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.
Kohn CW, Brooks CL.Blood, serum, and plasma total calcium concentrations and plasma and serum ionized calcium concentrations were anaerobically determined by use of a calcium-specific electrode for samples obtained from 39 healthy horses. Mean (+/- SD) serum ionized calcium concentration was 6.6 +/- 0.3 mg/dl (1.6 +/- 0.1 mmol/L) and the mean serum ionized calcium percentage was 58.2 +/- 3.4%. Serum ionized calcium percentage was not significantly correlated with serum pH. Plasma ionized calcium percentage was weakly correlated with plasma pH (r = -0.480; P less than or equal to 0.05). Ionized calcium concentrat...
Donoghue S, Meacham TN, Kronfeld DS.Cumulative nutritional demands on good brood mares are unrivalled among domestic livestock, but little attention has been given to the influence of nutrition on their reproductive performance and efficiency. We suggest that part of the decline in racing performance of progeny of mares over 10 years of age may be caused by suboptimal nutrition. This article contrasts the concepts of minimal and optimal nutrient requirements, revives Hammond's concept of nutrient partitioning to the conceptus and mammary gland, and discusses energy and nutrient requirements during gestation and lactation. Furthe...
Houpt KA.In summary, horses spend 60% or more of their time eating when grazing or when feed is available free choice. Grasses are their preferred food, but they supplement the grass with herbs and woody plants. Sweetened mixtures of oats and corn are the most preferred concentrate. Horses can increase or decrease the time spent eating and amount eaten to maintain caloric intake. Their intake is stimulated by drugs such as diazepam and by the presence of other horses. Horses stop eating when gastric osmolality increases; increases in plasma osmolality, protein, and glucose accompany digestion. Foals ea...
Lawrence LM.Substrate depletion and end product accumulation are two important factors in exercise fatigue. Fatigue during long-term exercise results from a depletion of muscle and liver glycogen and coincides with an inability to maintain blood glucose levels. During high intensity exercise, the rapid catabolism of carbohydrate and the resultant production of lactate and hydrogen ions cause a reduction in muscle pH that inhibits maximum force generation. Dietary manipulations that can influence carbohydrate status or lactate accumulation may be beneficial to performance. In human athletes, carbohydrate l...
Maylin GA, Bache CA, Lisk DJ.Effluents from a number of industries which are typically treated in municipal sewage plants result in cadmium-containing sludge. Disposal of such sewage sludge by application to agricultural land can result in uptake of cadmium by crops. In this study, oats were grown on soils which had been amended with sewage sludge from Syracuse, New York. The cadmium concentration in the sludge-grown oats was 1.79 ppm dry weight. Horses were fed the sludge-grown oats for 6 weeks during which time blood samples were taken for the determination of cadmium. No significant differences (p greater than 0.05) we...
Ono K, Inui K, Hasegawa T, Matsuki N, Watanabe H, Takagi S, Hasegawa A, Tomoda I.The change in activities of 3 major antioxidative enzymes in equine erythrocytes, superoxide dismutase (SOD), glutathione peroxidase (GSHpx), and catalase, was investigated in order to evaluate the effect of exercise. Blood samples were obtained from 11 thoroughbred horses before and immediately after vigorous exercise which induced the increase of plasma lipid peroxide (Lpx) concentration from 1.16 +/- 0.40 nmol/ml to 1.29 +/- 0.34 nmol/ml. Following the exercise, the GSHpx activity in erythrocytes was significantly reduced from 69 +/- 10 IU/gHb to 65 +/- 8 IU/gHb, whereas SOD and catalase ac...
Goetz TE, Manohar M.The effect of age on maximal heart rate induced by IV infusion of isoproterenol was studied in 19 healthy, sedentary, normothermic horses ranging in age from 0.25 to 9.90 years. Isoproterenol was administered IV (1.0 micrograms/kg of body weight/min) for 3 minutes, and the heart rate attained during the last 30 seconds of the infusion was determined. Linear regression of the maximal heart rate on age suggested that the rate decreased with age in a trend described by the equation: maximal heart rate (beats/min) = 209.63 - 3.28 x age (years). The regression coefficient (r) for this relation was ...
Haywood PE, Teale P, Moss MS.Thoroughbred geldings were fed racehorse cubes containing a predetermined concentration of theobromine in the form of cocoa husk. They were offered 7 kg of cubes per day, divided between morning and evening feed, and food consumption was monitored. Urinary concentrations of theobromine were determined following the consumption of cubes containing 11.5, 6.6, 2.0 and 1.2 mg per kg of theobromine, to verify whether or not such concentrations would produce positive urine tests. Pre-dose urine samples were collected to verify the absence of theobromine before each experiment. It became apparent fro...
Snow DH, Martin V.To investigate the claim that equine erythrocytes released from the spleen are older cells than those found at rest in the circulation, the 2,3, diphosphoglycerate (2,3 DPG), adenosine triphosphate (ATP) and creatine concentration of erythrocytes before and following splenic emptying were examined. Normal values for thoroughbreds (43) and ponies (10) at rest were established. Following either exercise or intravenous injection of adrenaline in six thoroughbreds, there was an increase in erythrocyte creatine content and a decrease in ATP concentration. Exercise produced a slight increase in 2,3 ...
Lindner A, Will Y, Wilkniss E, Chrispeels J.The influence of duration and temperature of storage on hormone levels of whole blood, plasma and serum of horses was investigated. Using FPIAs cortisol, T4 and T-uptake could be measured while the T3-FPIA did not work appropriately. Serum and Plasma stored under the same conditions did not show any difference in cortisol, T4 and T-uptake values. In frozen heparinized plasma samples analysed on different days the cortisol and T4 concentrations fluctuated markedly. The T-uptake values were rather stable. The smallest day by day changes of cortisol and T4 in plasma were found when storing the sa...
Carlin JI, Harris RC, Cederblad G, Constantin-Teodosiu D, Snow DH, Hultman E.Treadmill exercise of 2-min duration and increasing intensity resulted in increased formation of acetyl-CoA and acetylcarnitine in working muscle of Thoroughbred horses. At high work intensities a plateau was reached for both acetyl-CoA (approximately 50 mumols/kg dry muscle) and acetylcarnitine (approximately 20 mmol/kg dry muscle). Postexercise concentrations were significantly (P less than 0.001) correlated; [acetylcarnitine] = 349.[acetyl-CoA] + 2.4. The results indicate that approximately 350 mumols acetylcarnitine were accumulated for every 1 mumol acetyl-CoA. Under the conditions of exe...
Porter JK, Voss KA, Bacon CW, Norred WP.Fusarium moniliforme (FM) is associated with equine leukoencephalomalacia (ELEM) and hepatotoxicities in horses and rats. The neurochemical effects of ELEM-associated corn naturally infected with FM and FM strain MRC 826 were studied in rats. Increases in brain 5-hydroxyindoleacetic acid (5-HIAA, major metabolite of serotonin, 5-HT) and 5-HIAA/5-HT ratios were observed in rats fed the ELEM-FM corn. These rats had reduced body weights (17%, P less than 0.01) and increased brain weight/body weight ratios (14%, P less than 0.01) as compared with controls that were fed commercial corn. Rats fed a ...
Harkins JD, Kamerling SG, Bagwell CA, Karns PA.Eight horses with previous racing experience were used in a comparative study of training methods for Thoroughbred racehorses. They were randomly assigned to two groups of four horses each. One group was trained using an interval training method (IT) and the other using conventional training (CT) methods. Peak heart rates, heart rate recovery curves, peak plasma lactate levels, plasma lactate clearance rates and run times were used to evaluate differences in the training methods. Peak heart rates, heart rate recovery curves, and run times were not significantly different between the groups. Ho...
Firth EC, Nouws JF, Klein WR, Driessens F.A pilot study in two ponies showed that the plasma concentrations of intramuscularly administered procaine penicillin were higher if phenylbutazone was administered concurrently. In two other trials, each involving five horses, intravenous sodium penicillin was administered with and without concurrent intravenously injected phenylbutazone, and procaine penicillin was injected intramuscularly with and without oral phenylbutazone. In both cases the plasma concentrations of penicillin were higher when phenylbutazone was given. The pharmacokinetic parameters indicated that the effect was probably ...
Seeherman HJ, Morris EA.This paper describes the methodology necessary to perform a clinical exercise test and the expected variability in an individual horse's exercise test measurements based on comparing the results of two repetitions of the test with six horses. The exercise test measurements were obtained with an open flow respiratory gas analysis system, fast time response lactate analyser and an on-board heart rate monitor during an incremental inclined treadmill exercise test. With the exception of peak venous lactate concentration (LACpeak), the results indicate that the mean variability in peak oxygen consu...
Rose RJ, Hodgson DR, Bayly WM, Gollnick PD.To determine whether maximum oxygen uptake (VO2max) in the horse in influenced by type of exercise test, five different protocols were evaluated in eight untrained Thoroughbreds exercised on a treadmill. With all protocols, horses were given a 5 min warm-up on a 10 per cent treadmill slope. Three protocols were at a 10 per cent slope and included: 1) increasing the running speed by 1 to 2 m/sec every 60 secs from 4 m/sec to a maximum of 12 m/sec; 2) running at 12 m/sec until fatigue; and 3) running for 3 to 4 mins at speeds ranging from 6 to 12 m/sec with rest pauses between exercise bouts. Th...
Thomas DP, Fregin GF.The purpose of the present study was to measure the time-course and degree of cardiovascular and respiratory 'drift' during constant submaximal exercise in the horse. One Thoroughbred and four Morgan mares were instrumented for simultaneous measurement of respiratory and blood gases which also enabled cardiac output (Q) to be calculated. Data were collected at rest, and at 10, 20 and 30 mins during a constant workload which elicited an initial exercising heart rate (HR) of 150 beats/min, and an approximate 15-fold increase in oxygen consumption (VO2). Significant cardiac and respiratory drift ...
Sexton WL, Erickson HH.Six ponies performed a standardised exercise test on a motorised treadmill at each of three randomly assigned treadmill elevations (1, 4, or 7 degrees). The exercise test consisted of four, 4 min increments of increasing treadmill speed from 1.0 to 3.4 m/sec. Heart rate, blood lactate concentration, and packed cell volume (PCV) were determined, during the last min of each exercise level, and at 4 and 12 mins post exercise. Regardless of treadmill elevation, no differences were observed in pre-exercise heart rate (49 +/- 2) beats/min), lactate (1.2 +/- 0.1 mM), and PCV (0.32 +/- 0.01 litres. Du...
Greenhaff PL, Snow DH, Harris RC, Roberts CA.Two studies were undertaken in an attempt to investigate the optimal dose, route and time course required to 'bicarbonate load' the Thoroughbred. During the first study a test solution of sodium bicarbonate (NaHCO3) and a control solution of water were administered via a nasogastric tube to six horses. Blood acid-base status was determined immediately prior to and for 24 h following intubation. During the second study a standardised feed was given to four horses, with and without NaHCO3 supplementation. This was followed by a further trial involving the addition of glucose and NaHCO3 to a stan...
Goetz TE, Manohar M.The heart rate (HR) induced by maximal beta-adrenergic activation, which was elicited by infusion of isoproterenol, was studied in 8 healthy horses before (control) and after hyperthermia was induced by IV administration of 2,4-dinitrophenol (DNP). Isoproterenol was administered IV at 1.0 micrograms.kg-1.min-1 for 3 minutes, and the HR was determined during the final 30 seconds of the infusion. As the rectal temperature increased (P less than 0.001) from 38.2 +/- 0.1 C (mean +/- SEM; normothermic control) to 40.1 +/- 0.1 C at 60 minutes after DNP administration, the isoproterenol-induced HR al...
Rej R, Rudofsky U, Magro A, Prendergast J.Aminotransferase activities were measured in the serum of two- to three-year-old Thoroughbred fillies and colts during a four week period of peak training for flat racing. Aspartate aminotransferase (AspAT, EC 2.6.1.1), mitochondrial aspartate aminotransferase (m-AspAT) and alanine aminotransferase (AlaAT, EC 2.6.1.2) activities in serum were measured and the relative proportions of apoenzyme and holoenzyme were determined. The aminotransferase activities were increased only slightly immediately following exercise. This small and immediate post exercise increase in activity did not vary greatl...
Tulamo RM, Saari H, Konttinen YT.Concentration of hyaluronate (HA) in equine serum was determined by a recently developed specific radioassay. The mean +/- SD HA concentration in equine serum was 288 +/- 145 micrograms/L, was age dependent, and varied widely between horses (range, 190 to 760 micrograms/L). Light or moderate exercise increased serum HA concentration from baseline values by 1.5- to 3-fold. In all horses, serum HA concentration returned to or below the original resting values 1 and 2 hours after exercise.
Cí·¯ord D, Woodhead A, Muirhead R.The potential of short-cutting cycle, high temperature-dried alfalfa as a source of calcium for horses was determined by means of a 4 x 4 Latin square digestibility trial using four thoroughbred horses (mean liveweight 531 kg). The four dietary treatments were timothy hay alone, 33 per cent alfalfa and 67 per cent timothy hay, 67 per cent alfalfa and 33 per cent timothy hay, and alfalfa alone. Significantly more calcium and magnesium were absorbed from the alfalfa than from the hay. Phosphorus absorption appeared to be unaffected by treatment. Alfalfa calcium was more available than timothy ha...
Escabias MI, Santisteban R, Rubio MD, Tovar P.The correlations between different electrocardiographic variables and plasma concentrations of K, Na and Ca ions were studied in foals of 1 to 14 days of age. The results obtained are only significant in neonate individuals of 1 day of age. Whilst the PQ segment and R wave duration showed a positive linear correlation (p less than or equal to 0.05) with plasma concentrations of Na and Ca ions respectively, the amplitude of the T wave showed a negative linear correlation (p less than or equal to 0.05) with the K ion. Moreover, the variability in duration of the QT and ST intervals can be explai...
Lepage OM, Marcoux M, Tremblay A.Levels of alkaline phosphatase and osteocalcin or bone Gla-protein, a new marker of bone metabolism, were analyzed in blood samples of 50 clinically normal female Standardbred horses between four months and twenty years of age. Samples were collected in the morning before exercise. Serum osteocalcin was measured by radioimmunoassay using bovine antibodies. There was a significant inverse correlation between alkaline phosphatase, osteocalcin and the age of the animals up to 48 months. The decrease in osteocalcin levels in serum was very marked during the first 30 months of life. The mean osteoc...
Clarke LL, Argenzio RA, Roberts MC.The effect of meal size and frequency on plasma volume, plasma aldosterone concentration and urinary Na and K clearances was determined in ponies. A daily maintenance ration of hay-grain pellets was provided either as a multiple feeding regimen, ie, 12 equal portions fed at 2-hour intervals, or as single large feedings, ie, half the ration fed every 12 hours at 0800 and 2000 hours. Only the effect of the single morning feeding was studied, using the latter regimen. Serial measurements of plasma volume were made by use of an indicator-dilution technique and indocyanine green (0.15 mg/kg of body...
Kline KH, Bechtel PJ.The purpose of this study was to investigate metabolic changes in equine muscle from birth to 1 yr of age. Duplicate biopsies from the middle portion of the gluteus medius were obtained from a depth of 2 cm beneath the superficial fascia at 1 day, 7 days, 1 mo, 3 mo, 6 mo, and 1 yr of age in 11 quarter horses and at 1 day, 3 mo, 6 mo, and 1 yr of age in 5 Standardbreds. Muscle enzyme activities determined were citrate synthase, 3-hydroxyacyl-CoA dehydrogenase, phosphorylase, and lactate dehydrogenase. Percent fast-twitch, fast-twitch high oxidative, and slow-twitch oxidative fiber types were d...
Snow DH.The haematological, biochemical and physiological changes associated with the cross-country stage of driving trials were studied in horses and ponies competing in singles, pairs, tandems and teams at five, five-section and two, three-section events. Heart rates were monitored continuously and sometimes exceeded 200 beats/minute. The highest maximum, mean and recovery heart rates were found after the most severe competitions. Rectal temperatures were also highest after the most severe events and in some animals exceeded 41 degrees C. Respiratory rates were very variable. Blood taken five minute...
Baker SJ, Gerring EL, Fox MT.Gastric pH varied widely among eight fasted ponies, of which seven exhibited discrete episodes of spontaneous alkalinisation (SA). SA occurred at all times of the study and no significant variation in the summary variables of pH (median pH, mean pH and percentage of readings exceeding pH 4.0) was noted among the periods 0 to eight, eight to 16 and 16 to 24 hours. The occurrence of SA has significant implications for the performance of acid secretory studies in the fasted pony. There was, however, no significant correlation between pH and plasma gastrin concentration measured using a commercial...
Teixeira FA, Araújo AL, Ramalho LO, Adamkosky MS, Lacerda TF, Coelho CS.The aim of this study was to evaluate the effects of oral creatine supplementation on the athletic performance of equines used for barrel racing. Ten healthy Quarter Horses, or Quarter Horse crossbred, weighing 429.7 ± 25.3 kg and with mean age of 3.8 ± 1.2 years, were used. Animals were evaluated in four different moments (M1, M2, M3, M4), and between M3 and M4, they were supplemented with 28 g of creatine/100 kg of body weight, orally, for 45 days. Although significant alterations for LDH activity, plasma glucose and packed cell volume were observed, it was possible to conclude th...
Mellor DJ.Physiological challenges facing the perinatal individual are huge. This is partly because of the marked and abrupt change from the intrauterine to the extrauterine environment, but also because the physiological responses to that change depend upon systems whose maturation is affected markedly by birth. Perinatal maturation appears, therefore, both to precede and accompany the physiological adaptations required for neonatal survival. This review does not provide a comprehensive coverage of perinatal physiology but directs attention towards evaluating constraints on foetal and neonatal thermoge...
Aramaki S, Mori M, Nakata M, Shinohara A, Koizumi T.The pharmacokinetics characteristics of propranolol (PPL) in horses was studied by administering the drug intravenously or orally to the animals. The predominant primary pathway was ring oxidation, and 4-hydroxypropranolol glucuronide (4-OHPG) was the major metabolite in both plasma and urine. Side-chain glucuronidation and oxidation were not significant. A two-compartment model was employed for PPL followed by a one-compartment model for 4-OHPG. After oral administration, one-step absorption and two-step first pass metabolism were employed. The fraction absorbed of PPL was approximately 70% a...
Harris P.This review outlines the energy sources available to the horse, from its diet and from its body stores, at rest and while exercising. It looks at the current ways of describing the energy potential of diets fed to horses and discusses the relative advantages and disadvantages of the digestible energy and net energy systems. The more empirical net energy system for calculating the energy available for maintenance and work is compared with a more physiological partitioning system. Finally, the energy requirements for maintenance and exercise are discussed, together with how they may be practical...
Dunnett CE, Marlin DJ, Harris RC.The aim of the present study was to relate changes in muscle oxidative capacity and free fatty acid flux in response to oil supplementation to fuel utilisation during subsequent exercise of varying intensities. Following 10 weeks of oil supplementation there was an increased capacity for fat utilisation during low and moderate intensity exercise as indicated by a lower respiratory exchange ratio (RER) (P<0.05). We suggest that this was contributed to by a parallel increase in the oxidative capacity of muscle as indicated by a significant increase in the activity of muscle citrate synthase (...
Gordon ME, Edwards MS, Sweeney CR, Jerina ML.The objective of this study was to test the hypothesis that an equine diet formulated with chelated trace minerals, organic selenium, yeast culture, direct-fed microbials (DFM) and Yucca schidigera extract would decrease excretion of nutrients that have potential for environmental impact. Horses were acclimated to 100% pelleted diets formulated with (ADD) and without (CTRL) the aforementioned additives. Chelated sources of Cu, Zn, Mn, and Co were included in the ADD diet at a 100% replacement rate of sulfate forms used in the CTRL diet. Additionally, the ADD diet included organic selenium yeas...
Hyyppä S.To test the effect of nandrolone on their recovery, six adult half-bred riding horses performed a competition exercise test (CET) and a standardized exercise test (SET) on consecutive days before and after a 2-week treatment with the anabolic steroid nandrolone laurate. Blood samples were collected during and between these tests for the determination of red cell volume and concentrations of blood lactate, plasma glucose, non-esterified fatty acids, glycerol, triglycrides, erythropoietin, cortisol, insulin, and glucagon. Muscle biopsy specimens were taken immediately after the CET and before th...
Abo El Sooud K.The pharmacokinetics of gentamicin was studied in lambs, calves and foals, respectively after single intravenous (i.v.) injections of 5 mg kg(-1) body weight. The plasma concentration-time curves of gentamicin sulphate were best fitted to follow a two-compartment open model in calves and foals and a three-compartment open model in lambs. Gentamicin showed high plasma level at 5 min post-injection. Then its concentration decreased gradually until its minimum detectable level at 10 and 12 h post-injection in foals and calves, respectively, was reached. In contrast, the plasma concentrations were...
Tanner SL, Wagner AL, Digianantonio RN, Harris PA, Sylvester JT, Urschel KL.The objective of this study was to measure whole-body protein kinetics in weanling horses receiving forage and one of two different concentrates: (1) commercial crude protein (CCP) concentrate, which with the forage provided 4.1 g CP/kg bodyweight (BW)/day (189 mg lysine (Lys)/kg BW/day), and (2) recommended crude protein (RCP) concentrate which, with the same forage, provided 3.1 g CP/kg BW/day (194 mg Lys/kg BW/day). Blood samples were taken to determine the response of plasma amino acid concentrations to half the daily concentrate allocation. The next day, a 2 h-primed, constant inf...
Philip M, Karakka Kal AK, Subhahar MB, Karatt TK, Mathew B, Perwad Z, Graiban FM, Caveney MR, Sayed R, Kadry AM.According to previous research, aminorex is the major metabolite of levamisole; however, in the screening of levamisole-positive racehorse urine and plasma samples, aminorex could only be detected in trace amounts or not at all. In forensic laboratories, hydroxy levamisole and its phase II conjugates make it easier to confirm levamisole misuse and to differentiate between the abuse of levamisole and aminorex. This study aimed to identify the major levamisole metabolites that can be detected along with the parent drug. Methods: The study describes levamisole and its metabolites in thoroughbred ...
Suska M, Skotnicka E.The aim of this study was to examine the relationships between the concentrations of ATP, ADP, AMP (HPLC methods), total nucleotide pool (TAN), adenylate energy charge (AEC) and Na(+), K(+)-ATPase erythrocytic activities (by Choi's method) of horses as a function of breed and sex. The studies were conducted on 54 horses (stallions and mares) of different constitution types: breathing constitution (Wielkopolska and Hanoverian breed) and digestive constitution (Ardenian breed). Horse erythrocytes, independently of examined breed, present low ATP concentration in comparison to other mammal specie...
Lindmark DG, Jarroll EL, Timoney PJ, Shin SJ.The energy metabolism of the English E-CMO strain of contagious equine metritis bacterium was studied in whole cells and cell extracts. This bacterium appears to have an active Krebs cycle and probably obtains energy by oxidative phosphorylation since glycolysis and the hexose monophosphate pathways appear to be absent. These conclusions are based on the findings that [U-14C]glucose incorporation by this bacterium is below the level of detection, and that respiration is stimulated by Krebs cycle intermediates (i.e., malate, citrate, and succinate), but not by glucose, fructose, maltose, or suc...
Jaraiz V, Rodriguez C, San Andres MD, Gonzalez F, San Andres MI.A disposition and bioequivalence study with a suxibuzone granulated and a suxibuzone paste oral formulation was performed in horses. Suxibuzone (SBZ) is a nonsteroidal anti-inflammatory drug, which was administered to horses (n = 6) at a dosage of 19 mg/kg bwt by the oral route (p.o.) in a two period cross-over design. Suxibuzone is very rapidly transformed into its main active metabolites, phenylbutazone (PBZ) and oxyphenbutazone (OPBZ). Therefore plasma and synovial fluid concentrations of SBZ, PBZ and OPBZ were simultaneously measured by a sensitive and specific high-performance liquid chro...
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...
Parks CM, Manohar M.In recent years, increasing attention has been focused on the physiological responses of the horse to maximal exercise. Cardiovascular response in near maximally exercised galloping ponies (heart rate 225 +/- 7 beats/min; whole body oxygen consumption 122 +/- 12 ml/min/kg) comprised a marked increase in blood flow to the cerebellum, myocardium, diaphragm and the working muscles, while renal blood flow decreased precipitously. Cerebral and brainstem perfusion did not vary from resting values. Transmural homogeneity of myocardial blood flow persisted during near maximal exercise. It was reported...
Jellyman JK, Allen VL, Holdstock NB, Fowden AL.Studies in humans and animals have linked abnormal programming of adult tissue function to excess glucocorticoids during perinatal development. The current study investigated the hypothesis that physiological variations in glucocorticoid concentrations during early neonatal life of the foal alter the secretory responses of the pancreatic β cells 2 and 12 wk after treatment. Spontaneously delivered foals received either saline or long-acting ACTH for 5 d from 1 d after birth to maintain an endogenous rise in cortisol concentrations. Starting at d 10, pancreatic β cell function was studied usi...
Littlejohn A, Snow DH.These studies investigated circulatory, respiratory and metabolic responses in four Thoroughbred geldings during the first 400 metres of galloping (mean speed 14.4 +/- 0.38 m.s-1), cantering (mean speed 10.0 +/- 0.61 m.s-1) and walking (mean speed 1.58 +/- 0.05 m.s-1) from a standing start. A radio-controlled device which collected blood samples anaerobically during each 100 m section of the exercise track allowed analyses of changes in and functional relationships of the variables measured. During the 400 m gallop, the mean heart rate (HR) increased from 125 to 201 beats.min-1 and the haemato...
Borgia LA, Valberg SJ, McCue ME, Pagan JD, Roe CR.To evaluate effects of fats with odd and even numbers of carbon atoms on muscle metabolism in exercising horses with polysaccharide storage myopathy (PSSM). Methods: 8 horses with PSSM (6 females and 2 males; mean +/- SD age, 6.3 +/- 3.9 years). Methods: Isocaloric diets (grain, triheptanoin, corn oil, and high-fat, low-starch [HFLS] feed) were fed for 3 weeks each; horses performed daily treadmill exercise. Grain was fed to establish an exercise target, and HFLS feed was fed as a negative control diet. Daily plasma samples were obtained. For each diet, a 15-minute exercise test was performed,...
Wensing T, van Gent DM, Schotman AJ, Kroneman J.(I) The lipid and lipoprotein concentrations in sera of 4 healthy and 9 hyperlipaemic patients were determined. From the results of the analyses, it is suggested that three types of hyperlipoproteinaemia can be distinguished in ponies: (a) Type 1, characterised by a very pronounced increase in only the very low density lipoproteins (VLDL); (b) Type 2, in which there is a pronounced increase in the chylomicrons (Chylo) and the very low density lipoproteins (VLDL); (c) Type 3, which can be the result of fasting and is characterised by a moderate increase in the concentration of chylomicrons and ...
Knych HK, McKemie DS, Kass PH, Stanley SD, Blea J.Ketoprofen is an anti-inflammatory drug that is commonly administered to racehorses for the alleviation of musculoskeletal pain and inflammation. This study represents a comprehensive examination of the metabolism (in vivo and in vitro), pharmacokinetics and ex vivo pharmacodynamics, of ketoprofen in horses. The in vitro metabolism as well as specific enzymes responsible for metabolism was determined by incubating liver microsomes and recombinant CYP450 and UGT enzymes with ketoprofen. For the in vivo portion, 15 horses were administered a single intravenous dose of 2.2-mg/kg ketoprofen. Blood...
Warner A, Mayhew IG.Anhidrosis is loss of the ability to sweat. The problem is seen in horses kept in a hot humid climate, and it may cause severe impairment of thermoregulation in the equine athlete. British Thoroughbreds imported to her tropical colonies are the earliest recorded cases, and since then the syndrome has come to be described as one of Thoroughbreds, usually performance athletes, undergoing acclimatization to heat and humidity. A recent epidemiologic study of cases in Florida has shown, however, that many different breeds, and long time inhabitants of a hot climate, may be affected. Equine sweat gl...
Urschel KL, McKenzie EC.Skeletal muscle comprises 40% to 55% of mature body weight in horses, and its mass is determined largely by rates of muscle protein synthesis. In order to support exercise, appropriate energy sources are essential: glucose can support both anaerobic and aerobic exercise, whereas fat can only be metabolized aerobically. Following exercise, ingestion of nonfiber carbohydrates and protein can aid muscle growth and recovery. Muscle glycogen replenishment is slow in horses, regardless of dietary interventions. Several heritable muscle disorders, including type 1 and 2 polysaccharide storage myopath...
Rose RJ.In this article a physiological approach to fluid therapy is discussed, commencing with examination of fluid distribution in the normal horse. The functions of individual plasma electrolyte concentrations are considered and practical causes of acid-base disturbances discussed. When fluid administration is necessary, selection of the route for fluid administration as well as the type of fluid are important considerations and these must be adjusted to the needs of the individual case. Balanced polyionic solutions appear to be most suitable for general use because normal saline can produce hypoka...
Santos AS, Jerónimo E, Ferreira LM, Rodrigues MA, Bessa RJ.The potential use of odd- and branched-chain fatty acids (OBCFA) and purine bases (PB) as microbial markers in the equine hindgut was studied. For this purpose, feed particles adherent bacteria [solid associated bacteria (SAB)] and planktonic bacteria [liquid associated bacteria (PAB)] were isolated from total cecum and colon contents of 8 healthy, crossbred horses (9 ± 3 yr). Horses were fasted for 12 to 15 h before slaughter, and the cecum and colon were identified and clamped in their extremities to avoid mixing of digesta contents. The total cecum or colon contents was collected into ther...
Peretich AL, Abbott LL, Andrews FM, Dhar MS.To determine whether expression of mRNA for sodium-potassium adenosine-triphosphatase (NAKA) and sodium-hydrogen exchanger (NHE) in samples of the nonglandular portion of the equine gastric mucosa was altered by exposure to volatile fatty acids (VFAs) in an acidic environment. Methods: 10 horses (5 or = 12 years old). Methods: Samples of the nonglandular portion of the gastric mucosa were collected and exposed in Ussing chambers to Ringer's solution (control samples), Ringer's solution containing a mixture of VFAs (pH, 1.5 or 4.0), or Ringer's solution containing acetic acid (pH, 1.5 or 4.0)....
Luethy D, Johnson AL, Stefanovski D, Boston RC, Orsini JA.Equine metabolic syndrome (EMS) is prevalent in the equine population, and somatostatin analogs might be useful for diagnosis and/or treatment of EMS in horses. The purpose of this study was to evaluate the glucose and insulin responses to subcutaneous and intravenous administration of somatostatin. Six healthy research horses were included in this prospective study. An initial pilot study was performed to assess several different doses (10-22 µg/kg [4.5-10 µg/lb]) in two horses, then a final dosage of 22 µg/kg (10 µg/lb) was administered to six horses IV and SQ in a two-period random...
Bohar Topolovec M, Kruljc P, Prošek M, Jazbec Križman P, Smidovnik A, Nemec Svete A.Coenzyme Q10 (CoQ10) is an essential cofactor in the mitochondrial electron transport pathway, and is also the only known endogenously synthesized lipid-soluble antioxidant. The aim of the present study was to determine, for the first time, endogenous plasma CoQ10 concentration and its correlation with plasma total antioxidant capacity (TAC) and serum total cholesterol (TC) in a population of healthy untrained horses. Thirty-one horses were included in the study. Plasma CoQ10 concentration ranged from 0.380 to 2.090 mg/L, which is in general agreement with plasma CoQ10 concentration in humans....
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...
Paradis MR, Breeze RG, Bayly WM, Counts DF, Laegreid WW.The hematologic and pathologic effects of orally administered L-tryptophan and indoleactic acid and of L-tryptophan administered IV were studied in ponies. Sixteen adult Shetland ponies were allotted into 4 experimental groups. Group 1 consisted of 5 ponies (1-5) given 0.6 g of tryptophan/kg of body weight in a water slurry via stomach tube. Group 2 included 4 ponies (6-9) given 0.35 g of tryptophan/kg orally. Group-3 ponies (10-13) were given 0.35 g of indoleacetic acid/kg orally. Group 4 consisted of 3 ponies (14-16) given a single 4-hour IV infusion of 0.1 g of tryptophan/kg. Restlessness, ...
