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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.
Effect of route of administration and age on the pharmacokinetics of amikacin administered by the intravenous and intraosseous routes to 3 and 5-day-old foals.
Equine veterinary journal    September 1, 1994   Volume 26, Issue 5 367-373 doi: 10.1111/j.2042-3306.1994.tb04405.x
Golenz MR, Wilson WD, Carlson GP, Craychee TJ, Mihalyi JE, Knox L.The suitability of the intraosseous (i.o.) route for drug administration to equine neonates was evaluated in a study comparing the pharmacokinetics of amikacin administered by the i.o. and intravenous (i.v.) routes. Using a cross-over study design amikacin sulphate (7 mg/kg bwt) was administered i.o. or i.v. to 6 healthy foals at 3 and 5 days of age. Amikacin was instantaneously and completely absorbed after i.o. administration, achieving a mean +/- sd peak concentration (34.17 +/- 3.54 micrograms/ml) in the first sample collected 3 min after administration which was not significantly differen...
Equine hoof function investigated by pressure transducers inside the hoof and accelerometers mounted on the first phalanx.
Equine veterinary journal    September 1, 1994   Volume 26, Issue 5 362-366 doi: 10.1111/j.2042-3306.1994.tb04404.x
Dyhre-Poulsen P, Smedegaard HH, Roed J, Korsgaard E.The dampening of hoof impact was investigated by measuring the accelerations transmitted through structures of the hoof in horses trotting freely on an asphalt tarmac. The hoof dampened the vibrations transmitted to the first phalanx. Shoeing decreased the viscous dampening and increased the median power frequency and the maximal amplitude of the vibrations transmitted to the first phalanx. The pressure inside the digital cushion of the foreleg was recorded. The pressure dropped during the stance phase, indicating expansion of the hoof. The expansion of the hoof was not produced by frog or sol...
Plasma concentrations of prolactin, glucose, insulin, urea nitrogen, and total amino acids in stallions after ingestion of feed or gastric administration of feed components.
Journal of animal science    September 1, 1994   Volume 72, Issue 9 2345-2353 doi: 10.2527/1994.7292345x
DePew CL, Thompson DL, Fernandez JM, Southern LL, Sticker LS, Ward TL.Concentrations of prolactin, glucose, insulin, urea N, and total amino acids in plasma of stallions after ingestion of pelleted feed were compared to those after direct gastric administration of water, NaCl, egg albumin, or corn starch (Exp. 1) or water, egg albumin, hydrolyzed casein (Amicase), or a mixture of indispensable amino acids (Exp. 2). Stallions were fed once daily (75% pellet and 25% hay) at 1500 for 30 d. On d 22, 24, 26, 28, and 30, blood samples were collected every 30 min from 1 h before through 4 h after treatment, which occurred at 1100. In Exp. 1, there was a positive secret...
Proteins induced by recombinant equine interferon-beta 1 within equine peripheral blood mononuclear cells and polymorphonuclear neutrophilic granulocytes.
Veterinary immunology and immunopathology    September 1, 1994   Volume 42, Issue 3-4 221-235 doi: 10.1016/0165-2427(94)90069-8
Heinz H, Marquardt J, Schuberth HJ, Adolf GR, Leibold W.Peripheral blood mononuclear cells (PBMC) and polymorphonuclear neutrophilic granulocytes (PMN) as well as embryonic equine dermal fibroblasts and the equine fibroblast line E. Derm which were used as controls, were treated with recombinant equine interferon-beta 1 (rEqIFN-beta 1) in vitro which induced the expression of different proteins in these cells. A 74 kDa protein was induced in PBMC and an 82 kDa protein was additionally found in the equine fibroblast E. Derm cell line following treatment with rEqFN-beta 1. Both proteins reacted with anti-mouse and anti-human Mx protein antisera in im...
Short-term secretion patterns of corticotropin-releasing hormone, arginine vasopressin and ACTH as shown by intensive sampling of pituitary venous blood from horses.
Neuroendocrinology    September 1, 1994   Volume 60, Issue 3 225-236 doi: 10.1159/000126755
Alexander SL, Irvine CH, Donald RA.To characterize the short-term ACTH secretion pattern and to investigate factors regulating it, pituitary venous (PV) blood was collected using our nonsurgical method from 8 unperturbed horses every 20 or 30 s for approximately 1 h. In all but 1 horse, sampling occurred during the broad circadian maximum in plasma cortisol concentrations. Concentrations of corticotropin-releasing hormone (CRH; n = 7 horses), arginine vasopressin (AVP), ACTH and cortisol were measured by radioimmunoassay. In all horses, CRH, AVP and ACTH secretion patterns appeared irregular in time and amplitude. The mean (+/-...
Effects of alpha 2-agonists on intrauterine pressure and sedation in horses: comparison between detomidine, romifidine and xylazine.
Zentralblatt fur Veterinarmedizin. Reihe A    September 1, 1994   Volume 41, Issue 7 523-529 doi: 10.1111/j.1439-0442.1994.tb00120.x
Schatzmann U, Jossfck H, Stauffer JL, Goossens L.The effect of three alpha 2-agonistic sedatives, Detomidine (0.04 mg/kg), Romifidine (0.08 mg/kg) Xylazine (1.1 mg/kg) and placebo (NaCl), on intrauterine pressure was investigated with an intrauterine balloon model in four non-pregnant warmblood mares. Within 6.0 (+/- 2.2) min mean pressure increases of 9.80 (+/- 3.74), 6.88 (+/- 3.95) and 13.95 (+/- 5.19) mmHg were recorded for Detomidine, Romifidine and Xylazine, respectively. Placebo had no significant effect. The mean duration of pressure increase was 30.0 (+/- 5.10), 17.67 (+/- 9.87) and 19.50 (+/- 13.78) min for Detomidine, Romifidine a...
Equine demineralized bone matrix: relationship between particle size and osteoinduction.
Veterinary surgery : VS    September 1, 1994   Volume 23, Issue 5 386-395 doi: 10.1111/j.1532-950x.1994.tb00499.x
Vail TB, Trotter GW, Powers BE.The osteoinductive capability of four particle sizes of equine demineralized bone matrix (DBM) was evaluated. Matrix particles were implanted in brachiocephalicus muscle pouches in six horses and were harvested 8 weeks later. Matrix particle sizes of 2.0 mm3 to 4.0 mm3 and 5.0 mm3 to 10.0 mm3 were associated with osteoinductive activity and minimal signs of local inflammation. The two smaller particle sizes (0.425 mm3 to 0.850 mm3 and 0.850 mm3 to 2.0 mm3) were minimally osteoinductive and were associated with a greater local inflammatory response. Microscopic events associated with new bone p...
Prepartum adrenocortical maturation in the fetal foal: responses to ACTH.
The Journal of endocrinology    September 1, 1994   Volume 142, Issue 3 417-425 doi: 10.1677/joe.0.1420417
Silver M, Fowden AL.The present study was carried out on 19 chronically catheterized mares and fetuses in late gestation (term > 320 days). In six animals which were monitored up to the time of delivery of a live foal, plasma and amniotic fluid cortisol concentrations remained low until 4-5 days before parturition when there was a rapid, significant rise (P < 0.05) which was not accompanied by any corresponding changes in maternal plasma cortisol. Circulating fetal ACTH concentrations became more variable close to delivery and ANOVA revealed no significant increases during this critical period, although a n...
In vitro comparison of the effect of parallel and divergent transfixation pins on breaking strength of equine third metacarpal bones.
American journal of veterinary research    September 1, 1994   Volume 55, Issue 9 1327-1330 
McClure SR, Watkins JP, Ashman RB.Breaking strength (torque at failure) of equine third metacarpal bones, with transfixation pins placed parallel in the frontal plane and 30 degrees divergent from the frontal plane, was determined in vitro. Two transfixation pins were placed through the distal metaphysis, using a jig designed to drill the holes in the assigned configuration. Paired metacarpal bones II through IV from 12 horses were tested in torsion. The torsional moment of the force applied through the transfixation pins at failure was compared for each limb. Metacarpal bones with divergent pins were significantly (P = 0.030)...
Beta-glucuronidase and trypsin inhibitor capacity of tracheal lavage fluid as indicators of seasonal airway irritation in the horse.
Equine veterinary journal    September 1, 1994   Volume 26, Issue 5 385-391 doi: 10.1111/j.2042-3306.1994.tb04408.x
Maisi P, Koivunen AL, Rantala AR, Turgut K.The health of the respiratory tracts of 19 horses was studied for 11 months. The horses were placed into 3 groups (healthy, periodically diseased and continuously diseased) based on the measurements of blood gases, intrapleural pressure and on neutrophil content of tracheal mucus. Lysosomal enzymes (N-acetyl-beta-D-glucosaminidase and beta-glucuronidase) and reflectors of the proteolytic system (plasmin, plasminogen, trypsin inhibitor capacity) were determined. beta-glucuronidase appeared to be a good indicator of the presence of disease of the respiratory system. High beta-glucuronidase value...
Differential artificial ventilation in anesthetized horses positioned in lateral recumbency.
American journal of veterinary research    September 1, 1994   Volume 55, Issue 9 1319-1326 
Moens Y, Lagerweij E, Gootjes P, Poortman J.Effects of differential ventilation on gas exchange were studied in 7 isoflurane-anesthetized, laterally recumbent horses, and were compared with effects of conventional ventilation, using similar minute volume. A tracheal tube-in-tube intubation technique allowed each lung to be connected separately to an anesthetic circle system with a ventilator. Two distribution patterns of tidal volume were investigated; half the tidal volume was distributed to each lung and two-thirds the tidal volume was distributed to the dependent lung. Effects of the combination of these patterns with positive end-ex...
The basement membrane at the equine hoof dermal epidermal junction.
Equine veterinary journal    September 1, 1994   Volume 26, Issue 5 399-407 doi: 10.1111/j.2042-3306.1994.tb04410.x
Pollitt CC.In the equine hoof, the basement membrane connects the heavily keratinised hoof wall to the dense connective tissue of the distal phalanx, a region able to withstand considerable mechanical stress. This study investigated the properties of this important anatomical and physiological structure. In contrast to haematoxylin and eosin, the connective tissue stains, periodic acid Schiff, periodic acid silver methenamine and Azan showed good resolution of lamellar basement membrane. The lamellar basement membrane cross-reacted with mouse monoclonal antibodies raised against human laminin, thereby pr...
Capillary blood transit time in muscles in relation to body size and aerobic capacity.
The Journal of experimental biology    September 1, 1994   Volume 194 69-81 doi: 10.1242/jeb.194.1.69
Kayar SR, Hoppeler H, Jones JH, Longworth K, Armstrong RB, Laughlin MH, Lindstedt SL, Bicudo JE, Groebe K, Taylor CR.The mean minimal transit time for blood in muscle capillaries (tc) was estimated in six species, spanning two orders of magnitude in body mass and aerobic capacity: horse, steer, dog, goat, fox and agouti. Arterial (CaO2) and mixed venous (CvO2) blood O2 concentrations, blood hemoglobin concentrations ([Hb]) and oxygen uptake rates were measured while the animals ran on a treadmill at a speed that elicited the maximal oxygen consumption rate (VO2max) from each animal. Blood flow to the muscles (Qm) was assumed to be 85% of cardiac output, which was calculated using the Fick relationship. Total...
Heterogeneity of pericyte populations in equine skeletal muscle and dermal microvessels: a quantitative study.
Anatomia, histologia, embryologia    September 1, 1994   Volume 23, Issue 3 232-238 doi: 10.1111/j.1439-0264.1994.tb00472.x
Sims D, Horne MM, Creighan M, Donald A.The objective of this ultrastructural investigation was to determine if populations of pericytes in equine dermal and skeletal muscle capillaries increase in a head-to-foot direction, as has been reported in human skeletal muscles. Samples of equine microvessels were obtained from the longissimus dorsi skeletal muscle 150 cm. from the ground, from the dermis above this muscle, from the extensor carpi radiali muscle at 55 cm. from the ground, from the dermis adjacent to that muscle, and from dermis 15 cm. from the ground, just above the hoof wall. Tissues were processed for transmission electro...
Differential distribution of immunoreactive S-100 protein in mammalian testis.
Histochemistry    September 1, 1994   Volume 102, Issue 3 241-245 doi: 10.1007/BF00268901
Amselgruber WM, Sinowatz F, Erhard M.The present study deals with the immunohistochemical localization of S-100 protein in the testes of seven mammalian species including rat, cat, dog, pig, sheep, cattle and horse. Significant differences are demonstrated in the cellular distribution and intensity of immunoreaction for the protein. In bull, ram, boar and cat testes S-100 protein was localized in the cytoplasm and nuclei of Sertoli cells. A particularly intense staining was seen in the modified Sertoli cells of the terminal tubular segment. With the exception of the cat and horse S-100 protein immunoreactivity was additionally fo...
Gait and respiration in standardbred horses when pacing and galloping.
Research in veterinary science    September 1, 1994   Volume 57, Issue 2 233-239 doi: 10.1016/0034-5288(94)90063-9
Evans DL, Silverman EB, Hodgson DR, Eaton MD, Rose RJ.The relationship between gait and the respiratory response to exercise was examined in five standardbred racehorses which exercised on a treadmill at a pace and a gallop. After an initial warm-up, respiratory rate and stride frequency were measured after one and two minutes of treadmill exercise at 80 per cent of maximal oxygen consumption (VO2max), after one minute at 100 per cent VO2max and after two minutes at 100 per cent VO2max (galloping horses only). Exercise at 100 per cent VO2max continued until the horses showed signs of fatigue. Arterial blood was collected during exercise and when ...
Use of sodium bicarbonate by equine practitioners.
Journal of the American Veterinary Medical Association    August 15, 1994   Volume 205, Issue 4 535-536 
Skand DL.No abstract available
Oestrus synchronisation and superovulation using equine FSH in crossbred ewes.
The Veterinary record    August 13, 1994   Volume 135, Issue 7 164-165 doi: 10.1136/vr.135.7.164
Sharma VK, Gupta RC, Khurana NK, Khar SK.No abstract available
Molecular cloning and expression of two horse pancreatic cDNA encoding colipase A and B.
Biochimica et biophysica acta    August 4, 1994   Volume 1213, Issue 3 357-360 doi: 10.1016/0005-2760(94)00096-4
Crenon I, Granon S, Chapus C, Kerfelec B.Pancreatic colipase plays an essential role in the intestinal fat digestion by anchoring lipase on lipid/water interfaces in the presence of bile salts. In contrast to other species, two molecular forms of colipase, A and B, have been found in horse. The two corresponding cDNAs were isolated from a horse pancreatic library and their nucleotide sequences were determined. Moreover, for the first time, active colipase has been obtained after transfection of COS cells by either colipase A or B cDNA.
The effects of butorphanol on locomotor activity in ponies: a preliminary study.
Journal of veterinary pharmacology and therapeutics    August 1, 1994   Volume 17, Issue 4 323-326 doi: 10.1111/j.1365-2885.1994.tb00253.x
Nolan AM, Besley W, Reid J, Gray G.No abstract available
The pathobiology and repair of tendon and ligament injury.
The Veterinary clinics of North America. Equine practice    August 1, 1994   Volume 10, Issue 2 323-349 doi: 10.1016/s0749-0739(17)30359-0
Goodship AE, Birch HL, Wilson AM.Injury of the collagenous structures comprising tendons and ligaments, either from acute trauma or from repetitive strain lesions, results in protracted periods of disability. The resolution of such injuries often fails to restore the normal morphologic and functional characteristics of the structure and, therefore, either compromises the future performance of the individual or predisposes to an increased risk of recurrent injury.
Thermal sensitivity of mares’ milk proteins.
The Journal of dairy research    August 1, 1994   Volume 61, Issue 3 419-422 doi: 10.1017/s0022029900030843
Bonomi F, Iametti S, Pagliarini E, Solaroli G.No abstract available
[The horse: more than recreation].
Soins. Psychiatrie    August 1, 1994   Issue 166-167 22-24 
Claes MR, Guidal V, Miche D.No abstract available
Functional anatomy of tendons and ligaments in the distal limbs (manus and pes).
The Veterinary clinics of North America. Equine practice    August 1, 1994   Volume 10, Issue 2 273-322 doi: 10.1016/s0749-0739(17)30358-9
Denoix JM.Tendons and ligaments of the equine distal limbs have a prominent anatomic, functional, and clinical importance. This article reviews the descriptive and topographic anatomy of these structures in details. Special information is given about the mechanical properties and functional anatomy of the flexor tendons, accessory ligaments, and third interosseous muscle, as well as about their roles during the standing position and gaits.
Plasma disposition of amikacin and interactions with gastrointestinal microflora in Equidae following intravenous and oral administration.
Journal of veterinary pharmacology and therapeutics    August 1, 1994   Volume 17, Issue 4 291-298 doi: 10.1111/j.1365-2885.1994.tb00248.x
Horspool LJ, Taylor DJ, McKellar QA.Amikacin was detectable (> 0.02 micrograms/ml) in plasma for 12 h in horses and donkeys and for 8 h in ponies following intravenous (i.v.) administration at a dose rate of 6 mg/kg bodyweight. The elimination half-life (harmonic mean) of amikacin was 2.8, 1.6 and 1.9 h in horses, ponies and donkeys, respectively, and the mean body clearance was relatively slow (45.2, 82.4 and 58.0 ml/h.kg, respectively). A suitable dosage interval for the i.v. administration of amikacin sulphate to horses, ponies and donkeys, at a dose rate of 6 mg/kg, would be every 8 h in horses, and every 6 h in ponies an...
Effect of bacterial lipopolysaccharides on sulfated glycosaminoglycan metabolism and prostaglandin E2 synthesis in equine cartilage explant cultures.
American journal of veterinary research    August 1, 1994   Volume 55, Issue 8 1127-1138 
MacDonald MH, Stover SM, Willits NH, Benton HP.The metabolic responses of equine articular cartilage to incubation with bacterial lipopolysaccharide (LPS) were studied, using explant cultures of articular cartilage obtained from the metatarsophalangeal joints of 15 horses, age of which ranged from 3 months to 20 years. For comparison, explants were also established from the metatarsophalangeal joints of 3 calves. Explants were cultured for 3 days in medium containing various concentrations of LPS from 0 (control) to 100 micrograms/ml. Glycosaminoglycan (GAG) released during the 3-day incubation was determined by a spectrophotometric assay,...
The pharmacokinetics and pharmacodynamics of procainamide in horses after intravenous administration.
Journal of veterinary pharmacology and therapeutics    August 1, 1994   Volume 17, Issue 4 265-270 doi: 10.1111/j.1365-2885.1994.tb00243.x
Ellis EJ, Ravis WR, Malloy M, Duran SH, Smyth BG.Six horses were administered either 15 or 20 mg/kg body weight (b.w.) procainamide (PA) as an intravenous (i.v.) dose over 10 min. The plasma concentrations of PA and N-acetylprocainamide (NAPA) as well as the pharmacodynamic effect (prolongation of the QT interval) were monitored. The PA plasma concentrations could be described by a one-compartment model with a t1/2 of 3.49 +/- 0.61 h. The total body clearance of PA was 0.395 +/- 0.090 l/hr/kg and the volume of distribution was 1.93 +/- 0.27 l/kg. As observed after PA administration, NAPA (an active metabolite) had a t1/2 longer than PA of 6....
Interaction of equine spermatozoa with oviduct epithelial cell explants is affected by estrous cycle and anatomic origin of explant.
Biology of reproduction    August 1, 1994   Volume 51, Issue 2 222-228 doi: 10.1095/biolreprod51.2.222
Thomas PG, Ball BA, Brinsko SP.Regulation of attachment of equine spermatozoa to homologous oviduct epithelium was investigated by co-culture of spermatozoa with oviductal epithelial cell explants. Stallion spermatozoa were incubated with explants derived from the isthmus and ampulla of follicular, postovulatory, and diestrous mares. Steroid treatments (estradiol, progesterone, or control) were applied across all explant groups. Estimates of motility and total numbers of attached spermatozoa were made 0.5, 24, and 48 h after initiation of co-culture. Equine spermatozoa attached by their rostral acrosomal region to both cili...
Effect of seminal plasma on motion characteristics of epididymal and ejaculated stallion spermatozoa during storage at 5 degrees C.
DTW. Deutsche tierarztliche Wochenschrift    August 1, 1994   Volume 101, Issue 8 319-322 
Braun J, Torres-Boggino F, Hochi S, Oguri N.The objective of this experiment was to examine the effect of seminal plasma on motion characteristics of epididymal and ejaculated equine spermatozoa during storage at 5 degrees C. Epididymal spermatozoa were flushed with either seminal plasma or a skim milk-glucose extender. Ejaculated spermatozoa were collected with extender added 10 minutes after semen collection and addition of extender during ejaculation by placing 50 ml extender in the collection bottle. Semen samples were centrifuged and resuspended with a skim milk-glucose extender containing seminal plasma (0, 5 and 25%; v/v), prepar...
[A comparison of cardiac stroke volume determination using the thermodilution method and PW-Doppler echocardiography for the evaluation of systolic heart function in the horse].
DTW. Deutsche tierarztliche Wochenschrift    August 1, 1994   Volume 101, Issue 8 312-315 
Stadler P, Kinkel N, Deegen E.In 14 horses without heart disease stroke volume determination were established by pulsed wave doppler echocardiography. Thermodilution and doppler echocardiography were used simultaneously. The doppler echocardiographic volume determinations were carried out in left and right outflow tracts. Echocardiographically Velocity Time Integral, Maximum Flow Velocity, Mean Flow Velocity and Acceleration Time were ascertained. To be able to compare heart volumes of horses with different body weight stroke volume was applied to 1 kg of body weight (= heart index). Heart Index determined with thermodilut...