Ovarian function and morphology in the mare after multiple follicular punctures

Resolution of two cases of ovarian abscesses in mares subjected to ovum pick up

BACKGROUND

Currently, for in vitro embryo production in live mares, immature oocytes are retrieved by transvaginal follicular aspiration or ovum pick up (OPU). Occasionally, ovarian abscesses have been described after OPU, but no current consensus exists on how to treat this condition.

OBJECTIVES

To describe diagnosis and successful treatment of ovarian abscesses in two mares subjected to OPU.

STUDY DESIGN

Case report.

METHODS

Case records were reviewed and summarised.

RESULTS

In the first case, a pony mare showed tachypnoea, tachycardia, high temperature, leukocytosis, left hindlimb lameness and slight increase in concentration of serum amyloid A. Ultrasonography revealed an increase in the size of the left ovary and two well defined structures suggestive of ovarian abscess. A left ovariectomy by standing laparoscopy was the treatment of choice: the diagnosis was confirmed, and bacterial culture produced heavy growth of Streptococcus equi Zooepidemicus. In the second mare, an abnormal structure was observed in the left ovary in a routine transrectal ultrasonographic exam in the absence of any clinical signs or abnormal blood parameters. A medical approach was chosen and a sample of the purulent material was aspirated with a transvaginal ultrasound-guided approach. The sample yielded a heavy growth of Streptococcus equi Zooepidemicus after culture. Treatment was initiated with rifampicin and trimethoprim-sulfadiazine based on the antibiogram results and the abscess completely resolved after 40 days.

MAIN LIMITATIONS

Limited to two cases.

CONCLUSIONS

Ovarian abscesses in mares can be successfully treated both surgically and medically.

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.

Clinical Application of in Vitro Embryo Production in the Horse

The first reports of in vitro embryo production (IVEP) by conventional in vitro fertilization and intracytoplasmic sperm injection in horses date respectively from approximately 30 and 25 years ago. However, IVEP has only become established in clinical practice during the last decade. The initial slow uptake of IVEP was largely because the likelihood of success was too low to make it an economically viable means of breeding horses. During the last decade, the balance has shifted, primarily because of significant improvements in the efficiency of recovering immature oocytes from live donor mares (historically <25%; now >50%) and in the successful culture of zygotes to the blastocyst stage in vitro (historically <10%; now >20%). It has also been established that immature oocytes can be "held" at room temperature for at least 24 hours, allowing overnight transport to a laboratory with expertise in IVEP. Moreover, because in vitro-produced embryos can be cryopreserved with no appreciable reduction in viability, they can be shipped and stored until a suitable recipient mare is available for transfer. Most importantly, in an established equine ovum pick-up intracytoplasmic sperm injection (OPU-ICSI) program, blastocyst production rates now exceed 1 per procedure, and posttransfer foaling rates exceed 50%, such that overall efficiency betters that of either embryo flushing or oocyte transfer. Moreover, OPU-ICSI can be performed year round and allows embryo production from mares with severe acquired subfertility and extremely efficient use of scarce or expensive frozen semen. Cumulatively, these factors have stimulated rapid growth in demand for IVEP among sport horse breeders.

Use of different pressures for transvaginal follicular aspiration in mares

ABSTRACT The success of transvaginal follicular aspiration in mares can be influenced by several factors, such as vacuum pump pressure levels. The present study aimed to investigate the effect of different negative pressures (150, 280 and 400mmHg) of the vacuum pump on the oocyte recovery in the mares. The mares (n=10) were undergoing follicular aspiration using three different negative pressures for three consecutive estrous cycles as follows: G150 = 150mmHg (n = 10); G280 = 280mmHg (n = 10); G400 = 400mmHg (n = 10). Every estrous cycle, the group that the mare would participate was drawn, and each animal participated once in each group. Only preovulatory follicle was used, about 30 to 36 hours after application of hCG. To compare the results, the chi-square test was used (5% significance) and Fisher exact test, when recommended. Thirty preovulatory follicles (diameter 36.1±1.80mm) were aspirated and ten oocytes were recovered (33.3%). There was no statistical difference between the experimental groups (p=0.59). Thus, accord to the results observed in this study, we could conclude that the negative pressure of the vacuum pump used was not efficient to increase oocyte recovery.

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.

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.

Embryo technologies and animal health – consequences for the animal following ovum pick-up, in vitro embryo production and somatic cell nuclear transfer

Mammalian reproductive technologies that aim either to complement or to transcend conventional livestock breeding options have contributed to some of the most remarkable achievements in the field of reproductive biology in recent decades. In so doing they have extended our horizons in two distinct dimensions, the first concerning what it is technically possible to achieve and the second relating to the time-frame within which an individual's life-long developmental capability is initially established and ultimately realized or undermined. Our impressions of the benefits and values, or otherwise, of technologies such as in vitro embryo production and nuclear transfer are rightly influenced by the extent to which they impinge on the health of animals either subjected to or derived from them. Here, we consider some of the health implications of oocyte/embryo-centric technologies applied to farm livestock.

Fertility in the mare after repeated transvaginal ultrasound-guided aspirations

Ovum pick-up (OPU) by transvaginal ultrasound guided aspiration (TUGA) is a procedure applied in equine-assisted reproduction programs such as oocyte transfer and in vitro embryo production. Despite a large number of studies reporting that it is a repeatable and safe technique, little information is available about the effect of repeated punctures on fertility of mares. Moreover, even if flushing follicles improves the oocyte recovery rate, to our knowledge the efficiency of flushing estrous and diestrous follicles has not been evaluated. The aims of the present study were (1) evaluate if repeated TUGAs negatively effects fertility and (2) investigate the influence of flushing the follicular cavity (as compared to aspiration only-unflushed) on the recovery rate from follicles of different sizes and in different stages of the estrous cycle. Seventy-six TUGAs were carried out on 20 mares during the breeding season; 153 follicles were aspirated and 31 oocytes were recovered (20.3% per follicle; 40.8% per TUGA attempt). Of the 76 aspirations, 52 were carried out during estrus and 24 in diestrus. Flushing the follicular cavity significantly increased (P < 0.01) the oocyte recovery rate from estrous follicles (13/28, 46.4% flushed versus 3/24, 12.5% aspirated only) but not (P > 0.05) from diestrous follicles of different diameters (3/30, 10% flushed versus 2/36, 5.6% aspirated only for follicles <2 cm in diameter; 6/20, 30% flushed versus 4/15, 26.7% aspirated only for follicles > or =2 cm in diameter). Mares underwent ultrasonic examinations after every aspiration and no alteration was found with the exception of two mares in which the corpus luteum (CL) did not form following aspiration of estrous follicle. Of the 20 mares involved in this study, 10 were artificially inseminated with fresh semen from a single fertile stallion at the first spontaneous heat following the previous aspiration. Of the 10 inseminated mares, 7 were found to be pregnant 16, 30 and 50 days after artificial insemination (AI), indicating that repeated TUGAs did not adversely affect fertility.

Integrating new technologies with embryology and animal production

The present review describes a range of selected farm animal embryo technologies used in embryological research and applied in animal breeding and production. Some of the techniques are driven by the breeder’s wish to obtain animals with higher breeding values, whereas others are primarily driven by the curiosity of researchers. The interaction between basic research and practical application in these areas is still a characteristic feature for people who contribute to the International Embryo Transfer Society (IETS) and has been an advantage for both researchers and breeders. One example of such an interaction is that detailed structural analyses have described quality differences between embryos of various origins and, following embryo transfer, the pregnancy results have confirmed the correlation between morphology and viability. Another example is that polymerase chain reaction technology has allowed detection of Y-specific sequences in male embryos and has become a tool in animal production today. Data from domestic animal genome sequencing will provide a great deal of new information. A major challenge for the years to come will be using this information in a physiologically meaningful context and to continue the efforts to convert the laboratory experience into use in practise. Finally, it is important to obtain societal acceptance for a wider application of many of the technologies, such as in vitro embryo production and cloning.