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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.
Estimation of cardiac output in the horse by thermodilution techniques. An evaluation and comparison of thermodilution technique with dye dilution technique was made in the computation of cardiac output in 39 conscious adult horses (av body wt, 450 kg). Estimation of cardiac output by thermodilution was found to compare favorably with values obtained from dye dilution when a volume of 30 to 40 ml at a temperature of 0 C was used. Difficulties in obtaining accurate thermodilution curves in the horse seem predominantly associated with errors in mixing and observation.
Autoxidation in milk rich in linoleic acid. II. Modification of the initiation system and control of oxidation. Factors contributing to the initiation of lipid oxidation in cow's and mare's milk containing high levels of polyunsaturated fatty acids were studied. Addition of H2O2 just after milking, in slight excess of the stoichiometric amounts required to destroy ascorbic acid, delayed the development of oxidized flavours in cow's milk high in linoleic acid. Hydrogen peroxide treatment followed by the addition of alpha-or gamma-tocopherols prevented lipid oxidation in cow's milk even when 0.1 mg Cu/l milk was added. When used separately in the presence of Cu these treatments were ineffective as was but...
The influence of hepatic microsomal amidopyrine demethylase activity on halothane hepatotoxicity in the horse. The hepatotoxic effect of oral halothane in the horse is increased by pretreatment with phenobarbitone or DDT but not by chlorpromazine. Phenobarbitone and DDT increase the activity of hepatic amidopyrine N-demethylase but chlorpromazine does not. Carbon disulphide protects the liver of the horse against halothane.
Observations on growth plates in limbs of foals. Observations were made which may be related to growth plate disorders. They included irregularity and thickening of the growth plate bridging of the plate by bony spicules, distortion of the plate adjacent to foci of fusion, and metaphyseal lipping. These observations are very similar to those found in "epiphysitis." The question had to be asked, where these normal foals or did they have sub-clinical "epiphysitis"?
Steady-state enzyme kinetics of the pancreatic ribonucleases from five mannalian species. The kinetic parameters Km, k+2 and k+2/Km of the pancreatic ribonucleases (EC 3.1.4.22) from cow, giraffe, horse, rat and lesser rorqual have been determined, using 2',3'-cyclic cytidine monophosphate and 2',3'-cuclic uridine monophosphate as substrates. No large differences were found between the activities of the five enzymes. The relative differences between the activities of the five enzymes are mainly due to differences in the rates of hydrolysis and not to differences in the affinities for the substrates.
Levels of luteinizing hormone and progesterone during the estrous cycle and early pregnancy in mares. Jugular venous blood was collected from 16 mares at daily intervals throughout the estrous cycle. Twelve of these mares were bred to fertile stallions. Of the twelve, four were palpated daily throughout the estrous cycle, four were palpated daily during estrus and four were not palpated. The remaining four mares were not palpated or bred and blood samples were collected at 6-h intervals during estrus. Serum was harvested from all blood samples by centrifugation. The serum samples were analyzed for luteinizing hormone (LH) and/or progesterone by radioimmunoassay. Levels of LH in serum increased...
Studies on the estrus cycle of Arabian mares in Egypt. A study of the estrus cycle of Arabian mares in Egypt gave the following results:
1. The estrus cycle was as short as 12 and as long as 240 days.
2. Cycles considered as normal ranged between 16 and 34 days and were more concentrated in the period 20–26 days.
3. Periods of anestrum caused elongation of the cycles to varying lengths, from double the normal cycle period to four times or more.
4. Seasonal variations in the length of the estrus cycle are discussed.
Luteolysis following carotid or ovarian arterial injection of prostaglandin F2alpha in mares. On the day of ovulation (Day 0), 20 pony mares were randomly assigned to one of five groups (4 mares/group) which were given intracarotid arterial (ICA) and intraovarian arterial (IOA) injections on Day 7 as follows: 1) vehicle ICA, vehicle IOA (control); 2) .125 mg PGF2α ICA, vehicle IOA; 3) vehicle ICA, .125 mg PGF2α IOA; 4) .250 mg PGF2α ICA, vehicle IOA; or 5) vehicle ICA, .250 mg PGF2α IOA. Peripheral plasma progesterone and LH concentrations were determined for 0 (pretreatment) and .1, .25, .50, .75, 1, 6, 12, 24, 48, 72 and 96 h posttreatment. The intervals (days) from treatment to ...
Techniques and hazards of embryo manipulation and induction of parturition. Recent advances in reproductive physiology offer ways for exploiting superior, female cattle and for manipulating physiological events such as parturition. The techniques involved in these advances and their associated hazards are the subject of this review.
The applied pharmacology of azaperone in ponies. The butyrophenone tranquilliser, azaperone, was administered intramuscularly to ponies in five series of experiments, using a dose level of 0-4 mg/kg once and 0-8 mg/kg four times. An excellent or good sedative effect was usually obtained with both dose levels, but the response was more consistent with the higher dose. The onset of sedation was apparent within 10 min of administration, the maximal effect usually occurring between 20 and 60 min while sedation was no longer apparent after 2 to 6 h. Body temperature was reduced in all animals for at least 2 h and respiratory rate was increased in...
Hot film coronary artery velocity measurements in horses. Coronary velocity measurements have been carried out in anaesthetized, open-chest horses using a constant-temperature, hot-film anemometer system. L-shaped needle probes inserted by direct vessel puncture have been used to measure velocity profiles in the left common, left anterior descending (LAD), and left circumflex coronary arteries. The flow conditions were characterized by peak Reynolds numbers from approximately 200 to 1500 and values of the unsteadiness parameter from 3 to 10. These measurements indicate that in the left common coronary artery the profile is in general skewed towards t...
Normal and abnormal xylose absorption in the horse. The D-xylose absorption test was applied to clinically normal horses and to horses with signs of gastrointestinal disease. A dosage of 0.5 grams of xylose per kilogram of bodyweight was useful in detecting horses that absorbed the pentose abnormally. The clinical findings were correlated with gross and microscopic findings by biopsy and at necropsy. Gastrointestinal lesions associated with abnormal xylose absorption were classified as: 1) villous atrophy; 2) edema of the lamina propria or 3) necrosis of the lamina propria.
A comparison of techniques for the quantitative analysis of hyaluronic acid in equine synovial fluid. A comparison of methods of preparing the hyaluronic acid of equine synovial fluid for quantitative spectrophotographic analysis is presented. A new method is proposed which appears superior to the previous methods.
