The topic of muscle in horses encompasses the study of equine muscle structure, function, and physiology. Muscles in horses are responsible for movement, posture, and various metabolic processes. They are composed of muscle fibers that contract and relax to produce motion and generate force. Research in this area often focuses on muscle development, adaptation to exercise, and the impact of nutrition and training on muscle performance. Conditions such as muscle fatigue, injury, and disorders like equine exertional rhabdomyolysis are also explored. This page compiles peer-reviewed research studies and scholarly articles that investigate the anatomy, physiology, and clinical aspects of muscle in equine species.
Tappenbeck K, Hoppe S, Geburek F, Feige K, Huber K.By blocking the enteric nervous system (ENS) using tetrodotoxin (TTX), previous studies have documented the contractility-enhancing (CE) effects of lidocaine in equine intestinal smooth muscle (SM) at the level of SM cells and/or interstitial cells of Cajal (ICC). The present study examined the impact of ENS deactivation on CE lidocaine effects, and investigated the effects of lidocaine on ENS activity. TTX application did not affect the CE effects of lidocaine, indicating that these were not mediated by TTX-sensitive sodium channels. Application of TTX or ≥100 mg/L lidocaine reduced ENS a...
Boyko AR, Brooks SA, Behan-Braman A, Castelhano M, Corey E, Oliveira KC, Swinburne JE, Todhunter RJ, Zhang Z, Ainsworth DM, Robinson NE.Equine recurrent laryngeal neuropathy (RLN) is a bilateral mononeuropathy with an unknown pathogenesis that significantly affects performance in Thoroughbreds. A genetic contribution to the pathogenesis of RLN is suggested by the higher prevalence of the condition in offspring of RLN-affected than unaffected stallions. To better understand RLN pathogenesis and its genetic basis, we performed a genome-wide association (GWAS) of 282 RLN-affected and 268 control Thoroughbreds. Results: We found a significant association of RLN with the LCORL/NCAPG locus on ECA3 previously shown to affect body siz...
Kristensen L, Buhl R, Nostell K, Bak L, Petersen E, Lindholm M, Jacobsen S.The purpose of the study was to investigate whether acute strenuous exercise (1600- to 2500-m race) would elicit an acute phase response (APR) in Standardbred trotters. Blood levels of several inflammatory markers [serum amyloid A (SAA), haptoglobin, fibrinogen, white blood cell count (WBC), and iron], muscle enzymes [creatinine kinase (CK) and aspartate transaminase (AST)], and hemoglobin were assessed in 58 Standardbred trotters before and after racing. Hemoglobin levels increased and iron levels decreased 12 to 14 h after racing and haptoglobin concentrations, white blood cell counts, and i...
Reichel M, Martinek J.Distribution of the electrical field is very important to activate muscle and nerve cells properly. One therapeutic method to treat Recurrent Laryngeal Neuropathy (RLN) in horses can be performed by Functional Electrical Stimulation (FES). Current method to optimize the stimulation effect is to use implanted quadripolar electrodes to the musculus cricoarythenoideus dorsalis (CAD) and testing electrode configuration until best possible optimum is reached. For better understanding and finding of maximum possible activation of CAD a simulation model of the actual entire setting is currently in de...
Tappenbeck K, Schmidt S, Feige K, Naim HY, Huber K.Lidocaine is the most commonly chosen prokinetic for treating postoperative ileus in horses, a motility disorder associated with ischaemia-reperfusion injury of intestinal tissues. Despite the frequent use of lidocaine, the mechanism underlying its prokinetic effects is still unclear. Previous studies suggested that lidocaine altered cell membrane characteristics of smooth muscle cells. Therefore, the present study aimed to elucidate effects of lidocaine administration on characteristics of detergent-resistant membranes in equine jejunal smooth muscle. Lidocaine administration caused significa...
Pruitt BN.Rhabdomyolysis in equines occurs in horses due to physical overexertion or underlying pathologic myopathy. Methocarbamol is a muscle relaxant that can be used in equines to treat symptoms associated with Rhabdomyolysis. Methocarbamol is available as a solution for injection but is not commercially available as an oral suspension. This article focuses on the treatment of Tying-up caused by overexertion, and details the treatment of Rhabdomyolysis with an oral suspension that was prepared for a veterinarian by a compounding pharmacist.
Hyytiäinen HK, Mykkänen AK, Hielm-Björkman AK, Stubbs NC, McGowan CM.Although the majority of equine muscles have a mixed fibre type distribution indicative of diverse functional roles, the predominance of a fibre type can indicate the primary function of a muscle. The deep epaxial musculature has an important role in core spinal stability in humans, reflected as a predominantly muscle fibre type (MFT) I or postural fibre type. The fibre type of the deep epaxial musculature has not been determined in horses. The objective of the study was to determine the MFT distribution in selected muscles of thoracolumbar and hindlimb region of horses. This included deep epa...
Girard C, Macieira S.A 6-year-old Haflinger mare was presented with a history of recurrent hemoabdomen. On necropsy, a firm infiltrative multinodular yellow mass was observed in the wall of the posterior abdomen. Histopathologic examination revealed a proliferation of fibroblastic cells, which were positive for α-smooth muscle actin and vimentin.
Aranda-García S, Iricibar A, Planas A, Prat-Subiran JA, Angulo-Barroso RM.This study evaluates the separate effect and retention of 12-week traditional (TE) and horse (HE) exercise programs on physical function in healthy older participants (61 to 87 years old). Thirty-eight participants were randomly assigned to three groups: TE (n = 17), HE (n = 10), and control group (n = 11). TE and HE underwent a supervised exercise program (3 day/week). Maximal gait speed, muscle strength, and body balance were assessed at weeks 0, 12, and 16. Only TE and HE displayed significant improvements (P < .05) in knee extensor strength, and only HE had faster gait speed. Marginal b...
Mack SJ, Kirkby K, Malalana F, McGowan CM.Hereditary muscular disease is well described in racehorses, yet little is known about traumatic muscle disease associated with unaccustomed exercise or training. The objective of the study was to compare sedentary horses, racehorses undergoing training for the first time (unaccustomed exercise), and experienced racehorses during a training season (accustomed exercise) to investigate the effect of exercise and training on serum muscle enzyme activities and other variables. Horses were sampled prior to exercise for serum activities of aspartate amino transferase (AST), creatine kinase and other...
Hughes SB, Quan M, Guthrie A, Schulman M.The insulin-like growth factor system (insulin-like growth factor 1, insulin-like growth factor 2, insulin-like growth factor 1 receptor, insulin-like growth factor 2 receptor and six insulin-like growth factor-binding proteins) and insulin are essential to muscle metabolism and most aspects of male and female reproduction. Insulin-like growth factor and insulin play important roles in the regulation of cell growth, differentiation and the maintenance of cell differentiation in mammals. In order to better understand the local factors that regulate equine physiology, such as muscle metabolism a...
Navas De Solís C, Biscoe EW, Lund CM, Labbe K, Muñoz J, Farnsworth K.A 14-year-old Thoroughbred gelding was presented for chronic colic and weight loss. Transcutaneous and transrectal abdominal ultrasonography revealed distended, thickened small intestine with primary thickening of the muscularis and a focally more thickened loop with an echoic structure crossing the wall from the mucosa to the serosa. Visualization of diffuse thickening of the muscularis (muscular hypertrophy of the small intestine) and a focal lesion (pseudodiverticulum) helped clinicians make informed decisions. This case illustrates the importance of transabdominal and transrectal ultrasono...
Fernandez-Fuente M, Martin-Duque P, Vassaux G, Brown SC, Muntoni F, Terracciano CM, Piercy RJ.Several human and animal myopathies, such as malignant hyperthermia (MH), central core disease and equine recurrent exertional rhabdomyolysis (RER) are confirmed or thought to be associated with dysfunction of skeletal muscle calcium regulation. For some patients in whom the genetic cause is unknown, or when mutational analysis reveals genetic variants with unclear pathogenicity, defects are further studied through use of muscle histopathology and in vitro contraction tests, the latter in particular, when assessing responses to ryanodine receptor agonists, such as caffeine. However, since musc...
Komine M, Langohr IM, Kiupel M.Friesian horses have a perceived high rate of congenital or hereditary diseases, including megaesophagus, that may lead to choke and death. A retrospective study was performed to determine the prevalence and pathologic characteristics of esophageal disease in 852 horses, including 17 Friesians, that had been necropsied over a 6-year period at the Diagnostic Center for Population and Animal Health. Forty-two horses had grossly described esophageal lesions (25 muscular hypertrophy, 7 hemorrhage, 6 megaesophagus, 4 erosion/ulceration, 3 obstruction, 2 tears, 2 secondary neoplasms, 2 lymphoid patc...
Wagner AL, Urschel KL, Betancourt A, Adams AA, Horohov DW.To determine the effects of advanced age on whole-body protein synthesis and activation of the mechanistic target of rapamycin (mTOR) signaling pathway in skeletal muscle of horses. Methods: Six 22- to 26-year-old (aged) and six 7- to 14-year-old (mature) horses. Methods: Whole-body protein synthesis was measured with a 2-hour primed constant infusion of (13)C sodium bicarbonate, followed by a 4-hour primed constant infusion of 1-(13)C phenylalanine. After the infusions, a biopsy specimen was obtained from a gluteus medius muscle and activation of protein kinase B (Akt), p70 riboprotein S6 kin...
Wijnberg ID, Hardeman LC, van der Meij BR, Veraa S, Back W, van der Kolk JH.Therapeutic reduction of the activity of the deep digital flexor (DDF) muscle may play a role in treatment of laminitic horses. Clostridium botulinum toxin type A induces reduced muscle activity and has a spasmolytic effect in horses. In this study, the effectiveness of 200 IU C. botulinum toxin type A on reduction of DDF muscle activity was measured in seven healthy, sound, adult Royal Dutch sport horses. C. botulinum toxin type A was injected using ultrasound and electromyographic (EMG) guidance. The effectiveness was assessed by interference pattern analysis (IPA) and motor unit action pote...
Cullimore AM, Lester GD, Swindells KL.A 7-year-old Thoroughbred gelding presented with muscle fasciculation, reluctance to move, profuse sweating, tachycardia, tachypnoea and a localised, unilateral swelling on the muzzle. History and physical examination were suggestive of snake envenomation. Methods: A sandwich ELISA for the detection of snake venom was performed on serum and urine samples. Results: The test performed on urine confirmed a diagnosis of tiger snake envenomation. Conclusions: The response to treatment with antivenom and supportive medical therapy was excellent.
Tappenbeck K, Hoppe S, Reichert C, Feige K, Huber K.The purpose of the study was to compare the contractility-enhancing effects of lidocaine in equine jejunal circular (CSM) and longitudinal smooth muscle (LSM) in vitro. In previous studies, more pronounced effects of lidocaine were observed in ischaemia-reperfusion (IR) injured smooth muscle. Therefore in this study, effects were examined in both non-injured control tissues and tissues challenged by a defined, artificial IR injury. Isometric contractile performance of CSM and LSM, assessed by frequency (F), amplitude (A) and mean active force (MAF) of contractions, was defined as contractility...
Ball BA, Scoggin KE, Troedsson MH, Squires EL.Biological effects of prostaglandin E2 are mediated via one of four receptors designated EP1, EP2, EP3 and EP4 which are encoded by separate genes. In general, EP1 and EP3 induce smooth muscle contraction whereas EP2 and EP4 induce smooth muscle relaxation. The objective of the current study was to characterize the expression of the genes for PGE2 receptors (EP2 and EP4) in the horse oviduct based upon immunohistochemistry (IHC) and quantitative PCR (qPCR). Oviductal tissue was collected from mares at estrus (n=5), at 5 days post-ovulation (n=4), and from prepubertal mares (n=5). Isthmic and a...
Manikowska F, Jóźwiak M, Idzior M, Chen PJ, Tarnowski D.Hippotherapy has been shown to produce beneficial effects by improving the most difficult motor functions, such as sitting, running, jumping, coordination, as well as balance and muscle strength in children with motor developmental delays. The aim of this study was to analyze the effect of hippotherapy on spatiotemporal parameters of gait in cerebrally palsied children. Methods: 16 ambulatory cerebrally palsied children (GMFCS Level I-III; Female: 10, Male: 6; Age: 5.7-17.5 years old) qualified for hippotherapy were investigated. Basic spatiotemporal parameters of gait, including walking speed...
Riis KH, Harrison AP, Riis-Olesen K.Assessment of muscle function after an injury or during recovery is of great importance in the veterinary field. Accelerometry, bioimpedance analysis and mechanomyography/acoustic myography have been used to assess human muscular problems, but have not been applied to the veterinary clinic. We report the clinical use of these techniques in a 12-year-old Danish Warmblood horse presenting with recurring and shifting lameness. Acoustic myography, assessing both the amplitude and frequency of active muscles, was employed to locate the specific area of muscle injury, the right hip, which exhibited ...
Davis TZ, Stegelmeier BL, Lee ST, Green BT, Hall JO.Rayless goldenrod (Isocoma pluriflora) sporadically poisons horses and other livestock in the southwestern United States. Similar to livestock poisoning by white snakeroot (Ageratina altissima) in the midwestern United States, previous research suggests that benzofuran ketones (BFK: tremetone, dehydrotremetone, 6-hydroxytremetone, and 3-oxyangeloyl-tremetone) are responsible for the toxicity of rayless goldenrod. However, experimental reproduction of rayless goldenrod-induced disease and detailed descriptions of poisoning in horses with known concentrations of tremetone and other BFK has not b...
Giagazoglou P, Arabatzi F, Kellis E, Liga M, Karra C, Amiridis I.Reaction time and muscle activation deficits might limit the individual's autonomy in activities of daily living and in participating in recreational activities. The aim of the present study was to assess the effects of a 14-week hippotherapy exercise program on movement reaction time and muscle activation in adolescents with intellectual disability (ID). Nineteen adolescents with moderate ID were assigned either to an experimental group (n=10) or a control group (n=9). The experimental group attended a hippotherapy exercise program, consisting of two 30-min sessions per week for 14 weeks. Rea...
Wagner AL, Urschel KL, Lefta M, Esser KA.To determine the effect of biopsy collection depth on the postprandial activation of mammalian target of rapamycin (mTOR) signaling factors, particularly protein kinase B, ribosomal protein S6 kinase, ribosomal protein S6, and eukaryotic initiation factor 4E binding protein 1 in middle-aged horses. Methods: 6 healthy Thoroughbred mares (mean ± SD age, 13.4 ± 3.4 years). Methods: Horses were fed a high-protein feed at 3 g/kg. Sixty minutes after horses were fed, the percutaneous needle biopsy technique was used to collect biopsy specimens from the gluteus medius muscle at 6, 8, and 10 cm belo...
McKenzie RK, Gibson IR, Ritmeester A.Three weanling Thoroughbred fillies were presented during autumn with depression, muscle rigidity and, in one case, colic symptoms and cardiovascular shock. Results: All fillies had abnormal physical examinations that included elevated heart rates and respiratory rates coupled with muscle rigidity through the back and rump. Biochemistry revealed markedly elevated creatinine kinase and aspartate aminotransferase which indicated a myopathy. Methods: All three horses were diagnosed with presumptive equine atypical myopathy. The horses received supportive therapy as per the literature available at...
Radtke CL, Nino-Fong R, Esparza Gonzalez BP, Stryhn H, McD￮ LA.To characterize equine muscle tissue- and periosteal tissue-derived cells as mesenchymal stem cells (MSCs) and assess their proliferation capacity and osteogenic potential in comparison with bone marrow- and adipose tissue-derived MSCs. Methods: Tissues from 10 equine cadavers. Methods: Cells were isolated from left semitendinosus muscle tissue, periosteal tissue from the distomedial aspect of the right tibia, bone marrow aspirates from the fourth and fifth sternebrae, and adipose tissue from the left subcutaneous region. Mesenchymal stem cells were characterized on the basis of morphology, ad...
Massey CA, Walmsley GL, Gliddon TP, Piercy RJ.Histopathological interpretation of semimembranosus muscle samples from an adult Warmblood mare with clinical signs suggestive of exertional rhabdomyolysis and intermittent mild elevations in muscle enzyme activities revealed abundant sarcoplasmic vacuoles in all fibre-types containing fine, apparently proteinaceous debris. Vacuolar contents stained lightly with PAS, but did not appear to contain amylopectate, lipid or acid phosphatase and their periphery was unstained with dystrophin immunohistochemistry. Electron microscopy revealed that vacuoles were not membrane bound. No vacuoles were det...
Peters LW, Smiet E, de Sain-van der Velden MG, van der Kolk JH.In particular branched-chain amino acids might limit muscle protein loss in pathological conditions. Little is known on basic amino acid utilization of muscle in horses. Objective: To assess amino acid utilization by the hindlimb of horses at rest and following low intensity exercise. ANIMALS & METHODS: Amino acid uptake by the hindlimb was investigated using the arteriovenous difference technique. Blood from six warmblood mares (mean age 12 ± 3 (SD) years and weighing 538 ± 39 kg) was collected simultaneously from the (transverse) facial artery and from the caudal vena cava. Food was wi...
Bedford HE, Valberg SJ, Firshman AM, Lucio M, Boyce MK, Trumble TN.To characterize clinical findings, outcomes, muscle characteristics, and serum or muscle concentrations of α-tocopherol for horses with vitamin E-responsive signs of muscle atrophy and weakness consistent with signs of equine motor neuron disease (EMND). Methods: Retrospective case-control study. Methods: 8 affected (case) adult horses with acute (n = 3) or chronic (5) gross muscle atrophy that improved with vitamin E treatment and 14 clinically normal (control) adult horses with adequate (within reference range; 8) or low (6) muscle concentrations of α-tocopherol. Methods: Medical records w...
Nieto JE, Morales B, Yamout SZ, Stanley SD, Harmon FA, Snyder JR.To determine the response to neostigmine of the contractile activity of the jejunum and pelvic flexure and the effects of a continuous rate infusion (CRI) of neostigmine in horses. Methods: 7 adult horses and tissue from 12 adult horses. Methods: A CRI of neostigmine (0.008 mg/kg/h) or placebo was administered to 6 horses in a crossover study design. Gastric emptying was evaluated by the acetaminophen test. The frequency of defecation and urination and the consistency and weight of feces were recorded throughout the experiment. The effect of neostigmine on smooth muscle contractile activity wa...
Hodgson DR, Rose RJ, DiMauro J, Allen JR.The effects of training on skeletal muscle composition were studied in four Standardbred geldings given a seven week submaximal treadmill training programme. Before the start of training, muscle biopsies were collected from the left middle gluteal muscle for the determination of muscle fibre types, oxidative capacity and capillary numbers using histochemical techniques. The concentrations of citrate synthase, 3-hydroxyacyl-CoA dehydrogenase (HAD), lactate dehydrogenase and total muscle glycogen were measured using fluorometric methods. Muscle biopsy samples were repeated after one, three, five...
Kim JS, Hinchcliff KW, Yamaguchi M, Beard LA, Markert CD, Devor ST.The purpose of the present study was to determine the age-related changes in myosin heavy chain (MHC) composition and muscle oxidative and glycolytic capacity in 18 horses ranging in age from two to 30 years. Muscle samples were collected by excisional biopsy of the semimebranosus muscle. MHC expression and the key enzymatic activities were measured. There was no significant correlation between horse age and the proportions of type-IIA and type-IIX MHC isoforms. The percentage of type-I MHC isoforms decreased with advancing age. Muscle citrate synthase activity decreased, whereas lactate dehyd...
Malone ED, Brown DR, Trent AM, Turner TA.To characterize the response of equine jejunal smooth muscle to adrenergic and cholinergic mediators. Methods: Evaluation of myogenic responses, using an in vitro model. Methods: Intestinal tissues were obtained from horses without gastrointestinal tract disorders or systemic disease. Methods: Baseline myogenic tone and amplitude and frequency of contraction were determined for suspended jejunal muscle strips. The level of adrenergic and cholinergic regulation was assessed, using atropine and adrenoceptor antagonists. The response of the muscles to norepinephrine was characterized, using adren...
Aman JE, Valberg SJ, Elangovan N, Nicholson A, Lewis SS, Konczak J.Cerebellar Purkinje cell axonal degeneration has been identified in horses with shivering but its relationship with abnormal hindlimb movement has not been elucidated. Objective: To characterise surface electromyographic (sEMG) hindlimb muscle activity in horses with shivering, correlate with clinical scores and examine horses for Purkinje axonal degeneration. Methods: Descriptive controlled clinical study. Methods: The hindlimb of seven shivering and six control draught horses were clinically scored. Biceps femoris (BF), vastus lateralis (VL), tensor fasciae latae and extensor digitorum longu...
McKenzie EC, Eyrich LV, Payton ME, Valberg SJ.A previous report suggests a substantial incidence of exertional rhabdomyolysis (ER) in Arabian horses performing endurance racing. This study compared formalin histopathology and clinical and metabolic responses to a standardised field exercise test (SET) between Arabians with and without ER. Arabian horses with (n = 10; age 15.4 ± 5.6 years) and without (n = 9; 12.9 ± 6.1 years) prior ER were stall-rested for 24-48 h, after which paired ER and control horses were fitted with a telemetric ECG and performed a 47 min submaximal SET. Plasma glucose, lactate, electrolyte and...
Rakestraw PC, Snyder JR, Woliner MJ, Sanders KM, Shuttleworth CW.To evaluate the role of nitric oxide (NO), vasoactive intestinal peptide (VIP), and a transmitter acting through an apamin-sensitive mechanism in mediating inhibitory transmission in the equine jejunal circular muscle, and to determine the distribution of VIP-and NO-producing nerve fibers in the myenteric plexus and circular muscle. Methods: Circular muscle strips were suspended in tissue baths containing an oxygenated modified Krebs solution and attached to isometric force transducers. Responses to electrical field stimulation (EFS), tetrodotoxin, the NO antagonists L-N-nitro-arginine-methyl-...
Wilson JA, Kronfeld DS, Gay LS, Williams JH, Wilson TM, Lindinger MI.Sarcoplasmic reticulum (SR) responses to repeated sprints and to physical conditioning were studied in 10 Quarter Horses. Exercise tests (four repeated sprints on a treadmill) were conducted before and after 12 wk of sprint conditioning. Muscle samples from the middle gluteal muscle were taken before and after each exercise test, and SR vesicles were isolated. Calcium uptake was determined spectrophotometrically using antipyrylazo III, and Ca2+-ATPase activity was determined using an enzyme-linked optical assay. Conditioning increased calcium uptake rate and Ca2+-ATPase activity by 14 and 38%,...
Reed SM, Hegreberg GA, Bayly WM, Brown CM, Paradis MR, Clemmons RM.A severe and progressive neuromuscular disorder accompanied by clinical, electrophysiological, and pathological features resembling human dystrophia myotonica was observed in three foals. This disorder was apparent as early as 1 month of age and involved progressive skeletal muscle dysfunction, initially characterized by proximal muscle hypertrophy and hypertonicity with subsequent muscle stiffness, weakness, and atrophy. Multisystem involvement was manifested in one case by testicular hypoplasia, early cataract formation, and borderline glucose intolerance. Prolonged dimpling of these large r...
Rietbroek NJ, Dingboom EG, Schuurman SO, Hengeveld-van der Wiel E, Eizema K, Everts ME.To determine whether postnatal development of oxidative capacity and capillary supply of skeletal muscle is affected by various movement regimens in horses. Methods: 35 foals. Methods: Dutch Warmblood foals were allocated into 3 groups (box stall rest, box stall rest with training, and free pasture exercise). Training comprised an increasing number of gallop sprints from 1 week after birth to 22 weeks of age. From 22 to 48 weeks, the 3 groups were combined and allowed to exercise freely. Capillary supply (diffusion index [ie, area supplied by 1 capillary]), citrate synthase (CS) activity, and ...
Valentine BA.Gross and histopathologic evaluation of skeletal muscle was performed in 229 equids (217 horses, 8 ponies, 3 donkeys, and 1 mule) 1 year of age or older undergoing postmortem examination at Oregon State University in a 2.5-year period. Animals were evaluated for grossly evident muscle lesions, and muscle samples were fixed in formalin, processed routinely, and stained with hematoxylin and eosin (HE) and periodic acid-Schiff (PAS) for glycogen. Muscle lesions were detected in 149 animals (65%). Chronic myopathic change (excessive fiber size variation and internal nuclei) was evaluated in horses...
Wijnberg ID, Sleutjens J, Van Der Kolk JH, Back W.There has been growing interest in training techniques with respect to the head and neck position (HNP) of the equine athlete. Little is known about the influence of HNP on neuromuscular transmission in neck muscles. Objective: To test the hypothesis that different HNPs have effect on single fibre (SF), quantitative electromyographic (QEMG) examination and muscle enzyme activity directly after moderate exercise. Methods: Seven Warmblood horses were studied using a standard exercise protocol in 5 HNPs: HNP1: unrestrained; HNP2: neck raised; bridge of nose around the vertical; HNP4: neck lowered...
Hinchcliff KW, Lauderdale MA, Dutson J, Geor RJ, Lacombe VA, Taylor LE.High intensity exercise is associated with production of energy by both aerobic and anaerobic metabolism. Conditioning by repeated exercise increases the maximal rate of aerobic metabolism, aerobic capacity, of horses, but whether the maximal amount of energy provided by anaerobic metabolism, anaerobic capacity, can be increased by conditioning of horses is unknown. We, therefore, examined the effects of 10 weeks of regular (4-5 days/week) high intensity (92+/-3 % VO2max) exercise on accumulated oxygen deficit of 8 Standardbred horses that had been confined to box stalls for 12 weeks. Exercise...
Zielińska P, Soroko-Dubrovina M, Dudek K, Ruzhanova-Gospodinova IS.The reason for undertaking this study was to investigate soft tissue response to high-intensity laser therapy (HILT) by measuring changes in skin surface temperature and longissimus dorsi muscle tone in the thoracolumbar back area in Thoroughbreds with back pain and diagnosed with and without Kissing Spines Syndrome (KSS). Thoroughbreds aged 3-4 years with clinically presented back pain underwent a radiological examination (to assess a lack or presence of KSS) and longissimus dorsi muscle palpation (to assess muscle tone and pain degree). The subjects were divided into two groups, those with K...
Much ML, Leatherwood JL, Zoller JL, Bradbery AN, Martinez RE, Keegan AD, Lamprecht ED, Wickersham TA.Stock-type mares (498 ± 9 kg BW; 12 ± 7 yr) were used in a completely randomized design for 56 d to test the hypothesis that concentrate fortification improves apparent digestion and enhances lean mass over the topline. Horses were stratified by age, BW, and BCS and randomly assigned to either a custom pelleted concentrate (CON; = 13), or an iso-caloric, iso-nitrogenous pellet that included amino acid fortification, complexed trace minerals, and fermentation metabolites (FORT; = 10). Concentrate was offered at a total 0.75% BW/d (as-fed) twice daily, and diets were designed to meet or exce...
Krueger CR, Ruple-Czerniak A, Hackett ES.In horses undergoing celiotomy for acute gastrointestinal pain, identification of variables correlating with lesion severity and location, and survival provide veterinarians and owners with information that aids in making informed decisions regarding appropriate treatment. Muscle enzyme activity is often increased in horses undergoing celiotomy for acute gastrointestinal pain and it is not known if muscle enzyme activity increase is specific to lesion type or impacts prognosis for survival. The objective of this study was to evaluate the relationship of pre-operative increase in muscle enzyme ...
Kitaoka Y, Endo Y, Mukai K, Aida H, Hiraga A, Takemasa T, Hatta H.To evaluate the effects of a single incremental exercise test (IET) on mRNA expression and protein content of monocarboxylate transporter (MCT) 1 and MCT4 in the gluteus medius muscle of Thoroughbreds. Methods: 12 Thoroughbreds (6 males and 6 females; age, 3 to 4 years). Methods: Horses underwent an IET before and after 18 weeks of high-intensity exercise training (HIT). Horses were exercised at 90% of maximal oxygen consumption for 3 minutes during the initial 10 weeks of HIT and 110% of maximal oxygen consumption for 3 minutes during the last 8 weeks of HIT. Gluteus medius muscle biopsy spec...
Dietrich J, Handschuh S, Steidl R, Böhler A, Forstenpointner G, Egerbacher M, Peham C, Schöpper H.As the longissimus dorsi muscle is the largest muscle in the equine back, it has great influence on the stability of the spine and facilitates proper locomotion. The longissimus muscle provides support to the saddle and rider and thereby influences performance in the horse. Muscular dysfunction has been associated with back disorders and decline of performance. In general, muscle function is determined by its specific intramuscular architecture. However, only limited three-dimensional metrical data are available for the inner organisation of the equine longissimus dorsi muscle. Therefore, we a...
Gottlieb M, Essén-Gustavsson B, Lindholm A, Persson SG.Circulatory and muscle metabolic responses were studied in 10 horses which all performed incremental draught work at a low trotting speed on a treadmill (D-test) and also exercise with gradually increasing velocities (S-test). Exercise was continued until the horses could no longer maintain the weights above the floor or maintain speed trotting without changing gait to a gallop. Muscle biopsies were taken from the gluteus and the semitendinosus muscles before, and immediately after, exercise. The heart rate (HR) increased linearly with both increasing draught resistance and velocity and reache...
Manao G, Camici G, Stefani M, Berti A, Cappugi G, Liguri G, Nassi P, Ramponi G.Acylphosphatase was purified from horse muscle by a new procedure involving an affinity chromatography step and subsequent ion-exchange chromatography. This procedure was considerably milder than the preceding one, gave an overall yield of about 60% of activity and permitted isolation of three molecular forms with acylphosphatase activity. All these enzymatic forms are tightly bound to Sepharose 4B-linked anti-horse muscle acylphosphatase antibodies. Two of these forms (Ho1 and Ho3) are present in larger amounts: Ho1 corresponds to the enzyme purified according to the older procedure; this enz...
Hunt LM, Valberg SJ, Steffenhagen K, McCue ME.There are few detailed reports describing muscular disorders in Warmblood horses. Objective: To determine the types of muscular disorders that occur in Warmblood horses, along with presenting clinical signs, associated risk factors and response to diet and exercise recommendations, and to compare these characteristics between horses diagnosed with polysaccharide storage myopathy (PSSM), those diagnosed with a neuromuscular disorder other than PSSM (non-PSSM) and control horses. Methods: Subject details, muscle biopsy diagnosis and clinical history were compiled for Warmblood horses identified ...
Siciliano PD, Parker AL, Lawrence LM.The effect of vitamin E intake on indicators of muscle integrity was studied in exercised horses. Nineteen horses were blocked by sex and then assigned to one of three diets: no supplemental vitamin E (BASAL), BASAL plus 80 IU of supplemental vitamin E/kg DM (80), or BASAL plus 300 IU of supplemental vitamin E/kg DM (300). The BASAL diet contained less than 44 IU of vitamin E/kg DM, but it was adequate in all other nutrients. During the 90-d treatment period, horses were exercised 5 d/wk; in addition, serum and middle gluteal muscle alpha-tocopherol concentrations were measured at 0, 30, and 9...
Valberg SJ, Carlson GP, Cardinet GH, Birks EK, Jones JH, Chomyn A, DiMauro S.Although exertional myopathies are commonly recognized in horses, specific etiologies have not been identified. This is the first report in the horse of a deficiency of Complex I respiratory chain enzyme associated with profound exercise intolerance. Physical examination, routine blood tests, endoscopy, and ultrasonograms of the heart and iliac arteries were unremarkable. With slow, incremental exercise (speeds 1.5-7 m/s), the Arabian mare showed a marked lactic acidosis, increased mixed venous PVO2, and little change in oxygen consumption. Muscle biopsies contained large accumulations of mito...
McCue ME, Anderson SM, Valberg SJ, Piercy RJ, Barakzai SZ, Binns MM, Distl O, Penedo MC, Wagner ML, Mickelson JR.The GYS1 gene mutation that is causative of Type 1 Polysaccharide Storage Myopathy (PSSM) has been identified in more than 20 breeds of horses. However, the GYS1 mutation frequency or Type 1 PSSM prevalence within any given breed is unknown. The purpose of this study was to determine the frequency of the GYS1 mutation and prevalence of genetic susceptibility to Type 1 PSSM in selected breeds from Europe and North America. The GYS1 mutation was detected in 11 breeds, including, in order of increasing allele frequency, Shires, Morgans, Appaloosas, Quarter Horses, Paints, Exmoor Ponies, Saxon-Thu...
Prieto D, Simonsen U, Martín J, Hernández M, Rivera L, Lema L, García P, García-Sacristán A.The distribution of acetylcholinesterase (AChE)-positive nerve fibers and cells, as well as the effects of acetylcholine (ACh) on ureteral smooth muscle and small resistance arteries were investigated in the equine ureter by means of histochemical, classic organ baths and myograph techniques. AChE-positive nerve fibers were widely distributed throughout the ureteral wall forming muscular, subepithelial and perivascular nerve plexuses, whose density was highest at the intravesical ureter. AChE-positive nerve cells were also identified grouped as adventitial or intramural ganglia. ACh increased ...
Valberg S, Häggendal J, Lindholm A.Six horses with a history of recurrent exertional rhabdomyolysis (RER) and 7 control horses performed both a 55-min submaximal and later a 10-min near-maximal exercise test on a treadmill. Blood samples were obtained during exercise and gluteus medius muscle biopsies were obtained before and immediately after each exercise test and at 24 h after completion of the submaximal test. Rhabdomyolysis was developed by 3 of 6 RER horses during submaximal exercise and in 1 of the RER horses during near-maximal exercise. Concentrations of potassium, glucose, free fatty acids, ammonia, lactate, cortisol,...
Reeta Pösö A, Hyyppä S.To test whether, in horses, the concentration of muscle glycogen can be influenced by increasing the uptake of glucose into the muscle cells or by providing a gluconeogenic precursor, 9 trained half-bred riding horses performed on a treadmill a 1.5 h competition exercise test (CET). Each horse performed CET 3 times and 30 min after CET, each was given one of the following solutions: isotonic glucose-electrolyte (GE) solution, GE supplemented with 50 g leucine (GEL) to increase insulin secretion, or GE supplemented with 200 ml propionic acid (GEP), a gluconeogenic precursor. Administration of G...
Nieto JE, Rakestraw PC, Snyder JR, Vatistas NJ.To evaluate effects of erythromycin, lidocaine, and metoclopramide on smooth muscle of the pyloric antrum (PA), proximal portion of the duodenum (PD), and middle portion of the jejunum (MJ) of horses. Sample Population-Strips of smooth muscle from 7 horses. Methods: Isolated muscle strips were suspended in a bath and attached to isometric force transducers. Once stable spontaneous contractions were observed, agents were added. Isometric stress responses were compared with the amplitude of spontaneous contractions. Results: A single dose of erythromycin to the PA increased contractile amplitude...
Meira CT, Curi RA, Farah MM, de Oliveira HN, Béltran NA, Silva JA, Mota MD.Selection of Quarter Horses for different purposes has led to the formation of lines, including racing and cutting horses. The objective of this study was to identify genomic regions divergently selected in racing line of Quarter Horses in relation to cutting line applying relative extended haplotype homozygosity (REHH) analysis, an extension of extended haplotype homozygosity (EHH) analysis, and the fixation index (F ST) statistic. A total of 188 horses of both sexes, born between 1985 and 2009 and registered at the Brazilian Association of Quarter Horse Breeders, including 120 of the racing ...
Fintl C, Hudson NP, Handel I, Pearson GT.Slow waves are rhythmic pacemaker currents generated by the gastrointestinal pacemaker cells, the interstitial cells of Cajal, and represent the rate-limiting step for small intestinal smooth muscle contractions. Therefore, factors that affect slow wave activity may also influence contractile activity. It is not known how temperature changes may influence slow wave activity in the horse. This could be of relevance during colic surgery if cooling of exposed intestine resulted in reduced slow wave activity potentially exacerbating post operative ileus. Objective: To evaluate the effect of temper...
Davis TZ, Stegelmeier BL, Lee ST, Green BT, Hall JO.Rayless goldenrod (Isocoma pluriflora) sporadically poisons horses and other livestock in the southwestern United States. Similar to livestock poisoning by white snakeroot (Ageratina altissima) in the midwestern United States, previous research suggests that benzofuran ketones (BFK: tremetone, dehydrotremetone, 6-hydroxytremetone, and 3-oxyangeloyl-tremetone) are responsible for the toxicity of rayless goldenrod. However, experimental reproduction of rayless goldenrod-induced disease and detailed descriptions of poisoning in horses with known concentrations of tremetone and other BFK has not b...
