Monitoring ovarian function and detecting pregnancy in felids: A review

Serum anti-Müllerian hormone around the time of ovulation simulated by exogenous hormones in clouded leopards (Neofelis nebulosa)

Anti-Müllerian hormone (AMH) is produced by granulosa cells of the antral follicles. It serves as a promising biomarker for ovarian reserve and responsiveness to ovarian stimulation in humans and domestic animals. This study aimed to validate the AMH Gen II enzyme-linked immunosorbent assay (ELISA) and correlate ovarian structures with serum AMH concentrations after stimulation treatment in clouded leopards (Neofelis nebulosa). Serum samples were collected from 12 women (age 6.21 ± 3.56 years), and serum AMH concentrations were analysed using AMH Gen II ELISA. The animals were divided into two groups based on ovarian structures [preovulatory follicles (>2 mm) and/or corpora hemorrhagica] along with the presence of uterine tonicity visualized laparoscopically around the time of ovulation. Animals that exhibited these reproductive features were identified as the responder group (n = 9, aged 7.59 ± 2.96 years), whereas those lacking the corresponding features were assigned to the nonresponder group (n = 3, aged 2.06 ± 0.53 years). The intra-assay coefficient of variation (CV) and interassay CV was 3.56% and 7.75%, respectively. The linearity of AMH dilution was confirmed (r2  = .998), and the percentage of recovery ranged from 93% to 115%. The results demonstrated that overall serum AMH concentrations around the time of ovulation were negatively correlated with age (rs  = -.692, p = .013). However, serum AMH concentrations were not correlated with the average number of ovarian structures (rs  = -.535, p = .074). Thus, AMH Gen II ELISA was validated in clouded leopards. Around the time of ovulation, serum AMH decreased with advancing age and ovarian responsiveness cannot be evaluated using serum AMH.

Scent detection dogs as a novel method for oestrus detection in an endangered species, the Tasmanian devil (Sarcophilus harrisii)

Captive breeding is a critical tool for conservation of endangered species. Identifying the correct time to pair males and females can be a major challenge for captive breeding programmes, with current methods often being invasive or slow. Detection dogs may provide a non-invasive way to determine female receptivity, but this has not been explored in captive wildlife. This exploratory study investigated the use of detection dogs as a novel method of oestrus detection in the endangered Tasmanian devil (Sarcophilus harrisii). Faecal samples were collected from 11 captive female devils during the breeding seasons of 2020 and 2021. Three dogs with prior detection experience were trained and subsequently assessed (n = 188 searches per dog), on their ability to discriminate between oestrus and non-oestrus devil faecal samples, in a one sample set-up. When assessed on training samples, dogs were able to correctly discriminate oestrus from non-oestrus with a mean sensitivity of 69.1% and mean specificity of 65.7%. When assessed on novel samples, their sensitivity to oestrus dropped (mean sensitivity of 48.6%). However, they were still able to correctly identify non-oestrus samples (mean specificity of 68.1%). This study is the first to explore detection dogs' ability to identify oestrus in a captive breeding programme for endangered wildlife, providing a promising tool for non-invasive monitoring of reproductive status in wildlife.

Molecular Factors Involved in the Reproductive Morphophysiology of Female Domestic Cat (Felis catus)

The domestic cat (Felis catus) is considered an important model for the study of feline reproductive morphophysiology. However, although the morphological changes and clinical signs that occur during the estrous cycle and pregnancy are well known, little is known about the molecular mechanisms involved in the reproductive physiology of this animal species. Thus, this paper reviews the current knowledge about the modulation and expression profile of hormonal, immunological, redox, and growth mediators involved in the uterine, ovarian, and placental morphophysiology of domestic cats.

Prolonged glucocorticoid administration affects oocyte morphology in cats (Felis catus) undergoing an ovarian stimulation protocol

While captivity-related stress and the associated rise in baseline glucocorticoid (GC) concentrations have been linked to ovarian quiescence in some felid species, no study has examined the effects of elevated GC on oocyte quality. This study examined the effects of exogenous GC administration on the ovarian response and oocyte quality of domestic cats after an ovarian stimulation protocol. Entire mature female cats were divided into treatment (n = 6) and control (n = 6) groups. Cats in the GC treatment (GCT) group were given 1 mg kg-1 oral prednisolone daily from Day 0-45. All cats (n = 12) were given 0.088 mg kg-1 day-1 progesterone orally from Day 0-37, before treatment with 75 IU eCG im to induce follicular growth on Day 40, followed by 50 IU hCG im 80 h later to induce ovulation. Cats were ovariohysterectomised 30 h after the hCG treatment. Blood samples were collected on Days 0, 10, 30 and 40 (prior to eCG treatment), 80 h after eCG treatment, and on Day 45 for cortisol, glucose, prednisolone, oestradiol, and progesterone analysis. Cortisol concentrations did not differ between treatment groups throughout the study. Mean glucose concentrations were higher in the GCT cats (P = 0.004). Prednisolone was undetectable in all samples. Oestradiol and progesterone concentrations confirmed that the eCG treatment stimulated follicular activity and ovulation in all cats. Following ovariohysterectomy, the ovarian responses were graded (1 = excellent, 4 = poor) and oocytes retrieved from the oviducts. Each oocyte was given a total oocyte score (TOS: using an 9-point scale, 8 = best) based on four parameters: oocyte morphology, size, ooplasm uniformity and granularity, and zona pellucida (ZP) thickness and variation. Ovulation was confirmed in all cats, with a mean of 10.5 ± 1.1 ovulations per cat. Ovarian mass, ovarian response, number of ovulations, and oocyte recovery did not differ between groups. Oocyte diameter did not differ between the groups, but the ZP was thinner in the GCT group (3.1 ± 0.3 μm vs. 4.1 ± 0.3 μm, P = 0.03). The TOS was similar between treatment and control cats, but the ooplasm grade was lower (1.5 ± 0.1 vs. 1.9 ± 0.1, P = 0.01) and there was a tendency for ZP grade to be poorer (0.8 ± 0.1 vs. 1.2 ± 0.2; P = 0.08) in the treatment group. In conclusion, the GC treatment resulted in morphological changes to oocytes collected following ovarian stimulation. Whether these changes would affect fertility warrants further investigation.

Provocative tests with Kisspeptin-10 and GnRH set the scene for determining social status and environmental impacts on reproductive capacity in male African lions (Panthera leo)

Understanding the hypothalamic factors regulating reproduction facilitates maximising the reproductive success of breeding programmes and in the management and conservation of threatened species, including African lions. To provide insight into the physiology and pathophysiology of the hypothalamic-pituitary-gonadal reproductive axis in lions, we studied the luteinising hormone (LH) and steroid hormone responses to gonadotropin-releasing hormone (GnRH) and its upstream regulator, kisspeptin. Six young (13.3 ± 1.7 months, 56.2 ± 4.3 kg) and four adult (40.2 ± 1.4 months, 174 ± 6 kg) male lions (Ukutula Conservation Centre, South Africa) were used in this study. Lions were immobilised with a combination of medetomidine and ketamine and an intravenous catheter was placed in a jugular, cephalic or medial saphenous vein for blood sampling at 10-min intervals for 220 min. The ten-amino acid kisspeptin which has full intrinsic activity (KP-10, 1 µg/kg) and GnRH (1 µg/kg) were administered intravenously to study their effects on LH and steroid hormone plasma concentrations, measured subsequently by ELISA and liquid chromatography tandem mass spectrometry (LC-MS/MS), respectively. Basal LH levels were similarly low between the age groups, but testosterone and its precursor levels were higher in the adult animals. Adult lions showed a significant LH response to KP-10 (10-fold) and GnRH (11-fold) administration (p < 0.05 and P < 0.001, respectively) whereas in young lions LH increased significantly only in response to GnRH. In adults alone, testosterone and its precursors steadily increased in response to KP-10, with no significant further increase in response to GnRH. Plasma levels of glucocorticoids in response to KP-10 remained unchanged. We suggest that provocative testing of LH and steroid stimulation with kisspeptin provides a new and sensitive tool for determining reproductive status and possibly an index of exposure to stress, environmental insults such as disease, endocrine disruptors and nutritional status. 272 words.

Label-Free Quantification (LFQ) of Fecal Proteins for Potential Pregnancy Detection in Polar Bears

Reliable pregnancy diagnostics would be beneficial for monitoring polar bear (Ursus maritimus) populations both in situ and ex situ, but currently there is no method of non-invasive pregnancy detection in this species. Recent reports in several carnivore species described the identification of fecal proteins that may serve as pregnancy biomarkers; however, repeatability has been limited. The objective of the current analysis was to utilize an unbiased, antibody-free, label-free method for the identification and quantification of fecal proteins to determine if differences associated with pregnancy are detectable in polar bears. Protein was extracted from fecal samples (n = 48) obtained from parturient (n = 6) and non-parturient (n = 6) profiles each at four timepoints: pre-breeding season, embryonic diapause, early placental pregnancy, and mid-placental pregnancy. Protein was prepared and analyzed on the Thermo Orbitrap Eclipse nanoLC-MS/MS system. A total of 312 proteins was identified and quantified; however, coefficients of variation (CV) were high for both abundance ratio variability (384.8 ± 61.0% SEM) and within group variability (86.8 ± 1.5%). Results of this study suggest that the inconsistencies in specific protein concentrations revealed previously by antibody-based assays may not be due to that methodology’s limitations, but rather, are reflective of true variation that exists among samples.

Trends in Small Animal Reproduction: A Bibliometric Analysis of the Literature

Simple Summary

Reproduction in small animals is an expanding research area, with focus on breeding improvement and clinical management of domestic carnivores. The aim of the present study was to conduct a bibliometric analysis of the literature of the last decade on small animal reproduction, to point out main sources, most prolific countries, and emerging and neglected topics. Results show that research in biotechnologies for assisted reproduction has a central and increasing role in this field. Diversity in author keywords was also pointed out and a consensus to better categorize research in this field is proposed to reduce this problem in the future.

Abstract

Small animal reproduction (SAR) is a main research field in veterinary medicine and bibliometric analyses are useful to investigate trends in specific research areas. The objective of the present study was to conduct a bibliometric analysis of the literature of the last decade on SAR. A search equation was created, and documents were retrieved from the Web of Science database. Documents were manually revised, categorized and R software version 4.1.2 with Bibliometrix R package version 3.1 and MS Excel were used to perform the analyses. The included documents (n = 1470) were mainly research articles (78%). The top countries for the number of documents and citations were Brazil, United States, Italy, Poland, and Korea. These also account for the most prolific authors and institutions. Analyses by author keywords, categories, and recent reviews of the literature suggest that research on the canine species is more abundant than research on the feline one and that reproductive biotechnologies are a main research focus. Some clinical topics are still considered niche or neglected themes (e.g., semen collection in tomcats, neonatology). However, heterogeneity and ambiguity in keywords and categories are undeniable. This study offers interesting insights, providing definitions for main keywords in the field of SAR.

Accelerometry and infrared thermography show potential for assessing ovarian activity in domestic cats (Felis catus)

Accurate and reliable monitoring of ovarian activity is challenging in many felids as current methods are either invasive or not amenable to real-time assessments. This 45-day study assessed whether accelerometry and infrared (IR) thermography can be used to address these limitations. Intact female domestic cats (n = 12) were given 0.088 mg kg^-1 day^-1 altrenogest (progestin) orally for 37 days to suppress follicular growth. On Day 40, cats were given 75 IU eCG im to induce follicular growth and 50 IU hCG im 80 h later to induce ovulation. Cats were ovariohysterectomised 30-31 h after the hCG treatment. Actical® accelerometers were fitted to the cats' collars and activity monitored continuously from the start of the altrenogest treatment until ovariohysterectomy. Infrared images of the perivulvar, perianal, and gluteal area were taken of each cat on Day 30 and daily from Days 36-45 of the study. Perivulvar temperature (PVT), PVT relative to gluteal temperatures (PVT-GT), and PVT relative to perianal temperature (PVT-PAT) were recorded for each image. Blood samples were collected on Days 0, 10, 30, and 40, immediately prior to the hCG treatment, and at the time of ovariohysterectomy. Serum oestradiol and progesterone concentrations indicated complete ovarian suppression by Day 30 and, together with morphological assessment of the ovaries, confirmed the induction of follicular growth and ovulation in all cats. Daily activity counts differed among cats (P < 0.001), so the daily activity counts of each cat were converted to a proportional change from the average daily activity count from Days 30-39 (defined as the 'proportional daily activity'). Proportional daily activity counts increased after the stimulation of follicular growth with eCG, with peak levels (2.03 ± 0.29-fold higher than pre-treatment levels; P = 0.006) occurring three days after the eCG treatment. The PVT-GT showed the greatest sensitivity to detect subtle changes in body temperature, increasing from early to late follicular growth (1.96 ± 0.33 °C increase from Day 41-43; P < 0.001) and decreasing after hCG-induced ovulation (1.24 ± 0.41 °C decrease from Day 43-45; P = 0.01). In conclusion, both accelerometry and IR thermography show potential as non-invasive, real-time methods for assessing ovarian activity in cats, but further research is required to determine if these methods could be used to monitor natural/non-stimulated oestrous cycles.

Multiple corticosteroid abnormalities in cats with hyperaldosteronism

Background

The frequency with which multiple corticosteroid abnormalities occur in cats with aldosterone secreting adrenocortical tumors is unknown.

Objectives

To evaluate adrenal‐derived corticosteroids in cats in which blood samples were submitted for measure of aldosterone.

Animals

Two hundred ninety‐seven cats.

Methods

Retrospective study. Analysis of a convenience sample of previously submitted serum or plasma. Progesterone, corticosterone, and cortisol were measured in feline serum or plasma samples submitted to an endocrinology laboratory for aldosterone measurements. Demographics and clinical history were retrieved from submittal forms when provided. Statistical testing was performed to investigate associations among the adrenal corticosteroids.

Results

Progesterone and corticosterone concentrations were strongly correlated (ρ = 0.74; P < .001). Progesterone (median, 5 nmol/L; interquartile range, 3‐10 nmol/L) and corticosterone (113 nmol/L, 38‐250 nmol/L) in cats with markedly increased aldosterone concentrations (≥3000 pmol/L) were higher than progesterone (1 nmol/L, 1‐2 nmol/L) and corticosterone (12 nmol/L, 3‐25 nmol/L) in cats with normal aldosterone concentrations (P < .001 for both comparisons). Progesterone concentrations ≥10 nmol/L (normal, ≤2 nmol//L) occurred in 24 of 76 (32%) cats with aldosterone concentrations ≥3000 pmol/L. Cortisol was lower in cats with aldosterone concentrations ≥3000 pmol/L as compared to those with aldosterone concentrations <500 pmol/L (59 nmol/L, 27‐103 nmol/L vs 103 nmol/L, 49‐182 nmol/L; P = .002).

Conclusions and Clinical Importance

Multiple corticosteroid abnormalities occur in a subset of cats with hyperaldosteronism. The magnitude of increases in progesterone and corticosterone in some cats with hyperaldosteronism is likely to be clinically relevant.

Endometrial receptivity and embryo implantation in carnivores-commonalities and differences with other mammalian species

Endometrial receptivity and embryo implantation processes are a major point of pregnancy failure in many mammalian species, including humans. Although reproductive biology in many carnivore species remains enigmatic, the few that have been studied so far are invaluable comparative models. The goals of this review are to (1) summarize current data on the mechanisms involved in uterine receptivity and embryo implantation in carnivores, including commonalities and differences with other mammalian species and (2) identify research priorities to better understand a key phenomenon in a critical group of mammals. Besides unique reproductive traits in some carnivores (induced vs. spontaneous ovulation in cats, ovulation at the germinal vesicle stage in dogs), preimplantation embryo development is comparable with other orders. However, the timing of implantation varies, especially in species having an embryonic diapause. Mechanisms involved in endometrial receptivity and decidualization still remain to be fully understood, but specific markers have already been identified. Importantly, the use of endogenous hormones to control the ovarian activity may impact endometrial receptivity and subsequent embryo implantation. Next, research efforts should take advantage of advanced technologies to further study embryo implantation in carnivores and to provide more relevant models to reproductive medicine or for the conservation of rare and endangered species.