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.
Bowen JM.Characteristics of minature end-plate potentials (MEPP) of isolated external intercostal muscle preparations of 7 mammalian species (dog, cat, pig, horse, cow, and goat) including 1 marsupial (opossum, Didelphis marsupialis) were determined with intracellular microelectrodes. Mean amplitude (+/- standard error of MEPP for all species was 0.60 +/- 0.06 mV, and the range was 0.28 mV (opossum) to 1.07 mV (pig). Amplitude was inversely correlated (P less than 0.01) with muscle fiber diameter which ranged from 93 mum (opossum) to 51 mum (pig). Mean values for rise time, half-decay time, and frequen...
Bowen JM, McMullan WC.The neurally evoked contractile response of the upper lip muscles of horses anesthetized with halothane was used to evaluate the neuromuscular blocking property of oxytetracycline which was administered intravenously at total dose rate of 21 to 28 mg/kg. This dose rate did not alter the contractile response which had a mean control value (and standard error; SE) of 1.76 plus or minus 0.22 kg. Arterial blood pressure was not affected by these dose rates. Neuromuscular blocking effect of the antibiotic occurred when it was administered during partial neuromuscular blockade which had been induced...
Anderson MG.A group of clinically normal horses was subjected to controlled strenuous exercise. Elevated serum concentrations of lactic dehydrogenase, aldolase and creatine kinase were observed after exercise but no significant change in serum glutamic-oxalacetic transaminase was noted. These changes were reduced by repeated exposure to exercise suggesting that measurement of serum enzyme elevations, particularly creatine kinase, might be a useful index of fitness in the horse. Administration of prednisolone prior to exercise also reduced these changes. Since the serum enzyme concentrations had returned t...
Ramponi G, Manao G, Camici G, White GF.It has been shown that horse muscle acylphosphatase is inhibited by pyridoxal 5'-phosphate and that the inhibition is pH dependent, reversible and competitive with respect to substrate binding. Spectral analysis on the EI complex demonstrates the presence of a Schiff base. Reduction of the pyridoxal 5'-phosphate-inhibited enzyme with sodium borohydride, followed by amino acid analysis, produces a diminution of the free lysine peak and the appearance of a new peak corresponding to epsilon-pyridoxyllysine. The results suggest that there is at least one NH2-lysyl residue of horse muscle acylphosp...
Lindholm A, Johansson HE, Kjaersgaard P.LINDHOLM, A., H.-E. JOHANSSON & P. KJÆRSGAARD: Acute rhabdomyolysis (“tying-up”) in standardbred horses. A morphological and biochemical study. Acta vet. scand. 1974, 15, 325–339. — Morphological, biochemical and histochemical changes were studied in muscle needle biopsy specimens (gluteus medius) from 59 standardbred trotters with acute clinical symptoms of the “tying-up” disease. All horses had increased levels of serum enzymes SGOT and SCPK. The biopsy specimens were taken at various intervals after onset of clinical symptoms (1–4 hrs., 18–24 hrs. and 2–20 days). Ry light...
Lindholm A, Piehl K.LINDHOLM, ARNE and KARIN PIEHL: Acta vet. scand. 1974, , 287–309. — Measurements of metabolites, electrolytes, water, RNA and protein concentrations, the activity of certain muscle enzymes (SDH and PFK) and muscle fibre composition were made on biopsy specimens from the gluteus medius muscle of 68 standardbred horses, ½ to 8 years old. The muscle fibres were classified in 3 major categories, slow twitch (ST), fast twitch and high oxidative (FTH) and fast twitch (FT) fibres. The percentage of FTH fibres was higher after the age of 4 years, averaging 54 %. ST fibres comprised 24 % and this...
Lindholm A, Saltin B.LINDHOLM, ARNE and BENGT SALTIN: The physiological and biochemical response of standardbred horses to exercise of varying speed and duration. Acta vet. scand. 1974, 15, 310–324. — Welltrained standardbred horses were studied to examine the metabolic response to excercise of various speeds and duration. Comparisons between interval (400, 700, 1,000 and 2,000 m) and continuous trotting (1 hr., 2 hrs.) and racing were made. Muscle and rectal temperatures were recorded before and immediately after each work bout. Heart rate was linearly related to trotting speed, and maximal heart rate (240 be...
Gunn HM.The research article is a study about neurogenic atrophy in the dorsal cricoarytenoid muscle of horses. It examines whether this condition is present prenatally in horses and studies the patterns […]
Yamaguchi M, Miyazawa Y, Sekine T.Myosin was prepared from smooth muscle of horse esophagus in good yield
(about 15 ° mg/Ioo g tissue) and was designated myosin S. Its properties were compared
with those of myosin A from skeletal muscle.
The ratio of the absorption of myosin S at 280 nm to that at 26o nm was about
1.8, and the amount of contaminating phosphorus was only o.91 g/io 5 g of myosin S,
indicating that the latter is free of nucleic acid. The purity of this protein was examined
by ultracentrifugation, gel filtration in the presence of 0.5 M KC1 and 6 M urea and
chromatography on DEAE-cellulose columns. These e...
Van den Oord AH, Wesdorp JJ, Van Dam AF, Verheij JA.In commercial samples of equine myoglobin and samples of equine and bovine myoglobin prepared in the laboratory, a small amount of the protein was present as an aggregate. The presence of the myoglobin aggregate could be demonstrated by gel filtration on Sephadex G-100 Superfine, which also provided a means of isolating it. Gel filtration on Sephadex G-100 showed the molecular weights of the equine and bovine moyglobin aggregates to be about 35000 and 34000 respectively, thus supporting the hypothesis that they are dimers. This was confirmed for the equine myoglobin by ultracentrifugation meas...
AZZONE GF.In a series of model reactions, it is shown that residues
of ~-aminoacids may be inserted by a particular rearrangement into certain carboxyl or carbonylamido
groups. Repeated insertion results in the formation of
a peptide derivative. It is concluded that natural peptides or proteins must not necessarily be formed by head
to tail combination of aminoacids, Other implications of
the new principle are discussed.
Gomes ÉR, Felix LA, Gonzaga LWF, da Silva NFD, Soares BCF, de Almeida JVFC, Souza GP, Pereira RN, Taffarel MO, Ferrante M.The combination of detomidine and midazolam may provide safer sedation with muscle-relaxant effects, which are particularly necessary during standing procedures. Unassigned: Thus, the objective of this study was to evaluate the sedative and muscle-relaxant effects of the detomidine/midazolam combination in horses through a pharmacodynamic study. Unassigned: Five horses were used and subjected to four experimental protocols: 15 µg/kg of detomidine (D15); a combination of detomidine (15 µg/kg) with 25 µg/kg (DM25), 50 µg/kg (DM50), or 75 µg/kg (DM75) of midazolam administered intravenously....
Kawashima M, Kuroda T, Minamijima Y, Yamazaki Y, Mita H, Nomura M, Ohta M.Remimazolam (RMZ) is a new short-half-life benzodiazepine used in humans. We compared the pharmacokinetics and sedative effects of RMZ with those of midazolam (MDZ) in Thoroughbred horses. Six Thoroughbreds received a single IV dose of RMZ 0.05 mg/kg or MDZ 0.05 mg/kg in a randomized crossover design. Blood samples were collected, and plasma RMZ and MDZ concentrations were measured by LC-MS/MS. Plasma concentrations were analyzed by using non-compartmental analysis and a nonlinear mixed effect model. The half-life of RMZ (0.77 ± 0.15 h) was significantly shorter than that of MDZ (3....
Söderroos D, Stefánsdóttir GJ, Ragnarsson S, Gunnarsson V, Jansson A.Weight-carrying capacity is important in riding horses both for performance and welfare, yet there is no standardized method to estimate individual horses' weight-carrying capacity. This study investigated the correlation between the physiological response during a (i) standardized incremental exercise test (SET) on a treadmill and a (ii) ridden incremental weight-carrying exercise test (WET). Sixteen horses (15 ± 3 years) performed both tests, including four steps with increased speed or weight load, respectively. Body weight ratio (BWR) in the WET was 20%, 25%, 30%, and 35% in each st...
Wang J, Li Z, Li L, Wang R, Ma S, Su Y, Shan D, Huang Q.Kazakh horses are renowned for their endurance and adaptability, with distinct muscle groups such as the longissimus dorsi (LD) and biceps femoris (BF) muscles serving specialized functions. However, the molecular mechanisms underlying the functional specialization of these muscles in Kazakh horses remain poorly understood. This study aims to address this gap by utilizing single-cell RNA sequencing (scRNA-seq) to investigate the transcriptomic differences between these muscle groups, with a focus on understanding their molecular adaptations. Our analysis revealed that the BF muscle, specialize...
Hammack SM, Moshage SG, Kersh ME, McCoy AM.To quantify circulating levels of myokines with a known role in bone remodeling (receptor activator of nuclear factor κ B ligand [RANK-L], matrix metalloproteinase 2 [MMP-2], and irisin) in foals in response to exercise and over the first year of life. Unassigned: 12 foals were enrolled in the study; 6 underwent an 8-week exercise program, and 6 were nonexercised controls. Blood samples were collected between 2 and 11 months of age. Receptor activator of nuclear factor κ B ligand, MMP-2, and irisin were quantified using equine-specific ELISAs. Unassigned: RANK-L, MMP-2, and irisin did not ch...
Austin MMP, Ivey JLZ, Shepherd EA, Myer PR.Starvation in horses presents critical welfare, economic, and management challenges with underlying molecular mechanisms of metabolic modification and recovery left poorly defined. Prolonged caloric deprivation induces significant systemic shifts in carbohydrate, protein, and lipid metabolism, reflected in coordinated changes in tissue-specific gene expression. This review synthesizes current knowledge on equine metabolic responses to starvation, emphasizing pathways found through RNA sequencing (RNA-seq) and real-time quantitative polymerase chain reaction (RT-qPCR) studies. Molecular investi...
Huang Q, Ren W, Shan D, Su Y, Li Z, Li L, Wang R, Ma S, Wang J.This study aimed to compare blood samples from Yili horses with outstanding and average performance in 5000 m races through transcriptome sequencing, identify key differentially expressed genes, lncRNAs, and circRNAs, as well as related enriched pathways, and elucidate their regulatory networks. This study used six healthy four-year-old Yili stallions as subjects, divided into an excellent group (E group, = 3) and an ordinary group (O group, = 3) based on their 5000-m race performance. Blood RNA-Seq technology was used to analyze differentially expressed mRNAs, lncRNAs, and circRNAs. A total...
Hanousek K, O'Hara V, Riddell DO, Piercy RJ.In Thoroughbred horses, a highly prevalent short interspersed nuclear element (SINE) mutation in the myostatin gene (MSTN) promoter influences circulating myostatin concentration and is associated with muscle morphology, fracture risk and optimal race distance. Our prior data reveal that within horses there is substantial variation in serum myostatin concentration, particularly in MSTN heterozygotes and wild type horses but it was unclear whether such variation relates to within-horse differences or to environmental or temporal effects. Here we report the intra-horse consistency of circulating...
Takahashi K, Mukai K, Takahashi Y, Ebisuda Y, Sugiyama F, Hatta H, Kitaoka Y.To explore the molecular mechanisms underlying oxygen-dependent regulation of skeletal muscle adaptations, eight Thoroughbred horses performed 2 min of exercise at a velocity corresponding to 95% maximal O2 uptake under a normoxic condition, while using inspired O2 levels of 0.21 (normoxia), 0.26 (hyperoxia) or 0.16 (hypoxia). At the end of the exercise, arterial O2 saturation was significantly higher with hyperoxia and lower with hypoxia than with normoxia. However, no significant difference in plasma lactate or muscle glycogen concentrations was observed across the O2 conditions. A metabol...
St George L, Nankervis K, Walker V, Maddock C, Robinson A, Sinclair J, Hobbs SJ.Despite growing evidence on the adaptive movement patterns that horses adopt during water treadmill (WT) exercise, underlying adaptations in muscle activity remain uninvestigated. This feasibility study aimed to develop a method for the synchronous measurement of muscle activity and movement of horses during WT exercise. Combined surface electromyography (sEMG) (2000 Hz) from selected hindlimb (biceps femoris, gluteus medius, tensor fasciae latae) and epaxial (longissimus dorsi) muscles, and three-dimensional kinematic (200 Hz) data from the back and pelvis of one (n = 1) horse were collected ...
Rump-Dierig I, Giers J, Frenzel C, Stöckle S, Gehlen H.This study examines seasonal changes in muscle and heart parameters in eventing horses over the course of a competition season. Blood levels of the enzymes creatine kinase (CK) and aspartate aminotransferase (AST) as well as the heart muscle-specific concentration of cardiac troponin I (cTnI) were measured before (pre), 30 min (p30) and 24 h (p24) after competitions. Creatine kinase (CK: median pre-competition = 175 U/L, 30 min post = 221 U/L, 24 h post = 140 U/L), aspartate aminotransferase (AST: pre = 319 U/L, p30 = 335 U/L, p24 = 333 U/L), and cardiac troponin I concentration (cTnI: pre = 0...
Haugaard SL, Nissen SD, Schneider MJ, Birk JB, Carstensen H, Hopster-Iversen C, Altıntaş A, Barrès R, Kjøbsted R, Wojtaszewski JFP, Herum KM....High recurrence rates after atrial fibrillation (AF) treatment may be driven by myocardial changes induced by the arrhythmia itself. Understanding the molecular mechanisms behind these changes is crucial for developing targeted therapies and improving outcomes. Objective: To characterise the cardiac transcriptome of healthy horses and explore transcriptional changes associated with persistent AF (naturally occurring and tachypacing-induced). Methods: Case-control study. Methods: RNA-sequencing was performed on atrial and ventricular tissue samples collected from six horses with naturally occur...
Melanie Catanchin CS, Bell J, Labens R, Quinn CT.Detomidine hydrochloride is an alpha adrenoceptor agonist that is commonly used in equine practice to provide sedation and analgesia for horses undergoing standing procedures. Reported effects following intravenous administration of detomidine in horses include bradycardia, bradyarrhythmias, transient hypertension, sweating, piloerection and dose-dependent sedation, ataxia and analgesia. This case report describes a novel response characterised by tachycardia and profound muscle tremors following the administration of intravenous detomidine to a horse undergoing a standing procedure.
Training on deep sand is commonly employed in endurance horses, but its physiological adaptation remains poorly characterized. This study aimed to characterize locomotor adaptations during a 7 km controlled-speed canter on deep sand in eighteen endurance horses, to identify heart rate variability (HRV) components, and to investigate changes in hematological variables before and after exercise. Stride frequency (SF) and stride length (SL), HRV, and hematological profiles were recorded during exercise and recovery with a fitness tracker. Associations between maximum speed and locomotor parameter...
Wang T, Yang X, Ren W, Meng J, Yao X, Chu H, Yao R, Zhai M, Zeng Y.Exercise performance is a critical trait for evaluating the economic and breeding value of working and athletic horses, with cardiac structure and function serving as essential physiological determinants of athletic capacity. This study aimed to investigate the multi-omics response mechanisms associated with varying degrees of cardiac remodeling under identical exercise intensity. Twenty 2-year-old Yili horses were selected and categorized based on echocardiographic parameters into a high cardiac remodeling group (BH; EDV > 500 mL, SV > 350 mL, EF > 66%) and a low cardiac remodeling group (BL;...
Zuluaga-Cabrera AM, Barbosa da Costa G, Martinez ID, Arias MP.Colombian Paso horses (CPs) excel in gait competitions due to their endurance, speed, and precision, which demand a high level of cardiorespiratory fitness. However, their training regimes often lack scientific support, and few studies have linked physiological parameters to optimal training zones. This study aimed to estimate the aerobic lactate threshold (LTaer) using mathematical methods and to correlate it with heart rate (HR) zones and blood lactate. Eighteen CPs were evaluated and classified into trained (GT) and untrained (GD) groups. All animals underwent a field-based incremental exer...
Littiere TO, da Costa GB, de Sales NAA, de Carvalho JRG, Rodriguez IDM, Ramos GV, de Lacerda-Neto JC, Ferraz GC.Maximal lactate steady state (MLSS) and its predictive thresholds, including the lactate threshold (LT), are widely used to estimate endurance capacity, prescribe training, and assess the effects of training. The human literature identified approximately twenty-five methods to predict the MLSS. This communication compares the concordance between the two D methods and the MLSS. Under laboratory conditions, ten teaching horses underwent a submaximal graded exercise test (GXT) on a treadmill to obtain their lactate-velocity curves (LVC). They performed three to five 30-min continuous running sess...
Jonkhart M, Serra Bragança FM, Smit IH, Brommer H, Suskens JJM.Flexion tests are commonly used in equine locomotion examinations to identify underlying locomotor issues, yet their neuromuscular effects remain poorly understood. Response variability raises concerns about their clinical value in lameness assessments and pre-purchase evaluations. Objective: Primarily, to investigate the effect of full-limb flexion tests on static (flexed position) and dynamic (subsequent trot-up) muscle activity. Secondarily, to assess their effect on locomotion asymmetry during trotting. Methods: In vivo experiments. Methods: Sixteen warmblood horses were randomly assigned ...
Fresa K, Catandi GD, Gonzalez-Castro R, Omar A, Whitcomb LA, Cheng MH, Chen TW, Carnevale EM, Chicco AJ.Advancing age is associated with a decline in fertility and functional capacity, which may result in part from suboptimal nutrition and impaired mitochondrial function. Dietary essential polyunsaturated fatty acids (PUFA) are broadly recommended to mitigate weight loss and reduce risk of chronic disease in aged populations, but their effects on mitochondrial function are less clear. The present study investigated the impacts of dietary supplementation with essential omega-3 PUFA (flaxseed oil; N3) or omega-6 PUFA (corn oil, N6) on blood, muscle and follicular cell fatty acid composition and mi...
Brito G, Damián JP, Trigo P, Ruprechter G.The Raid Hípico Uruguayo (RHU) is the oldest equestrian endurance sport in Uruguay. A high percentage of horses fail to complete RHU rides. Therefore, the aim of this study was to investigate whether weather conditions (comfort index [CI]), horse experience, and ride distance affect horse performance (finishing ride [FR] or nonfinishing ride [NFR]) in the RHU. An additional objective was to determine whether finishing the ride affects the hematological and biochemical parameters of the horses. This study involved 17 RHU rides over distances of 60-90 km and 284 horses. Blood samples were tak...
Graide H, Duysens J, Frank T, Mouithys-Mickalad A, Niesten A, Sandersen C, Ceusters J, Serteyn D.Musculoskeletal pathologies present challenges in athletic horses, often leading to functional impairment. The slow or limited regenerative capacity of bone, joint, and tendon/ligament injuries, coupled with the limitations of conventional treatments, highlights the need for innovative therapies such as ortho-biologics and mesenchymal stem/stroma cells. Traditional 2D cell culture systems with fetal bovine serum (FBS) fail to replicate the complexity of the in vivo environment, whereas 3D cultures more accurately mimic native tissue architecture and cell-cell interactions. This study describes...
Arevalo-Turrubiarte M, Edling CE, Moller-Levet C, Forbes B, Kemp V, Weir J, Marr C, Lewis R, Jeevaratnam K.The initiation and maintenance of atrial fibrillation have been associated with physiological alterations in myocardial sleeves of the pulmonary veins (PVs). Gene expression profiles of the myocardial sleeves of the PVs in healthy (n = 3) and paroxysmal atrial fibrillation (PAF) (n = 6) thoroughbred horses (Equus caballus) were studied. Tissue collected from the left superior PV, adjacent to the left atrium, was analyzed by RNA sequencing. Gene Set Enrichment Analysis demonstrated positive enrichment of gene ontology biological processes related to muscle and endothelial cell development, cell...
Leibeck R, Lehman J, Birmingham S.Whole-body vibrational therapy (WBV) is well-studied in people, but there is a paucity of research regarding its effect on horses. It is suggested that the use of WBV in horses increases performance, aids in recovery, and stimulates nerves, bones, and muscles in ways that normal exercise does not. Objective: The purpose of this pilot study was to determine if frequent WBV therapy sessions affect mechanical nociceptive thresholds based on pressure algometry in horses without clinical signs of lameness or back pain. Methods: The mechanical nociceptive thresholds (MNTs) were measured for 5 horses...
Feng M, Hall TJ, MacHugh DE, Katz LM, Hill EW.Early skeletal muscle development is critical for young racehorses, yet research on the transcriptional changes during this period is limited. Additionally, the impact of age on the transcriptional response to exercise training in equine athletes is not well understood. A transcriptome-wide analysis of differential gene expression in skeletal muscle was performed for five untrained Thoroughbred horses sampled at rest at two years old (UR2) and three years old (UR3). A total of 136 differentially expressed genes (DEGs) were identified, with 95 increased and 41 decreased in expression. GO enrich...
Hiblu MA, Ahmed MO.This case report documents the first identified Brucella infection in a 6-year-old male Thoroughbred horse in Libya. The horse exhibited muscle and joint pain, inflammation over the shoulders with a pulpy texture (fistulous withers), stress, fatigue, and potential systemic infection. Its diagnosis was confirmed through serological testing, with agglutination titers of 1/80 for B. melitensis and 1/160 for B. abortus, and a blood culture revealing Gram-negative coccobacilli. After 3 weeks of combination therapy with rifampicin and doxycycline, the inflammation resolved, systemic signs disappeare...
Reemtsma FP, Giers J, Horstmann S, Stoeckle SD, Gehlen H.Amino acid (AA) metabolism and the adaptation of muscles to increased physical performance are interdependent. This field study examined changes in plasma amino acid (PAA) concentrations and two metabolites (ammonia and urea) before and after cross-country (CC) competitions throughout an entire eventing season and their associations with performance outcomes in eventing horses. Twenty horses from nine different Warmblood breeds were evaluated between two and seven times across 14 international eventing competitions over a 23-week period. A total of 55 rides were sampled. Blood samples were col...
Puccetti M, Beccati F, Pilati N.Femoral nerve neuropathy causes lameness, a condition clinically characterized by stifle's lack of extension with subsequent diminished lower limb function. This case report describes the ultrasonographic diagnosis of femoral neuropathy secondary to compression caused by myopathy of the iliopsoas muscle of an endurance horse during a competition. Transrectal ultrasonography played a pivotal role in diagnosis of the injury by assessment of the involved structures and monitoring of the healing process throughout the recovery period. The horse achieved complete recovery and successfully returned ...
Valberg SJ, Williams ZJ, Ames EG, Mickelson JR, Nout-Lomas YS, Landolt G, Sanz M, Gardner K.Equine myotonic dystrophy (eMD) is a rare neuromuscular disorder of undetermined origin marked by muscle hypertrophy and stiffness, dystrophic muscle histopathology, and myotonic discharges. In humans, myotonic dystrophy (DM) arises from trinucleotide repeat expansions in dystrophia myotonica protein kinase (DMPK) (DM1) or tetranucleotide expansions in cellular nucleic acid-binding protein (CNBP) (DM2), which disrupt mRNA processing and induce embryonic splicing patterns across multiple genes. In 6 eMD Quarter Horse types, (2-36 months-of-age) and 8 control Quarter Horses we determined: (1) fi...
Aleman M.Muscle disease has various clinical manifestations that range from exertional and non-exertional rhabdomyolysis, fasciculations, weakness, rigidity, stiffness, gait abnormalities, poor performance, and alterations in muscle mass and tone. Neurogenic disorders and non-neurogenic disorders such as primary muscle disease can cause muscle atrophy and changes in muscle tone. Myotonic disorders can have a genetic (eg, inherited channelopathies) or acquired (eg, electrolyte derangements) origin. Normal muscle enzyme activities do not rule out a myopathic disorder as the underlying cause of muscle atr...
De Ridder T, Aerts P, MacLaren JA.Equid evolution is characterized by a high diversity of extinct species and morphologies, whereas extant equids share a superficially similar, monodactyl morphology. This inferred musculoskeletal similarity of modern equid limbs remains unexplored, and it is often assumed that domestic horse limbs are representative for wild equids (e.g., zebras, onagers, etc.). Our aim was to quantitatively describe the muscle architecture and arrangement of all forelimb muscles in extant wild Equus species to test this assumption, and investigate any differences between the species. We hypothesized that ther...
