Omneity® Pellets
All-In-One Vitamin & Mineral Pellet
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.
Sympatho-adrenal activity and the clinical sedative effect of detomidine in horses. Thirty-nine horses were given detomidine 10 micrograms/kg bodyweight (bwt) intravenously (iv) and six horses were given a corresponding volume of saline solution before minor procedures. Venous blood samples were collected for catecholamine and cortisol determination immediately before the detomidine or saline injection and 20 mins after it. The behaviour of the horse at the time of detomidine injection and the extent of sedation were evaluated. Plasma adrenaline, noradrenaline and the catecholamine metabolites, 3,4-dihydroxyphenylglycol (DHPG) and 3,4-dihydroxyphenylacetic acid (DOPAC), and c...
The effects of stress on gastric ulceration, T3, T4, reverse T3 and cortisol in neonatal foals. Sixteen neonatal foals stressed by disease underwent endoscopic examination of their stomachs and blood was assayed for triiodothyronine (T3), reverse T3 (rT3), thyroxine (T4) and cortisol, to determine the effects of severe physiological stress and the occurrence of gastric ulcers. compared with eight age-matched controls, six foals had abnormal cortisol, seven had abnormal T3 and 12 had abnormal T4. Eleven of 13 foals had rT3 outside the 95 per cent confidence interval for clinically normal foals of comparable ages. Gastric lesions were seen more frequently in stressed foals, and gastric gla...
Plasma concentrations of cortisol, prolactin, luteinizing hormone, and follicle-stimulating hormone in stallions after physical exercise and injection of secretagogue before and after sulpiride treatment in winter. Ten lighthorse stallions were used to determine 1) whether prolactin (PRL) and cortisol responses previously observed after acute exercise in summer would occur in winter when PRL secretion is normally low, 2) whether subsequent treatment with a dopamine receptor antagonist, sulpiride, for 14 d would increase PRL secretion and response to thyrotropin-releasing hormone (TRH) and exercise, and 3) whether secretion of LH, FSH, and cortisol would be affected by sulpiride treatment. On January 11, blood samples were drawn from all stallions before and after a 5-min period of strenuous running. On J...
[A horse with Cushing’s disease]. A thirteen-year-old Dutch warmblooded mare was referred to the Faculty of Veterinary Medicine because of a sinusitis. She was thin with a potbellied appearance. Her coat was dull with long wavy hair. Unilateral (left) purulent nasal discharge was evident. A cbc revealed leucopenia (3.9 G.L.-1) and plasma biochemical analysis revealed a plasma glucose concentration of 10.1 mmol.L-1. Thermostable alkaline phosphatase (at 65 degrees C during 2 minutes) could not be demonstrated. Basal plasma cortisol concentration was lowered (114 nmol.L-1) and basal plasma ACTH concentration was highly elevated ...
Effects of hemolysis and storage on quantification of hormones in blood samples from dogs, cattle, and horses. Veterinary diagnostic endocrinology laboratories frequently receive hemolyzed plasma, serum, or blood samples for hormone analyses. However, except for the previously reported harm done by hemolysis to canine insulin, effects of hemolysis on quantification of other clinically important hormones are unknown. Therefore, these studies were designed to evaluate effects of hemolysis on radioimmunoassay of thyroxine, 3,5,3'-triiodothyronine, progesterone, testosterone, estradiol, cortisol, and insulin in equine, bovine, and canine plasma. In the first experiment, hormones were measured in plasma obt...
Responses of cortisol and prolactin to sexual excitement and stress in stallions and geldings. Sexual stimulation induces rapid secretion of cortisol and prolactin (PRL) in stallions. Experiment 1 was designated to determine whether stallions associated location and(or) procedure with previous sexual stimulation in that location. After a control period on d 1, four stallions were exposed to an estrous mare for 5 min on d 2. On d 3, 4, 5, and 6, the same procedure was followed with no mare present. Concentrations of PRL and cortisol increased (P less than .05) after mare exposure on d 2 but did not vary (P greater than .05) on d 1, 3, 4, 5, or 6. In Exp. 2, six stallions were used to det...
Quantitative buffy coat analysis related to adrenocortical function in horses during a three-day event competition. This study was carried out to investigate stress induced in a cross-country by measuring plasma cortisol and to compare the changes in cortisol level with the leucocytic changes measured with the quantitative buffy coat (QBC) analysis, which is a new method applicable in field conditions for the evaluation of haematological parameters in horses. Seven healthy horses competing in a national three-day event were investigated. Venous blood was sampled under resting condition, 2 min and 180 min after the completion of the cross-country and analysed for haematological parameters, plasma cortisol, p...
Exercise induced hormonal and metabolic changes in Thoroughbred horses: effects of conditioning and acepromazine. Nine Thoroughbred horses were assessed to determine the normal response of insulin, glucose, cortisol, plasma potassium (K) and erythrocyte K through conditioning and to exercise over 400 and 1,000 m. In addition, adrenaline, noradrenaline, cortisol, plasma K, erythrocyte K and L-lactate concentrations were evaluated in response to maximal exercise with and without the administration of acepromazine. Conditioning caused no obvious trends in plasma K, erythrocyte K, insulin or glucose concentration. Serum cortisol increased (P less than 0.05) from the initial sample at Week 1 to Weeks 4 and 5 (...
Detomidine reduces the plasma catecholamine, but not cortisol concentrations in horses. Single doses of the alpha 2-adrenergic sedative-analgesic drug, detomidine (10 micrograms/kg, n = 7; 20 micrograms/kg, n = 9), were administered IV to adult horses. Plasma concentrations of adrenaline, noradrenaline, the catecholamine metabolites 3,4-dihydroxyphenylglycol (DHPG) and 3,4-dihydroxyphenylacetic acid (DOPAC), and cortisol were determined before the medication and 30 minutes after it. The plasma concentrations of noradrenaline and the catecholamine metabolites decreased significantly after administration of both 10 micrograms/kg and 20 micrograms/kg of detomidine. Plasma adrenaline...
The effect of acute exercise on the secretion of corticotropin-releasing factor, arginine vasopressin, and adrenocorticotropin as measured in pituitary venous blood from the horse. We have used the technique which we have developed for collecting pituitary venous blood from conscious, undisturbed horses to study the effect of acute vigorous exercise on the secretion of CRF, arginine vasopressin (AVP) and ACTH. Pituitary venous (pit) blood was collected every 1-5 min from nine trained racehorses at rest in the stable. The horses then trotted quietly for 10 min, after which they galloped as fast as possible for 4-6 min, before returning to the stable where sampling continued. In Exp 1 (n = 5) no blood samples were taken during exercise, whereas in Exp 2 (n = 4), pit blood ...
Triglyceride, insulin, and cortisol responses of ponies to fasting and dexamethasone administration. Ponies were evaluated for their response to feed withholding and exogenous administration of corticosteroids (dexamethasone 0.04 mg/kg intramuscular [IM]) in an attempt to reproduce the hyperlipemia syndrome. Because insulin resistance has been associated with hyperlipemia, all ponies were initially evaluated for insulin response to an oral glucose load and normal dexamethasone suppression of serum cortisol. Four ponies were identified as hyperinsulinemic reflecting insulin resistance. All ponies had suppressed cortisol concentrations following dexamethasone administration. Feed withdrawal res...
Progestagen, oestrone sulphate and cortisol concentrations in pregnant mares during medical and surgical disease. Plasma cortisol, oestrone sulphate and progestagens were measured in 22 stressed pregnant mares (gestation length 17-336 days) as indicators of fetal viability. Mares were bled every 12 h from time of admission, and plasma was stored at -70 degrees C until assayed. Four normal mares were bled twice weekly from Day 270 to parturition to provide baseline endocrine data. Cortisol and progestagen concentrations were measured by radioimmunoassay and oestrone sulphate was measured by enzyme immunoassay. Mares were grouped according to clinical diagnosis: surgical colic (Group 1, n = 11), medical col...
Influence of pregnancy on diurnal and seasonal changes in cortisol, T3 and T4 levels in the mare blood serum. 1. The diurnal changes in the level of total protein, cortisol, T3 and T4 were studied in four barren and four pregnant standard-bred mares, kept and examined under the same conditions. 2. Blood samples were taken every 4 hr. for one day each month, throughout one year. 3. In barren mares, a diurnal rhythm in cortisol level (acrophase at 0530 hr in summer and at 0830 hr in winter) and in T3 level (acrophase at 1330 hr in summer and at 1800 hr in winter) was found. 4. In pregnant mares, a diurnal rhythm in cortisol level only till 5th month of pregnancy was observed. 5. A diurnal rhythm in T3 l...
Relationship between circulating tri-iodothyronine and cortisol in the perinatal period in the foal. Pre- and post partum changes in plasma T3 have been examined in relation to plasma cortisol in 23 newborn foals (12 full term, 6 premature and 5 'twilight'), and in 5 fetuses catheterized in late gestation. Blood samples were collected daily from the fetuses and from the neonates at 30-min intervals for 2 h after birth; the plasma was assayed for T3 and cortisol by standard radioimmunoassay methods. In the full-term foals, plasma cortisol and T3 concentrations were high at birth (67.4 +/- 6.1 and 4.3 +/- 0.3 ng/ml respectively) and rose to a maximum during the following 2-h period to 141.0 +/-...
Effects of transport and racing on ionic changes in thoroughbred race horses. 1. Packed cell volume (PCV), blood glucose, total plasma proteins (TPP) and plasma electrolytes, osmolality, cortisol and aldosterone alterations produced by transport and racing, were investigated in race horses. 2. Plasma cortisol, sodium and blood glucose, found after transport, were higher, while aldosterone was lower than control levels. 3. After racing, PCV, blood glucose, TPP and plasma cortisol, sodium and osmolality were higher than control, while chloride diminished and aldosterone returned to control values. 4. These results demonstrate that transport and racing are different kinds ...
Effect of oral melatonin treatment on the seasonal physiology of pony stallions. This study tested the role of melatonin in the regulation of seasonal physiological change in the pony stallion. Four 3-year-old, Welsh Mountain pony stallions were housed initially under the prevailing short-day photoperiod in December (8 of light [L]:16 h of darkness [D]) before being transferred to long days (16L:8D) on 13 January for the remaining 22 weeks of the study. On Day 76 (11 weeks later) the stallions began an 11-week period of daily melatonin treatment (20 mg orally, 8 h after lights on). Marked changes in mean plasma testosterone, beta-endorphin and cortisol concentrations occur...
[Reference values for cortisol, T4 and T-uptake in different horse groups using the fluorescence polarization immunoassay (FPIA)]. Reference values for Cortisol, T4 and T-Uptake, determined with the Fluorescence-Polarization-Immunoassays (FPIAs) in blood-plasma of different horse groups were established. The highest Cortisol values were measured in blood samples from thoroughbred racehorses and riding horses taken between 7 and 8 a.m. (181 +/- 37 and 268 +/- 43 nmol/l), the lowest gained between 5 and 6 p.m. (69 +/- 45 and 85 +/- 32 nmol/l respectively). Peak values for T4 in riding horses were found in blood samples collected between 1 and 2 p.m. (28.2 +/- 5.7 nmol/l) followed by the samples taken at 5-6 p.m. and 7-8 a.m...
Selected laboratory parameters of thoroughbreds. Selected haematological, blood chemical and serological variables were investigated in healthy Thoroughbreds (n = 45) in training. Haemoglobin concentration, haematocrit, red, white and differential cell counts as well as serum concentrations of total and ionized calcium, sodium, potassium, chloride, urea, creatinine, total protein, albumin, inorganic phosphorus, total bilirubin, iron, glucose, magnesium, alkaline phosphatase, gamma-glutamyltransferase, lactate dehydrogenase, aspartate transaminase, alanine transaminase and creatine kinase were found to be within ranges previously reported for...
Characterisation of compounds isolated from the sera of horses with acute grass sickness. Isolates were prepared from the sera of 12 horses with acute grass sickness, using methods reported to yield serum fractions associated with neurotoxicity, and their components identified by liquid chromatography and spectroscopy. All isolates were found to contain cortisol and six isolates also contained a degradation product of an analgesic drug, dipyrone. However, no recognised neurotoxin was detected.
[The endocrine status of clinically conspicuous mares during the peripartum period]. The aim of the present investigations was to characterize the endocrine changes in the peripheral plasma during the periparturient phase of mares with a known history of obstetrical disorders. Blood plasma samples from 9 mares (8 mares during parturition, 1 mare during abortion) were collected and the following steroid hormones were radioimmunologically determined: progesterone (P4), dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEA-S), estrone (E1), estrone sulfate (E1-S), estradiol-17 beta (E2), estriol (E3), cortisol and transcortin. In general, with the exception of corti...
The stress response to anaesthesia in ponies: barbiturate anaesthesia. Information on the equine stress response to anaesthesia and surgery is sparse but offers a promising approach to elucidating the high anaesthetic risk in this species. Previous work has shown that halothane anaesthesia induces substantial metabolic and endocrine changes. This paper reports the effects of barbiturate anaesthesia. Anaesthesia was induced with thiopentone in six ponies and no further agents were given. They stood within 30 mins. On another occasion, these animals, and three further ponies, were anaesthetised with pentobarbitone and anaesthesia was maintained for 2 h. No surgery ...
Metabolic and hormonal changes associated with arthroscopic surgery in the horse. The effect of general anaesthesia and arthroscopic surgery on blood glucose and lactate, plasma non-esterified fatty acids, insulin, beta-endorphin and cortisol was investigated in seven horses. Animals were premedicated with xylazine and anaesthesia was induced with guaifenesin and sodium thiamylal and maintained with halothane vaporised in oxygen. Blood samples were collected in the pre-, intra- and post operative period. Induction of anaesthesia was associated with a transient hyperglycaemia and a significant rise in plasma insulin levels. Plasma insulin values fell during surgery but showe...
Comparison of the adrenocortical response to both pharmacological and physiological stresses in sport horses. Seven sport horses were investigated to compare physiological and pharmacological stresses on the plasma glucocorticosteroid levels. Venous blood was sampled and analysed for cortisol concentrations before and after each type of stress. The physiological stress was induced by the completion of a cross-country and the pharmacological one, by an intravenous ACTH administration (200 micrograms) in the same horses, one week after the course. Both exercise and ACTH injection induced a highly significant cortisol increase of 79 +/- 0.10% and 160 +/- 0.18%, respectively. The relative plasma cortisol ...
[Determination of cortisol, T4, T3 and T-uptake in serum and plasma of horses using fluorescence polarization immunoassays (FIPAs)]. The influence of duration and temperature of storage on hormone levels of whole blood, plasma and serum of horses was investigated. Using FPIAs cortisol, T4 and T-uptake could be measured while the T3-FPIA did not work appropriately. Serum and Plasma stored under the same conditions did not show any difference in cortisol, T4 and T-uptake values. In frozen heparinized plasma samples analysed on different days the cortisol and T4 concentrations fluctuated markedly. The T-uptake values were rather stable. The smallest day by day changes of cortisol and T4 in plasma were found when storing the sa...
Serum lipids and lipoproteins in equine colic and grass sickness. Serum total lipids, lipoprotein fractions, triglycerides, cholesterol, phospholipids and free fatty acids were measured in horses with acute, subacute and chronic grass sickness (equine dysautonomia) and in colic cases. The values were compared with those of normal grazing and stabled horses. A marked individual variation occurred, but total lipids, triglycerides and free fatty acids were significantly higher than normal in grass sickness and colic cases with cholesterol was significantly higher than normal in grass sickness cases only. Pre-beta lipoprotein was significantly increased in colic...
Effects of transportation on early embryonic death in mares. Incidence of early embryonic death (EED) and associated changes in serum cortisol, progesterone and plasma ascorbic acid (AA) in transported mares were investigated. Mares were transported for 472 km (9 h) during either d 16 to 22 (T-3 wk, n = 15) or d 32 to 38 (T-5 wk, n = 15) of gestation. Blood samples were drawn from control, nontransported mares (NT-3 wk, NT-5 wk, n = 24) and transported mares pre-trip, midtrip, and at 0, 12, 24, 48 and 72 h post-transport and daily for the next 2 wk. Incidence of EED between transported and nontransported mares was not different (P greater than .05). Ser...
Effect of transportation on the estrous cycle and concentrations of hormones in mares. Effect of transportation on estrous behavior, duration of the estrous cycle, ovulation, pregnancy rates and concentrations of serum cortisol, plasma ascorbic acid (AA), LH, estradiol and progesterone in mares was investigated. Fifteen mares were transported for 792 km (12 h) during the preovulatory stage of estrus. Transported mares were bled immediately before transport (baseline), at midtrip and 0, 12, 24, 48 and 72 h post-transport and twice daily from d 1 before transport to d 1 (estrogen) or 3 (LH) post-ovulation. Blood samples also were taken for progesterone on d 0, 2, 6, 10, 15, 16, 17...
Concentration decrease of corticosteroid binding globulin (CBG) in plasma of the mare throughout pregnancy. A significant decrease of CBG binding capacity in plasma of the mare throughout pregnancy was demonstrated using equilibrium dialysis and gel equilibration methods. As indicated with immunoelectrophoresis experiments, the pregnancy related fall of CBG binding capacity was linked to an actual decrease in blood CBG concentration. This result contrasts sharply with data on most other mammalian species, with the exception of the gestating rhesus monkey.
Action of dexamethasone in an equine model of acute non-immune inflammation. In a crossover study in seven New Forest ponies the actions of dexamethasone, at a dose rate of 0.06 mg kg-1 administered intravenously, were compared with those of a placebo treatment. Dexamethasone exerted expected effects on plasma and inflammatory exudate concentrations of cortisol and on blood glucose concentration and circulating leucocyte numbers, but it failed to affect exudate concentrations of the eicosanoids, prostaglandin E2, thromboxane B2, 6-keto-PGF1 alpha and leukotriene B4. These findings do not support the hypothesis that the anti-inflammatory actions of dexamethasone in the ...
Development of diurnal rhythm in some metabolic parameters in foals. 1. The development of diurnal rhythm activity of FDPA, AspAT and A1AT and in levels of cortisol, T3 and T4 was observed in the blood serum of six foals. 2. The studies began when a foal was 7 days old and were repeated every month until foals reached 1 year of age. Blood samples were taken every 4 hr for one day each month. 3. As a control group four barren mares were used, kept and examined in the same conditions. 4. In mature mares, diurnal rhythms in activity of A1AT (acrophase at 2200 hr), AspAt (2400 hr) and cortisol (0630 hr) but in T3 only in summer months (acrophase at 0100 hr) were ob...
