bluuebunny/crossref_metadata_2025_split huggingface dataset:
Environmental stress and 3‐day eventing: effects of altitude
Authors: FOREMAN J. H. , WALDSMITH J. K. , LALUM R. B. 
Published: June 2010

SummaryThree‐day event horses are subject to various external environmental stresses including changes in ambient temperature, humidity, altitude, and test severity. Considerable research on the adverse effects of increased heat and humidity preceded the 1996 Olympic Summer Games in Atlanta, Georgia USA, but no research has been done previously on the effects of altitude on 3‐day eventing. Physical and venous blood gas data were collected on horses (n = 24) competing in the High Prairie Preliminary (CCN*) and Intermediate (CCN**) 3‐day events and Preliminary Horse Trials in Parker, Colorado (1900 m above sea level). Despite the increased altitude, only post exercise rectal temperature and pH were higher (P<.05) whereas heart rate (HR), [K+], and ionised calcium (iCa++) were lower (P<.05) in 3‐day event horses compared to horse trial horses. All other variables (respiratory rate [RR], PCV, [Hb], Pco2, [tco2], [HCO3‐], BE, and [Na+]) were not different between groups (P>0.05). When these preliminary horse trial horses in Colorado were compared to those previously studied at preliminary horse trials at sea level in Arizona, post exercise HR and RR were higher (P<.05) and pH, Pco2, [tco2], [HCO3‐], BE and [iCa++] were lower (P<.05) at altitude. These data show that increased altitude (1900 m above sea level) was more stressful for 3‐day event horses, but did not result in the severe physiological changes and inability to complete prescribed exercise tests seen in previous studies with increased heat and humidity. It is clear from these and previous data that increased heat and humidity are the more important environmental stressors in 3‐day eventing.
Sweat production and localisation of carbonic anhydrase in the equine sweat gland during exercise at two ambient temperatures
Authors: DAHLBORN KRISTINA , JANSSON ANNA , NYMAN SARA , MORGAN KARIN , HOLM LENA , RIDDERSTRåLE YVONNE 
Published: June 2010

SummaryThe aim of this investigation was to study sweat production during exercise at 2 ambient temperatures (20°C and 35°C) and the concurrent localisation of carbonic anhydrase (CA) in the sweat gland. Horses develop alkalosis during prolonged exercise and the sweat contains HCO3‐. Carbonic anhydrase is therefore of interest since it catalyses the reaction CO2+ H2O ↔ HCO3‐ + H+. Four standardbred trotters performed an exercise test. Skin biopsies were taken from the neck, and sweat rate, blood and skin temperatures were measured. There was a close relationship between sweat rate, temperatures and work intensity at 20°C. Temperatures and sweat rate were higher at 35°C and did not fall when the work intensity dropped. A significant decrease in the sweat gland cell area was found after exercise at 35°C with an accompanying decrease of vesicles. Strong CA activity was present at the luminal cell membrane and weaker basolaterally. The staining intensity increased after exercise. We suggest that CA might be of importance for counteracting the alkalosis developed after exercise by delivering HCO3‐ for generation of the alkaline pH in sweat.
Effects of potassium intake on potassium, sodium and fluid balance in exercising horses
Authors: JANSSON ANNA , LINDHOLM A. , LINDBERG J. E. , DAHLBORN KRISTINA 
Published: June 2010

SummaryThe aim of this study was to investigate the adaptation to an increased potassium (K+) intake in horses and to study whether the regulation of the post exercise K+, sodium (Na+) and fluid balances were altered by an increased K+ intake. Four Standardbred horses were fed 2 levels (4.1 and 5.4 mmol/kg bwt/day) of K+ for 17 days in a crossover design. The effects on K+, Na+ and fluid balance were studied both at rest and in response to 29 km exercise. K+, Na+ and fluid intakes and outputs were balanced within 24 h after a new diet had been introduced. Adaptation consisted primarily of an increased urinary K+ excretion, later followed by an increase in faecal excretion. The increased urinary K+ excretion was associated with an increased mass of urine (1.2–1.4 kg/day) compensated for by an increased water intake. The sweat Na+ concentration was increased on the highest K+ intake (from 123 ± 5 mmol/l to 138 ± 3 mmol/l) and the urinary Na+ excretion was lower post exercise on this diet. There were no differences in the magnitude of post exercise hypokalaemia between the diets, and plasma K+ concentration was still reduced 24 h post exercise even when the horses were fed the higher K+ diet. Adaptation to an increased K+ intake was rapid in these horses and consisted mainly of an increased urinary excretion. The response to exercise was unaltered by the increased K+ intake, except for an increased Na+ concentration in sweat.
Electrolyte and glycerol supplementation improve water intake by horses performing a simulated 60 km endurance ride
Authors: DüSTERDIECK KATJA F. , II H. C. SCHOTT , EBERHART SUSAN W. , WOODY KRISTINA A. , COENEN M. 
Published: June 2010

SummaryTo replace electrolytes lost in sweat during endurance competitions, riders frequently supplement horses with hypertonic oral electrolyte pastes. To determine whether this practice and concurrent administration of the so‐called hyperhydrating substance glycerol are of benefit, weight loss, voluntary water intake, plasma osmolality, and plasma protein and electrolyte concentrations were measured in 6 Arabian horses supplemented with a total of 2.4 ml/kg bwt of water (W); 0.2 g/kg bwt KCl and 0.4 g/kg bwt NaCl in 2.4 ml/kg bwt of water (E); or 0.2 g/kg bwt KCl and 0.4 g/kg bwt NaCl in 2.4 ml/kg bwt (3 g/kg bwt) of glycerol (GE) before and during a treadmill exercise test simulating a 60 km endurance ride. Weight loss was greater (P<.01) with W (3.2%) than with E and GE (1.0% and 0.9%, respectively) and was associated (r=‐0.85, P<.0001) with less (P<.01) water intake with W (12.2 l) than with E or GE (23.5 l and 25.81, respectively). Plasma osmolality increased to a greater extent (P<.01) with GE than with E and was unchanged with W. In contrast, plasma protein concentration decreased (P<.01) in the later stages of the simulated ride with E and GE, reflecting plasma volume expansion, but remained unchanged with W. Plasma Na+and Cl−concentrations increased (P<.01) with E and GE and were greater (P<.01) than values for W during the second half of the 60 km simulated ride. Despite administration are large amounts of potassium with E and GE, plasma K+concentration was decreased (P<.01) at the end of the rest breaks during the simulated ride and after 60 min of recovery with all supplements. Adverse effects of administration of hypertonic oral electrolyte pastes were not observed and decreases in plasma protein concentration within 30 min after drinking with all supplements suggested that intestinal absorption was well maintained during the simulated endurance ride. In conclusion, electrolyte supplementation in the form of hypertonic oral pastes improved water intake during endurance exercise but concurrent glycerol administration provided no additional benefits in comparison to supplementation with electrolytes alone.
Electrolyte vs. glucose‐electrolyte isotonic solutions for oral rehydration therapy in horses
Authors: MONREAL L. , GARZóN N. , ESPADA Y. , RUIZ‐GOPEGUI R. , HOMEDES J. 
Published: June 2010

SummaryAn isotonic electrolyte solution with a composition similar to equine sweat was compared to an isotonic glucose‐glycine‐electrolyte solution for oral rehydration therapy in exercising horses. Ten horses were dehydrated by using frusemide and allocated randomly to receive 4 different oral solutions: isotonic sweat‐like electrolyte solution, half‐strength hypotonic electrolyte solution, isotonic glucose‐glycine‐electrolyte solution, and plain water. Solutions were given by nasogastric tube using the same volume as the bodyweight lost by each horse. Blood samples were collected before and throughout 6 h of the rehydration period. Results showed that all solutions recovered pre‐frusemide values of packed cell volume (PCV) and total plasma protein (TP) in a similar fashion. No changes for Na+values were observed during the rehydration period when the isotonic sweat‐like solution was used. However, a significant hyponatraemia was induced throughout rehydration when the other 3 solutions were given, especially when hypotonic solution and water were used. Osmolality values did not change when both isotonic solutions were administered; but a significant hypotonicity was observed when hypotonic solution and water were given. When the isotonic sweat‐like solution was used, plasma Cl−, K+and creatinine values recovered to premedication values significantly faster than the other 3 solutions. In conclusion, the isotonic sweat‐like electrolyte was the best solution because it restored rapidly the fluid and plasma electrolyte imbalances. In contrast, the isotonic glucose‐glycine‐electrolyte solution impaired the plasma electrolyte imbalances.
Weak acid‐concentration Atotand dissociation constant Kaof plasma proteins in racehorses
Authors: STäMPFLI H. R. , MISIASZEK S. , LUMSDEN J. H. , CARLSON G. P. , HEIGENHAUSER G. J. F. 
Published: June 2010

SummaryThe plasma proteins are a significant contributor to the total weak acid concentration as a net anionic charge. Due to potential species difference, species‐specific values must be confirmed for the weak acid anionic concentrations of proteins (Atot) and the effective dissociation constant for plasma weak acids (Ka). We studied the net anion load Atotof equine plasma protein in 10 clinically healthy mature Standardbred horses. A multi‐step titration procedure, using a tonometer covering a titration range of PCO2from 25 to 145 mmHg at 37°C, was applied on the plasma of these 10 horses. Blood gases (pH, PCO2) and electrolytes required to calculate the strong ion difference ([SID] = [(Na++K++Ca2++Mg2+)‐(Cl−+Lac+PO42‐)]) were simultaneously measured over a physiological pH range from 6.90–7.55. A nonlinear regression iteration to determine Atotand Kawas performed using polygonal regression curve fitting applied to the electrical neutrality equation of the physico‐chemical system. The average anion‐load Atotfor plasma protein of 10 Standardbred horses was 14.89 ± 0.8 mEq/l plasma and Kawas 2.11 ± 0.50 × 10−7Eq/l (pKa= 6.67). The derived conversion factor (iterated Atotconcentration/average plasma protein concentration) for calculation of Atotin plasma is 0.21 mEq/g protein (protein‐unit: g/l). This value compares closely with the 0.24 mEq/g protein determined by titration of Van Slykeet al.(1928) and 0.22 mEq/g protein recently published by Constable (1997) for horse plasma. The Ka value compares closely with the value experimentally determined by Constable in 1997 (2.22 × 107Eq/l). Linear regression of a set of experimental data from 5 Thoroughbred horses on a treadmill exercise test, showed excellent correlation with the regression lines not different from identity for the calculated and measured variables pH, HCO3and SID. Knowledge of Atotand Kafor the horse is useful especially in exercise studies and in clinical conditions to quantify the mechanisms of the acid‐base disturbances occurring.
Effect of diet on Thoroughbred horses with recurrent exertional rhabdomyolysis performing a standardised exercise test
Authors: MacLEAY JENNIFER M. , VALBERG STEPHANIE J. , PAGAN J. D. , DE LA CORTE F. , ROBERTS JENNIFER , BILLSTROM JESSICA , McGINNITY JILL , KAESE HEATHER 
Published: June 2010

SummaryPrevious studies have associated recurrent exertional rhabdomyolysis (RER) with a diet high in soluble carbohydrate (CHO). The purpose of this study was to investigate the effect of 3 diets on clinical and metabolic parameters in 5 Thoroughbred horses with RER and 3 healthy Thoroughbreds performing a standardised exercise test (SET). Two diets were formulated to meet energy requirements for the amount of exercise being performed in the form of CHO or fat (21.4 Meal DE/day). The third diet was formulated to provide 135% of the DE of the other 2 diets in the form of an excessive amount of carbohydrate (28.8 Meal DE/day). Diets were fed in a crossover design for 3 week blocks and then horses performed a near maximal SET. Changes in heart rate (HR), plasma lactate, plasma glucose, total plasma solids, packed cell volume (PCV), muscle lactate and muscle glycogen concentration were measured immediately prior to, during, and 5 min after exercise. Serum creatine kinase (CK) activity was measured prior to and 4 h post SET. A 2‐way ANOVA was used to examine the effect of group and dietary treatment. When dietary treatments were compared, horses fed the high‐CHO diet had a mean pre‐SET PCV and pre‐SET HR that was higher than horses fed the fat diet (P=0.06 and P=0.07, respectively). Pre‐SET heart rates were highest in RER horses consuming the high‐CHO diet compared to RER horses consuming the low‐CHO and fat diets (P = 0.02). Horses with RER had 4 h post SET CK activity greater than 400 u/l in 7/14 (50%) measurements compared to control horses which had CK activity greater than 400 u/l in 2/7 (29%) measurements. This study did not demonstrate a significant effect of diet on rhabdomyolysis, indicated by CK activity, or on the metabolic response to exercise. However, diet may have a calming effect on Thoroughbred horses with RER as manifested by decreased pre‐exercise heart rates and decreased pre‐exercise PCV in horses fed the fat diet.
Dietary fat supplementation and equine plasma lipid metabolism
Authors: GEELEN SUZANNE N. J. , van OLDRUITENBORGH‐OOSTERBAAN MARIANNE M.SLOET , BEYNEN A. C. 
Published: June 2010

SummaryFeeding of a fat‐rich diet to horses may enhance the flux of fatty acids, in the form of triacylglycerols (TAG), through the circulation into skeletal muscle. This hypothesis was tested indirectly by measuring the concentration of plasma TAG and the activity of lipoprotein lipase (LPL) in post heparin plasma. Six mature horses were fed a high‐fat or a control diet according to a crossover design with feeding periods of 6 weeks. The control diet contained 1.5% fat in the dry matter and the high‐fat diet 11.8%. The high‐fat diet was formulated by adding soybean oil to the control diet at the expense of an isoenergetic amount of corn starch plus glucose. Both diets consisted of hay and concentrate and were given on a restricted basis. Nine hours after feeding, whole plasma TAG concentration decreased significantly by 84% following fat‐supplementation, whereas the whole plasma concentrations of cholesterol and phospholipids were significantly increased by 53% and 26%, respectively. The level of HDL‐cholesterol was raised by 54%. The changes in plasma lipids were accompanied by a 79% increase in LPL activity in post heparin plasma. These results indicate that in the fasting state a high‐fat diet raises the flux of fatty acids, in the form of TAG, into skeletal muscles as illustrated by the observed decrease in plasma TAG concentrations and increase in LPL activity. It is speculated that the increased flux of fatty acids is associated with an increased oxidative capacity of skeletal muscle which might be advantageous to exercising horses.
Time of feeding and fat supplementation affect plasma concentrations of insulin and metabolites during exercise
Authors: DUREN S. E. , PAGAN J. D. , HARRIS PAT A. , CRANDELL KATHLEEN G. 
Published: June 2010

SummarySix Thoroughbreds were used to evaluate time of feeding on changes in exercise response in horses receiving either a textured feed or a fat‐supplemented textured feed. Using a crossover design, 3 horses were fed a fat‐supplemented diet while 3 horses received a control ration of textured feed. Horses performed a standardised exercise test (SET) on a high speed treadmill. The SET was performed at 3 different times: 1) following an overnight 12 h fast, 2) 3 h after feeding and 3) 8 h after feeding. The SET consisted of a 2 min walk at 1.4 m/s, 800 m trot at 4.2 m/s, 800 m gallop at 7.7 m/s, 1600 m gallop at 11 m/s, 800 m trot at 4.2 m/s and 2 min walk at 1.4 m/s. Jugular blood samples were taken before feeding, hourly until the beginning of the SET, at the end of each exercise step, 15 min post exercise and 30 min post exercise. During the SET, heart rate was measured and blood samples collected for analysis of glucose, lactate, insulin and nonesterified fatty acids (NEFA). Feeding horses 3 h prior to exercise resulted in elevated concentrations of plasma glucose and insulin (P<.01) at rest Elevated concentrations of insulin in horses fed 3 h prior to exercise decreased plasma glucose (P<.01) during exercise and appeared to have suppressed fat oxidation during exercise because horses that were either fasted or fed 8 h post prandial had a net disappearance of NEFA in the plasma during exercise. This study indicates that beginning exercise with elevated plasma insulin appeared to be of no benefit during the exercise conducted in this experiment.
Digestible energy expenditure in grazing activity of growing horses
Authors: ASAI Y. , MATSUI A. , OSAWA T. , KAWAI M. , KONDO S. 
Published: June 2010

SummaryTen Thoroughbred yearlings (5 females and 5 males) were used to examine the effect of time of grazing on pasture forage and digestible energy (DE) intake, bodyweight gain and DE expenditure in grazing activity. Five females were grazed for 17 h/day (LTG), 5 males were grazed for 7 h/day (STG) and they were fed differently. As a result, DE intake from pasture forage of LTG horses and STG horses was 27.3 and 12.7–13.9 Meal/day, respectively. The average daily gain (ADG) of LTG and STG horses was 0.37 and 0.39–0.61 kg/day, respectively. The regression lines between DE intake and ADG of both groups were parallel and the difference in DE intake between them was 10 Meal of DE. It was suggested that DE expenditure in grazing activity (entirely at night) of growing horses was 1 Mcal/h under the conditions of this study.
Effect of a post exercise fat‐supplemented diet on muscle glycogen repletion
Authors: HYYPPä S. , SAASTAMOINEN M. , PÖSÖ A. REETA 
Published: June 2010

SummaryLow muscle glycogen at the beginning of exercise may adversely affect performance, increase protein degradation and contribute to the onset of fatigue. As horses are sometimes required to compete on consecutive days both in racing and endurance types of competition, optimal muscle glycogen repletion may improve performance on the day following a race day. The purpose of this experiment was to study the effects of fat supplementation on repletion of muscle glycogen. Twelve Finnhorses performed an exercise test on a treadmill, and 2 and 4 h later they received hay and concentrate(Trial A).Two weeks later these horses performed the same exercise test and were fed the same diet supplemented with either 1000 g of carbohydrate or 400 g of vegetable oil(Trial B).A third trial(Trial C)was 3 weeks later, identical to Trial B, except that the fat group had already been adapted to dietary fat for 3 weeks. Blood samples were analysed for lactate, glucose, glycerol, triglycerides, NEFA, cholesterol, β—OH‐butyrate, insulin and glucagon and muscle samples were analysed for glycogen and triglycerides. The results indicate that in horses not adapted to fat feeding, fat supplementation slows the rate of muscle glycogen repletion, and that after an adaptation period, fat supplementation does not alter the rate of muscle glycogen repletion compared to the rate with a normal diet.
The effect of dietary fibre on hydration status after dehydration with frusemide
Authors: WARREN LORI K. , LAWRENCE L. M. , BREWSTER‐BARNES TAMMY , POWELL DEBRA M. 
Published: June 2010

SummaryThree diets were fed to 6 horses in a 3 × 6 Latin rectangle experiment to determine if dietary fibre could improve hydration status in response to dehydration with frusemide. Frusemide was used to simulate dehydration from exercise‐induced sweat loss. Diets contained similar dry matter (DM), energy, protein and electrolyte content, but differed in total dietary fibre (TDF) and/or soluble fibre (SDF). The 3 diets were: 1) HIGH‐HIGH (high TDF, high SDF); 2) HIGH‐LOW (high TDF, low SDF); and 3) LOW‐LOW (low TDF, low SDF). In each 10 day period, water intake and faecal moisture content were assessed on Day 7. On Day 10, feed and water were withheld and horses were dehydrated with frusemide (1 mg/kg bwt, i.m.). Plasma volume (PV), plasma total protein (TP), packed cell volume (PCV) and plasma electrolyte concentrations were determined before and after frusemide administration. Water consumption was greater (P<.05) when horses received diets high in TDF. Faecal moisture content was greatest (P<.01) when horses received the HIGH‐HIGH diet. The decline in PV and the rise in plasma TP concentration following frusemide administration were similar for all diets. When horses received the HIGH‐HIGH diet, they had a greater (P<.05) bodyweight before dehydration and lost more (P<.05) bodyweight in response to frusemide. A greater loss of bodyweight in response to frusemide without a proportional loss of PV when horses received the HIGH‐HIGH diet suggests that a diet high in SDF may provide the horse with a source of dispensable water in the hind gut during dehydration.
Repeated administration of frusemide does not offer an advantage over single dosing in attenuating exercise‐induced pulmonary hypertension in Thoroughbred horses
Authors: GOETZ T. E. , MANOHAR M. , MAGID J. H. 
Published: June 2010

SummaryThe objective of the present study was to ascertain whether administration of a second dose of frusemide would attenuate exercise‐induced pulmonary hypertension more than a single dose. Right atrial, right ventricular and pulmonary vascular pressures were determined in 7 healthy, sound, exercise‐trained Thoroughbred horses at rest and during exercise (14.2 m/s + a 3.5% uphill grade) performed at maximal heart rate (217 ± 3 beats/min [mean ± s.e.]). Horses were studied during the following 3 treatments in random order 7 days apart: control (no medication), frusemide single dose (250 mg i.v. 4 h pre‐exercise), and frusemide double dose (250 mg i.v., 4 h pre‐exercise + 250 mg i.v. 2 h pre‐exercise). In the control study, exercise resulted in significant (P<.05) right atrial as well as pulmonary arterial, capillary and venous hypertension. In the frusemide single dose experiments, a significant (P<.05) attenuation of the exercise‐induced rise in right atrial and pulmonary vascular pressures was observed. However, compared with frusemide single dose experiments, significant changes in the exercise‐induced right atrial and pulmonary arterial, capillary and venous hypertension were not observed in the frusemide double dose experiments. Therefore, it is concluded that administration of an additional dose of frusemide is unlikely to affect the severity of EIPH in racing Thoroughbred horses more than a single dose.
Osteoinductive response in the dorsal aspect of the carpus of young Thoroughbreds in training occurs within months
Authors: FIRTH E. C. , GOODSHIP A. E. , DELAHUNT J. , SMITH T. 
Published: June 2010

SummaryBone mineral density (BMD) was measured by dual x‐ray absorptiometry (DXA) in the carpus of 6 Thoroughbreds age 24 months that were exercised on the treadmill for 4.5 months, and of 6 matched control horses. A sagittal slab of known thickness was sawn from one or more of radius, radial carpal (Cr), third carpal (C3), and third metacarpal (Mc3) bones. After the 4.5 month treadmill exercise, there was a significantly greater volumetric BMD in the dorsal aspect of C3 (P=0.006). Treadmill‐exercised horses also had higher BMD in the dorsodistal aspect of the radius (P=0.03), the dorsal half of Mc3 (P=0.012), and the dorsal aspect of Cr (P = 0.04). In other areas of interest (AOI) studied on the palmar aspect of the bones, significant increases in exercised horses did not occur. These sizeable changes in bone mass occurred within a few months of initiation of exercise. With technical development, DXA could be appliedin vivofor investigation of changes in bone mass of horses which are growing and exercising under various regimes. The data are also relevant to the development of scientifically based training protocols.