bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of ambient temperature and humidity on pulmonary artery temperature of exercising horses
Authors: KOHN CATHERINE W. , HINCHCLIFF K. W. , McKEEVER K. H.
Published: June 2010

Six healthy Thoroughbred mares were trained to run on a high‐speed treadmill and were conditioned for approximately 5 weeks. Each horse performed 6 identical standardised exercise tests (SET) 5 to 7 days apart Each SET was performed under different ambient laboratory conditions: low temperature/low humidity (LL) 20.2° ± 0.6°C, 53.6 ± 4.1%; low temperature/high humidity (LH) 19.7 ± 0.6°C, 86.7 ± 4.2%; medium temperature/low humidity (ML) 24.6 ± 0.2°C, 58.7 ± 3.7%; medium temperature/high humidity (MH) 24.7 ± 0.3°C, 87.5 ± 1.4%; high temperature/low humidity (HL) 31.1 ±0.6°C, 41.6 ± 3.5%; and high temperature/high humidity (HH) 30.6 ± 0.2°C, 84.4 ± 3.6%. Horses completed the 46 min SET, became fatigued or exercise was terminated when a pulmonary artery temperature (PAT) of 41.5°C was reached. During a 30 min recovery period, horses stood quietly on the treadmill. Only one trial was terminated due to fatigue; in all other trials horses completed the 46 min SET or the trial was terminated when PAT=41.5°C. The relationships among run time (min) or PAT (°C), ambient temperature and % relative humidity were defined by multiple linear regression analysis. Run time (min) = 90.9 — (1.39 × ambient temperature °C) — (0.236 × relative humidity %). Approximately 54% of the variation in run times was explained by variation in environmental conditions, indicating that ambient temperature and humidity contribute substantially to the rate of rise in PAT. Run times to a PAT of 41.5°C were significantly shorter (P<.000001) in HH than in other groups during the SET. Approximately 63% of the variation in PAT at the end of exercise was due to ambient temperature and humidity. In general, the longer the exercise time, the better the correlation among PAT, ambient temperature and relative humidity. Rectal temperature increased significantly (P<.0001) during the recovery period only in horses in the HH group, indicating that heat dissipation during recovery may have been impaired by environmental conditions. This study demonstrates that hot humid conditions result in more rapid rate of rise in PAT for horses undertaking identical exercise tests.
Effect of frusemide and hypertonic saline on electrolytes during post exercise anaesthesia
Authors: GREENE S. , KEEGAN R. , BROWN JENNIFER , KINGSTON JANENE , BAYLY W. M.
Published: June 2010

This study evaluated the effects of pre‐exercise frusemide administration and hypertonic saline (H) infusion during anaesthesia on arterial pH, blood gases and electrolytes in 6 Thoroughbred horses anaesthetised immediately post exercise. Horses received either frusemide (F) (0.5 mg/kg, i.v.) or a saline placebo (P) injection 4 h prior to treadmill exercise. Exercise consisted of a 3 min warm‐up at 40% V̇O2maxfollowed by exercise to fatigue. Detomidine (40 μg/kg, i.v.) was given within 5 min of stopping and followed 5 min later by zolazepam‐tiletamine (1.25 mg/kg, i.v.) to induce anaesthesia. During maintenance of anaesthesia using isoflurane in O2. either isotonic saline solution (I) or 7.5% H (4 ml/kg, i.v.) was administered. Arterial blood was sampled at the following times: prior to (Pre‐F/P) and 4 h after (Pre‐ex) F or P administration, 1 min after fatigue (Fatigue), 5 min after induction of anaesthesia (Post‐ind), and just prior to and 15, 30 and 60 min after beginning isoflurane (ISFL) anaesthesia. Arterial pH and blood gas tensions, pulmonary arterial blood temperature, plasma [lactate], total protein and plasma [Na+], [K+], and [Cl−] were measured. Data were analysed using 2‐way ANOVA for repeated measures (P<.05). There were significant differences over time for all variables except total protein. Plasma [Na+] increased at Fatigue compared to Pre‐F/P or Pre‐ex in all treatment groups. Plasma [Na+] and [Cl−] increased during ISFL anaesthesia compared to Pre‐F/P and Pre‐ex in horses given H. During ISFL anaesthesia, plasma [Cl−] decreased compared to Pre‐F/P in Group F+I horses. We conclude that acid‐base, blood gas, and electrolyte changes associated with F are unlikely to influence management of horses anaesthetised immediately following supramaximal exercise to fatigue. Hypertonic saline infusion may help restore plasma [Cl−] faster in hypochloremic horses requiring anaesthesia immediately after strenuous exercise.
The effects of timing and amount of forage and grain on exercise response in Thoroughbred horses
Authors: PAGAN J. D. , HARRIS PAT A.
Published: June 2010

There is considerable debate among horsemen about how to feed horses before exercise. Should horses be fed or fasted before work and when should hay be fed relative to grain and/or exercise? Three experiments were conducted to evaluate if feeding hay with and without grain affects glycaemic and haematological responses in Thoroughbred (TB) horses at rest and during a simulated competition exercise test (CET) on a high‐speed treadmill. InExperiment 1, 6 TB horses were fed hay at 3 different times relative to a grain meal. Time of feeding hay affected glycaemic response, plasma protein and water intake post grain feeding. DuringExperiment 2, 4 TB horses were used in a 4 × 4 Latin square design to determine whether feeding grain with or without hay prior to a CET would affect substrate utilisation and exercise. Feeding grain reduced free fatty acid (FFA) availability and increased blood glucose disappearance during exercise (P<.05). Feeding hay either along with grain orad libitumthe night before exercise resulted in reduced plasma volume (P<.05) and higher lactate production (P<.05) and heart rates (P<.05) during exercise. DuringExperiment 3, 4 TB horses were used in a 4 × 4 Latin square design experiment to determine whether feeding forage but no grain prior to CET would affect substrate utilisation and performance. Feeding only forage before exercise did not adversely affect performance. It was concluded that grain should be withheld from horses before exercise, but that small quantities of hay should be fed to ensure proper gastrointestinal tract function.
Dietary protein influences acid‐base responses to repeated sprints
Authors: GRAHAM‐THIERS PATRICIA M. , KRONFELD D. S. , KLINE K. A.
Published: June 2010

Dietary protein during conditioning and exercise must support additional needs while avoiding adverse metabolic effects. Ten Arabian horses were assigned randomly to 2 diets formulated to contain 7.5 or 14.5% crude protein and 12% fat. The low‐protein diet (LP) was supplemented with lysine and threonine to match the levels of these amino acids in the high‐protein diet (HP). Feed intake averaged 8.1 kg/day. Dietary cation‐anion difference was 181.6 and 260.4 mmol/kg for high and low protein, respectively. Following 9 weeks conditioning, horses performed a repeated sprint test: 3 min walk at 1.5 m/s and zero slope, followed by 3 min walk at 1.5 m/s, 5 min trot at 3.5 m/s, then six 1 min sprints at 10 m/s separated by 4 min walks all on a 6% slope, concluding with 30 min walk at 1.5 m/s and zero slope. Blood samples (arterial, A, and venous, V) were taken at rest, during the last 15 s of each sprint, and at 5, 10, 20 and 30 min. of recovery. Samples were analysed for total protein (TP), lactate (La−), pH, PCO2, PO2, HCO3−, Na+, K+ and Cl−. Strong ion difference (SID+) and total weak acids (Atot) were calculated. Analysis of variance with repeated measures was used to evaluate the effects of exercise and recovery (time), diet and any interactions.

Comparing LP to HP groups, plasma pH tended to be higher after the first sprint (V, P=0.084; A, P = 0.014), and plasma HCO3− was higher overall (V, P=0.0023; A, P = 0.094) during exercise and recovery. In both groups, pH declined; however, LP remained higher than HP. The decline in pH represents an exercise‐induced acidosis which was attributable mainly to PCO2, especially during recovery, and to a tendency for a higher SID+ during most of exercise and recovery. The plasma La− response was lower, Cl− higher, suggesting that LP enhanced the lactate‐storage function of erythrocytes. Dietary protein restriction for 9 weeks moderated sprint‐induced acidosis in fat‐adapted horses.
A comparison of grain, oil and beet pulp as energy sources for the exercised horse
Authors: CRANDELL KATHLEEN G. , PAGAN J. D. , HARRIS PAT , DUREN S. E.
Published: June 2010

High‐grain diets for the exercising horse were compared with diets which provided 15% of the total caloric intake from either vegetable oil or a highly fermentable fibre source (beet pulp). Six Thoroughbreds age 3 years were fed one of 3 diets for 5 weeks in a replicated 3 × 3 Latin square. The CONTROL diet was 3.65 kg of sweet feed (SF), 0.9 kg of a protein/vitamin/mineral pellet and 5.45 kg of hay cubes. The FAT diet replaced 1.15 kg of SF with 0.45 kg of soybean oil and the FIBRE diet replaced 1.15 kg of SF with 1.36 kg of beet pulp. Horses were exercised 3 times per week on a highspeed treadmill. During the last week of each period, the horses performed a standardised exercise test (SET). A series of blood samples was drawn immediately before feeding and every 0.5 h for 3 h after feeding, throughout the exercise bout and 30 min post exercise. Plasma was analysed for lactate, glucose, cortisol, insulin, packed cell volume, total protein and triglycerides. Water intake was measured at regular intervals during SET day.

Blood glucose was lower (P<.05) in the FAT‐fed horses during the 3 h post feeding as compared to either CONTROL or FIBRE‐fed horses. Insulin was lower (P<.05) in the FAT‐fed both post feeding and throughout exercise. Cortisol was lower (P<.05) in the FAT than the CONTROL‐fed during exercise. Following exercise, the FAT‐fed drank more water (P<.1) than either CONTROL or FIBRE‐fed. Substituting 15% of DE as vegetable oil had a greater effect on metabolic response to exercise than a 15% substitution of beet pulp.
Influence of oral ß‐alanine and L‐histidine supplementation on the carnosine content of the gluteus medius
Authors: DUNNETT M. , HARRIS R. C.
Published: June 2010

The aim of this work was to test the hypothesis that in vivo carnosine biosynthesis is dependent upon endogenous ß‐alanine availability, by studying the effect of sustained dietary ß‐alanine supplementation in the horse on the carnosine concentration in types I, IIA and IIB skeletal muscle fibres. The diets of 6 Thoroughbred horses were supplemented 3 times/day with ß‐alanine (100 mg/kg bwt) and L‐histidine (12.5 mg/kg bwt) for a period of 30 days. Percutaneous biopsies of the m. gluteus medius from a depth of 6 cm were taken on the days immediately before and after the supplementation period. Heparinised blood samples were collected at hourly intervals on the first and last days of supplementation, and on every sixth day during the supplementation period, 2 h after each ration. Individual muscle fibres were dissected from freeze‐dried biopsies, weighed and characterised histochemically. ß‐alanine, histidine and carnosine concentrations were measured in plasma. The areas under the plasma concentration‐time curves (AUC) for ß‐alanine and histidine were calculated as indicators of the doses absorbed. Carnosine concentrations were measured in types I, IIA and IIB muscle fibres.

There was an adaptive response to sustained ß‐alanine administration resulting in mean ± s.d. ß‐alanine AUC increasing significantly from 1130 ± 612 umol/l h (Day 1) to 2490 ± 1416 μmol/l h (Day 30) (P< 0.05). This was probably due to increased ß‐amino acid transport across the gastrointestinal lumen. There was no consistent increase in histidine AUC between Days 1 and 30, (mean ± s.d. values being 757 ± 447 umol/l h [Day 1] and 1162 ± 1084 umol/l h [Day 30] [P< 0.05]). Type IIA fibre carnosine concentrations increased from 59.9–102.6 to 76.2–112.2 mmol/kg dry weight (dw). Increases were statistically significant in 2 of the 6 horses (P<.05 in both instances). Type IIB fibre carnosine concentrations increased from 1013–131.2 to 1143–153.3 mmol/kg dw. Increases were statistically significant in 5 of the 6 horses (P<.05 in 3 horses, P<.01 in 1 horse, P<.005 in 1 horse). Changes in muscle carnosine concentration appeared to be influenced by ß‐alanine bioavailability. Individual increases in muscle carnosine concentration were significantly correlated with individual changes in ß‐alanine AUC (r2 = 0.973, P<.005). Increased muscle carnosine concentrations lead to increased intramuscular hydrogen ion (H+) buffering capacity.
Plasma adrenocorticotropin, cortisol and catecholamines response to various exercises
Authors: NAGATA S. , TAKEDA F. , KUROSAWA M. , MIMA K. , HIRAGA A. , KAI M. , TAYA K.
Published: June 2010

The responses of plasma adrenocorticotropin (ACTH), cortisol, noradrenaline and adrenaline in 5 Thoroughbred horses to an incremental exercise and 2 relative workload exercises, at 105 and 80% maximal oxygen consumption (V̇O2max), on a treadmill were examined. These hormone concentrations increased (P<.05) with each exercise and the maximal plasma concentrations of ACTH, cortisol were observed between 5 and 30 min after the end of the exercise, while maximal catecholamine concentrations occurred just at exhaustion time. The plasma ACTH, noradrenaline and adrenaline responses during exercise were more sensitive to the intensity of exercise than that of cortisol and showed a significant correlation with blood lactate concentrations (r=0.605, P<.001 for ACTH; r=0.718, P<.001 for noradrenaline; r=0.738, P<.001 for adrenaline). The plasma cortisol response appeared to be connected with the duration of exercise (r=0.71, P<.05). The recovery of these hormones was related to the exercise styles. These results suggest that the autonomic nervous system and the pituitary‐adrenal axis of the horse are efficiently stimulated by various treadmill exercises, and these hormones may be used in the evaluation of exercise‐induced stress.
Maximal exercise transiently disrupts hormonal secretory patterns in Standardbred geldings
Authors: GOLLAND LORRAINE C. , EVANS D. L. , STONE G. M. , TYLER‐McGOWAN CATHERINE M. , HODGSON D. R. , ROSE R. J.
Published: June 2010

Basal concentrations of cortisol (CORT), beta‐endorphin (ßEP), growth hormone (GH) and testosterone (T) and their disruption during 32 h of recovery after treadmill exercise were investigated in 4 geldings. Blood samples were collected from resting horses every 20 min between 0600–1000 and 1500–1900 h, and hourly between 1000–1500 h on 3 consecutive days. Treadmill exercise tests comprising 2 min intervals at 30, 50, and 70% V̇O2max then to fatigue at 100% V̇O2max were conducted between 1020–1130 h on Day 2. Blood was collected before, during and 15, 30, 60 and 90 min after exercise. Mean (Cav), peak (Cmax) and total (i.e. integrated) (Ctot) concentrations were calculated for CORT, βEP and GH during the 20 min sampling sessions, and for CORT, βEP, GH and T between 1000–1300 h on Days 1–3 (incorporating the samples during exercise on Day 2) and 1300–1900 h on Days 1–3. Cav, Cmax and Ctot for CORT, βEP, GH and T were greater during exercise and recovery than in the same period on Day 1. Cav and Ctot values for plasma T during the 1300–1900 h period were significantly elevated on Day 2 and compared to Day 1 (P<.05), but there were no differences between Days 1 and 3 values for these variables. We concluded that plasma T concentration increases in response to maximal exercise in geldings, as does plasma CORT, βEP and GH. Furthermore, maximal exercise disrupts basal plasma concentrations of CORT, βEP and GH for up to 24 h and T for 26–32 h post exercise in geldings, therefore reflecting the minimum recovery periods required before evaluating normal, resting levels of these hormones in horses undergoing training.
Relationship of body condition score to completion rate during 160 km endurance races
Authors: GARLINGHOUSE SUSAN E. , BURRILL MELINDA J.
Published: June 2010

Three‐hundred and sixty horses, primarily of Arabian breeding, age 5–22 years and body condition scores 1.5–5.5 (on 1 to 9 scale as described by Henneke 1985), participated in one of two 160 km endurance races over the same course in August 1995 and July 1996. Condition score, cannon bone circumference, combined rider and tack weight, heart girth and body length were measured 11–18 h prior to the start of the event and bodyweight estimated according to the formula by Carroll and Huntington (1988). A rider weight ratio was calculated as rider weight divided by horse bodyweight. Rider weight and rider weight ratio had no effect on overall completion rates among all horses (P>0.05). Among horses successfully completing the course, rider weight and rider weight ratio had no effect on finish time or placing (P>0.05). Among horses who were eliminated, rider weight and rider weight ratio had no effect on miles completed before failure (P>0.05). Condition scores had a significant effect on completion rate (P<.001). Distance successfully completed increased 31.81 km (19.88 miles) for each incremental increase of 1 in condition score (P<.001). Within the group of unsuccessful horses, there was a significant difference in condition score between horses who failed due to metabolic and nonmetabolic factors (P<.001). It was concluded that condition score is a more important factor in endurance performance than has been previously believed, and that condition score is a more important factor than is the weight of the rider, or the rider weight in relation to the weight of the mount.
Effects on exercise metabolism of varying dietary starch and sugar proportions
Authors: JANSSON A. , NYMAN S. , LINDHOLM A. , LINDBERG J. E.
Published: June 2010

Studies of the effect of varying dietary carbohydrate compositions on exercise metabolism of horses are scarce. In the present study, the starch and sugar porportions were altered in the diet to 4 Standardbred horses. In a crossover experiment, the horses were offered a hay and oat diet, where the oats were substituted for barley syrup (BS) at 4 levels (BS 0, 0.5, 1.0 and 1.5 kg). Each diet was consumed for 21 days and both an incremental treadmill exercise test (IE) and a 40 min submaximal exercise test (SE) were performed. During the IE there was a significant (P<0.05) increase in mean V̇O2 on BS 1.5 and at the highest speed respiratory exchange ratio (RER) was significantly lower on BS 1.0 and 1.5. During the SE, RER and HR were significantly higher on BS 1.0 and 1.5. There were no significant effects of diets on plasma levels of glucose, lactate and insulin. Following the SE there was a significant decrease in the muscle glycogen content on BS 0, which was not observed in the other diets. In addition, there was a numerical decrease in the glycogen utilisation with increasing proportions of sugar in the diet. In conclusion, this study indicates that horses on diets with a high sugar inclusion respond with an increased heart rate during exercise of lower intensities; and that the response in V̇O2 and RER may differ depending on the exercise intensity. In addition, glycogen utilisation during submaximal exercise was lowered when daily sugar intake was increased. However, further investigation is needed to evaluate whether this strategy of feeding could be beneficial for exercising horses competing over endurance distances.
Effect of feeding exercised horses on high‐starch or high‐fat diets for 390 days
Authors: ZEYNER A. , BESSERT J. , GROPP J. M.
Published: June 2010

Our hypothesis was that, because horses have not evolved as fat eaters, there may be negative metabolic long‐term effects of feeding a high fat diet. The objective of the present study was to identify these long‐term effects and compare them with the effects of isoenergetic long‐term high starch feeding. This randomised block study with 20 exercised horses looked at the effect of feeding either a high starch (HS) or a high fat (HF) diet type in 3 periods during stabling (Stable 1), pasture, and stabling (Stable 2) over 390 days. The horses received a HS or HF concentrate, straw, hay and 6 h pasture/day in the pasture period. HF horses gained weight (2% of initial bwt) and, therefore, fat intake was reduced (from 1.43 to 0.88 g/kg bwt/day). Blood plasma glucose, total protein, albumins, γ‐globulins, free fatty acids, phospholipids and cholesterol concentrations were higher but urea concentration was lower with HF compared to HS feeding (P<0.05). Plasma concentrations of triglycerides, bilirubin and pre‐β lipoproteins were unaffected by the diet type. There were period effects (P<0.05) for all variables except triglycerides and pre‐β lipoproteins. In contrast to HS, in HF the quotient α/β lipoproteins rose (P<0.05) throughout the stable periods and decreased (P<0.05) during ‘pasture’. Glutamic acid dehydrogenase, γ‐glutamyl transferase, alkaline phosphatase, aspartate aminotransferase, creatine kinase and lactate dehydrogenase activity in sera were within the normal range.

In conclusion, on the precondition that substantial bodyweight changes were prevented, no apparent adverse effects of long‐term high fat feeding were identified and there were no apparent disadvantages of feeding on high fat compared with high starch diets.
Effect of short‐term exercise training on insulin sensitivity in obese and lean mares
Authors: POWELL D. M. , REEDY S. E. , SESSIONS D. R. , FITZGERALD B. P.
Published: June 2010

Twelve untrained aged mares were used to determine whether 7 days of light exercise improved peripheral tissue insulin sensitivity. Mares were divided into obese‐exercised (n = 3), obese‐sedentary (n = 3), lean‐exercised (n = 3) and lean‐sedentary (n = 3) groups. The exercised groups were worked at a trot to a heart rate (HR) of not more than 140 beats/min for 30 min in a round pen. Each group was subjected to 3 euglycaemic hyperinsulinaemic clamps: prior to exercise (P), 24 h following the seventh exercise training session (E) and 9 days postexercise training (PE). Prior to exercise training, the mares in the obese group were confirmed insulin‐resistant compared to the mares in the lean group. There was no change in bodyweight or body condition in the obese or lean groups throughout the study. Glucose infusion rate (GIR) was higher (P<0.05) on E compared to P days in the obese‐exercised and lean‐exercised groups. Insulin sensitivity returned to pre‐exercise values by 9 days postexercise in the obese‐exercised and lean‐exercised groups. The results of this study suggest that improvement in insulin sensitivity occurs in obese mares without a long interval of exercise training and in the absence of a change in bodyweight.
Effects of substituting starch with fat on the acid‐base and mineral status of female horses
Authors: ZEYNER A. , KIRBACH H. , FÜRLL M.
Published: June 2010

Feeding a high‐fat diet may have potential advantages by maintaining pH homeostasis during intense exercise; conversely, effects including elevated PCV and increased plasma concentration of total protein may indicate effects detrimental to performance by reducing perfusion of tissues and organs. Six horses were used to determine the effects of an replacement of starch (diet ‘0.00’) with 0.33, 0.67, 1.00 and 1.33 g soybean oil/kg bwt/day (diets ‘0.33’, ‘0.67’, ‘1.00’ and ‘1.33’) on venous and renal acid‐base status and fractional clearance (FC) of electrolytes in a postprandial state but prior to exercise. Venous blood and urine were sampled for 3 days at the end of the 28 day periods, in each case 3 h postprandially. Throughout the study, the horses put on weight by 35 kg (P<0.05). From diet ‘0.00’ to ‘0.67’, blood pH decreased (P<0.05) and carbon dioxide tension increased (P<0.05). Simultaneously, the base and net acid‐base concentration in the urine rose (P<0.05) but diuresis decreased (P<0.05) and, therefore, the daily excretion of bases and net acid‐bases was only unsystematically affected. From diet ‘0.00’ to ‘1.33’, the FC of magnesium and chloride fell (P<0.05). These results suggested that the exchange of starch with up to moderate amounts of fat affects the venous and renal acid‐base status of resting horses. The decrease in urine volume is most striking. Further research is needed to investigate the importance of these effects for sporting performance.
Effects of ageing and training on maximal heart rate and V̇O2max
Authors: BETROS C. L. , MCKEEVER K. H. , KEARNS C. F. , MALINOWSKI K.
Published: June 2010

The purpose of this study was to test the hypotheses that ageing would result in a decline in maximal heart rate (HRmax) and maximal aerobic capacity (V̇O2max) and, secondarily, that those effects would be reversible with training. Eighteen, healthy, unfit Standardbred mares representing 3 age groups: young (Y = mean ± s.e. 6.8 ± 0.4 years, n = 6); middle‐aged (MA = 15.2 ± 0.4 years, n = 6); and old (O = 27.0 ± 0.2 years, n = 6) were used. HRmax, V̇O2maxand oxygen pulse at V̇O2max(OPmax) and the velocities producing HRmax(V̇HRmax) and V̇O2max(VV̇O2max) were measured during pretraining and post‐training incremental exercise tests (GXT). During training, mares exercised 3 days/week (Weeks 1–8) and 4 days/week (Weeks 9–12) at a submaximal intensity (∼60% HRmax) for ∼30 min/day. There were no differences (P>0.05) between Y and MA, before (218 ± 2 vs. 213 ± 3 beats/min; 116 ± 3 vs. 109 ± 3 ml/kg bwt/min; 0.55 ± 0.01 vs. 0.52 ± 0.02 ml/kg/beat; 9.0 ± 0.3 vs. 9.3 ± 0.2 m/s; 8.8 ± 0.2 vs. 8.8 ± 0.2 m/s) or after training (224 ± 2 vs. 218 ± 2 beats/min; 131 ± 3 vs. 120 ± 2 ml/kg bwt/min; 0.58 ± 0.01 vs. 0.55 ± 0.01 ml/kg/beat; 10.5 ± 0.2 vs. 9.5 ± 0.1 m/s; 10.6 ± 0.2 vs. 9.5 ± 0.1 m/s) for HRmax, V̇O2max, OPmax, V̇HRmaxor VV̇O2max, respectively. Old horses had lower HRmax, V̇O2maxand OPmaxand reached them at lower velocities compared to Y and MA (P<0.05), both before (193 ± 3 beats/min; 83.2 ± 2.0 ml/kg bwt/min; 0.43 ± 0.01 ml/kg/beat; 7.8 ± 0.1 m/s; 7.2 ± 0.1 m/s) and after training (198 ± 2 beats/min; 95 ± 2 ml/kg bwt/min; 0.48 ± 0.01 ml/kg/beat; 8.2 ± 0.2 m/s; 8.0 ± 0.2 m/s). Training did not alter HRmaxin any age group (P>0.05) but did cause increases in V̇O2max, OPmaxand VV̇O2maxfor all groups (P<0.05). Interestingly, training increased VHRmaxonly in Y (P<0.05). These data demonstrate that there is a reduction in HRmax, V̇O2max, OPmax, VHRmaxand VV̇O2maxin old horses, and that training can partially reverse some effects of ageing.
Heart rate and blood lactate responses during exercise in preparation for eventing competition
Authors: SERRANO M. G. , EVANS D. L. , HODGSON J. L.
Published: June 2010

The aim of this study was to investigate the heart rate and blood lactate responses to exercise in event horses in normal training, and to compare them to those encountered in eventing competition. It was hypothesised that the responses during exercise in the course of training for CCI*** events would be significantly different from those of the Cross‐Country day. Heart rates and blood lactate concentrations were measured in 13 elite event horses after intense exercise sessions conducted during the late stages of preparation for CCI*** or CCI**** 3‐day‐event competition. Mean ± s.d. heart rate during exercise was 138 ± 17 beats/min and mean blood lactate concentration after exercise was 1.0 ± 0.6 mmol/l. These values were compared to heart rates and blood lactate concentrations recorded during and after a CCI*** Cross Country course using unpairedttests (unequal variances) and 99.9% confidence interval analysis. Mean heart rates during and blood lactate concentrations after the competition were 195 ± 8 beats/min and 10.2 ± 4.2 mmol/l. The 99.9% confidence intervals were 183–207 beats/min and 7.7–12.6 mmol/l. Heart rates and blood lactate concentrations recorded during exercise sessions were significantly lower than competition values (P<0.001) and lay outside 99.9% confidence intervals for most horses. Only one horse achieved heart rates and blood lactate concentrations during exercise sessions that were similar to those occurring in competition. The intensity of exercise during normal training sessions was much lower than during competition, suggesting that many event horses are not appropriately trained.
Ribose supplementation in maximally exercising Thoroughbreds
Authors: KAVAZIS A. N. , SOBOTA J. S. , KIVIPELTO J. , PORTER M. B. , COLAHAN P. T. , OTT E. A.
Published: June 2010

A diverse group of studies, which are equine exclusive, indicate that ribose administered to myocardial and skeletal muscle tissue stimulates ATP production and recovery. This study investigated the effects of ribose supplementation on blood and muscle metabolites and performance in Thoroughbred geldings performing a maximal treadmill standardised exercise test (SET). In Experiment 1, 6 conditioned Thoroughbred geldings performed a baseline SET and horses were assigned to one of 2 experimental treatment groups, placebo or ribose, based on Vo2max. The placebo treatment group received 0.07 g glucose/kg bodyweight (bwt) and ribose treatment group received 0.07 g ribose/kg bwt top dressed on the feed twice daily. Following a 2 week treatment period, a second SET was performed. After a one‐week washout period, the horses switched treatment groups. Following another 2 week treatment period, a third SET was performed. Blood ammonia‐N was lower in the ribose treatment group at 15 min (P = 0.06) and 30 min (P = 0.02) postexercise. Plasma lactic acid was lower in the ribose treatment group at 30 min postexercise (P = 0.07). In Experiment 2, 1 h before a SET, 2 horses received 31 water (control) and 3 horses 250 g of ribose dissolved in 31 water (single ribose dose) via a nasogastric tube. Following a 2 week washout period, the horses switched treatment groups and another SET was performed. There were no differences in blood ammonia‐N, plasma lactic acid or glucose between treatment groups. No differences in performance were detected between treatment groups in either experiment. In conclusion, the results from Experiment 1 show a trend that daily ribose supplementation may be beneficial during recovery from exercise. However, a single dose of ribose 1 h before exercise revealed no effect on the variables measured. Because moderate to intense daily exercise can cause a decrease in total adenine nucleotide (TAN) pool with no meaningful recovery even after 72 h rest, future experiments should be designed to futher elucidate the effects of ribose supplementation on TAN metabolism in horses exercising at high intensity.
Induction of heat shock protein 72 mRNA in skeletal muscle by exercise and training
Authors: PÖSÖ A. R. , EKLUND‐UUSITALO S. , HYYPPÄ S. , PIRILÄ E.
Published: June 2010

In response to stress, cells synthesise heat shock proteins (HSP) to maintain protein homeostasis. To study whether exercise and training induce expression of HSP72 in the middle gluteal muscle, 10 Finnhorses performed a submaximal 60 min exercise test on a treadmill. Test A was performed after 3 months of training, and the other two tests 2 (B) and 5 (C) weeks later. Blood samples were taken during and after the tests, and biopsy samples before, immediately after and 23 h after each test. HSP72 mRNA was analysed using a digoxigenin‐labelled probe. Blood lactate concentration in the 3 tests varied between 7.2 and 10.2 mmol/I. Training increased HSP72 mRNA, as indicated by increases in samples taken at rest (A<B<C). Exercise also tended to increase HSP72 mRNA transiently but, 23 h later, values had returned to pre‐exercise levels. HSP72 mRNA was expressed in all muscle fibres. After exercise, HSP72 mRNA correlated positively with the peak concentration of blood lactate, but not with indicators of energy status. Therefore, acidosis rather than energy depletion was the major inducer of HSP72 expression after moderate intensity exercise. Because HSP72 may protect cells against stress, knowledge about their expression may help in planning optimal trainng regimes.
Influence of trotting and supplemental weight on metacarpal bone development
Authors: NIELSEN B. D. , O'CONNOR C. I. , ROSENSTEIN D. S. , SCHOTT H. C. , CLAYTON H. M.
Published: June 2010

The use of weight‐training to alter bone strength has not been investigated in horses. Recognising that bone responds to loading, we studied the effect of carrying weight on bone development during training. Seventeen horses were divided into 3 groups: controls exercised counterclockwise in a free‐flow exerciser; the weight group performed the same exercise carrying progressively increasing weight up to 45 kg and the weight supplement group also received a myo‐anabolic supplement. Radiographic equivalence measure of bone mineral content of zones of the third metacarpi (MCIII) was determined on 4 occasions: baseline (Day 108), pre‐conditioning following 108 days stall confinement (Day 0), mid‐conditioning (Day 39) and end‐conditioning (Day 78). Stall confinement resulted in loss of mineral in lateral and medial cortices of both MCIII. During conditioning, weight‐carrying increased mineral deposition in lateral and medial cortices of MCIII of the left (inside) leg compared with controls. In the right leg, controls had lower mineral content of the lateral cortex at Day 39 than weight‐carrying horses but no differences between treatments were recorded at Day 78. Markers of bone metabolism did not change from baseline to pre‐conditioning, but increased from Day 0 to 39 and 78 for all groups. This study demonstrates the benefits to bone mineral deposition in the third metacarpi of carrying weight when trained at low speeds and re‐emphasises the potential for bone loss when not given sufficient exercise.
Do regional variations in flexor tendons predispose to site‐specific injuries?
Authors: BIRCH H. L. , SMITH T. J. , POULTON C. , PEIFFER D. , GOODSHIP A. E.
Published: June 2010

Partial rupture occurs most often to the superficial digital flexor tendon (SDFT) of the forelimb at the mid‐metacarpal level. In this study, we tested the hypothesis that the mid‐metacarpal region of the SDFT has the smallest cross sectional area (CSA) and a similar collagen content to other regions and, therefore, represents a weak point in the tendon. The SDFT was collected from the forelimbs of 9 horses. Each tendon was marked at 7 different levels from the origin of the accessory ligament to the phalangeal region. The CSA, water content and collagen content was measured at each level.

The mid‐metacarpal level had a significantly smaller CSA than the most proximal and distal levels measured and a significantly higher dry matter content than proximal levels. However, the total amount of collagen present in the mid‐metacarpal section was not significantly less than other regions except for the most distal sections. The results of this study suggest that the mid‐metacarpal region of the SDFT, although smaller in CSA, is not significantly weaker than the proximal end andmanica flexoriaregion of the tendon. Therefore, other factors such as hypoxia and/or hyperthermia may be responsible for site‐specific tendon lesions in the SDFT.
Three‐dimensional kinematics of the tarsal joint at the trot
Authors: LANOVAZ J. L. , KHUMSAP S. , CLAYTON H. M. , STICK J. A. , BROWN J.
Published: June 2010

The tarsal joint is a common site of injury for many sport horses. Understanding the biomechanics of this complex joint begins with developing a clear picture of the kinematics during normal locomotion. This study describes the 3D kinematics of the tarsal joint by measuring the motion of the tibia and third metatarsus in 4 sound Quarter Horses with targets attached directly to the bones via steel pins. The objective was to determine if the tarsus had significant motion outside the tarsocrural joint. Two Steinmann pins were inserted into the lateral side of the right hindlimb and marker triads were fixed to the end of each pin. 3D motion of the bones was recorded as each subject trotted in hand. Three rotations were expressed using an attitude vector based on the finite helical angle method. Three translations were calculated as the motion of the tibia relative to the third metatarsus. Angular and translation data were mostly coupled with flexion angle. Internal/external rotation during stance and translations during swing showed evidence of noncoupled motion. Although the majority of tarsal motion occurs in the tarsocrural joint, there is evidence that translations and rotations occur in other locations within the tarsal joint and that some of these are related to the tarsal joint ‘snapping’ phenomenon.

This research provides a set of reference 3D kinematics which will aid in the study of the aetiology and mechanical effects of tarsal joint lameness.
Modelling the oxygen cost of transport in competitions over ground of variable slope
Authors: SCHROTER R. C. , MARLIN D. J.
Published: June 2010

This study provides an objective method for estimating the oxygen consumption of horses while running on variable slopes so that realistic comparisons may be made of the locomotory transport cost involved in 3‐day events, particularly the Speed and Endurance Test, at sites of differing terrain. A knowledge of the work profile over a particular course would enable competitors to plan speed and interval times appropriately along its length. We have developed a semi‐empirical, but mechanistically based, model to calculate the oxygen cost of transport [COTpath in ml O2/kg/m path] for running on the flat, up or down a slope of given gradient (from −0.3 to +0.3). The model is then used to calculate the overall effort of running on a number of 3‐day event courses of differing standard; the model does not assess the energetic cost of jumping. The cost of transport over the range of gradient of −0.3 to +0.3 was modelled using the following equations:

On the flat or uphill: COTpath = 0.123 + 1.561(gradient) Downhill:

COTpath = 0.123 + 1.591(gradient) + 9.762(gradient)2 + 14.0(gradient)3
Gas exchange during intense exercise in Standardbreds with earlierRhodococcus equipneumonia
Authors: FUNKQUIST P. , DEMMERS S. , HEDENSTIERNA G. , WAERN M. JENSEN , NYMAN G.
Published: June 2010

It is not known if pulmonary function and gas exchange during exercise are altered after pyogranulomatous pneumonia caused byRhodococcus equiinfection in the foal. The aim was to evaluate whether pulmonary gas exchange during high intensity exercise was altered in mature Standardbreds with a history ofR. equipneumonia as foals. In 7 foals,R. equipneumonia was confirmed and treated. At age 3 years, when these horses were subjected to professional training, an inclined treadmill exercise test including 4 speeds was performed. Samples were collected when a steady state in V̇O2was obtained. Red cell volume, heart rate, respiratory rate, and systemic and pulmonary mean arterial pressures were measured and cardiac output calculated. Oxygen and carbon dioxide tensions in arterial and mixed venous blood were analysed. The alveolar ventilation and the alveolar‐arterial oxygen tension difference were determined. Pulmonary gas exchange was assessed and the ventilation‐perfusion distribution, VA/Q, was estimated by the multiple inert gas elimination technique. Ventilation‐perfusion mismatch and shunt were determined and diffusion limitation calculated. The gas exchange in Standardbred trotters previously infected withR. equiand successfully treated was not compromised during intense treadmill exercise compared with reference values for healthy, fit Standardbreds.

We conclude that adult Standardbreds trotters with diagnosedR. equipneumonia as foals, can achieve an adequate gas exchange at a workload close to V̇O2peak.
Effects of different volumes of autologous blood instilled into the airways of horses on pulmonary function during treadmill exercise
Authors: KINGSTON J. K. , BAYLY W. M. , SIDES R. H.
Published: June 2010

Exercise‐induced pulmonary haemorrhage has been associated with reduced performance in racing horses. However, it is unclear what volume of blood loss into the lungs impairs performance. The purpose of the present study was to determine the minimal volume of autologous blood instilled into the airways that significantly affects performance and pulmonary function in exercising horses. Six Thoroughbred horses performed 2 exercise bouts on each of 4 treatment test days. Each exercise bout consisted of a 2 min warm‐up at 4 m/s followed by running at a speed equivalent to 115% V̇O2max, until fatigued. For the first run of each testing day there was no treatment (baseline run). Prior to the second run either there was no treatment (control) or 100, 50 or 25 ml of autologous blood was instilled into the airways on the right hand side. During each test, arterial and mixed venous blood was sampled, and V̇O2, VCO2and breathing mechanics measured. The results of this study indicate that unilateral instillation of 100 ml of blood or less into the airways of horses does not significantly affect pulmonary function, breathing mechanics or performance during supramaximal exercise. The results of this study may be helpful in determining the significance of exercise‐induced pulmonary haemorrhage on racing performance.
Structural and oxidative enzyme characteristics of the diaphragm
Authors: POOLE D. C. , PETRISKO R. N. , ANDERSON L. , FEDDE M. R. , ERICKSON H. H.
Published: June 2010

During exercise, the horse can achieve oxygen uptakes and ventilations in excess of 200 ml/kg/min and 1800 I/min, respectively. Whether the diaphragm has the capacity to contribute substantially to inspiratory effort in the exercising horse is not known. To investigate the potential for the horse diaphragm to generate tension, lung displacement and sustain ventilatory function, we measured diaphragm thickness, muscle length and oxidative enzyme activity (citrate synthase) within the ventral, medial and dorsal costal and crural diaphragm. In the diaphragms of 6 mature horses (5 Thoroughbreds, one Quarter Horse; body mass (mean ± s.e.) 475 ± 14 kg, age 4 ± 1 years), the mass of the freshly‐excised diaphragm was 4.54 ± 0.19 kg of which 79% was the costal diaphragm, 17% the crural diaphragm and 4% the central tendon. The medial costal region (2.1 ± 0.1 cm) was significantly thicker (P<0.05) than either the ventral (1.4 ± 0.1 cm) or dorsal (1.2 ± 0.2 cm) costal regions and the crural diaphragm was significantly thicker (>3.2 ± 0.3 cm, P<0.05) than any costal diaphragm region. With respect to the costal diaphragm, excised muscle length was greatest (P<0.05) in the medial costal (17.2 ± 1.0 cm) than either the ventral costal (<12.6 ± 1.5 cm) or dorsal costal (<13.9 ± 1.8 cm) regions and therefore the medial region would be expected to exhibit the greatest absolute length change on inspiration. Citrate synthase activity was high throughout the diaphragm (40.8 ± 11.3 to 55.3 ± 9.7 μmol/g/min), but was not significantly different among regions. These structural characteristics and the oxidative potential of the horse diaphragm are consistent with the diaphragm providing a significant and substantial contribution to the inspiratory effort during exercise in the horse. Consequently, clinical and physiological investigations of exercise performance should not ignore the potentially crucial importance of the diaphragm.
Heart size estimated by echocardiography correlates with maximal oxygen uptake
Authors: YOUNG L. E. , MARLIN D. J. , DEATON C. , BROWN‐FELTNER H. , ROBERTS C. A. , WOOD J. L. N.
Published: June 2010

Maximum oxygen uptake also appears to correlate to athletic performance in horses. In the Thoroughbred industry, there has long been an empirical theory that heart size is related to athletic performance, despite a lack of scientific evidence supporting this assertion. To investigate the relationship between peak oxygen consumption (V̇O2max) and cardiac size measured by echocardiography, guided M‐mode and 2‐dimensional echocardiography were performed in 17 conditioned Thoroughbreds with a range of V̇O2max from 126 to 217 ml/min/kg STPD (mean ± s.d. 158 ± 28 ml/min/kg). Horses were age 2–10 years and weighed 430–510 kg. Echocardiography was performed using a Vingmed System V echocardiograph with a 2.25 MHz phased array ultrasound transducer. All images were obtained from the right hemithorax using a short axis view of the left ventricle (LV) at the level of the chordae tendinae. All horses were free from significant regurgitation at the aortic or mitral valves. Maximal oxygen uptake was measured during a standardised incremental treadmill exercise test to fatigue. Maximal oxygen uptake was correlated significantly with LVIDd (r = 0.71; P = 0.001), MWT (r = 0.72; P = 0.001), LV mass (r = 0.78; P = 0.0002) and LV short‐axis area (r = 0.69; P = 0.003). When indices of heart size were indexed to bodyweight, the correlation between V̇O2max and indices of heart size were LVIDd (r = 0.57; P = 0.01), MWT (r = 0.44; P = 0.07), LV mass (r = 0.78; P = 0.0002) and LV short‐axis area (r = 0.69; P = 0.003). The current study suggests there is a strong relationship between V̇O2max and measurements of left ventricular size in Thoroughbred horses when individuals with a range of V̇O2max are compared.
The effect of coat clipping on thermoregulation during intense exercise in trotters
Authors: MORGAN K. , FUNKQUIST P. , NYMAN G.
Published: June 2010

The aim of this study was to study the physiological, especially thermoregulatory, responses during intense exercise in the clipped horse compared to the horse with winter coat. Six Standardbred trotters were studied before and after clipping. They performed an inclined incremental high intensity treadmill exercise test and were monitored during recovery. The clipped horse differed significantly (ANOVA) during exercise as compare to coated: less increase in central venous blood temperature, higher skin surface temperature, greater difference skin to ambient temperature and higher rate of nonevaporative heat loss. The clipped horse had significantly lower total cutaneous evaporative heat loss from walk to end of peak exercise and a shorter time for recovery for the respiratory rate using a paired t test. The clipped horse showed a tendency (P = 0.059) to decreased oxygen uptake during the stepwise increase in workload. We concluded that the clipped horse experienced less strain on the thermoregulatory system due to an enhanced heat loss. Some clipped horses in the study showed a more efficient power output; future studies with emphasis on respiration and oxygen demand are needed to explain this.