Topic:Cortisol
Cortisol is a steroid hormone produced by the adrenal glands in horses, playing a significant role in the regulation of metabolism, immune response, and stress management. As a glucocorticoid, cortisol influences various physiological processes, including glucose metabolism, inflammation modulation, and the maintenance of homeostasis during stress. Its levels in horses can vary due to factors such as exercise, environmental changes, and psychological stressors. Cortisol is often measured to assess stress responses and overall well-being in equine health management. This page compiles peer-reviewed research studies and scholarly articles that explore the production, regulation, and implications of cortisol in equine physiology and health.
The Role of Conceptus-maternal Signalling in the Acquisition of Uterine Receptivity to Implantation in Mammals. Implantation is a pivotal step in the establishment of mammalian pregnancy. Although implantation strategies vary between species, many aspects of conceptus-maternal signalling necessary to induce uterine receptivity to implantation are conserved. The temporal 'window' for the initiation of implantation is short and precisely controlled by endocrine, paracrine and autocrine factors. An invariable prerequisite for the development of uterine receptivity to implantation is continuous exposure of the endometrium to progesterone which, after a species-specific interval, downregulates progesterone r...
Acupuncture Affects Autonomic and Endocrine but Not Behavioural Responses Induced by Startle in Horses. Startle is a fast response elicited by sudden acoustic, tactile, or visual stimuli in a variety of animals and in humans. As the magnitude of startle response can be modulated by external and internal variables, it can be a useful tool to study reaction to stress. Our study evaluated whether acupuncture can change cardiac autonomic modulation (heart rate variability); and behavioural (reactivity) and endocrine (cortisol levels) parameters in response to startle. Brazilian Sport horses (n = 6) were subjected to a model of startle in which an umbrella was abruptly opened near the horse. Before s...
The physiological consequences of crib-biting in horses in response to an ACTH challenge test. Stereotypies are repetitive and relatively invariant patterns of behavior, which are observed in a wide range of species in captivity. Stereotypic behavior occurs when environmental demands produce a physiological response that, if sustained for an extended period, exceeds the natural physiological regulatory capacity of the organism, particularly in situations that include unpredictability and uncontrollability. One hypothesis is that stereotypic behavior functions to cope with stressful environments, but the existing evidence is contradictory. To address the coping hypothesis of stereotypies...
Responses of hematological parameters, beta-endorphin, cortisol, reactive oxygen metabolites, and biological antioxidant potential in horses participating in a traditional tournament. Several concerns have been raised over the health of animals used in equestrian games that have their origins in historical or religious events and are currently held in many countries. This study investigated physiological stress response and health status of horses participating in the Sartiglia, a historical horse tournament held in the city of Oristano, Italy, which is principally based on the attempts of masked horsemen at a gallop to run a sword through a hole in a suspended silver star. Blood samples were collected from 21 horses the day before the tournament (D0), during the tournament...
Flying-fox roost disturbance and Hendra virus spillover risk. Bats of the genus Pteropus (flying-foxes) are the natural host of Hendra virus (HeV) which periodically causes fatal disease in horses and humans in Australia. The increased urban presence of flying-foxes often provokes negative community sentiments because of reduced social amenity and concerns of HeV exposure risk, and has resulted in calls for the dispersal of urban flying-fox roosts. However, it has been hypothesised that disturbance of urban roosts may result in a stress-mediated increase in HeV infection in flying-foxes, and an increased spillover risk. We sought to examine the impact of...
Glucocorticoid receptor density and binding affinity in healthy horses and horses with systemic inflammatory response syndrome. Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis occurs in horses with systemic inflammatory response syndrome (SIRS). Peripheral resistance to glucocorticoids has not been investigated in horses. Objective: To determine if glucocorticoid receptor (GR) function in horses can be measured using flow cytometry, and to use this information to evaluate HPA axis dynamics. Methods: Eleven healthy adult horses in parts 1 and 2. Ten horses with SIRS and 10 age and sex matched controls in part 3. Methods: Flow cytometry was used to evaluate GR density and binding affinity (BA) in 3 healthy...
Domesticated horses differ in their behavioural and physiological responses to isolated and group housing. The predominant housing system used for domestic horses is individual stabling; however, housing that limits social interaction and requires the horse to live in semi-isolation has been reported to be a concern for equine welfare. The aim of the current study was to compare behavioural and physiological responses of domestic horses in different types of housing design that provided varying levels of social contact. Horses (n = 16) were divided equally into four groups and exposed to each of four housing treatments for a period of five days per treatment in a randomized block design. The four h...
Increased cortisol release and transport stress do not influence semen quality and testosterone release in pony stallions. The use of breeding stallions for equestrian competitions requires that fertility is not negatively affected by competition or transport to the competition site. In this study, effects of cortisol release induced by road transport (600 km), adrenocorticotropic hormone (ACTH) administration (3 × 0.5 mg synthetic ACTH) and placebo treatment on semen quality and testosterone release were investigated in Shetland stallions (N = 13) using a crossover design. Saliva for cortisol and blood for testosterone analysis were collected for 10 weeks after treatments. Semen was collected daily for 5 days di...
Pre-analytical stability of adrenocorticotrophic hormone from healthy horses in whole blood, plasma and frozen plasma samples. The stability of equine adrenocorticotrophic hormone (ACTH) in blood samples is not fully known. The study objectives were to determine ACTH stability (1) in whole blood and plasma over 72 h at either 4 or 21 °C, and (2) in plasma frozen at either -20 or -80 °C over 30 days. Nine horses were sampled and ACTH concentration were measured after storage as whole blood or plasma, at 4, 21, -20 and -80 °C for up to 30 days. The ACTH concentration was significantly reduced at 24 h but remained stable when plasma was frozen at -20 and -80 °C for 30 days. Beyond 24 h, samples stored a...
Effects of season, age, sex, and housing on salivary cortisol concentrations in horses. Analysis of salivary cortisol is increasingly used to assess stress responses in horses. Because spontaneous or experimentally induced increases in cortisol concentrations are often relatively small for stress studies, proper controls are needed. This requires an understanding of the factors affecting salivary cortisol over longer times. In this study, we have analyzed salivary cortisol concentration for 6 mo in horses (n = 94) differing in age, sex, reproductive state, and housing. Salivary cortisol followed a diurnal rhythm with the highest concentrations in the morning and a decrease throug...
Serum cortisol concentration in horses with heaves treated with fluticasone proprionate over a 1 year period. The purpose of this study is to measure the effect of long-term administration of inhaled fluticasone proprionate on cortisol concentrations in heaves-affected horses. Eleven horses with heaves were treated with fluticasone at least once daily at dosages required to improve lung function or with antigen avoidance alone for 1 year. Morning serum cortisol was measured before and after 10, 30, 110, 190, 230, 280, and 320 days of treatment. Cortisol was also measured in the afternoon of day 330. Cortisol was significantly lower in the Fluticasone group on days 30, 110, and 190 when compared with t...
Effects of a continuous rate infusion of butorphanol in isoflurane-anesthetized horses on cardiorespiratory parameters, recovery quality, gastrointestinal motility and serum cortisol concentrations. To assess the cardiorespiratory parametes, recovery, gastrointestinal motility and serum cortisol concentrations in horses anesthetized with isoflurane with or without a continuous rate infusion (CRI) of butorphanol for orchiectomy. Methods: Twelve adult, intact, male horses weighing 332 ± 55 kg were included in the study. Xilazine was administered as premedication. Anesthesia was induced with ketamine and midazolam and maintained with isoflurane. Butorphanol (0.025 mg kg-1 bolus) or an equivalent volume of saline (0.9%) was given intravenously followed by a CRI of butorphanol (BG) (13 µg kg...
Dexamethasone acutely regulates endocrine parameters in stallions and subsequently affects gene expression in testicular germ cells. Testicular steroidogenesis and spermatogenesis are negatively impacted by stress-related hormones such as glucocorticoids. The effects of two injections of a therapeutic dose of dexamethasone (a synthetic glucocorticoid, 0.1mg/kg; i.v.) given 24h apart to each of three stallions were investigated and compared to three saline-injected control stallions. Dexamethasone decreased circulating concentrations of cortisol by 50% at 24h after the initial injection. Serum testosterone decreased by a maximum of 94% from 4 to 20h after the initial injection of dexamethasone. Semen parameters of the dexame...
Changes in plasma leptin concentration during different types of exercises performed by horses. Leptin is a tissue-derivative adipokine that regulates appetite, food intake and energy expenditure. It is still not clear how exercise affects plasma leptin concentration in horses. The aim of this study was to evaluate the influence of exercise intensity and duration on plasma leptin levels in working horses. A total of 38 horses were prospectively included in the study and grouped according to the type of exercise they performed: dressage (six stallions, group D), jumping (12 stallions, group J), race (12 Thoroughbred horses, six stallions and six mares, group R) and harness (10 light draft...
The relationship of dominance, reproductive state and stress in female horses (Equus caballus). Maintaining a dominant position in a hierarchy requires energetically expensive aggressive displays and physical exertion. Lab based winner-loser studies, often conducted with individuals from non-social species, have shown that subordinates have higher stress hormone levels than dominant individuals. However, in wild studies on cooperative breeders, displays of aggression used to maintain dominance status are associated with elevated stress hormone levels. The effect of reproductive state on dominance and stress has not been addressed within either of these situations. The purpose of this stu...
Effect of different head and neck positions on behaviour, heart rate variability and cortisol levels in lunged Royal Dutch Sport horses. Different head-and-neck positions (HNPs) are discussed in relation to potential welfare issues. To evaluate the effect on welfare, seven Royal Dutch Sport horses were studied in five predetermined HNPs: (1) unrestrained (HNP1); (2) neck raised, bridge of nose around the vertical (HNP2); (3) neck lowered and considerably flexed, bridge of nose pointing towards the chest (HNP4); (4) neck raised and extended, bridge of nose in front of the vertical (HNP5), and (5) neck lowered and flexed, bridge of nose pointing towards the carpus (HNP7). A standardised exercise test (SET) of 34 min consisted o...
Neonatal glucocorticoid overexposure programs pituitary-adrenal function in ponies. The present study tested the hypothesis that overexposure to endogenous glucocorticoids in neonatal life alters the reactivity of the hypothalamic-pituitary-adrenal (HPA) axis in ponies at 1 and 2 yr of age. Newborn foals received saline (0.9% NaCl, n = 8, control) or long-acting adrenocorticotropic hormone (ACTH1-24) (Depot Synacthen 0.125 mg intramuscularly twice daily, n = 9) for 5 d after birth to raise cortisol concentrations 5- to 6-fold. At 1 and 2 yr of age, HPA axis function was assessed by bolus administration of short-acting ACTH1-24 (1 μg/kg intravenous) and insulin (0.5 U/kg...
Serum cortisol concentrations in horses with colic. Few studies have evaluated cortisol concentrations in horses with colic. In humans with septic shock, high cortisol levels are associated with an increased risk of death. The objectives of this study were to compare the serum total cortisol concentrations (STCCs) in horses with colic to those without colic, and to assess whether the STCC relates to the pathological nature or outcome of the disease. STCCs were determined at presentation in horses with colic and in systemically healthy 'control' horses. Horses with colic were grouped based on clinical and clinico-pathological parameters at admis...
[Stress parameters and behaviour of horses in walkers with and without the use of electricity]. In order to investigate stress responses of horses in walkers with and without electricity, 12 horses were trained during 3 weeks in a horse walker with and without the use of electricity (3.7 kV). To evaluate the stress response, cortisol levels in the blood were measured, the heart rate was monitored using the Polar® system and the behaviour was evaluated. Neither the cortisol levels nor the heart rates showed any relevant statistically significant difference between horses moved in the horse walker with or without the use of electricity. The highest cortisol levels and heart rates were rec...
Analgesic and gastrointestinal effects of epidural morphine in horses after laparoscopic cryptorchidectomy under general anesthesia. To evaluate the hypothesis that epidural morphine (0.1 mg kg(-1) ) decreases pain in horses after laparoscopic surgery without adversely affecting gastrointestinal (GI) motility. Methods: Randomized clinical trial. Methods: Eighteen horses undergoing laparoscopic cryptorchidectomy under general anesthesia. Methods: Horses were randomly assigned to receive either epidural morphine (0.1 mg kg(-1) ) or no epidural before the start of surgery. Pain behaviors were assessed during the first two post-operative days using a numerical rating scale. Barium-filled spheres were administered through a naso...
Effects of hyperflexion on acute stress responses in ridden dressage horses. The effects of hyperflexion on the welfare of dressage horses have been debated. This study aimed to investigate acute stress responses of dressage horses ridden in three different Head-and-Neck-positions (HNPs). Fifteen dressage horses were ridden by their usual rider in a standardised 10-min dressage programme in either the competition frame (CF), hyperflexion ("Low-Deep-and-Round"; LDR) or a looser frame (LF) in a balanced order on three separate test days. Heart rate (HR), heart rate variability parameters (HRV), behaviour and rein tension were recorded during the test. Salivary cortisol c...
Plasma cortisol concentration increases within 6 hours of stabling in RAO-affected horses. In many inflammatory diseases plasma cortisol concentration (CORT) increases at the onset of acute inflammation, but the situation in recurrent airway obstruction (RAO) of horses is unknown. Methods: Split-plot repeated measures design with one grouping factor (disease) and two repeated factors (day and 3-hour intervals). Objective: To test the hypothesis that CORT increases as acute exacerbations of RAO develop. Methods: Four RAO-susceptible and 4 control horses were placed in a low dust environment (LDEnv) for 2 days followed by 2 days in a high dust environment (HDEnv). Exacerbations of RAO...
Effect of different head-neck positions on physical and psychological stress parameters in the ridden horse. Different head-neck positions (HNPs) are used in equestrian sports and are regarded as desirable for training and competition by riders, judges and trainers. Even though some studies have been indicative of hyperflexion having negative effects on horses, this unnatural position is frequently used. In the present study, the influence of different HNPs on physical and psychological stress parameters in the ridden horse was investigated. Heart rate (HR), heart rate variability (HRV) and blood cortisol levels were measured in 18 horses. Low frequency (LF) and high frequency (HF) are power componen...
Detection of endogenous cortisol in equine tears and blood at rest and after simulated stress. To determine whether cortisol is present in equine tears at rest and during simulated stress and compare tear cortisol to serum free and total cortisol. Methods: Fourteen healthy adult horses were included. Paired tear total cortisol and serum total and free cortisol concentrations were measured with ELISA, chemiluminescent immunoassay, and ultrafiltration methodology, respectively, in 10 horses at rest once daily for five consecutive days. In an additional four horses, paired tear and serum samples were collected for cortisol measurement before and after adrenocorticotropic hormone (ACTH) sti...
Short-term effect of ovariectomy on measures of insulin sensitivity and response to dexamethasone administration in horses. To evaluate the effect of ovariectomy on insulin sensitivity in horses and determine whether the effects of suppression of the hypothalamo-pituitary-adrenal axis differ before and after ovariectomy. Methods: 6 healthy mares. Methods: The horses underwent an IV glucose tolerance test (IVGTT), an insulin sensitivity test, and a dexamethasone suppression test before and 5 weeks after ovariectomy. Body weight, serum cortisol and plasma ACTH concentrations, serum insulin-to-blood glucose concentration ratios, and changes in blood glucose concentration with time after injection of glucose or insulin...
Linking social environment and stress physiology in feral mares (Equus caballus): group transfers elevate fecal cortisol levels. Feral horses (Equus caballus) have a complex social structure, the stability of which is important to their overall health. Behavioral and demographic research has shown that decreases in group (or band) stability reduce female fitness, but the potential effects on the physiological stress response have not been demonstrated. To fully understand how band stability affects group-member fitness, we need to understand not only behavioral and demographic, but also physiological consequences of decreases to that stability. We studied group changes in feral mares (an activity that induces instabilit...
Changes in salivary and plasma cortisol levels in Purebred Arabian horses during race training session. Physical activity and stress both cause an increase in cortisol release ratio. The aim of this study was to evaluate the use of saliva samples for the determination of cortisol concentrations indicating the work-load level in horses during race training. Twelve Purebred Arabian horses aged 3-5 years were studied during the routine training session. After the warm-up, the horses galloped on the 800 m sand track at a speed of 12.8 m/s. Three saliva samples, and three blood samples were collected from each horse. Both types of samples were taken at rest, immediately after return from the trac...
The influence of selected factors and sport results of endurance horses on their saliva cortisol concentration. The aim of the study was to define the influence of the selected factors (gender, age, transportation time, riding distance and air temperature during the ride) on the cortisol secretion and finding a correlation between the hormone level and the horses' sport results (veterinary parameters and the ride route parameters). The research was performed on 38 Arabian pure breed horses taking part in the endurance rides. The cortisol level was measured with enzyme-immunological method in saliva samples, taken four times from each horse. In order to verify the differences between the mean results the...
Reduced-size microchips for identification of horses: response to implantation and readability during a six-month period. In this study, readability of reduced-size microchips in horses and the response to implantation were analysed. It was hypothesised that small microchips can be implanted stress-free but are less readable than larger microchips. Adult mares (n=40) were implanted with a reduced-size microchip (10.9×1.6 mm) at the left side of the neck (size of conventional microchips 11.4×2.2 mm). Microchips were identified with three different scanners (A, B, C) immediately, and at 6, 12 and 28 weeks after implantation. Twelve out of the 40 mares were submitted to microchip implantation and control treatment...
Physiological, behavioral, and serological responses of horses to shaded or unshaded pens in a hot, sunny environment. Housing recommendations for horses invariably include providing access to shade on hot, sunny days, but the potential benefits have not been scientifically studied. This experiment measured physiological, behavioral, and serological responses of horses confined individually to completely shaded (SH) or completely unshaded (SUN) drylot pens during the summer in Davis, CA. Twelve healthy adult horses in a crossover design experienced both treatments for 5 d each. Rectal temperature, respiration rate, skin temperature, and sweat scores were recorded hourly from 1230 to 1730 h daily. Observations ...