Temperature regulation in horses involves physiological processes that maintain the animal's core body temperature within a narrow, optimal range despite external environmental changes. Horses, being homeothermic animals, rely on mechanisms such as sweating, respiration, and blood flow adjustments to dissipate excess heat or conserve warmth. These thermoregulatory processes are influenced by factors such as exercise, humidity, and ambient temperature. Variations in temperature can affect a horse's performance, health, and overall well-being. This page aggregates peer-reviewed research studies and scholarly articles that explore the mechanisms, effects, and implications of temperature regulation in equine physiology.
Hanzawa K, Kai M, Hiraga A, Watanabe S.We examined the relationship in horses between osmotic fragility of erythrocytes (OFE) measured as the red cell haemolysis rates (HLR) in 0.56% NaCl and certain physiological characters. Animals were exercised on a treadmill: warmed up at 30% VO2max for 5 min or at 105% VO2max for 1 min, given an exercise test at 80 or 105% VO2max until fatigued, and then cooled down. The pH and temperature of the blood had a significant correlation for the HLR: r = 0.93 and 0.92 (P < 0.01) on arterial and mixed venous blood, respectively. In multiple regression analysis, heart rate and packed cell volume s...
Kohn CW, Hinchcliff KW, McKeever KH.Six healthy Thoroughbred mares were trained to run on a high-speed treadmill and were conditioned for approximately 5 weeks. Each horse performed 6 identical standardised exercise tests (SET) 5 to 7 days apart. Each SET was performed under different ambient laboratory conditions: low temperature/low humidity (LL) 20.2 degrees +/- 0.6 degree C, 53.6 +/- 4.1%; low temperature/high humidity (LH) 19.7 +/- 0.6 degrees C, 86.7 +/- 4.2%; medium temperature/low humidity (ML) 24.6 +/- 0.2 degrees C, 58.7 +/- 3.7%; medium temperature/high humidity (MH) 24.7 +/- 0.3 degrees C, 87.5 +/- 1.4%; high tempera...
Marlin DJ, Schroter RC, Scott CM, White S, Nyrop KA, Maykuth PL, Harris PA.Anhidrosis has been recognised for over half a century, but despite some excellent epidemiological studies, there has been little progress in understanding the aetiology of the condition. Using a modified ventilated capsule, we obtained dynamic, quantitative data on sweating responses in anhidrotic horses and normal sweating controls from the same environment. Ten horses with current seasonal anhidrosis and 10 matched normal sweating controls were selected. Each horse was given two 10 min infusions of 1 and 2 micrograms/kg/min adrenaline, separated by at least 6 h. Sweating responses and skin ...
Marr CM, Bright JM, Marlin DJ, Harris PA, Roberts CA.We hypothesised that exercise in a hot and humid environment would affect echocardiographic indices of cardiac dimensions and function more than exercise in a cool environment. M-mode echocardiograms were obtained in 5 clinically normal horses before, and at 0, 10, 30 and 60 min after a treadmill exercise test. The test was performed in a controlled environment at 20 degrees C/40% relative humidity (RH) and again at 30 degrees C/80% RH. All the horses completed the exercise test in cool conditions, but only one horse completed the exercise test in the hot/humid environment. The relaxation time...
Scott CM, Marlin DJ, Schroter RC.Previously we have observed a decline in sweating rate (SR) during high intensity exercise in an incremental test protocol. In man, the sweating sensitivity (SR/degree C) has been shown to vary with exercise intensity. The aim of the present study was to determine if thermoregulatory responses in the horse, a prolific sweater with a high rate of metabolic heat production, were modified by exercise intensity. The effect of 3 separate exercise intensities (50 (S), 70 (M) and 90% (F) VO2peak on neck (SRN) and gluteal sweating rate (SRG), pulmonary artery (TPA), rectal (TREC) and skin temperatures...
Daels PF, Fatone S, Hansen BS, Concannon PW.The effect of the dopamine antagonist sulpiride on FSH secretion and onset of reproductive activity in anoestrous mares under different environmental conditions was investigated. In Expt 1, sulpiride (0.5 mg (-)-sulpiride kg(-1) twice a day) had no affect on FSH pulse frequency, mean FSH concentration, basal FSH concentration or FSH pulse amplitude in anoestrous mares. These data do not support the hypothesis that dopamine inhibits reproductive activity by suppressing GnRH secretion, as it does in other species. In Expt 2, the interval to first ovulation (14.8 +/- 1.9 days; range 12-22 days) i...
Brendemuehl JP, Cross DL.The aim of the present study was to determine the effect of prolonged administration of the dopamine antagonist domperidone on follicular development, ovulation and endocrine profiles in anoestrous mares. Anoestrous mares (n=16) were maintained under natural photoperiod and ambient temperature. Eight of the mares were treated with domperidone each day from 15 January until the first ovulation of the year. The mean number and size of follicles > or =20 mm in diameter were significantly greater in domperidone-treated mares than in control mares by day 14 of treatment. The day of first ovulati...
McCutcheon LJ, Geor RJ, Ecker GL, Lindinger MI.This study examined sweating responses in six exercise-trained horses during 21 consecutive days (4 h/day) of exposure to, and daily exercise in, hot humid conditions (32-34 degrees C, 80-85% relative humidity). On days 0, 3, 7, 14, and 21, horses completed a standardized exercise test on a treadmill (6 degrees incline) at a speed eliciting 50% of maximal O(2) uptake until a pulmonary artery temperature of 41.5 degrees C was attained. Sweat was collected at rest, every 5 min during exercise, and during 1 h of standing recovery for measurement of ion composition (Na(+), K(+), and Cl(-)) and swe...
Ribeiro MF, Costa JO, Guimarães AM.The prevalence of Babesia equi in two climatic regions of Minas Gerais state was determined using the indirect fluorescent antibody test (IFAT) with blood samples obtained from horses in two slaughterhouses. Of 399 samples, 241 (60.4%) showed a positive reaction. Anti-B. equi antibody was detected in every county studied, the prevalence being 59.7% for horses in the area where the temperature rises above 18 degrees C in winter and 61.4% in the area where it remains below 18 degrees C, indicating that climatic variation has no substantial effect on the prevalence of the infection in Brazil. Blo...
Toews AR, Bailey JV, Townsend HG, Barber SM.To examine the amount of heat generated in equine cortical bone by a 6.2-mm drill, using low- and high-speed and controlled feed rate drilling. Methods: 10 metacarpal bones harvested from five 2-year-old draft-type horses. Methods: Drilling on metacarpal bones was done using a machine shop mill with which the feed rate and drill speed could be precisely controlled. Bones were drilled, using 6 combinations of feed rate (1, 2, and 3 mm advance/s) and drill speed (317 and 1,242 revolutions/min [rpm], with maximal temperatures recorded by thermocouples placed 1, 1.5, and 2 mm from the drill. Maxim...
Gottlieb-Vedi M, Essén-Gustavsson B, Thornell LE, Lindholm A.The aim of this study was to determine whether the metabolic response and ultrastructure of muscle differed when horses performed intense exercise at different ambient temperatures. Four Standardbred geldings performed treadmill exercise, including an intensive trot of 2600 m on two different occasions, either at a high ambient temperature of 35 degrees C or at a temperature of 20 degrees C. The horses had a warm-up period of 23.5 min of submaximal exercise, followed by 2 h of box rest before the intensive exercise. Muscle biopsy data of adenine nucleotides, creatine phosphate, lactate and gly...
House JK, Mainar-Jaime RC, Smith BP, House AM, Kamiya DY.To identify risk factors for nosocomial Salmonella infections among hospitalized horses. Methods: Longitudinal study. Methods: 1,583 horses hospitalized in an intensive care unit between January 1992 and June 1996. Methods: Survivor functions were used to estimate time to shedding salmonellae for various Salmonella serotypes. Survival analysis was then used to determine how variables associated with patient management, environmental conditions, hospital conditions, and other disease processes affected the risk of nosocomial Salmonella infection. Results: 78 horses shed Salmonella organisms: 35...
Tomasic M, Nann LE.To examine temporal patterns of rectal, nasal, groin, and skin temperatures measured in adult horses undergoing general anesthesia and to determine accuracy and precision of temperatures at these sites, compared with core temperature. Methods: 5 healthy adult horses. Methods: Induction, maintenance of, and recovery from general anesthesia were performed in an air-conditioned surgical suite. Room temperature and relative humidity were approximately 21 C and 40%, respectively. Anesthesia was maintained for 2.5 hours, and body temperatures were measured and recorded every 5 minutes. Mean values w...
Tomasic M.To examine temporal patterns of core body temperatures in adult horses during general anesthesia and to determine the efficacy of forced-air warming blankets in attenuating decreases in core body temperatures. Methods: 5 clinically normal adult horses. Methods: Horses were assigned to each of 2 trials, warmer and no-warmer, in a randomized crossover design. Horses were instrumented with a thermistor-tipped pulmonary arterial catheter to measure core body temperature. Induction and maintenance of and recovery from general anesthesia were performed in an air-conditioned surgical suite where room...
Lindinger MI.This paper reviews the limits to exercise imposed by increases in ambient, hypothalamic, and contracting skeletal muscle temperature in humans and horses. Like humans, horses frequently compete in hot environments, yet their high mass-specific rate of heat production and low mass-specific surface area for heat dissipation places them at a great disadvantage compared to humans. Exercise in hot conditions increases the rate of body heat storage and reduces the time required to reach a critical hypothalamic temperature that results in voluntary fatigue. This critical temperature appears to be ass...
Pollitt CC, Davies CT.The effect of alimentary carbohydrate overload on hoof temperature was investigated to determine the state of the sublamellar vasculature preceding the onset of equine laminitis. Hoof, core and ambient temperatures and heart rate were logged continuously in 21 mature Standardbred horses kept in an environmental chamber set at 10 degrees C. Recording hoof temperature was a successful, noninvasive, method to measure indirectly, shifts in digital blood flow against a background of cold induced, physiological, vasoconstriction. High hoof temperatures were assumed to indicate digital vasodilation a...
Ebert DW, Bertone AL, Roberts C.To determine whether irradiation with a low-intensity diode laser, which produces radiation at a wavelength of 810 nm, will induce nonthermal enhancement of chondrocyte metabolism. Methods: 144 grossly normal articular cartilage explants aseptically harvested from the femoral condyles of 6 adult horses. Methods: Treated cartilage explants were irradiated with a diode laser at 1 of 7 fluence levels that ranged from 8 to 1,600 J/cm2. Explants were incubated for 24 or 72 hours, labeled for 24 hours with [35S]Na2SO4, and assayed for newly synthesized sulfated glycosaminoglycan (GAG; measured incor...
Vanin AF, Serezhenkov VA, Mikoyan VD, Genkin MV.The parameters of EPR signal from dinitrosyl-iron complexes (DNIC) with bovine serum albumin (BSA), horse hemoglobin (Hb), and apometallothionein (apo-Mt) of horse kidney incorporating one (BSA, Hb) or two thiol-containing ligands (apo-Mt) were compared. The EPR signal from DNIC-BSA was characterized by the rhombic symmetry of g tensor at room temperature of signal recording (ambient temperature) or at 77K in the solution frozen in the presence of glycerol. In freezing of the solution in the absence of glycerin, under the exposure of DNIC-BSA to negatively charged sodium dodecyl sulfate (SDS) ...
Meskers SC, Dekkers HP.For mitochondrial ferricytochrome c from horse, cow and tuna and for bacterial cytochrome c-550 from Paracoccus versutus, the pressure and temperature dependence of their quenching of racemic Tb(DPA)3(3-) and Eu(DPA)3(3-) (DPA = pyridine-2,6-dicarboxylate) luminescence in aqueous solution is investigated. Of these energy transfer reactions the activation volumes (delta V#) and energies (Ea) are determined for the ranges P = 0-3 kbar and T = 15-40 degrees C. For the lambda enantiomers of Tb(DPA)3(3-) and Eu(DPA)3(3-), delta V# and Ea are almost the same for all proteins: 0.4 < or = delta V# < o...
Taylor LE, Kronfeld DS, Ferrante PL, Wilson JA, Tiegs W.Rectal temperature (Tre) is often used to adjust measurements of blood gases, but these adjusted measurements may not approximate temperatures during intense exercise at main sites of gas exchange: muscle and lung. To evaluate differences in blood gases between sites, temperatures (T) were measured with thermocouples in the rectum (re), in mixed venous blood (v), in gluteal muscle (mu), and on the skin (sk) in seven Arabian horses as they underwent an incremental exercise test on a treadmill. Blood samples were drawn from the carotid artery and pulmonary artery (mixed venous) 30 s before each ...
Looney AL, Ludders J, Erb HN, Gleed R, Moon P.To compare, for blood samples from dogs and horses, blood electrolyte concentrations, blood gas partial pressures, and Hct obtained using a handheld analyzer with those obtained using a standard chemistry analyzer and to compare results obtained with the handheld analyzer using warm versus cold test cartridges. Methods: Case series with analysis of split samples. Methods: Blood samples from 22 dogs and 17 horses. Methods: Sodium, potassium, ionized calcium, bicarbonate, and total CO2 concentrations, pH, PO2, PCO2, base excess, and Hct were determined by use of a handheld analyzer and test cart...
van den Berg JS, Guthrie AJ, Meintjes RA, Nurton JP, Adamson DA, Travers CW, Lund RJ, Mostert HJ.The objectives of this trial were to measure the water and electrolyte intake and loss, of horses during road transportation in relatively hot environmental conditions. Six mature, Thoroughbred horses in full training were used in a balanced crossover design. The horses were conditioned on a treadmill for 6 weeks before the start of the trial in order to simulate the type of horse that is transported most often over long distances in South Africa. The horses were assigned randomly to one of 2 treatment groups. On a particular day 3 horses were transported, while the other horses served as cont...
Marlin DJ.A number of studies have clearly shown that the ability of both man and horses to perform a standardised exercise test in hot humid conditions is reduced compared to that in hot dry or cool conditions (see reviews by Maughan and Lindinger, 1995; Lindinger and Marlin, 1995). In man it is clear that a period of acclimation or acclimatisation is beneficial. A search of the literature prior to 1995 indicates no published information relating to the acclimation or acclimatisation of the horse to hot or hot humid environmental conditions. Concerns for the appropriate preparation for and welfare of h...
Bhuyan AK, Udgaonkar JB.The unfolding kinetics of horse cytochrome c in the oxidized state has been studied at 10, 22, and 34 degreesC as a function of guanidine hydrochloride (GdnHCl) concentration. Rapid (millisecond) measurements of far-UV circular dichroism (CD) as well as fluorescence quenching due to tryptophan to heme excitation energy transfer have been used to monitor the unfolding process. At 10 degreesC, the decrease in far-UV CD signal that accompanies unfolding occurs in two phases. The unobservable burst phase is complete within 4 ms, while the slower phase occurs over tens to hundreds of milliseconds. ...
Baptiste KE.The equine guttural pouch is a large, air-filled diverticulum of the auditory tube whose function is not clear. Since the horse does not possess a known, well-developed brain-cooling mechanism that could satisfy cerebral thermoregulatory demands, an hypothesis is proposed that respiratory air enters the guttural pouches, when needed, to ventilate and cool the internal carotid arteries (ICA). Experiments were initially carried out on nine cadavers, where blood flow was mimicked with warmed saline propelled by peristaltic pumps. Subsequent experiments were conducted on an anaesthetized horse whe...
Guthrie AJ, Lund RJ.Metabolic HP is extremely high during exercise in horses. Thermoregulation in horses is primarily dependent on evaporative heat loss from sweating in particular. Under thermoneutral conditions, these mechanisms are sufficient to allow horses to perform high-intensity exercise for long periods. Under thermally stressful conditions, particularly in high ambient humidity, the efficiency of evaporative heat loss mechanisms is compromised and may result in horses developing hyperthermia. Early recognition and vigorous treatment are essential to limit the consequences of heat stress in horses. Metic...
Geor RJ, McCutcheon LJ.The large metabolic heat load generated as a consequence of muscular work requires activation of thermoregulatory mechanisms in order to prevent an excessive and potentially dangerous rise in body temperature during exercise. Although the horse has highly efficient heat dissipatory mechanisms, there are a number of circumstances in which the thermoregulatory system may be overwhelmed, resulting in the development of critical hyperthermia. The risk for development of life-threatening hyperthermia is greatest when (1) the horse is inadequately conditioned for the required level of physical perfo...
Marlin DJ, Scott CM, Roberts CA, Casas I, Holah G, Schroter RC.Whereas the efficacy of cold water cooling of horses has been demonstrated by several studies, the dynamics of temperature changes within and between compartments (primarily muscle, blood [core], skin and deep core [rectal]) have not been investigated. Changes in body temperature associated with cold water cooling were investigated in the hyperthermic horse. Muscle (TMU), pulmonary artery (TPA), rectal (TREC), tail-skin (TTSK) and coat surface (TCOAT) temperatures, were monitored continuously in 5 Thoroughbred horses during and after exercise in hot humid (30 degrees C and 80% RH) conditions o...
Kubota T, Inaba Y, Uwatoko K, Akashi H, Fukunaga Y.Equine arteritis virus (EAV) grown on RK13 cell cultures was tested for hemagglutination (HA) with erythrocytes from a variety of species at 4 degrees C, room temperature and 37 degrees C. HA was observed at all temperatures with erythrocytes from mouse and chicken but not with those of cattle, horse, rabbit, guinea pig, mongolian gerbil, goose or chick embryo. Chickens showed an individual variation in agglutinability of their erythrocytes, requiring selection of birds to obtain erythrocytes for HA. The HA activity was enhanced by treatment of virus materials with Tween 80 followed by treatme...
Webbon PM.Skin temperature measurements were recorded of the legs of 13 racehorses between 2 and 5 years old. The normal limb temperature patterns are described. In over 90 per cent of the normal horses the difference between contralateral limbs was less than 1 degree C, but in the remainder differences of up to 8 degree C were recorded due to the excessive cooling of one limb. One horse had a constant temperature elevation of one foreleg, but it remained in training for 7 weeks without any obvious ill effects. Because of the small numbers of horses in the survey and their freedom from tendon injuries i...
Edwards S, Clode AB, Gilger BC.This retrospective case series evaluates husbandry and environmental conditions in relation to eosinophilic keratitis in horses. While no associations were found between disease and husbandry practices or specific environmental factors such as humidity or temperature, an increased prevalence of presentation in summer months was identified in this population of horses.
Reinprecht B, Hackl S, Reisinger R, Zickl M, Spona J, Stanek C, Zentek J.The objective of this study was to investigate some metabolic and clinical effects of feed deprivation in horses that were submitted for orthopaedic surgery. The effects of preoperative feed restriction were investigated in 20 horses submitted for elective orthopaedic surgery. The patients were fasted from 12 hours before until 4 hours after surgery. Serum free amino acids, glucose,free fatty acids (FFA), white blood cell counts, creatine kinase (CK) and aspartate aminotransferase (AST) were determined 24 hours before surgery, 2 hours after the end of anaesthesia and 24 and 72 hours after surg...
Szenci O, Németh F, Stollár Z, Brydl E.Stability of ionized calcium (Ca2+) concentrations and pH values in equine venous samples (n = 12 in each group) stored at 4 C for 3, 9, 24, and 48 hours (blood, plasma, and serum) or for 240 hours (plasma and serum), and at -20 C for 240 hours (plasma and serum), was studied. Storage of equine blood, plasma, and serum samples at 4 C for up to 48 hours and of serum samples at 4 C for up to 240 hours, despite appreciable pH changes, was associated with < 1.5% change in blood, plasma, and serum Ca2+ concentrations. Therefore, Ca2+ concentration in equine blood, plasma, and serum samples store...
Kaminski RP, Forster HV, Bisgard GE, Pan LG, Dorsey SM, Barber BJ.The purpose of this study was to determine if the changes in O2 consumption (VO2) during CO2 inhalation could in part be due to stimulation of thermogenesis for homeothermy. Twelve ponies were exposed for 30-min periods to inspired CO2 (PIco2) levels of less than 0.7, 14, 28, and 42 Torr during the winter at 5 (neutral) and 23 degrees C ambient temperatures (TA) and during the summer at 21 (neutral TA), 30, and 12 degrees C. Elevating TA in both seasons resulted in an increased pulmonary ventilation (VE) and breathing frequency (f) (P less than 0.01) but no significant increase in VO2 (P great...
Foglesong MA.The antibiotic activity of cephalothin, cephaloridine, cephalexin, cephaloglycin, cefazolin, and cefamandole was determined after storage for up to 30 days in horse serum at -10 and 4 degrees C. Cephalothin, cefamandole, cefazolin, and cephalexin were stable for at least 30 days at -10 degrees C, whereas cephaloridine lost 29% of its initial activity and cephaloglycin lost more than 50%. Cefamandole, cefazolin, and cephalexin could only be stored for 3 days at 4 degrees C without significant loss in activity, whereas cephalothin, cephaloridine, and cephaloglycin could be stored for only 1 day....
Haluska GJ, Wilkins K.Rectal temperature was recorded from 22 mares at 0700, 1500 and 2300 h daily for seven days pre-partum and one day post partum. A circadian variation in rectal temperature was present with the lowest temperature recorded at 0700 h. Because of this, the mares were divided into three groups based on time of parturition; those foaling between 0700 and 1500 h (n = 2); between 1500 and 2300 h (n = 13); and between 2300 and 0700 h (n = 7). On the day prior to delivery (Day -1) the circadian pattern was absent because the nocturnal increase did not occur. A significant decrease in temperature was rec...
Marlin DJ.A number of studies have clearly shown that the ability of both man and horses to perform a standardised exercise test in hot humid conditions is reduced compared to that in hot dry or cool conditions (see reviews by Maughan and Lindinger, 1995; Lindinger and Marlin, 1995). In man it is clear that a period of acclimation or acclimatisation is beneficial. A search of the literature prior to 1995 indicates no published information relating to the acclimation or acclimatisation of the horse to hot or hot humid environmental conditions. Concerns for the appropriate preparation for and welfare of h...
Jacob RJ, Price R, Bouchey D, Davis T, Borchelt J.This article reviews the findings on temperature sensitivity of equine herpesvirus isolates with an emphasis on equine herpesvirus 3, etiological agent of equine coital exanthema. The hypothesis is presented that the relative apathogenic nature of this herpesvirus may be an indirect result of its inability to synthesize and/or process glycoproteins needed by the virus to produce infectious virions at the normal body temperature of its natural host. It is suggested that equine herpesvirus 3 is the more evolved and naturally attenuated member of the equine herpesviruses.
Wheeler SJ.Sensory nerve conduction velocity was measured in the lateral palmar nerve of 8 horses. The limb temperature was manipulated by external means and monitored. Alterations in the nerve conduction velocity related to limb temperature variation were identified at both increased and decreased temperatures. These were quantified and a mean value of 2.15 +/- 0.2 m/s/degree Celsius was determined. The effect of altered limb temperature should be considered in nerve conduction velocity determinations.
Gospodarek E.Direct and intermediate hemolytic activity of 526 strains of Acinetobacter was investigated. Their ability to produce lipase and lecithinase was also studied. Measurements were performed parallely on human, horse, sheep and bovine erythrocytes. Direct hemolytic activity was exhibited by 16% of tested strains (17 out of 24 strains of A. haemolyticus). Human, sheep and bovine erythrocytes were useful for testing the hemolytic activity of Acinetobacter. The hemolysis was occurring faster and was visible more frequently during incubation at 37 degrees C. Indirect hemolytic activity was observed in...
Väihkönen LK, Hyyppä S, Reeta Pösö A.In horses, both the post exercise distribution of lactate between plasma and red blood cells (RBC) and the activity of lactate transporters on the RBC membrane vary widely between individuals. In this study, we investigated the effects of pH, time and temperature on lactate distribution in vitro, and compared the in vitro activity of lactate transporters with the accumulation of lactate into RBC in vivo. To accomplish this, we took venous blood samples at rest and after trotting races. The post exercise accumulation of lactate into RBC was shown to depend on the activity of lactate transporter...
Guertin JE, Losano JA, Salazar S, Callaham J, Daigneault BW.Bottlenecks to the success of equine assisted reproductive technologies (ART) include suboptimal conditions for prolonged storage of stallion sperm. Shipped stallion sperm are transported in cooling devices designed to maintain temperature for up to 48 h. Increasing the storage time of cooled semen while maintaining acceptable motility would relieve logistical ART challenges. Experiments were conducted to test the hypothesis that external regulation of shipment container temperature would prolong storage time of cooled stallion semen. Initial experiments determined the effect of pre-freezing c...
MacKechnie-Guire R, Fisher M, Mathie H, Kuczynska K, Fairfax V, Fisher D, Pfau T.Thermography is a non-invasive method for measuring surface temperatures and may be a convenient way of identifying hypo/hyperthermic areas under a saddle that may be related to saddle pressures. A thermal camera quantified minimum/maximum/mean temperatures at specific locations (left/right) of the thoracic region at three-time points: (1) baseline; (2) post lunging; (3) post ridden exercise in eight non-lame sports horses ridden by the same rider. A Pliance (Novel) pressure mat determined the mean/peak saddle pressures (kPa) in the cranial and caudal regions. General linear mixed models with ...
Cymbaluk NF, Christison GI, Leach DH.Eighteen weanling horses were assigned to two treatments: limited or ad libitum feed intake. Growth and feed utilization were evaluated over a 78-wk period. Ad libitum-fed horses gained 24% more (P less than .05) weight than limit-fed horses. Total BW was distributed into 57% fore and 43% hind weight and did not differ between groups regardless of dietary treatment or age. Net gain and ADG in wither height of ad libitum-fed horses exceeded (P less than .05) that of limit-fed horses over 78 wk. Ad libitum-fed horses consumed 19, 44 and 34% more digestible energy (DE) than indicated in 1978 NRC ...
Art T, Lekeux P.A preliminary study attempted to assess the influence of atmospheric conditions on the breathing pattern of ponies. The respiratory airflow, tidal volume, breathing frequency, minute volume, total pulmonary resistance and heart rate of five ponies (257 +/- 9 kg and three to five years old) were measured by a standardised procedure. Data were collected at rest, during a nine minute period of treadmill exercise and during a five minute recovery period. The ambient temperature (degrees C) and relative humidity (%) were recorded at the time of each investigation and the respiratory parameters were...
Bocian K, Strzelec K, Janczarek I, Jabłecki Z, Kolstrung R.This paper analyzes changes in the length of coat on selected body areas in horses and ponies kept under different husbandry (stable) conditions during the winter-spring period. The study included 12 Małpolski geldings and 12 geldings of Felin ponies aged 10-15 years. Horses were kept in two stables (six horses and six ponies in each stable). The type of performance, husbandry conditions and feeding of the studied animals were comparable. As of December 1, samples of hair coat from the scapula, sternum, back and abdomen areas of both body sides were collected seven times. The lengths of 20 ra...
Jenny JCA, Hopster K, Hurcombe SD.To compare the accuracy and precision of cardiac output (CO) measurements derived from 4 thermodilution protocols that used different injectate temperatures and volumes in healthy adult horses. Methods: 8 healthy adult horses. Methods: Horses were anesthetized and instrumented with Swan-Ganz catheters. The CO was derived from each of 4 thermodilution protocols (IV injection of physiologic saline [0.9% NaCl] solution chilled to < 5 °C at volumes of 1 mL/15 kg of body weight [protocol A; control], 1 mL/25 kg [protocol B], and 1 mL/35 kg [protocol C] or maintained at 17 °C at a volume of 1 m...
Martin EM, Duck FA, Winlove CP.We have previously shown that MHz frequency ultrasound causes contraction of the carotid artery in vitro. We now extend this investigation to equine mesenteric arteries and investigate the cellular mechanisms. In vitro exposure of the large lateral cecal mesenteric artery to 4-min periods of 3.2 MHz continuous wave ultrasound at acoustic powers up to 145 mW induced reversible repeatable contraction. The magnitude of the response was linearly dependent on acoustic power and, at 145 mW, the mean increase in wall stress was 0.020 ± 0.017 mN/mm(2) (n = 34). These results are consistent with our p...
Tomasic M, Nann LE.To examine temporal patterns of rectal, nasal, groin, and skin temperatures measured in adult horses undergoing general anesthesia and to determine accuracy and precision of temperatures at these sites, compared with core temperature. Methods: 5 healthy adult horses. Methods: Induction, maintenance of, and recovery from general anesthesia were performed in an air-conditioned surgical suite. Room temperature and relative humidity were approximately 21 C and 40%, respectively. Anesthesia was maintained for 2.5 hours, and body temperatures were measured and recorded every 5 minutes. Mean values w...
Doherty TJ, Geiser DR, Rohrbach BW.The effect of i.v. acepromazine (0.05 mg/kg bwt), butorphanol (0.05 mg/kg bwt) and a combination of acepromazine and butorphanol on halothane minimum alveolar concentration (MAC) was determined in 7 mixed-breed ponies. Ventilation was controlled, and blood pressure and temperature were maintained within normal limits. Following the determination of baseline MAC, treatments were administered to each pony in a random manner. The control treatment was normal saline. The baseline halothane dMAC for the control group was 0.91 +/- 0.04%, and no significant change occurred after saline administration...
Merlin A, Ravinet N, Sévin C, Bernez-Romand M, Petry S, Delerue M, Briot L, Chauvin A, Tapprest J, Hébert L.Cyathostomins are considered as the most prevalent and pathogenic parasites of grazing horses. The development on pastures of the free-living stages of these gastrointestinal worms is particularly influenced by outdoor temperature. Understanding the bionomics of free-living stages is an important prerequisite to implement mathematical models designed to assess the parasitic risk for grazing equids. The aim of this study was to assess the effect of 3 constant temperatures under laboratory conditions (10 ± 1 °C, 23 ± 2 °C, 30 ± 2 °C) and one fluctuating temperature under outdoor c...
Sahu SP, Dardiri AH, Rommel FA, Pierson RE.Survival of bacteria that cause contagious equine metritis (CEM) was evaluated in Amies modified transport (AMT) medium, in AMT medium with charcoal, and in Stuart transport medium at 37, 22, 4, and -70 C. The CEM bacteria suspended in transport media survived at 22, 4, and -70 C for longer periods in AMT medium with charcoal than they did in AMT and Stuart transport media. In 1 day, the number of bacteria in exudate stored in the absence of any transport medium decreased 15-fold at 22 C and twofold at 4 C. The CEM bacteria were isolated from exudate on cotton-tipped swabs from all three trans...
Ebert DW, Bertone AL, Roberts C.To determine whether irradiation with a low-intensity diode laser, which produces radiation at a wavelength of 810 nm, will induce nonthermal enhancement of chondrocyte metabolism. Methods: 144 grossly normal articular cartilage explants aseptically harvested from the femoral condyles of 6 adult horses. Methods: Treated cartilage explants were irradiated with a diode laser at 1 of 7 fluence levels that ranged from 8 to 1,600 J/cm2. Explants were incubated for 24 or 72 hours, labeled for 24 hours with [35S]Na2SO4, and assayed for newly synthesized sulfated glycosaminoglycan (GAG; measured incor...
Geiser DR, Walker RD.The pathophysiology and histopathology of thermal burns in large animals is very similar to that in humans. Burns are classified as first degree, superficial and deep second degree, third degree, and fourth degree, depending upon the depth of thermal injury. Most severe burns will produce a local and a systemic response--both of which must be properly treated to increase the patient's chances for survival. The systemic response is mainly characterized by hypovolemia, fluid and electrolyte loss, protein loss, pulmonary edema, increased caloric requirements, and depressed immune responses. The l...
Hernández-Avilés C, Ramírez-Agámez L, Love CC, Friedrich M, Pearson M, Kelley DE, Beckham AMN, Teague SR, LaCaze KA, Brinsko SP, Varner DD.Under in vitro conditions, stallion sperm might preferentially use energy substrates that primarily undergo mitochondrial metabolism. The present study sought to determine the effects of glucose, pyruvate, lactate, or their combinations on the quality of stallion sperm subjected to cooled storage at different temperatures, when using a skim milk-based semen extender. In Experiment 1, no substrate (Control), glucose (40 mM; Glu-40), pyruvate (2 mM, 19.8 mM; Pyr-2, Pyr-19), lactate (2 mM, 19.8 mM; Lac-2, Lac-19, respectively), or their combinations (G/P/L-2 or G/P/L-19, respectively) were ...
Allen ML, Baker GJ, Freeman DE, Holmes KR, Marretta SM, Scoggins RD, Constable P.To measure the amount of heat generated during 3 methods of equine dental reduction with power instruments. Methods: In vitro study. Methods: 30 premolar and molar teeth removed from mandibles of 8 equine heads collected at an abbatoir. Methods: 38-gauge copper-constantan thermocouples were inserted into the lingual side of each tooth 15 mm (proximal) and 25 mm (distal) from the occlusal surface, at a depth of 5 mm, which placed the tip close to the pulp chamber. Group-NC1 (n = 10) teeth were ground for 1 minute without coolant, group-NC2 (10) teeth were ground for 2 minutes without coolant, a...
Noël PG, Couëtil L, Constable PD.Plastic heparinised vacutainer tubes are used for blood gas analysis in horses. This collection method may not be ideal because influx of atmospheric O(2) through the permeable plastic wall of the vacutainer tube and loss of CO(2) into the gas phase above the blood sample should increase blood PO(2) and decrease PCO(2), respectively. Objective: To determine the effects of collecting blood into plastic vacutainer tubes and storage conditions on blood gas analysis values. Methods: Blood was obtained from 6 healthy horses and tonometered at 37 °C with 12% O(2) and 5% CO(2). Three ml aliquots of ...
