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.
Folin M, Gennari G, Jori G.The irradiation of horse and sperm-whale Fe” or Fez’ myoglobins with visible light
showed that axial ligands that render the heme diamagnetic (e.g. 02, CO or CN-) endow the
hemoproteins with a marked photosensitivity. In contrast, high-spin myoglobins are unaffected by
visible light. These findings appear to be of general validity for all hemo-proteins and are in agreement
with the involvment of the triplet state of the heme as the reactive intermediate. In all cases, the overall
photoprocess occurs within a very narrow spatial range, leading to specific modification of these
photoox...
Augustinsson KB, Bartfai T, Mannervik B.The steady-state kinetics of the butyrylcholinesterase-catalysed hydrolysis of butyrylthiocholine and thiophenyl acetate were shown to deviate from Michaelis-Menten kinetics. The ;best' empirical rate law was selected by fitting different rate equations to the experimental data by non-linear regression methods. The results were analysed in view of two alternative interpretations: (1) the reaction is catalysed by a mixture of enzymes, or (2) the activity is due to a single enzyme displaying deviations from Michaelis-Menten kinetics. It was concluded that the second alternative applies, and this...
Swierstra EE, Gebauer MR, Pickett BW.The cycle of the seminiferous epithelium of the stallion was
divided into eight stages, using as criteria the presence of meiotic divi-
sions, shape of the spermatid nuclei and location of spermatids with
elongated nuclei in the tubule. The mean frequencies ofstages 1 to 8 were
16\m=.\9, 14\m=.\9, 3\m=.\2, 15\m=.\8, 7\m=.\4, 13\m=.\5, 12\m=.\6 and 15\m=.\7%, respectively. The
duration of one cycle of the seminiferous epithelium was 12\m=.\2 days
(S.E.\m=+-\0\m=.\1) as determined by injecting a single dose of 700 \g=m\Ciof
[3H]thymidine into each spermatic artery of six stallions and rem...
Sainsbury DW.The physiological requirements of the horse appear to be reasonably well established and should be adequately provided by ventilation based on straightforward principles, relying largely on natural air flow. On the other hand, there are few objective values for ventilation required to promote good health or alleviate equine respiratory disease. In the absence of such knowledge it is only possible to rely on a logical application of sound principles and experience. Both indicate the satisfactory nature of ventilation by stack effect, aspiration and perflation. Buildings should be well insulated...
Hall LW.Catheters were implanted through the left atrium into large veins drawing blood from regions of the diaphragmatic lobes in five ponies. Measurement of oxygen and carbon dioxide tensions in blood samples drawn through these catheters showed that in laterally recumbent conscious and anaesthetised animals the function of the lowermost lung is progressively impaired while in the supine position the function of both lungs is adversely affected.
Troyer DL, Oyster RO, Hunt MC.The purpose of this study was to find a combination histochemical staining technique for the evaluation of equine skeletal muscle that is reliable and effective, while offering a substantial reduction in the labor and cost involved with currently used individual histochemical methods. Several combinations under varying conditions of pH were studied. The most uniform results were obtained using an acid preincubation step at an optimal pH of 4.2 followed by reduced nicotinamide adenine dinucleotide-tetrazolium reductase (NADH-TR) and the remainder of the acid-ATPase procedure.
Hunt RJ, Moore JN, Allen D.In 6 adult horses anesthetized with pentobarbital, the hemodynamic responses of the equine digit to infusion of dopamine were evaluated by use of an isolated extra corporeal pump perfused digital preparation. Digital blood flow was maintained at a constant rate that was independent of systemic hemodynamic changes. Three sequential experiments were performed on each horse. In the first experiment (n = 6), dopamine was infused IV at rates of 1.0, 2.5, and 5.0 micrograms/kg/min. For the second experiment (n = 5), dopamine (400 micrograms/ml) was infused into the digital artery at the rates of 0.0...
Derar R, Haramaki S, Hoque S, Hashizume T, Osawa T, Taya K, Watanabe G, Miyake Y.To elucidate the physiological role of insulin-like growth factor-I (IGF-I) during early pregnancy in mares, number of ovarian follicles was monitored ultrasonically during different stages of the first trimester of pregnancy in 36 thoroughbred mares. From 9 of 36 mares, blood samples were collected weekly from the mating day till the end of the first trimester of pregnancy and plasma IGF-I profiles were examined with other hormones, like follicle stimulating hormone (FSH), luteinizing hormone (LH), ir-inhibin, progesterone and estradiol-17beta. Plasma IGF-I level fluctuated throughout the stu...
Weaver MP, Shaw DJ, Munaiwa G, Fitzpatrick DP, Bellenger CR.The objectives of this study were to topographically map pressure distribution across the palmar surface of the navicular bone in response to forces applied by the deep digital flexor tendon (DDFT), and evaluate the effect of raising the heels in vitro . A rig was constructed to hold an equine cadaver limb and apply controlled pressure to the navicular bone from the DDFT. Pressure-sensitive paper was used to quantify and map the resultant pressure. Changes in response to heel wedges (5 degrees and 10 degrees ) were recorded. The areas subject to maximum pressure from the DDFT were: the central...
Kouider S, Kolb FE, Müller I, Pfüller C, Schneider J.Horses were examined for the behaviour of various blood constituents prior to and following infusions of solutions of glucose, fructose, invertose, and sorbitol. Infusion of 0.5 g/kg live weight glucose to six horses was followed by half-life variation between eleven and 23 minutes. Subsequent infusion of invertose to the same animals usually caused prolongation of glucose half-life. Half-life values were between 17 and 33 minutes for fructose and between 21 and 80 minutes for glucose. Infusion of 0.5 g/kg live weight fructose to two horses was followed by half-life values between 17 and 18 mi...
Dunnett M.N-alpha-Acetyl-L-carnosine (NAcCAR) in perchloric acid extracts of equine plasma was assayed by high-performance liquid chromatography on a 3 microns Hypersil ODS (150 x 4.6 mm I.D.) column eluted with 5 mM phosphoric acid-1 mM triethylamine, pH 2.58. NAcCAR was isolated by solid-phase extraction on Isolute PRS (propylsulphonyl) columns. The HPLC mean retention time for NAcCAR was 5.9 +/- 0.2 min. The recovery from plasma by solid-phase extraction was 93.9-99.7% and lower limit of detection in plasma was 0.18 microM. The normal NAcCAR concentration in equine plasma was 2.4 +/- 0.3 microM. The ...
Attenburrow DP, Flack FC, Portergill MJ.The technique of impedance plethysmography is described and its application to observation of lung volume changes in the horse at exercise is discussed. The results from horse at rest show that there is a close relationship between rate of lung volume change (flow rate) and the associated impedance changes during both inspiration and expiration. Impedance changes during exercise were related to inspiration and expiration by observation of associated respiratory sounds. Artefacts related to technical difficulties are also indicated.
Bertone JJ.Six standing awake adult horses were instrumented for measurement of mean arterial, central venous, and pulmonary arterial blood pressures (mm of Hg), thermodilution cardiac output (ml/kg/min), and pulmonary arterial blood temperature (C). Total peripheral resistance was calculated from these values. Base-line data were accumulated, and a single dose of hydralazine HCl (0.5 mg/kg) was administered IV. Horses were monitored for 420 minutes after hydralazine administration. Mean arterial and central venous blood pressures did not change from the base-line values. Cardiac output and heart rate we...
Nequin LG, King SS, Roser JF, Soderstrom BL, Carnevale EM, Neumann KR.The reproductive activity of light horse mares (n=12) was monitored each day from 3 September until 29 January, or until the mares entered anoestrus, by behaviour evaluation, ultrasonography and blood sampling. Follicles, corpora lutea and ovulation, as well as oestradiol, progesterone, and LH and FSH concentrations, were analysed to determine a reproductive profile for the transition into anoestrus. The results of the present study indicate that light horse mares progress through four phases during the autumn transition into anoestrus: (i) normal cycles; (ii) aberrant cycles; (iii) anovulatio...
Robinson NE.The primary function of the equine respiratory system is the exchange of oxygen and carbon dioxide at a rate that is matched to metabolism. Gas exchange requires ventilation, distribution of gas within the lung, perfusion of blood through pulmonary capillaries, matching of ventilation and blood flow, diffusion of gases between air and blood, and transport of gases to and from the muscles. In this article, the author reviews what is known about each of these processes in the resting and exercising horse.
Bjorck G, Nilsson G.Sixteen cases of chronic hoof changes seen in Standardbred trotters are described. The chief defect is decomposition of the horn. The disease process usually commences on the weight-bearing surface and spreads to underrun both the sole and wall. Histopathological studies revealed marked swelling and vacuolation of the cells of the stratum corneum, increased proliferation in the stratum germinativum, and monocytic infiltration in the corium. Treatment comprised complete removal of underrun horn and exposure of the affected area. In severe cases, a course of penicillin is administered. The lengt...
MacDougall DF.The proteins IgG and IgG(T) are the predominant immunoglobulins in equine colostrum. Their distribution and catabolism were studied in the newborn foal using an isotopic tracer technique. More precise quantitation of the absorption of these immunoglobulins from colostrum is now possible.
Sanada Y, Noda H, Nagahata H.The blastogenic response of lymphocytes from 16 newborn foals naturally infected with Rhodococcus equi was investigated, in order to evaluate the relationship between R. equi infection and depressed host response. Naturally infected foals showed evidence of R. equi infection at 5-6 weeks of age, as determined by clinical, haematological, bacteriological and serological methods. The blastogenic response of lymphocytes against phytohaemagglutinin was significantly depressed (stimulation index < 1.80; P < 0.01, P < 0.05) in R. equi-infected foals at 5-6 weeks of age compared with those o...
Scandurra R, Politi L, Santoro L, Consalvi V.Horse liver phosphopantothenoylcysteine decarboxylase (EC 4.1.1.36) incorporates nonexchangeable tritium from borotritide with a decrease of the activity. Substrate prevents both tritium incorporation and the decrease in activity. Acid and base hydrolysis of the tritiated protein releases labeled lactate identified by high-voltage paper electrophoresis, paper chromatography and silicic acid chromatography. These results indicate the presence of pyruvate covalently bound through an ester linkage to phosphopantothenoylcysteine decarboxylase which is then another example of a mammalian enzyme in ...
May SA, Hooke RE, Lees P.Chondrocytes subjected to adverse culture conditions in vitro are stimulated to produce the eicosanoid prostaglandin E2 (PGE2) and the neutral metalloproteinase stromelysin (proteoglycanase). This indicates the potential role of the chondrocyte in cartilage degeneration in equine clinical joint disease and suggests a mechanism which may be involved in the potentiation of the effects of other inflammatory mediators. Therefore, adverse conditions within the joint, such as decreased pH in an inflammatory focus and decreased access of nutrients to deeper layers of cartilage, might contribute to th...
Poole AW, Heath MF, Sage SO, Evans RJ.Equine platelets in platelet-rich plasma were incubated with the fluorescent indicator dye, Fura-2-AM (Fura-2-acetoxymethyl ester) and the degree of loading of the cells with the dye and the extent of hydrolysis of the ester was assessed by quantitative fluorimetry and by thin-layer chromatography respectively. Under these conditions the cells loaded poorly with Fura-2 to a concentration of 4 microM. The technique was validated by demonstrating adequate loading of human platelets with Fura-2, to a concentration of 250-300 microM, using the same method. The removal of plasma from the extracellu...
Joppich-Kuhn R, Luisi PL.The interaction between horse liver alcohol dehydrogenase and the oxidized and reduced forms of the 3-thionicotinamide--adenine dinucleotide coenzyme analogues (sNAD and sNADH) has been investigated by ultraviolet absorption, fluorescence and circular dichroism. The fluorescence of sNADH is enhanced when bound to the enzyme, and the protein fluorescence is quenched by both sNADH (60--65%) and sNAD (65%). The possible origin of the larger quenching produced by sNAD with respect to that of NAD is discussed. Coenzyme dissociation constants have been determined by monitoring the quenching of the p...
Cothran EG, Henney PJ, King JA.The inheritance of the equine Tf F3 allele was examined in 39 parent-offspring combinations. For 26 of the cases the allele inherited by the offspring from the heterozygous parent could be determined. The proportion of individuals that inherited the F3 variant compared to the alternative allele was exactly 1:1. In five cases the parental phenotype was identical to that of the offspring. For the remaining eight cases the parent was homozygous for the F3 allele and all offspring had the F3 allele. The results were consistent with Mendelian inheritance.
Hohenhaus MU, Lehmann B.Ultrasonography is a good means of monitoring follicular development in the mare and allows objective observation and measurement of follicular growth as well as identification of corpora lutea and hematoma in the ovary. The significance of ultrasonography in this field lies in the specific anatomical structure of the mare's ovary and the different phenomena preceding and accompanying ovulation, which are described in this paper. The last part deals with the handling and use of ultrasonography.
Kovár J.Changes in the concentration of lactate in the blood are described as a response to gradated physical strain, consisting of 1140 m of walk, 2 x 1000 m of trot, and 3 x x 5000 m of gallop in seven horses in thirteen experiments. The dependence of lactate concentration on speed in different track sections was examined and the aerobic and anaerobic stages of metabolism were clearly differentiated. It appears realistic on the basis of the onset and course of anaerobic metabolism to work out tests for evaluating the physical capacities and training abilities of horses.
Evers P, Hoffmann B.This paper describes the use of hormone analysis in the diagnosis of adrenal cortex dysfunction in the dog, cat and horse. Analytical problems concerning the determination of corticosteroid levels are discussed and the pathology of adrenal dysfunction is briefly presented. The paper focuses on the problems in establishing physiological norms for adrenal function based on the established assays. Own experiences and other reported data are referred to.
Kotsiubenko AA.The indexes of standardized deviations by the measured characters (probits) are expedient to be used for distribution of horses according to classes M-, M0 and M+, under these conditions one can select individuals M0 for to rise their capacity for work and expressivity of the type of breed.
Stamer M, Sumpf D.The live weight development of young warm-blooded stallions at the age of 0 to 30 months of life was investigated in order to derive their energy and protein requirement. The aim of the studies was the derivation of a standard curve for the course of growth. Choice of the best suited model and the corresponding calculations were one of the main investigation objects. The mathematical function developed by Janoschek provided a relatively good description of the material.
Pohlmeyer K, Hertsch B.The arterial blood vessels in 24 humeri of equine fetusses and foals are described. The relation between the age and the distribution of these arteries are explained and completely discussed.
Phillips AW, Courtenay JS, Ruston RD, Moore J, Baker C, Epps HB.A simple apparatus is described for the collection of plasma from horses while maintaining their blood in extracorporeal circulation. Using this device, nearly 2.5 kg of plasma protein was collected from a horse during a period of 3 weeks without any obvious adverse effect upon the animal. The blood’s packed cell volume showed little variation throughout this period, although its content of plasma protein was found to fall. The normal plasma protein level was almost completely re-established after 3 weeks rest. A horse immunized with tetanus toxoid and subjectcd to repeated cycles of plasmap...
Smith ID.Progesterone concentration was measured by a protein-binding assay in peripheral plasma samples taken from 8 thoroughbred mares throughout pregnancy and for 2 days after parturition. There were considerable differences between individuals at any one time in gestation but, on average, levels rose during the first 60 days of gestation, fell to a minimum at about 180 days when the accessory corpora lutea regress and finally reached their highest mean value of 11.5 mg/ml±1.2 (S.E.M.) during the period 270 days to term, significantly higher than the mean, 7.6 ng/ml±0.5 (S.E.M) for the whole of ge...
