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.
Watson ED, Sertich PL, Zanecosky HG.Ovulation has been likened to an inflammatory process. Inflammatory cells accumulate in the ovulating follicle, presumably because of chemotactic factors. Chemotactic activity was measured in fluid aspirated from follicles of estrous mares 0, 12, 24, and 36 hours after ultrasonographic detection of a 35-mm follicle and IV treatment with 2,500 IU of human chorionic gonadotropin. Chemotaxis was assessed by measuring directional migration of equine neutrophils under agarose. Follicular fluid acted as a chemoattractant for neutrophils, but there was no significant difference in chemotactic activit...
Johnson L, Varner DD, Tatum ME, Scrutchfield WL.To evaluate the effect of age and season on Sertoli cell number per paired testes, ratio of germ cells per Sertoli cell, and daily sperm production, testes were obtained from 184 adult (4-20 yr) stallions at slaughter throughout one year. Numbers of Sertoli cells or germ cells were derived from nuclear volume density, volume of individual nuclei, and parenchymal volume. Germ cell to Sertoli cell ratios were calculated from cell numbers. Regression analysis was used to detect age-related differences in the breeding season (May-Jul) or throughout the year. A two-way analysis of variance was used...
Abrahams S, Greenwald L, Stetson DL.In mammals, the length of the loops of Henle increases with increasing body size without a concomitant rise in urinary concentrating ability. Because mass-specific metabolic rate falls with increasing body mass, this study sought to determine the extent to which this decline in metabolic rate could explain the low urinary concentrating ability of large mammals with long loops of Henle. Mitochondrial ultrastructural parameters were measured in the medullary thick ascending limbs (mTALs) of a series of nine mammalian genera ranging in body mass from 0.011 kg (bats) to approximately 400 kg (horse...
McCoy HE, Broder CC, Lottenberg R.The species specificities of plasminogen activation and binding of plasmin by pathogenic group C streptococci isolated from humans, horses, and pigs were examined. Of 56 streptococcal isolates, 52 elaborated plasminogen activator activity and 49 of these had specificity for plasminogen of the homologous host. Analysis of supernatants from 13 isolates indicated that the plasminogen activator activity resulted from secreted streptokinases. These 13 streptokinases were antigenically related and bound all three plasminogens, indicating that the binding recognition sites were conserved despite the ...
McKeever KH, Hinchcliff KW, Schmall LM, Muir WW.Exercise-induced changes in renal function were examined during steady-state submaximal treadmill exercise in six unfit mares. Horses were randomly assigned to either an exercise or parallel control (no exercise) trial on day 1 and the alternate trial 1 wk later. The mares ran on a treadmill, set at a 6 degrees incline, for 1 h at 55-60% of maximal heart rate. Exercise significantly (P less than 0.05) increased plasma osmolality, plasma [K+], urine flow (+ 45%), Na+ excretion (+ 371%), K+ excretion (+ 57%), osmotic clearance (+ 32%), Na+ clearance (+ 391%), K+ clearance (+ 33%), and fractional...
Desideri A, Stefanini S, Polizio F, Petruzzelli R, Chiancone E.Apoferritin has been selectively labeled with a maleimide nitroxide derivative at Cys-126, located in the hydrophilic 3-fold channels. Titration of this derivative with Fe(II), which gives rise to the initial Fe(III)-apoferritin complex, produces, at low metal-to-protein ratios, a decrease of the intensity of the label EPR signal due to the occurrence of a magnetic dipolar interaction. A label-metal distance ranging between 8-12 A can be estimated from titrations performed with VO(IV), which is known to bind in the 3-fold channels, and likewise produces a decrease in the label EPR signal. The ...
Manohar M, Hassan AS.The present study was carried out to examine diaphragmatic O2 extraction and lactate and ammonia production during prolonged exhaustive exercise. Experiments were performed on nine healthy exercise-conditioned ponies in which catheters had been implanted in the phrenic vein previously. Blood-gas variables and lactate and ammonia concentrations were determined on simultaneously obtained arterial and phrenic-venous blood samples at rest and during 30 min of exertion at 15 mph + 7% grade (heart rate, 200 beats/min; approximately 90% of maximum). Arterial O2 tension and saturation were maintained ...
Galati P, Roperto F, De Vico G, Restucci B, D'Andrea F.Specimens of the tracheal epithelium were obtained from two sites in nine healthy horses by a fibre optic endoscope. Electron microscopic examination of 53,550 cilia revealed that 5.2 per cent of cilia were atypical. Nine hundred and seventeen (1.7 per cent) were compound, 78 (0.15 per cent) were swollen, 27 (0.05 per cent) were intracytoplasmic and 171 (3.35 per cent) had microtubular defects. These microtubular defects (159 peripheral and 12 central) were found in 5103 cross-sectioned cilia.
Matsuda H, Koyama H, Oikawa M, Yoshihara T, Kaneko M.Addition of sera, collected from Thoroughbred horses after sprint exercise, induced significant neurite outgrowth from chick embryo dorsal root ganglia after a 24-hour culture. The nerve growth factor (NGF)-like activity was detected in sera collected immediately, or 1 hour or more, after the exercise. These findings suggest a possible role of serum NGF-like activity under stress conditions (running exercise) of horses.
Mifune H, Suzuki S, Noda Y, Mohri S, Mochizuki K.In the pig, cattle and horse, the right and left atria and ventricles were examined by immunohistochemistry, and the right atrial and auricular cardiocytes were studied by transmission electron microscopy. Moreover, ANP-granules in the cardiocytes were analyzed by ultrastructural morphometry. Immunohistochemically, the most intensely ANP-reacted cardiocytes were localized in the right auricle, particularly more prominent in the pig and cattle than in the horse. Ultrastructurally, ANP-granules were located principally in the perinuclear region associated with the Golgi apparatus and throughout ...
Büchi S, Waelchli RO, Corboz L, Gygax AP, Wälti RJ.In the mare, natural breeding is associated with bacterial contamination of the reproductive tract. The purpose of this study was to examine postcoital bacterial contamination and the resulting inflammatory response of the uterus. Uterine swabs for bacteriological and cytological examination were obtained from 80 mares. Each mare was sampled once between 4 and 69 hours postbreeding. In mares which did not conceive, sampling was repeated at the following estrus. The findings were compared with those obtained prior to breeding and correlated with the breeding outcome. Bacteria were cultured from...
Gasthuys F, de Moor A, Parmentier D.The influence of different rates of dopamine and dobutamine on the cardiovascular depression during a standard halothane anesthesia was studied in dorsally recumbent ventilated ponies. Haemodynamic and respiratory responses were investigated by means of cardiac output (CO) determination (thermodilution technique), mean systemic (MAP) and pulmonary artery pressure (MPAP) (direct intravascular method) and arterial blood analysis (blood gases and packed cell volume). An important cardiopulmonary depression characterized by decreases (55% of the standing values) in CO, cardiac index (CI), MAP, MPA...
Malark JA, Nixon AJ, Skinner KL, Mohammed H.Physical, biochemical, and cytologic properties of synovial fluid from digital flexor tendon sheaths of clinically normal horses were investigated. Tendon sheath fluid was pale yellow, clear, and did not clot. Volume of fluid within a tendon sheath varied minimally, with a mean of 2.11 ml. Total erythrocyte counts were higher than values observed in normal equine joint fluid, whereas values for total leukocyte count (770 +/- 73 cells/mm3), viscosity (6.05 +/- 0.58 cs), and protein concentration (7.87 +/- 0.03 mg/ml) were similar to those in joint fluid. Large mononuclear cells were the predomi...
Young DR, Nunamaker DM, Markel MD.Eight untrained 2-year-old Thoroughbred horses were used in a study of the remodeling response of the proximal sesamoid bone (PSB) to training-related stimuli. Two horses each were assigned to 1 of 4 groups: group 1, untrained, pasture turnout (control); group 2, modified-classically trained, dirt track; group 3, classically trained, dirt track; and group 4, classically trained, wood chip track. Horses were given fluorochromic bone labels every 28 days during training. All horses were euthanatized after 5 months of training, and the proximal sesamoid bones (PSB) were removed. A midsagittal sec...
MacKay RJ, King RR, Dankert JR, Reis KJ, Skelley LA.Blood monocytes and alveolar macrophages (AM) were harvested from foals (aged 46 days to 6 months) and cultured in either medium alone or medium containing 10 micrograms/ml bacterial lipopolysaccharide (LPS). After 24 h, culture supernates were collected and analyzed for cytotoxic activity on sensitized L929 cells. Both monocytes and AM that had been treated with LPS produced significantly more cytotoxic activity than the same cell type exposed to medium lacking LPS. LPS-treated macrophages secreted significantly more cytotoxic activity (120 +/- 17.8 U/ml) than did LPS-treated monocytes (47.3 ...
Padilla AW, Foote RH.Slow-cooled stallion spermatozoa, with and without seminal plasma removed by centrifugation, were diluted in Kenney's extender (KE) containing nonfat dry skim milk with glucose and antibiotics or in KE supplemented by adding a modified high-potassium Tyrode's medium (KMT). Four ejaculates from each of four stallions were collected and divided factorially across these four treatments. Percentage of motile sperm, path velocity, and linearity immediately after treatment (0 h) and after storage at 4 degrees C for 24, 48, and 72 h were evaluated objectively by use of a HTM-2030 sperm motility analy...
Turner TA.Thermography has been shown to be a practical aid in the clinical evaluation of lameness. This modality specifically increases the accuracy of diagnosis. Thermography represents skin temperature, usually pictorially. The techniques involve contacting and noncontacting modalities. Noncontacting thermography, which detects infrared radiation, is the most accurate. In order to be accurate, thermography must be performed in a temperature-controlled, draft-free area. The area should be protected from sunlight to avoid erroneous heating of the skin, and the hair length should be uniform. Thermograph...
Watson TD, Sullivan M.The effects of sedation with detomidine on oesophageal function were assessed by contrast radiography in 10 healthy adult thoroughbred horses. Barium swallows were monitored by means of image intensification, first without sedation and then after the intravenous administration of detomidine at doses of 10 and 20 micrograms/kg bodyweight. The transit time of contrast agent to the oesophageal hiatus was recorded and each swallow was scored for markers of oesophageal dysfunction. Analysis of the data indicated that there were highly significant dose dependent increases in the transit time, the re...
Science (New York, N.Y.)July 19, 1991
Volume 253, Issue 5017 306-308 doi: 10.1126/science.1857965
Farley CT, Taylor CR.It is widely thought that animals switch gaits at speeds that minimize energetic cost. Horses naturally switched from a trot to a gallop at a speed where galloping required more energy than trotting, and thus, the gait transition actually increased the energetic cost of running. However, by galloping at this speed, the peak forces on the muscles, tendons, and bones, and presumably the chance of injury, are reduced. When the horses carried weights, they switched from a trot to a gallop at a lower speed but at the same critical level of force. These findings suggest that the trot-gallop transiti...
Stewart DR, Nevins B, Hadas E, Vandlen R.Relaxin, a polypeptide hormone normally associated with pregnancy, has been purified from many species, and the sequence determined for a growing number. Equine relaxin has been previously purified by acetone extraction, gel filtration, and ion exchange chromatographies. In an attempt to develop a more rapid and efficient method for relaxin purification, the use of affinity chromatography coupled with HPLC was explored. Monoclonal antibodies were raised against highly purified equine relaxin; large quantities of antibody were obtained by ascites production and attached to a solid phase support...
Shoemaker RS, Bertone AL, Mohammad LN, Arms SW.Effects of longitudinal compression before and after transection of the accessory ligament of the superficial digital flexor (SDF) muscle were measured in eight equine cadaver forelimbs. When compression was increased from 890 N to 3115 N, the metacarpophalangeal (MCP) and carpal joints hyperextended 20 degrees and 4 degrees, respectively, and strain in the SDF and deep digital flexor tendons was increased 3.5% and 1.4%, respectively. The accessory ligament did not elongate. Immediately after transection of the accessory ligament at 3115 N load, a 2.8 mm gap formed between the transected ends ...
Rutkowski JA, Eades SC, Moore JN.A chronic model with an ultrasonic transit time blood flow probe and strain gauge force transducers implanted on the cecum was used to evaluate cecal mechanical activity and cecal arterial blood flow in 4 conscious adult horses. Intravenous administration of xylazine (1.1 mg/kg of body weight) significantly decreased heart rate and cardiac output, but significantly increased diastolic pulmonary arterial pressure, mean pulmonary arterial pressure, carotid arterial pressure, and central venous pressure. Lateral cecal arterial blood flow after xylazine administration was decreased substantially m...
Warko G, Bostedt H.Eight vital, new-born foals were additionally administered a non-species-specific colostrum-substitute via stomach-tube within the first 18 hours of their life. The substitute had been made of cattle-colostrum. These foals as well as a control-group of eight foals constantly had free access to maternal colostrum. Object of measurement was GGT-activity in the blood-serum. The increase of GGT-activity within the first 24 hours after birth was very low in the control-group (up to 25 U/l), and very high in the tested animals (418 +/- 182 U/l). Obviously there is a direct connection between this ri...
Alwan WH, Carter SD, Dixon JB, Bennett D, May SA, Edwards GB.Synovial fluid samples of horses with osteoarthritis were investigated to detect interleukin-1 (IL-1) activity which could contribute to the disease pathogenesis. Of the 32 samples tested, 12 (37.5 per cent) showed an augmented phytohaemagglutinin induced proliferation of C3H/HeJ mouse thymocytes. Positive results were also seen in horses with infected arthritis, osteochondritis, traumatic arthritis and undefined synovial effusions. Normal synovial fluid and sera from all groups failed to show any detectable IL-1 activity. Fractionation of synovial fluid showed that the IL-1 activity was in th...
Carney NJ, Squires EL, Cook VM, Seidel GE, Jasko DJ.Donor mares of mixed, light-horse breeds, maintained at Colorado State University, provided 104 embryos for immediate transfer (fresh embryos). One hundred and thirty-six additional embryos were collected on various breeding farms in the United States and were shipped to Colorado State University via commercial airlines (cooled embryos). Embryos were harvested 7 d after ovulation, graded, and either transferred into a mare immediately (<1 h) or placed in Ham's F-10 medium plus 10% fetal calf serum in an atmosphere of 5% CO2, 5% O2, 90% N2 and packaged in a passive cooling unit (Equitai...
Madison JB, Hamir AN, Ehrlich HP, Haberman J, Topkis V, Villasin JV.Full-thickness skin wounds were created on the dorsum of both metacarpi in 8 horses. Three topical treatment regimens were studied. All wounds were bandaged with a nonadherent dressing, which was held in place with a snug elastic wrap. Group-A wounds were treated with a proprietary topical wound medication that consisted of a spray and an ointment. Group-B wounds were treated with the same regimen, except the putative active ingredients in the ointment were omitted. Group-C wounds were treated with a dry nonadherent bandage only. Wound dressings were changed every day and the limbs were photog...
Nyman G, Lindberg R, Weckner D, Björk M, Kvart C, Persson SG, Gustafsson H, Hedenstierna G.Eight horses (mean weight 438 kg) with chronic obstructive pulmonary disease (COPD) were studied for clinical signs, ventilation/perfusion relationships (VA/Q) and lung morphology. Four horses were killed and necropsied after the study. In horses with COPD, minute ventilation was almost twice as high as normal, whereas PaO2 was significantly decreased. Cardiac output was normal, but pulmonary artery pressure and pulmonary vascular resistance were significantly increased. The VA/Q distribution was abnormal with an increased scatter of VA/Q ratios. However, shunt (VA/Q = 0) was increased in one ...
Simmons HA, Ford EJ.The production of propionate has been measured in the large colon of two ponies fitted with cannulas and fed on a standard diet of hay or hay and wheat bran. A continuous infusion of 14C-labelled sodium propionate was made into a cannula in the right ventral colon and samples of ingesta were obtained from another cannula near the end of the right dorsal colon. A simultaneous intravenous infusion of [2-3H]-labelled glucose was made to measure total glucose entry. Colonic propionate production on the hay diet was 146 (range 110-176) mg/h per kg body weight and, on the hay and bran, 195 (range 13...
Derksen FJ, Robinson NE, Slocombe RF, Hill RE.In unanesthetized ponies, arterial blood gas tensions, pulmonary mechanics, and lung volumes were determined before and 24 to 48 hours after oral administration of 500 ml of corn oil or 100 mg of 3-methylindole (3MI)/kg of body weight in 500 ml of corn oil. In the latter group, variables were also measured after bilateral cervical vagotomy. Respiratory rate and minute ventilation were increased by 3MI treatment and decreased after vagotomy, suggesting that the tachypnea induced by 3MI was vagally mediated. The arterial O2 tension (PaO2) was unaffected but arterial CO2 tension (PaCO2) decreased...
Rooney JR.Sacroiliac arthrosis is a major cause of "hiking" lameness (often, so-called "stifle lameness") in Standardbred horses. The cause of this arthrosis is found in the moment forces generated as horses negotiate unbanked and underbanked turns and in the forces generated on cambered racing surfaces. The prediction is that such lameness could be virtually eliminated if racetrack and training track turns were properly banked and camber held to a minimum.
Bornmann T, Williams J, Richardson K.The impact of head and neck position (HNP) on horse welfare has received much attention in the scientific literature within the last two decades. Studies have identified physiological and behavioral signs of distress in horses ridden for prolonged time in an HNP with their noseline behind the vertical (BTV), which may compromise their welfare. The objective of this study was to compare potential differences of HNPs shown in horse sales photographs advertised in an Australian horse sales magazine (Horse Deals) from the years 2005 and 2018. In addition, factors potentially impacting HNPs, such a...
De Lille AJ, Silvers ML, Cadario ME, Tran TQ, Cage CL, LeBlanc MM.The effects of the sedatives xylazine (predominantly alpha2 agonist) and acepromazine (predominantly alpha1 antagonist) and their influence on intrauterine pressure were measured in four reproductively normal mares and four mares with delayed uterine clearance. Intrauterine pressure was measured in each mare during oestrus for three 100 min periods using an 8-F catheter with three discrete pressure sensors. After 10 min of baseline recording, xylazine, acepromazine or saline was administered i.v. Oxytocin was administered i.v. after a further 30 min, and pressure recordings were continued for ...
Palm AE, Wattle O, Lundström T, Wattrang E.This study aimed to increase the knowledge on salivary antibodies in the horse since these constitute an important part of the immune defence of the oral cavity. For that purpose assays to detect horse immunoglobulin A (IgA) including secretory IgA (SIgA) were set up and the molecular weights of different components of the horse IgA system were estimated. Moreover, samples from 51 clinically healthy horses were tested for total SIgA and IgG amounts in saliva and relative IgG3/5 (IgG(T)) and IgG4/7 (IgGb) content were tested in serum and saliva. Results showed a mean concentration of 74μg SIgA...
May SA, Hooke RE, Lees P.Equine thymocytes, which respond to equine monocyte supernatants, do not respond to stimulation with recombinant human interleukin-1 alpha and beta, and equine synovial fibroblasts show a limited response in the form of prostaglandin E2 production without any evidence of neutral metalloproteinase production. Human interleukin-1 beta was about three to ten times as active on equine synovial cells as human interleukin-1 alpha in terms of prostaglandin E2 production. This preliminary evidence would suggest that there are qualitative and quantitative differences in the way recombinant human interl...
Sedrish SA, Venugopalan CS, Holmes EP, Koch CE, Moore RM.To determine in vitro vasomotor response of equine large colon arterial and venous rings with and without endothelium to vasodilator drugs, including dopamine (DOP), dopexamine (DPX), acepromazine (ACE), isoxsuprine (ISX), and nifedipine (NFP). Methods: 7 adult horses. Methods: Relaxation of large colon arteries and veins in response to vasodilating drugs was determined by measuring the change in tension of vessel rings when exposed to a cumulative concentration range (10(-8) to 10(-4)M) of each drug. Vessel rings, with and without endothelium, were mounted in organ baths, attached to a transd...
Adeyefa CA.The effects of the various growth factors with regard to the nutritional physiology of zoophilic dermatophytes isolated from horses are reported. The optimum temperature, pH and growth period for the fungal isolates were found to be 30 degrees-35 degrees C, 5-6 and 7-12 days respectively while the carbon and nitrogen sources utilised by the organisms were sucrose, fructose, maltose, L-arginine and calcium nitrate. The use of these factors in preparation of efficacious fungicides used in the treatment of ringworm infections in man and animals is discussed.
BMC research notesNovember 8, 2012
Volume 5 626 doi: 10.1186/1756-0500-5-626
Boudko SP, Ishikawa Y, Lerch TF, Nix J, Chapman MS, Bächinger HP.Hyperelastosis cutis is an inherited autosomal recessive connective tissue disorder. Affected horses are characterized by hyperextensible skin, scarring, and severe lesions along the back. The disorder is caused by a mutation in cyclophilin B. Results: The crystal structures of both wild-type and mutated (Gly6->Arg) horse cyclophilin B are presented. The mutation neither affects the overall fold of the enzyme nor impairs the catalytic site structure. Instead, it locally rearranges the flexible N-terminal end of the polypeptide chain and also makes it more rigid. Conclusions: Interactions of th...
McDonnell SM, Oristaglio Turner RM.Imipramine-induced ex copula ejaculates (11) and fractionated in copula ejaculates were collected from each of 5 pony stallions for freezing in 5-ml straws (6), using a modified Kenney glucose skim-milk extender (2). Initial post-thaw total and progressive motilities and daily post-thaw total and progressive motilities, as well as the number of days to reach 0 progressively motile spermatozoa, were also similar for the 2 methods of collection. The percentage of morphologically normal spermatozoa both before freezing and after thawing were also similar for in copula and ex copula ejaculates. Co...
Mendoza FJ, Mejia-Moreira S, Buchanan BR, Toribio RE, Perez-Ecija A.Insulin dysregulation (ID) and donkey metabolic syndrome (DMS) are common in this species. Contrary to horses, diagnostic guidelines compiling insulin cut-offs values and dynamic testing interpretations have not been reported for this species. Objective: To evaluate resting serum insulin concentrations, the combined glucose-insulin test (CGIT) and the glucose intravenous tolerance test (IVGTT) for the diagnosis of DMS with ID suspicion. Methods: Diagnostic test comparison. Methods: Six of 80 mix-breed adult donkeys fulfilled the inclusion criteria for DMS based on history or clinical evidence ...
Dean MF, Lee YW, Dastjerdi AM, Lees P.The basal rate of in vitro proteoglycan (PG) synthesis in explants of equine articular cartilage was subject to considerable variation in animals of the same age but was greater in younger than older animals. Synthesis of PGs in explant cultures was stimulated by a synthetic link peptide, identical in sequence to the N-terminus of the link protein (LP) of PG aggregates, in a similar manner to that demonstrated previously for human articular cartilage [Biochem. Soc. Trans. 25 (1997) 427; Arthritis Rheum. 41 (1998) 157]. Stimulation occurred in tissue from animals ranging from 1 to 30 years old ...
Rahnama S, Spence R, Vathsangam N, Baskerville CL, Bailey SR, de Laat MA, Anderson ST, Pollitt CC, Sillence MN.Although it is understood that equine endocrinopathic laminitis can be triggered by high concentrations of insulin, it is unclear whether this represents a direct action on lamellar tissue via insulin receptors (InsR), an interaction with IGF-1 receptors (IGF-1R), or some other, indirect action. This uncertainty is because of the reported scarcity of InsR in lamellar tissue and the low affinity of insulin for equine IGF-1R. In the present study, the effects of insulin and IGF-1 (as a positive control) were examined using lamellar explants isolated from the hooves of healthy horses and incubate...
Moore RM, Muir WW, Cawrse M, Bertone AL, Beard WL.Twenty-four horses were randomly allocated to 3 groups. Horses were anesthetized, subjected to a ventral midline celiotomy, and the large colon was exteriorized and instrumented. Group-1 horses served as sham-operated controls. Group-2 horses were subjected to 6 hours of low-flow colonic arterial ischemia, and group-3 horses were subjected to 3 hours of ischemia and 3 hours of reperfusion. Baseline (BL) samples were collected, then low-flow ischemia was induced by reducing ventral colonic arterial blood flow to 20% of BL. All horses were monitored for 6 hours after BL data were collected. Bloo...
McDonough P, Kindig CA, Ramsel C, Poole DC, Erickson HH.In healthy man, conditions that change muscle O2 delivery affect the achievable maximum rate of O2 uptake as well as the metabolic (e.g. lactate threshold, LT) and gas exchange (e.g. gas exchange threshold, Tge) responses to incremental exercise. Inclined (I) compared to level (L) running increases locomotory muscle EMG at a given speed in the horse, indicative of elevated metabolic demand. To our knowledge, the effect of treadmill incline on VO2,max, LT and Tge has not been addressed in the exercising quadruped. We used blood sampling and breath-by-breath expired gas analysis to test the hypo...
Mancini RA, Ramanathan R.Injection-enhancement of beef with lactate improves color stability; however, the mechanism is unclear. Thus, our objectives were to assess the effects of sodium lactate on equine myoglobin redox stability in vitro. Oxymyoglobin at pH 5.6 (50mM sodium citrate) and pH 7.4 (50mM sodium phosphate) was incubated at 4°C with lactate (0, 5, 10, 100, or 200mM) and myoglobin redox form was determined using absorbance spectra. Metmyoglobin formation at pH 5.6 and 7.4 was significantly (P<0.05) decreased by lactate at concentrations of 100 and 200mM. In general, increasing lactate concentration from...
Shellow JS, Jackson SG, Baker JP, Cantor AH.Twenty mature geldings, averaging 535 kg, were used to determine the influence of dietary selenium (Se) on the blood levels of Se and Se-dependent glutathione peroxidase (SeGSH-Px) activity in the horse. Horses were randomly assigned within breed to four treatments consisting of five horses each and fed a basal diet containing .06 ppm of naturally occurring Se. Diets were supplemented with .05, .10 and .20 ppm Se, as sodium selenite. Blood was drawn for 2 wk before, and for 12 wk following, the inclusion of supplement Se in the diets. Whole blood and plasma Se concentrations and plasma SeGSH-P...
Richter MC, Bayly WM, Keegan RD, Schneider RK, Weil AB, Ragle CA.To determine the cardiovascular and respiratory effects of water immersion in horses recovering from general anesthesia. Methods: 6 healthy adult horses. Methods: Horses were anesthetized 3 times with halothane and recovered from anesthesia while positioned in lateral or sternal recumbency in a padded recovery stall or while immersed in a hydropool. Cardiovascular and pulmonary functions were monitored before and during anesthesia and during recovery until horses were standing. Measurements and calculated variables included carotid and pulmonary arterial blood pressures (ABP and PAP respective...
Oliver JW, Held JP.Thyrotropin (thyroid stimulating hormone; TSH) stimulus to thyroid cells of horses and dogs resulted in increased serum triiodothyronine (T3) concentrations that were detected earlier than those of thyroxine (T4). Doubling of the base-line T3 values in horses was detected 0.5 hours after injection of 5 IU of TSH IV, with peak response of 5 times base-line value detected 2 hours after injection. Doubling of T4 values in horses was noticed between 2 and 3 hours, with the peak response of 2.4 times base-line value at 4 hours after injection of TSH. Doubling of base-line T3 values in dogs in respo...
Hansen PJ, Asbury AC.The release of opsonins into the uterine lumen of mares susceptible or resistant to endometritis was examined after intrauterine inoculation of a filtrate of Streptococcus culture fluid or vehicle. Uterine flushings were collected at 0.5 hour before and 2, 4, 6, 8, and 24 hours after inoculation on day 2 or 3 of estrus and on day 7 or 8 after ovulation. Amounts of opsonins in flushings were quantified as the H2O2 produced by leukocytes incubated with flushings-opsonized bacteria, compared with H2O2 produced by leukocytes incubated with nonopsonized bacteria. Opsonin values in flushings increas...
Hall SE, Nixon B, Aitken RJ.Feral horses are a significant pest species in many parts of the world, contributing to land erosion, weed dispersal and the loss of native flora and fauna. There is an urgent need to modify feral horse management strategies to achieve public acceptance and long-term population control. One way to achieve this is by using non-surgical methods of sterilisation, which are suitable in the context of this mobile and long-lived species. In this review we consider the benefits of implementing novel mechanisms designed to elicit a state of permanent sterility (including redox cycling to generate oxid...
Todhunter RJ, Fubini SL, Wootton JA, Lust G.The effect of different doses of methylprednisolone acetate (MPA) on proteoglycan and collagen metabolism of articular cartilage from normal equine joints was tested in vitro. Methods: Cultured explants were treated with 0, 0.0004, 0.004, 0.04, 0.4 and 4.0 mg/ml (approximately 10(-6)-10(-2) M) MPA for 72 h. Proteoglycan synthesis was measured by incorporation of sodium [35S]sulfate into proteoglycans and proteoglycan degradation was measured by release of total and radiolabeled proteoglycan into the culture media. The size of the proteoglycans was assessed with size exclusion chromatography un...
Turner DD, Garcia MC, Miller KF, Holtan DW, Ginther OJ.The influence of the ovaries and presence of a foal on periparturient concentrations of FSH and LH were studied in 19 Pony mares. In intact and ovariectomized mares, mean concentrations of FSH fluctuated between 1.1and 9.9 ng/ml on Days -14 to-1 before parturition (Day 0). A surge of FSH occurred in all mares in association with parturition. From Days 1 to 10, the high levels of FSH gradually decreased in the intact group to the minimal concentrations that occur during oestrus, but remained elevated in the ovariectomized mares. There were no significant pre-partum changes in LH in either type ...
Alling CR, Cremer J, Liu CC, Lewin AC, Camacho-Luna P, Carter RT.To evaluate changes in intraocular pressure (IOP) with variable head position in healthy, anesthetized horses in hoisted inversion and to assess the influence of various cofactors (age, sex, body weight, body condition score, and neck length) on IOP changes during hoisting. Methods: Seventeen healthy adult horses without significant ocular abnormalities. Methods: Subjects were administered intravenous xylazine/butorphanol premedication and ketamine/midazolam induction with xylazine/ketamine boluses for anesthetic maintenance. While hoisted, IOP was measured in triplicate for each eye via rebou...
Weiss DJ, Richwagen K, Evanson OA.To evaluate the contribution of hematocrit and RBC deformability to pulmonary vascular pressures of racehorses. Methods: Pony lungs were isolated and right and left lungs were perfused separately with blood. The effects of changing hematocrit and of pentoxifylline treatment were evaluated. Methods: 11 healthy mixed-breed ponies. Methods: Ponies were anesthesized, blood was collected, and lungs were removed and perfused with blood at constant flow rate. Results: Increasing the hematocrit from 35% to 65% resulted in increases in pulmonary arterial pressure (53%, 45%), capillary shear stress (45%...
Sinnemaa L, Järvimaa T, Lehmonen N, Mäkelä O, Reilas T, Sankari S, Katila T.The effect of artificial insemination (AI) volume on uterine contractility and inflammation and on elimination of semen in the reproductive tract of mares was examined for 4 h after AI using two methods, scintigraphy and ultrasonography. The same doses were used in both methods: 2 and 100 ml of skim milk-extended frozen semen. In the scintigraphic study, the number of reproductively normal mares was four per group and in the ultrasonographic study five per group. For scintigraphy, the semen was radiolabelled with technetium-99m. The static scintigrams were acquired immediately before and 30, 6...
Manso Filho HC, McKeever KH, Gordon ME, Manso HE, Lagakos WS, Wu G, Watford M.Glutamine is concentrated within skeletal muscle, where it has been proposed to play a regulatory role in maintaining protein homeostasis. The work presented here addressed the hypothesis that glutamine would be the most abundant free alpha-AA in plasma and skeletal muscle in the foal during the first year of life. Glycine, however, was the most abundant free alpha-AA in plasma at birth and between 3 and 12 mo of age. The concentration of glutamine, the second most abundant AA at birth, increased through the first 7 d (P < 0.05) and then returned to values similar to those at birth. This re...
Herholz C, Phillip M, Straub R, Ueltschi G, Busato A.The elimination of carbon dioxide from the lung can be used to monitor ventilation and perfusion, and 99mtechnetium-diethylenetriaminepentaacetate (99mTc-DTPA) clearance is a highly sensitive index of alveolar epithelial integrity, which is a presupposition for effective gas exchange. The aim of this study was to determine whether a correlation exists between indices of lung function derived from the single breath diagram for CO2, and 99mTc-DTPA clearance in horses with chronic obstructive pulmonary disease. The rate of 99mTc-DTPA elimination was negatively and substantially correlated with th...
Davern AJ, Peloso JG, Hawkins JF, Moore GE, Morehead JP.OBJECTIVE To evaluate 2- and 3-year-old and career race performance of Thoroughbred racehorse prospects with and without osteochondral fragmentation of the accessory carpal bone (ACB) identified on yearling presale radiographs. DESIGN Retrospective, matched cohort study. ANIMALS 47 nonlame Thoroughbreds with (exposed cohort) and 94 nonlame Thoroughbreds without (unexposed cohort) osteochondral fragmentation of ACB facture identified on yearling sales repository radiographs. PROCEDURES Repository radiographic interpretation reports for September yearling sales of a large Kentucky auction house ...
Tate LP, Blikslager AT, Papich MG.The objective was to develop a protocol whereby 808-nm diode laser irradiation combined with intravenous (IV) indocyanine green (ICG) could be used in non-contact mode with equal surgical efficacy to the Nd:YAG on equine tissues. Background: The 808-nm diode laser, delivering 20-40 W of power, has been produced for veterinary medical applications. This laser's power output is less than that of most neodymium:yttrium-aluminum-garnet (Nd:YAG) lasers. ICG is absorbed at a wavelength of 810 nm, which when concentrated in tissue should be an excellent absorber for the energy produced by the 808-nm ...
