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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.
Reference values for clinical chemistry using the Coulter Chemistry System. Reference (normal) ranges were established for clinical chemistry results obtained from the Coulter Chemistry instrument on specimens from dogs, cats, horses, and cattle. These results, in general, are very similar to those reported in the current veterinary literature. The specimens obtained from horses and cows were subdivided according to age and lactation status, respectively. Significant differences were noted between the subgroups in the results of certain tests.
Effects of furosemide on plasma volume and extracellular fluid volume in horses. The effects of IV administered furosemide upon plasma volume (PV) and extracellular fluid volume were determined in horses at rest and after exercise. Serum sodium, potassium, chloride, and osmolality determinations were made. Furosemide caused a significant (P less than 0.05) decrease in PV and serum potassium concentrations in resting horses only. Furosemide's effects upon PV and electrolytes were evident longer than its hemodynamic effects.
Inhibition of calcium absorption in ponies fed diets containing oxalic acid. The effects of dietary oxalic acid on absorption, excretion, and retention of calcium was determined in Shetland ponies in 2 experiments. In each experiment, the results of feeding a control diet consisting of oats, molasses, and a complete pelleted horse ration were compared with those of feeding the control diet plus 1% oxalic acid. The diets contained 0.6% calcium in the 1st experiment and 0.45% calcium in the 2nd experiment. Oxalic acid increased the fecal excretion of calcium and decreased calcium absorption. The endogenous fecal excretion of calcium determined in the 1st experiment, usin...
Physiological implications of microbial digestion in the large intestine of mammals: relation to dietary factors. The rate of digesta marker passage through the large intestine of the dog, pig, and pony correlated with the relative length and degree of sacculation of the colon. Volatile fatty acids (VFA), the end products of microbial digestion of all forms of carbohydrate, were the major anions present in large intestinal contents of all three species. Total VFA concentration was little affected by the feeding of high-versus low-fiber diets. VFA were rapidly transported across colonic mucosa of all three species. Results of comparative studies indicate that production and absorption of VFA are important ...
Increased plasma bromide concentration in the horse after halothane anesthesia. A long-lasting increase of the plasma bromide concentration was found in 25 horses after clinical halothane anesthesia. The plasma bromide concentration was significantly (P less than 0.005) increased at the end of anesthesia. In 18 horses, peak values were reached between 48 and 72 hours after anesthesia. Eighteen days after horses had been anesthetized, the plasma bromide concentration remained significantly (P less than 0.005) increased. Significant correlation was not found between the total dose of halothane and the plasma bromide concentration. In 1 horse reanesthetized with halothane 4 ...
The mean fibre area of the semitendinosus, diaphragm and pectoralis transversus muscles in differing types of horse and dog. The mean fibre areas of samples from m. semitendinosus, m. diaphragma and m. pectoralis transversus of thoroughbred horses and greyhounds have been compared with those in similar samples from other members of their species. Athletes (greyhounds and thoroughbreds) have larger fibres in the semitendinosus and diaphragm than their fellows. However, the mean area of pectoralis transversus is similar in the two types of animal within each species. During growth the mean fibre areas increase to a greater extent in athletes than in non-athletes. Detraining adult greyhounds for a period of one year di...
Glucose transport by horse kidney brush borders. I.–Transport properties of brush border membrane closed vesicles. Brush border membranes isolated from horse kidney cortex as closed right-side out vesicles show selective permeability when analyzed on sucrose and dextran gradients. These vesicles can actively accumulate D-glucose. The preservation of the glucose transport system is demonstrated by the following features: (a) the uptake and release rates of D-glucose are higher in the presence of a sodium gradient, showing that D-glucose transport is a sodium-dependent process; (b) this transport, specific for the D-isomer, is inhibited by phlorizin; (c) the D-glucose transport system is saturable; (d) no in...
Serum folate levels in horses, with particular reference to the English thoroughbred. The assay of serum folate has been used to investigate the folate status of thoroughbreds in training to race, in-foal thoroughbred mares at stud and crossbred ponies kept permanently at grass. Throughbreds in training, with no obvious haematological or clinical abnormalities, had lower serum folate levels (mean 3.3, range 1.5 to 6.1 microgram per litre) compared with thoroughbred mares at stud (mean 10.6, range 6.4 to 15.8 microgram per litre) and crossbred ponies at grass (mean 10.9, range 7.4 to 16.6 microgram per litre. Intensive exercise, over a period of six months, significantly decreas...
Fourier transform infrared spectroscopic study of molecular interactions in hemoglobin. Infrared absorption spectra of the alpha-104 (G11) cysteine SH group have been observed for aqueous solutions of hemoglobin derivatives from humans, pigs, and horses. The center frequencies ((nu)SH) show ligand sensitive patterns that are similar for the three species, with (nu)SH (HbCO) <(nu)SH (HbO(2) ~ HbCN) < (nu)SH (Hb(+)) <<(nu)SH (deoxyHb) for human and pig hemoglobins. The alpha-104 SH group is most strongly H-bonded (smallest (nu)SH), has the greatest range of (nu)SH (Hb ? HbCO) in human hemoglobin, and is least strongly H-bonded and has the smallest range of (nu)SH (Hb ? HbCO) in hor...
Acid-base status of equine blood during storage. The changes in pH, pCO2, pO2, BE, SBC, and lactic during storage of equine venous and arterial blood in 24 hours at different temperatures were measured (tables I, II), and illustrated (fig, 1, 2, 3). Correction tables (tables VI, VII) for determination of the initial acid-base data are constructed based on regression equations (tables IV, V) of the in vitro changes of the blood. The changes in the acid-base values of equine blood differ from that of bovine and canine blood (table III).
Comparison of the effects of prostacyclin (PGI2), prostaglandin E1 and D2 on platelet aggregation in different species. The activity of prostacyclin (PGI2), PGE1 or PGD2 as inhibitors of platelet aggregation in plasma from human, dog, rabbit, rat, sheep and horse was investigated. Prostacyclin was the most potent inhibitor in all species. PGD2 was a weak inhibitor in dog, rabbit and rat plasma whereas PGE1 and prostacyclin were highly active. Theophylline or dipyridamole potentiated the inhibition of human platelet aggregation by prostacyclin, PGE1 or PGD2. Compound N-0164 abolished the inhibition by PGD2 of human platelet aggregation but did not inhibit the effects of PGE1 or prostacyclin. The results suggest ...
Electromagnetic blood flowmeters and flow probes: theoretic and practical considerations. Electromagnetic blood flowmeters and flow probes are used to measure blood flow in blood vessels throughout the circulatory system. The principle of this measuring device is based on laws of electromagnetic induction discovered in the 19th century. The instrument has been predominantly used in research, but is presently used in human cardiovascular units to measure blood flow in blood vessels, and in prosthesis in conjection with cardiovascular surgical procedures. Electromagnetic flow equipment provides the most accurate measurement (in vivo) of blood flow available, both for acute and chroni...
An experimental study on the role of the reciprocal tendinous apparatus of the horse at walk. The locomotor pattern of the hind limb of seven horses has been studied in intact animals and after transection of the following structures: the peroneus tertius tendon, the cranial tibial muscle, both cranial tibial muscle and peroneus tertius tendon, and the superficial digital flexor tendon. The investigation was carried out by high speed cinematography and electromyography. It is concluded that (1) the muscles and tendons over the cranial aspect of the tibia play an important role during the support phase; (2) the movements of the hind limb may be performed without the action of the crania...
Amino acid sequence of the beta-subunit of the follicle-stimulating hormone from equine pituitary glands. A tentative amino acid sequence of the beta-subunit of equine follicle-stimulating hormone (FSH) was derived from the sequences of tryptic, thermolytic as well as peptic, subtilisin, and chymotryptic peptides. Equine FSH-beta is analogous to human FSH-beta except six amino acid substitutions at positions 12, 16, 21, 62, 108, and 114. The amino acid sequence suggests that the hormone-specific beta-subunits of FSH are similar at the interspecies level, whereas the amino acid sequences of the hormone nonspecific alpha-subunits show variations.
Isolation and amino acid sequence of the alpha-subunit of follicle-stimulating hormone from equine pituitary glands. Six hundred milligrams of follicle-stimulating hormone (FSH), containing 110 NIH-FSH-S1 units/mg, was isolated from 9 kg of equine pituitary glands. The equine FSH was dissociated into alpha- and beta-subunits. A tentative amino acid sequence of the alpha-subunit was determined. The alpha-subunit contained 82 amino acids. The equine FSH-alpha is shorter by 10 to 14 amino acids at the NH2 terminus and has several substitutions at several positions as compared with human FSH-alpha and bovine thyroid-stimulating hormone-alpha. At the intraspecies level, the alpha-subunits of human FSH, human lute...
The presence of two (Na+ + K+)-ATPase inhibitors in equine muscle ATP: vanadate nad a dithioerythritol-dependent inhibitor. A potent inhibitor of (Na+ + K+)-ATPase activity was purified from Sigma equine muscle ATP by cation- and anion-exchange chromatography. The isolated inhibitor was identified by atomic absorption spectroscopy and proton resonance spectroscopy to be an inorganic vanadate. The isolated vanadate and a solution of V2O5 inhibit sarcolemma (Na+ + K+)-ATPase with an I50 of 1 micrometer in the presence of 1 mM ethyleneglycol-bis-(beta-aminoethylether)-N,N'-tetraacetic acid (EGTA), 145 mM NaCl, 6mM MgCl2, 15 mM KCl and 2 mM synthetic ATP. The potency of the isolated vanadate is increased by free Mg2+. ...
Congenital stationary night blindness: an animal model. Electroretinographic studies of myctalopic Appaloosa horses demonstrated photopic and scotopic abnormalities similar to those in humans with congenital stationary night blindness (CSNB) of the Schubert-Bornschein type. The phototopic abnormalities consisted of reduced b-wave amplitudes and slower than normal b-wave implict time. The dark-adapted ERG's consisted of a simple negative potential; the scotopic b-wave was nonrecordable. However, a normal c-wave was present in the dark-adapted response. Histologic studies demonstrated no structural abnormalities that could explain the functional defe...
Foetal and maternal plasma concentrations of 13, 14-dihydro-15-oxo-prostaglandin F in the mare during late pregnancy and at parturition. The concentrations of 13, 14-dihydro-15-oxo-prostaglandin F(PGFM), the stable metabolite of prostaglandin F, were measured in the plasma of catheterized mares and foetuses and non-catheterized thoroughbred mares and ponies during the last months of gestation. The plasma concentration of PGFM increased gradually towards term in all groups of animals. During the operation for insertion of catheters, maternal and foetal concentrations of PGFM were high, but the values fell to basal levels 24--48 h after the operation. It was found the preoperative starvation (24 h) led to a rise in the concentrat...
