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.
Prutton JS, Kass PH, Watson JL, Pusterla N.The stability of equine adrenocorticotrophic hormone (ACTH) in blood samples is not fully known. The study objectives were to determine ACTH stability (1) in whole blood and plasma over 72 h at either 4 or 21 °C, and (2) in plasma frozen at either -20 or -80 °C over 30 days. Nine horses were sampled and ACTH concentration were measured after storage as whole blood or plasma, at 4, 21, -20 and -80 °C for up to 30 days. The ACTH concentration was significantly reduced at 24 h but remained stable when plasma was frozen at -20 and -80 °C for 30 days. Beyond 24 h, samples stored a...
van Eps AW, Orsini JA.Digital hypothermia may be effective for laminitis prophylaxis and therapy, but the efficacy of cooling methods used in clinical practice requires evaluation. Objective: To use hoof wall surface temperature (HWST) to compare several cooling methods used in clinical practice. Methods: Experimental crossover design with a minimum washout period of 72 h. Methods: Seven cooling methods (commercially available ice packs, wraps and boots) and one prototypical dry-sleeve device were applied to a single forelimb in 4 horses for 8 h, during which HWST of the cooled forelimb and the uncooled (contro...
Oldenhof H, Heutelbeck A, Blässe AK, Bollwein H, Martinsson G, Wolkers WF, Sieme H.The aim of this study was to evaluate inter-individual variability in osmotic properties of stallion spermatozoa and its correlation with cryosurvival. In addition, temperature dependency of hypo-osmotic tolerance and membrane fluidity were studied. Stallion sperm membranes exhibited good resistance towards hypotonic stress in the 15-30 °C temperature range, whereas membrane stability was found to be decreased at 4 and 37 °C. Bull spermatozoa showed greater hypo-osmotic tolerance compared with stallion spermatozoa, especially at temperatures above 30 °C, which coincided with decreased membr...
Janczarek I, Wilk I, Zalewska E, Bocian K.The aim of this paper was to select atmospheric factors and their values, which may disrupt the correct behavior and physiological condition of recreational horses. The studies were carried out from 1 July until 1 September on 16 Anglo-Arabian geldings. Each day, from 09.00 to 10.00 hours, the horses worked under saddle. The riders and the authors gave a qualitative behavioral assessment for each horse. Mood and willingness to work were evaluated. The quantitative assessment was called 'incorrect behavior of the horse while riding' (IBHR). The percentage time of duration and the number of occu...
Brinkmann L, Gerken M, Hambly C, Speakman JR, Riek A.Recent results suggest that wild Northern herbivores reduce their metabolism during times of low ambient temperature and food shortage in order to reduce their energetic needs. It is, however, not known whether domesticated animals are also able to reduce their energy expenditure. We exposed 10 Shetland pony mares to different environmental conditions (summer and winter) and to two food quantities (60% and 100% of maintenance energy requirement) during low winter temperatures to examine energetic and behavioural responses. In summer, ponies showed a considerably higher field metabolic rate (FM...
Meister U, Ohnesorge B, Körner D, Boevé MH.Sonographic ophthalmic examinations have become increasingly important in veterinary medicine. If the velocity of ultrasound in ocular tissues is known, the A-mode ultrasound method may be used to determine the axial intraocular distances, such as anterior chamber depth, lens thickness, axial length of the vitreous and axial globe length, which are required for intraocular lens (IOL) power calculations. To the authors' knowledge, the velocity of ultrasound in the ocular tissues of the horse was not previously determined. In the present study, 33 lenses, 29 samples of aqueous and 31 of vitreous...
Martino NA, Dell'Aquila ME, Filioli Uranio M, Rutigliano L, Nicassio M, Lacalandra GM, Hinrichs K.Evaluation of mitochondrial function offers an alternative to evaluate embryo development for assessment of oocyte viability, but little information is available on the relationship between mitochondrial and chromatin status in equine oocytes. We evaluated these parameters in immature equine oocytes either fixed immediately (IMM) or held overnight in an Earle's/Hank's' M199-based medium in the absence of meiotic inhibitors (EH treatment), and in mature oocytes. We hypothesized that EH holding may affect mitochondrial function and that holding temperature may affect the efficiency of meiotic su...
Gómez MD, Menéndez-Buxadera A, Valera M, Molina A.The performance results of Spanish Trotter Horses were merged with the information from the nearest official weather stations, to estimate the effects of temperature (T) on speed during the day of the race. The resulting data set included: 104 125 individual results from 7653 races with 3772 participant horses and driven by 1402 jockeys. After a classical repeatability animal model in which the effects of T were assumed null, a total of five different random regression models (RRM) with the same fixed part were applied in a parsimonious nested process in which the (co)variance components for ...
Yarnell K, Fleming J, Stratton TD, Brassington R.Infrared thermography (IRT) was used to assess surface temperature change as an indirect measure of muscle activity and exercise associated changes in blood flow in the working hind limb muscles of horses (n=7) undergoing water treadmill exercise. Three treatments were investigated including the treadmill ran dry (TD), water at the height of the proximal interphalangeal joint (PIP) and water at the height of the carpus (CP). Maximum skin surface temperature was recorded from the region of the semitendinosus muscle during exercise at each water height. There was a significant difference in surf...
Velineni S, Timoney JF.Streptococcus zooepidemicus causes opportunist respiratory and other infections in the horse. Capsule expression is highly variable and known to affect resistance to phagocytosis. Most clinical isolates producing small, dry colonies at 37°C produce mucoid colonies at temperatures below 35°C. Objective: The aim was to understand the molecular basis of increased capsule expression by equine isolates of S. zooepidemicus at temperatures lower than 35°C. Methods: Cross-sectional observational study. Methods: Capsule production by groups of equine S. zooepidemicus strains was determined at 23, ...
Edner A, Lindberg LG, Broström H, Bergh A.Static magnetic blankets are often claimed to induce increases in blood flow, reduce muscle tension and tenderness, and be beneficial in both prevention and treatment of musculoskeletal injuries in horses. However, there are no studies that confirm alleged beneficial effects of magnets on muscles of the back in healthy horses. Objective: To investigate whether static magnets sewn into a blanket affect back muscle blood flow, skin temperature, mechanical nociceptive threshold (MNT) and behaviour in healthy horses. Methods: Prospective, randomised, blinded, placebo-controlled crossover study. Me...
Grint NJ, Whay HR, Beths T, Yvorchuk K, Murrell JC.To evaluate a thermal nociceptive threshold (TNT) testing device in the donkey, and the influence of potential confounding factors on TNTs. Methods: Two groups (Group 1 and Group 2) of eight castrated male donkeys aged 4-9 years, weighing 105-170 kg. Methods: TNTs were measured by heating a thermal probe on skin until an end-point behaviour (threshold temperature) or a cut-out temperature (51 °C) was reached. The withers and the dorsal aspect of the distal limb were used as sites for TNT testing. The effects on TNT of different confounding factors: the limb tested; rate of heating; and amb...
Ellse L, Burden FA, Wall R.A longitudinal study was undertaken over a 21 months period to examine the seasonal abundance of lice infesting donkeys, the risk factors which predispose donkeys to infestation and the effectiveness of louse management. All the lice seen were Bovicola (Werneckiella) ocellatus. A strong seasonal pattern, which was correlated with mean monthly temperature, was observed with higher prevalence and intensity in the cooler, winter months (October-March). Overall infestation in these animals was over-dispersed, suggesting that some individuals are strongly predisposed to infestation. Donkey age and ...
Westermann S, Windsteig V, Schramel JP, Peham C.To determine the skin temperature of the metacarpus in horses associated with the use of bandages and tendon boots, compared with the bare limb, at rest and after 20 minutes of lunging. Methods: 10 adult horses. Methods: Skin temperature on the bare metacarpus of both forelimbs was measured at rest and after lunging. Subsequently, a bandage was applied to the left metacarpus and a tendon boot to the right metacarpus and skin temperature was measured at rest and after lunging. Skin temperature was measured with fixed sensors and thermographically. Results: Mean ± SD skin temperatures of the ba...
Nemoto M, Bannai H, Tsujimura K, Yamanaka T, Kondo T.Although many disinfectants are commercially available in the veterinary field, information on the virucidal effects of disinfectants against equine group A rotavirus (RVA) is limited. We evaluated the performance of commercially available disinfectants against equine RVA. Chlorine- and iodine-based disinfectants showed virucidal effects, but these were reduced by the presence of organic matter. Glutaraldehyde had a virucidal effect regardless of the presence of organic matter, but the effect was reduced by low temperature or short reaction time, or both. Benzalkonium chloride had the greatest...
Smith KM, Maxwell L, Gull T, Payton ME, Gilmour MA.To establish the effect of storage in a constant-rate infusion (CRI) pump on the sterility and stability of voriconazole 1% solution. Methods: Nine vials of voriconazole (Vfend(®) I.V.) 1% solution were prepared. Approximately half of each solution was used to prime a commercially available CRI pump with attached subpalpebral lavage system (CRI/SPL unit) with the remaining solution stored in the commercial glass vial. Three CRI/SPL units and their three corresponding vials were stored at one of three temperatures: 23 °C, 33 °C, and 40 °C. The CRI pumps ran for 7 days, and the vials were st...
Grint NJ, Beths T, Yvorchuk K, Taylor PM, Dixon M, Whay HR, Murrell JC.To evaluate a mechanical nociceptive threshold (MNT) testing device in the donkey, and to investigate the influence of potential confounders on MNTs generated. Methods: Prospective, randomised. Methods: Sixteen castrated male donkeys aged 4-9 years, weighing 105-170 kg. Methods: Mechanical nociceptive thresholds were measured using an actuator with three pins placed on the dorsal aspect of the distal limb, connected to a force meter. The pins (surface area 15 mm(2) ) were extruded onto the limb by pressurising an air-filled syringe, until the MNT force (when foot-lift was observed) or 25 N (cu...
Haeussler S, Luepke M, Seifert H, Staszyk C.In equine practice, teeth corrections by means of motorized grinding systems are standard procedure. The heat resulting from that treatment may cause irreparable damage to the dental pulp. It has been shown that a 5.5°C temperature rise may cause severe destruction in pulp cells. Hence, the capability to continuously form secondary dentine is lost, and may lead, due to equine-typical occlusal tooth abrasion, to an opening of the pulp cavity.To obtain reliable data on the intra-pulp increase in temperature during corrective treatments, equine cheek teeth (CT) were modified in a way (occlusal s...
Holcomb KE, Tucker CB, Stull CL.Provision of shade is recommended by best practice guidelines for horses living in hot, sunny environments despite a lack of research focused on potential benefits. We found in a previous study that horses without access to shade showed greater rectal temperature (RT), respiration rate (RR), and skin temperature (SK) and exhibited more sweat than horses that were completely shaded. Yet not known is whether horses will choose to stand in the shade when given a choice of areas with and without this resource. Our objective was to assess horse preference for shaded and unshaded areas in the hot an...
Khoshtariya DE, Dolidze TD, Shushanyan M, van Eldik R.Horse muscle myoglobin (Mb) was tightly immobilized at Au-deposited ~15-Å-thick mixed-type (1:1) alkanethiol SAMs, HS-(CH₂)₁₁-COOH/HS-(CH₂)₁₁-OH, and placed in contact with buffered H₂O or D₂O solutions. Fast-scan cyclic voltammetry (CV) and a Marcus-equation-based analysis were applied to determine unimolecular standard rate constants and reorganization free energies for electron transfer (ET), under variable-temperature (15-55 °C) and -pressure (0.01-150 MPa) conditions. The CV signal was surprisingly stable and reproducible even after multiple temperature and pressure cycl...
Longland AC, Barfoot C, Harris PA.The effects of different water-soaking treatments on removal of water-soluble carbohydrates (WSC), WSC constituents and protein from four UK hays were determined. Hays were soaked in water for up to 16 hours at mean temperatures of 8°C, 16°C, in hot tap water (initially 49°C) or agitated and rinsed in clean water at 16°C. Initial hay WSC contents ranged from 154 to 216 g/kg dry matter. Losses of WSC from hays after 16 hours soaking at 8°C, 16°C, 16°C plus agitation and 49°C averaged 28, 46, 49 and 44 per cent, respectively. Corresponding percentage losses of fructan were 16, 37, 39 and...
van Eps AW, Pollitt CC, Underwood C, Medina-Torres CE, Goodwin WA, Belknap JK.Prophylactic digital hypothermia reduces the severity of acute laminitis experimentally but there is no evidence for its efficacy as a treatment once lameness has already developed. Objective: To investigate the therapeutic effects of digital hypothermia, applied after the onset of lameness, in an experimental acute laminitis model. Methods: Randomised, controlled (within subject), blinded, experimental trial. Methods: Eight Standardbred horses underwent laminitis induction using the oligofructose model. Once lameness was detected at the walk, one forelimb was continuously cooled (CRYO), with ...
Alberghina D, Casella S, Giannetto C, Marafioti S, Piccione G.Serum protein electrophoresis (SPE) is a technique that could be considered one of the most useful diagnostic aids available to the clinician. The effect of storage time and temperature on the total proteins and electrophoretic fractions (albumin, α1-, α2-, β1-, β2-, and γ-globulins) was assessed in 24 healthy horses. All samples, collected by jugular vein puncture, were centrifuged and divided into 4 aliquots. The 1st aliquot was analyzed within 3 h from collection (time 0), the 2nd was refrigerated at +4°C for 24 h, the 3rd was refrigerated at +4°C for 48 h, and the last was frozen at...
Hartwig FP, Lisboa FP, Hartwig FP, Monteiro GA, Maziero RR, Freitas-Dell'Aqua CP, Alvarenga MA, Papa FO, Dell'Aqua JA.During the cooling process, sperm may suffer irreversible damage that compromises the fertility rate. Incorporating cholesterol-loaded cyclodextrin (CLC) represents a strategy to increase sperm resistance at low temperatures; however, high levels of cholesterol in the cell membrane can interfere with sperm capacitation. The goals of this study were to determine the CLC concentration and cooling temperature that produce optimal kinetic parameters and viability of sperm from stallions identified as bad coolers (BCs) and good coolers (GCs), as well as the effect of adding CLC on the occurrence of...
Bartolomé E, Sánchez MJ, Molina A, Schaefer AL, Cervantes I, Valera M.The aims of this study were, first, to evaluate eye temperature (ET) with infrared thermography and heart rate (HR) to measure stress in horses during show jumping competitions and their relationship with competition results, and second, to evaluate the influence of different extrinsic and intrinsic factors of the horse on the stress measurements analysed. One hundred and seventy-three Spanish Sport Horses were analysed for ET and HR, and these measurements were taken 3 h before the competition, just after and 3 h after it. Two interval measurements were also assessed for each parameter. Posit...
Brinkmann L, Gerken M, Riek A.Water is an essential nutrient necessary to support life, and adequate water supply is crucial for animal survival and productivity. The present study was designed to determine seasonal changes in the water metabolism of horses under outdoor conditions. Total body water (TBW) and total water intake (TWI) of 10 adult Shetland pony mares were estimated at monthly intervals for 14 mo by using the deuterium dilution technique. During the last 4 mo, 5 ponies were fed restrictively to simulate natural feed shortage in winter, and 5 ponies served as controls. The TBW (kg) was closely related to body ...
Oldenhof H, Gojowsky M, Wang S, Henke S, Yu C, Rohn K, Wolkers WF, Sieme H.The aim of this study was to determine how different membrane-permeable and -impermeable cryoprotective agents modulate tolerance of stallion sperm to osmotic stress and stabilize membranes during cryopreservation. Special emphasis was on hydroxyl ethylene starch (HES), which exposes cells to minimal osmotic stress due to its large molecular weight. Percentages of motile sperm post-thaw were found to be similar when glycerol, sucrose, and HES were used at their optimal concentrations. Percentages of plasma membrane intact sperm after return to isotonic medium were highest for HES. Fourier tran...
Tinkler SH, Couëtil LL, Constable PD.The stability of total CO2 concentration (ctCO2) in plasma is influenced by storage temperature and handling during sample processing. Conflicting information exists regarding the stability of ctCO2 in equine plasma over time, and the effect of centrifugation on the measured value for plasma ctCO2 is unclear. Objective: To determine plasma ctCO2 stability over 5 days when equine blood is collected into Vacutainer tubes, centrifuged within 30 min of collection, and stored at 4 degrees C; and to determine whether a delay in centrifugation increases the rate at which plasma ctCO2 decreases over t...
McDowell KJ, Moore ES, Parks AG, Bush LP, Horohov DW, Lawrence LM.The hypotheses that endophyte (Neotyphodium coenophialum)-infected tall fescue (TF) seed causes vasoconstriction in horses in vivo and that ground seed would cause more pronounced vasoconstriction than whole seed were tested. Ten horses each received 1 of 3 treatments: endophyte-free ground (E-G; n = 4 horses) seed, endophyte-positive whole (E+W; n = 3) seed, or endophyte-positive ground (E+G; n = 3) seed. There were two 14-d periods, P1 and P2. During P1, animals were adapted to a concentrate (0.2% BW, as fed, twice daily) and alfalfa cubes. During P2, the seed was mixed into the concentrate ...
Paz S, Malkinson D, Green MS, Tsioni G, Papa A, Danis K, Sirbu A, Ceianu C, Katalin K, Ferenczi E, Zeller H, Semenza JC.In the summer of 2010, Europe experienced outbreaks of West Nile Fever (WNF) in humans, which was preceded by hot spells. The objective of this study was to identify potential drivers of these outbreaks, such as spring and summer temperatures, relative humidity (RH), and precipitation. Methods: Pearson and lag correlations, binary and multinomial logistic regressions were used to assess the relationship between the climatic parameters and these outbreaks. Results: For human morbidity, significant (<0.05) positive correlations were observed between a number of WNF cases and temperature, with...
Kohn CW, Hinchcliff KW, McCutcheon LJ, Geor R, Foreman J, Allen AK, White SL, Maykuth PL, Williamson LH.The impending 1996 summer Olympic 3-day-event in Atlanta has focused attention on the need to determine what modifications to the demanding Endurance Test will be required to ensure safety of the horses competing. Three groups of horses participated in a Field Trial held in August of 1994 in northern Georgia to determine the safety and feasibility of conducting a modified 3-day-event in hot, humid weather. One group (TD) completed a modified 1 Star 3-day-event test, a control group (HT) completed a Horse Trial identical to the modified 1 Star test except for the omission of Phases B and C and ...
Lamoureux JL, Fitzgerald SD, Church MK, Agnew DW.Diagnostic laboratories are frequently required to assess the antemortem nutritional condition of deceased animals. The percentage of fat in the bone marrow is used to diagnose starvation because this fat depot is typically the last in the body to be depleted. Diagnosticians rely on measurement of bone marrow adipose content using fat solvent-extraction methods; however, the effects of tissue storage conditions before processing have not been fully assessed. The current study focuses on evaluating the effects of 3 storage conditions (refrigeration [4 °C], freezing [-20 °C], and ambient tempe...
Sosa León LA, Davie AJ, Hodgson DR, Rose RJ.Effects of different tonicities, glucose concentrations and temperatures of an oral rehydration solution (ORS) on its uptake and elimination in resting horses were studied. Fluid and electrolyte deficits similar to those occurring during prolonged exercise were induced by the administration of 1 mg/kg bwt of frusemide i.m., 3 h prior to the ORS. Fluid was administered via nasogastric tube at a volume equivalent to 4% bodyweight, which approximated diuretic induced losses. The uptake of fluid was evaluated by changes in haematocrit (PCV) and plasma total protein concentration (TP). Changes in e...
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...
Maśko M, Witkowska-Piłaszewicz O, Jasiński T, Domino M.Infrared thermography is a non-invasive technique which allows to distinguish between pregnant and non-pregnant animals. Detecting accurate body surface temperatures can be challenging due to external factors altering thermograph measurements. This study aimed to determine the associations between the ambient temperature, the hair coat features and the temperatures of mares' abdomens. It compared pregnant and non-pregnant mares throughout 11 months. The research was carried out on 40 Konik Polski mares, which were divided into pregnant and non-pregnant groups. The temperature (Tmax, maximal; ...
Holcomb KE, Stull CL.The Federation of Animal Science Societies (FASS) recommends providing access to shade for horses in hot, sunny weather at equine facilities. Previously, we found that healthy, mature domestic horses use shade with behavioral and physiological benefits during those weather conditions. The objective of this study was to characterize preference, frequency, and duration of shade use by healthy, mature horses in a Bureau of Land Management (BLM) holding facility during hot, sunny weather. The study took place at the BLM's Palomino Valley Wild Horse and Burro Center in Reno, NV, from Aug. 10 to Oct...
Guignot F, Bezard J, Palmer E.In the mare only a limited number of oocytes can be successfully collected in vivo, so that when large numbers of oocytes are needed for experimentation, ovaries harvested from slaughtered mares must be used. The resulting temperature changes and time intervals mandated by handling and transport of ovaries from the slaughterhouse to the laboratory adversely affect the rate of oocyte recovery and their quality after IVF and maturation. We chose to study the effect of temperature and time in transit of excised ovaries by evaluating rate of oocyte recovery, nuclear maturation stage reached before...
Jørgensen GH, Aanensen L, Mejdell CM, Bøe KE.Horses may adapt to a wide range of temperatures and weather conditions. Owners often interfere with this natural thermoregulation ability by clipping and use of blankets. Objective: To investigate the effects of different winter weather conditions on shelter seeking behaviour of horses and their preference for additional heat. Methods: Observational study in various environments. Methods: Mature horses (n = 22) were given a free choice test between staying outdoors, going into a heated shelter compartment or into a nonheated shelter compartment. Horse location and behaviour was scored using i...
Geraghty TE, Love S, Taylor DJ, Heller J, Mellor DJ, Hughes KJ.A total of 102 horses that had a catheter introduced intravenously to facilitate treatment had the catheterised jugular vein and contralateral vein examined by ultrasound every 48 hours. Subclinical complications were defined by thrombus formation or thickening of the venous wall, and the data were analysed to establish risk factors for the development of these complications. The horses with a rectal temperature above 38.5 degrees C when the catheter was introduced were four times more likely to develop complications, than the horses with a lower temperature. The administration of a NSAID whil...
Mills PC, Scott CM, Marlin DJ.We investigated the role of NO in the control of thermoregulation. We measured sweating rate and body temperatures (core, rectal and skin) in five thoroughbred horses during exercise of variable intensity on a high-speed treadmill. A standard exercise test (SET) consisting of three canters (8 m s-1), with walking and trotting between each canter, was performed twice, in random order, by each horse and N omega-nitro-L-arginine methyl ester (L-NAME; 20 mg ml-1), a competitive inhibitor of nitric oxide synthase (NOS), was infused into the central circulation after the first canter in the test SET...
Ward MP, Wittich CA, Fosgate G, Srinivasan R.West Nile Virus (WNV) was first detected in the Texas equine population during June 2002. Infection has since spread rapidly across the state and become endemic in the equine population. Environmental risk factors associated with equine WNV attack rates in Texas counties during the period 2002 to 2004 were investigated. Equine WNV attack rates were smoothed using an empirical Bayesian model, because of the variability among county equine populations (range 46-9,517). Risk factors investigated included hydrological features (lakes, rivers, swamps, canals and river basins), land cover (tree, mos...
Carlson GP, Rumbaugh GE, Harrold D.Eight normal horses were held without access to food or water for 72 hours during a period of high environmental temperatures. During this period, the horses had an average weight loss of 51.6 kg (10.7% of body weight). Highly significant (P less than 0.001) decreases in extracellular fluid volume (18.6 L) and plasma volume (5 L) were observed during this period as compared with base-line values. Plasma protein, sodium, chloride, and osmolality progressively increased in response to the dehydration, whereas packed cell volume, plasma potassium, calcium, magnesium, and phosphate were not signif...
McConaghy FF, Hodgson DR, Hales JR, Rose RJ.Cardiac output (Q) and tissue blood flows (BF) were measured in four ponies at rest, after 30 min of moderate exercise (ME) (approximately 30% VO2max) and following moderately intense exercise (M-IE) (approximately 65%) until fatigue, in a mildly hot (MH) environment (dry bulb temperature = 41 degrees C, wet bulb temperature = 27.5 degrees C). Exercise at both intensities resulted in increases in Q (15.6 +/- 1.7 [rest] vs. 35.8 +/- 2.6 [ME] vs. 48.6 +/- 3.9 [M-IE] l/min) and VO2 (4.7 +/- 0.9 vs. 24.5 +/- 1.2 vs. 55.8 +/- 5.8 ml/kg/min). When compared to ME, M-IE resulted in decreases in BF to ...
Petrov R, MacDonald MH, Tesch AM, Van Hoogmoed LM.To determine rate and degree of cooling for the superficial digital flexor tendon (SDFT) during a standard cryotherapy application in horses and evaluate in vitro effects of cooling on survival of tendon cells. Methods: 6 limbs of 5 adult horses and cultured cells obtained from SDFT of 3 adult horses during necropsy. Methods: In vivo data were acquired by use of a thermocouple temperature probe inserted into the SDFT of a forelimb of each standing sedated horse. After baseline temperatures were recorded, a commercial compression splint with circulating coolant was placed on each selected limb,...
McConaghy FF, Hodgson DR, Rose RJ, Hales JR.Radioactive microspheres were used to measure cardiac output and blood flow to most major tissues in 4 ponies at rest in thermoneutral (16 degrees C/60% RH) and mildly hot (41 degrees C/34% RH) environments. In response to heat stress there were increases in cardiac output (2-fold), respiratory frequency (5-fold), blood flow to the skin of the body (3-fold), and limbs (50%), respiratory muscles (2-fold) and the upper respiratory tract (3-fold). Ponies were able to maintain body temperature in the hot environment by increasing blood flow to the tissues involved in heat dissipation, while blood ...
Hendricks KE, Hansen PJ.Apoptosis is common during spermatogenesis. Here, it was tested whether apoptosis could be induced in sperm after ejaculation. There were several lines of evidence to indicate that sperm are resistant to induction of apoptosis. First, incubation of bull sperm at temperatures characteristic of normothermia (38.5 degrees C) or heat shock (40 and 41 degrees C) for 4h did not increase the proportion of sperm positive for the TUNEL reaction. There was also no reduction in mitochondrial polarity caused by exposure to 40 or 41 degrees C. Incubation at 38.5 degrees C (least-squares mean+/-SEM=4.0+/-1....
McCutcheon LJ, Geor RJ.Sweating responses were examined in five horses during a standardized exercise test (SET) in hot conditions (32-34 degrees C, 45-55% relative humidity) during 8 wk of exercise training (5 days/wk) in moderate conditions (19-21 degrees C, 45-55% relative humidity). SETs consisting of 7 km at 50% maximal O(2) consumption, determined 1 wk before training day (TD) 0, were completed on a treadmill set at a 6 degrees incline on TD0, 14, 28, 42, and 56. Mean maximal O(2) consumption, measured 2 days before each SET, increased 19% [TD0 to 42: 135 +/- 5 (SE) to 161 +/- 4 ml. kg(-1). min(-1)]. Peak swea...
Devireddy RV, Swanlund DJ, Alghamdi AS, Duoos LA, Troedsson MH, Bischof JC, Roberts KP.The effects of extracellular ice and cryoprotective agents on the measured volumetric shrinkage response and the membrane permeability parameters of equine spermatozoa have been reported previously. The volumetric shrinkage data were obtained using a differential scanning calorimeter technique that was independent of cell shape. The aim of this study was to examine the effects of collection and cooling conditions on the motility and the water transport parameters at subzero temperatures of equine spermatozoa. Stallion semen samples were collected using either a commercial lubricating agent, wh...
Permyakov SE, Khokhlova TI, Uversky VN, Permyakov EA.The triggering of Ca(2+) signaling pathways relies on Ca(2+)/Mg(2+) specificity of proteins mediating these pathways. Two homologous milk Ca(2+)-binding proteins, bovine alpha-lactalbumin (bLA) and equine lysozyme (EQL), were analyzed using the simplest "four-state" scheme of metal- and temperature-induced structural changes in a protein. The association of Ca(2+)/Mg(2+) by native proteins is entropy-driven. Both proteins exhibit strong temperature dependences of apparent affinities to Ca(2+) and Mg(2+), due to low thermal stabilities of their apo-forms and relatively high unfavorable enthalpi...
Martel P, Calmettes P, Hennion B.Equine red blood cells were washed in saline heavy water (2H2O) to exchange the hydrogen atoms of the non-hemoglobin components with deuterons. This led to novel neutron scattering measurements of protein vibrations within a cellular system and permitted a comparison with inelastic neutron scattering measurements on purified horse hemoglobin, either dry or wetted with 2H2O. As a function of wavevector transfer Q and the frequency transfer v the neutron response typified by the dynamic structure factor S(Q, v) was found to be similar for extracted and cellular hemoglobin at low and high tempera...
Fanelli D, Tesi M, Ingallinesi M, Camillo F, Panzani D.This study retrospectively analysed the effects of different environmental factors such as the photoperiod, temperature/humidity index of 19 years of a commercial embryo transfer programme performed in central Italy. From 340 donors of different breeds and aged between 2 and 25 years, 576 embryos of an excellent or good quality were obtained by uterine flushing on days 7-8 after ovulation. The embryos were transferred to 259 recipients, aged between 2 and 16 years, and belonging to different breeds. Both the donors and the recipients were employed for several cycles/years. At the time of tr...
Thornton JR.Current knowledge and understanding of the hormonal response to exercise are limited, whether in relation to horses, humans, or other species. The changes in plasma concentration of some hormones occur early in exercise, apparently owing to a neuronal stimulation, whereas others, being pituitary dependent, require hormonal stimulation. Also, although it is possible to observe changes in plasma concentrations of hormones, the mechanism by which this is achieved is not always understood, and unless the nonprotein-bound, or active, form of the hormone is also determined, changes in plasma concent...
DeMeio JL, DeSanctis AN.Normal and immune sera were obtained from horses immunized with either aqueous, alum, or adjuvant bivalent vaccines containing Milford equine 2 virus. Upon heating at 56 C for 30 min, a factor, required for hemagglutination-inhibition but not complement fixation or neutralization testing, was destroyed. This factor which is present in normal sera does not appear to be complement.
Dini P, Ducheyne K, Lemahieu I, Wambacq W, Vandaele H, Daels P.Several methods have been proposed to advance the onset of the breeding season in horses. Most of them are based on the exposure to an artificial lighting period combined with hormonal treatments. Mares exposed to an artificial photoperiod are most often housed indoors where the ambient temperature is often higher than the outside temperature. Mares held in barns are also exposed to different daylight intensities than horses kept outside, depending on the architecture. In the current study, we evaluated the impact of ambient temperature, daylight intensity and changes in body condition score (...
Mostert HJ, Lund RJ, Guthrie AJ, Cilliers PJ.A theoretical integrative model was developed to determine the heat balance of horses working in a given environment. This model included the following parameters: metabolic heat gain, solar heat gain, evaporative heat loss due to sweating, respiratory tract heat loss, radiation from the body and heat gain or loss due to convection and conduction. The model developed in this study includes an unique approach for estimating heat loss via evaporation of sweat from the animal's skin surface. Previous studies modelling evaporative heat dissipation were based on the volume of sweat loss. While it i...
McLaughlin BG, McLaughlin PS.Samples of equine vitreous humor were analyzed for urea nitrogen, creatinine, sodium, chloride, phosphorus, calcium, potassium, and magnesium concentrations. Fresh vitreous chemical concentrations were compared to corresponding serum concentrations and expressed as a vitreous to serum ratio. The effects of postmortem time and temperature on the stability of the chemical concentrations were determined by incubation of the samples at 4 degrees C, and 20 degrees C and 37 degrees C for 6, 12, 24, or 48 h. Chemical concentrations were generally more stable at lower temperatures and shorter incubati...
Reesink HL, Divers TJ, Bookbinder LC, van Eps AW, Soderholm LV, Mohammed HO, Cheetham J.To compare effects of 3 methods of topically applied cold treatment (cryotherapy) on digital laminar and venous temperatures in horses. Methods: 9 healthy adult Thoroughbreds. Methods: Thermocouples were placed in palmar digital veins and digital laminae of both forelimbs of horses. Three methods of cryotherapy were applied to the distal aspects of the limbs: wader boot (63-cm-tall vinyl boot filled with ice and water [ice slurry]), ice bag (5-L fluid bag filled with ice slurry), and a gel pack boot (boot containing frozen gel packs). Gel packs and ice slurries were replenished every hour duri...
