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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.
Free and bound cortisol in plasma and saliva during ACTH challenge in dairy cows and horses. Cortisol levels reflect hypothalamic-pituitary-adrenocortical (HPA) axis activity. While most plasma cortisol is supposed to be bound to the soluble corticosteroid-binding globulin (CBG), only free cortisol (FC) actively regulates metabolic and immunological processes. We aimed to establish a multispecies suitable method to assess FC in cows and horses which in combination with total cortisol (TC) allows interpreting proportional changes of cortisol in saliva as well as in blood in response to a standardized HPA axis activation via ACTH. We further investigated if the ratios of cortisol fracti...
Assessment of tissue-specific cortisol activity with regard to degeneration of the suspensory ligaments in horses with pituitary pars intermedia dysfunction. OBJECTIVE To identify signs of tissue-specific cortisol activity in samples of suspensory ligament (SL) and neck skin tissue from horses with and without pituitary pars intermedia dysfunction (PPID). SAMPLE Suspensory ligament and neck skin tissue samples obtained from 26 euthanized horses with and without PPID. PROCEDURES Tissue samples were collected from 12 horses with and 14 horses without PPID (controls). Two control horses had received treatment with dexamethasone; data from those horses were not used in statistical analyses. The other 12 control horses were classified as old horses (≥...
Road transport and diet affect metabolic response to exercise in horses. This study investigated the effects of transport and diet on metabolic response during a subsequent race-like test in Standardbred horses in training fed a forage-only diet and a 50:50 forage:oats diet. Six trained and raced Standardbred trotter mares were used. Two diets, 1 forage-only diet (FONLY) and 1 diet with 50% of DM intake from forage and 50% from oats (FOATS), were fed for two 29-d periods in a crossover design. At Day 21, the horses were subjected to transport for 100 km before and after they performed an exercise test (transport test [TT]). At Day 26, the horses performed a control...
Effect of temperament on cortisol response to a single exercise bout in Thoroughbred racehorses – short communication. Temperament has not been taken into account in previous studies evaluating the stress response to exercise in horses. The aim of the present study was to investigate the cortisol response in Thoroughbred racehorses to a single exercise bout, and to analyse the results based on the basic personality of the horse examined. Twenty healthy Thoroughbred horses were selected for the study based on a 25-item rating questionnaire survey used for characterising equine temperament. Eight temperamental and twelve calm horses took part in the experiment. The horses trotted as a warm-up activity, and then ...
Effect of butorphanol, midazolam or ketamine on romifidine based sedation in horses during standing cheek tooth removal. Standing surgery, especially dental procedures, are commonly performed in horses. This leads to an increasing demand for reliable sedation protocols. Therefore, it was the purpose of this study to investigate the influence of butorphanol, midazolam or ketamine on romifidine based sedation in horses during cheek tooth removal. Methods: Forty horses presented for tooth extraction were divided in four groups using matched pair randomization. Group R was sedated with romifidine (bolus 0.03 mg/kg, followed by a constant rate infusion (CRI) 0.05 mg/kg/h) and group RB with romifidine (same dose) an...
Effect of dietary carbohydrates and time of year on ACTH and cortisol concentrations in adult and aged horses. Diagnosis of equine pituitary pars intermedia dysfunction (PPID) remains a challenge as multiple factors (stress, exercise, and time of year) influence ACTH and cortisol concentrations. To assess endocrine status in a study designed to evaluate the effects of age and diet on glucose and insulin dynamics, we performed thyrotropin-releasing hormone (TRH) stimulation tests and overnight dexamethasone suppression tests in March, May, August, and October on 16 healthy Thoroughbred and Standardbred mares and geldings. Horses were grouped by age: adult (mean ± SD; 8.8 ± 2.9 yr; n = 8) and aged (20...
Glucocorticoid assessment in the domestic horse: The impacts of time and climatic variables on sample integrity. Assessment of faecal glucocorticoid metabolites (FGM) offers a noninvasive method of monitoring adrenal activity in domestic horses. Samples are collected on an opportunistic basis and, if they are not fresh or have been exposed to the elements before they are identified, may not accurately reflect FGM concentrations. Objective: To explore the impact of a range of environmental conditions upon the integrity of FGM levels in equine faeces. Methods: In vitro experiment. Methods: Equine faeces were exposed to six controlled environmental conditions intended to simulate a range of weather and seas...
Increased adrenocortical response to adrenocorticotropic hormone (ACTH) in sport horses with equine glandular gastric disease (EGGD). This study tested the hypothesis that adrenocortical function would be altered in horses with equine gastric ulcer syndrome (EGUS). Twenty-six sport horses competing at national or international levels in eventing (n=15) or endurance (n=11) were subjected to a gastroscopic examination and an adrenocorticotropic hormone (ACTH) stimulation test. Salivary cortisol concentrations were measured before (baseline) and after (30, 60, 90, 120 and 150min) IV ACTH injection (1μg/kg bodyweight). Within EGUS, two distinct diseases, equine squamous gastric disease (ESGD) and equine glandular gastric diseas...
Low plasma cortisol and fecal cortisol metabolite measures as indicators of compromised welfare in domestic horses (Equus caballus). The hypothalamic-pituitary-adrenal (HPA) axis response to chronic stress is far from straight forward, particularly with regards to animal welfare. There are reports of no effect as well as both decreases and increases in cortisol after chronic stressors. Therefore, the first aim of the present study was to determine how measures of compromised welfare, such as chronic pain and haematological anomalies, related to cortisol levels in domestic horses (Equus caballus). Domestic horses are an informative model to investigate the impact of chronic stress (due to environment, pain, work, housing con...
Effect of housing system on reproductive behaviour and on some endocrinological and seminal parameters of donkey stallions. Reproductive management of male donkeys employed for artificial breeding has been poorly studied. The aim of this study was to evaluate the effect of housing system, with the animals grouped together in a paddock or kept in individual boxes, on sexual behaviour, cortisol and testosterone concentration and seminal characteristics of adult male donkeys. The study included four Amiata donkey jacks (stallions) from which ejaculates, saliva and blood were collected during two distinct 3 weeks periods, one in the group and one in the box housing system. Time needed for semen collection was shorter ...
Bioavailability and tolerability of nebulised dexamethasone sodium phosphate in adult horses. Nebulisation of the injectable dexamethasone sodium phosphate (DSP) would offer an inexpensive way of delivering a potent corticosteroid directly to the lungs of horses with asthma. However, this approach would be advantageous only if systemic absorption is minimal and if the preservatives present in the formulation do not induce airway inflammation. Objective: To investigate the bioavailability of nebulised DSP and determine whether it induces airway inflammation or hypothalamic-pituitary-adrenal (HPA) axis suppression in healthy adult horses. Methods: Randomised crossover experiment. Methods...
The Effect of Geographic Location on Circannual Adrenocorticotropic Hormone Plasma Concentrations in Horses in Australia. Longitudinal evaluation of plasma endogenous ACTH concentration in clinically normal horses has not been investigated in the Southern Hemisphere. Objective: To longitudinally determine monthly upper reference limits for plasma ACTH in 2 disparate Australian geographic locations and to examine whether location affected the circannual rhythm of endogenous ACTH in the 2 groups of horses over a 12-month period. Methods: Clinically normal horses <20 years of age from 4 properties (institutional herd and client owned animals) in Perth (n = 40) and Townsville (n = 41) were included in the study. M...
An exploratory study of competition scores and salivary cortisol concentrations in Warmblood horses. The main objective of this explorative study was to describe the relationship between competition scores and salivary cortisol concentrations in young horses during dressage and showjumping competitions. The study also investigated whether the diurnal rhythm of salivary cortisol concentrations was affected by competition over consecutive days compared with the home environment. Saliva samples were collected from 126 dressage horses and showjumpers in their home environment and at 3 different events. The relationship between scores given by judges at the competition and cortisol concentrations ...
Steroids, steroid precursors, and neuroactive steroids in critically ill equine neonates. Hypothalamic-pituitary-adrenal axis (HPAA) dysfunction has been associated with sepsis and mortality in foals. Most studies have focused on cortisol, while other steroids have not been investigated. The objectives of this study were to characterise the adrenal steroid and steroid precursor response to disease and to determine their association with the HPAA response to illness, disease severity, and mortality in hospitalised foals. All foals (n=326) were classified by two scoring systems into three categories: based on the sepsis score (septic, sick non-septic [SNS] and healthy) and the foal s...
Effects of environmental temperature and season on hair coat characteristics, physiologic and reproductive parameters in Shetland pony stallions. We hypothesized that housing of stallions in a thermoneutral temperature zone during autumn and winter does not only influence metabolism and hair shedding but also improves the characteristics of raw and processed semen. Fertile Shetland pony stallions were followed from October to June. This time coincided with the seasons autumn, winter and spring. Ponies were kept in outside paddocks (group CON, n = 8) or in indoor stables (group ST, n = 8) from October to March when ST stallions returned to outdoor paddocks, but ponies remained in the same groups. The rectal temperature was measured o...
Influence of riders’ skill on plasma cortisol levels of horses walking on forest and field trekking courses. The aim of this study was to evaluate the influence of rider's skill on the plasma cortisol levels of trekking horses on two courses, walking on field and forest courses (about 4.5 to 5.1 km each). Three riders of different skills did horse trekking (HT) in a tandem line under a fixed order: advanced-leading, beginner-second and intermediate-last. A total of six horses were used and they experienced all positions in both courses; a total of 12 experiments were done. Blood samples were obtained before HT, immediately after and 2 h after HT. As a control, additional blood samples were obtained...
Estradiol cypionate aided treatment for experimentally induced ascending placentitis in mares. The overall goal of this study was to assess the efficacy of various therapeutic combinations of estradiol cypionate (ECP, a long-acting estrogen) and altrenogest (ALT, a long-acting progestin) in addition to basic treatment for placentitis with trimethoprim-sulfamethoxazole (TMS) and flunixin meglumine (FM). Specific outcomes measured in this experiment were (i) time from induction of bacterial placentitis to delivery, and foal parameters (high-risk, survival, and birth weight); and (ii) serum steroid concentrations (progesterone, 17α-hydroxyprogesterone, 17β-estradiol, and cortisol) in res...
Longitudinal changes in serum catecholamines, dopamine, serotonin, ACTH and cortisol in pregnant Spanish mares. Systemic physiological changes required for placental and fetal development during pregnancy are associated with an activation of the sympathetic nervous system (SNS) and the hypothalamus-pituitary-adrenal axis (HPA) in women, but this fact has not been investigated in mares. Venous blood samples were taken monthly from 31 successful Spanish mares during the 11months of pregnancy. During the first 4months of pregnancy, adrenaline (AD), dopamine (DOPA) and ACTH increases, whereas 5-hydroxitryptamine (5-HT) decreased, and noradrenaline (NAD) and cortisol (CORT) did not change. Serum NAD increase...
Effects of birth weight, sex and neonatal glucocorticoid overexposure on glucose-insulin dynamics in young adult horses. In several species, adult metabolic phenotype is influenced by the intrauterine environment, often in a sex-linked manner. In horses, there is also a window of susceptibility to programming immediately after birth but whether adult glucose-insulin dynamics are altered by neonatal conditions remains unknown. Thus, this study investigated the effects of birth weight, sex and neonatal glucocorticoid overexposure on glucose-insulin dynamics of young adult horses. For the first 5 days after birth, term foals were treated with saline as a control or ACTH to raise cortisol levels to those of stressed...
The effect of free and carrier-bound cortisol on equine neutrophil function. Cortisol is a key anti-inflammatory hormone that increases in bacterial sepsis and circulates predominantly bound to cortisol binding globulin (CBG). Only unbound cortisol was believed to be biologically active, but recent evidence suggests that CBG-bound cortisol also regulates inflammation. The objective of this study was to evaluate the effects of free and CBG-bound cortisol on equine neutrophil function ex vivo. We hypothesized that CBG would enhance cortisol-mediated suppression of neutrophil pro-inflammatory responses. Neutrophils isolated from 8 foals and 6 adult horses were exposed to ...
The relationship of muscle perfusion and metabolism with cardiovascular variables before and after detomidine injection during propofol-ketamine anaesthesia in horses. To study in horses (1) the relationship between cardiovascular variables and muscle perfusion during propofol-ketamine anaesthesia, (2) the physiological effects of a single intravenous (IV) detomidine injection, (3) the metabolic response of muscle to anaesthesia, and (4) the effects of propofol-ketamine infusion on respiratory function. Methods: Prospective experimental study. Methods: Seven standardbred trotters, 5-12 years old, 416-581 kg. Methods: Anaesthesia was induced with intravenous (IV) guaifenesin and propofol (2 mg kg) and maintained with a continuous IV infusion of propofol (0.15...
Hormonal, metabolic and physiological effects of laparoscopic surgery using a detomidine-buprenorphine combination in standing horses. To assess the hormonal, metabolic and physiological effects of laparascopic surgery performed under a sedative analgesic combination of detomidine and buprenorphine in standing horses. Methods: Prospective study. Methods: Eight healthy adult Dutch Warmblood horses and five healthy adult ponies undergoing laparoscopy were studied. Five healthy adult horses not undergoing laparoscopy were used as a control group. Methods: The sedative effect of an initial detomidine and buprenorphine injection was maintained using a continuous infusion of detomidine alone. The heart and respiratory rate, arteria...
Propofol anaesthesia for surgery in late gestation pony mares. To characterize propofol anaesthesia in pregnant ponies. Methods: Fourteen pony mares, at 256 ± 49 days gestation, undergoing abdominal surgery to implant fetal and maternal vascular catheters. Methods: Pre-anaesthetic medication with intravenous (IV) acepromazine (20 µg kg), butorphanol (20 µg kg) and detomidine (10 µg kg) was given 30 minutes before induction of anaesthesia with detomidine (10 µg kg) and ketamine (2 mg kg) IV Maternal arterial blood pressure was recorded (facial artery) throughout anaesthesia. Arterial blood gas values and plasma concentrations of glucose, lactate, cort...
Hormonal, metabolic and physiological effects of laparoscopic surgery using a detomidine-buprenorphine combination in standing horses. To assess the hormonal, metabolic and physiological effects of laparascopic surgery performed under a sedative analgesic combination of detomidine and buprenorphine in standing horses. Methods: Prospective study. Methods: Eight healthy adult Dutch Warmblood horses and five healthy adult ponies undergoing laparoscopy were studied. Five healthy adult horses not undergoing laparoscopy were used as a control group. Methods: The sedative effect of an initial detomidine and buprenorphine injection was maintained using a continuous infusion of detomidine alone. The heart and respiratory rate, arteria...
Intravenous anaesthesia using detomidine, ketamine and guaiphenesin for laparotomy in pregnant pony mares. Objective To characterize intravenous anaesthesia with detomidine, ketamine and guaiphenesin in pregnant ponies. Animals Twelve pony mares, at 260-320 days gestation undergoing abdominal surgery to implant fetal and maternal vascular catheters. Materials and methods Pre-anaesthetic medication with intravenous (IV) acepromazine (30 µg kg), butorphanol (20 µg kg) and detomidine (10 µg kg) preceded induction of anaesthesia with detomidine (10 µg kg) and ketamine (2 mg kg) IV Maternal arterial blood pressure was measured directly throughout anaesthesia and arterial blood samples were taken at ...
Measurement of cortisol concentration in the tears of horses and ponies with pituitary pars intermedia dysfunction. OBJECTIVE To compare tear cortisol concentrations between horses and ponies with pituitary pars intermedia dysfunction (PPID) and healthy nonaged (≤ 15 years old) and aged (≥ 20 years old) horses and to determine whether serum and tear cortisol concentrations were correlated. ANIMALS 11 horses and ponies with PPID and 20 healthy control horses and ponies (11 nonaged and 9 aged). PROCEDURES Paired tear and serum samples were obtained from PPID and control animals. All animals were free of active ocular disease. Tear and serum cortisol concentrations were measured with an ELISA and chemilumi...
Glucocorticoid metabolism in equine follicles and oocytes. The objective of this study was to determine whether (1) systemic and intrafollicular cortisol concentrations in horses are directly related and (2) supraphysiological levels of glucocorticoids affect in vitro maturation (IVM) rates of oocytes. Specifically, we studied the (1) changes in the intrafollicular cortisol and progesterone in context with granulosa cell gene expression during maturation of equine follicles (from 5-9 mm, 10-14 mm, 15-19 mm, 20-24 mm, and ≥25 mm in diameter) and (2) effects of cortisol supplementation on IVM rates and gene expression of equine cumulus-oocyte comple...
Pituitary-adrenocortical adjustments to transport stress in horses with previous different handling and transport conditions. The changes of the hypothalamic pituitary adrenal (HPA) axis response to a long distance transportation results in increase of adrenocorticotropic hormone (ACTH) and cortisol levels. The purpose of the study was to quantify the level of short-term road transport stress on circulating ACTH and cortisol concentrations, related to the effect of previous handling and transport experience of horses. Methods: The study was performed on 56 healthy horses after short-term road transport of 30 km. The horses were divided into four groups, Groups A, B, C, and D, with respect to the handling quality: Goo...
High interindividual and intraindividual variation of oxytocin secretion in estrous mares exposed to stallions, but no significant link to mate preferences. Oxytocin is a hormone that may not only influence reproductive mechanisms in mammals but also their social behavior, including pair bonding. We therefore tested if the concentrations of oxytocin and other hormones reveal mate preferences of 13 mares in estrus. Each mare was first exposed to two stallions (haphazardly selected out of seven) and her behavior recorded. The mare was then returned to her box (i.e., no contact to stallions during that time). Approximately 4.5 hours later, venous blood samples were collected every minute during 30 minutes preceding exposure to one of the two previo...
A comparison between the equine and bovine hypothalamus-pituitary-adrenocortical axis. In this review, we address the function of the hypothalamus-pituitary-adrenocortical (HPA) axis with special emphasis on the comparison between the bovine and equine species. The pars intermedia of the pituitary gland is particularly well developed in horses and cattle. However, its function is not well appreciated in cattle yet. The Wulzen's cone of the adenohypophysis is a special feature of ruminants. Total basal cortisol concentration is much higher in horses than that in cows with similar free cortisol fractions. Corticotropin-releasing factor (CRF) concentrations in equine pituitary veno...
