blastocysts were stained with Nile Red and Hoechst. The G200 had a greater number of medium and large follicles, as well as a larger size of the third largest follicle. A total of 97.2% (35/36) of the ewes came into estrus and it was possible to transpose cervix in 80.6% (29/36). There were no effects of treatments in the response to superovulation, the proportion of ewes in which was possible to transpose the cervix, the number of corpora lutea, the number of anovulatory follicles, the proportion of ewes flushed with at least one recovered structure, number of recovered structures, number of viable embryos, viability rate, and recovery rate. The G200 ewes were in estrus for a longer period of time than the G133 ewes (54.0 ± 4.5 h vs. 40.3 ± 3.6 h) and produced more freezable embryos (6.5 ± 1.6 vs. 2.3 ± 0.7) than G133. Both doses promoted an efficient superovulatory response and did not affect embryonic lipid accumulation. The dose of 200 mg of pFSH showed greater potential to increase the superovulatory response, as it increased follicular recruitment and the recovery of freezable embryos.

Effect of antifreeze protein I in the freezing solution on in vivo-derived sheep embryos

This study evaluated the effects of different antifreeze protein type I (AFP I) concentrations added to a slow freezing solution in sheep in vivo-derived embryos. Good-quality embryos were allocated into: AFP-free (CONT); 0.1 μg/mL of AFP I (AFP0.1); or 0.5 μg/mL of AFP I (AFP0.5). After thawing, embryos were in vitro cultured (IVC) for 48 h. At 24 h and 48 h of IVC, dead cells and apoptosis, mitochondrial activity, intracellular reactive oxygen species (ROS), and glutathione (GSH) evaluations were performed. At 24 h, evaluated embryos were submitted to RT-qPCR for metabolism (SIRT2, PRDX1, OCT4, CDX2) and quality (AQP3, CDH1, HSP70, BAX, BCL2) genes. The in vitro survival rate was 56% (22/39) for CONT, 60% (32/53) for AFP0.1, and 53% (23/43) for AFP0.5 (p > 0.05). A tendency (p = 0.09) for a higher blastocyst hatching rate was noted in AFP0.1 (62%) compared to AFP0.5 (33%), and both groups were similar to CONT (50%). An increased (p < 0.05) mitochondrial activity at 24 h was observed in AFP0.1 compared to CONT. No differences (p > 0.05) were observed in oxidative stress homeostasis and viability between treatments. A downregulation (p < 0.05) of CDH1 in AFP0.1 and a downregulation of AQP3 in AFP0.5 were observed in comparison to the other groups. An upregulation (p < 0.05) was detected in HSP70 and BCL2 on AFP0.5 compared to AFP0.1 group. The addition of AFP I in slow freezing solution can benefit cryopreserved sheep in vivo-derived embryos, without affecting embryonic survival.

Review: Non-surgical artificial insemination and embryo recovery as safe tools for genetic preservation in small ruminants

Artificial insemination (AI) and in vivo embryo production (or multiple ovulation and embryo transfer, MOET) programs are both instrumental in accelerating the propagation of genetically and economically superior goats and sheep. The aim of this review was to present the current gestalt of non-surgical AI and embryo recovery (NSER) procedures in small ruminants. Small body size, precluding rectal palpation, and highly limited penetrability of the uterine cervix in ewes are the major reasons for the scarce use of non-surgical assisted reproduction techniques in this species. As a result, AI and embryo recovery techniques in sheep mainly involve laparoscopy or laparotomy (LAP). In does, however, the Embrapa method of AI allows for successful intrauterine deposition of semen, resulting in pregnancy rates from 50 to 80% under field conditions (>3 000 goats inseminated) when frozen-thawed semen is used. After the administration of prostaglandin F2α (PGF2α), non-surgical (transcervical) embryo recovery is also feasible in goats, with the cervical penetration rate approaching 100%. There is a paucity of information on the efficacy of non-surgical AI using frozen semen in sheep, but the results are satisfactory with fresh, cooled, or chilled ram semen. An application of the NSER technique in ewes has greatly improved over the last decade, and cervical penetration rates of ∼90% can be achieved when a hormonal cervical dilation protocol using PGF2α, oxytocin, and/or estradiol ester (e.g., estradiol benzoate) is applied. In some genotypes of sheep, sufficient cervical dilation can be induced without estradiol ester included in the protocol. Several studies indicated that recovery of transferable quality ovine embryos using NSER is comparable to that employing a ventral midline laparotomy, and NSER is evidently a method of choice when animal welfare is concerned. Considering both the number of retrievable embryos and animal well-being, the NSER is a viable alternative for surgical procedures. With further developments, it has the makings of a primary, if not exclusive, embryo recovery technique in small ruminants worldwide.

Hormonal protocol used for cervical dilation in ewes does not affect morphological embryo quality but reduces recovery rate and temporarily alters gene expression

BACKGROUND

Information on the impact of hormonal protocols for cervical dilation on the quality of ovine embryos is scarce.

METHODS

To compare the quality of embryos after cervical dilation protocol, ewes (n = 64) were allocated into either a treated group (100 μg estradiol benzoate intravenous and 0.12 mg cloprostenol intramuscularly, 12 hours before embryo collection plus 100 iu oxytocin intravenous 15 minutes before the collection procedure) or a control group (saline). Luteal function was analysed using ultrasonography and P4 measurement. Some collected embryos were frozen/thawed for gene expression, others were cultured in vitro, frozen/thawed for gene expression, and the remaining embryos were fixed for the apoptosis test (TUNEL test).

RESULTS

The treatment reduced fluid (p=0.04) and structure (p=0.03) recovery rates, but the morphological quality, development stage, and apoptosis incidence of the embryos were not affected by treatment. The corpora lutea of the control group had greater blood perfusion (p = 0.002) and greater P4 concentrations at 6, 9, and 12 h after the treatment (p < 0.0001). The expression of BAX, BCL2, PRDX1, and HSP90 genes were not affected by the treatment. However, the embryos in the treated group had fewer NANOG and OCT4 transcripts than control embryos (p = 0.008; p = 0.006, respectively). After culture, there was no difference between the groups in any gene.

CONCLUSION

The hormonal protocol for cervical dilation reduced the efficiency of embryo collection. In addition, the treatment induced luteolysis and a transient alteration of embryo gene expression, however there were no detectable changes in embryo morphological quality, development stage, or incidence of apoptosis.

Use of oxytocin to attain cervical dilation for transcervical embryo transfer in sheep

The aim of this work was to determine whether a cervical dilation protocol (CDP) composed of only oxytocin can be used to perform transcervical (non-surgical) embryo transfer in sheep (NSET) without affecting the viability of the corpus luteum (CL). Likewise, we evaluated whether a cervical transposing test with a Hegar dilator (CT Hegar test), performed at oestrous time, could be used to screen ewes for NSET (greater or lower chances to transpose the cervix). For that, oestrous and ovulation synchronization was performed in 25 Santa Inês ewes to induce the dioestrous condition. Animals went through the following CDP in a crossover design: E + OX, oestradiol benzoate (100 µg intravenously [IV]) and oxytocin (100 IU IV); OX, oxytocin (100 IU IV); and SAL, saline solution (IV). Using a Hegar dilator, cervical transposing attempts were performed at oestrous (D0) and dioestrous time (D8). The viability of the CL (morphology, luteal blood flow and progesterone values) was evaluated by ultrasonography (colour Doppler and B-mode) and by serum progesterone measurement from D7 to D13. The cervical transposing rate was lower for the SAL group (64%; 16/25; p < .05) and did not differ between the E + OX (88%; 22/25, p > .05) and OX (84%; 21/25, p > .05) groups. No treatment affected the CL viability. The CT Hegar test showed a high sensitivity (85.7%-93.3%), satisfactory accuracy (72%-84%), low false-negative rate (6.7%-14.6%), but high false-positive rate (46%-66.7%). In conclusion, a CDP protocol composed exclusively of oxytocin can lead to good cervical transposing rates and does not affect the viability of the CL. In addition, a screening test (CT Hegar) performed at oestrus can identify ewes for which cervical transposing will likely not occur at NSET.

Successful transcervical uterine flushing can be performed without or reduced dose of oestradiol benzoate in cervical relaxation protocol in Dorper ewes

This study assessed the efficiency of cervical relaxation protocol using none, half or full dose (1.0 mg) of oestradiol benzoate in Dorper ewes subjected to non-surgical embryo recovery (NSER). Thirty-six pluriparous ewes received progestogen sponge (60 mg) for 9 days plus eCG administration (300 IU i.m.) 24 hr before sponge removal. Ewes were not mated and were randomly assigned to receive at 16 hr before NSER 37.5 µg d-cloprostenol i.m. and different doses of oestradiol benzoate: 0.0 mg (0EB group; n = 12); 0.5 mg (0.5EB group; n = 12) or 1.0 mg of oestradiol (1.0EB group, n = 12). All ewes received oxytocin (50 IU) i.v. 20 min before NSER, which was performed 8 days after sponge removal. Corpora lutea were counted by transrectal ultrasonography 24 hr before NSER. After procedure, the ewes were kept in natural breeding period to check their post-NSER fertility. NSER was performed in 91.7% (33/36) of the animals with overall fluid recovery efficiency over 97% (p > .05). The cervical transposing with Hegar dilator was longer (p < .05) in 0EB (4.2 ± 0.3 min) compared to 0.5EB (1.7 ± 0.3 min) and 1.0EB group (1.5 ± 0.3 min). The cervical transposing with mandrel/catheter was longer (p < .05) in 0EB (2.4 ± 0.5 min) than 1.0EB group (1.3 ± 0.5 min). Overall duration of uterine flushing was 25.4 min with structure recovery rate of 43.5%, with no difference among groups (p > .05). The post-NSER fertility was higher (p < .05) in 0.0EB (90%) than 0.5EB group (36.4%). In conclusion, NSER can be successfully performed in Dorper ewes by using a cervical relaxation protocol without oestradiol benzoate.

Transcervical vs. laparotomy embryo collection in ewes: The effectiveness and welfare implications of each technique

This study assessed animal welfare in ewes subjected to transcervical (TC) or laparotomy (LP) embryo collection, and the efficiency of these two techniques. Santa Inês ewes (n = 57) received a protocol for estrus synchronization and superovulation. Cervical dilation protocol was initiated 12 h before embryo collection in all ewes. Depending on the success of cervical passage, the embryos were collected from ewes by either TC or LP. Records were made of physiological (rectal temperature (RT) and heart rate (HR)), endocrine (cortisol concentration), biochemical (glycaemia, total proteins, globulin and albumin concentrations), and behavioral variables. Data were recorded before fasting (BF) and sedation (BS), during (DC) and immediately after embryo collection (IAC), and 1 h (1hAC), 3 h (3hAC), 6 h (6hAC), 12 h (12hAC), 24 h (24hAC), and 48 h (48hAC) after embryo collection. The LP and TC procedures were applied to 22 and 35 ewes (with 100.0% and 94.3% of procedures being successful, respectively). The use of LP took longer than TC (P = 0.007) but was less effective in the recovery of uterine fluid and structures (P = 0.0002 and P = 0.0180, respectively), with no difference in the number of viable embryos recovered per animal. The TC procedure induced a greater RT at DC (P = 0.002) and IAC moments (P < 0.0001). The heart rate was greater in TC than LP in IAC (P = 0.036). On the other hand, HR was greater with LP at 12hAC (P = 0.033) and 24hAC (P = 0.002). There was no interaction between the procedures and time on total proteins, albumin, or globulin concentrations. The TC procedure induced greater glycaemia than LP in IAC (P < 0.0001). LP induced greater serum cortisol concentration than TC at DC, IAC, 1hAC (P = 0.0004; P = 0.0006; P = 0.036, respectively), even though it was greater in the TC than the LP procedure at 3hAC (P = 0.008). In conclusion, the TC embryo collection was more effective than the traditional LP procedure. Although both embryo collection procedures affected ewes' welfare, the TC procedure is probably less stressor than the LP.