Effects of stress on reproduction in non-rodent mammals: the role of glucocorticoids and sex differences

Emotion recognition and regulation in males: Role of sex and stress steroids

Understanding emotions in males is crucial given their higher susceptibility to substance use, interpersonal violence, and suicide compared to females. Steroid hormones are assumed to be critical biological factors that affect and modulate emotion-related behaviors, together with psychological and social factors. This review explores whether males' abilities to recognize emotions of others and regulate their own emotions are associated with testosterone, cortisol, and their interaction. Higher levels of testosterone were associated with improved recognition and heightened sensitivity to threatening faces. In contrast, higher cortisol levels positively impacted emotion regulation ability. Indirect evidence from neuroimaging research suggested a link between higher testosterone levels and difficulties in cognitive emotion regulation. However, this notion must be investigated in future studies using different emotion regulation strategies and considering social status. The present review contributes to the understanding of how testosterone and cortisol affect psychological well-being and emotional behavior in males.

Gonads under stress: A systematic review and meta-analysis on the effects of acute psychosocial stress on gonadal steroids secretion in humans

Animal research has shown that the hypothalamus-pituitary-gonadal (HPG) axis is inhibited by (chronic and/or severe) stress, which can lead to impaired fertility and reproductive functioning, presumably caused by the inhibition of gonadal steroid secretion and in interactions with glucocorticoids. However, what has not been clarified is how acute psychosocial stress modulates gonadal steroid secretion in humans. Here we summarize the experimental research on the acute effects of stress on the secretion of gonadal steroids in humans. A systematic literature search revealed 21 studies (with N=881 individuals) measuring testosterone, progesterone or estradiol in response to a standardized acute laboratory stressor in healthy humans. Both our literature review and quantitative meta-analysis suggest that in humans, acute stress stimulates rather than inhibits HPG axis activity, although there is a considerable heterogeneity in the reported methods and results. Increased gonadal steroids in response to acute stress contrasts with many animal studies reporting the opposite pattern, at least regarding severe and/or chronic stressors. We discuss methodological issues and challenges for future research and hope to stimulate experimental studies within this area. A better understanding of these mechanisms is needed, and may have important implications for health and disease, as well as the modulation of various behaviors by acute stressors.

The opioid peptide leucine enkephalin modulates hypothalamic-hypophysial axis in the cichlid fish Oreochromis mossambicus

In vertebrates, opioid peptides are thought to be involved in the regulation of reproduction; however, the significance of enkephalins in testicular function remains unclear. We examined the influence of δ-opioid receptor agonist leucine enkephalin (L-ENK) on the hypophysial-testicular axis of the cichlid fish Oreochromis mossambicus. Treatment with a low dose of L-ENK (60 µg) caused a significant increase in the numbers of primary and secondary spermatocytes and early and late spermatids, concomitant with intense immunolabelling of testicular androgen receptors, but did not significantly alter serum luteinizing hormone (LH) and 11-ketotestosterone (11-KT) levels compared to those of controls. Nevertheless, treatment with a high dose of L-ENK (200 µg) caused a significant reduction in the numbers of secondary spermatocytes as well as late spermatids associated with marginal immunolabelling of androgen receptors and significantly lower concentrations of serum 11-KT and LH compared to controls. In addition, the serum cortisol level was not affected in low-dose L-ENK-treated fish, but its level was significantly increased in the high-dose L-ENK-treated group. Together, these findings indicate that a low dose of L-ENK stimulates the germ cells at the meiosis stage and promotes further stages of spermatogenesis, whereas a high concentration of L-ENK inhibits spermatogenesis at the advanced stages. This effect appears to be mediated through the suppression of testicular steroidogenesis and the reduction of LH release in the pituitary gland of tilapia. The findings also suggest that elevated L-ENK levels in teleosts may exert their inhibitory influence on the hypophysial-testicular axis via glucocorticoids.

Finding biomarkers of experience in animals

At a time when there is a growing public interest in animal welfare, it is critical to have objective means to assess the way that an animal experiences a situation. Objectivity is critical to ensure appropriate animal welfare outcomes. Existing behavioural, physiological, and neurobiological indicators that are used to assess animal welfare can verify the absence of extremely negative outcomes. But welfare is more than an absence of negative outcomes and an appropriate indicator should reflect the full spectrum of experience of an animal, from negative to positive. In this review, we draw from the knowledge of human biomedical science to propose a list of candidate biological markers (biomarkers) that should reflect the experiential state of non-human animals. The proposed biomarkers can be classified on their main function as endocrine, oxidative stress, non-coding molecular, and thermobiological markers. We also discuss practical challenges that must be addressed before any of these biomarkers can become useful to assess the experience of an animal in real-life.

The effects of heat stress on intrauterine development, reproductive function, and ovarian gene expression of F1 female mice as well as gene expression of F2 embryos†

Exposure to heat stress (HS) in utero was postulated to trigger an adaptive molecular response that can be transmitted to the next generation. Hence, this study assessed the impact of HS exposure at different stages of the gestational period of mice on the female F1 population and their offspring. Heat stress exposure (41°C and 65% relative humidity-RH) occurred during the first half (FP), the second half (SP), or the entire pregnancy (TP). A control group (C) was maintained in normothermic conditions (25°C, 45% RH) throughout the experiment. Heat stress had a significant negative effect on intrauterine development, mainly when HS exposure occurred in the first half of pregnancy (FP and TP groups). Postnatal growth of FP and TP mice was hindered until 4 weeks of age. The total number of follicles per ovary did not vary (P > 0.05) between the control and HS-exposed groups. Mean numbers of primordial follicles were lower (P < 0.05) in the sexually mature FP than those in SP and TP F1 females. However, the mean number of viable embryos after superovulation was lower (P < 0.05) in TP compared with C group. The expression of genes associated with physiological and cellular response to HS, autophagy, and apoptosis was significantly affected in the ovarian tissue of F1 females and F2 in vivo-derived blastocysts in all HS-exposed groups. In conclusion, exposure to HS during pregnancy compromised somatic development and reproductive parameters as well as altered gene expression profile that was then transmitted to the next generation of mice.

ACTH impairs the migratory and secretory profile of mononuclear cells during proestrus in cattle

The aim was to evaluate the effect of ACTH on the mechanisms involved in peripheral blood mononuclear cells (PBMCs) infiltration into the ovary during dairy cattle proestrus. Regarding this, proper expression pattern of adhesion molecules must take place both in PBMCs and in endothelial cells. Argentinian Holstein cows (n = 12) were treated with 100 IU of ACTH every 12 h for 4 days before ovulation when ovariectomy was performed (day 18). Blood samples were taken on day 15 (0 h) and immediately before (72 h) and after (74 h) the last ACTH administration. In PBMCs, flow cytometry was performed to analyze CD44, CD11b and CD62-L expression along with gene expression of chemokines' receptors. Interleukin (IL)-4 and tumor necrosis factor-α (TNF-α) production was analyzed by flow cytometry after exposing PBMCs to autologous follicular fluid. In ovarian blood vessels, expression of the vascular endothelium cell adhesion-1 (VCAM-1) and the platelet endothelial cell adhesion molecule-1 was evaluated by immunohistochemistry. In T-lymphocytes, the expression of CD44 and CD11b was lower at 72 h in ACTH-treated cows (P < 0.05). In monocytes, the expression of CD11b and CD62-L was lower at 72 h in ACTH-treated cows (P < 0.05). Also, the percentage of IL-4+ cells was higher in ACTH-treated cows, meanwhile, the percentage TNF-α+ cells was lower in ACTH-treated cows (P < 0.05). Finally, in the vessels associated with the preovulatory follicle VCAM-1 immunoexpression was lower in ACTH-treated cows (P < 0.05). Here, we present novel insights into the effect of stress during the preovulatory period on the inflammatory pathway necessary for ovulation.

Hypothalamus and Post-Traumatic Stress Disorder: A Review

Humans have lived in a dynamic environment fraught with potential dangers for thousands of years. While fear and stress were crucial for the survival of our ancestors, today, they are mostly considered harmful factors, threatening both our physical and mental health. Trauma is a highly stressful, often life-threatening event or a series of events, such as sexual assault, war, natural disasters, burns, and car accidents. Trauma can cause pathological metaplasticity, leading to long-lasting behavioral changes and impairing an individual's ability to cope with future challenges. If an individual is vulnerable, a tremendously traumatic event may result in post-traumatic stress disorder (PTSD). The hypothalamus is critical in initiating hormonal responses to stressful stimuli via the hypothalamic-pituitary-adrenal (HPA) axis. Linked to the prefrontal cortex and limbic structures, especially the amygdala and hippocampus, the hypothalamus acts as a central hub, integrating physiological aspects of the stress response. Consequently, the hypothalamic functions have been attributed to the pathophysiology of PTSD. However, apart from the well-known role of the HPA axis, the hypothalamus may also play different roles in the development of PTSD through other pathways, including the hypothalamic-pituitary-thyroid (HPT) and hypothalamic-pituitary-gonadal (HPG) axes, as well as by secreting growth hormone, prolactin, dopamine, and oxytocin. This review aims to summarize the current evidence regarding the neuroendocrine functions of the hypothalamus, which are correlated with the development of PTSD. A better understanding of the role of the hypothalamus in PTSD could help develop better treatments for this debilitating condition.

Non-invasive Assessment of Fecal Glucocorticoid and Androgen Metabolites in the Pygmy Hippopotamus (Choeropsis liberiensis)

The pygmy hippopotamus (Choeropsis liberiensis) is an endangered species endemic to the Upper Guinea Forest ecosystem in West Africa. We have limited information concerning the species' reproduction and well-being under managed care. We therefore developed non-invasive methods for characterizing gonadal androgen and adrenal hormone profiles in pygmy hippos using fecal samples collected from 12 males and 12 females housed in North American zoological institutions. We aimed to: 1) identify and validate enzyme immunoassays (EIAs) for measuring metabolites of corticosteroids and testosterone in feces; and 2) test whether gonadal activity is correlated with previous breeding history, season or type of housing. For glucocorticoids, several EIAs for measuring metabolites were investigated. A group-specific EIA exhibiting cross-reactivity with 11,17-dioxoandrostane (DOA) metabolites of cortisol most clearly reflected adrenocortical activity in response to ACTH¹ challenge in both males and females. However, day-to-day concentrations of this metabolite in the feces of pygmy hippos that did not undergo ACTH challenge were near the detection limits of the assay, making this EIA impractical for assessing glucocorticoid activity in this species. Another group-specific EIA, exhibiting cross-reactivity with 5α-pregnane-3β,11β,21-triol-20-one, produced biologically relevant data and evidence of an appropriate response to pharmacological challenge with exogenous ACTH. The testosterone metabolite assay C196 (Arbor Assays, Ann Arbor, Michigan, USA) also produced biologically coherent data: adult males exhibited the highest mean androgen metabolite concentrations (477 ng/g), followed by adult females (259 ng/g) and juvenile males (160 ng/g). Proven breeding males had higher, but not significantly different, mean concentrations (472 ng/g) to unproven males (352 ng/g; P = 0.400). Similarly, adult males housed outdoors year-round in subtropical climates exhibited higher, but not statistically different mean concentrations (554 ng/g) to males in temperate climates that were housed indoors at least part of the year (412 ng/g; P = 0.208). There were, however, significant differences in mean concentrations among seasons for adult males, with higher values in spring (546 ng/g) and summer (542 ng/g) than in autumn (426 ng/g) and winter (388 ng/g, P = 0.003). In conclusion, we identified EIAs for the measurement of fecal metabolites of androgens and glucocorticoids that can be used for further studies to monitor gonadal activity in male pygmy hippos and adrenocortical activity in both sexes. We also identified a seasonal trend in male gonadal activity in this species under managed care in North America. Finally, our findings highlight an important consideration when using non-invasive methods for evaluating fecal cortisol metabolites: ACTH used for pharmacological validation of an EIA does not necessarily equate to biological relevance.

In ovo corticosterone exposure does not influence yolk steroid hormone relative abundance or skeletal muscle development in the embryonic chicken

In ovo corticosterone (CORT) exposure reportedly reduces growth and alters body composition traits in meat-type chickens. However, the mechanisms governing alterations in growth and body composition remain unclear but could involve myogenic stem cell commitment, and/or the presence of yolk steroid hormones. This study investigated whether in ovo CORT exposure influenced yolk steroid hormone content, as well as embryonic myogenic development in meat-type chickens. Fertile eggs were randomly divided at embryonic day (ED) 11 and administered either a control (CON; 100 µL of 10 mM PBS) or CORT solution (100 µL of 10 mM PBS containing 1 µg CORT) into the chorioallantoic membrane. Yolk samples were collected at ED 0 and ED 5. At ED 15 and hatch, embryos were humanely killed, and yolk and breast muscle (BM) samples were collected. The relative abundance of 15 steroid hormones, along with total lipid content was measured in yolk samples collected at ED 0, ED 5, ED 15, and ED 21. Muscle fiber number, cross-sectional area, and fascicle area occupied by muscle fibers were measured in BM samples collected at hatch. Relative expression of MyoD, MyoG, Pax7, PPARγ, and CEBP/β, and the sex steroid receptors were measured in BM samples collected at hatch. The administration of CORT had a limited effect on yolk steroid hormones. In ovo CORT significantly reduced fascicle area occupied by muscle fibers and CEBP/β expression was increased in CORT exposed birds at hatch. In addition, the quantity of yolk lipid was significantly reduced in CORT-treated birds. In conclusion, in ovo exposure to CORT does not appear to influence early muscle development through yolk steroid hormones in embryonic meat-type chickens however, the results provide a comprehensive analysis of the composition of yolk steroid hormones in ovo at different developmental time points. The findings may suggest increased mesenchymal stem cell commitment to the adipogenic lineage during differentiation and requires further investigation.

Validation of Enzyme Immunoassays via an Adrenocorticotrophic Stimulation Test for the Non-Invasive Quantification of Stress-Related Hormone Metabolites in Naked Mole-Rats

Small size in mammals usually restricts long-term, frequent monitoring of endocrine function using plasma as a matrix. Thus, the non-invasive monitoring of hormone metabolite concentrations in excreta may provide an invaluable approach. The aim of the current study was to examine the suitability of enzyme immunoassays (EIAs) for monitoring responses to stressors in the naked mole-rat (Heterocephalus glaber, NMR) using urine and feces as hormone matrices. A saline control administration, and a high- and low-dose adrenocorticotropic hormone (ACTH) challenge were performed on six male and six female disperser morph NMRs. The results revealed that a 5α-pregnane-3β,11β,21-triol-20-one EIA detecting glucocorticoid metabolites (GCMs) with a 5α-3β-11β-diol structure is the most suitable assay for measuring concentrations in male urine samples, whereas an 11-oxoaetiocholanolone EIA detecting GCMs with a 5β-3α-ol-11-one structure appears the most suitable EIA for quantifying GCMs in female urine. An 11-oxoaetiocholanolone EIA detecting 11,17 dioxoandrostanes was the most suitable EIA for quantifying GCMs in the feces of both sexes. There were sex-related differences in response to the high- and low-dose ACTH challenge. We recommend using feces as a more suitable matrix for non-invasive GCM monitoring for NMRs which can be valuable when investigating housing conditions and other welfare aspects.

Elevated glucocorticoids during the ovarian follicular phase predict conception in wild female chacma baboons

Mating related behavior during ovarian cycling can be energetically demanding and constitute a significant stressor, requiring physiological responses to mediate investment in reproduction. To better understand the proximate mechanisms underlying these responses, we examine hormonal and behavioral variation across the ovarian cycle during conceptive and nonconceptive cycles in wild female chacma baboons (Papio ursinus). We quantified immunoreactive fecal estradiol, progesterone, and cortisol metabolites for 21 adult females, and calculated activity budgets and rates of received aggression from over 5000 15-min behavioral samples. We found conception to be associated with higher concentrations of both estradiol and cortisol during the follicular phase, but no difference in progesterone between conceptive and nonconceptive cycles for either the follicular or luteal phase. While females spent less time feeding during the follicular compared to the luteal phase, we found no difference in time spent feeding, moving, or copulating between conceptive and nonconceptive cycles of the same phase. Rates of received aggression also were similar across the ovarian cycle, with no difference between conceptive and nonconceptive cycles. Finally, we found positive associations between cortisol and estradiol, indicating that glucocorticoids (GCs) do not suppress hypothalamic-pituitary-gonadal (HPG) activity and reproductive function in this context. Overall, our results suggest that elevated GCs may play an adaptive role in mobilizing energy during sexually receptive periods of ovarian cycling.

Effects of chronic exposure to cold stress on ovarian functions in prepubertal rats

Ovarian functions are modulated by the hypothalamus-pituitary-ovary axis and neural signals. Stress modifies the activity of the sympathetic nervous system. In adult female rats, cold stress results in higher noradrenergic and steroidogenic activity of the ovary, anovulation and the presence of ovarian cysts; however, it is unknown whether this response occurs in prepubertal rats. The purpose of this study was to analyse the effects of cold stress initiated in the prepubertal stage of female rats on ovarian function. Female rats 24 days old were exposed to three, five or eight weeks of cold stress. Autopsies were performed at the end of each stress period. The parameters analysed were the number of ova shed by ovulating animals; the number of ovulating animals; the serum concentrations of progesterone, testosterone, and oestradiol; and the ovarian concentrations of norepinephrine and 3-methoxy-4-hydroxyphenyl-glycol. Our results show that chronic cold stress applied to prepubertal rats did not modify the number of ovulating animals, the total number of ova shed, or progesterone and testosterone concentrations in any of the periods analysed. Oestradiol concentration was lower in the animals exposed to five or eight weeks of stress. The ovarian norepinephrine concentration was higher in the animals exposed to three weeks of stress and was lower at eight weeks of stress. No changes in ovarian morphology were observed. Our data suggest that the changes in noradrenergic activity resulting from chronic cold stress experienced in the prepubertal stage do not modify ovarian architecture or affect the ovulatory response in adulthood.

Assessment of lipids and adrenal hormones in the Florida manatee (Trichechus manatus latirostris) from different habitats

Florida manatees (Trichechus manatus latirostris), a federally protected species, are classified as threatened due to anthropogenic stressors. Manatees inhabit sites that are impacted by human activities that can negatively affect stress physiology and metabolism. Samples collected from healthy manatees (pregnant females, non-pregnant females, and males) at Crystal River and Indian River Lagoon in Florida, were assessed for adrenal hormones, proteins, glucose, and lipid content in plasma. The objective was to determine if healthy manatees sampled between 2010-2014 from the Indian River Lagoon exhibited evidence of stress compared to healthy manatees sampled between 2012-2019 from Crystal River. Plasma cortisol concentrations were not different in male and non-pregnant female manatees between sites but were elevated in pregnant manatees. Plasma aldosterone concentrations were elevated in Indian River Lagoon manatees relative to those at Crystal River, possibly due to differences in salinity and available freshwater between the two environments. Site differences were noted for plasma protein and glucose concentrations in manatees; additionally, differences between the sexes were also observed in glucose concentrations. Fifteen lipid subclasses, including oxidized lysophosphatidylcholines, oxidized phosphatidylcholines, oxidized triacylglycerols, were elevated in manatees from the Indian River Lagoon relative to manatees from Crystal River. Evidence of a stress response in healthy Indian River Lagoon manatees was lacking compared to Crystal River manatees. Differences in metabolites related to energy (glucose, protein, and lipids) may be related to site-specific variables, such as salinity and food availability/quality. This study generates novel data on plasma lipid profiles and provides cortisol, aldosterone, glucose, and protein values from healthy Florida manatees in two disparate sites that can be referenced in future studies. These data contribute to an improved understanding of manatee physiology to better inform population management.

Laissez-Faire Stallions? Males' Fecal Cortisol Metabolite Concentrations Do Not Vary with Increased Female Turnover in Feral Horses (Equus caballus)

Stress responses can be triggered by several physical and social factors, prompting physiological reactions including increases in glucocorticoid concentrations. In a population of feral horses (Equus caballus) on Shackleford Banks, North Carolina, females previously immunized with the immunocontraceptive agent porcine zona pellucida (PZP) change social groups (bands) more often than unimmunized females, disrupting the social stability within the population. We assessed the effects of increased female group changing behavior (or female turnover) on individual male stress by comparing fecal cortisol metabolite (FCM) concentrations among stallions experiencing varying amounts of female group changing behavior. FCM concentrations did not significantly correlate with female turnover. Similarly, FCM concentrations were not dependent upon the timing of female group changing behavior. These findings suggest that female turnover rate has little influence on physiological measures of stress in associated stallions. That said, Shackleford stallions experiencing increased female turnover do engage in behaviors typically associated with stress (increased vigilance, highly escalated male-male conflicts). Future work should compare FCM concentrations across time within populations and among populations managed under different strategies to better isolate factors influencing stallion stress physiology. Such studies are especially important if we are to determine how changes in female behavior related to immunocontraception impact physiological and behavioral indicators of stress for non-target animals. Finally, our study highlights the importance of considering both physiological and behavioral measures when investigating animal responses to potentially challenging situations.

Temperature Extreme Events Decrease Endocrine and Immune Reactive Scope in Bullfrogs (Lithobates catesbeianus)

Currently, effects of increased atmospheric temperature, in the context of ongoing climate change, have been investigated in multiple organisms and levels of biological organization. While there has been a focus on the impacts of increased mean temperature, an emergent and equally important point is the consequences of recurrent exposure to extreme temperature events, simulating heat waves. This study investigated the effects of serial exposure to high temperatures on immune and endocrine variables before and after exposure to an acute secondary stressor in bullfrogs (Lithobates catesbeianus). Adult males were divided into three groups and subjected to three thermal regimes: control (c; constant 22°C); experimental 1 (E1; kept at 22°C and exposed to 4 days of 30°C every 16 days); and experimental 2 (E2; kept at 22°C and exposed to 4 days of 30°C every 6 days). Blood samples were collected on the last day of key extreme heat events. Two weeks after the last extreme heat event, animals were subjected to restraint stress (1 h) and sampled again. Blood samples were used to determine neutrophil: lymphocyte ratio, plasma bacterial killing ability, as well as, corticosterone and plasma testosterone levels. Overall, we found exposure to extreme heat events did not affect immune and endocrine variables over time. Meanwhile, the previous exposure to extreme heat events modulated the responsiveness to restraint. The amplitude of increased corticosterone plasma levels and neutrophil: lymphocyte ratio in response to restraint decreased with the number of previous exposures to extreme heat events. These results suggest that exposure to extreme climatic events has hidden effects on bullfrog's stress response, expressed as diminished reactive scope to a novel stressor. This represents a highly deleterious facet of climate change since diminished responsiveness prevents proper coping with wildlife challenges.

Behavioral restriction, lorazepam, and escitalopram uniquely influence the expression of naturalistic stereotypy in deer mice: perspectives on anxiety- and compulsive-like behavior

Introduction: Stereotypical expression in laboratory-housed rodents can be explained by different motivational, coping, and motor dysfunction theories. Here, we aimed to explore the neurocognitive underpinnings of high stereotypical (HS) expression in deer mice (Peromyscus maniculatus bairdii), previously proposed as a model system of compulsive-like behavioral persistence. Specifically, we aimed to establish whether HS behavior is related to an underlying escape-related trigger. Methods: One-hundred and sixteen deer mice were classified as either non-stereotypical (NS) or HS. Mice of each cohort were further subdivided and exposed to either sub-acute (3-day) or chronic (25-day) behavioral restriction (R), and high-dose escitalopram (ESC), lorazepam (LOR), alone and in combination with R (ESC+R and LOR+R, respectively). Mice were reassessed for stereotypical behavior at both time points. Results: Our results indicate that HS behavior is likely not temporally and functionally related to an anxiogenic trigger, i.e., R, but rather that HS is associated with parallel changes in anxiogenic feedback processing. We also show that chronic R alone significantly decreased the time spent in expressing HS behavior in animals of the HS, but not NS phenotype. Discussion: This points to the possibility that HS-expressing mice represent a subgroup of P. maniculatus bairdii in which unique interactions between neurobiology and processes of gradual behavioral organization, may contribute to the expression of the typical behaviors observed in this cohort. Collectively, our findings highlight the value of the deer mouse model system to investigate the potential neurocognitive mechanisms that may underlie the development of persistent phenotypes that can likely not be explained entirely by current theories.

Prenatal Restraint Stress-Induced Maternal Exposure and Clomifene Citrate Administration Modulates Reproductive Programming in Female Wistar Rats

&lt;b&gt;Background and Objective:&lt;/b&gt; Infertility and maternal stress studies have become major public health problems in most societies and this has attracted urgent global attention. This study examined the modulatory role of restraint-induced stress and clomiphene citrate (CC) administration on the reproductive programming of Wistar rats. &lt;b&gt;Materials and Methods:&lt;/b&gt; A total of 119 healthy Wistar rats weighing between 150-200 g were used and assigned into four major groups. Stress was induced for 1, 2, 4 and 6 hrs daily by exposure of the rats to a restraint plastic chamber for 1 and 2 weeks, respectively. At the end of each experimental protocol, the animals were euthanized by cervical dislocation and serum samples were collected for hormonal assay. The average gestational length, litter size and pup weight were examined. Data were expressed as Mean±SEM and mean differences were analyzed using One-way (ANOVA) and LSD &lt;i&gt;post hoc&lt;/i&gt; Test with SPSS 23 at p<0.05 level of significance. &lt;b&gt;Results:&lt;/b&gt; These findings showed that restraint stress caused a significant elevation in corticosterone level, while estrogen, progesterone, follicle-stimulating hormone and luteinizing hormone were significantly reduced when compared with control. Gestation length and litter size were also significantly reduced by stress while pup weights were not significantly affected. The CC increased litter size in unstressed rats when compared to litters of stressed rats that were significantly reduced, although, CC was able to increase the litter size of stressed rats towards normal. &lt;b&gt;Conclusion:&lt;/b&gt; Evidence indicated that stress alters reproductive potential in female rats and also, reduces the effectiveness of CC in inducing ovulation.

Validation of an enzyme immunoassay for measurement of fecal dehydroepiandrosterone sulfate in gibbons and siamangs

Monitoring wildlife stress levels is essential to ensure their quality of life in captivity or in the wild. One promising method to assess the stress response is the comeasurement of glucocorticoids (GC) and dehydroepiandrosterone sulfate (DHEAS), adrenal hormones involved in the modulation of the stress response. Although noninvasive methods to measure GCs have been validated in several species, only a few studies have validated DHEAS assays. The aims of this study were (1) to describe an enzyme immunoassay (EIA) to measure DHEAS levels, (2) to validate this assay for fecal samples in gibbons and siamangs, and (3) to test hormonal stability after one freeze-thaw cycle and over time at two freezer temperatures (-20°C and -80°C). Subjects included 32 gibbons and siamangs from U.S. zoological parks. The EIA was validated analytically by parallelism and accuracy tests, and biologically by confirming a DHEAS response 1-2 days after a stressful event (accident, vaccination, or transportation) in three individuals. In addition, fecal DHEAS levels in a pregnant female were above nonpregnant/nonlactating levels and declined progressively the following parturition. The hormonal stability experiments revealed no significant changes in fecal DHEAS levels after one freeze-thaw cycle. Hormonal levels in fecal extracts were stable for 2 months, regardless of the storage temperature, with no significant differences between -20°C and -80°C conditions. The EIA described has high sensitivity and it is suitable for fecal DHEAS measurement in gibbons and siamangs, with a potential to be applied to other species.

Testosterone, cortisol, and criminal behavior in men and women

Only two studies to date have considered the joint effects of testosterone and cortisol on direct measures of criminal behavior. The current study extends this earlier work by incorporating the direct and interactive effects of baseline hormone measures and hormone change scores in response to social stress. The current study also extends prior work by considering distinct measures of different criminal behavior types and sex differences. Analyses based on a large sample of undergraduates indicated that testosterone had a positive and statistically significant association with impulsive and violent criminal behavior. The interaction of testosterone with cortisol had a negative association with income generating crime. Simple slopes analyses of this interaction indicated testosterone had a positive association with income generating crime when cortisol was low (-1 SD). Associations between hormones and criminal behavior were not moderated by sex.

Cortisol awakening response and testosterone jointly affect adolescents' theory of mind

Adolescence is a critical period for the maturation of neurobiological processes and hormone secretion. Recent studies on the dual-hormone hypothesis have indicated that basal cortisol and testosterone jointly affect dominant and aggressive behavior among adolescents and adults. Whether this hypothesis applies to prosocial-related understanding of others' mental states remains unclear. The present study investigated associations between basal testosterone, basal cortisol (and cortisol awakening response [CAR]), and the cognitive/affective theory of mind (ToM) in 243 adolescents (67.9 % male, aged 14 to 17 years, M_age = 16.09, standard deviation = 0.62). Cognitive ToM (cToM) and affective ToM (aToM) were assessed with a cartoon story reasoning task: In the cToM condition, participants viewed a comic strip story and needed to predict what would happen based on a character's intentions, and in the aToM condition, they viewed a comic strip of two characters interacting and needed to think about what would make the protagonist feel better. The results showed that basal testosterone and basal cortisol did not interact with each other to affect the performance of ToM, either in terms of ToM accuracy or response speed. However, under the condition of low CAR, testosterone is associated with the fast performance of cToM, although the interaction of testosterone and CAR occurred only in female adolescents. Overall, our data provide new evidence for the dual-hormone hypothesis and further extend the hypothesis to social understanding.

Satisfactory breeding potential is transiently eliminated in beef bulls with clinical anaplasmosis

Background

Natural service breeding is common in U.S. cow-calf operations. Diseases impacting bull reproductive performance have significant economic consequences for producers. Anaplasmosis may be an underappreciated cause of poor reproductive performance in bulls. The primary systemic effects of bovine anaplasmosis including anemia, fever, and weight loss, can all result in unsatisfactory reproductive performance. The objective of this pilot study was to evaluate breeding soundness examination (BSE) outcomes and clinical changes in bulls during and upon resolution of clinical anaplasmosis. Anaplasma marginale-challenged bulls were observed for clinical disease and infection progression and changes in breeding soundness compared to uninfected control bulls for 16 weeks.

Results

All Anaplasma marginale-challenged bulls were PCR-positive, seropositive, and showed clinical signs by 3-, 17-, and 24-days post-challenge, respectively. Clinical signs of anaplasmosis included pallor, icterus, fever (≥ 40.2 °C), and weight loss. Acute anemia was observed in all challenged bulls with PCV nadirs ≤ 18% and peak percent parasitized erythrocyte ≥ 50%. Decreased scrotal circumference and poor semen quality (e.g., increased percentage of abnormal spermatozoa, decreased progressively motile sperm), were initially observed within days after onset of clinical anaplasmosis signs and continued weeks beyond disease resolution. Control bulls remained negative for A. marginale.

Conclusion

This pilot study demonstrates that clinical anaplasmosis reduces breeding soundness in beef bulls. Anaplasmosis should be considered as a differential for bulls with decreased semen quality, especially within endemic areas. A 90 day or greater retest window is recommended for bulls of unsatisfactory breeding potential recently recovered from clinical anaplasmosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03470-7.

Naturally stressed? Glucocorticoid profiles in blubber of blue and gray whales in response to life history parameters

The goal of the present study was to carry out a thorough methodological validation and describe baseline profiles for glucocorticoid hormones (cortisol and corticosterone) in blubber from blue (n = 77) and gray (n = 103) whales from the eastern North Pacific Ocean. For each species, we modelled cortisol and corticosterone concentrations in response to life history parameters (age, sex, reproductive status) and season or geographic location. In blue whales, cortisol concentrations did not vary significantly by age class, sex, or reproductive status, whereas corticosterone was significantly lower in immature than in adult females (p < .001). In gray whales, cortisol concentrations were significantly higher in lactating whales (p < .05), while corticosterone was significantly different between females and males (p = .001) and elevated in calves (p = .003). In gray whales, corticosterone concentrations were significantly lower in males sampled later in the year (August to November) compared to both sexes sampled between March and August (p = .05), but no seasonal trend occurred in blue whales. Our results indicate that glucocorticoid actions vary between species and sex in large whales. Analysis of multiple hormones improves our understanding of the physiology of maintaining metabolic homeostasis or coping with chronic stressors.

Performance of Marmoset Monkeys as Embryo Donors Is Reflected by Different Stress-Related Parameters

Non-human primates (NHPs) serve as embryo donors for embryo collection in order to mimic genetic diseases in humans by genetic modification. Reproductive health of the embryo donors is crucial, and chronic distress needs to be avoided. Embryo retrieval rates (ERR), anti-Müllerian hormone (AMH) concentrations, cortisol levels, and body weight fluctuations were assessed as markers for fertility and distress. With regard to successful embryo retrievals (total n = 667), the animals were either used for extended periods (long-term group; LTG) or only for short periods (short-term group; STG). Retrospective evaluation expectedly showed that animals in the LTG had a higher ERR than animals in the STG (p < 0.0001). Importantly, ERR in the LTG remained stable throughout the experimental period, and high embryo rates were already encountered during the first year of experimental use (p = 0.0002). High ERR were associated with high AMH and low cortisol levels, and minimal body weight fluctuations following anesthesia, indicating a superior ability of the LTG animals to handle distress. We conclude that the long-term experimental use of marmosets does not impair their fertility or health status per se, supporting the view that animal reuse can be in accordance with the 3R-principle, implying reduction, replacement, and refinement in animal experimentation.

Redox Status and Hematological Variables in Melatonin-Treated Ewes during Early Pregnancy under Heat Stress

The preovulatory follicles and preimplantation stage embryos are found to be rather sensitive to heat stress due to their low potential for scavenging reactive oxygen species (ROS). The aim of the present study was to assess the impact of melatonin administration on redox status and hematological variables during the preovulatory period and early stages of embryogenesis in heat-stressed ewes in vivo. Forty Karagouniko-breed ewes were divided in two groups, the melatonin (M, n = 20) group and control (C, n = 20) one. All animals were subjected to heat stress throughout the study, which lasted forty days (D0 to D40). In M group, melatonin implants were administered on D0. Then, oestrous synchronization was applied (D19-D33). On D34, six rams were introduced into the ewe flock for mating. Ultrasonographic examination was conducted on D73 for pregnancy diagnosis. The temperature humidity index (THI), the rectal temperature (RT), and the number of breaths per minute (BR) were evaluated twice daily. Redox biomarkers, namely total antioxidant capacity (TAC), reduced glutathione (GSH), and thiobarbituric acid reactive substances (TBARS), were assayed in blood samples collected on D0, D33, and D40. In addition, packed cell volume (PCV), white blood cells (WBCs), leukocyte differential count, and cortisol assessment were conducted in blood samples on D33 and D40. The results indicated improved fertility rate and mean number of lambs born per ewe due to improved redox status (p < 0.05) in ewes that received melatonin implants 34 days approximately before the onset of oestrus. The PCV decreased in both groups between the two time-points (p < 0.05). However, the NEU/LYMPH ratio decreased (p < 0.05) only in group M. The low cortisol levels and the decreased NEU/LYMPH ratio in both groups support the hypothesis that ewes of the indigenous Karagouniko breed may exhibit adaptation to environmental thermal stress. The administration of melatonin as an antioxidant regime may improve the reproductive competence of heat stressed ewes and may also enhance their ability to adapt at high ambient temperatures.

Opioidergic pathways and kisspeptin in the regulation of female reproduction in mammals

Endogenous opioid peptides have attracted attention as critical neuropeptides in the central mechanism regulating female reproduction ever since the discovery that arcuate dynorphin neurons that coexpress kisspeptin and neurokinin B (NKB), which are also known as kisspeptin/neurokinin B/dynorphin (KNDy) neurons, play a role as a master regulator of pulsatile gonadotropin-releasing hormone (GnRH) release in mammals. In this study, we first focus on the role of dynorphin released by KNDy neurons in the GnRH pulse generation. Second, we provide a historical overview of studies on endogenous opioid peptides. Third, we discuss how endogenous opioid peptides modulate tonic GnRH/gonadotropin release in female mammals as a mediator of inhibitory internal and external cues, such as ovarian steroids, nutritional status, or stress, on reproduction. Then, we discuss the role of endogenous opioid peptides in GnRH surge generation in female mammals.

Hormone ratios suffer from striking lack of robustness to measurement error

Hormone ratios are often used to capture the joint effect (or "balance") of two hormones with opposing or mutually suppressive effects. Despite some statistical and interpretative problems, hormone ratios are being increasingly used to examine associations of testosterone/cortisol, estradiol/progesterone, testosterone/estradiol, and other hormone pairs. Here we discuss a methodological problem that has not been previously recognized, namely, the striking lack of robustness of raw hormone ratios in the face of measurement error. Hormone levels are measured with error, both due to inability of assays to perfectly assess concentrations "in the tube" and due to discrepancies between levels at the time of sample collection and effective levels that produce the physiological and/or behavioral effect of interest. Noise in measured hormone levels can be substantially exaggerated by ratios, especially when the distribution of the hormone at the denominator is positively skewed, as is frequently observed. To evaluate the extent of this problem and explore the conditions that exacerbate it, we present two sets of simulations, one using idealized distributions and one using empirically observed distributions from studies of estrogen and progesterone. Results show that the validity of raw hormone ratios-the correlation between measured levels and underlying effective levels-drops rapidly in the presence of realistic levels of measurement error. Log-ratios are much more robust to measurement error, and their validity is more stable across samples; under some conditions (e.g., moderate amounts of noise with positively correlated hormone levels), they may provide a more valid measurement of the underlying raw ratio than the measured raw ratio itself. These findings have important implications for research that uses hormone ratios as predictors.

Corticosterone in three species of free-ranging watersnakes: Testing for reproductive suppression and an association with body condition

The potentially suppressive effects of the hypothalamic-pituitary-adrenal (HPA) axis on the hypothalamic-pituitary-gonadal (HPG) axis revolve around the central role that glucocorticoids play in mobilizing energy. As an individual's energy balance becomes negative, the HPA axis helps mobilize energy and shifts energy expenditure away from reproduction toward maintenance and survival. While there is evidence in support of these relationships, substantial species variability exists. Studies in a greater diversity of species promise to enhance our understanding of the interactions between these axes. In this field study we tested for relationships among body condition, corticosterone, and sex steroid concentrations in three species of closely related watersnakes: the common watersnake (Nerodia sipedon), the diamondback watersnake (Nerodia rhombifer) and the queen snake (Regina septemvittata). Snakes were sampled before and after a 30 min acute confinement stressor and body condition was estimated using the scaled mass index. All three species exhibited robust elevations of corticosterone in response to acute stress, but only plasma progesterone was elevated by the acute stressor in queen snakes. There was no evidence for a suppression of sex steroid concentrations in any of the species. Body condition was negatively associated with baseline corticosterone in queen snakes and with post-stressor corticosterone in both queen and common watersnakes. Overall we found fairly strong support for the proposed link between corticosterone and energetics in two of the three watersnake species, but no support for the hypothesis that acute stressors are associated with reproductive suppression, at least as measured by steroid concentrations.

Sex, not social behavior, predicts fecal glucocorticoid metabolite concentrations in a facultatively social rodent, the highland tuco-tuco (Ctenomys opimus)

Social relationships may influence circulating glucocorticoid levels, particularly in group-living species in which individuals regularly engage in interactions with conspecifics. The effects of such interactions appear to vary, with greater social contact being associated with increased glucocorticoid concentrations in some species but decreased concentrations in others. These distinct responses raise intriguing questions regarding relationships among social behavior, individual phenotypes, and glucocorticoid physiology. To explore such relationships in a free-living mammal with a dynamic social organization, we quantified variation in baseline glucocorticoids in a population of highland tuco-tucos (Ctenomys opimus) from Jujuy Province, Argentina. These subterranean rodents are facultatively social, with lone and group-living individuals regularly occurring within the same population. To assess potential endocrine correlates of this behavioral variability, we examined differences in baseline fecal glucocorticoid metabolite (fGCm) concentrations as a function of social group size and composition as well as several metrics of social behavior derived from social network analyses. Despite marked variability in social relationships among the 37 (12 male, 25 female) free-living tuco-tucos sampled, none of the measures of social behavior examined were significant predictors of variation in fGCm concentrations. In contrast, individual variation in glucocorticoid metabolites was best explained by sex, with males having higher fGCm concentrations than females. These analyses provide the first characterization of the glucocorticoid physiology of highland tuco-tucos and underscore the potential importance of intrinsic phenotypic factors (e.g., sex) in shaping glucocorticoid variation in free-living mammals.

Preliminary Findings on How Different Management Systems and Social Interactions Influence Fecal Glucocorticoid Metabolites in White Rhinoceros (Ceratotherium simum)

Simple Summary

In recent years, interest in improving the welfare of wild species in captivity has grown. The aim of this investigation was to evaluate the effects of different social environments and management systems on the cortisol secretion of fourteen white rhinoceroses (Ceratotherium simum) living under different conditions by using use noninvasive methods. The fecal glucocorticoid metabolite secretion was found to be affected by both management systems and social interactions. Additionally, sex is another factor that seems to influence. This research provides a deeper understanding of glucocorticoid production in white rhinoceroses, but more studies are needed to fully understand its influence on reproductive biology.

Abstract

White rhinoceroses (Ceratotherium simum) are the most social and gregarious species of all rhinoceroses known worldwide. One of the most critical effects of elevated glucocorticoid concentrations, especially in threatened species, is its relation to chronic stress, which could potentially lead to immunosuppression and reduced reproductive activity. Our aim is to determine how different social environments and management systems might be influencing the secretion of fecal glucocorticoids in white rhinoceroses. We have analyzed the concentration of fecal glucocorticoid metabolites in 658 fecal samples from 14 white rhinoceroses, seven free-ranging rhinos, and seven rhinos from two different managed captive populations. HPLC techniques were used to determine the main glucocorticoid metabolite found in this species, and a competitive EIA was used to establish fecal 5α-pregnan-3 3β, 11β, 21-triol-20-oneglucocorticoid metabolite (fGCM) levels. Our results reveal that management systems and social interactions had an influence on fGCM levels, suggesting that the more restrictive the management and social conditions are, the higher the glucocorticoid concentrations that are found. Additionally, sex was also found to influence fGCM levels, as in females, fGCM concentrations were higher than in males. We conclude that the analysis of glucocorticoids in relation to other factors is a powerful tool to assess adrenocortical response in white rhinoceros in order to broaden the knowledge of their reproductive biology and improve the management of the species.

An Investigation of Ovarian and Adrenal Hormone Activity in Post-Ovulatory Cheetahs (Acinonyx jubatus)

Cheetahs have been the subject of reproductive study for over 35 years, yet steroid hormone activity remains poorly described after ovulation. Our objective was to examine and compare fecal progestagen (fPM), estrogen (fEM), and glucocorticoid (fGM) metabolite concentrations post-ovulation in pregnant and non-pregnant animals to better understand female physiology (1) during successful pregnancy, (2) surrounding frequent non-pregnant luteal phases, and (3) after artificial insemination (AI) to improve the low success rate. Secondarily, the authors also validated a urinary progestagen metabolite assay, allowing pregnancy detection with minimal sample collection. Fecal samples were collected from 12 females for ≥2 weeks prior to breeding/hormone injection (the PRE period) through 92 days post-breeding/injection. Samples were assessed for hormone concentrations using established enzyme immunoassays. Urine samples were collected for 13 weeks from 6 females after natural breeding or AI. There were no differences among groups in fGM, but in pregnant females, concentrations were higher (p < 0.01) in the last trimester than any other time. For pregnant females that gave birth to singletons, fGM was higher (p = 0.0205), but fEM tended to be lower (p = 0.0626) than those with multi-cub litters. Our results provide insight into the physiological events surrounding natural and artificially stimulated luteal activity in the cheetah.

The Animal-Human Interface in Farm Animal Production: Animal Fear, Stress, Reproduction and Welfare

Simple Summary

For at least the last four decades, the focus of animal welfare research, quality assurance, and policy initiatives has been on measuring behavioural and physiological stress responses in animals. In the last decade, however, this focus of animal welfare research has shifted to the consequences of these behavioural and physiological stress responses rather than only the responses per se. Modern-day farming, even with the intensification and automation requires regular monitoring and interactions by stockpeople. Research conducted in both experimental and commercial settings has shown widespread effects of the human-animal interactions on behaviour, physiology, and reproductive performance in farm animals. In this paper, we review the implications of human-animal interactions on reproduction in farm animals.

Abstract

A negative human-animal relationship (HAR) from the perspective of the animal is a limiting factor affecting farm animal welfare, as well as farm animal productivity. Research in farm animals has elucidated sequential relationships between stockperson attitudes, stockperson behaviour, farm animal fear behaviour, farm animal stress physiology, and farm animal productivity. In situations where stockperson attitudes to and interactions with farm animals are sub-optimal, through animal fear and stress, both animal welfare and productivity, including reproductive performance, can be compromised. There is a growing body of evidence that farm animals often seek and enjoy interacting with humans, but our understanding of the effects of a positive HAR on stress resilience and productivity in farm animals is limited. In this review, we explore the pathways by which stress induced by human-animal interactions can negatively affect farm animal reproduction, in particular, via inhibitory effects on the secretion of gonadotrophins. We also review the current knowledge of the stockperson characteristics and the nature of stockperson interactions that affect fear and physiological stress in farm animals. The contents of this review provide an insight into the importance of the HAR on farm animal welfare and reproduction while highlighting the gap in knowledge regarding the effects of a positive HAR on farm animals.

Steroid hormones in hair and fresh wounds reveal sex specific costs of reproductive engagement and reproductive success in wild house mice (Mus musculus domesticus)

Not only males but also females compete over reproduction. In a population of free-living house mice (Mus musculus domesticus), we analyzed how (metabolic) costs of aggressive interactions (reflected in fresh wounds and long-term corticosterone concentrations in hair) are predicted by individual reproductive physiology and reproductive success in males and females. Over eight years, we studied wounds and reproduction of more than 2800 adults under naturally varying environmental conditions and analyzed steroid hormones from more than 1000 hair samples. Hair corticosterone were higher and wounds more frequent in males than females. In males, wound occurrence increased with increasing breeding activity in the population, without affecting hair corticosterone levels. Unexpectedly, individual male reproductive success did not predict wounds, while hair corticosterone increased with increasing levels of hair testosterone and reproductive success. High corticosterone in hair of males might therefore reflect metabolic costs of fighting over reproduction. In females, hair corticosterone was generally lower than in males and high levels did not impede pregnancy. Reproductive investment (reflected in hair progesterone) was dissociated from reproductive success. Occasional wounds in females indicated individuals without recent reproductive success and revealed reproductive competition, presumably driven by instability in the social environment. In both sexes, corticosterone increased with age, but there was no evidence that received overt aggression, as indicated by wounds or elevated corticosterone, suppressed reproductive physiology. Our results diverge from laboratory findings and emphasize the need to also study animals in their natural environment in order to understand the complexity of their behavioral physiology.

Influence of exogenous corticosterone on testicular function and mating behavior of Nigerian indigenous cocks

In bridging the knowledge gap on stress physiology of Nigerian indigenous chickens, this study investigated the effect of exogenous corticosterone (eCORT) as stress inducing agent on the testicular function and mating behavior of Nigerian indigenous cocks. Twenty-four (24) cocks and one hundred and forty four (144) hens (mating ratio of 1 cock: 6 hens) were grouped into four and assigned to each of the four eCORT treatments (0, 2, 4 and 6 mgeCORT/KgBW) daily for 14 days. Semen samples were collected on days 0, 7 and 14 and analyzed for semen volume (SV), progressive sperm motility (PSM), membrane integrity (MI) and sperm abnormality (SA). Mating behaviors were monitored on days 3, 5 and 8. Blood samples, for hormonal (Luteinizing Hormone (LH), Follicle Stimulating Hormone (FSH) Testosterone (TEST) and stress analysis (heterophil/lymphocyte ratio, H/L) were collected from brachial vein on days 7 and 14. On day 15, cocks were euthanized and testes harvested for histomorphometry. Data were analyzed using multivariate analysis, one–way ANOVA and Kruskal-Wallis tests all in SPSS 23. Administration of 4 mgeCORT/KgBW declined (P<0.05) PSM while 4 mgeCORT/KgBW and 6 mgeCORT/KgBW cocks had reduced (P<0.05) SV and MI with increased SA. Compared to baseline values, progressive sperm motility of cocks administered 6 mgeCORT for 7 and 14 days decreased (P<0.05) by 57.5% and 52.4%, respectively. Exogenous CORT had no significant (P>0.05) influence on the mating behaviors, H/L ratio, FSH and TEST. However, 2 mgeCORT/KgBW enhanced LH levels. Administration of eCORT did not affect the testicular epithelial height and seminiferous tubular diameter. In conclusion, optimal stress induced by eCORT impaired semen quality but with less impact on reproductive hormones, H/L and mating behaviors of intensively raised Nigerian indigenous cocks.

Heterogeneity in GnRH and kisspeptin neurons and their significance in vertebrate reproductive biology

Vertebrate reproduction is essentially controlled by the hypothalamus-pituitary-gonadal (HPG) axis, which is a central dogma of reproductive biology. Two major hypothalamic neuroendocrine cell groups containing gonadotropin-releasing hormone (GnRH) and kisspeptin are crucial for control of the HPG axis in vertebrates. GnRH and kisspeptin neurons exhibit high levels of heterogeneity including their cellular morphology, biochemistry, neurophysiology and functions. However, the molecular foundation underlying heterogeneities in GnRH and kisspeptin neurons remains unknown. More importantly, the biological and physiological significance of their heterogeneity in reproductive biology is poorly understood. In this review, we first describe the recent advances in the neuroendocrine functions of kisspeptin-GnRH pathways. We then view the recent emerging progress in the heterogeneity of GnRH and kisspeptin neurons using morphological and single-cell transcriptomic analyses. Finally, we discuss our views on the significance of functional heterogeneity of reproductive endocrine cells and their potential relevance to reproductive health.

Aspects of Breeding Stallion Management with Specific Focus on Animal Welfare

Risk prevention is often counterproductive to stallions' living conditions when assessed under welfare aspects. In the wild, stallions live in social groups, but under domestic conditions, the majority of breeding stallions live in individual boxes with limited social contact. This stimulates aggressiveness and the incidence of stereotypic behavior. While racehorse stallions start their breeding career after having finished their performance career, riding horse stallions are often simultaneously used for breeding and performance. Training, performance, and the associated stress are unlikely to impair semen characteristics, but performing stallions may benefit from more opportunities for social contact. With regard to accommodation of stallions in single boxes, changes in the construction of the partition between them may help to improve social contact from merely visual to much more physical. This will help to reduce social isolation but requires careful observation if neighbors tend to either sympathize or fight with each other. Careful organization of the barn is thus of great importance. Under certain conditions, even keeping adult stallions in groups on spacious pastures is possible. Interestingly, the frequency of agonistic interactions usually decreases quickly and remains low after successful group integration. General changes in the husbandry of young stallions and at their transfer into the future career may help to produce stallions with better social skills and facilitate accommodation under improved welfare conditions.

Effects of Temperament on the Reproduction of Beef Cattle

Simple Summary

In beef cattle and other livestock species, temperament can be considered as their behavioral responses to human interaction. Temperament evaluation allows classifying cattle according to the level of responsiveness, from calm to excitable. Consistently across studies, beef females classified as more excitable have signs of increased stress response and are less fertile compared to cohorts with calmer temperament. Cattle temperament can be improved via genetic selection and acclimating young animals to human interaction and handling procedures.

Abstract

Temperament is often defined as the behavioral expression of animals in response to human interaction. Cattle temperament can be evaluated using an association of chute score and exit velocity, with cattle then classified as adequate or excitable temperament. To assess the impacts of temperament on various beef systems, these evaluation criteria were associated with productive and reproductive parameters of Bos taurus and B. indicus-influenced cattle. Consistently across studies, excitable cattle had greater plasma cortisol compared to animals with adequate temperament. Studies also reported that excitable beef females have poorer reproductive performance compared to calmer cohorts, including reduced annual pregnancy rates, decreased calving rate, weaning rate, and kg of calf weaned/cow exposed to breeding. Acclimating B. indicus × B. taurus or B. taurus heifers to human handling improved behavioral expression of temperament and hastened puberty attainment. However, similar benefits were not observed when mature cows were acclimated to human handling. Collectively, temperament of beef females measured via behavioral responses upon human handling impacts their reproductive and productive responses independent of breed type, and should be considered for optimal beef cattle production.

Pro-and anti-inflammatory effects of glucocorticoid Fluticasone on ovarian and immune functions in commercial-aged laying hens

Ovarian chronic inflammation has been created and extended in the laying hen mainly via increasing laying frequency and microbial infection, especially during the late stage of production period. This study was aimed to evaluate glucocorticoid (GC) Fluticasone as an anti-inflammatory agent on the gene expression of the ovarian pro-and anti-inflammatory mediators (follicular cyclooxygenases COX 1, 2, and cytokines), inflammatory responses of the immune system, ovarian functions (ovulation rate and follicular growths), and hormones in the commercial-aged laying hens. White Leghorn hens aged 92-weeks were used for four weeks to be supplemented by 2 ppm Fluticasone as an optimum dose obtained in a pre-trial base on ovulation rate. As compared to control, Fluticasone resulted in a significant decrease in the mRNA expression of COX-1 and pro-and anti-inflammatory cytokines, and increase in COX-2 mRNA expression and heterophil to lymphocyte ratio (P < 0.001). A significant reduction was observed in the ovulation rate, follicular size (P < 0.001), ovarian hormones, immunoglobulins, body weight, and food consummation (P ≤ 0.05) by administering GC Fluticasone. Although a relative anti-inflammatory improvement was created by Fluticasone in the ovarian condition, the administration of this glucocorticoid resulted in a considerable reduction in ovarian hormones and functions of commercial aged laying hens.

Measuring adrenal and reproductive hormones in hair from Southern Beaufort Sea polar bears (Ursus maritimus)

Polar bears (Ursus maritimus) use sea ice to access marine mammal prey. In Alaska's Southern Beaufort Sea, the declining availability of sea ice habitat in summer and fall has reduced opportunities for polar bears to routinely hunt on the ice for seals, their primary prey. This reduced access to prey may result in physiological stress with subsequent potential consequences to reproductive function (physiological changes that accompany reproduction), which can be measured via reproductive hormones. Hormone concentrations in hair can be used as a minimally invasive alternative to serum concentrations, which must come from animal captures. Hair samples also provide a long-term average measurement of hormone concentrations that is not influenced by short-term fluctuations like that of serum. The aim of this study was (1) to determine if a radioimmunoassay could be used to measure adrenal and reproductive hormones in polar bear hair, and (2) to determine what the relationship is between these hormones and other reproductive, condition, and demographic parameters of polar bears. We successfully validated this method for cortisol, progesterone, estradiol, and testosterone through the analysis of hair and serum of 141 free-ranging polar bears. We found that while hair cannot be used to estimate serum hormone concentrations during the breeding season, hormone concentrations in hair can be used to measure reproductive function in polar bears. Further, our findings support trends in previous studies measuring hormone concentrations in serum. We found that adrenal and some reproductive hormones were positively correlated in hair samples of females. Associations between hormone concentrations in hair and serum did not vary relative to reproductive status of adult females. Serum testosterone increased throughout the breeding season for adult males and was significantly associated with body mass index (BMI). Our research supports the use of hair as a measure of reproductive function in polar bears and allows us to monitor the future effects of climate change on polar bear physiology.

Physiological, oxidative and metabolic responses of lactating water buffaloes to tropical climate of South China

BACKGROUND

Heat stress in tropics is generally associated with significant economic losses resulting from reduced performance, morbidity, and mortality of livestock. To avoid serious consequences of heat stress, it is imperative to better understand the physiological responses and biochemical changes under the state of altered body homeostasis during different seasons of the year.

OBJECTIVES

This study aimed to evaluate the seasonal dynamics of physiological, oxidative and metabolic responses of lactating Nili-Ravi buffaloes to the tropical climate of South China.

METHODS

Physiological responses including rectal temperature (RT), body surface temperature (BST) and respiratory rate (RR) along with serum biochemical and antioxidant parameters of 20 lactating Nili-Ravi buffaloes were evaluated during different seasons of the year.

RESULTS

Higher temperature-humidity Index (THI) during the summer season (>80) resulted in a significant increases in RR and BST as compared to the winter season. Higher oxidative stress was observed in the summer season as revealed by significantly higher MDA while lower serum antioxidant enzyme (TAC, GSH-Px, SOD and CAT) contents. Moreover, serum cortisol was also significantly higher in summer and autumn. The levels of growth hormone and ACTH were also significantly (P < 0.05) lower in summer and autumn as compared to other seasons. The negative association of THI with physiological and antioxidant parameters was observed while it was positively associated with serum MDA and cortisol levels.

CONCLUSIONS

Our study revealed moderate heat stress in lactating buffaloes in the summer season which calls for attention to avoid economic losses and animal welfare issues.

Inter- and intra-specific variation in hair cortisol concentrations of Neotropical bats

Quantifying hair cortisol has become popular in wildlife ecology for its practical advantages for evaluating stress. Before hair cortisol levels can be reliably interpreted, however, it is key to first understand the intrinsic factors explaining intra- and inter-specific variation. Bats are an ecologically diverse group of mammals that allow studying such variation. Given that many bat species are threatened or have declining populations in parts of their range, minimally invasive tools for monitoring colony health and identifying cryptic stressors are needed to efficiently direct conservation efforts. Here we describe intra- and inter-specific sources of variation in hair cortisol levels in 18 Neotropical bat species from Belize and Mexico. We found that fecundity is an important ecological trait explaining inter-specific variation in bat hair cortisol. Other ecological variables such as colony size, roost durability and basal metabolic rate did not explain hair cortisol variation among species. At the individual level, females exhibited higher hair cortisol levels than males and the effect of body mass varied among species. Overall, our findings help validate and accurately apply hair cortisol as a monitoring tool in free-ranging bats.

Non-invasive monitoring of glucocorticoid metabolite concentrations in native Indian, as well as captive and re-wilded tigers in South Africa

Over the last century, wild tiger (Panthera tigris) numbers have declined from over 100 000 individuals to fewer than 4 000, with animals now confined to less than 5% of their historic range due to habitat loss, persecution, inadequate management, and poaching. In contrast, 15 000-20 000 tigers are estimated to be housed in captivity, experiencing conditions vastly different than their wild counterparts. A total of 280 tigers are currently held at 44 different facilities within South Africa, including zoos, semi-captive 're-wilded' populations, and pets; these animals provide a unique opportunity to measure the impact of extrinsic factors, found in exotic habitats, on the adrenocortical activity of tigers. By monitoring and comparing stress-related faecal glucocorticoid metabolite (fGCM) concentrations of tigers housed at different locations, and free ranging tigers in natural tiger reserves, this project aimed to get a better understanding of the impact of extrinsic factors on adrenocortical function as a measure of stress. The results of this study showed no significant difference in fGCM concentrations between captive, re-wilded, and free-ranging tigers with the exception of one site. Furthermore, factors such as sex and season were not significant drivers of fGCM concentrations. One study group had elevated fGCM concentrations, showing population variation in the stress response. This indicates that populations are able to cope with exotic environments, however, as population-specific differences in the stress response exist, we suggest management protocols be created for each population. This study offered the unique opportunity to see how well tigers are faring outside of their native range and if having re-wilded tigers in exotic locations is a potential welfare-acceptable management option for tiger conservation globally.

Landscape of stress: Tree mortality influences physiological stress and survival in a native mesocarnivore

Climate change and anthropogenic modifications to the landscape can have both positive and negative effects on an animal. Linking landscape change to physiological stress and fitness of an animal is a fundamental tenet to be examined in applied ecology. Cortisol is a glucocorticoid hormone that can be used to indicate an animal's physiological stress response. In the Sierra Nevada Mountains of California, fishers (Pekania pennanti) are a threatened mesocarnivore that have been subjected to rapid landscape changes due to anthropogenic modifications and tree mortality related to a 4-year drought. We measured cortisol concentrations in the hair of 64 fishers (41 females, 23 males) captured and radio-collared in the Sierra National Forest, California. We addressed two main questions: (1) Is the physiological stress response of fishers influenced by anthropogenic factors, habitat type, canopy cover, and tree mortality due to drought in their home range? (2) Does the physiological stress response influence survival, reproduction, or body condition? We examined these factors within a fisher home range at 3 scales (30, 60, 95% isopleths). Using model selection, we found that tree mortality was the principle driver influencing stress levels among individual fishers with female and male fishers having increasing cortisol levels in home ranges with increasing tree mortality. Most importantly, we also found a link between physiological stress and demography where female fishers with low cortisol levels had the highest annual survival rate (0.94), whereas females with medium and high cortisol had lower annual survival rates, 0.78 and 0.81, respectively. We found no significant relationships between cortisol levels and body condition, male survival, or litter size. We concluded that tree mortality related to a 4-year drought has created a "landscape of stress" for this small, isolated fisher population.

Direct evidence that KNDy neurons maintain gonadotropin pulses and folliculogenesis as the GnRH pulse generator

The gonadotropin-releasing hormone (GnRH) pulse is fundamental for mammalian reproduction: GnRH pulse regimens are needed as therapies for infertile women as continuous GnRH treatment paradoxically inhibits gonadotropin release. Circumstantial evidence suggests that the hypothalamic arcuate KNDy neurons expressing kisspeptin (encoded by Kiss1), neurokinin B (encoded by Tac3), and d ynorphin A serve as a GnRH pulse generator; however, no direct evidence is currently available. Here, we show that rescuing >20% KNDy neurons by transfecting Kiss1 inside arcuate Tac3 neurons, but not outside of these neurons, recovered folliculogenesis and luteinizing hormone (LH) pulses, an indicator of GnRH pulses, in female global Kiss1 knockout (KO) rats and that >90% conditional arcuate Kiss1 KO in newly generated Kiss1-floxed rats completely suppressed LH pulses. These results first provide direct evidence that KNDy neurons are the GnRH pulse generator, and at least 20% of KNDy neurons are sufficient to maintain folliculogenesis via generating GnRH/gonadotropin pulses.

Nerve Growth Factor, Stress and Diseases

Stress is a constant threat for homeostasis and is represented by different extrinsic and intrinsic stimuli (stressors, Hans Selye's "noxious agents"), such as aggressive behavior, fear, diseases, physical activity, drugs, surgical injury, and environmental and physiological changes. Our organisms respond to stress by activating the adaptive stress system to activate compensatory responses for restoring homeostasis. Nerve Growth Factor (NGF) was discovered as a signaling molecule involved in survival, protection, differentiation, and proliferation of sympathetic and peripheral sensory neurons. NGF mediates stress with an important role in translating environmental stimuli into physiological and pathological feedbacks since NGF levels undergo important variations after exposure to stressful events. Psychological stress, lifestyle stress, and oxidative stress are well known to increase the risk of mental disorders such as schizophrenia, major depressive disorders, bipolar disorder, alcohol use disorders and metabolic disorders such as metabolic syndrome. This review reports recent works describing the activity of NGF in mental and metabolic disorders related to stress.

Psychosocial stress and cortisol stress reactivity predict breast milk composition

We studied a sample of 146 Polish, exclusively breastfeeding mothers and their healthy born on time infants to explore the effect of perinatal psychosocial stress on breast milk composition. Maternal perinatal stress was assessed using Recent Life Changes Questionnaire summarizing stressful events from the previous six months. Stress reactivity was determined by administering the cold pressor test and measuring cortisol in saliva samples taken during the test. Breast milk sample was taken to measure energy, protein, fat, lactose, and fatty acid content. Analyses revealed that stress reactivity was positively associated with milk fat and long-chain unsaturated fatty acids and negatively associated with milk lactose. Perinatal psychosocial stress negatively affected energy density, fat as well as medium-chain and long-chain saturated fatty acids in milk. These results, together with previous studies, advocate monitoring maternal psychological status during the peripartum to promote breastfeeding and healthy infant nutrition.

Involvement of BMP-15 in glucocorticoid actions on ovarian steroidogenesis by rat granulosa cells

To elucidate the impact of glucocorticoids on ovarian steroidogenesis and its molecular mechanism by focusing on bone morphogenetic proteins (BMPs), we examined the effect of dexamethasone (Dex) on estradiol and progesterone synthesis by using primary culture of rat granulosa cells. It was revealed that Dex treatment dose-dependently decreased estradiol production but increased progesterone production induced by follicle-stimulating hormone (FSH) by granulosa cells. In accordance with the effects of Dex on estradiol synthesis, Dex suppressed P450arom mRNA expression and cAMP synthesis induced by FSH. Dex treatment in turn enhanced basal as well as FSH-induced levels of mRNAs encoding the enzymes for progesterone synthesis including P450scc and 3βHSD but not StAR and 20αHSD. Of note, Dex treatment significantly upregulated transcription of the BMP target gene Id-1 and Smad1/5/9 phosphorylation in the presence of BMP-15 among the key ovarian BMP ligands. It was also found that Dex treatment increased the expression level of BMP type-I receptor ALK-6 among the type-I and -II receptors for BMP-15. Inhibitory Smad6/7 expression was not affected by Dex treatment. On the other hand, BMP-15 treatment upregulated glucocorticoid receptor (GR) expression in granulosa cells. Collectively, it was revealed that glucocorticoids elicit differential effects on ovarian steroidogenesis, in which GR and BMP-15 actions are mutually enhanced in granulosa cells.