Comparison of different sperm cryopreservation procedures on post-thaw quality and heterologous in vitro fertilisation success in the ocelot (Leopardus pardalis)

Assessment of thawed sperm quality from feline species: Ocelot (Leopardus pardalis) and oncilla (Leopardus gutullus)

This study aimed to evaluate the cryopreservation effects on the semen of oncilla (Leopardus guttulus, n = 5, 15 ejaculates) and ocelot (Leopardus pardalis, n = 5, 17 ejaculates) and compare two extenders (commercial and non-commercial extender). An andrological exam was conducted (testicle measurements and penis evaluation), including semen collection by electroejaculation. After collection, the semen was assessed to volume, color, pH, sperm motility, vigor, sperm number in the ejaculate, viability, membrane integrity, and sperm morphology. Samples were centrifuged (300 g for 10 min) and pellet diluted in two extenders (TRIS/glucose/egg yolk and BotuCRIO®), packed into 0.25 mL French straws (20 × 10⁶ spermatozoa/mL), equilibrated at 5 °C for 1 h (<0.5 °C/min), freezing in nitrogen vapor for 20 min. Thawing was achieved at 46 °C for 15 min. Thawed samples were evaluated to the same characteristics and ultrastructural analysis. There is no difference for extenders, but in ocelot the spermatozoa maintained higher quality after thawing. Major defects were increased in thawed samples, especially acrosome injuries, in both species. Semen contamination by urine was remarkable to oncilla (53% of the ejaculates) which can have reduced sperm cryoresistance of this species. Ultrastructural analysis endorsed morphological analysis under light microscopy and identified cells with acrosome vesiculation. In conclusion, the spermatozoa of ocelot were more cryoresistent and the extender commercial and non-commercial were suitable for their cryopreservation. Other extenders should be investigated for oncilla.

Heterologous in vitro fertilization and embryo production for assessment of jaguar (Panthera onca Linnaeus, 1758) frozen-thawed semen in different extenders

Heterologous in vitro fertilization (IVF) is an important tool for assessing fertility of endangered mammals such as the jaguar, considering difficult access to females for artificial insemination and to obtain homologous oocytes. We aimed to evaluate the fertility of jaguar sperm cryopreserved with different extenders, using domestic cat oocytes to assess the development of hybrid embryos. Semen from four captive jaguars was obtained by electroejaculation. Samples were cryopreserved in powdered coconut water (ACP-117c) or Tris extender containing 20% egg yolk and 6% glycerol. Thawed spermatozoa were resuspended (2.0 × 10⁶ spermatozoa/mL) in IVF medium and co-incubated with cat oocytes matured in vitro for 18 h. Presumptive zygotes were cultured for 7 days. After 48 h, cleavage rate was evaluated, and non-cleaved structures were stained for IVF evaluation. On days 5 and 7, the rate of morula and blastocyst formation was assessed. Data were analyzed using the Fisher exact test (p < 0.05). No difference was observed between ACP-117c and Tris extenders, respectively, for oocytes with 2nd polar body (2/51, 3.9 ± 2.9% vs. 2/56, 3.6 ± 3.1%), pronuclear structures (5/51, 9.8 ± 4.7% vs. 8/56, 14.3 ± 8.0%), and total IVF rates (7/36, 19.4 ± 5.0% vs. 10/37, 27.0 ± 13.8%). All the samples fertilized the oocytes, with 22.9 ± 3.2% (16/70) and 16.7 ± 3.6% (12/72) cleavage of mature oocytes for ACP-117c and Tris extenders, respectively. Morula rates of 4.3 ± 2.3% (3/70) and 5.6 ± 2.2% (4/72) were observed for ACP-117c and Tris, respectively. Only the Tris extender demonstrated blastocyst production (2/12, 16.7 ± 1.5% blastocyst/cleavage). We demonstrated that jaguar ejaculates cryopreserved using ACP-117c and Tris were suitable for IVF techniques, with blastocyst production by ejaculates cryopreserved in Tris. This is a first report of embryos produced in vitro using jaguar sperm and domestic cat oocytes through IVF.

Sperm evaluation and morphological description of male genitalia of meerkats (Suricata suricatta)

In ex situ conditions, little is known about the reproductive biology of meerkats. The aim of present study was to describe the morphological aspects of male genital organs and accessory glands using macroscopic evaluation, ultrasonography, and radiography, as well as describing semen characteristics post-electroejaculation. The results indicated anatomical characteristics of meerkats are very similar to those of cats, having a prostate, accessory bulbourethral glands, and an elongated and radiopaque structure in the penis, which is indicative of there being a baculum. The testicular volume was 0.81 cm³ (± 0.10) and the relative testis weight was 1.37 cm³/kg (± 0.15). Both testicles are present in the scrotum, which has an ellipsoidal shape, homogeneous texture, hypoechoic parenchyma and are encased in a hyperechoic tunica albuginea. Electroejaculation was effectively induced in all animals for semen collection with utilization of medetomidine and ketamine. The values semen samples variables were as follows for volume - 0.125 ± 0.193 mL, motility - 19.8 ± 18.6 %, vigor - 1.9 ± 1.0, concentration - 40.5 ± 25.2 × 10⁶ sperm/mL and morphologically normal sperm - 10.8 ± 6.6 %. This is the first study in which there is a description of morphological and imaging aspects of the male reproductive tracts of meerkats, as well as the seminal characteristics after using electroejaculation for semen collection. Knowledge of anatomical and seminal characteristics is essential for implementation of assisted reproduction programs, as well as reproductive management in the species.

Assisted reproductive technologies for endangered species conservation: developing sophisticated protocols with limited access to animals with unique reproductive mechanisms

Assisted reproductive technologies (ARTs) have been proposed as a means of overcoming the significant challenges of managing small, isolated populations of endangered species in zoos. However, efficient protocols for ARTs do not exist for most endangered species. This review will focus on research efforts to characterize unique reproductive mechanisms and develop species-specific ARTs. Central to these studies are assays to measure steroid metabolites in urine or feces and/or training programs to allow unrestrained blood collections and ultrasound evaluations. The resulting information about estrous cycle dynamics, combined with studies of semen collection and processing, provides the foundation for the development of artificial insemination (AI). In vitro fertilization and embryo transfer are also discussed in relation to the advantages these techniques could provide relative to AI, as well as the significant challenges involved with technologies that require oocytes and embryos. Finally, an argument is made for additional research of nontraditional model species (e.g., domestic cats and dogs) and the development of novel models representing unique taxa. Whether these species are studied by zoo-based researchers with the expressed intent of developing ARTs for conservation or academic scientists interested in basic biology, the resulting information will provide a unique, evolutionary perspective on reproduction that could have wide-reaching benefits. The more information we have available, the better our chances will be of developing effective ARTs and making a difference in conservation efforts for endangered species.

Cryopreservation of margay (Leopardus wiedii) spermatozoa: Effects of different extenders and frozen protocols

Sperm cryopreservation offers many benefits to wild felids conservation programs. However, the implementation of these programs is limited by the different responses of each species to the cryopreservation protocols and extenders used, requiring the formulation of species-specific protocols. For this purpose, semen samples from 6 margays (Leopardus wiedii) were submitted to 2 cryopreservation protocols: 1) manual freezing (cooling rate of - 0.33 °C/min at 5 °C/180 min and freezing rate with two steps - 9 °C/min for 2 min and -19.1 °C/min for 2 min) and 2) automatic freezing machine (cooling rate of - 0.25 °C/min at 5 °C/120 min and freezing rate with one step -20 °C/min for 8.3 min) using 2 commercial extenders, an egg yolk-based (Test Yolk Buffer; TYB) and an egg yolk-free extender (AndroMed; MED). Post-thawed sperm quality was assessed at 3 time points (immediately after thawing and 1 and 2 h post-thawed) by sperm motility index (SMI), plasma membrane and acrosomal integrity, and mitochondrial membrane potential (MMP). Regarding SMI, TYB yielded superior results (29.4 ± 3.5%) compared to MED (11.2 ± 2.8%; p < 0.002) immediately after thawing until 2 h after thawing (TYB 3.9 ± 1.7% and MED 0.0 ± 0.0%; p < 0.05). Furthermore, the automated freezing method provided higher motility compared to the manual freezing procedure immediately post-thaw (25.08 ± 3.66% and 15.78 ± 3.29%, respectively) and 1 h post-thaw (13.71 ± 2.56% and 6.03 ± 1.97%, respectively; p < 0.05). The percentage of intact acrosomes and plasma membranes and the percentage of sperm with high MMP were superior for TYB when compared to MED regardless of cryopreservation protocol (p < 0.05). Conversely, the interaction between cryopreservation protocols and extenders was observed for MMP where TYB exhibits better results compared to MED (p < 0.05) in both procedures, but it was higher in automated procedures. For MED, no changes were found in MMP between procedures. Considering only TYB, samples showed higher MMP when submitted to an automated procedure (p < 0.05). In conclusion, the slow cooling rates with shorter time of exposure to glycerol contributed to minimize cryodamage in the Margays' sperm. Moreover, results indicated that association between TYB and automatic freezing machine ensured the minimal quality of spermatozoa after thawing required for further use in in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI).

Practical application of laparoscopic oviductal artificial insemination for the propagation of domestic cats and wild felids

AI was first reported in cats almost 50 years ago but, unlike AI in other domesticated animals (e.g. dogs, cattle, horses), has not been widely used for routine propagation by veterinarians or breeders. Anatomical and physiological challenges with cats have hindered the efficiency of AI using standardised transcervical approaches applied to other species. Development of laparoscopic oviductal AI (LO-AI) has helped overcome some of these barriers and, during the past 7 years, produced high pregnancy percentages (>70%) in domestic cats using both fresh collected and frozen-thawed semen and resulted in the birth of full-term offspring in three cat hereditary disease models and six wild cat species (ocelot, Pallas's cat, fishing cat, sand cat, tiger, clouded leopard). The standard approach involves exogenous gonadotrophin treatment (typically equine chorionic gonadotrophin followed by porcine LH) to induce ovarian follicular growth and ovulation, with laparoscopic visualisation of the oviductal ostium for direct intraluminal insemination with low numbers of spermatozoa. Similar ovarian synchronisation and insemination approaches have been used with wild felids, but frequently must be refined on a species-by-species basis. From a practical perspective, LO-AI in domestic cats now has adequate efficiency for applied use as a reproductive service in veterinary practices that possess basic laparoscopy expertise.

Biobanking efforts and new advances in male fertility preservation for rare and endangered species

Understanding and sustaining biodiversity is a multi-disciplinary science that benefits highly from the creation of organized and accessible collections of biomaterials (Genome Resource Banks). Large cryo-collections are invaluable tools for understanding, cataloging, and protecting the genetic diversity of the world's unique animals and plants. Specifically, the systematic collection and preservation of semen from rare species has been developed significantly in recent decades with some biobanks now being actively used for endangered species management and propagation (including the introduction of species such as the black-footed ferret and the giant panda). Innovations emerging from the growing field of male fertility preservation for humans, livestock species, and laboratory animals are also becoming relevant to the protection and the propagation of valuable domestic and wild species. These new approaches extend beyond the “classical” methods associated with sperm freezing to include testicular tissue preservation combined with xenografting or in vitro culture, all of which have potential for rescuing vast amounts of unused germplasm. There also are other options under development that are predicted to have a high impact within the next decade (stem cell technologies, bio-stabilization of sperm cells at ambient temperatures, and the use of genomics tools). However, biobanking efforts and new fertility preservation strategies have to expand the way beyond mammalian species, which will offer knowledge and tools to better manage species that serve as valuable biomedical models or require assistance to reverse endangerment.

The effects of permeating cryoprotectants on intracellular free-calcium concentrations and developmental potential of in vitro-matured feline oocytes

Embryos produced from vitrified feline oocytes have resulted in pregnancies, but the efficiency of oocyte vitrification in cats is still low. Our objectives were to evaluate the effects of exposing feline oocytes to ethylene glycol (EG), propanediol (PrOH) and dimethyl sulfoxide (DMSO) on changes in intracellular free-calcium concentrations ([Ca2+]i), the time needed for enzymatic digestion of the zona pellucida (ZP), the incidence of parthenogenetic activation and degeneration and embryonic development following in vitro fertilisation (IVF). All of the chemicals tested altered [Ca2+]i, but changes in [Ca2+]i, resistance of the ZP to enzymatic digestion and the incidence of parthenogenetic activation (<5% for all treatments) were not affected (P > 0.05) by extracellular Ca2+. Exposure to EG (>44.1%) and DMSO (19.7%) increased (P < 0.05) oocyte degeneration compared with control oocytes and oocytes exposed to PrOH (≤2.5%). Following exposure to a combination of PrOH and DMSO (10% v/v each), blastocyst development (per cleaved embryo; 52.1%) was similar (P > 0.05) to control oocytes (64.4%). When oocytes were vitrified with PrOH and DMSO, 28.3% of surviving (intact plasma membrane) oocytes cleaved following IVF, but no blastocyst developed. When a non-permeating cryoprotectant (galactose, 0.25 M) was added to the vitrification medium, 47.7% of surviving oocytes cleaved and 14.3% developed to the blastocyst stage.

Mammalian fertility preservation through cryobiology: value of classical comparative studies and the need for new preservation options

Human-related fertility preservation strategies have enormous potential for helping sustain and protect other species, especially to assist managing or 'rescuing' the genomes of genetically valuable individuals, including endangered species. However, wider-scale applications are limited by significant physiological variations among species, as well as a lack of fundamental knowledge of basic reproductive traits and cryosensitivity. Systematic and comparative cryopreservation studies (e.g. on membrane biophysical properties and resilience to freezing temperatures) are required to successfully recover gametes and gonadal tissues after thawing and eventually produce healthy offspring. Such data are currently available for humans and a few laboratory and livestock animals, with virtually all other species, including wildlife, having gone unstudied. Interestingly, there also are commonalities among taxa that allow a protocol developed for one species to provide useful information or guidance for another. However, when a rare animal unexpectedly dies there is no time for a prospective understanding of that species' biophysical traits. Because the odds of success will be much lower in such instances, it is essential that more fundamental studies be directed at more species. But also worthwhile is thinking beyond these systematic characterisations to consider the potential of a 'universal preservation protocol' for animal biomaterials.

Recent advances and prospects in germplasm preservation of rare and endangered species

Fertility preservation strategies using cryopreservation have enormous potential for helping sustain and protect rare and endangered species, especially to assist managing or 'rescuing' the genomes of genetically valuable individuals. However, wide-scale applications are still limited by significant physiological variations among species and a sheer lack of fundamental knowledge about basic reproductive traits as well as in germplasm cryobiology. Cryo-studies have been conducted in more species (mainly vertebrates) in the recent years but a vast majority still remains un-studied. Semen cryopreservation represents the most extensive effort with live births reported in more and more species after artificial insemination. Oocyte freezing remains challenging and unsuccessful in wild species and will require more research before becoming a standard procedure. As an alternative to fully grown gametes, gonadal tissue preservation has become a promising option in vertebrates. Yet, more fertility preservation options are necessary to save species so a change in strategy might be required. It is worthwhile thinking beyond systematic characterizations and considering the application of cutting edge approaches to universally preserve the fertility of a vast array of species.

Comparative cryobiological traits and requirements for gametes and gonadal tissues collected from wildlife species

A major challenge to retaining viability of frozen gametes and reproductive tissues is to understand and overcome species-specificities, especially because there is substantial diversity in cryobiological properties and requirements among cell types and tissues. Systematic studies can lead to successful post-thaw recovery, especially after determining: 1) membrane permeability to water and cryoprotectant, 2) cryoprotectant toxicity, 3) tolerance to osmotic changes, and 4) resistance to cooling and freezing temperatures. Although species-dependency ultimately dictates the ability of specific cells and tissues to survive freeze-thawing, there are commonalities between taxa that allow a protocol developed for one species to be useful information for another. This is the reason for performing comparative cryopreservation studies among diverse species. Our laboratory has compared cellular cryotolerance, especially in spermatozoa, in a diverse group of animals-from corals to elephants-for more than 30 yrs. Characterizing the biophysical traits of gametes and tissues is the most efficient way to develop successful storage and recovery protocols, but, such data are only available for a few laboratory, livestock, and fish species, with virtually all others (wild mammals, birds, reptiles, and amphibians) having gone unstudied. Nonetheless, when a rare animal unexpectedly dies, there is no time to understand the fundamentals of biophysics. In these emergencies, it is necessary to rely on experience and the best data from taxonomically-related species. Fortunately, there are some general similarities among most species, which, for example, allow adequate post-thaw viability. Regardless, there is a priority for more information on biophysical traits and freezing tolerance of distinctive biomaterials, especially for oocytes and gonadal tissues, and even for common, domesticated animals. Our colleague, Dr John Critser was a pioneer in cryobiology, earning that moniker because of his advocacy and devotion to understanding the differences (and similarities) among species to better store living genetic material.

Fecal endocrine profiles and ejaculate traits in black-footed cats (Felis nigripes) and sand cats (Felis margarita)

Information regarding the reproductive biology of black-footed cats (BFC) and sand cats (SC) is extremely limited. Our objectives were to: (1) validate fecal hormone analysis (estrogens, E; progestagens, P; androgens, T) for noninvasive monitoring of gonadal activity; (2) characterize estrous cyclicity, ovulatory mechanisms, gestation, and seasonality; and (3) evaluate male reproductive activity via fecal androgen metabolites and ejaculate traits. In both species, the estrous cycle averaged 11-12 days. In BFC (n=8), estrus lasted 2.2+/-0.2 days with peak concentrations of E (2962.8+/-166.3 ng/g feces) increasing 2.7-fold above basal concentrations. In SC (n=6), peak concentrations of E (1669.9+/-83.5 ng/g feces) during estrus (2.9+/-0.2 days) were 4.0-fold higher than basal concentrations. Nonpregnant luteal phases occurred in 26.5% (26 of 98) of BFC estrous cycles, but were not observed in SC (0 of 109 cycles). In both species, P concentrations during pregnancy were elevated (32.3+/-3.0 microg/g feces BFC; 8.5+/-0.7 microg/g feces SC) approximately 10-fold above basal concentrations. Fecal T concentrations in males averaged 3.1+/-0.1 microg/g feces in BFC and 2.3+/-0.0 microg/g feces in SC. Following electroejaculation, 200 to 250 microl of semen was collected containing 29.9 (BFC) to 36.5 (SC)x10(6) spermatozoa with 40.4 (SC) to 46.8 (BFC)% normal morphology. All females exhibited estrous cycles during the study and spermatozoa were recovered from all males on every collection attempt, suggesting poor reproductive success in these species may not be due to physiological infertility.

Reproductive traits in captive and free-ranging males of the critically endangered Iberian lynx (Lynx pardinus)

The Iberian lynx (Lynx pardinus) is the most endangered felid in the world. Adequate genetic management of in situ and ex situ populations, and linkage between both, require knowledge on male reproductive biology and factors influencing it. We examined the influence of age, free-ranging versus captive conditions and seasonality on phenotypic, endocrine and semen traits, and links between reproductive traits and male fertility. Males had relatively small testes, produced low sperm numbers, a low proportion of normal sperm, and a high proportion of motile sperm. Young (2-year-old) males had lower testosterone levels, fewer sperm, and a lower proportion of motile and normal sperm than ≥4-year-old males. No major differences were found in semen traits before and after the mating season or between free-ranging and captive males, although the latter had better sperm motility. Males with larger relative testes weight and more sperm copulated more frequently, whereas males that produced more sperm with higher motility produced more cubs per female. In conclusion, small relative testes size and low sperm quality could indicate either low levels of sperm competition or high levels of inbreeding. Young males are probably subfertile; there is a slight trend for males in the captive breeding programme to have better semen quality than wild males, and males with higher sperm production are sexually more active and more fertile. These findings have major implications for decisions regarding which males should breed, provide samples for the genetic resource bank, or participate in programmes involving the use of assisted reproductive techniques.

Assessment of semen quality, sperm cryopreservation and heterologous IVF in the critically endangered Iberian lynx (Lynx pardinus)

Semen traits and factors affecting sperm cryopreservation were assessed in the Iberian lynx (Lynx pardinus), a species regarded as the most endangered felid in the world. For cryopreservation, semen was washed, resuspended in a Tes–Tris-based diluent (TEST) or a Tris-based diluent (Biladyl), both with 20% egg yolk and 4% glycerol, loaded into straws, cooled to 5°C using an automated programmable system and frozen on nitrogen vapour. Heterologous IVF of in vitro-matured domestic cat oocytes was used to test the fertilising ability of cryopreserved spermatozoa. Electroejaculates from five males were obtained. Characterisation of the electroejaculates revealed mean (± s.e.m.) values of 3.3 ± 0.6 × 106 total spermatozoa, 73.6 ± 4.6% motile spermatozoa, 23.7 ± 4.0% morphologically normal spermatozoa and 40.7 ± 2.3% spermatozoa with intact acrosomes. After thawing a higher percentage of motile spermatozoa was seen in TEST than in Biladyl (34.0 ± 6.2% v. 7.5 ± 4.8%, respectively; P < 0.05); however, there were no differences in the percentage of intact acrosomes between the two diluents. Iberian lynx spermatozoa fertilised domestic cat oocytes in vitro, with higher fertilisation rates observed for spermatozoa cryopreserved in TEST than in Biladyl, although the difference did not reach statistical significance (20.5 ± 4.5% v. 11.5 ± 6.8%, respectively). There were positive significant relations between the fertilisation rates and both the percentage of normal spermatozoa and the percentage of spermatozoa with an intact acrosome before cryopreservation (P = 0.04). This first report of the collection and cryopreservation of Iberian lynx semen and analysis of fertilising ability is an important step in the development of assisted reproductive techniques for this critically endangered felid species.