bluuebunny/crossref_metadata_2025_split 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

SummarySix 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

SummaryThis 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

SummaryThere 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

SummaryDietary 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

SummaryHigh‐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

SummaryThe 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

SummaryThe 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

SummaryBasal 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

SummaryThree‐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

SummaryStudies 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

SummaryOur 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

SummaryTwelve 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.