A study using a canine hydrotherapy treadmill at five different conditions to kinematically assess range of motion of the thoracolumbar spine in dogs.

BACKGROUND: Incline treadmill and underwater treadmill (UWTM) exercises are common canine rehabilitation modalities , which are often used in isolation in dogs recovering from spinal surgery. Early use of an incline during UWTM exercise may have the potential to improve rehabilitation outcomes in dogs, but, it is hypothesised that dorsoventral movement of the spine may be excessive meaning it is unsuitable in some circumstances. OBJECTIVES: The purpose of this study was to identify changes in canine spinal kinematics in dogs when using a dry treadmill at different angles of incline compared to an underwater treadmill using the same inclines. METHODS: Eight dogs were encouraged to walk on a dry, horizontal, underwater treadmill as well as under the same conditions with both a 10% and 20% incline. This was then repeated at a 10% and 20% incline with the addition of water to hock level. Data were collected using reflective anatomical markers placed at the occipital protuberance, T1, T13, L3, L7 and sacral apex, captured by a high-speed camera facing the lateral aspect of the treadmill. Dorsoventral motion of the spine as well as flexion, extension and range of motion (ROM) of T1, T13, L3 and L7 were recorded. RESULTS: We found significant differences in dorsoventral spinal ROM at T1, L3 and L7, but no significant differences in T13 ROM. No significant differences were found in flexion and extension of any of the joints assessed when comparing dry conditions to the use of water (P>0.05). CONCLUSIONS: The lack of significant differences in joint flexion and extension at T1, T13, L3 and L7 indicates the potential safe use of combining underwater treadmill and incline exercise in canine rehabilitation. However, a lack of uniformity in results makes distinguishing any patterns of significance difficult. More research is needed to establish the effects of these exercises in additional planes of motion before a treatment protocol can be established.

Treatment of experimentally induced osteoarthritis in horses using an intravenous combination of sodium pentosan polysulfate, N-acetyl glucosamine, and sodium hyaluronan.

OBJECTIVE: To assess the effects of sodium pentosan polysulfate (PPS), N-acetyl glucosamine (NAG), and sodium hyaluronan (HA) in horses with induced osteoarthritis (OA). STUDY DESIGN: Experimental. ANIMALS: Adult Standard bred horses (n = 16). METHODS: OA was induced arthroscopically in 1 intercarpal joint; 8 horses were administered 3 mg/kg PPS, 4.8 mg/kg NAG, and 0.12 mg/kg HA (PGH), intravenously (IV), weekly and 8 horses were administered an equivalent volume of saline IV until study completion (day 70). Horses underwent a standardized treadmill exercise program. Clinical and radiographic findings and synovial fluid analysis were evaluated throughout the study. Macroscopic, histologic, histochemical, and biochemical findings were evaluated after necropsy. Comparisons of interest included OA and non-OA joints of saline treated horses and OA joints of PGH treated horses and OA joints of saline treated horses. Results were statistically analyzed with significance set at P < .05. RESULTS: OA caused increases in clinical assessment scores, synovial fluid variables, radiographic, macroscopic, and histologic cartilage scores, synovial fluid and cartilage chondroitin sulfate 846-epitope and glycosaminoglycan concentration. Total radiographic scores, total macroscopic joint pathology and macroscopic cartilage pathology scores were significantly reduced in horses treated with PGH compared with saline treated horses. Synovial fluid total protein concentration and white blood cell count were higher in OA joints of PGH treated horses compared with saline treated horses. There were no other significant differences between treatment groups. CONCLUSIONS: Improvements in macroscopic variables were not supported by other outcomes. Further evidence is needed before PGH can be recommended as a therapeutic option for osteoarthritis in horses.

Gastric emptying, intestinal absorption of electrolytes and exercise performance in electrolyte-supplemented horses.

Horses lose considerably more electrolytes through sweating during prolonged exercise than can be readily replaced through feeds. The present study tested an oral electrolyte supplement (ES) designed to replace sweat electrolyte losses. We measured gastric emptying of 3 litres of ES (using gamma imaging of (99)Tc-sulfide colloid), the absorption of Na(+) and K(+) from the gastrointestinal tract using (24)Na(+) and (42)K(+), and the distribution of these ions in the body by measuring radioactivity within plasma and sweat during exercise. Three litres of ES emptied from the stomach as fast as water, with a half-time of 47 min, and appeared in plasma by 10 min after administration (n = 4 horses). Peak values of plasma (24)Na(+) and (42)K(+) radioactivity occurred at 20-40 min, and a more rapid disappearance of K(+) radioactivity from plasma was indicative of movement of K(+) into cells (n = 3 horses). In a randomized crossover experiment (n = 4 horses), 1 h after administration of placebo (water), 1 or 3 litres of ES containing (24)Na(+), horses exercised on a treadmill at 30% of peak oxygen uptake until voluntary fatigue. The (24)Na(+) appeared in sweat at 10 min of exercise, and when horses received 3 litres of ES the duration to voluntary fatigue was increased in all horses by 33 ± 10%. It is concluded that an oral ES designed to replace sweat ion losses was rapidly emptied from the gastrointestinal tract, rapidly absorbed in the upper intestinal tract and rapidly distributed within the body. The ES clearly served as a reservoir to replace sweat ion losses during exercise, and administration of ES prior to exercise resulted in increased duration of submaximal exercise.

Bee pollen product supplementation to horses in training seems to improve feed intake: A pilot study.

The objective of this study was to determine the efficacy of supplementation of Dynamic Trio 50/50, a bee pollen-based product, to improve physical fitness, blood leukocyte profiles, and nutritional variables in exercised horses. Ten Arabian horses underwent a standardised exercise test (SET), then were pair-matched by sex and fitness and randomly assigned to BP (receiving 118 g of Dynamic Trio 50/50 daily) or CO (receiving 73 g of a placebo) for a period of 42 days. A total collection was conducted from days 18 to 21 on six geldings to determine nutrient retention and neutral detergent fibre (NDF) and acid detergent fibre (ADF) digestibility. Horses were exercise conditioned and completed another SET on day 42. V160 and V200 were calculated from SET heart rates (HR). Lactate, glucose, haematocrit (HT) and haemoglobin (HB) concentrations were determined from SET blood samples. Total leukocyte count, and circulating numbers of various leukocytes and IgG, IgM and IgA concentrations were determined in rest and recovery blood samples from both SETs. Geldings on BP (n = 3) ate more feed than CO. BP had less phosphorus excretion, and tended to retain more nitrogen. BP tended to digest more NDF and ADF while having lower NDF digestibility and tending to have lower ADF digestibility. No treatment differences existed for V160 and V200, HR, lactate, HT and HB. There was a trend for lymphocyte counts to be lower in BP than CO on day 42. Dynamic Trio 50/50 supplementation may have a positive effect on performance by helping horses in training meet their potentially increased nutrient demands by increasing feed intake and thus nutrient retention.

Does usefulness of potassium supplementation depend on speed?

REASONS FOR PERFORMING STUDY: Electrolyte mixtures given to counter sweat loss usually contain abundant potassium. However, increases in plasma [K+] occur with exercise and supplementation may further increase plasma levels, potentially increasing the risk of neuromuscular hyperexcitability and development of adverse clinical sequellae. This proposition requires study. OBJECTIVES: To compare effects of a K-rich electrolyte supplement (EM+K) to a K-free one (EM-K) on plasma [K+], [Ca++] and acid-base status during an endurance incremental exercise test on the treadmill. METHODS: The test consisted of 3 bouts (simulating loops in an endurance race) of 12 km performed at 6, then 7, then 8 m/sec with 25 min rest stops (S1, S2) between loops on 13 endurance trained Arabian horses (7 EM-K, 6 EM+K). Electrolytes were supplied orally 60 mins before exercise (Pre) and at each stop. Blood samples were taken before exercise and during exercise, each S and 120 mins of recovery (R). Blood was analysed for pH, PCO2, packed cell volume (PCV), plasma [Na+], [K+], [Cl-], [Ca++], glucose, and lactate [La-]; plasma [H+] and osmolality (osm) were calculated. The dietary cation anion difference (DCAD) was calculated to be -27 meq/dose EM-K and 109 meq in EM+K, respectively. RESULTS: Plasma [H+] decreased during the 6 and 7 m/sec loops, increased during the 8 m/sec loop, and returned to Pre at S1, S2 and R. Plasma [K+] was higher at 8 m/sec and plasma [Ca++] was overall lower in the EM+K group compared to EM-K. Other findings included higher overall PCV, overall glucose, and [La-] during the 8 m/sec loop (P<0.040) in EM+K compared to EM-K horses. CONCLUSIONS: EM+K supplementation leads to higher plasma [K+] increasing the risk of neuromuscular hyperexcitability during exercise. Acute effects of a lower DCAD in EM-K may have led to higher plasma [Ca++]. Potassium-rich electrolytes may have triggered the release of epinephrine, contributing to higher PCV, glucose release and increased lactate production. POTENTIAL RELEVANCE: Lower plasma [K+] and higher plasma [Ca++] with EM-K supplementation may help reduce the risk of conditions associated with neuromuscular hyperexcitability occurring especially during higher speeds in endurance races.

The effects of dietary N-3 and antioxidant supplementation on erythrocyte membrane fatty acid composition and fluidity in exercising horses.

REASONS FOR PERFORMING STUDY: Fatty acid supplementation could modulate erythrocyte membrane fluidity in horses at rest and during exercise, but information is lacking on the effect of exercise. OBJECTIVES: To assess the effect of exercise with, and without, an oral antioxidant supplementation enriched with n-3 fatty acids on erythrocyte membrane fluidity (EMF) and fatty acid composition in eventing horses. METHODS: Twelve healthy and regularly trained horses were divided randomly into 2 groups: group S received an oral antioxidant cocktail enriched in n-3 fatty acid (alphatocopherol, eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]) whereas group P was placebo-treated. At the end of 4 weeks, all horses performed a standardised exercise test (ET) under field conditions. Venous blood was sampled before starting treatment (TO), immediately before (T1) as well as 15 min (T2) and 24 h (T3) after ET. Spin labelled (16-DOXYL-stearic acid) red blood cell membranes were characterised using the relaxation correlation time (Tc in inverse proportion to EMF). Fatty acid composition (%) of the membrane was determined by gas-liquid chromatography. RESULTS: Supplementation did not induce changes in EMF (T1 vs. TO) but significant changes in membrane composition were observed and there were increases in n-3 polyunsaturated fatty acid PUFA, n-3/n-6 ratio, and total n-3 fatty acids. Exercise (T2 vs. T1) induced a significant decrease of EMF in group P (Tc: +19%, P<0.05) and nonsignificant decrease in group S (Tc: +5%), whereas membrane fatty acid composition did not change in either group. During the recovery period (T3 vs. T2), EMF decreased significantly in group S (Tc: +29%, P<0.05) and nonsignificantly in group P (Tc: +18%) without any significant changes in fatty acid composition. CONCLUSION AND POTENTIAL RELEVANCE: An enriched oral antioxidant supplementation induced changes in membrane composition, which modulated the decrease in EMF induced by exercise. Long chain n-3 fatty acid supplementation might therefore be beneficial.

Oral vitamin E supplementation on oxidative stress, vitamin and antioxidant status in intensely exercised horses.

REASONS FOR PERFORMING STUDY: Vitamin E is the most commonly supplemented antioxidant in horses; however, previous research is not conclusive as to the recommended level for exercising horses. OBJECTIVE: To evaluate the effects of 3 levels of vitamin E supplementation on oxidative stress and vitamin/antioxidant status in intensely exercised horses to determine the optimal level of vitamin E supplementation. METHODS: Twelve unfit Standardbreds were divided into 3 groups, supplemented orally with 0 (CON), 5000 (MOD), or 10,000 (HI) iu/day of DL-alpha-tocopheryl acetate. The 3 x 3 Latin square design consisted of three 4 week supplementation periods with 4 week wash out periods between. After each period, horses underwent a treadmill interval exercise test. Blood samples were collected and heart rate (HR) measured before, during and after exercise. Data were analysed using ANOVA with repeated measures in SAS. RESULTS: The CON group had lower HR throughout the test compared to the MOD and HI groups (P<0.05). There was an increase in plasma retinol (RET), beta-carotene (BC), red blood cell total glutathione and glutathione peroxidase with exercise (P<0.05), but all groups returned to baseline after 24 h. Plasma alpha-tocopherol (TOC) increased from baseline with exercise (P<0.0001) in all groups; treatment differences were observed at 24 h (P<0.05). The HI and CON groups had lower BC compared to the MOD group (P = 0.05). CONCLUSIONS: Horses supplemented with vitamin E, at nearly 10-times the 1989 NRC recommended level, did not experience lower oxidative stress compared to control horses. Additionally, lower plasma BC levels observed in the HI group, which may indicate that vitamin E has an inhibitory effect on BC metabolism. POTENTIAL RELEVANCE: Supplementation above control levels is not more beneficial to oxidative stress and antioxidant status in intensely exercising horses; indeed, levels 10 times in excess may be detrimental to BC and should be avoided.

Effects of different levels of calcium and phosphorus intake on calcium homeostasis in exercising horses.

HYPOTHESIS: Increasing levels of dietary calcium (Ca) and phosphorous (P) might have a negative impact on parathyroid hormone (PTH) response and result in a more pronounced hypocalcaemia during high-speed exercise in horses. MATERIAL AND METHODS: In successive order, five trained horses were fed 33 g Ca and 19 g P (approximately 100% NRC, adequate intake), 64 g Ca and 38 g P (moderately high intake) or 96 g Ca and 56 g P (high intake). Each horse was adapted to each diet over a 21 day period before undergoing a standardised exercise test (SET) on a treadmill. The SET comprised 5 steps (each step 4 min duration, 3% incline, first step 5 m/sec, followed by increments of 1 m/sec). Blood samples were taken at defined times. RESULTS: Blood lactate, plasma intact PTH (PTHi) and plasma inorganic P (Pi) increased during exercise (P<0.05), blood pH and blood ionised Ca2+ (Ca2+, adjusted to a pH of 7.4) declined during SETs (P<0.05) whereas total plasma Ca (CaT) and Mg (MgT) remained constant. The most exaggerated drop in Ca2+ and lactate peaks were found for the adequate Ca and P intake at 7, 8, and 9 m/sec during SET (treatment P<0.05). At 120 min after exercise, Ca2+ levels exceeded resting concentrations with higher Ca2+ values for the higher Ca intake (Ca2+: adequate 1.58 +/- 0.07 mmol/, moderately high 1.63 +/- 0.04 mmol/l, high 1.65 +/- 0.02 mmol/l, P<0.05). Concomitantly, 120 min after exercise, PTHi returned to basal concentrations with higher PTH concentrations for the adequate Ca intake than the other two treatments (PTHi: adequate 45.6 +/- 72.8 pg/ml, moderately high 11.6 +/- 13.6 pg/ml, high 2.6 +/- 2.3 pg/ml, P<0.05). During recovery (30 min, 120 min and 24 h after exercise) MgT concentrations were depressed (P<0.05) for the high Ca intake (P<0.05). CONCLUSION: These results suggest that high dietary Ca and P intake did not impair PTH responses during exercise and recovery, but might depress Mg metabolism. POTENTIAL RELEVANCE: High Ca and P intake might have some potential to increase the availability of blood Ca2+ and Pi in the recovery phase after intensive exercise, but detrimental effects on Mg homeostasis might offset this potential benefit.

Effects of feeding a blend of grains naturally contaminated with Fusarium mycotoxins on feed intake, metabolism, and indices of athletic performance of exercised horses.

An experiment was conducted to determine the effect of feeding blends of grains naturally contaminated with Fusarium mycotoxins to mature, exercised horses, and to test the efficacy of a polymeric glucomannan mycotoxin adsorbent (GM polymer) in preventing Fusarium mycotoxicoses. Six mature, mixed-breed mares with an average BW of 530 kg were assigned to one of three dietary treatments for 21 d in a replicated 3 x 3 Latin square design. Feed consumed each day was a combination of up to 3.5 kg of concentrates and 5.0 kg of mixed timothy/alfalfa hay (as-fed basis). The concentrates fed included 1) manage; 2) blend of contaminated grains; and 3) contaminated grains + 0.2% GM polymer (MTB-100, Alltech Inc., Nicholasville, KY). Concentrates containing contaminated grains averaged 11.0 ppm deoxynivalenol, 0.7 ppm 15-acetyldeoxynivalenol, and 0.8 ppm zearalenone (as-fed basis). Feed intake and BW were monitored over a 21-d period. Horses were maintained on a fixed exercise schedule throughout the experiment. At the end of the experiment, each horse completed a time-to-fatigue treadmill step test. Variables measured during pretest, each step of the test, and 5 and 10 min posttest were as follows: 1) time-to-fatigue, 2) heart rate, 3) hematological variables, and 4) serum lactate concentration. Each step consisted of 2 min of fast trot with a 2% increase in incline after each 2 min. Feed intake by horses fed contaminated grains was decreased compared with controls throughout the experiment (P < 0.05). Supplementation of 0.2% GM polymer to the contaminated diet did not alter feed intake by horses compared with those fed the unsupplemented contaminated diet. All hay was consumed regardless of concentrate fed. Weight loss from 0 to 21 d was observed in horses fed contaminated grains compared with controls (P < 0.05). No effect of diet was seen on variables used to measure athletic ability, although the results showed an expected response to exercise for a fit horse. We conclude that exercised horses are susceptible to Fusarium mycotoxicoses as indicated by appetite suppression and weight loss.

Effects of draught load exercise and training on calcium homeostasis in horses.

This study was conducted to investigate the effects of draught load exercise on calcium (Ca) homeostasis in young horses. Five 2-year-old untrained Standardbred horses were studied in a 4-month training programme. All exercise workouts were performed on a treadmill at a 6% incline and with a constant draught load of 40 kg (0.44 kN). The training programme started with a standardized exercise test (SET 1; six incremental steps of 5 min duration each, first step 1.38 m/s, stepwise increase by 0.56 m/s). A training programme was then initiated which consisted of low-speed exercise sessions (LSE; constant velocity at 1.67 m/s for 60 min, 48 training sessions in total). After the 16th and 48th LSE sessions, SETs (SET 2: middle of training period, SET 3: finishing training period) were performed again under the identical test protocol of SET 1. Blood samples for blood lactate, plasma total Ca, blood ionized calcium (Ca(2+)), blood pH, plasma inorganic phosphorus (P(i)) and plasma intact parathyroid hormone (PTH) were collected before, during and after SETs, and before and after the first, 16th, 32nd and 48th LSE sessions. During SETs there was a decrease in ionized Ca(2+) and a rise in lactate, P(i) and intact PTH. The LSEs resulted in an increase in pH and P(i), whereas lactate, ionized Ca(2+), total Ca and intact PTH were not affected. No changes in Ca metabolism were detected in the course of training. Results of this study suggest that the type of exercise influences Ca homeostasis and intact PTH response, but that these effects are not influenced in the course of the training period.

Metabolic responses to oral tryptophan supplementation before exercise in horses.

This study was conducted to evaluate the effects of oral tryptophan (Trp) supplementation on exercise capacity and metabolic responses in horses. Three horses had to perform an exercise test: a 15-min warm-up followed by a 60-min walk (1.7 m/s, W1), a 10-min trot (3.1 m/s, T1), a second 60-min walk (1.7 m/s, W2), a second 10-min trot (3.1 m/s, T2) and a final 30-min walk (1.7 m/s, W3) until the horses were unwilling to continue. The horses exercised on a treadmill at a 6% incline and with a constant draught load of 40 kg (0.44 kN). Two hours before exercise horses were given 50 g Trp (9.8-10.7 g Trp/100 kg BW) by nasogastric tube. A control exercise test was conducted without Trp. During the control test, one horse was able to finish the final 30-min walk (W3), whereas two horses finished W3 after Trp administration. Higher plasma Trp levels after Trp administration did not change significantly during exercise (Trp: start exercise, 524 +/- 41 micromol/l; end exercise 547 +/- 20 micromol/l; control: start exercise, 70 +/- 10 micromol/l; end exercise, 58 +/- 21 micromol/l). After Trp supplementation, blood lactate concentrations were significantly lower after the first and second trotting periods. Free fatty acids in plasma increased during exercise without any treatment-related differences. Although experimental plasma Trp levels were seven times higher than the control levels, Trp supplementation had no effect on exercise performance and metabolic responses to draught load exercise.

Aerobic training, but not creatine supplementation, alters the gluteus medius muscle.

The aim of the present study was to investigate the effect of oral supplementation of creatine on the muscular responses to aerobic training. Twelve purebred Arabian horses were submitted to aerobic training for 90 d, with and without creatine supplementation, and evaluated with respect to BW and BCS and to the area and frequency of the different types of muscle fibers in the gluteus medius. Supplementation consisted of the daily administration of 75 g of creatine monohydrate mixed into the ration for the 90 d of training. Physical conditioning was conducted on a high-performance treadmill, and training intensity was stipulated by calculating the velocity at which blood lactate reaches 4 mmol/L, determined monthly for each animal. The individual intensity of physical force at 80% of aerobic threshold was established. Morphometry of gluteus medius muscle fibers was performed on frozen sections processed for histochemical analysis of myosin adenosine triphosphatase and immunohistochemistry of slow-contracting myosin. The results demonstrated that the animals maintained a moderate BCS without alteration of BW during the course of training, providing evidence of equilibrium between food intake and caloric expenditure during the study period. The present study demonstrated that aerobic training for 90 d caused hypertrophy of fiber types I (P = 0.04), IIA (P = 0.04), and IIX (P = 0.01), as well as an increase in the relative area occupied by type I fibers (P = 0.02) at the expense of type IIX fibers (P = 0.03), resulting in modifications of the contractile and metabolic characteristics of the gluteus medius muscle. It was not possible to show any beneficial effect from creatine on the skeletal muscle characteristics examined.

The effect of dietary fish oil supplementation on exercising horses.

Ten horses of Thoroughbred or Standardbred breeding were used to study the effects of dietary fish oil supplementation on the metabolic response to a high-intensity incremental exercise test. Horses were assigned to either a fish oil (n = 6) or corn oil (n = 4) treatment. The fish oil (Omega Protein, Hammond, LA) contained 10.6% eicosapentaenoic acid and 8% docosahexaenoic acid. Each horse received timothy hay and a textured concentrate at a rate necessary to meet its energy needs. The supplemental oil was top-dressed on the concentrate daily at a rate of 324 mg/kg BW. Horses received their assigned diet for 63 d, during which time they were exercised 5 d/wk in a round pen or on a treadmill. During wk 1, horses exercised for 10 min at a trot. After wk 1, exercise time and intensity were increased so that at wk 5, exercise time in the round pen increased to 30 min (10 min of cantering and 20 min of trotting) per day. Starting at wk 6, horses were exercised 3 d/wk in the round pen for 30 min and 2 d/wk on a treadmill for 20 min. After 63 d, all horses performed an exercise test consisting of a 5-min warm-up at 1.9 m/s, 0% grade, followed by a step test on a 10% grade at incremental speeds of 2 to 8 m/s. Blood samples were taken throughout exercise. During exercise, horses receiving fish oil had a lower heart rate (treatment x time interaction; P < 0.05) and tended to have lower packed cell volume (treatment effect; P = 0.087). Plasma lactate concentrations were not affected by treatment. Plasma glucose concentrations were not different between groups during exercise but were lower (treatment x time interaction; P < 0.01) for the fish oil group during recovery. Serum insulin tended to be lower in fish oil horses throughout exercise (treatment effect; P = 0.064). There was a tendency for glucose:insulin ratios to be higher for fish oil-treated horses throughout exercise (treatment effect; P = 0.065). Plasma FFA were lower (treatment x time interaction; P < 0.01) in horses receiving fish oil than in horses receiving corn oil during the initial stages of the exercise test. Serum glycerol concentrations also were lower in fish oil-treated horses (P < 0.05). Serum cholesterol concentrations were lower in horses receiving fish oil (treatment effect; P < 0.05), but serum triglycerides were not affected by treatment (P = 0.55). These data suggest that addition of fish oil to the diet alters exercise metabolism in conditioned horses.

Comparison of the effects of fructose and glucose supplementation on metabolic responses in resting and exercising horses.

The aim of this study was to compare the effects of two different carbohydrate sources (fructose and glucose) on the metabolic responses in resting and exercising horses. The following regimes were fed in randomized order to five trained horses at rest and immediately before or during exercise. The resting regime comprised 0.6 kg grass meal pellets (control) or 0.6 kg grass meal pellets supplemented with either 50% glucose or 50% fructose. The exercise regime comprised 0.3 kg grass meal (control) or 0.6 kg grass meal pellets supplemented with either 50% glucose or 50% fructose fed immediately before or during simulated endurance exercise on a treadmill (30 km, total running time 120 min; 15 min rest after 60 min running time). Blood samples were collected for the analysis of glucose, insulin, free fatty acids (FFA) and lactate. In resting horses, glucose supplementation resulted in a significantly higher glycaemic and insulinaemic response than the control or fructose feedings (treatment P < 0.05). Plasma glucose levels were significantly higher after glucose supplementation given before or during exercise. Similar plasma glucose concentrations were observed after fructose was fed before exercise, whereas fructose supplementation during exercise resulted in a lower glycaemic response than glucose feeding (P < 0.05). Plasma insulin, FFA and lactate levels showed exercise-related changes (time P < 0.05), but treatment did not effect these results. Plasma glucose concentrations were elevated during the simulated endurance exercise after glucose feeding, and no counter-regulation by insulin occurred. The higher glycaemic response might be beneficial as exogenous glucose can be used as an energetic substrate during prolonged exercise. Fructose exhibited no clear advantages in comparison with glucose as a carbohydrate source for exercising horses.

Effects of ribose supplementation on selected metabolic measurements and performance in maximally exercising Thoroughbreds.

The objective of this study was to investigate the effects of ribose supplementation on blood ammonia-N, plasma lactic acid, plasma glucose, volume of oxygen consumption (VO2), heart rate, and performance in Thoroughbred geldings performing a maximal treadmill standardized exercise test (SET). The hypothesis tested was that ribose supplementation would decrease ammonia-N and lactic acid accumulation during exercise, and improve performance. Eight Thoroughbred geldings were assigned randomly to one of two groups: glucose or ribose. The glucose group received 0.15 g glucose/kg of BW, and the ribose group received 0.15 g of ribose/kg BW top-dressed on the feed twice daily. After 2 wk of glucose or ribose supplementation, a SET was performed. Blood was analyzed for blood ammonia-N, plasma lactic acid, and plasma glucose before exercise (0 min), every minute during SET, and at 15 and 30 min after exercise. Heart rate and VO2 were recorded for the duration of SET. After a 10-d washout period, geldings switched groups. Following another 2 wk of supplementation, a second SET was performed, and same data recorded. Blood ammonia-N and plasma lactic acid increased as duration of SET increased and reached a peak at 15 min after exercise. Peak plasma glucose was observed at 15 min after exercise, and peak heart rate and VO2 were recorded at highest speed during SET. Geldings supplemented with ribose had blood ammonia-N, plasma lactic acid, plasma glucose, VO2, heart rate, and performance similar to those of geldings supplemented with glucose. Results from this study show that supplementation with 0.15 g ribose/kg BW twice daily in the diet of conditioned Thoroughbred geldings for 2 wk does not influence blood ammonia-N, plasma lactic acid, plasma glucose, VO2, heart rate, or performance during SET or the first 30 min of recovery.

Effect of nutritional antioxidant supplementation on systemic and pulmonary antioxidant status, airway inflammation and lung function in heaves-affected horses.

An oxidant/antioxidant imbalance in favour of oxidants has been identified as playing a decisive role in the pathogenesis of chronic inflammatory airway diseases. Nutritional antioxidant supplementation might reduce oxidative damage by enhancement of the antioxidant defence, thereby modulating inflammatory processes. In a placebo-controlled, blind study, it was tested whether a dietary antioxidant supplement administered for 4 weeks would improve lung function and reduce airway inflammation in heaves-affected horses. Eight horses in clinical remission of heaves were investigated at rest and after a standardised exercise test before and after treatment with an antioxidant supplement (consisting of a mixture of natural antioxidants including vitamins E and C and selenium from a variety of sources) or placebo (oatfeed pellets without additive). Pulmonary function and exercise tolerance were monitored; systemic and pulmonary lining fluid uric acid, glutathione and 8-epi-PGF(2alpha) were analysed, and bronchoalveolar lavage (BAL) cytology and inflammatory scoring of the airways were performed. The antioxidant treatment significantly improved exercise tolerance and significantly reduced endoscopic inflammatory score. Plasma uric acid concentrations were significantly reduced, suggesting downregulation of the xanthine-dehydrogenase and xanthine-oxydase pathway. Haemolysate glutathione showed a nonsignificant trend to increase, while plasma 8-epi-PGF(2alpha) remained unchanged. Pulmonary markers and BAL cytology were not significantly affected by antioxidant supplementation. The present study suggests that the antioxidant supplement tested modulated oxidant/antioxidant balance and airway inflammation of heaves-affected horses.

Calcium homeostasis and intact plasma parathyroid hormone during exercise and training in young Standardbred horses.

Physical exercise is known to affect calcium homeostasis in horses, but there is little information on the hormonal regulation of calcium metabolism during exercise. In order to evaluate the effects of exercise and training on calcium homeostasis and intact plasma parathyroid hormone, 7 untrained Standardbred horses were studied in a 6 week training programme. These horses were accustomed to running on the treadmill 3 weeks before onset of training and were exercised on a high-speed treadmill with an initial incremental standardised exercise test (SET 1: 6 incremental steps of 5 min duration each; first step 5 m/s, increase 1 m/s). SET 1 was followed by a lactate-guided training programme (6 weeks in total) with 2 types of exercise in alternating order with a day of rest after each work day: high-speed exercise (HSE) of 15 min duration, starting at VLa4, continuous increase in speed every 60 s by 0.3 m/s (14 incremental steps); and low-speed exercise (LSE) at a constant velocity at VLa2.5, duration approximately 60-90 min. The whole training programme consisted of 8 HSE and 8 LSE sessions. HSE and LSE were calculated to require the same energy expenditure. A final SET (SET 2) finished the training programme. Blood samples for lactate, plasma total calcium [Ca], blood ionised calcium [Ca2+], blood pH, plasma inorganic phosphorus [P(i)] and plasma intact parathyroid hormone [PTH] were collected before, during and after SETs 1 and 2, before and after the first and eighth HSE and LSE. During SETs 1 and 2, HSEs 1 and 8 there was a decrease in ionised Ca2+ and pH and a rise in lactate, intact PTH and P(i). LSEs 1 and 8 resulted in an increase in pH, whereas lactate, ionised Ca2+, total Ca, P(i) and intact PTH were not affected. No changes in calcium metabolism were detected during training. Results of this study suggest that intact PTH is a mediator in counter-regulation of exercise-induced hypocalcaemia.

Antioxidant supplementation and pulmonary function at rest and exercise.

Antioxidants have been implicated in the reduction and prevention of oxidative stress during exercise. We hypothesised that a dietary supplement containing a mixture of natural antioxidants together with vitamins E, C and selenium, given for 4 weeks, would increase the systemic and pulmonary antioxidant capacity leading to a reduction in markers of oxidative damage and an improvement in pulmonary function during exercise. In 6 healthy horses studied, the antioxidant supplement significantly increased plasma concentrations of ascorbic acid (from mean +/- s.d. 16 +/- 7 to 23 +/- 4 micromol/l; P = 0.007) and alpha-tocopherol (from 10 +/- 3 to 14 +/- 3 micromol/l; P = 0.02) and increased the bronchoalveolar lavage pulmonary epithelial lining fluid (ELF) concentration of ascorbic acid compared to a placebo, but not significantly (2.0 +/- 0.9 mmol/l and 1.2 +/- 0.9 mmol/l, respectively; P>0.05). Alpha-tocopherol was not detected in ELF either before or after supplementation or exercise. The mean concentration of malondialdehyde (MDA) in ELF was lower following antioxidant supplementation compared to placebo and control periods, but not significantly. An intermittent exercise test consisting of 2 min at 70, 80 and 90% of the horses' individual maximum oxygen uptake, failed to induce significant systemic or pulmonary oxidative stress (based on the glutathione redox ratio (GRR) and the ascorbic acid redox ratio (ARR)) and lipid peroxidation (based on the concentration of thiobarbituric acid reactive substances in plasma and MDA in ELF) either for placebo or antioxidant treatments. There was a strong correlation between GRR and ARR in the pulmonary epithelial lining fluid (r = 0.89; P<0.0001). In healthy horses on a diet containing adequate levels of antioxidants, additional antioxidant supplementation has no apparent beneficial or detrimental effect on pulmonary function during moderate intensity exercise. The importance of antioxidant supplementation may only become apparent if the diet is deficient in antioxidants, if exercise intensity is higher or more prolonged, or if disease or additional stresses are present.

Effect of dietary lipid on response to exercise: relationship to metabolic adaptation.

The aim of the present study was to relate changes in muscle oxidative capacity and free fatty acid flux in response to oil supplementation to fuel utilisation during subsequent exercise of varying intensities. Following 10 weeks of oil supplementation there was an increased capacity for fat utilisation during low and moderate intensity exercise as indicated by a lower respiratory exchange ratio (RER) (P<0.05). We suggest that this was contributed to by a parallel increase in the oxidative capacity of muscle as indicated by a significant increase in the activity of muscle citrate synthase (CS) (P<0.05) and trend towards an increase in beta-Hydroxy acyl CoA dehydrogenase (beta-HAD), (P>0.05). In addition, low and moderate intensity exercise was associated with an exercise-induced increase in plasma free fatty acids (FFA) and there was an increased facility for uptake of FFA by working muscle from circulating triglycerides, as suggested by an increase in TL activity (P<0.01). The response to oil supplementation varied between individual horses and the magnitude of response, during the low intensity exercise test, in terms of difference in RER was correlated to the increase in CS activity (r2 = 0.95, P<0.05) following oil supplementation. There was no similar significant correlation with respect to FFA, TL or beta-HAD activity (P>0.05). The hypothesis in this study was that the metabolic adaptation to oil supplementation, in terms of exercise response, was related to individual increases in the activities of CS, beta-HAD or TL. However, the relationship between these parameters was unequivocal and requires further investigation, ideally with a larger group of horses.

Relationship between markers of blood oxidant status and physiological variables in healthy and heaves-affected horses after exercise.

Exercise-induced oxidative stress is investigated as a potential performance-limiting factor in human sports medicine. Therefore, the present study aimed to assess whether physiological variables that change with exercise intensity were correlated with blood oxidant markers in healthy and heaves-affected horses. Seven healthy horses, 8 heaves-affected in remission and 7 heaves-affected in crisis performed a standardised exercise test (SET) of stepwise increasing intensity. Variables monitored during exercise were heart rate (HR), venous plasma lactate (LA), packed cell volume (PCV) and arterial oxygen tension (PaO2). Oxidant markers (uric acid [UA], 8-iso-PGF2alpha and reduced [GSH] and oxidised glutathione [GSSG]) were analysed in venous peripheral blood sampled at rest (R), at peak-exercise intensity (Emax), 15 (E15) and 60 (E60) min after SET. There was a significant effect of heaves on oxidant markers and, therefore, correlation analyses between physiological variables and oxidant markers were performed separately per horse group. In healthy horses, UA analysed at Emax was positively correlated with LA. Furthermore, GSH analysed at Emax and E15 was positively correlated with PaO2. In healthy and heaves-affected horses in remission, GSH and GSSG determined at Emax were negatively correlated with HR. There was no significant correlation between 8-iso-PGF2alpha and physiological variables. In conclusion, a correlation between the physiological response to exercise and some oxidant markers exists in healthy horses. However, in heaves-affected horses the blood oxidant status is probably more dependant on airway disease than on exercise. Future studies should be undertaken to assess whether antioxidant supplementation might positively influence the oxidant-antiodidant balance in exercising horses.