Infertility in purebred cats - A review of the potential causes

Insights into alternative cryoprotectants to freeze sperm of domestic cats

Globalization and habitat destruction pose a significant threat to wildlife felids. Even though conservation banks for genetic materials have been created, the sperm cryopreservation with minimal cell damage is still a great challenge. Thus, this study aimed to compare the effects of two commercial extenders with different concentrations of alternative cryoprotectants on thawed sperm quality of domestic cats. Five adult cats were anaesthetized (using a combination of 40 μg/kg medetomidine associated to 5 mg/kg ketamine), and the semen was collected by electroejaculation (electrical stimulation of 2-3 V). Semen samples were evaluated for sperm characteristics (kinetics, morphology, membrane integrity and morphometry). Subsequently, they were sorted into two aliquots and centrifuged. The aliquots were added to a commercial extender containing 3% glycerol and 2% methylformamide (extender I) or 2% glycerol and 3% methylformamide (extender II), frozen, thawed (37°C/30 s) and reevaluated. Comparatively, the sperm kinetics and membrane integrity of fresh semen were higher (p < .002) than frozen samples in extender I and II. Total and progressive motility were lowest in the thawed samples. However, the subjective analysis indicated high sperm motility, since the kinetics evaluation was impaired by the low cell number in the thawed samples. There were no differences in sperm morphology between the groups. In the sperm morphometric analysis, a significant difference (p = .04) was identified in the length of the intermediate piece in extender II samples compared with fresh and extender I. Thus, it can be concluded that although the concentrations tested did not maintain the kinetic parameters and membrane integrity of spermatozoa after thawing, the extender with a lower concentration of glycerol was less toxic for maintaining the midpiece length.

Observations about declining fertility in a feline breeding colony

Feline breeding colonies are important to the feline industry by preserving traits desirable for a particular breed or in research settings by maintaining medically valuable genetic traits. As breeding females age, their reproductive efficiency declines. The objective of this study was to determine the most common causes of infertility in breeding females that were producing fewer kittens. Knowing the cause and average age of infertility would allow management decisions to be made for the betterment of the colony. The medical records of 70 queens retired from breeding from a single research colony were examined for litter size and number, fertility over their lifespan, and age and reason for removal from breeding stock. Sections of uterus and ovaries were evaluated using gross and histopathological examination for a subset of these queens (46). The data suggests that mature, continuously breeding female cats may show signs of reduced fertility (infertile matings or reduced litter size) as early as 3 years of age and may be a result of undiagnosed Cystic Endometrial Hyperplasia (CEH), endometritis, pyometra and/or ovarian cysts. Evaluation of breeding queens should include periodic ultrasounds to monitor for ovarian cysts and evidence of CEH. Retiring animals from breeding once signs of infertility become apparent is recommended.

Reproduction of Domestic Cats in Laboratories, Catteries, and Feral Colonies: A Review

Cat reproduction is important for research and commercial cat breeding operations, as well as the control of feral cat populations. This review describes studies examining reproductive performance in laboratory cats, privately-owned breeding cats, and feral cats, including sexual maturity, the estrous cycle (timing, behavior, and hormonal changes), seasonal effects, gestation length, parturition (litter size, litter weight, and parity effects), mortality, and stillbirth. Because the studies highlighted in this review vary in the location where they were conducted and the region's management practices, these factors should be considered depending on the goal of the reader when interpreting these data. Furthermore, standard practices were lacking in some earlier studies of cat reproduction, so they should be considered for historical context only and may not reflect the actual reproductive potential of cats as described in the new studies due to advancements in husbandry practices and nutrition. The objective of this manuscript is to review scientific studies examining reproductive performance in laboratory cats, privately-owned breeding cats, and feral cats. The data sources for this manuscript included original research publications and scientific reviews from the veterinary literature. All reviews or studies that augmented the knowledge of the reproduction of domestic cats in laboratories, catteries, and feral colonies were included. Most studies on laboratory cats have been conducted under the conditions of controlled light cycles, temperature, and diet. The environmental effects on reproductive behavior are subtler than those in feral cat studies, but the effects are still distinguishable. Cat breeding studies focus on genetic effects and rely heavily on surveys or questionnaires from cat breeders. However, the reliability of these data can be variable, in part because the methodology of record-keeping and other protocols are generally not reported. In addition, laboratory animal management standards, specific pathogen-free cat colonies, and nutritional requirements for cats were not fully established until the 1970s. Reproductive outcomes of earlier studies may not be a true representation of the modern cat due to more advanced, regulated husbandry practices, including improvements in nutrition, resulting in diets formulated to meet feline requirements for every life stage.

ARRDC5 expression is conserved in mammalian testes and required for normal sperm morphogenesis

In sexual reproduction, sperm contribute half the genomic material required for creation of offspring yet core molecular mechanisms essential for their formation are undefined. Here, the α-arrestin molecule arrestin-domain containing 5 (ARRDC5) is identified as an essential regulator of mammalian spermatogenesis. Multispecies testicular tissue transcriptome profiling indicates that expression of Arrdc5 is testis enriched, if not specific, in mice, pigs, cattle, and humans. Knockout of Arrdc5 in mice leads to male specific sterility due to production of low numbers of sperm that are immotile and malformed. Spermiogenesis, the final phase of spermatogenesis when round spermatids transform to spermatozoa, is defective in testes of Arrdc5 deficient mice. Also, epididymal sperm in Arrdc5 knockouts are unable to capacitate and fertilize oocytes. These findings establish ARRDC5 as an essential regulator of mammalian spermatogenesis. Considering the role of arrestin molecules as modulators of cellular signaling and ubiquitination, ARRDC5 is a potential male contraceptive target.

Disease threats to tigers and their prey

The contraction of the global tiger population over the last 100 years into small, often isolated subpopulations has made them increasingly vulnerable to the impact of disease. Despite this, the health of wild tigers continues to be insufficiently funded and explored. For example, canine distemper virus (CDV), has been associated with localized declines and increased risk of extinction, and yet has received little research attention in most tiger range countries. The emergence of new pathogenic threats has posed fresh challenges, including African swine fever virus (ASFV), which has the potential to devastate wild boar populations, and severe acute respiratory syndrome coronavirus (SARS-CoV2) with implications for tiger conservation that remain unknown. The objective of this review is to synthesize current research on the health of tigers and their prey that impacts the conservation of tigers in the wild. Published sources are interpreted based on three mechanisms through which disease can affect the viability of tiger populations: (1) by reducing the survival of adult tigers, (2) by reducing breeding productivity, and (3) by reducing the carrying capacity of tiger habitat through decreased prey abundance. Examples of CDV, SARS-CoV2, carnivore protoparvovirus 1 and ASFV are used to illustrate these processes and inform discussion of research and mitigation priorities.

Serum antimüllerian hormone concentrations in female cats. Relation with ovarian remnant syndrome, ovarian cysts and gonadectomy status

The aim of this study was to reveal (1) the determination of the serum antimüllerian hormone concentrations in cats with ovarian remnant syndrome and ovarian cyst, (2) the effectiveness of the serum antimüllerian hormone concentrations in detecting gonadectomy status, and (3) ovarian expression of the antimüllerian hormone in the ovarian cysts and ovarian remnant tissue. For this purpose, a total of 31 domestic cats older than 1 year, including ORS (n = 9), OC (n = 3), spayed (n = 8), and intact (n = 11), were used in the study. Serum and intrafollicular AMH concentrations were determined by the electrochemiluminescence immunoassay, and expression of the AMH was determined by the immunohistochemical method. The serum AMH concentration in the ORS group was 1.49 ± 1.24 ng/ml (0.10-3.63 ng/ml) whereas it was 1.78 ± 0.92 ng/ml (0.8-2.63 ng/ml) in the OC group. AMH concentration in the intrafollicular fluid was determined as 0.023 ng/ml in a cat with an ovarian cyst. While the serum AMH concentration was below 0.01 ng/ml in spayed cats, it was 5.80 ± 3.30 ng/ml (1.88-11.86 ng/ml) in the intact cats. There was a significant difference between the spayed and intact groups in terms of serum AMH concentration (p < 0.05). Moreover, in cats with ovarian cyst and ovarian remnant syndrome, no difference was found between the groups in terms of serum AMH concentration (p > 0.05). No difference was found between the ovarian remnant syndrome and intact cats in terms of serum AMH concentration (p > 0.05). In immunohistochemical staining, ovarian cysts were found to be negative for AMH while a moderate (+2) AMH positivity was observed in other follicles. Furthermore, in cats with ovarian remnant syndrome, severe (+3) AMH positivity was observed. As a result, it was determined that gonadectomy status can be accurately diagnosed by the AMH measurement. Ovarian remnant syndrome cannot be diagnosed accurately by AMH measurement. In addition, it was found that AMH did not seem to play a role in the pathogenesis of ovarian cysts in cats.

Estrogen and progesterone receptors and antioxidant enzymes are expressed differently in the uterus of domestic cats during the estrous cycle

Sex steroids and antioxidant enzymes are important in female sexual development and adequate modulation of the estrous cycle, pregnancy, and fetal development. Therefore, modifications in its signaling or expression in the genital system are associated with reproductive dysfunctions. However, the spatial-temporal expression profile of receptors for sex steroids and antioxidant enzymes in the uterus of domestic cats throughout the estrous cycle needs to be studied. Cats in proestrus/estrus (N = 6), diestrus, (N = 7), and anestrus (N = 6) were used to evaluate the uterine expression of estrogen alpha (ERα), progesterone (PR), and androgen (AR) receptors and of the antioxidant enzymes superoxide dismutase 1 (SOD1), catalase and glutathione peroxidase 1 (GPX1) by immunohistochemistry and qPCR. The uterus of cats in diestrus showed lower protein and mRNA expression of ERα and PR compared to proestrus/estrus and anestrus, mainly in the luminal and glandular epithelium and myometrium, different from catalase and SOD1, which showed higher expression in diestrus in relation to other phases of the cycle. GPX1, on the other hand, showed lower uterine gene expression in diestrus compared to proestrus/estrus and anestrus. No significant differences in AR expression were observed. In conclusion, ERα and PR sex steroid receptors and antioxidant enzymes are expressed differently in the uterus of domestic cats during the estrous cycle.

Uterine issues in infertile queens: nine cases

This prospective case series investigated potential uterine causes of infertility in queens. Purebred queens with infertility (failure to conceive, embryonic death, or failure to maintain pregnancy and produce viable kittens), but no other reproductive disorders were examined approximately 1-8 weeks before mating (Visit 1), 21 days after mating (Visit 2), and 45 days after mating (Visit 3) if pregnant at Visit 2. Investigations included vaginal cytology and bacteriology, urine bacteriology, and ultrasonography. At Visit 2 or 3, uterine biopsy or ovariohysterectomy was performed for histology. Of nine eligible queens, seven were non-pregnant by ultrasound at Visit 2 and two had lost pregnancies by Visit 3. Ovulation was confirmed by serum progesterone concentration in all queens. Ultrasonic appearance of the ovaries and uterus was compatible with a healthy status except for one queen with signs of cystic endometrial hyperplasia (CEH) and pyometra, a follicular cyst in another, and fetal resorptions in two queens. Six cats had histologic lesions of endometrial hyperplasia, including CEH (n=1). Only one cat had no histologic uterine lesions. Bacteria were cultured from vaginal samples in seven queens at Visit 1, (two were non-evaluable), and in five of seven queens sampled at Visit 2. Uterine cultures were negative except for the cat with pyometra. All urine cultures were negative. In summary, the most frequent pathology observed in these infertile queens was histologic endometrial hyperplasia, which can potentially inhibit embryo implantation and healthy placental development. This suggests that uterine disease might contribute substantially to infertility in purebred queens.

Generation and cryopreservation of feline oviductal organoids

Next-generation in vitro culture model systems are needed to study the reproductive pathologies that affect domestic animals. These 3D culture models more closely mimic normal physiological function to allow a greater understanding of reproductive pathology and to trial therapeutics without the welfare concerns and the increased time and cost associated with live animal research. Recent advances with in vitro cell culture systems utilizing human and laboratory animal tissues have been reported, but implementation of these technologies in veterinary species has been slower. Organoids are a physiologically representative 3D cell culture system that can be maintained long-term. By combining organoid culture with cryopreservation, a long-term, experimental model can be available for year-round application, thus bypassing seasonality and reproductive tract availability restrictions. Here we report the generation and cryopreservation of feline oviductal organoids for the first time. Optimal culture medium for the generation of feline oviductal organoids was established, and organoids were successfully cryopreserved using three different freezing media with organoids from each treatment demonstrating comparable viability, growth rate, and protein expression after thawing and culture. Feline oviductal organoids may facilitate an in vivo-like environment that, in conjunction with co-culture for in vitro maturation and in vitro fertilization, may positively influence in vitro gamete and embryo development, embryo quality, and pregnancy rates after embryo transfer in domestic and nondomestic felids. Furthermore, readily available cryopreserved feline oviductal organoids will facilitate this co-culture, which is of particular importance to endangered felid breeding programs where tissue and gamete samples are often opportunistically obtained with little or no notice.

Reproductive Management in Catteries: Optimising health and wellbeing through veterinarian-breeder collaboration

PRACTICAL RELEVANCE

Many veterinarians - even those engaged in small animal reproduction - are uncomfortable with taking care of cat breeders or being in charge of catteries. Likely reasons for this are that feline reproduction is largely under-represented in undergraduate and graduate reproduction teaching, as well as in postgraduate education and science, whereas cat breeders themselves are often well informed and actively share knowledge with other cat breeders via the internet and social media.

CLINICAL CHALLENGES

A variety of problems can exist within a cattery, and collaboration between veterinarian and breeder to solve these is ultimately beneficial for the breeder, for the veterinarian, and for the health and wellbeing of the individual cats and of the cattery as a whole.

AIM

This review presents a comprehensive overview of aspects of cattery management that might negatively impact reproduction, including sanitation, hygiene and infectious disease control. It also discusses monitoring of reproductive performance, breeding recommendations, and the diagnostic and therapeutic approach to some common and specific problems.

EQUIPMENT AND TECHNICAL SKILLS

Reproductive management in the cattery requires no specialised equipment, as such. What it does need is an open mind, in terms of seeing how things are done, an open ear, for listening to the breeder, and the veterinarian's clinical skills in palpation, auscultation and, where required, further examination of the animals. Keeping abreast of the latest information on infectious diseases, disinfection and genetics ensures proper advice is provided.

EVIDENCE BASE

Current knowledge of reproductive management in catteries is summarised in order to apply an evidence-based approach, whenever possible. Notwithstanding, much of the information remains empirical.

Infertility In Toms: Clinical approach, experiences and challenges

PRACTICAL RELEVANCE

An infertile tom used to be a relatively rare presentation in feline practice. However, as a result of breeding strategies targeting specific morphological/behavioural traits, and the influence of inbreeding (especially practised in rare breeds), among other factors, feline infertility has become a genuine clinical problem. Furthermore, increased interest among cat breeders and pet owners in diagnosing and treating an 'unsuccessful' tom (including using assisted reproductive techniques [ARTs]), has made such patients more commonplace in veterinary practice.

CLINICAL CHALLENGES

A definitive cause for male infertility is often difficult to identify. One of the biggest challenges is the lack of fertility-based reference values for semen quality and hormone levels. Moreover, the literature in this field is scant and many reproductive tract conditions described in other species have not been reported in cats. The establishment of diagnostic tools and algorithms is essential to facilitate a reliable assessment of fertility potential.

GLOBAL IMPORTANCE

There is a growing demand for appropriate veterinary care relating to feline reproduction. There is an expectation among breeders, particularly of pedigree cats of high breeding value, that the same options widely used for dogs (including ARTs) should also be available for cats.

EQUIPMENT AND TECHNICAL SKILLS

Equipment required for investigating male infertility includes a microscope and ultrasound machine; a blood analyser may also be useful, but samples can instead be sent to a laboratory. The skills required are often already performed by veterinarians; for example, catheterising the urethra, performing ultrasonography and blood sampling.

EVIDENCE BASE

There are some reports of fertility problems in male cats in the literature, but this area of feline reproduction is still relatively undeveloped. This review draws on the comprehensive knowledge developed and shared by specialists in this field, and is supported by the authors' own clinical experience.

Prevalence of Vector-Borne Pathogens in Reproductive and Non-Reproductive Tissue Samples from Free-Roaming Domestic Cats in the South Atlantic USA

Reservoir to multiple species of zoonotic pathogens, free-roaming cats (FRCs) interact with domestic and wild animals, vectors, and humans. To assess the potential for feline vector-borne pathogens to be vertically transmitted, this study surveyed ear tip and reproductive tissues of FRCs from two locations in the South Atlantic United States for Anaplasma, Bartonella, Ehrlichia, hemotropic Mycoplasma, and Rickettsia species. We collected ovary (n = 72), uterus (n = 54), testicle (n = 74), and ear tip (n = 73) tissue from 73 cats, and fetal (n = 20) and placental (n = 19) tissue from 11 queens. Pathogen DNA was amplified utilizing qPCR, confirmed by sequencing. Cats were more frequently Bartonella henselae positive on reproductive tissues (19%, 14/73) than ear tip (5%, 4/73; p = 0.02). B. henselae was amplified from fetus (20%, 4/20) and placenta samples (11%, 2/19). Bartonella spp. infection was more common in cats from North Carolina (76%, 26/34) than Virginia (13%, 5/39; p < 0.0001). Fourteen percent (10/73) of both ear tip and reproductive tissues were positive for hemotropic Mycoplasma spp. Anaplasma, Ehrlichia, and Rickettsia spp. DNA was not amplified from any cat/tissue. These findings suggest that B. henselae preferentially infected cats' reproductive tissue and reinforces the importance of investigating the potential for B. henselae vertical transmission or induction of reproductive failure.

Endometrial Status in Queens Evaluated by Histopathology Findings and Two Cytological Techniques: Low-Volume Uterine Lavage and Uterine Swabbing

Simple Summary

The endometrium health of feline queens can be difficult to assess due to the reduced size of the uterus, which hinders representative biopsy sampling. This may result in limitations in diagnosing endometritis, and consequently in detecting infertility problems. Although histology is considered the most reliable technique for diagnosing endometritis in many species, cytology is also gaining importance and may be an alternative tool for evaluating the endometrium in small species. Two different common cytological techniques (uterine lavage and uterine swabbing) were compared to determine the reliability of cytology for evaluating the endometrium status in queens. Histopathological and bacteriological information was used for the control methods. Our results demonstrated that cytology may be a useful diagnostic tool for assessing the endometrial status. In addition, when comparing cytological techniques, the uterine lavage method was more representative than uterine swabbing.

Abstract

Endometritis is associated with fertility problems in many species, with endometrial biopsy being the main diagnostic tool. In feline queens, the reduced size of the uterus may make it difficult to obtain representative diagnostic samples. Endometrial cytology may represent a valuable diagnostic tool for evaluating the health status of the endometrium in queens. Fifty domestic shorthair queens were included and divided into two cytological diagnostic technique groups, the uterine lavage (UL; n = 28) and uterine swabbing (US; n = 22) groups. Cytological results were compared with histopathological and bacteriological information. Changes in the histopathological patterns were also evaluated and compared with progesterone levels to confirm previous published data. Furthermore, the results from both cytological sampling methods were compared to evaluate the utility of each method. Endometritis was ruled out in all queens by means of histology and microbiology. Leukocyte counts and red blood cell/endometrial cell ratios were significantly higher in US than UL samples. Additionally, UL sampling is less affected by blood contamination and cells are better preserved. The combination of endometrial cytology and uterine culture might be useful for evaluating the endometrial characteristics in queens. The UL evaluation method is more representative of the actual endometrial status than the US technique.