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Topic:Physiology
The physiology of horses encompasses the study of the biological functions and processes that occur within the equine body. This includes the examination of various systems such as the cardiovascular, respiratory, musculoskeletal, digestive, and nervous systems. Understanding equine physiology is essential for comprehending how horses adapt to different environmental conditions, perform physical activities, and respond to health challenges. Research in this field often focuses on the mechanisms of energy metabolism, thermoregulation, and muscle function during exercise, as well as the physiological responses to stress and disease. This page compiles peer-reviewed research studies and scholarly articles that explore the diverse aspects of equine physiology, providing insights into the biological processes that support the health and performance of horses.
[Variations in plasma components in lactating mares at late pregnancy-early lactation (author’s transl)]. In an experiment comparing pregnant then lactating mares with dry non-pregnant mares, the changes in plasma components were studied as indicators of the metabolic utilization of energy (glucose, non-esterified fatty acids, beta-hydroxybutyrate), nitrogen (urea, proteins) or minerals (calcium, phosphorus, magnesium). The mares were fed daily 2 kg concentrate and hay ad libitum. Beta-hydroxybutyrate, magnesium and to a lesser extent glucose were the only constituents whose levels were affected within the period starting one month before and ending one month after foaling. The increase in food in...
Copper metabolism and requirement in mature ponies. The effects of copper intake on stable copper and 64Cu metabolism and on the excretory pathways of absorbed copper were examined in ponies. Bile and feces collected from two bile duct-cannulated ponies following an intravenous dose of 64Cu showed that bile was the main route of endogenous copper excretion. Stable copper and 64Cu metabolism were examined in three intact ponies fed dietary copper to provide 5.6, 16.6 and 25.7 mg Cu/100 kg body weight/day. The amount of copper excreted in urine was not influenced by dietary treatment. Stable copper absorption and 64Cu retention significantly incr...
Fatty acid composition of equine plasma. Fatty acid composition of plasma lipids of normal horses was determined. Four fatty acids (C16:0, C18:0, C18:1, and C18:2) comprised 86.73% of the total, with C18:2 comprising 44.04% of the total. Eight other fatty acids were found in small amounts. Unsaturated fatty acids constituted 66% of the total. Marked variation was demonstrated in fatty acid occurrence and distribution in the sterol ester, triglyceride, phospholipid, and free fatty acid fractions.
Variations in the properties of equine chorionic gonadotropin. The objectives of this paper are to review the chemical and biological properties of equine chorionic gonadotropin (eCG, PMSG) isolated from the serum. Comparisons are made with eCG isolated from endometrial cups, trophoblast cell culture medium, and low titer serum. The results show that eCG can vary, depending on the source, in both chemical and biological (LH and FSH activity) properties.
Concentration of serum transferrin in sick horses and its relationship to serum albumin content. Studies of transferrin (Tf) concentration in sera of sick horses were carried out using Mancini’s immunodiffusion technique. Relative values against a chosen reference serum were determined for a total of 112 horses. Horses with acute infections had Tf values significantly below the normal. The lowest individual Tf value in this group (46%) was found in a six-months-old foal with temperature 41°C and watery diarrhoea. Horses suffering from acute laminitis also had decreased Tf values. The lowest value in the whole material (45%) was found in a horse belonging to this group. There was a posi...
Volume of the synovia in certain joint cavities in the horse. A method of determining the volumes of synovia in certain articular cavities in the horse is described. The method is based on the degree of dilution of human serum albumin labelled with I that is injected into the joint. It is shown that uniform distribution of the injected substance is attained within 20 min post injection. The elimination of the labelled substance was found to follow the pattern of a single exponential function. The following volumes of synovia were determined (mean ± s) : hock, 39.8 ± 2.1 ml; radio-carpal, 12.6 ±1.5 ml; intercarpal, 14.9 ± 0.6 ml; foreleg fetlock joint...
Antigen-antibody crossed electrophoretic studies and quantitative comparisons of serum transferrin types in horses. Selected transferrin phenotypes from 14 horses were investigated by antigen-antibody crossed electrophoresis. Horse sera were subjected to starch gel electrophoresis followed by right angle electrophoresis in agarose gels containing rabbit produced anti-horse transferrin. This technique gave an additional zone in the front as compared with 2 transferrin zones seen after ordinary starch gel electrophoresis. Comparisons of transferrin concentrations in horse sera were performed by an immunodiffusion technique. Values were related to a chosen reference serum. A total of 372 horses (210 Norwegian ...
A method of electro-acupuncture treatment for equine intestinal impaction. A method of electro-acupuncture for treatment of intestinal impaction of the horse was reported. The unique technique of the treatment includes deep needle insertion and the "triple tetanic treatment." Possible mechanism of this form of treatment was discussed.
Influence of dietary molybdenum on copper metabolism in ponies. The effects of molybdenum ingestion on copper metabolism were investigated in bile duct-cannulated ponies fed diets containing 1.01, 27.4 and 107.3 ppm molybdenum. Copper metabolism was assessed by examination of 64Cu and stable copper excretion in feces, bile and urine. The addition of molybdenum to the diet decreased copper absorption and retention as a consequence of increased excretion of dietary copper in feces and increased excretion of absorbed copper in bile. Only 5% or less of the absorbed copper was excreted in urine regardless of dietary treatment. Biliary molybdenum excretion was o...
In vivo metabolism of [3H]equilin in the pregnant mare. [3H]Equilin [3H-labeled 3-hydroxy-1,3,5(10), 7-estratetraen-17-one] was administered iv to a pregnant mare in the 10th month of gestation. Maternal urine was collected for 3 days, and blood samples were taken 35 min and 3, 6, 12, and 24 h after the injection. The half-life of the disappearance of radioactivity from the blood was approximately 2.5 h. Over 90% of the administered dose was excreted in the first 24 h. The urine was extracted, hydrolyzed, and fractionated. The bulk of the radioactive material (75%) was present in the phenolic sulfate fraction from which radiochemically pure equilin...
Characterization of the binding of Triton X-100 to equine and rabbit serum albumin. The binding isotherms for Triton X-100 binding to equine and rabbit serum albumin were determined by equilibrium dialysis at 16 degrees C in pH 7.0, I = 0.05 phosphate buffer. Presented in a Scatchard plot, the binding isotherms are a straight line, indicating thermodynamically independent and identical binding sites. In this model equine serum albumin is characterized as having 11 such sites with an equilibrium constant of 6.0 x 10(3) M-1. Similarly, rabbit serum albumin is characterized as having 9 such sites with an equilibrium constant of 8.0 x 10(3) M-1.
Regional pulmonary perfusion in horses: a comparison between anaesthetised and conscious standing animals. The regional perfusion to the lungs of 14 ponies was studied using radioactively labelled microspheres injected intravenously. It was found that within half an hour of induction of anaesthesia the perfusion to the dependent lung had decreased significantly from the values in the standing animal. When anaesthesia was maintained for more than two and a half hours, however, the lung perfusions were not significantly different from the standing values when the animals were lying in lateral or supine recumbency.
Use of the portable infrared thermometer as a means of measuring limb surface temperature in the horse. Evaluation was made of the portable infrared thermometer to measure limb surface temperature in 3 horses--first standing in a stall and then placed in lateral recumbency under general anesthesia. To determine the effect of pigment, black and white targets were examined with the instrument under various clinical conditions. In each horse, thermal gradient measurements were consistent along the extremities. Mean limb surface temperatures were less than rectal temperature and greater than ambient temperature. Limb surface temperatures measured in lateral recumbency under general anesthesia were u...
A physiological approach to fluid and electrolyte therapy in the horse. In this article a physiological approach to fluid therapy is discussed, commencing with examination of fluid distribution in the normal horse. The functions of individual plasma electrolyte concentrations are considered and practical causes of acid-base disturbances discussed. When fluid administration is necessary, selection of the route for fluid administration as well as the type of fluid are important considerations and these must be adjusted to the needs of the individual case. Balanced polyionic solutions appear to be most suitable for general use because normal saline can produce hypoka...
The metabolism of promazine and acetylpromazine in the horse. Promazine hydrochloride and acetylpromazine maleate were administered intravenously at clinical dose levels to horses. In urine from horses given promazine hydrochloride, the parent drug and four metabolites were detected. The two major metabolites, present as conjugates were identified after hydrolysis by beta-glucuronidase/arylsulfatase as 3-hydroxypromazine and 3-hydroxydesmonomethyl-promazine. Conjugated 3-hydroxypromazine has been previously identified as a major metabolite in the horse. Two minor metabolites isolated in this study were primaizine N-oxide and promazine N-oxide sulfoxide. ...
Influence of season and age on reproductive activity in pony mares on the basis of a slaughterhouse survey. Reproductive tracts were collected monthly over a 3-year period from 1,003 nonpregnant ponies at a slaughtering plant in Wisconsin. Ages of the animals were estimated from tooth replacement and wear. Ovaries were examined for follicular and luteal activity. There were no differences between left and right ovaries in size or occurrence of ovulation. The frequency of multiple ovulations, 10%, was higher than previously reported for ponies. The follicular changes during the ovulatory cycle did not support a two-wave theory of follicular growth. Ovarian activity changed seasonally, a finding simil...
[Some clinical biochemical features of ‘tying up’ in horses (author’s transl)]. The changes in the activities of lactate dehydrogenase (LDH) and creatine phosphokinase (CPK) in de blood of thirty-three horses with 'tying up' were compared. The extent to which the serum enzymes LDH, CPK and glutamic oxaloacetic transaminase (GOT) and the changes in the activities of these enzymes after suitable labour can be used in the diagnosis of 'tying up' and in following the recovery of patients was studied.
Fractionation and partial characterization of alpha-1-protease isoinhibitors of horse. The principal alpha-1-protease inhibitor of horse was fractionated by classical methods and analysed with a modified fibrinogen-agarose gel electrophoretic method of high sensitivity and resolving power. Starting with an electrophoretically homogeneous inhibitor in unfractionated serum, two isoinhibitor bands became apparent after fractionation with (NH4)2SO4 and DEAE-cellulose DE-52 ion-exchange chromatography. The isoinhibitors differed in electrophoretic migration and in the elution pattern from Sephadex G-100 gel filtration, but possessed identical antigenic determinants and enzyme specifi...
Lymphocyte responses to virus and mitogen in ponies during experimental infection with equine herpesvirus 1. Six pony foals, experimentally infected with equine herpesvirus 1 (EHV-1), were studied for their lymphocyte responses to EHV-1 and phytohemagglutinin (PHA) stimulations. Lymphocyte blastic transformation in the presence of EHV-1 appeared as early as 2 days after the foals were inoculated, reached a peak in 7 to 10 days, and subsequently decreased. In contrast, the lymphocyte blastic transformation in the presence of PHA increased sharply, reaching a peak in 2 to 3 days, and then decreased to its lowest level in 10 days after which it returned to its near preinoculation level. As for the mecha...
Recovery of peripheral chemoreceptor function after denervation in ponies. Resting ventilation (PaCO2) and ventilatory responses to acute hypoxia and to intravenous NaCN were assessed over a 4-yr period following cutting of the carotid sinus nerves and stripping the adventitia of the aortic arch. The data indicated essentially complete loss of peripheral chemoreceptor function immediately after surgery and hypoventilation during normoxia (delta PaCO2 = +8.7 Torr). There was a time-dependent, partial recovery of peripheral chemoreceptor function between 2 and 22 mo after surgery. Approximately 10% of the ventilatory response to iv NaCN returned, and 30-40% of the norm...
Dietary fat and exercise conditioning effect on metabolic parameters in the horse. Four isocaloric diets containing 4, 8, 12 and 16% dietary fat (as soybean oil) were fed to four horses at four intervals according to a Latin square design. After 3 weeks of conditioning at each interval, diet effects were evaluated by trotting all horses at 3.2 m/sec for 6 hours. Pre- and posttrotting responses were measured in muscle and liver glycogen, serum long-chain fatty acids, serum electrolytes, serum enzymes, serum cholesterol, plasma glucose, packed cell volume and hemoglobin. Dietary fat was highly correlated with exercise-induced plasma glucose changes and with cholesterol concent...
The effect of joint position on juxta-articular bone marrow pressure. Relation to intra-articular pressure and joint effusion–an experimental study on horses. Six metacarpo-phalangeal joints of adult horses were studied. Pressure measurements were made in the joint and the metacarpal bone with simultaneous measurement of the systemic arterial blood pressure. Investigations performed to study the effect of joint position on juxta-articular bone marrow pressure showed that an increase in joint flexion was always followed by a rise in intraosseous pressure with a significant increase at flexion above 60 degrees. Increase in intra-articular pressure which was achieved by injection of saline was always followed by a slower rise in intraosseous pressure. ...
Sexual behavior, seminal pH and accessory sex gland weights in geldings administered testosterone and(or) estradiol-17 beta. Sixteen stallions were castrated and 30 days later assigned to one of four treatments: (1) testosterone propionate (175 microgram/kg body weight), (2) 17 beta-estradiol-3-benzoate (44 micrograms/kg body weight), (3) a combination of both steroids or, (4) vehicle only. These dosage were administered every other day for 18 days. The dosages were then doubled and continued for 20 days. Concentrations of testosterone and estradiol in serum decreased rapidly after castration and stabilized within about 6 hours. Mean concentrations of testosterone and estradiol maintained by the steroids were 1.4 an...
Equine postanesthetic forelimb lameness: intracompartmental muscle pressure changes and biochemical patterns. Intracompartmental muscle pressures were recorded from the right and left forelimbs (extensor carpi radialis, triceps brachii) of healthy horses maintained in left lateral recumbency while under deep halothane anesthesia for 180 to 240 minutes. Cardiac output, blood pressure, blood gases, and acid-base status were monitored throughout the anesthesia, and electrolyte levels (Ca2+, P+, K+, Cl-, Na+) and enzyme activities (aspartate aminotransferase (AST), creatine phosphokinase (CPK), and blood lactate) were monitored for 7 days. Postanesthetic forelimb lameness was produced in 5 of the 6 horses...
