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.
Pulmonary function and adrenal gland suppression with incremental doses of aerosolized beclomethasone dipropionate in horses with recurrent airway obstruction. To evaluate clinical response, pulmonary function, and adrenal gland response to incremental doses of beclomethasone dipropionate in horses with recurrent airway obstruction. Methods: Crossover trial. Methods: 8 horses with recurrent airway obstruction. Methods: Horses randomly assigned to 4 groups were treated twice daily via aerosol administration of placebo or 500, 1,000, or 1,500 micrograms of beclomethasone dipropionate in a crossover design with a 10-day minimum washout period. Subjective assessment of airway obstruction, serum cortisol concentration, and maximum change in pleural pressu...
Plasma cortisol and ACTH concentrations in the warmblood horse in response to a standardized treadmill exercise test as physiological markers for evaluation of training status. Reliable physiological markers for performance evaluation in sport horses are missing. To determine the diagnostic value of plasma ACTH and cortisol measurements in the warmblood horse, 10 initially 3-yr-old geldings of the Hannovarian breed were either exposed to a training schedule or served as controls. During experimental Phase 1, horses were group-housed, and half of the horses were trained for 20 wk on a high-speed treadmill. During Phase 2, groups were switched and one group was trained for 10 wk as during Phase 1, whereas the control group was confined to boxes. During Phase 3 horses w...
Physiological responses of horses to 24 hours of transportation using a commercial van during summer conditions. Fifteen mature horses (mares, n = 6); geldings, n = 9) were used to assess the physiological responses of 24 h of transport in a commercial van under California summer conditions. The study was conducted on four consecutive days, and data were collected on d 1 and d 2 to obtain baseline values and to determine any diurnal variation in the individual measurements. Travel commenced on d 3 at 0800 for 24 h, with a total of 1,622 km traveled. Blood samples were collected at 0800, 1100, 1400, 2000, and 0200 each day. Horses were weighed and rectal temperatures recorded at 0800 each day and at 2000 ...
Hydrocortisone concentrations in post-race urine from horses. As hydrocortisone is an endogenous substance, it is first necessary to establish its normal concentrations so as to be able to control its use in racing animals. This study was designed to establish the hydrocortisone concentrations in post-race urine samples of horses racing in Brazil and also to evaluate the results in relation to the international threshold set for this drug. Urine samples were analysed by HPLC-UV. The results were evaluated according to the concentration range as well as sex and time of sample collection (afternoon or evening races). The results showed a high degree of var...
Induction and maintenance of gastric ulceration in horses in simulated race training. Gastric ulceration is a prevalent condition of racehorses. A number of models of gastric ulceration have been described, but none mimic the conditions of a horse in training. The objectives of this study were to determine whether gastric ulcers could be induced and maintained in a group of horses in simulated race training. In addition, serum cortisol was measured on a weekly basis to investigate the possibility that stress may be important in the pathogenesis of gastric ulceration. Thirty horses used in the trial were fed Bermuda grass hay and 6 kg of a concentrate diet, and exercised 6 days/...
Urinary concentration of corticoids in ponies with hyperlipoproteinaemia or hyperadrenocorticism. The urinary corticoid:creatinine (c:c) ratio was determined in ten pony mares suffering from hyperlipoproteinaemia. The mean (+/- sd) urinary c:c ratio of these ten ponies (47 +/- 31 x 10(-6)) was not significantly different from that of twelve pony mares with a pituitary pars intermedia adenoma (31 +/- 18 x 10(-6). The correlation between the urinary concentration of corticoids and plasma total lipids, and the correlation between the urinary c:c ratio and plasma total lipids in ponies with hyperlipoproteinaemia were not significant (P > 0.05; r = 0.53 and r = 0.008, respectively). Preliminary...
A comparison of grain, oil and beet pulp as energy sources for the exercised horse. High-grain diets for the exercising horse were compared with diets which provided 15% of the total caloric intake from either vegetable oil or a highly fermentable fibre source (beet pulp). Six Thoroughbreds age 3 years were fed one of 3 diets or 5 weeks in a replicated 3 x 3 Latin square. The CONTROL diet was 3.65 kg of sweet feed (SF), 0.9 kg of a protein/vitamin/mineral pellet and 5.45 kg of hay cubes. The FAT diet replaced 1.15 kg of SF with 0.45 kg of soybean oil and the FIBRE diet replaced 1.15 kg of SF with 1.36 kg of beet pulp. Horses were exercised 3 times per week on a high-speed tre...
Maximal exercise transiently disrupts hormonal secretory patterns in standardbred geldings. Basal concentrations of cortisol (CORT), beta-endorphin (beta EP), growth hormone (GH) and testosterone (T) and their disruption during 32 h of recovery after treadmill exercise were investigated in 4 geldings. Blood samples were collected from resting horses every 20 min between 0600-1000 and 1500-1900 h, and hourly between 1000-1500 h on 3 consecutive days. Treadmill exercise tests comprising 2 min intervals at 30, 50, and 70% VO2max then to fatigue at 100% VO2max were conducted between 1020-1130 h on Day 2. Blood was collected before, during and 15, 30, 60 and 90 min after exercise. Mean (C...
Effects of electrolyte and glycerol supplementation on recovery from endurance exercise. Incomplete recovery from endurance exercise after an overnight rest period is reflected by persisting weight loss and an elevated plasma aldosterone concentration, even in successful competitors. To determine whether supplementation with high doses of electrolytes, with or without glycerol, enhances recovery, the following were measured in 6 Arabian horses before and after completion of a 60 km treadmill exercise test simulating an endurance ride and after 12, 24, 48, and 72 h of recovery: bodyweight; plasma osmolality; plasma concentrations of protein, electrolytes, aldosterone and cortisol; ...
The effects of an endurance ride on metabolism and neutrophil function. The effects of an endurance ride on neutrophil functions in endurance-trained horses were evaluated and related to metabolic changes and changes in cortisol concentrations. Blood samples were taken from 7 horses (aged 9-15 years) one day before, and then 30-60 min, 1 day and 8 days after the ride. The race resulted in elevated serum cortisol levels (< 465 nmol/l) and an increased neutrophil:lymphocyte ratio. Immediately post race, the neutrophil ability to engulf yeast was increased. One day after the race, a decrease in leukotriene B4 production (approximately 40%) and in the respiratory b...
Plasma adrenocorticotropin, cortisol and catecholamines response to various exercises. The responses of plasma adrenocorticotropin (ACTH), cortisol, noradrenaline and adrenaline in 5 Thoroughbred horses to an incremental exercise and 2 relative workload exercises, at 105 and 80% maximal oxygen consumption (VO2max), on a treadmill were examined. These hormone concentrations increased (P < 0.05) with each exercise and the maximal plasma concentrations of ACTH, cortisol were observed between 5 and 30 min after the end of the exercise, while maximal catecholamine concentrations occurred just at exhaustion time. The plasma ACTH, noradrenaline and adrenaline responses during exerci...
Plasma cortisol and beta-endorphin concentrations in trained and over-trained standardbred racehorses. The effects of training and over-training on plasma cortisol and beta-endorphin (betaEP) concentrations at rest and after standardised exercise tests and the cortisol responses to adrenocorticotropin (ACTH) administration were investigated in standardbred horses. Twelve horses were divided randomly into control and over-trained (OT) groups after 17 weeks slow- and moderate-intensity treadmill training. The standardised treadmill exercise test consisted of 2 min at velocities corresponding to 30, 50, 70 and 100% of maximum O2 consumption. Over-training, defined as a significant decrease in body...
Measurement of glucocorticoid metabolite concentrations in faeces of domestic livestock. After 14C-labelled cortisol infusion in ponies and pigs, faecal samples were collected. Extraction of 0.5 g faeces with 5 ml 80-90% methanol yielded the highest radioactivity in the supernatant. Most of the metabolites were ether soluble. After high performance liquid chromatography (HPLC), the presence of immunoreactive metabolites was demonstrated by measuring each HPLC fraction using enzyme immunoassays for cortisol, corticosterone and 11-oxoaetiocholanolone. Only the assay for 11-oxoaetiocholanolone revealed peaks with co-eluting radioactivity. For biological validation of the test system,...
Effect of transport on the intensity of stress reactions in mares and foals. The aim of this study was to determine the effect of transportation on the behaviour and stress responses of the sympatho-adrenal and hypothalamo-pituitary-adrenal systems in mares and their foals by measuring the peripheral plasma concentrations of adrenaline, noradrenaline and cortisol. Control blood samples were taken from mares and their foals (n=5 pairs) on day 8 after parturition to establish whether blood sampling caused any changes in adrenaline, noradrenaline or cortisol concentrations in blood plasma. The experiment was conducted during foal oestrus (on day 9 after parturition). Adre...
Developmental changes in blood pressure and the renin-angiotensin system in pony fetuses during the second half of gestation. Blood pressure, heart rate and the plasma concentrations of cortisol and components of the renin-angiotensin system were measured in chronically catheterized Pony mares (n=15) and their fetuses during the second half of gestation (day 153-336 of gestation; term is normally between day 320 and day 340 of gestation). Fetal blood pressure increased towards term with the prepartum surge in plasma cortisol concentration, and there was a correlation between fetal blood pressure and both gestational age (r = 0.88, P < 0.0005) and plasma cortisol concentration (r = 0.88, P < 0.0005). Plasma concentrat...
Response of newborn foals with thyroid musculoskeletal disease to adrenocorticotrophic hormone (ACTH). Fetal maturation and equine parturition are not understood fully, although the adrenal and thyroid glands are thought to have regulatory roles. Thyroidectomized equine fetuses undergo prolonged gestation, and spontaneous diseases such as thyroid musculoskeletal disease and gestational fescue endophyte exposure are also associated with delayed parturition. Thyroid musculoskeletal disease is characterized by: histologically hyperplastic thyroid glands, chondro-osseous dysplasia and dysgenesis, angular limb deformity, low resting thyroxine and triiodothyronine concentrations, and lack of response...
Effects of glucose infusion on the endocrine, metabolic and cardiorespiratory responses to halothane anaesthesia of ponies. Glucose was infused intravenously into six ponies during halothane anaesthesia, to evaluate its effect on their endocrine response to anaesthesia. The ponies were premedicated with acepromazine, and anaesthesia was induced with thiopentone and maintained with halothane in oxygen for two hours. Glucose was infused to maintain the plasma glucose concentration above 20 mmol/litre. Anaesthesia was associated with hypothermia, a decrease in haematocrit, hypotension, hyperoxaemia, respiratory acidosis and an increase in the plasma concentrations of lactate and arginine vasopressin. The concentration...
New approaches to detect cortisol administration in the horse. The cortisol threshold concentration of 1.0 microg/ml in horse urine adopted by the International Federation of the racing Authorities in 1994 is specific. However, an increase in the sensitivity for the detection of cortisol administration would be helpful. Previous studies have shown that 20beta-dihydrocortisol concentration in urine would be a good indicator of cortisol administration. The purpose of the present work was to estimate the population parameters and the critical values of 20beta-dihydrocortisol and 20beta-dihydrocortisone concentration in urine compared with that of cortisol. U...
Hydrocortisone levels in the urine and blood of horses treated with ACTH. An investigation was undertaken to demonstrate whether therapeutic treatment with ACTH raises hydrocortisone (cortisol) levels in horse urine above the limit (1000 ng/ml) established by the International Conference of Racing Authorities with the aim of controlling the abuse of cortisol and ACTH in equine sports. ACTH (200 iu) was administered i.m. to 3 Thoroughbred horses; urine and blood samples were collected at intervals afterwards and analysed by an immunoenzymatic system (ELISA) and HPLC-MS. To ascertain post exercise cortisol levels in untreated horses, 101 urine and 103 serum samples we...
Different approaches to the identification of a cortisol isomer compound in horse urine. A threshold concentration for cortisol in equine urine was fixed at 1.0 microgram ml-1 by the racing authorities in 1994. In some circumstances, interlaboratory discrepancies were observed and structural cortisol modification was revealed. In order to elucidate the degradation process and to prevent it, an identification study of the produced compound was carried out. The modified substrate was characterised by the same molecular weight as cortisol and a shorter retention time under the conditions used for the cortisol quantification (M.A. Popot, PhD Thesis, King's College, London, 1996). To i...
The effects of intrafetal ACTH administration on the outcome of pregnancy in the mare. Enhanced adrenocortical activity in the fetus is related to the onset of parturition in many species. The aim of this study was to determine the effect of injection of fetal ACTH on gestational length and fetal viability in the horse. Pony mares (n=23) were studied from 300 days gestation. Seven control mares (Group 1) received three consecutive intrafetal injections of sterile water, while fetuses of a further 16 mares received Depot ACTH1-24. These mares were either allowed to foal spontaneously (Group 2, n=4) or delivery was induced within 3 days of the last fetal injection (Group 3, n=7); ...
Effect of exercise on the immune response of young and old horses. To compare exercise-induced immune modulation in young and older horses. Methods: 6 young and 6 aged horses that were vaccinated against equine influenza virus. Methods: Venous blood samples were collected for immunologic assessment before and immediately after exercise at targeted heart rates and after exercise for determination of plasma lactate and cortisol concentrations. Mononuclear cells were assayed for lymphoproliferative responses and incubated with interleukin-2 (IL-2) to induce lymphokine-activated killer (LAK) cells. Antibodies to equine influenza virus were measured. Results: Olde...
Perioperative plasma cortisol concentration in the horse. The cortisol response to anaesthesia and surgery was studied in 2 groups of horses undergoing either abdominal or non-abdominal surgery. The preoperative mean plasma cortisol concentration (pcc) of 381.7 nmol/l (s.d. 254.7) was markedly higher in the abdominal group than the early-morning mean pcc of 115.6 nmol/l (s.d. 78.4) in the non-abdominal group. During halothane anaesthesia and surgery the mean pcc increased significantly (p < 0.05) from the preoperative mean of 119.2 to 215.9 nmol/l (s.d. 79.8) after 30 min of surgery in the non-abdominal group. In the abdominal group a decrease occ...
Effects of hypoxia on endocrine and metabolic responses to anaesthesia in ponies. Some metabolic and endocrine effects of hypoxaemia were studied during halothane anaesthesia in six ponies. Each was anaesthetised twice; on one occasion a 20-minute period of hypoxaemia (arterial oxygen tension between 4.4 and 5.8 [mean 5.3] kPa) was imposed during 120 minutes of anaesthesia. On the second occasion arterial oxygen tension was maintained above 17 kPa throughout. Routine cardiovascular monitoring was performed and blood samples were taken to measure haematocrit, cortisol, insulin, glucose and lactate. Anaesthesia was associated with hypotension in both groups (mean ABP 7.0 kPa...
Diurnal variation and age differences in the biochemical markers of bone turnover in horses. Biochemical markers of bone turnover provide sensitive, rapid, and noninvasive monitoring of bone resorption and formation. Serum concentrations of osteocalcin (OC) reflect rates of bone formation, and urinary concentrations of the pyridinium crosslinks pyridinoline (Pyd) and deoxypyridinoline (Dpd) are specific and sensitive markers of bone resorption. These markers are age-dependent and are used to detect and monitor changes in the rates of bone turnover in a variety of orthopedic diseases in humans and may prove to have similar application in horses. This study examined age differences and ...
Endocrine and metabolic responses to plasma volume expansion during halothane anesthesia in ponies. The study was designed to contribute to identification of the stimulus to adrenocortical activity during halothane anaesthesia in equidae. Two groups of six ponies were premedicated with acepromazine before induction of anaesthesia with thiopentone and maintenance for 120 min with halothane in oxygen. In group H Haemaccel modified gelatine plasma replacer was infused (48+/-13 mL/kg) to maintain mean arterial blood pressure (MABP) close to preanaesthetic values. In group DH, blood pressure was maintained close to preanaesthetic levels with a lower dose of Haemaccel (10 mL/kg) combined with an i...
Pituitary-adrenocortical effects of methoxamine infusion on halothane anaesthetised ponies. This study investigated whether maintenance of normotension using a methoxamine infusion would prevent activation of the stress response during halothane anaesthesia in ponies. After acepromazine premedication, anaesthesia was induced with thiopentone in six ponies, and maintained for 120 minutes with halothane in oxygen and ventilation to normocapnia. Methoxamine (M, 0.013+/-0.005 mg kg(-1) min(-1)) or saline (C) was infused throughout anaesthesia. Sequential blood samples were taken for cortisol and ACTH assay. During anaesthesia normotension (mean arterial blood pressure 101-124 mm Hg) was ...
Physiological and behavioral consequences associated with short-term prevention of crib-biting in horses. Crib-biting in the horse is frequently prevented in the short-term by horse-owners using physical means. Because it has been proposed that crib-biting may function to reduce stress, the effect of prevention of crib-biting and/or eating on the behaviour, heart rate, and plasma cortisol and beta-endorphin concentrations was measured in six crib-biting and six normal horses. When crib-biters were unable to crib-bite, they showed an increase in ingestive behaviour. When crib-biters were prevented from crib-biting and eating, a relative stasis in the motility of the foregut occurred, suggesting tha...