Electroejaculation and semen characteristics of Asiatic Black bears (Ursus thibetanus)

Evaluation of pharmacological alternatives to reduce the pain and discomfort produced by electroejaculation in rams

Electroejaculation (EE) represents the main technique for semen collection from domestic and wild animals independently of libido. However, the technique is associated with intense involuntary muscle contractions, vocalization, ataxia and lying down, caused by the electric stimulation of the nerves in the caudal epigastric region. These clinical manifestations represent important indicators of discomfort. In this context, the objective of this study was to evaluate two protocols of local anaesthetic blockade and two anatomical access for pharmacological desensitization of the caudal epigastric innervation as alternatives to promote comfort and reduce stress associated with EE in rams. For the study, four clinically healthy Dorper rams were selected. All animals were subjected to a design consisting of five semen collection treatments (n = 3 collections per treatment): T1-control, conventional EE without local anaesthetic blockade; T2, EE with ventral blockade (VB) of epigastric innervation using lidocaine hydrochloride 2%; T3, EE with VB of epigastric innervation using a combination of lidocaine hydrochloride 2% and fentanyl citrate; T4, EE with blockade of epigastric innervation through the perineal access using lidocaine hydrochloride 2%; T5, EE with blockade of epigastric innervation through the perineal access using a combination of lidocaine hydrochloride and fentanyl citrate. Seminal samples resulting from EE were subjectively evaluated for sperm motility and concentration, vigour and volume. Additionally, blood serum samples were collected for quantification of cortisol and creatine kinase (CK) enzyme. Assessments of stress and discomfort were conducted by measuring blood pressure, heart rate (HR) and respiratory rate (RR), as well as observing involuntary muscle contractions, ataxia and animal vocalization. No variations in blood pressure, sperm motility, vigour, CK, and cortisol were observed among the treatments. Individual variations were observed for the occurrence of vocalization (p = .0066), but there were no differences between the groups. Anaesthetic blockades conducted using the combination of lidocaine and fentanyl resulted in a lower incidence of ataxia during EE (p < .0001). It is concluded that the combination of fentanyl citrate and lidocaine hydrochloride results in less discomfort for animals undergoing EE, regardless of the anatomical access used for local anaesthetic blockades.

Current knowledge in the biology of gametes and embryos from Carnivora

In addition to companion animals and laboratory species, about 270 carnivore species play fundamental ecological roles in different ecosystems. However, almost 40% of carnivore species are now threatened or endangered in the wild because of human activities. While protection of natural habitats is critical, it is equally important to better understand carnivore reproduction, including a solid knowledge in sperm, oocyte, and embryo biology, to maintain sustainable populations in the wild and in conservation breeding centers. Characterizing gamete and embryo biology is also needed to develop cryopreservation and assisted reproductive technologies to enhance conservation efforts. The objective of this review is to provide the most recent knowledge in the biology of sperm cells, oocytes, and early embryos across all carnivore families. Overall, most data originate from populations maintained in breeding centers or zoos. Characterizations of sperm biology and cryopreservation are far more advanced than for oocytes and embryos. Currently, sperm biology is mainly studied in Canids, Felids, Ursids, and Mustelids, with more emphasis on structural than functional properties. Importantly, fundamental studies of gamete and embryo biology in domestic dogs, cats, and ferrets have paved the way for more precise characterizations in wild counterparts as well as the development of cryopreservation and assisted reproductive technologies. A striking feature of spermatozoa across a wide range of Canids and Felids is the presence of teratospermia (>60% of abnormal sperm cells), which is related to the loss of genetic diversity in some populations. Although sperm structures differ across carnivore families, sperm biology remains difficult to compare because of the small amount of data in many species. Regarding oocyte biology and embryology, data are much scarcer than in sperm cells, with too few studies going beyond structural descriptions. More carnivore species and more individuals (especially from wild populations in addition to captive ones) must be studied to improve our understanding about comparative germplasm biology and develop adequate conservation breeding strategies including the use of cryobanking and assisted reproductive technologies.

Case Studies in Polar Bear (Ursus maritimus) Sperm Collection and Cryopreservation Techniques

Simple Summary

Polar bears are threatened by habitat loss, decreased food availability, and reduced reproductive success due to climate change. Zoo populations can support species survival through preservation of genetic diversity and maintenance of insurance populations, but in the US, the zoo polar bear population is currently not sustainable. The development of sperm collection and cryopreservation can help to support the population by providing the biomaterial needed for assisted reproductive techniques, such as artificial insemination. However, these procedures are not well described for polar bears. Data from 38 opportunistic sperm collections, that were conducted between 2011 and 2021, were assessed to establish best practices to date for collecting and preserving polar bear sperm. The information gathered demonstrates that urethral catheterization is an efficient method of sperm collection, sperm can be rescued postmortem from the vasa deferentia and epididymides, and polar bear sperm collection appears to be most effective during the breeding season. Furthermore, polar bear sperm can survive cryopreservation. Further studies will optimize these techniques, but this summary provides information that is immediately applicable to enhancing sample collection and cryopreservation success that could support the long-term genetic management of polar bears in zoos.

Abstract

Assisted reproductive technologies can aid conservation efforts via support of ex situ population management and preservation of genetic material. Data from 38 sperm collection attempts from 17 polar bears (1–5 procedures/bear) were evaluated. Sample collections were attempted via electroejaculation (EEJ; n = 6), urethral catheterization (UC; n = 25), or sperm rescue (SR; n = 7) during the breeding season (Jan. 1-May 21; n = 27) and nonbreeding season (May 22-Dec. 31; n = 11). Sperm retrieval was successful in 1 EEJ (16.7%), 18 UC (72.0%) and 4 SR (57.1%) collections. Initial sperm motility and viability were 50.0% and 77.0% for EEJ, 64.3 ± 7.4% and 80.9 ± 3.8% for UC, and 56.7 ± 8.8% and 80.5 ± 0.5% for SR. UC and SR were more likely to be successful during the breeding season (84.2–100%) than the nonbreeding season (25.0–33.3%). Testicular tumors were observed in four males (57%) during SR. In total, 13 samples were cryopreserved (n = 1 EEJ, 9 UC, and 3 SR) with egg-yolk-based equine extender (EQ) or OptiXcell (OP). For both extenders, post-thaw motility and viability were reduced by 20–60% and 30–65%, respectively. Further efforts to optimize procedures are warranted, but this summary provides data useful for enhancing the success of polar bear sperm collection and cryopreservation.

Effectiveness of urethral catheterization under ultrasound guidance for semen collection from Asiatic black bears (Ursus thibetanus)

The Asiatic black bear (ABB; Ursus thibetanus ussuricus) is a globally endangered species, and measures to help increase their population are necessary. For the successful restoration of this species, artificial breeding as well as conservation translocation are considered important. The aims of the present study were to evaluate the feasibility and effectiveness of urethral catheterization (UC), which is effectively used in feline species, for semen collection from ABBs and establish the optimal protocol for semen collection via this technique. Seven clinically healthy, adult male ABBs (age, 6-13 years; weight, 130-180 kg) housed at the Species Restoration Technology Institute, Korea were included in this study. All study procedures were performed during the breeding season (June to August) over 3 consecutive years. Semen samples were collected once or three times from all bears by ultrasound-guided UC or electroejaculation (EE) under general anesthesia, and their characteristics, including sperm motility, were evaluated. The day of semen collection was defined as Day 0. The semen collected by the UC method was stored at 4 °C, and sperm motility was evaluated at the same time every day for 16 days. The successful collection rates for the UC and EE methods were 92.3% and 53.8%, respectively. The sperm concentration (4718.9 ± 1526.1 vs. 185.0 ± 34.2 × 10⁶/ml), total sperm count (1196.6 ± 955.5 vs. 100.9 ± 70.0 × 10⁶), sperm motility score (4.39 ± 0.78 vs. 3.00 ± 1.73), viability (98.2 ± 2.3 vs. 82.7 ± 19.6), and the proportion of spermatozoa with intact acrosomes (92.2% ± 9.3% vs. 75.6% ± 10.6%) were higher with the UC method than with the EE method, whereas the proportion of spermatozoa with an abnormal morphology (23.1% ± 4.6% vs. 45.6% ± 19.5%) was lower with the former than with the latter. Over the course of cool storage, there was an overall decrease in the total motility, progressive motility, and viability, although viability was >50% until Day 10. These findings suggest that ultrasound-guided UC is a useful and feasible tool for the collection of high-quality semen from ABBs. The collected semen remains viable for up to 10 days, with high sperm motility maintained for up to 7 days, when stored at 4 °C.

Salvaging urospermic ejaculates from brown bear (Ursus arctos)

The objective of this study was to reverse the osmotic stress of sperm in urine contaminated bear ejaculates that were obtained by electroejaculation using pre-freezing washing or density gradient centrifugation isolation. In Experiment 1, ejaculates were divided into six aliquots, five were diluted in each washing extender: 200, 300, 400, 500 and 700 mOsm/kg (prepared from a Tes-Tris-Fructose base, adding water or fructose as corresponds), at a 1:2 ratio (raw semen: washing solution, v/v); and the other aliquot was handled without washing (Control group). Samples were centrifuged at 600 × g for 6 min prior to freezing. In Experiment 2, ejaculates were divided into two aliquots: one was diluted 1:1 with TCG (Tris-Citric acid-Glucose) and centrifuged at 600 × g for 6 min (Centrifugation Control; C-Control); the other was treated with PureSperm density gradient column. After treatments, samples were cryopreserved. Sperm motility, viability (SYBR-14/propidium iodide (PI)) and acrosomal status (peanut agglutinin-fluorescein isothiocyanate (PNA-FITC)/PI) were analyzed before and after freezing. Ejaculates with an initial osmolality of less than 120 mOsm/kg treated with pre-freezing washing, and the Control sample had greater pre-freezing sperm motility than the raw ejaculate, but sperm viability was not different among these groups. The samples washed with 700 mOsm/kg solutions had the least pre-freezing viability. In the post-thawing evaluation, pre-freezing washing treatments did not provide any improvement in comparison with the Control sample, and treatment with 700 mOsm/kg extender had deleterious effects in all urospermic samples. PureSperm density gradient centrifugation applied to urospermic raw semen was suitable for improving sperm motility and viability of pre-freezing samples and the selected spermatozoa had greater freezing capacity.