Equine metabolism encompasses the biochemical processes that occur within horses to maintain life, including the conversion of food into energy, the synthesis of necessary compounds, and the elimination of waste products. These processes are essential for supporting various physiological functions such as growth, reproduction, and physical performance. Key components of equine metabolism include carbohydrate, fat, and protein metabolism, each of which contributes to the overall energy balance and health of the horse. Factors influencing metabolic rate and efficiency in horses include age, breed, diet, exercise, and health status. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms, regulation, and implications of metabolic processes in equine physiology.
Westermann CM, Dorland L, van Diggelen OP, Schoonderwoerd K, Bierau J, Waterham HR, van der Kolk JH.Earlier research on ten horses suffering from the frequently fatal disorder atypical myopathy showed that MADD (multiple acyl-CoA dehydrogenase deficiency) is the biochemical derangement behind atypical myopathy. From five horses that died as a result of this disease and seven healthy control horses, urine and plasma were collected ante mortem and muscle biopsies were obtained immediately post-mortem (2 patients and 7 control horses), to analyse creatine, purine and carbohydrate metabolism as well as oxidative phosphorylation. In patients, the mean creatine concentration in urine was increased...
Hwang I, Jung EM, Yang H, Choi KC, Jeung EB.Calcium transporter genes, such as transient receptor potential cation channel subfamily V members 5/6 (TRPV5/6), Na(+)/Ca(2+) exchanger 1 (NCX1), and plasma membrane calcium-transporting ATPase 1b (PMCA1b), are essential for maintaining homeostasis and metabolizing Ca(2+) ions. The TRPV5 and TRPV6 proteins play an important role in Ca(2+ )absorption, and NCX1 and PMCA1b are both critical for intracellular calcium homeostasis. In this study, the tissue-specific mRNA and protein expression of these calcium transporter genes in the duodenum, kidney and heart of the horse (Equus caballus) was exa...
Stewart AJ, Boothe DM, Cruz-Espindola C, Mitchum EJ, Springfield J.To determine the pharmacokinetics of tramadol and its metabolites O-desmethyltramadol (ODT) and N-desmethyltramadol (NDT) in adult horses. Methods: 12 mixed-breed horses. Methods: Horses received tramadol IV (5 mg/kg, over 3 minutes) and orally (10 mg/kg) with a 6-day washout period in a randomized crossover design. Serum samples were collected over 48 hours. Serum tramadol, ODT, and NDT concentrations were measured via high-performance liquid chromatography and analyzed via noncompartmental analysis. Results: Maximum mean ± SEM serum concentrations after IV administration for tramadol, ODT, ...
Peters J, Block W, Oswald S, Freyer J, Grube M, Kroemer HK, Lämmer M, Lütjohann D, Venner M, Siegmund W.The delivery of clarithromycin (CRL) to its site of action in bronchial/alveolar epithelial cells (EC), bronchial epithelial lining fluid (ELF), and bronchoalveolar lavage cells (BALC) may be influenced by CYP3A4 and the drug transporters, ATP-binding cassette (ABC) B1 and ABCC2 and organic anion-transporting polypeptides (OATPs), which can be modulated and/or up-regulated via the nuclear pregnane X receptor (PXR) by rifampicin (RIF). Therefore, we evaluated the disposition and pulmonary distribution of CLR (7.5 mg/kg b.i.d., 21 days) and expression of ABCB1, ABCC2, OATP1A2, and OATP2B1 in EC ...
Longland AC, Barfoot C, Harris PA.The aim of this study was to determine the amounts of water-soluble carbohydrate (WSC), WSC constituents and protein leached from a range of U.K. hays soaked according to common practice. Initial hay WSC content ranged from 123 to 230 g/kg dry matter (DM). Soaking the hays for up to 16 hours in water at a mean temperature of 8°C resulted in a mean loss of 27 per cent (range 6 to 54 per cent) of hay WSC. The mean percentage losses of WSC constituents were 24 per cent (range 14 to 31) for fructan, 41 per cent (range 21 to 70) for fructose, 45 per cent (range 28 to 100) for sucrose and 56 per ce...
Tinworth KD, Wynn PC, Boston RC, Harris PA, Sillence MN, Thevis M, Thomas A, Noble GK.Determining circulating equine insulin concentrations is becoming increasingly important in equine clinical practice and research. Most available assays are optimized for human medicine, but there is strong equine cross-reactivity because of the highly conserved nature of insulin. To identify an accurate and reliable assay for equine insulin, 6 commercial immunoassays were evaluated for precision, accuracy, and specificity. Only 1 assay initially reached the requisite standard: Mercodia Equine Insulin Enzyme-linked Immunosorbent assay (ELISA). Plasma matrix interferences were identified when t...
Votion DM, Fraipont A, Goachet AG, Robert C, van Erck E, Amory H, Ceusters J, de la Rebière de Pouyade G, Franck T, Mouithys-Mickalad A, Niesten A....Limited information exists about the muscle mitochondrial respiratory function changes that occur in horses during an endurance season. Objective: To determine effects of training and racing on muscle oxidative phosphorylation (OXPHOS) and electron transport system (ETS) capacities in horses with high resolution respirometry (HRR). Methods: Mitochondrial respiration was measured in microbiopsies taken from the triceps brachii (tb) and gluteus medius (gm) muscles in 8 endurance horses (7 purebred Arabians and 1 crossbred Arabian) before training (T0), after two 10 week training periods (T1, T2)...
Vengust M, Stämpfli H, De Moraes AN, Teixeiro-Neto F, Viel L, Heigenhauser G.Carbonic anhydrase (CA) catalyses the hydration/dehydration reaction of CO(2) and increases the rate of Cl(-) and HCO(3)(-) exchange between the erythrocytes and plasma. Therefore, chronic inhibition of CA has a potential to attenuate CO(2) output and induce greater metabolic and respiratory acidosis in exercising horses. Objective: To determine the effects of Carbonic anhydrase inhibition on CO(2) output and ionic exchange between erythrocytes and plasma and their influence on acid-base balance in the pulmonary circulation (across the lung) in exercising horses with and without CA inhibition....
Robert C, Goachet AG, Fraipont A, Votion DM, Van Erck E, Leclerc JL.Limited information exists about the physiological training-induced changes in electrolyte balance of horses competing in long distance endurance races. Objective: To determine the effects of endurance training and racing on hydration and electrolyte balance in horses. Methods: Blood and urine were sampled at rest in 8 endurance horses before training and after two 11 week training periods (T1 and T2). Each training was followed by a 120 km endurance ride and horses were sampled before, during and 2 h after the rides. Blood was analysed for packed cell volume (PCV), total protein (TP), urea, c...
Hill EW, Eivers SS, McGivney BA, Fonseca RG, Gu J, Smith NA, Browne JA, MacHugh DE, Katz LM.The role of molecular signalling pathways in the phenotypic adaptation of skeletal muscle to different exercise stimuli in the Thoroughbred horse has not been reported previously. Objective: To examine CKM, COX4I1, COX4I2 and PDK4 gene expression following high intensity sprint and moderate intensity treadmill exercise stimuli in skeletal muscle of Thoroughbred horses. Methods: Two groups of trained 3-year-old Thoroughbred horses participated. Group A (n = 6 females, n = 3 males) participated in an incremental step test (moderate intensity) to fatigue or HR(max) on a Sato high speed treadmill ...
Ohmura H, Mukai K, Takahashi T, Matsui A, Hiraga A, Jones JH.Accumulated O(2) deficit (AOD) and plasma lactate accumulation rate (PLAR) are alternative methods for estimating net anaerobic energy utilisation (NAEU) in exercising horses. How they compare or their accuracy is unknown. Objective: We hypothesised net anaerobic energy utilisation calculated by PLAR (NAUE(PLAR)) is equivalent to NAUE estimated by AOD (NAUE(AOD)). Methods: Six Thoroughbred horses ran at identical supramaximal speeds (118% aerobic capacity) until exhaustion for 2 runs while breathing normoxic (NO, 21% O(2)) or hyperoxic (HO, 26% O(2)) gas. Jugular blood was sampled at 15 s inte...
Revold T, Mykkänen AK, Karlström K, Ihler CF, Pösö AR, Essén-Gustavsson B.Muscular changes caused by training are breed-specific and studies on the Norwegian-Swedish Coldblooded Trotter (NSCT) are limited. Knowledge about lactate-transporters in muscle in this light draught breed used for harness racing is lacking. Objective: To identify muscular changes associated with training in young NSCTs and investigate muscular distribution of the monocarboxylate transporter 1 (MCT1) and its ancillary protein CD147, which facilitate lactate transport across membranes. Methods: Nine horses were followed from the start of their training period until the end of their 3-year-old ...
Goachet AG, Varloud M, Philippeau C, Julliand V.In endurance horses, commonly fed 80% forage, energy is provided mainly by VFA produced in the hindgut during cell wall degradation, but cell wall digestibility has been reported to be impaired by exercise. Objective: To assess the influence of a long-term endurance conditioning on cell wall digestion in horses. Methods: The total tract apparent digestibility of dry matter, organic matter and fibrous constituents, solid and liquid total mean retention time and the faecal microbial ecosystem of purebred Arabian horses were measured for 2 years in 2 longitudinal experiments. Methods: Performed a...
Essén-Gustavsson B, Connysson M, Jansson A.There is little information about the influence of crude protein (CP) intake on glycogen and free pool amino acid concentrations in the muscle of horses in training. High energy forage-only diets may be an alternative to concentrate rich diets and may provide high levels of CP. Objective: To study the effect of feeding 2 forage-only diets, containing either high or moderate CP concentrations on glycogen and free pool amino acid concentrations in the muscle. Methods: Two high energy forage-only diets based on high-energy grass forage were fed for 23 days in a crossover design to 6 Standardbred ...
Spooner HS, Nielsen BD, Schott HC, Harris PA.Excessive sweat loss during endurance exercise may lead to electrolyte disturbances and previous research suggests dietary factors may affect hydration status. While investigating the effect of dietary fibre type on hydration status, sweat samples were collected which allowed for the evaluation of sweat composition in horses consuming forage-based, low sodium (Na) rations. Objective: To investigate sweat composition in Arabian horses performing endurance type exercise while fed forage-based, rations low in Na. Methods: Six 2-year-old Arabian horses were fed, according to a replicated 3 × 3 La...
Stewart-Hunt L, Pratt-Phillips S, McCutcheon LJ, Geor RJ.Starch rich (S) feeds reduce insulin sensitivity in untrained horses when compared to high fat (F) feeds, but insulin sensitivity is not affected when S or F are fed during exercise training. The effects of S vs. F on training-associated alterations in skeletal muscle glucose metabolism are unknown. Objective: To determine the effects of dietary energy source on training-associated changes in insulin sensitivity, skeletal muscle GLUT4 protein and hexokinase (HK) and glycogen synthase (GS) activities in horses. Methods: After a baseline period on an all forage diet (Phase 1), horses were adapte...
Cottin F, Metayer N, Goachet AG, Julliand V, Slawinski J, Billat V, Barrey E.Arabian horses have morphological, muscular and metabolic features designed for endurance races. Their gas exchange and gait variables were therefore measured during a field exercise test. This study presents original respiratory and locomotor data recorded in endurance horses under field conditions. Objective: Respiratory gas exchange ratio (RER) of Arabian horses at the speed required to win endurance races (18 km/h for 120-160 km) are <1 and running economy (RE) is also low in order to maintain exercise intensity using aerobic metabolism for long intervals. The purpose of this study was to ...
Borgia LA, Valberg SJ, Essen-Gustavsson B.Flexor tendon injury may be due to flexor muscle fatigue, contributing to fetlock joint hyperextension and tendon damage. A water treadmill provides resistance training on flexor tendon muscles, which might reduce the risk of tendon injury. Objective: To determine the effect of water treadmill training on the properties of the gluteal and superficial digital flexor (SDF) muscles and on cardiocirculatory response to a standardised exercise test. Methods: Five healthy unfit horses were trained on a water treadmill for 5 days/week for 4 weeks, starting with 5 min/day increasing to 20 min/day. Bef...
Kallings P, Persson SG, Essén-Gustavsson B.Since nonsteroidal anti-inflammatory drugs, such as flunixin, on account of their anti-inflammatory and analgesic properties, are used in both racing and equestrian sport horses, the question has been raised as to whether these drugs affect the physiological responses to exercise and thus performance potential. Objective: The aims of this investigation were to study the effects of flunixin on cardiorespiratory, metabolic and locomotor parameters in horses during intense treadmill exercise. Methods: Six Standardbred trotters underwent an incremental treadmill exercise test to fatigue, without d...
Kawai M, Kuwano A, Hiraga A, Miyata H.The myonuclear domain (MND) is the region of cytoplasm governed by a single myonucleus. Myonuclear domain size is an important factor for muscle fibre plasticity because each myonucleus has limitations in the capacity of protein synthesis. Previous studies have demonstrated that differences in MND size exist in different fibre types in several species, including horses. Objective: To understand the basic mechanism of muscle plasticity, the relationships between MND size, muscle fibre type population and metabolic properties of skeletal muscles throughout the whole body in Thoroughbred horses w...
Muñoz A, Riber C, Trigo P, Castejón-Riber C, Castejón FM.Limited information exists concerning the defence of homeostasis during endurance competitions and the relationship with performance. Objective: This research analysed renin (REN), angiotensin II (ANG), aldosterone (ALD) and vasopressin (AVP) in horses covering different distances, assesses differences between successful and eliminated horses and evaluates correlations between hydration status, renal function, electrolytes, REN, ANG, ALD and AVP. Methods: Packed cell volume (PCV), velocity and serum concentrations of REN, ANG, ALD, AVP, Na, K, Cl, Ca, Mg, P, creatine kinase, aspartate aminotra...
Geor RJ, Stewart-Hunt L, McCutcheon LJ.There is limited information about factors regulating glucose utilisation post exercise in horses. Objective: To determine the effects of a single bout of moderate intensity exercise on measures of insulin-mediated (IMGU) and noninsulin-mediated (NIMGU) glucose uptake during a hyperglycaemic clamp (HC). Methods: Hyperglycaemic clamps were administered in random order to 8 Standardbreds under 4 conditions: 1) rest, insulinopenia (R-L); 2) rest, hyperinsulinaemia (R-H); 3) post exercise (45 min at ∼ 50% VO2peak), insulinopenia (Ex-L) and 4) post exercise, hyperinsulinaemia (Ex-H). In the R-L a...
Urschel KL, Geor RJ, Waterfall HL, Shoveller AK, McCutcheon LJ.Providing protein or amino acid mixtures in combination with glucose to post exercise in man has resulted in increases in the post feeding insulin response and in muscle glycogen and protein synthesis rates. However, whether protein and/or amino acids can modify the post exercise insulin responses in horses remains to be fully elucidated. Objective: To determine whether whey protein or leucine addition to a glucose solution affects the post gavage plasma insulin, glucose and amino acid responses in horses and whether these responses are different following a period of exercise vs. rest. Method...
Barnes A, Kingston J, Beetson S, Kuiper C.This study investigated the physiology of endurance horses competing in warm weather over technical terrain, a situation where horses may become metabolically compromised. Objective: There will be changes in physiological, haematological and biochemical variables as horses progress through the 160 km ride and horses detected clinically at the veterinary inspections as metabolically compromised will have significant differences in measured laboratory variables compared to horses that complete the ride successfully. Methods: Forty-eight horses competing in the Australian Tom Quilty 160 km endura...
Meyer ND, Bayly WM, Sides RH, Wardrop KJ, Slinker BK.Prolonged equine exercise can cause hypochloraemic alkalosis and hypokalaemia secondary to the loss of hypertonic sweat. Movement of ions in and out of erythrocytes during exercise may help regulate acid-base balance and changes in plasma ion concentrations. The extent to which this happens during prolonged equine exercise has not been reported. Objective: To measure changes in blood gases and major plasma and intraerythrocytic (iRBC) ion concentrations of horses undergoing prolonged submaximal exercise. Methods: Six horses were trotted at ∼ 30% VO2max on a treadmill for 105 min. Arterial ((...
Connysson M, Essén-Gustavsson B, Lindberg JE, Jansson A.A higher forage allowance to athletic horses might be an alternative to increase health and the gut fluid reservoir. However, more forage might increase bodyweight (bwt) and could therefore be a limitation during competition. Objective: To investigate the effect of a forage-only diet (FD) compared to a 50:50 (dry matter basis) forage:oats diet (OD) on bwt, plasma protein concentration and some metabolic plasma parameters during 12 h of feed deprivation. Methods: Twelve adult Standardbred horses in training were used. The 2 diets were fed in 2 experimental periods of 3 weeks each in a crossover...
McKenzie EC, Garrett RL, Payton ME, Riehl JH, Firshman AM, Valberg SJ.Dantrolene sodium is used to prevent exertional rhabdomyolysis in predisposed horses. Food intake might negatively impact dantrolene bioavailability in horses; however, prolonged feed restriction might be detrimental to performance. Objective: To determine a minimum duration of feed restriction that would optimise plasma dantrolene concentrations in horses after nasogastric administration. It was hypothesised that feed restriction for 4, 8 or 12 h before dantrolene administration would result in higher plasma dantrolene concentrations than achieved with no feed restriction before treatment. Me...
Smarsh DN, Liburt N, Streltsova J, McKeever K, Williams CA.Many nutraceuticals are used as equine supplements without their efficacy having been scientifically tested. Black tea, cranberries, orange peel and ginger are a few of those nutraceuticals that warrant further study. Objective: To test the effects of single doses of black tea, cranberry, orange peel and ginger extract on markers of oxidative stress and antioxidant status following exercise in horses. Methods: In Study 1, 9 mature, healthy but unfit Standardbred mares were administered 2 l of a control (water), orange peel extract (30 g extract) or decaffeinated black tea extract (28 g extract...
Kemmink A, Westermann CM, van der Kolk JH.The quantity of glucose disposal during exercise (walk and trot) compared to rest by use of the hyperglycaemic clamp technique has not been reported previously and has relevance to nutritional requirements. Objective: Exercise (walk and trot) significantly increases glucose disposal compared to rest. Methods: Seven healthy Dutch Warmblood mares, all in dioestrus, mean ± s.d. age 11.6 ± 2.4 years and weighing 569 ± 40 kg were fasted for 12 h prior to a hyperglycaemic clamp at rest (maintaining a steady state of the blood glucose concentration during 30 min), walk (10 min, 1.5 m/s), trot (20 ...
Trigo P, Castejon F, Riber C, Muñoz A.Endurance races are the competition with the biggest metabolic demands for the sport horse. During races, some horses show homeostasis alterations, having repercussions in diverse biochemical parameters and negative consequences on performance and health. Objective: To evaluate the utility of biochemical analysis in the early diagnosis of metabolic stress and to determine cut-off values of biochemical parameters to assist in the prevention of metabolic alterations in endurance horses. Methods: This study involved 36 CEI races and 283 horses (41 eliminated because of metabolic disturbances). Bl...
Serwotka-Suszczak AM, Marcinkowska KA, Smieszek A, Michalak IM, Grzebyk M, Wiśniewski M, Marycz KM.Insulin resistance (IR) is one of the characteristic features of equine metabolic syndrome (EMS). Presently, the only therapies of choice are caloric restrictions combined with mineral supplementation, which might improve insulin sensitivity. In this study we investigated the effect of Haematococcus pluvialis algae water extract enriched in bioaccumulation process in magnesium ions (Hp_Mg(II)) on equine adipose derived mesenchymal stromal stem cells, in which insulin resistance was induced by palmitic acid (IR-EqASCs). For this purpose, chemical characterization of H. pluvialis was performed w...
Johnson PJ, Ganjam VK, Slight SH, Kreeger JM, Messer NT.The role of glucocorticoids (GCs) in the pathogenesis of laminitis is incompletely understood. Local tissue activity of GC is regulated by the steroid converting enzyme, 11beta-hydroxysteroid dehydrogenase-1 (11beta-HSD-1). Changes in integumentary (skin and hoof lamellar) 11beta-HSD activity occurring during laminitis could affect the extent to which GCs are involved in its development. Objective: That changes in integumentary 11beta-HSD-1 activity associated with the laminitic condition would lead to elevated local tissue levels of GCs, which could subsequently contribute, through paracrine ...
Cochaux P, Van Sande J, Swillens S, Dumont JE.The characteristics of the iodide-induced inhibition of cyclic AMP accumulation in dog thyroid slices have been previously described [Van Sande, J., Cochaux, P. and Dumont, J. E. (1985) Mol. Cell. Endocrinol. 40, 181-192]. In the present study we investigated the characteristics of the iodide-induced inhibition of adenylate cyclase activity in dog and horse thyroid. The inhibition of cyclic AMP accumulation by iodide in stimulated horse thyroid slices was similar to that observed in dog thyroid slices. The inhibition was observed in slices stimulated by thyroid-stimulating hormone, cholera tox...
Fowden AL, Gardner DS, Ousey JC, Giussani DA, Forhead AJ.At birth, the endocrine pancreas becomes more directly involved in the control of glycaemia than in utero. However, compared with other tissues, relatively little is known about the maturational changes that occur in the fetal endocrine pancreas in preparation for extrauterine life. This study examined the pancreatic beta-cell response to exogenous administration of glucose and arginine in fetal horses with respect to their gestational age and concentration of cortisol, the hormone responsible for prepartum maturation of other fetal tissues. Glucose administration had no effect on fetal insuli...
The Journal of physiologyOctober 6, 2000
Volume 528 Pt 1, Issue Pt 1 209-219 doi: 10.1111/j.1469-7793.2000.00209.x
Fowden AL, Taylor PM, White KL, Forhead AJ.1. Using the Fick principle and tracer methodology, the metabolic rates of chronically catheterized fetal foals (n = 24) were measured at different gestational ages during the second half of gestation and in response to maternal fasting for 36 h in late gestation (n = 4, term approximately 335 days). 2. Absolute rates of umbilical blood flow, fetal glucose utilization and umbilical uptake of oxygen (O2) and glucose increased from mid-gestation to 300 days and then plateauxed until term. The absolute rate of umbilical lactate uptake was significant after, but not before, 280 days of gestation. ...
Stanek KA, Nagle FJ, Bisgard GE, Byrnes WC.Published reports of oxygen consumption (VO2) during exercise in hyperoxia are equivocal. By and large, when measured at the lung using respiratory gas equations, VO2 is elevated in hyperoxia and, when measured at the blood-tissue level using the cardiovascular Fick (CVF) equation, it is unchanged. We sought to provide some insight into this problem by making through the use of both equations simultaneous determinations of VO2 during hyperoxia in exercising ponies. In normoxia, during treadmill exercise (115 m/min, 10% grade) of seven ponies, there was no difference in exercise VO2, whether it...
Bhuyan AK, Udgaonkar JB.The unfolding kinetics of horse cytochrome c in the oxidized state has been studied at 10, 22, and 34 degreesC as a function of guanidine hydrochloride (GdnHCl) concentration. Rapid (millisecond) measurements of far-UV circular dichroism (CD) as well as fluorescence quenching due to tryptophan to heme excitation energy transfer have been used to monitor the unfolding process. At 10 degreesC, the decrease in far-UV CD signal that accompanies unfolding occurs in two phases. The unobservable burst phase is complete within 4 ms, while the slower phase occurs over tens to hundreds of milliseconds. ...
Koho NM, Hyyppä S, Pösö AR.Monocarboxylate transporters (MCT) facilitate the transport of lactate across membranes. In red blood cells (RBC) the transport activity varies interindividually due to differences in the amount of an ancillary protein CD147. Similar variations in muscles could have a great influence on lactate accumulation during exercise. Objective: To study the expression of MCT isoforms and CD147 in the middle gluteal muscle. Methods: Venous blood and muscle biopsy samples were taken from 14 Standardbred horses. Lactate transport activity in RBC and the amounts of MCT1, 2, 4 and CD147 were measured. Result...
Anderson MG, Aitken MM.Adrenaline was given intramuscularly to resting horses. It increased heart rate, sweating, blood levels of lactic dehydrogenase, aldolase, creatine kinase, glucose, lactate, free fatty acids and glycerol. Responses to isoprenaline, to noradenaline and to adrenaline after pretreatment with propranolol indicated that beta receptors were involved in stimulation of tachycardia, sweating, lipolysis and muscle glycogenolysis, and alpha receptors in stimulation of liver glycogenolysis and leakage of intracellular enzymes. The time course and relative magnitude of the effects on different enzymes was ...
Meng S, Zhang Y, Lv S, Zhang Z, Liu X, Jiang L.With their enormous muscle mass and athletic ability, horses are well-positioned as model organisms for understanding muscle metabolism. There are two different types of horse breeds-Guanzhong (GZ) horses, an athletic breed with a larger body height (~148.7 cm), and the Ningqiang pony (NQ) horses, a lower height breed generally used for ornamental purposes-both inhabited in the same region of China with obvious differences in muscle content. The main objective of this study was to evaluate the breed-specific mechanisms controlling muscle metabolism. In this study, we observed muscle glycogen, ...
Sewell DA, Harris RC.Adenine nucleotide (AN) degradation has been shown to occur during intense exercise in the horse and in man, at or close to the point of fatigue. The aim of the study was to compare the concentrations of muscle inosine 5'-monophosphate (IMP) and plasma ammonia (NH3) during intense exercise with the concentrations of muscle and blood lactate. Seven trained thoroughbred horses were used in the study. Each exercised on a treadmill for periods of between 30 s and 150 s, at 11 and/or 12 m.s-1. Blood and muscle samples were taken and analysed for lactate and NH3 and adenosine 5'-triphosphate (ATP), ...
Kalashnikov V, Zajcev A, Atroshchenko M, Miroshnikov S, Frolov A, Zav'yalov O, Kalinkova L, Kalashnikova T.A study on the Russian trotting breeds was conducted to assess the impact of horses' sporting results and the degree of accumulation of chemical elements in the hair. In the first phase of the research, the elemental composition of the mane hair of trotter horses (n = 215) was studied. Based on these studies, percentile intervals for the distribution of concentrations of chemical elements in the hair have been established, and the values of 25 and 75 percentile adopted as a "physiological standard" have been defined. In the second stage of the research into clinically healthy Russian trott...
Rose RJ, Hodgson DR, Kelso TB, McCutcheon LJ, Bayly WM, Gollnick PD.Changes in blood gases, ions, lactate, pH, hemoglobin, blood temperature, total body metabolism, and muscle metabolites were measured before and during exercise (except muscle), at fatigue, and during recovery in normal and acetazolamide-treated horses to test the hypothesis that an acetazolamide-induced acidosis would compromise the metabolism of the horse exercising at maximal O2 uptake. Acetazolamide-treated horses had a 13-mmol/l base deficit at rest, higher arterial Po2 at rest and during exercise, higher arterial and mixed venous Pco2 during exercise, and a 48-s reduction in run time. Ar...
Tevell A, Bondesson U, Törneke K, Hedeland M.The metabolism of clemastine was studied in dogs, horses, and humans after a single dose of Tavegyl. The urine collected was extracted by solid-phase extraction or hydrolyzed with beta-glucuronidase and then extracted by liquid-liquid extraction, prior to analysis for unchanged drug and phase I and II metabolites by liquid chromatography/tandem mass spectrometry. The metabolites were identified by their molecular mass and interpretation of the product ion spectra, since no standard substances were available. Unchanged drug was recovered in urine samples from dogs and humans, but not from horse...
Hodgson DR, Rose RJ, Dimauro J, Allen JR.Biopsy samples were obtained from the middle gluteal muscle of 10 Thoroughbred horses undergoing a commercial race-training program. Samples were obtained before the program began and again after 6 and 12 weeks of training. All horses had raced at least once by the 12th week of training. Serial sections of muscle were examined histochemically for myosin adenosinetriphosphatase after either acid (pH 4.3 and 4.6) or alkaline (pH 10.3) preincubation, and then muscle fibers were identified as types I, IIA, IIB, or IIC. The oxidative capacity of individual fibers was assessed, using the reduced nic...
French K, Pollitt CC, Pass MA.Experiments were performed to establish the pharmacokinetics of triamcinolone acetonide and the effects of the glucocorticoid on glucose metabolism in horses. The pharmacokinetics after intravenous (i.v.) dosing was best described by a three-compartment open model. There was rapid distribution from the central compartment followed by two phases of elimination. The half-life of the rapid elimination phase was 83.5 min and of the slower phase was 12 h. The term (Vss/Vc)-1was 12.3 indicating extensive distribution into the tissues. Triamcinolone acetonide given i.v. or intramuscularly (i.m. ) ind...
Zeyner A, Kirchhof S, Susenbeth A, Südekum KH, Kienzle E.Few data on apparent pre-caecal digestibility (APCD) of crude protein (CP) and particularly amino acids (AA) are available from studies with horses. Protein bound in cell walls (i.e. neutral detergent insoluble CP (NDICP)) is unlikely to be decomposed by digestive enzymes in the small intestine. In contrast the corresponding analytical fraction of neutral detergent soluble CP (NDSCP) (NDSCP = CP-NDICP) is likely to be available for auto-enzymatic digestion. A literature analysis on the relationship between NDICP/NDSCP and pre-caecal indigestible/digestible CP was carried out. There was a str...
Bröjer J, Holm S, Jonasson R, Hedenström U, Essén-Gustavsson B.The degradation of glycogen and its two forms, proglycogen (PG) and macroglycogen (MG) has been studied in horses performing different types of exercise, but no information is available about the resynthesis of PG and MG after exercise. Objective: To determine the resynthesis of PG and MG in skeletal muscle after intermittent uphill exercise. Methods: At a training camp 9 well-trained Standardbred trotters performed a training session comprising a warm-up period, 7 repeated 500 m bouts of exercise on an uphill slope and a recovery period. Muscle biopsies (m. gluteus medius) for analysis of PG,...
Evans DL, Priddle TL, Davie AJ.Relationships between racing performance and plasma lactate and uric acid concentrations after racing were investigated in pacing Standardbred racehorses. The study was undertaken in order to better understand factors that limit racing performance. Twenty horses were tested after races of 1760 m and 28 horses after races over 2160 m. Blood samples were taken 30-60 min before and 8 and 30 min after a race. There were no significant differences between the race distances for prerace and 8 min postrace plasma lactates. Significant low correlations were obtained for plasma lactate concentration 8 ...
Gretler SR, Finno CJ, Kass PH, Knych HK.In humans, the drug metabolizing enzyme CYP2D6 is highly polymorphic resulting in substantial differences in the metabolism of drugs including anti-arrhythmics, neuroleptics, and opioids. The objective of this study was to phenotype a population of 100 horses from five different breeds and assess differences in the metabolic activity of the equine CYP2D6 homolog using codeine as a probe drug. Administration of a probe drug is a common method used for patient phenotyping in human medicine, whereby the ratio of parent drug to metabolite (metabolic ratio, MR) can be used to compare relative enzym...
Wilgus H, Stellwagen E.Changes in the visible absorbance spectra of complexes of horse heart cytochrome c hemopeptide 1-65, peptide 66-104, and their guanidinated counterparts are compared with those characteristic of native and fully guanidinated ferricytochrome c over the pH range 7 to 11. Upon raising the pH, the methionine ligand in the guanidinated hemopeptide 1-65.peptide 66-104 complex is replaced by a strong field ligand. By contrast, the methionine ligand in the hemopeptide 1-65.guanidinated peptide 66-104 is replaced by a weak field ligand. These results demonstrate that lysine 13 does not ligate with the ...
Kollias-Baker C, Cox K, Jones J.Omeprazole is a proton-pump inhibitor recently approved in the United States for the treatment of gastric ulcer disease in horses. A study was designed to determine the effects of omeprazole treatment on the physiological indices of performance of horses during incremental treadmill exercise. In a crossover-design study carried out over 2 weeks, five horses completed standardized incremental exercise tests on a high-speed treadmill either with no treatment or treatment with omeprazole. No statistically significant effects of omeprazole were found on the mean maximum responses for specific oxyg...
Williams CA, Carlucci SA.Vitamin E is the most commonly supplemented antioxidant in horses; however, previous research is not conclusive as to the recommended level for exercising horses. Objective: To evaluate the effects of 3 levels of vitamin E supplementation on oxidative stress and vitamin/antioxidant status in intensely exercised horses to determine the optimal level of vitamin E supplementation. Methods: Twelve unfit Standardbreds were divided into 3 groups, supplemented orally with 0 (CON), 5000 (MOD), or 10,000 (HI) iu/day of DL-alpha-tocopheryl acetate. The 3 x 3 Latin square design consisted of three 4 week...
Marth CD, Young ND, Glenton LY, Noden DM, Browning GF, Krekeler N.The physiological changes associated with the varying hormonal environment throughout the oestrous cycle are linked to the different functions the uterus needs to fulfil. The aim of the present study was to generate global gene expression profiles for the equine uterus during oestrus and Day 5 of dioestrus. To achieve this, samples were collected from five horses during oestrus (follicle >35 mm in diameter) and dioestrus (5 days after ovulation) and analysed using high-throughput RNA sequencing techniques (RNA-Seq). Differentially expressed genes between the two cycle stages were further inves...
Peters LM, Demmel S, Pusch G, Buters JT, Thormann W, Zielinski J, Leeb T, Mevissen M, Schmitz A.Ketamine is an anesthetic and analgesic regularly used in veterinary patients. As ketamine is almost always administered in combination with other drugs, interactions between ketamine and other drugs bear the risk of either adverse effects or diminished efficacy. Since cytochrome P450 enzymes (CYPs) play a pivotal role in the phase I metabolism of the majority of all marketed drugs, drug-drug interactions often occur at the active site of these enzymes. CYPs have been thoroughly examined in humans and laboratory animals, but little is known about equine CYPs. The characterization of equine CYP...
Jones JH, Ohmura H, Stanley SD, Hiraga A.Human athletes run faster and experience fewer injuries when running on surfaces with a stiffness 'tuned' to their bodies. We questioned if the same might be true for horses, and if so, would running on surfaces of different stiffness cause a measurable change in the amount of energy required to move at a given speed? Objective: Different brands of commercial treadmills have pans of unequal stiffness, and this difference would result in different metabolic power requirements to locomote at a given speed. Methods: We tested for differences in stiffness between a Mustang 2200 and a Säto I comme...
Burnley M.The parameters of the hyperbolic speed-duration relationship (the asymptote critical speed, CS, and the curvature constant, D') provide estimates of the maximal steady state speed (CS) and the distance an animal can run, swim, or fly at speeds above CS before it is forced to slow down or stop (D'). The speed-duration relationship has been directly studied in humans, horses, mice and rats. The technical difficulties with treadmill running in dogs and the relatively short greyhound race durations means that, perhaps surprisingly, it has not been assessed in dogs. The endurance capabilities of li...
Stefánsdóttir GJ, Ragnarsson S, Gunnarsson V, Roepstorff L, Jansson A.This study compared the effect of ridden tölt and trot at 3 speeds on physiological responses in trained adult (15.3 ± 1.6 yr) Icelandic horses. The experiment had a crossover design with 8 horses, 2 treatments (incremental exercise test in tölt and trot), and 2 riders. Each horse performed 2 tests per day (1 gait with 2 riders, minimum 4.5 h between) on 2 separate days, with 1 d of rest in between. The exercise test consisted of three 642-m phases at 3.0 m/s (Speed), 4.0 m/s (Speed), and 5.0 m/s (Speed) and was performed outdoors on a 300-m oval gravel riding track in northern Iceland in M...
Corado CR, McKemie DS, Knych HK.OBJECTIVE To characterize polymorphisms of the gene for cytochrome P450 isozyme 2D50 (CYP2D50) and the disposition of 2 CYP2D50 probe drugs, dextromethorphan and debrisoquine, in horses. ANIMALS 23 healthy horses (22 Thoroughbreds and 1 Standardbred). PROCEDURES Single-nucleotide polymorphisms (SNPs) in CYP2D50 were identified. Disposition of dextromethorphan (2 mg/kg) and debrisoquine (0.2 mg/kg) were determined after oral (dextromethorphan) or nasogastric (debrisoquine) administration to the horses. Metabolic ratios of plasma dextromethorphan and total dextrorphan (dextrorphan plus dextrorph...
Rourke KM, Kohn CW, Levine AL, Rosol TJ, Toribio RE.Calcium has important physiological functions, and disorders of calcium homeostasis are frequent in horses. We have made important progress understanding equine calcium homeostasis; however, limited information on equine calcitonin (CT) is available, in part because of the lack of validated CT assays. To determine the CT response to high ionized calcium (Ca(2+)) concentrations in healthy horses, we induced hypercalcemia in 10 healthy horses using a calcium gluconate 23% solution (5mg/kg; 120 mL/500 kg horse) infused over 4 min. Four horses were infused with 120 mL of 0.9% NaCl and used as cont...
