Effect of repeated transvaginal ultrasound-guided follicle aspiration on fertility in mares

Optimization of recovery and maturation methods for cumulus-oocyte complexes in jennies

Embryo production in donkeys is inefficient compared with that in other livestock. Obtaining a sufficient number of MII oocytes is the first step to solving this problem. In this study, the number, morphology and maturation rates of cumulus-oocyte complexes (COCs) obtained from abattoir-derived ovaries or live jennies were compared. The diameter of follicles from abattoir-derived ovaries was measured and divided into group 1 (2-6 mm), group 2 (6-10 mm), group 3 (10-20 mm), group 4 (20-28 mm) and group 5 (>28 mm). The results showed that the number of follicles per ovary in group 2 (3.6 ± 0.28) and 3 (4.2 ± 0.90) was higher than that in the other groups (p < .05). The recovery rate in group 3 was higher than group 1 (48.8% vs. 26.8%, p = .00), but lower than group 5 (48.8% vs. 76.5%, p = .025). The percentage of grade A COCs in group 3 was higher than group 2 (59.3% vs. 39.5%, p = .00) and group 1 (59.3% vs. 26.7%, p = .00). Moreover, the percentage of grade A COCs in group 4 (55.0%, p = .710) and group 5 (46.2%, p = .351) was reduced compared with that in group 3. From the above results, the developing follicles (group ovum pick-up [OPU], 10-20 mm) and preovulation follicles (group OPU-Preov, >35 mm) were aspirated from live jennies using OPU. Although there was no difference in the recovery rates of COCs between group 3 and OPU (48.8% vs. 43.0%, p = .184), the percentage of grades A COCs in group OPU was higher than group 3 (72.5% vs. 59.3%, p = .036). There was no difference in the maturation rate between group 3 and OPU (60.3% vs. 69.3%, p = .171) after the COCs matured in vitro. The rates of recovery (72.2%) and maturation (92.3%) in group OPU-Preov were higher than those in other groups (p < .05). Moreover, the effects of maturation time and serum type on maturation rates were evaluated in groups B44 (44 h, FBS), B36 (36 h, FBS) and D44 (44 h, foetal donkey serum, FDS). These results indicated that the maturation rate in group B36 was lower than group B44 (13.1% vs. 47.0%, p = .00) and group D44 (13.1% vs. 53.3%, p = .00). In conclusion, the quality of donkey COCs from OPU was higher than that from abattoir-derived ovaries, the suitable time of donkey in vitro maturation (IVM) was 44 h, and FBS could be replaced with FDS in donkey IVM medium.

Recovery of Equine Oocytes in Ambulatory Practice and Potential Complications

Field collection of oocytes in mares using transvaginal follicular aspiration (TVA) for embryo production has the potential to revolutionate the equine industry. Protocols for TVA in specialized laboratory settings have been described in the scientific literature since the early 1980s. The objective of this study was to determine the success rate of TVA oocytes recovery under ambulatory conditions. A secondary goal of this study was to determine if TVA is associated with any health complications when performed by recently trained practitioners in the field. Follicles (n = 296) from 66 adult clinically healthy mares were aspirated over a period of 6 days. TVAs were performed by 22 veterinarians with 5-20 years of experience in equine and bovine reproductive medicine, but no previous experience in TVA. Oocytes (n = 145) were recovered. No short- or long-term systemic or local complications were observed following TVA in any of the mares used in this study. Fifty-six out of 66 mares became pregnant within 3 months following TVA. This study shows that with proper training, TVA can be successfully used to obtain equine oocytes with no health complications under field conditions in nonspecialized laboratory settings.

Influence of transvaginal ultrasound-guided follicular punctures in the mare on heart rate, respiratory rate, facial expression changes, and salivary cortisol as pain scoring

Transvaginal ultrasound-guided follicular punctures are widely used in the mare for diagnosis, research, and commercial applications. The objective of our study was to determine their influence on pain, stress, and well-being in the mare, by evaluating heart rate, breath rate, facial expression changes, and salivary cortisol before, during, and after puncture. For this experiment, 21 pony mares were used. Transvaginal ultrasound-guided aspirations were performed on 11 mares. After injections for sedation, analgesia, and antispasmodia, the follicles from both ovaries were aspirated with a needle introduced through the vagina wall into the ovary. In the control group, 10 mares underwent similar treatments and injections, but no follicular aspiration. Along the session, heart rate and breath rate were evaluated by a trained veterinarian, ears position, eyelid closure, and contraction of facial muscles were evaluated, and salivary samples were taken for evaluation of cortisol concentration. A significant relaxation was observed after sedative injection in the punctured and control mares, according to ear position, eyelid closure, and contraction of facial muscles, but no difference between punctured and control animals was recorded. No significant modification of salivary cortisol concentration during puncture and no difference between punctured and control mares at any time were observed. No significant modification of the breath rate was observed along the procedure for the punctured and the control mares. Heart rate increased significantly but transiently when the needle was introduced in the ovary and was significantly higher at that time for the punctured mares than that for control mares. None of the other investigated parameters were affected at that time, suggesting discomfort is minimal and transient. Improving analgesia, e.g., through a multimodal approach, during that possibly more sensitive step could be recommended. The evaluation of facial expression changes and heart rate is easy-to-use and accurate tools to evaluate pain and well-being of the mare.

Advances in Collection, Transport and Maturation of Equine Oocytes for Assisted Reproductive Techniques

Assisted reproductive techniques that are based on oocyte manipulations have gained acceptance in the equine industry. Methods to collect and handle immature or maturing oocytes have been developed, and systems to ship oocytes now allow for collection in one location and intracytoplasmic sperm injection (ICSI) in another. Subsequently, ICSI-produced embryos can be transferred onsite, shipped to another location, or cryopreserved. Methods for the collection, identification, culture, maturation, and shipment of equine oocytes are reviewed, with an emphasis on procedures from laboratories providing clinical services with documented success.

Expression profiles of select genes in cumulus–oocyte complexes from young and aged mares

There is compelling evidence that oocytes from mares >18 years of age have a high incidence of inherent defects that result in early embryonic loss. In women, an age-related decrease in oocyte quality is associated with an increased incidence of aneuploidy and it has recently been determined that the gene expression profile of human oocytes is altered with advancing age. We hypothesised that similar age-related aberrations in gene expression occur in equine oocytes. Therefore, the aim of the present study was to compare gene expression profiles of individual oocytes and cumulus cells from young and aged mares, specifically evaluating genes that have been identified as being differentially expressed with advancing maternal age and/or aneuploidy in human oocytes. Expression of 48 genes was compared between 14 cumulus–oocyte complexes (COCs) from mares aged 3–12 years and 10 COCs from mares ≥18 years of age. Three genes (mitochondrial translational initiation factor 3 (IF3), heat shock transcription factor 5 (HSF5) and Y box binding protein 2 (YBX2)) were differentially expressed in oocytes, with all being more abundant in oocytes from young mares. Three genes (ADP-ribosylation factor-like 6 interacting protein 6 (ARL6IP6), BCL2-associated X protein (BAX) and hypoxia upregulated 1 (HYOU1)) were differentially expressed in cumulus cells, with all being more abundant in aged mares. The results of the present study confirm there are age-related differences in gene expression in equine COCs, which may be associated with the lower quality and decreased developmental competence of oocytes from aged mares.

Ovum pick up, intracytoplasmic sperm injection and somatic cell nuclear transfer in cattle, buffalo and horses: from the research laboratory to clinical practice

Assisted reproductive techniques developed for cattle in the last 25 years, like ovum pick up (OPU), intracytoplasmic sperm injection (ICSI), and somatic cell nuclear transfer, have been transferred and adapted to buffalo and horses. The successful clinical applications of these techniques require both the clinical skills specific to each animal species and an experienced laboratory team to support the in vitro phase of the work. In cattle, OPU can be considered a consolidated technology that is rapidly outpacing conventional superovulation for embryo transfer. In buffalo, OPU represents the only possibility for embryo production to advance the implementation of embryo-based biotechnologies in that industry, although it is still mainly in the developmental phase. In the horse, OPU is now an established procedure for breeding from infertile and sporting mares throughout the year. It requires ICSI that in the horse, contrary to what happens in cattle and buffalo, is very efficient and the only option because conventional IVF does not work. Somatic cell nuclear transfer is destined to fill a very small niche for generating animals of extremely high commercial value. The efficiency is low, but because normal animals can be generated it is likely that advancing our knowledge in that field might improve the technology and reduce its cost.

Characterization of matrix metalloproteinase-2 and matrix metalloproteinase-9 and their inhibitors in equine granulosa cells in vivo and in vitro

Matrix metalloproteinases (MMP) and tissue inhibitors of MMP (TIMP) regulate tissue remodeling events necessary for ovulation. Thus, changes in MMP and TIMP expression and protein enzyme activity were examined in vivo and in vitro during follicular development and atresia in the horse. Equine granulosa cells and follicular fluid from medium (15 to 29 mm) healthy and atretic follicles and from large (>30 mm) healthy and preovulatory follicles were collected by transvaginal aspiration. The cells were either snap-frozen (in vivo study) or cultured for 48 h (in vitro study) to determine gene expression and protein enzyme activity of MMP-2 and MMP-9 and TIMP-1 and TIMP-2. Concentrations of progesterone and estradiol were determined by RIA in follicular fluid and conditioned media and were used along with follicle dynamics to classify follicles. In vivo, expression of MMP-2 and TIMP-2 was increased (P < 0.05) in large-preovulatory follicles, whereas TIMP-1 was decreased. The ratio of MMP-2:TIMP-2 expression was decreased (P < 0.05) in medium-healthy and large-preovulatory follicles, whereas the MMP-9:TIMP-1 ratio was increased only in large-preovulatory follicles compared with large-healthy follicles. Estradiol was greatest (P < 0.05) in the fluid of large-healthy and large-preovulatory follicles. However, medium-atretic follicles were associated with the least estradiol concentrations, both in vivo and in vitro. Progesterone concentrations were greatest (P < 0.05) in large-preovulatory follicles both in vivo and in vitro. In healthy follicles in vivo, the diameter was correlated with estradiol concentration, the estradiol:progesterone ratio, MMP-9 and TIMP-1 expression, and MMP-2 and MMP-9 protein activity. In contrast to in vivo studies, the ratio of MMP-9:TIMP-1 expression was increased (P < 0.05) in medium-healthy follicles; TIMP-2 expression decreased in large-preovulatory follicles in vitro. In addition, MMP-9 protein activity was decreased (P < 0.05) in the media samples of cells from large-healthy follicles compared with those from medium-healthy follicles. These results indicate that changes in MMP-2 and MMP-9 activities may be essential to the tissue reorganization necessary for ovulation in the equine ovary.

Ovulation synchronization following commercial application of ultrasound-guided follicle ablation during the estrous cycle in mares

A regimen of progesterone plus estradiol (P&E) was used as a standard for ovarian synchronization to test the efficacy and evaluate the commercial application of ultrasound-guided follicle ablation as a non-steroidal alternative for ovulation synchronization in mares. Recipient mares at a private embryo transfer facility were at unknown stages of the estrous cycle at the start of the experiment on Day 1 when they were randomly assigned to an ablation group (n=18-21 mares) or to a P&E group (n=20-21 mares). In the ablation group, mares were lightly sedated and all follicles > or = 10 mm were removed by transvaginal ultrasound-guided follicle aspiration. In the P&E group, a combination of progesterone (150 mg) plus estradiol (10mg) prepared in safflower oil was given daily (im) for 10 d. Two doses of prostaglandin F(2alpha) (PGF, 10mg/dose, im) were given 12 h apart on Day 5 in the ablation group, or a single dose on Day 10 in the P&E group. Human chorionic gonadotropin (hCG, 2500 IU/mare, im) was given at a fixed time, 6 and 10 d after PGF treatment in the ablation and P&E groups, respectively, with the expectation of a follicle > or = 30 mm at the time of treatment. In both the ablation and P&E groups, transrectal ultrasonography was done at the start of the study (Day 1) and again on the day of hCG treatment and daily thereafter to determine the presence of a CL, measure diameter of the largest follicle and detect ovulation. The mean interval from the start of the study and from PGF treatment to ovulation was shorter (P<0.0001) in the ablation group (13.7 and 9.7 d, respectively) compared to the P&E group (22.3 and 13.2 d, respectively). Following fixed-day treatment with hCG after PGF treatment, the degree of ovulation synchronization was not different (P>0.05) between the ablation and P&E groups within a 2-d (56 and 70%) or 4-d (83% and 90%) period. Although ultrasound-guided follicle ablation may not be practical in all circumstances, it excluded the conventional 10-d regimen of progesterone and estradiol and was considered an efficacious and feasible, non-steroidal alternative for ovulation synchronization in mares during the estrous cycle.

Aspiration of oocytes from transitional, cycling, and pregnant mares

The aim of this study was to compare the efficacy of three approaches for recovering equine oocytes via transvaginal ultrasound-guided follicular aspiration. Fourteen mares were used as oocyte donors during the spring transition period and physiologic breeding season, and 11 mares were bred for use as oocyte donors during early gestation. In all mares, large (>20 mm) and small (10-20 mm) follicles were aspirated in eight rounds every 10-11 days. In each of the four rounds during the transition period, half the mares received 12.5 mg eFSH once daily for 4 days prior to aspiration. For each of the four rounds during the cycling season, half the mares received 12.5 mg eFSH twice daily for 3 days prior to aspiration. Pregnant mares were aspirated on days 25, 40 and 55 of gestation and received no eFSH. There were more large (>20 mm) follicles in cycling controls (2.25+/-0.27) and cycling FSH-treated (2.64+/-0.27) mares than in transitional FSH-treated mares (1.18+/-0.27). The number of oocytes recovered from small (10-20 mm) follicles varied by mare (P<0.05) and averaged 1.08+/-0.22 per aspiration for transitional mares and 1.23+/-0.22 per aspiration for cycling mares (P>0.1). The number of oocytes per aspiration from large follicles was greater in cycling FSH-treated mares (0.46+/-0.09) than in transitional control mares (0.11+/-0.09). In pregnant mares, more large follicles were present at day 25 than at any other time, and the number of oocytes per aspiration from large follicles was greater at day 25 (0.73+/-0.16) than at day 55 (0.04+/-0.18). When compared across all seasons and treatments, the day 25 pregnant mares yielded the greatest number of oocytes per aspiration (2.91+/-0.66 per mare).

Developmental competence of equine oocytes and embryos obtained by in vitro procedures ranging from in vitro maturation and ICSI to embryo culture, cryopreservation and somatic cell nuclear transfer

Development of assisted reproductive technologies in horses has been relatively slow compared to other domestic species, namely ruminants and pigs. The scarce availability of abattoir ovaries and the lack of interest from horse breeders and breed associations have been the main reasons for this delay. Progressively though, the technology of oocyte maturation in vitro has been established followed by the application of ICSI to achieve fertilization in vitro. Embryo culture was initially performed in vivo, in the mare oviduct or in the surrogate sheep oviduct, to achieve the highest embryo development, in the range of 18-36% of the fertilised oocytes. Subsequently, the parallel improvement of in vitro oocyte maturation conditions and embryo culture media has permitted high rates of embryo development from in vitro matured and in vitro cultured ICSI embryos, ranging from 5 to 10% in the early studies to up to 38% in the latest ones. From 2003, with the birth of the first cloned equids, the technology of somatic cell nuclear transfer has also become established due to improvement of the basic steps of embryo production in vitro, including cryopreservation. Pregnancy and foaling rates are still estimated based on a small number of in vitro produced equine embryos transferred to recipients. The largest set of data on non-surgical embryo transfer of in vitro produced embryos, from ICSI of both abattoir and in vitro-matured Ovum Pick Up (OPU) oocytes, and from somatic cell nuclear transfer, has been obtained in our laboratory. The data demonstrate that equine embryos produced by OPU and then cryopreserved can achieve up to 69% pregnancy rate with a foaling rate of 83%. These percentages are reduced to 11 and 23%, respectively, for cloned embryos. In conclusion, extensive evidence exists that in vitro matured equine oocytes can efficiently develop into viable embryos and offspring.