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Topic:Muscle
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.
The effects of short intensive exercise on plasma free amino acids in standardbred trotters. The aim of this study was to investigate the effect of short intense exercise on plasma amino acid concentrations in trotters and to test the repeatability of plasma amino acids concentration in samples obtained on two independent days under field conditions. Plasma amino acid concentrations were analysed in blood samples of 36 standardbred trotters before and after intense exercise over a distance of 2000 m. Sampling was repeated in 20 horses after 35 days. Exercise intensity was estimated from post-exercise lactate levels. Horses were divided in two groups according to a cut-off lactate conc...
Optimal diet of horses with chronic exertional myopathies. Chronic exertional rhabdomyolysis represents a syndrome of recurrent exercise-associated muscle damage in horses that arises from a variety of etiologies. Major advances have been made in the understanding of the pathophysiology of this disease, and causative genetic defects have been recently identified for two conditions-polysaccharide storage myopathy of quarter horses, paints, warm bloods, and draft breeds. Dietary management in combination with a regular exercise regimen comprises the most effective means for control of clinical signs.
Storage-associated artefact in equine muscle biopsy samples. Muscle biopsy is increasingly used in equine veterinary practice for investigating exertional, inflammatory or immune mediated myopathies and unexplained muscle atrophy. Although formalin-fixed samples are often used, for complete evaluation, fresh-frozen tissue is required. Freezing muscle in veterinary practice is impractical: samples sent to specialist laboratories for processing are therefore susceptible to delays, potentially leading to artefact and compromising histological interpretation. Objective: Altered temperature, duration and hydration status influence the severity of storage-ind...
Metabolism during anaesthesia and recovery in colic and healthy horses: a microdialysis study. Muscle metabolism in horses has been studied mainly by analysis of substances in blood or plasma and muscle biopsy specimens. By using microdialysis, real-time monitoring of the metabolic events in local tissue with a minimum of trauma is possible. There is limited information about muscle metabolism in the early recovery period after anaesthesia in horses and especially in the colic horse. The aims were to evaluate the microdialysis technique as a complement to plasma analysis and to study the concentration changes in lactate, pyruvate, glucose, glycerol, and urea during anaesthesia and in th...
Malignant hyperthermia associated with ryanodine receptor 1 (C7360G) mutation in Quarter Horses. Anesthetic-induced malignant hyperthermia (MH) has been documented in Quarter Horses with a single point mutation in the ryanodine receptor 1 gene (RyR1) at nucleotide C7360G, generating a R2454G amino acid substitution. However, there have been no reports of nonanesthetic manifestations of MH in horses with the C7360G mutation. Objective: To describe clinical manifestations of Quarter Horses with the C7360G mutation. Methods: Eleven Quarter Horses with the RyR1 C7360G mutation. Methods: This prospective study included horses with suspected MH, undetermined etiology of sudden death, death with...
Assessment of the transformation of equine skin-derived fibroblasts to multinucleated skeletal myotubes following lentiviral-induced expression of equine myogenic differentiation 1. To develop a reliable method for converting cultured equine skin-derived fibroblasts into muscle cells. Methods: Equine skin-derived fibroblasts. Methods: The equine myogenic differentiation 1 (eqMyoD) genomic sequence was obtained by use of equine bacterial artificial chromosome screening and PCR sequencing. Total mRNA was extracted from foal skeletal muscle, and eqMyoD cDNA was cloned into a plasmid vector with an internal ribosomal entry site to express bicistronic eqMyoD or enhanced green fluorescent protein (EGFP). Transient expression was confirmed by immunocytochemical analysis and west...
Fluid and electrolyte supplementation after prolonged moderate-intensity exercise enhances muscle glycogen resynthesis in Standardbred horses. We hypothesized that postexercise rehydration using a hypotonic electrolyte solution will increase the rate of recovery of whole body hydration, and that this is associated with increased muscle glycogen and electrolyte recovery in horses. Gluteus medius biopsies and jugular venous blood were sampled from six exercise-conditioned Standardbreds on two separate occasions, at rest and for 24 h following a competitive exercise test (CET) designed to simulate the speed and endurance test of a 3-day event. After the CETs, horses were given water ad libitum, and either a hypotonic commercial electrol...
(Over)training effects on quantitative electromyography and muscle enzyme activities in standardbred horses. Too intensive training may lead to overreaching or overtraining. To study whether quantitative needle electromyography (QEMG) is more sensitive to detect training (mal)adaptation than muscle enzyme activities, 12 standardbred geldings trained for 32 wk in age-, breed-, and sex-matched fixed pairs. After a habituation and normal training (NT) phase (phases 1 and 2, 4 and 18 wk, respectively), with increasing intensity and duration and frequency of training sessions, an intensified training (IT) group (phase 3, 6 wk) and a control group (which continued training as in the last week of phase 2) w...
A GYS1 gene mutation is highly associated with polysaccharide storage myopathy in Cob Normand draught horses. Glycogen storage diseases or glycogenoses are inherited diseases caused by abnormalities of enzymes that regulate the synthesis or degradation of glycogen. Deleterious mutations in many genes of the glyco(geno)lytic or the glycogenesis pathways can potentially cause a glycogenosis, and currently mutations in fourteen different genes are known to cause animal or human glycogenoses, resulting in myopathies and/or hepatic disorders. The genetic bases of two forms of glycogenosis are currently known in horses. A fatal neonatal polysystemic type IV glycogenosis, inherited recessively in affected Qu...
Contractile behavior of the forelimb digital flexors during steady-state locomotion in horses (Equus caballus): an initial test of muscle architectural hypotheses about in vivo function. The forelimb digital flexors of the horse display remarkable diversity in muscle architecture despite each muscle-tendon unit having a similar mechanical advantage across the fetlock joint. We focus on two distinct muscles of the digital flexor system: short compartment deep digital flexor (DDF(sc)) and the superficial digital flexor (SDF). The objectives were to investigate force-length behavior and work performance of these two muscles in vivo during locomotion, and to determine how muscle architecture contributes to in vivo function in this system. We directly recorded muscle force (via ten...
Pathologic findings in equine muscle (excluding polysaccharide storage): a necropsy study. 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...
Evaluation of the effect of ranitidine on gastroduodenal contractile activity and gastric emptying in horses. To determine the effect of ranitidine on gastric emptying in horses. Methods: 11 adult horses. Methods: In vitro, isolated muscle strips from the pyloric antrum and duodenum of 5 horses were suspended in baths and attached to isometric force transducers. Once stable spontaneous contractions were observed, ranitidine or diluent was added at cumulative increasing concentrations. Isometric stress responses were compared. In vivo, 6 horses were assigned to a group in a prospective randomized crossover study design with a wash-out period of 2 weeks between trials. Ranitidine (2.2 mg/kg) or saline (...
Equine anesthesia: triple drip. Anesthetization of large animals, such as the horse, is a challenge for veterinarians and compounding pharmacists. This article discusses the technique of intravenous anesthesia by using a combination of xylazine and ketamine in the horse for short-term unconsciousness; a combination of xylazine, diazepam, and ketamine, for improved sedation and muscle relaxation; and a combination of xylazine, ketamine, and guaifenesin, referred to as Triple Drip, for the maximum 1-hour duration of unconsciousness. Compounding pharmacists that have the facilities and training required to prepare sterile compo...
Use of acupuncture in equine reproduction. The goal of this review is to provide evidence supporting the physiologic basis for the use of acupuncture as a treatment in equine reproduction, and to discuss current uses of acupuncture for the treatment of anestrus, urine pooling, uterine infection and/or fluid, infertility, maintenance of pregnancy, cryptorchidism, musculoskeletal pain, and poor libido in stallions. The benefits achieved through acupuncture treatment are thought to be a result of hormonal regulation, altered smooth muscle motility, and general stress and/or pain relief from musculoskeletal or environmental conditions.
Insulin sensitivity in Belgian horses with polysaccharide storage myopathy. To determine insulin sensitivity, proportions of muscle fiber types, and activities of glycogenolytic and glycolytic enzymes in Belgians with and without polysaccharide storage myopathy (PSSM). Methods: 10 Quarter Horses (QHs) and 103 Belgians in which PSSM status had been determined. Methods: To determine insulin sensitivity, a hyperinsulinemic euglycemic clamp (HEC) technique was used in 5 Belgians with PSSM and 5 Belgians without PSSM. Insulin was infused i.v. at 3 mU/min/kg for 3 hours, and concentrations of blood glucose and plasma insulin were determined throughout. An i.v. infusion of g...
Endothelin mediated contraction of equine laminar veins. Endothelin-1 (ET-1) may be a key mediator in the pathogenesis of laminitis, but endothelin-mediated responses in the venous microcirculation of the equine foot have yet to be fully characterised. Objective: To characterise the response of equine laminar veins to ET-1 and evaluate the ET-1 receptor subtypes that mediate this response. Methods: Small veins (150-500 microns) draining the equine digital laminae from healthy horses and ponies subjected to euthanasia at an abattoir were investigated using wire myography. Concentration response curves were constructed for ET-1 in the presence of ETA ...
Polysaccharide storage myopathy in Cob Normand draft horses. Gluteus medius muscle was sampled from 53 Cob Normand horses for histologic evaluation. Twenty horses (38%) exhibited amylase-resistant material in myocytes consistent with polysaccharide storage myopathy. Diameter of affected type II fibers was increased (67.7 +/- 21.4 microm) compared with normal ones (57.3 +/- 19.7 microm). Two groups were distinguished by quantitative study. The first group (n = 14; 26%) was characterized by a low percentage of fibers (m = 0.98%) containing aggregates occurring singly or in perifascicular clusters without myopathic changes. The second group (n = 6; 11%) wa...
[Dynamics of hip joint biomechanics in patients with coxarthrosis at the time of hippotherapy]. The problems of degenerative-dystrophic abnormalities stimulate the development of new skills and methods of treatment and rehabilitation of the diseases. The goal of the study was to determine the efficacy of hippotherapy in patients with coxarthrosis, according to functional and biomechanical parameters. Hippotherapy involves the utilization of horseback riding to stimulate the patient's normal reactions and locomotion; to improve the balance and coordination of movement, normalize muscle tension, and eliminate pathological reflexes. The advantage of the hippotherapy is in the specific postu...
Acquired multiple Acyl-CoA dehydrogenase deficiency in 10 horses with atypical myopathy. The aim of the current study was to assess lipid metabolism in horses with atypical myopathy. Urine samples from 10 cases were subjected to analysis of organic acids, glycine conjugates, and acylcarnitines revealing increased mean excretion of lactic acid, ethylmalonic acid, 2-methylsuccinic acid, butyrylglycine, (iso)valerylglycine, hexanoylglycine, free carnitine, C2-, C3-, C4-, C5-, C6-, C8-, C8:1-, C10:1-, and C10:2-carnitine as compared with 15 control horses (12 healthy and three with acute myopathy due to other causes). Analysis of plasma revealed similar results for these predominantly...
A review of equine muscle disorders. Muscle disorders are a common cause of disability in horses. For many years, clinical manifestations such as muscle pain, exercise intolerance, weakness, and stiffness were believed to be caused by a single syndrome. However, in the past years a broad spectrum of muscle disorders have been recognized including glycogen and polysaccharide storage myopathies, malignant hyperthermia, mitochondrial myopathy, hyperkalemic periodic paralysis and others. For some, a specific mutation has been identified. Recognition of the myopathic clinical phenotype and thorough clinical, electrodiagnostic, and his...
Prevalence of equine polysaccharide storage myopathy and other myopathies in two equine populations in the United Kingdom. The aim of this study was to determine the prevalence of equine polysaccharide storage myopathy (EPSM) in two populations of horses in the UK. Biopsy specimens from 94 horses presented to an abattoir (population 1), and 46 horses with neuromuscular disorders presented to a university referral hospital (population 2) were obtained over a period of 4years. Histological sections were examined by a veterinary pathologist for lesions including abnormal polysaccharide inclusions in myofibres. In population 1, a diagnosis of EPSM was made in 8% and non-specific myopathy in 33% of horses. In populatio...
Electromyographic activity of the longissimus dorsi muscles in horses when walking on a treadmill. The pattern of electromyographic activity of the equine long back muscle at the walk has not yet been reported. The aim of this study was to use surface electromyography to measure activity of the longissimus dorsi muscles of horses walking on a treadmill. Fifteen horses without back pain were used and electromyographs were recorded bilaterally from the longissimus dorsi muscles at the level of T12, T16 and L3. Mean electromyograph activity and mean motion were calculated for each horse. At the walk, only one maximum activity for each longissimus dorsi muscle was detected during each motion cy...
Comparison between acceleromyography and visual assessment of train-of-four for monitoring neuromuscular blockade in horses undergoing surgery. To compare acceleromyography (AMG) with visual assessment of train-of-four (TOF) for monitoring neuromuscular blockade and detecting residual muscle paralysis in horses receiving atracurium. Methods: Prospective, controlled clinical study. Methods: Nine adult, client-owned horses weighing 577 (436, 727) kg (median, minimum, maximum) and ASA physical status I-II, admitted for surgery. Methods: An electrical nerve stimulator was used to stimulate the peroneal nerve with TOFs at 1 minute intervals. Before and after atracurium administration (0.15 mg kg(-1), IV), the number of twitches observed (T...
Contractile effects of 5-hydroxytryptamine (5-HT) in the equine jejunum circular muscle: functional and immunohistochemical identification of a 5-HT1A-like receptor. Prokinetic drugs used to treat gastrointestinal ileus in man have equivocal results in horses. In man, prokinetic drugs have 5-hydroxytryptamine4(5-HT4) receptors as their target, but little is known about the 5-HT-receptor subtypes in the equine small intestine. Objective: Functional and immunohistochemical identification of the serotonin receptor subtype(s) responsible for the 5-HT induced contractile response in the equine circular jejunum. Methods: Isometric organ-bath recordings were carried out to assess spontaneous and drug-evoked contractile activity of equine circular jejunum. Histolo...
Distribution of the neurokinin-1 receptor in equine intestinal smooth muscle. Tachykinins have profound effects on equine intestinal motility, but the distribution of the neurokinin receptors (NKRs) through which they act is unknown. This study reports the distribution of one of these receptors, the neurokinin-1 receptor (NK1R), in smooth muscle throughout the equine intestinal tract. Objective: To quantify the distribution of the NK1R, based upon mRNA expression, in smooth muscle of different regions of the equine intestinal tract. Methods: Nine regions of the intestinal tract were sampled in 5 mature horses. Total RNA was isolated from smooth muscle and reverse transc...
History and clinical features of atypical myopathy in horses in Belgium (2000-2005). The emergent nature of atypical myopathy or atypical myoglobinuria (AM) necessitates precise description of its clinical and epidemiologic features. Objective: To define key features of AM to help practitioners recognize the disease and to advise owners to take preventive measures. Methods: Belgian cases of AM confirmed by histology (CC horses; n = 57) from autumn 2000 to spring 2005 were included in the study. Co-grazing horses (Co-G horses; n = 77) that remained free of any abnormal clinical signs constituted a control group. Methods: History, environmental characteristics, clinical signs, a...
Comparative anatomy and muscle architecture of selected hind limb muscles in the Quarter Horse and Arab. The Quarter Horse (bred for acceleration) and the Arab (bred for endurance) are situated at either end of the equine athletic spectrum. Studies into the form and function of the leg muscles in human sprint and endurance runners have demonstrated that differences exist in their muscle architecture. It is not known whether similar differences exist in the horse. Six Quarter Horse and six Arab fresh hind limb cadavers were dissected to gain information on the muscle mass and architecture of the following muscles: gluteus medius; biceps femoris; semitendinosus; vastus lateralis; gastrocnemius; tib...
An epidemiological study of myopathies in Warmblood horses. 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 ...
Myonecrosis in three horses with colic: evidence for endotoxic injury. Three horses with colic, clinical evidence of endotoxaemia and high serum activities of creatine kinase and aspartate aminotransferase were examined postmortem. The horses were diagnosed with severe ulcerative colitis, pyloric ulceration and stenosis with colonic sand impaction, and colonic obstruction due to faecaliths. There was no gross or histological evidence of muscle trauma. Their semimembranosus muscles had scattered acute to subacute segmental necrosis of the myofibres, suggestive of endotoxin-induced muscle injury.
