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.
McIlwraith CW, Frisbie DD, Kawcak CE.Osteoarthritis (OA) is an important cause of pain, disability and economic loss in humans, and is similarly important in the horse. Recent knowledge on post-traumatic OA has suggested opportunities for early intervention, but it is difficult to identify the appropriate time of these interventions. The horse provides two useful mechanisms to answer these questions: 1) extensive experience with clinical OA in horses; and 2) use of a consistently predictable model of OA that can help study early pathobiological events, define targets for therapeutic intervention and then test these putative thera...
Mata F.Several growth models are commonly used in the biological sciences, to model the follicle growth occurring in the estrous cycle. The aim of this project was to find the model that best fit the follicular size growth data for Lusitano mares. Retrospective data collected from reproduction book records of n=84 mares and n=124 cycles was used to find the series to be fitted to the models. The exponential, Gompertz, logistic, von Bertalanffy, Richards and Weibull models were used, and the most parsimonious and best fit was achieved with the logistic model (r(2)=0.999). The logistic model fits the L...
Beckelmann J, Budik S, Helmreich M, Palm F, Walter I, Aurich C.An adjustment of sex ratio of offspring to the conditions present at conception is seen in many mammals including horses. This depends on preferential survival of male embryos under conditions of high energy intake. In several species, growth factors including insulin like growth factor (IGF)-1 have been shown to promote embryonic development by decreasing apoptosis and increasing cell proliferation. We hypothesized that sex-related differences in IGF-1 expression in equine embryos during the phase of maternal recognition of pregnancy might exist and thus contribute to preferential survival of...
Nagao JF, Neves Neto JR, Papa FO, Alvarenga MA, Freitas-Dell'Aqua CP, Dell'Aqua JA.This study aimed to determine whether deslorelin acetate could induce double ovulation in mares. In Experiment 1, eight mares were treated with prostaglandin on Day 8 (D8) after ovulation, then treated with saline or with 100 μg of a controlled-release formulation of deslorelin acetate vehicle intramuscularly (IM) every 12h from D8 after ovulation until at least two follicles reached 33 mm. At this time, ovulation was induced with 2500 IU of hCG. Artificial insemination was performed 24h after induction, and embryos were collected on the eighth day after ovulation was first detected. In Exper...
Skedros JG, Keenan KE, Williams TJ, Kiser CJ.In bone, matrix slippage that occurs at cement lines of secondary osteons during loading is an important toughening mechanism. Toughness can also be enhanced by modifications in osteon cross-sectional size (diameter) for specific load environments; for example, smaller osteons in more highly strained "compression" regions vs. larger osteons in less strained "tension" regions. Additional osteon characteristics that enhance toughness are distinctive variations in collagen/lamellar organization (i.e., "osteon morphotypes"). Interactions might exist between osteon diameter and morphotype that repr...
Franklin SH, Van Erck-Westergren E, Bayly WM.Horses are elite athletes when compared with other mammalian species. In the latter, performance is limited by cardiovascular or musculoskeletal performance whereas in athletic horses it is the respiratory system that appears to be rate limiting and virtually all horses exercising at high intensities become hypoxaemic and hypercapnoeic. This is due to both diffusion limitation and a level of ventilation inadequate for the metabolic level that enables horses to exercise at these intensities. In conjunction with these blood gas changes, total pulmonary resistance increases and the work of breath...
Katz LM, Bailey SR.With the increasing number of studies being published on the different experimental models used to induce and study acute laminitis, the pathophysiological events associated with these various models (i.e. starch overload, oligofructose overload, black walnut extract and hyperinsulinaemia) can be compared more realistically. Within this review, the mechanisms for metabolic vs. inflammatory laminitis are discussed, and the question of how pasture laminitis may fit into any of the proposed mechanisms is addressed.
Bellenzani MC, Merritt JS, Clarke S, Davies HM.To investigate forelimb hoof wall strains and shape changes in unshod horses undergoing regular moderate exercise on a treadmill at selected speeds and gaits. Methods: 6 horses of various body types. Methods: Each horse was exercised on a treadmill (walking, trotting, and cantering, with or without galloping at 12.5 m/s) 3 times a week for 4 consecutive weeks; duration of each exercise session ranged from 10 to 14 minutes. During the 4-week period, the proximal hoof circumference (PHC) and toe angle (TA) of each forelimb hoof were measured weekly with a flexible measuring tape and a hoof gauge...
Szober CM, Hauck SM, Euler KN, Fröhlich KJ, Alge-Priglinger C, Ueffing M, Deeg CA.The purpose of this study was to characterize the cell surface proteome of native compared to cultured equine retinal pigment epithelium (RPE) cells. The RPE plays an essential role in visual function and represents the outer blood-retinal barrier. We are investigating immunopathomechanisms of equine recurrent uveitis, an autoimmune inflammatory disease in horses leading to breakdown of the outer blood-retinal barrier and influx of autoreactive T-cells into affected horses' vitrei. Cell surface proteins of native and cultured RPE cells from eye-healthy horses were captured by biotinylation, an...
Symons JE, Entwistle RC, Arens AM, Garcia TC, Christiansen BA, Fyhrie DP, Stover SM.To determine morphological and mechanical properties of trabecular bone of horses with a bone fragility syndrome (BFS; including silicate-associated osteoporosis). Methods: Cylindrical trabecular bone samples from the distal aspects of cadaveric third metacarpal bones of 39 horses (19 horses with a BFS [BFS bone samples] and 20 horses without a BFS [control bone samples]). Methods: Bone samples were imaged via micro-CT for determination of bone volume fraction; apparent and mean mineralized bone densities; and trabecular number, thickness, and separation. Bone samples were compressed to failur...
Kitaoka Y, Mukai K, Aida H, Hiraga A, Masuda H, Takemasa T, Hatta H.To investigate the effects of high-intensity training (HIT) on carbohydrate and fat metabolism in Thoroughbreds. Methods: 12 Thoroughbreds (3 to 4 years old; 6 males and 6 females). Methods: Horses performed HIT for 18 weeks. They ran at 90% or 110% of maximal oxygen consumption ((V)O(2max)) for 3 minutes (5 d/wk) and were subjected to incremental exercise testing (IET) before and after training. Blood samples were collected during IET, and muscle samples were obtained from the gluteus medius muscle immediately after IET. Phosphofructokinase, citrate synthase, and β-3-hydroxyacyl CoA dehydrog...
Sugimoto M, Kuwano A, Ikeda S, Kume S, Yoshihara E, Wada S.To examine the distribution of water in hoof wall specimens of horses via nuclear magnetic resonance (NMR) microscopy and determine changes in water distribution during hydration. Methods: 4 hoof wall specimens (2 obtained from the dorsum and 1 each obtained from the lateral quarter and lateral heel regions) of the stratum medium of healthy hooves of 1 horse. Methods: Equine hoof wall specimens were examined via NMR microscopy. Proton density-weighted 3-D images were acquired. Changes during water absorption were assessed on sequential images. Results: The inner zone of the stratum medium had ...
Despite the number of postpartum handling that a newborn experiences, few studies focus on their long-term consequences. In rats, regular long separations from the mother, during the early life, led to modifications of the locomotor activity when the animal is confronted to a stressor. In horses, one component of the behavioral response to stressful situation is active locomotion. We wondered if the routine postpartum handling undergone by foals, would affect their level of reactivity or the way they express their stress, when older. One single prolonged bout of handling just after birth clear...
Klein C, Troedsson MH, Rutllant J.The expression of 12 different aquaporin subtypes in equine endometrium was examined at the mRNA and protein level. Endometrial samples were obtained during anoestrus, oestrus, 8, and 14 days after ovulation in non-pregnant mares, and 14 days after ovulation in pregnant mares. Quantitative PCR revealed a time-dependent pattern for all aquaporin subtypes examined except for AQP10 and 12. AQP3, 5 and 7 showed highest mRNA abundance 8 days after ovulation, while AQP0 and 2 were most abundant at Day 14 of the cycle in non-pregnant mares. At 14 days of pregnancy, AQP1, 4, 8, 9 and 11 displayed ...
Adams GP, Ratto MH.Ovulation in mammals involves pulsatile release of GnRH from the hypothalamus into the hypophyseal portal system with subsequent release of LH from the anterior pituitary into systemic circulation. Elevated circulating concentrations of LH induce a cascade of events within the mature follicle, culminating in follicle rupture and evacuation. The broad classification of species as either spontaneous or induced ovulators is based on the type of stimulus responsible for eliciting GnRH release from the hypothalamus. In spontaneously ovulating species (e.g., human, sheep, cattle, horse, pigs), relea...
Yamaguchi T, Endo Y, Nambo Y, Sato F, Sasaki N, Yamada K.Equine bone scintigraphy is usually performed with horses in standing position under sedation. However, swaying motion often leads to poor-quality images. To examine the usefulness of motion correction (MC) processing, equine bone scintigrams were evaluated using Scheffé's method of paired comparisons. A significant difference in evaluation scores was detected by analysis of variance (F test, P<0.01). According to all observers, Yardstick analysis scores were higher for images use of MC processing than for those no use of MC processing, for all parts. Overall scores of 5 observers were as ...
Collodel G, Rinaldi S, Moretti E, Fontani V, Castagna A, Iacoponi F, Terzuoli G, C뻝u F, Careddu GM, Cossu I, Passino ES.The Radio Electric Asymmetric Conveyer (REAC) has been mostly applied to treat symptoms related to psychological stress. In the study, we demonstrated the effect of REAC-Veterinary Neuro Psycho Physical Optimization (VNPPO) treatment protocol on sperm parameters of subfertile (n=11) and fertile (n=4) stallions. Subfertile stallions showed a reduced sperm concentration, progressive motility and normal morphology compared to fertile stallions. An increase in progressive sperm motility and quality of sperm morphology was found in subfertile stallions after the REAC-VNPPO treatment. The positive e...
D'Arcy-Moskwa E, Noble GK, Weston LA, Boston R, Raidal SL.Newer NSAIDs that more selectively target the induced isoform of the cyclooxygenase enzyme (COX2) activity might reduce adverse effects while preserving therapeutic benefits of these drugs. Objective: To compare the effect of oral administration of multiple dose rates of meloxicam and phenylbutazone (PBZ) on gastric mucosal integrity in horses. Methods: Twenty-five light breed horses. Methods: In vivo toxicity study. Horses were randomly assigned to 5 treatment groups, receiving placebo, PBZ (4.4 mg/kg PO q12h day 1, 2.2 mg/kg PO q12h for 4 days, 2.2 mg/kg PO q24h for 9 days), or 3 dose rates ...
Galvão A, Valente L, Skarzynski DJ, Szóstek A, Piotrowska-Tomala K, Rebordão MR, Mateus L, Ferreira-Dias G.Regulation of immune-endocrine interactions in the equine endometrium is not fully understood. The aims of the present study were to: (1) investigate the presence of tumour necrosis factor alpha (TNF), interferon gamma (IFNG), Fas ligand (FASLG) and their receptors in the mare endometrium throughout the oestrous cycle; and (2) assess endometrial secretory function (prostaglandins), angiogenic activity and cell viability in response to TNF, oestradiol (E2), progesterone (P4) and oxytocin (OXT). Transcription of TNF and FASLG mRNA increased during the early and late luteal phase (LP), whereas IF...
Kwok WH, Ho EN, Leung GN, Wong AS, Yue SK, Wan TS.Relaxin (RLX) is a peptide hormone belonging to the relaxin-like peptide family. Relaxin-2 (RLX-2), a heteromeric polypeptide consisting of an A-chain (24 amino acids) and a B-chain (29 amino acids) linked together by two inter-chain disulfide bonds, is the main circulating RLX hormone in human. Due to its ability to dilate blood vessels surrounding the smooth muscles via induction of nitric oxide resulting in the increase of blood and oxygen supplies to the muscles, it may enhance athletic performance and is therefore banned in horseracing, equestrian competitions, and human sports. In order ...
Lovati AB, Corradetti B, Cremonesi F, Bizzaro D, Consiglio AL.Adult bone marrow mesenchymal stem cells (BM-MSCs) are a potential cell source for tendon repair in direct cell therapy and tissue engineering investigations. The purpose of this study was to evaluate the tenogenic induction of undifferentiated BM-MSCs under indirect co-culture technique with trimmed native tendon tissue. Since the horse represents a preferred species to study tendon regenerative strategies, this work was conducted on equine BM-MSCs. Methods: Equine BM-MSCs were co-cultured in a transwell system with tendon tissue fragments. The BM-MSC tenogenic differentiation was evaluated b...
Jellyman JK, Allen VL, Holdstock NB, Fowden AL.Studies in humans and animals have linked abnormal programming of adult tissue function to excess glucocorticoids during perinatal development. The current study investigated the hypothesis that physiological variations in glucocorticoid concentrations during early neonatal life of the foal alter the secretory responses of the pancreatic β cells 2 and 12 wk after treatment. Spontaneously delivered foals received either saline or long-acting ACTH for 5 d from 1 d after birth to maintain an endogenous rise in cortisol concentrations. Starting at d 10, pancreatic β cell function was studied usi...
Wieser B, Tichy A, Nell B.Guinea pigs have a very low threshold of corneal sensitivity and at the same time nearly no reflex tearing compared to dogs, cats, and horses. The question arose whether there is a general correlation between corneal sensitivity and the quantity of reflex tearing. Methods: Totally 160 animals of 8 different species (20 animals per species) were investigated. Methods: The corneal touch threshold (CTT) was measured with a Cochet-Bonnet esthesiometer. The palpebral fissure length (PFL) was measured with a calliper ruler. The Schirmer tear test (STT) was modified by adapting the width of the STT s...
Onmaz AC, Stoklas-Schmidt C, van den Hoven R.The aim of the study was to analyse the day-to-day variability of the respiratory resistance (R(rs)) and the reactance (X(rs)) in 5 horses in a status of remission of recurrent airway obstruction by forced oscillometry system (FOS). Furthermore, the effects of stabling, outdoor and room temperature and humidity on these parameters were determined. Mean R(rs) at oscillation frequencies 1, 1.5, 2 and 3 Hz were all significantly higher in the morning than in the afternoon, while X(rs) was not significantly affected by time of the day. R(rs) was significantly different on various sampling days at ...
Koj A, Chudzik J, Dubin A.Two proteinases (2A and 2B) purified from the granular fraction of horse blood leucocytes degrade casein (Km values 12.8 and 6mg/ml respectively) with maximum activity at pH 7.4 and in the presence of 2m-urea. Urea-denatured haemoglobin, fibrinogen, albumin and resorcin/fuchsin-stained elastin are digested at a slower rate. The enzymes hydrolyse synthetic substrates of elastase, N-benzyloxycarbonyl-L-alanine 4-nitrophenyl ester (Km 0.114 and 0.178 mM) and N-acetyl-tri-L-alanine methyl ester (Km 5.55 and 0.98 mM), but they do not hydrolyse synthetic substrates of trypsin, chymotrypsin and throm...
Moore JN, Garner HE, Berg JN, Sprouse RF.Cecal fluid from two adult horses was assayed by the limulus amebocyte lysate system for endotoxin before and after carbohydrate overload of the gastrointestinal tract. There were increases in cecal fluid endotoxin concentrations at the 3-, 6-, and 12-hour samplings when compared with base-line values. Concomitant cecal fluid lactate concentrations and pH values increased and decreased, respectively. Both horses subsequently developed clinical signs of acute laminitis.
Cox JE, Edwards GB, Neal PA.The authors analyse data collected over 23 years from 500 cryptorchid horses. They show that left- and right-sided abdominal cases occur with approximately equal frequency in ponies. Approximately half the right-sided unilateral abdominal cases have the epididymal tail descended while only 20 per cent of the left-sided cases do. These findings are briefly discussed. From their analysis of inguinal cryptorchidism the authors conclude that it is a relatively more complex phenomenon with incidence changing with age as well as breed. Right-sided retention predominates in young ponies, probably bei...
Alberts MK, Clarke CR, MacAllister CG, Homer LM.To determine the pharmacokinetics of acetazolamide administered IV and orally to horses. Methods: 6 clinically normal adult horses. Methods: Horses received 2 doses of acetazolamide (4 mg/kg of body weight, IV; 8 mg/kg, PO), and blood samples were collected at regular intervals before and after administration. Samples were assayed for acetazolamide concentration by high-performance liquid chromatography, and concentration-time data were analyzed. Results: After IV administration of acetazolamide, data analysis revealed a median mean residence time of 1.71 +/- 0.90 hours and median total body c...
Byrne DP, Secombe CJ, Tan RHH, Perera DI, Watts SP, Wearn JG.Thyrotropin releasing hormone (TRH)-stimulation testing for pituitary pars intermedia dysfunction (PPID) in horses is only recommended at certain times of the year. Current diagnostic cut-off values reflect testing in the northern hemisphere during this time. The aims of this study were to evaluate TRH stimulation testing during two different phases of the circannual pituitary cycle and to determine whether diagnostic cut-off values developed in the northern hemisphere are appropriate in Australia. Thirteen clinically normal horses at Perth, Western Australia, and 23 horses at Townsville, Quee...
Ribitsch I, Peham C, Ade N, Dürr J, Handschuh S, Schramel JP, Vogl C, Walles H, Egerbacher M, Jenner F.Meniscal pathologies are among the most common injuries of the femorotibial joint in both human and equine patients. Pathological forces and ensuing injuries of the cranial horn of the equine medial meniscus are considered analogous to those observed in the human posterior medial horn. Biomechanical properties of human menisci are site- and depth- specific. However, the influence of equine meniscus topography and composition on its biomechanical properties is yet unknown. A better understanding of equine meniscus composition and biomechanics could advance not only veterinary therapies for meni...
Nambo Y, Nagaoka K, Tanaka Y, Nagamine N, Shinbo H, Nagata S, Yoshihara T, Watanabe G, Groome NP, Taya K.In female mammals, inhibin is secreted by the granulosa cells and selectively inhibits secretion of FSH. Although circulating immunoreactive (ir)-inhibin levels decrease after ovulation as a result of the disappearance of its main source, they abruptly increase at the time of ovulation in mares. To investigate the mechanisms responsible for this increase, 50 ml of equine follicular fluid (eFF) was administered into the abdominal cavity of mares during the luteal phase (eFF, n = 4). One hour after treatment, plasma levels of ir-inhibin and inhibin pro-alphaC (but not estradiol-17beta) were sign...
Hollis AR, Boston RC, Corley KT.Neonatal foals succumb rapidly to hypovolaemic shock in comparison to mature horses; they do not consistently increase their heart rate in response to hypotension and respond differently to fluid administration. The hormonal responses to hypovolaemia in the horse and foal require investigation. Objective: The hormonal responses to hypovolaemia and fluid administration differ between mature and neonatal horses. Methods: Five mature horses and 5 neonatal foals fulfilling predetermined criteria for hypovolaemia, were included in the study. A blood sample was taken at admission and after normalisa...
Olson LE, Lai-Fook SJ.Pleural liquid pressure was measured at end expiration in 11 spontaneously breathing anesthetized ponies in the prone and supine positions. A liquid-filled capsule was implanted into a rib to measure pleural liquid pressure with minimal distortion of the pleural space (Wiener-Kronish et al., J. Appl. Physiol. 59: 597-602, 1985). Capsule position relative to lung height was measured from thoracic radiographs taken in each position. In each body position, pleural liquid pressure was most negative in the superior lung regions and least negative in the inferior lung regions. In the supine position...
Amis TC, Pascoe JR, Hornof W.The regional distribution of ventilation to perfusion ratios (VA/Q) in the lungs of 8 healthy standing Thoroughbred geldings (4.4 +/- 1.5 years, 465.7 +/- 46.6 kg) was studied, using steady-state inhalation and IV infusion of the radioactive gas krypton-81m. The VA/Q was uniformly distributed within a vertical lung strip centered over the 9th rib on the right side. Ventilation per unit of alveolar volume (V/VA) assessed from the clearance of inhaled radioactive gas in 5 horses increased from 0.49 +/- 0.13 (arbitrary units) in nondependent lung zones to 1.45 +/- 0.16 in dependent lung zones. Se...
Thompson KN.This study was conducted to determine normal rates of growth of different skeletal segments in the thoroughbred horse. Growth of body weight and eight skeletal segments (wither height, hip height, body length, knee to pastern length, hock to pastern length, shoulder to pastern length, width of chest, depth of girth) were monitored in 106 horses (60 colts, 46 fillies) during the period from 14 to 588 d of age. Body weight gains were slightly higher (30 to 40 kg) than previously reported values. Growth in wither height and hip height were similar to previous reports. During the period measured i...
Perkins NR, Rogers CW, Firth EC, Anderson BH.To determine if the superficial digital flexor tendon (SDFT) of young Thoroughbred horses changed in size and echogenicity in association with early race training. Methods: Cross-sectional area (CSA) and echogenicity were determined ultrasonographically at five levels of the SDFT of the forelimbs of 2-year-old fillies (n=14), corresponding to 4, 8, 12, 16 and 20 cm distal to the accessory carpal bone (DACB). Measurements were made before and after a 13-week period in which a trained group of seven horses was compared with another group of seven untrained horses. Results: Level below the access...
Uberti B, Eberle DB, Pressler BM, Moore GE, Sojka JE.OBJECTIVE-To determine whether urine protein-to-creatinine (UP:C) ratio assessment provides an estimate of urine protein excretion (UPE) over a 24-hour period in horses and ponies, establish a preliminary UP:C ratio reference range, and determine UP:C ratio variation over time in healthy equids. ANIMALS-11 female horses and 6 female ponies. PROCEDURES-Urine was collected from all equids at 4-hour intervals for 24 hours. Total 24-hour UPE (mg of protein/kg of body weight) and UP:C ratio were determined; these variables were also assessed in aliquots of urine collected at 4-hour intervals. On 2 ...
Kayar SR, Hoppeler H, Armstrong RB, Laughlin MH, Lindstedt SL, Jones JH, Conley KR, Taylor CR.The mean minimal capillary transit time was estimated in muscles of various animals using a combination of physiological and morphometric methods. Radioactive microspheres were injected intravascularly in various animals running on a treadmill at maximum oxygen consumption rate (VO2,max) to label blood flow to individual muscles. The muscles were then removed and preserved by standard methods for electron microscopy. The volume density of mitochondria was measured to assess muscle oxidative capacity. Capillary densities in muscle cross-sections, capillary diameters and tortuosities were incorp...
Henckel P.The middle gluteal muscle of five, two-year-old untrained trotters was investigated by repeated needle biopsy sampling over a training period of six months. A second group of five, three-year-old untrained horses was included to examine the effect of growth. After the training period increases were found in the relative distribution of slow twitch (ST) fibres from 18 per cent to 25 per cent and fast twitch (FTa) fibres from 36 per cent to 45 per cent, and a decrease in FTb fibres from 46 per cent to 30 per cent. A proportionally equal reduction (approximately 18 per cent) in the cross sectiona...
Serteyn D, Deby-Dupont G, Pincemail J, Mottart E, Philippart C, Lamy M.Arachidonic acid cyclooxygenase metabolites, thromboxane B2 (TXB2), prostaglandin E2 (PGE2) and 6-keto-prostaglandin F1 (6-keto-PGF1) were measured in horses where anaesthesia was maintained with halothane. Two horses suffering from postanaesthetic myositis were compared with four normal horses. TXB2 and PGE2 levels were higher in mixed venous blood drawn from the myopathic horses. An increase of TXB2 and PGE2 levels appeared when myopathic horses were rolled into dorsal recumbency after a prolonged period of lateral recumbency. One hour after the end of anaesthesia, TXB2 had continued to incr...
Raub RH, Jackson SG, Baker JP.Nineteen weanling horses (average age = 147 d) were divided into exercised (EX; n = 10) and nonexercised (NEX; n = 9) groups, with age, sex and breed represented as equally as possible. The EX group was exercised on an automatic walker at a medium trot for up to 20 min, 5 d each week. Both groups were fed to meet 100% of their protein and 110% of their energy requirements (NRC, 1978). The EX group's diet was supplemented, on exercise days, with corn starch to meet the additional energy requirements for exercise. The experiment was conducted over a 111-d period. Body weight was measured at 10-d...
Jenkinson DM, Elder HY, Bovell DL.The condition of anhidrosis is described in this review, and the latest theories on the causal factors are explored. The evidence supports the hypothesis that anhidrosis is an inappropriate response to prolonged climatic stress (generally combined heat and high humidity), which can be evoked in a small (approximately 10 +/- 5%) proportion of the equine population. It is caused by gradual failure of the glandular secretory cell processes, initiated by desensitization and subsequent down-regulation of the cell receptors as a result of continued adrenaline-driven hyperactivity. It progresses thro...
Zhang FL, Zhang XY, Zhao JX, Zhu KX, Liu SQ, Zhang T, Sun YJ, Wang JJ, Shen W.Mongolian horses have been bred and used for labor and transport for centuries. Nevertheless, traits of testicular development in Mongolian horses have rarely been studied; particularly, studies regarding the transcriptional regulation characteristics of testicular development are lacking. In this paper, transcription specificity during testicular development in Mongolian horses is highlighted via a multispecies comparative analysis and weighted gene co-expression network analysis (WGCNA). Interestingly, the results showed that most genes were up-regulated in the testes after sexual maturity, ...
Richardson JD, Cripps PJ, Lane JG.Dental features are commonly expected to provide an accurate estimate of a horse's age. In this study the dentition of 434 thoroughbreds was photographed and the individual dental features documented, the true age of all the horses was known. For each dental feature the correlation with true age was determined. The eruption of the incisor teeth was the most consistent feature but it was not totally reliable. The presence of a hook on the upper corner incisor and Galvayne's groove proved to be of no value when estimating age and, of the attritional features studied, the dental star showed the h...
Mainguy-Seers S, Diaw M, Lavoie JP.While the prevalence of asthma is higher in boys than in girls during childhood, this tendency reverses at puberty, suggesting an effect of sex hormones on the disease pathophysiology. Fluctuations of asthma severity concurring with the estrus cycle are reported in women, but this phenomenon has never been investigated in mares to date. The objective of this exploratory study was to determine whether the estrus cycle modulates airway obstruction in severe equine asthma (SEA). Five mares with SEA during exacerbation of the disease were studied. The whole breath, expiratory and inspiratory resis...
Vanderwall DK, Silvia WJ, Fitzgerald BP.The reproductive tracts of nine thoroughbred mares were examined by ultrasound to determine the day of ovulation (day 0). Mares were fitted with intercavernous sinus cannulae on the day before the start of sample collection of pituitary venous effluent rich in oxytocin. Intercavernous sinus blood samples were collected for at least 36 h at 5 min intervals beginning at noon on day 13 (n = 2), day 15 (n = 5) or day 16 (n = 2) after ovulation. Concentrations of oxytocin and 13,14-dihydro-15-keto prostaglandin F2 alpha (PGFM) in plasma were determined by radioimmunoassay. Three high-magnitude surg...
Valberg SJ, Velez-Irizarry D, Williams ZJ, Pagan JD, Mesquita V, Waldridge B, Maresca-Fichter H.Horses have a slow rate of muscle glycogen repletion relative to other species for unknown reasons. Our aim was to determine the expression of glucose transporters () and genes impacting GLUT4 expression and translocation in the gluteal muscle. Five fit Thoroughbred horses performed glycogen-depleting exercises on high-starch (HS, 2869 g starch/day) and low-starch, high-fat diets (LS-HF, 358 g starch/d) with gluteal muscle biopsies obtained before and after depletion and during repletion. Muscle glycogen declined by ≈30% on both diets with little increase during repletion on LS-HF. Transcrip...
