The maximal lactate steady state (MLSS) has been considered the gold standard method to determine aerobic/anaerobic metabolism transition during continuous exercise executed by human beings and rats. Therefore, the aim of the present study was to determine MLSS for aerobic evaluation in swimming mice. Twenty-five adult male mice (90-day-old animals) were adapted to the deep aquatic environment at the temperature of 31 ± 1°C. The mice were submitted to five continuous exercise loads of 3, 4, 5, 6 and 7% of the body weight (bw) tied to the back, executed with 25-min duration and 48-h intervals between them. Blood samples were collected from the tail during swimming exercise (rest, 5, 10, 15, 20 and 25 min) for blood lactate concentration (LAC) determinations. The individual MLSS was considered as the highest intensity in which the increase on the LAC was equal to or below 1 mmol l− 1 from the 10th to the 25th minute of exercise. The results showed that 36% of the swimming mice presented MLSS at 4% bw, 20% at 3% bw and 6% bw, 16% at 5% bw and 8% at 7% bw. The LAC at the MLSS was 5.78 ± 0.29 mmol l− 1 (4.40–6.67 mmol l− 1). These results indicate that the MLSS of mice swimming with additional weight for the final 15 of 25 min of exercise could be determined.

Few equine studies exist comparing the effects of different forms of training. This study tested the following hypothesis: interval training (IT) results in similar or better fitness parameters in Thoroughbreds when compared to continuous incremental training (CT) of the same workload with fewer galloping strides. Two groups of five horses underwent 6 weeks of IT or CT. Fitness levels were established before and following training. Both groups showed significant increases in VO2max (P < 0.05), lactate threshold (P < 0.05), work rate corresponding to 100% VO2max (P < 0.05) and work to fatigue during an incremental and sprint exercise test (P < 0.05). The interval-trained group had a significant increase in peak lactate values (P < 0.05) and a significant decrease in body weight (P < 0.05). The increase in VO2max of the interval group was greater than the increase in VO2max of the continuous incremental group (P = 0.10), increasing 27.38 ± 8.44 and 14.64 ± 2.66%, respectively. The interval group took significantly fewer galloping strides than the continuous incremental group for all weeks of training (P < 0.05). It is considered that supramaximal IT improves equine fitness as well as CT of the same workload with fewer galloping strides.

Intense exercise has been associated with free radical damage that forms potentially measurable by-products in the blood and muscle of exercising subjects. The extent of damage to the exercising animal has yet to be conclusively determined, and studies often focus on by-products in the blood rather than muscle. The current study examined the presence of oxidative products in the muscle of exercising horses as well as the effects of excess vitamin E on the presence of these products. Eight Thoroughbred horses were used in a crossover design, with one group being fed vitamin E at the 1989 NRC [National Research Council (1989) Nutrient Requirements of Horses. 5th revised edn.; Washington DC: National Academy Press, pp. 48] level recommended for horses in moderate to intense work (80 IU kg DM− 1), and the second group being fed the control diet plus 3000 IU day− 1dl-α-tocopheryl acetate. The horses underwent an 8-week training programme and a final standard exercise test (SET). During the SET, the horses ran on a 6° incline to exhaustion. Muscle samples were biopsied before and after performing the SET and analysed for the presence of carbonyl groups and ubiquitin. Blood was collected prior to the SET and analysed for vitamin E. No significant differences in plasma vitamin E were found between treatment groups. However, myofibril carbonylation, a product of free radical damage to muscle tissue, was found to be lower in vitamin E-supplemented horses post-SET exercise (P < 0.05), suggesting that vitamin E influences some measures of oxidative stress in exercising horses, particularly following a strenuous bout of exercise. Ubiquitin was not detected in myofibrils, indicating clearance of carbonyl groups by a different mechanism.

Human heart rate monitors (HRMs) are frequently used in equine studies to measure heart rate (HR) and interbeat intervals (IBIs). However, to date, the most commonly used HRM (the Polar® system) in horses has not been validated against simultaneously recorded electrocardiogram (ECG) signals during a range of ambulatory conditions. Polar® S810i and ECG IBIs were simultaneously recorded from six horses under three conditions commonly included in behavioural observation: standing at rest, loose in the stable and at liberty in a field. Following recording, Polar® IBI data were corrected for error processing in cardiac data. Corrected and uncorrected Polar® data were then compared with simultaneously recorded ECG data using a variety of commonly measured time and frequency domain parameters (e.g. HR variability (HRV)). Polar® data collected while horses were stabled or in the field were significantly different from ECG data, even following correction of the data, and therefore, it may not be possible for the two systems to be used interchangeably. This study indicates the need for caution while using Polar® S810i for collecting HRV data, unless horses are stationary, and even when the IBI data are corrected for measurement error.

Methoxy polyethylene glycol–epoetin β (pegylated epoetin β, peg-epoetin β, Mircera®) is an erythropoiesis-stimulating agent that is synthesized by pegylating epoetin β. It is prohibited in racehorses and humans because it enhances their performance. It is detectable in human urine and plasma using the isoelectric focusing–double-blotting (IEF–DB) method that has been widely applied in human doping control laboratories to detect doping with recombinant erythropoietins (EPOs). Fifty micrograms of peg-epoetin β were administered intravenously to a 450 kg female Thoroughbred, and blood was collected for 48 h. The plasma was processed by immunopurification followed by IEF–DB. The analytical procedures required about 2 days. No peg-epoetin β was detected in the baseline plasma collected prior to drug administration. It was readily detected in samples collected at 2, 4, 6, 8, 24 and 48 h. The isoforms showed a characteristic pattern that differed from epoetin β and was unlike any other known erythrocyte-stimulating agent or recombinant EPO. No peg-epoetin β was detected in plasma from five control horses. The plasma samples were also tested by a rapid, automated and chemiluminescent immunometric assay for EPO (Immulite®). The samples collected from the treated horse at 2–48 h contained the equivalent of approximately 200–800 pg ml− 1 of peg-epoetin β. The samples from the ten control horses were negative. These data show that a small dose of peg-epoetin β is detectable for 48 h by two different methods that are based on two different principles (chemiluminescence immunoassay and IEF–DB). The Immulite® assay is suitable as a screen and the IEF–DB assay as a confirmation method. These studies need to be expanded to other horses. The screen and confirmation tests, if applied, will probably eliminate the use of peg-epoetin β as a horse doping agent.

This study investigated intra-oral behaviours in horses wearing different bits with and without rein tension. Six riding horses wore a bridle and three bits: jointed snaffle, KK Ultra and Myler comfort snaffle. Lateral fluoroscopic images (30 Hz) were recorded for 20 s for each bit with loose reins and with 25 ± 5 N bilateral rein tension. The videos were analysed to determine time spent in the following behaviours: mouth quiet, gently mouthing the bit, retracting the tongue, bulging the dorsum of the tongue over the bit, lifting the bit and other behaviours that were performed infrequently. Repeated-measures ANOVA indicated that behaviours did not differ between bits, so bit type was not predictive of behaviour, but there were significant effects of horse and rein tension. Horses spent less time quiet and more time mouthing the bit, retracting the tongue and bulging the tongue over the bit when tension was applied.

An understanding of the physiological and metabolic demands of competition is essential for the development of training regimens that elicit adaptations appropriate for the sport being participated in. Despite the fact that dressage is a major sport and one of only three equestrian Olympic disciplines, to date there appear to be no studies that have described the heart rate of horses performing competitive dressage in any detail. The present study was therefore undertaken to describe the physiological demands of dressage competition. Thirty-five horses competing in a total of 50 dressage tests, 36 of which were at British dressage (BD) elementary level and 14 at BD medium level, were studied. The horses studied were predominantly Warmblood or Thoroughbred cross geldings with an age range from 6 to 17 (mean ± SD age of 10.0 ± 2.5 years). The average durations of warm-up for all horses competing were 31.3 ± 15.4 min at elementary level (n = 36) and 31.4 ± 10.0 min at medium level (n = 14; P>0.05). The mean and mean peak heart rates for horses warming up for elementary level were 91 ± 13 and 146 ± 35 bpm (beats min− 1), respectively, and were not different to that for horses warming up for medium level (mean 91 ± 10 bpm; peak: 144 ± 32 bpm; P>0.05). The mean and mean peak heart rates for all horses while competing at elementary level (n = 36) were 102 ± 13 and 132 ± 20 bpm, respectively, and 107 ± 8 and 132 ± 10 bpm, respectively, for medium level (n = 14), and were not significantly different (P>0.05). Mean heart rates during competition were significantly higher compared with that during warm-up for both elementary and medium levels (P < 0.001). Mean heart rate during competition (elementary and medium data combined) was significantly correlated with mean heart rate during warm-up (r2 = 0.503; n = 50; P < 0.001). There was no association between heart rate, warm-up duration and score or placing. These observations suggest that competitive dressage at BD elementary and medium levels is only moderately aerobically demanding.

The study was designed in order to gain a better understanding of whether the lack of competition stress and/or sampling time had an influence on circulating β-endorphin, adrenocorticotrophin (ACTH) and cortisol modifications after experimental showjumping sessions and to study the effects of fence height on hormone changes. Hormone levels were recorded before exercise in basal conditions and after warm-up, then 5 and 30 min post-exercise. Using a randomized crossover study design, six horses were studied during three experimental showjumping sessions over fences of different heights: 1.00 m (session 1), 1.10 m (session 2) and 1.20 m (session 3). The showjumping exercise did not modify plasma β-endorphin and serum ACTH concentrations after session 1, and tended only to maintain higher values than basal after both session 2 and session 3. The interaction fence height/time was not statistically significant for either β-endorphin or ACTH changes. Sampling time significantly affected both β-endorphin (F = 2.88; P < 0.04) and ACTH (F = 3.84; P < 0.01) changes. Serum cortisol levels were always higher than basal 5 min post-exercise, with levels falling at 30 min. The interaction fence height/time was not statistically significant, while sampling time significantly affected the results (F = 7.96; P < 0.0002). This study demonstrated no significant effects of fence height on β-endorphin, ACTH and cortisol changes. The sampling times adopted affected post-exercise changes in plasma β-endorphin, ACTH and cortisol and could have masked the effects of fence height on hormone modifications.

The objective was to characterize the endoscopic appearance of the glossoepiglottic fold (GEF) in normal horses. Six clinically normal adult Quarter Horses between 5 and 7 years of age were used and ranged from 480 to 520 kg body weight. Prior to oropharyngeal endoscopic examination, all horses had demonstrated normal function of the upper respiratory tract during high-speed treadmill examination. The horses were cantered at between 6.5 and 8.0 m s− 1 on a high-speed treadmill until fatigued and unable to maintain position on the treadmill. All horses were able to canter for at least 5 min. Oropharyngeal endoscopy was performed under intravenous general anaesthesia. The ventral aspect of the epiglottis and the GEF were examined with the aid of a specially designed epiglottic elevator. The endoscopic appearance of the oropharynx was documented using digital image capture technology Karl Storz AIDA™ Vet compact data archiving system (Karl Storz Veterinary Endoscopy America Inc., Goleta, CA, USA). In all horses, the GEF attached to the most caudo ventral aspect of the base of the epiglottis. The mucosa of the GEF was consistently plicated in the transverse plane, and in no horse, was there plication in the sagittal plane only. The clinical relevance included malformations of the GEF, which have been implicated in the etiopathogenesis of dorsal displacement of the soft palate. The results of this study may facilitate the differentiation of normal oropharyngeal anatomy from malformations (frenula) that may contribute to upper airway dysfunction.

This study investigates the relationship between Thoroughbred yearling sale price and race performance at the age of three. Sales details of all yearlings sold at Tattersalls October Yearling sales (Newmarket, UK) and Goffs Yearling sales (County Kildare, Ireland) in 2004 and 2005 were collected. End-of-year Timeform ratings were used to measure racetrack performance at the age of three. Yearlings that did not meet the study's criteria were excluded from the statistical analysis, reducing the sample size from 5749 to 1735. Comparisons between Tattersalls and Goffs were made for sale prices and end-of-year Timeform ratings. Tattersalls had a greater average sale price (56 787.51 guineas) than Goffs (52 680.49 guineas). Average end-of-year Timeform ratings were extremely similar for those yearlings sold from Tattersalls (78) and Goffs (77). A very highly significant correlation between LOG yearling sale price and end-of-year Timeform rating at the age of three (r = 0.363, n = 1735, P < 0.001) was established. Yearling sale price accounted for 13.3% of the variation in end-of-year Timeform ratings at the age of three (P < 0.01). A regression equation was formulated, allowing end-of-year Timeform rating at the age of three to be predicted from yearling sale price.

While temporal variable measurements have assisted in objectively defining and distinguishing between four-beat stepping gaits performed by gaited horses, kinematic research describing joint motion of the gaited horse is limited. The objective of this study was to measure the temporal variables and the forelimb kinematics of the flat walk and fox trot of the Missouri Fox Trotter (MFT) to provide a more comprehensive description of these gaits and to assist in distinguishing between them. Reflective markers placed along the lateral aspect of the right forelimb and the zygomatic process of the temporal bone were tracked at 60 Hz as eight MFTs were ridden at a flat walk and fox trot for ten strides. Student's paired t-tests were performed to compare means of analysed parameters between gaits on finding that the fox trot was a faster stepping gait (fox trot velocity: 3.17 ± 0.03 m s− 1, flat walk velocity: 1.75 ± 0.06 m s− 1) with a shorter stride duration (fox trot: 0.63 ± 0.03 s, flat walk: 1.17 ± 0.06 s) and greater stride frequency (fox trot: 1.59 ± 0.09 strides s− 1, flat walk: 0.09 ± 0.04 strides s− 1) than the flat walk (P < 0.05). Both gaits were performed with similar stride length (fox trot: 2.0 ± 0.03 m, flat walk: 1.95 ± 0.05 m), but the fox trot had an irregular rhythm with diagonal couplets (diagonal advanced placement: 0.10 ± 0.01 s, lateral advanced placement: 0.23 ± 0.02 s). Vertical head excursions, protraction/retraction angles and joint angle-time curves for the shoulder, elbow, carpus and forelimb fetlock were similar between gaits. Shoulder peak flexion of the fox trot occurred later in the stride (fox trot: 38 ± 5%, flat walk: 20 ± 3%; P < 0.05), but the timing of the other peak flexion and extension joint angles were similar between gaits. The fox trotting carpus flexed more (fox trot: 136 ± 3°, flat walk: 147 ± 4°) than the carpus of the flat walk (P < 0.05), but the other peak flexion and extension joint angles were comparable between gaits. Measured temporal and kinematic variables assisted in defining the fox trot and flat walk and differences between variables can be applied in distinguishing between the two gaits.

Exercise places an increased demand on the body's systems, both to provide fuel for working musculature and to neutralize and dispose of toxic build-up. By-products of demanding performance are reactive free radicals. Dietary consumption of vitamin E, an antioxidant, may be a plausible way to reduce free radical damage. The present study examined the effects of supplemental dietary vitamin E on the presence of oxidation products and antioxidant capacity in blood and tissue of exercising horses. Eight Thoroughbred horses were used in a crossover design study, with one group consuming a diet containing vitamin E at the 1989 National Research Council (NRC) level recommended for horses in moderate to intense work (80 IU kg DM− 1 [National Research Council (1989). Nutrient Requirements of Horses. 5th revised edn.; Washingto, DC: National Academy Press, pp. 48]), and the second group being fed the control diet plus 3000 IU day− 1dl-α-tocopheryl acetate. The horses underwent an adaptation phase, an 8-week training programme and a final standard exercise test (SET) during which the horses ran on a 6° incline to exhaustion, and then a washout phase. Horses were then crossed over to opposite treatment groups and these phases repeated. Blood samples were collected at specific points before and after exercise during the training period and before and after performing the SET. Neither plasma vitamin E nor thiobarbituric acid-reactive substance concentrations were influenced by supplemental vitamin E. Blood Trolox-equivalent antioxidant capacity values increased (P < 0.05) following 5 weeks of training in both groups, indicating improved antioxidant capacity as horses became fitter. Vitamin E supplementation did not alter plasma reduced, oxidized or total glutathione levels, nor the percentage of glutathione in the reduced form during the training period. However, vitamin E did cause an elevation in the percentage of glutathione existing in the reduced form following a SET as compared with the control diet (P < 0.006). This is possibly due to lower plasma oxidized glutathione levels in vitamin E-treated horses (P < 0.03). This study indicates that vitamin E supplementation above NRC levels can influence certain measures of oxidative stress in intensely exercising horses, and training has the ability to improve the antioxidant status of the animal.

Football players walk a fine line between optimal training and overtraining. Manipulating nutrient intake has the potential to maximize the biochemical environment necessary to induce peak performance and proper recovery. The purpose of this study was to examine the impact of supplementing the diet of Division I football players with a proprietary nutraceutical recovery drink on changes in performance, body composition, anabolic status, muscle damage, inflammation and oxidative stress over the course of a 7-week conditioning period immediately prior to preseason camp. At the beginning (trial 1) and end (trial 2) of a 7-week training phase, body composition, vertical jump and 225 lb bench press were assessed in Division I college football players (n = 25). A 30 s Wingate Anaerobic Test plus eight 10 s intervals was used to examine power and biochemical responses. Blood samples were collected pre-, 0 and 60 min post-test for analysis of interleukin-6 (IL), 8-isoprostane (8-iso), cortisol (CORT) and resting testosterone:CORT (T:C) ratios. Athletes were randomly assigned to either an experimental group (EXP) receiving the nutraceutical drink (n = 13) or a control group (CON) receiving an isocaloric equivalent (n = 12). EXP had a significantly greater increase in peak power (P < 0.05) and significant decreases in percentage body fat and fat mass (P < 0.05). Multivariate ANOVA for repeated measures (RM MANOVA) revealed a significant test × time × group interaction (P < 0.05) for changes in CORT, IL-6 and 8-iso from trial 1 to trial 2. Follow-ups revealed no significant differences between groups at trial 1 for any of the variables. At trial 2, EXP had significantly lower CORT at rest (P = 0.01) and 60 min post-test (P = 0.001). Additionally, IL-6 was significantly different between EXP and CON at 0 (P < 0.01) and 60 min post-test (P < 0.01), with CON having an elevated IL-6 response. There were also differences in both 8-iso and creatine kinase at all time points at trial 2, with CON having higher levels (P < 0.02.). There were significant differences between groups in T:C ratio changes (P < 0.05), with EXP having an improved T:C ratio. It appears that supplementing the post-workout diet of Division I college football players with a nutraceutical recovery drink has favourable effects on body composition, peak power output and biochemical markers. Based on differences between groups that emerged at rest at trial 2, it appears that this supplement positively impacts both acute and chronic physiological responses indicative of improved recovery.

Numerous studies have described the cardiorespiratory and kinematic responses of horses running on level and positive gradients, but little attention has been given to exercise on negative gradients, despite the fact that many horses compete over variable terrain. The purpose of this study was to describe the heart rate (HR), estimated net transport cost (COT) and stride characteristics of horses exercising at walk and trot on positive and negative gradients. Five horses (mean ± SD, 517 ± 42 kg) were acclimated in walk and trot on positive and negative gradients prior to data collection. HR and stride characteristics were measured over the last minute during walk (1.9 m s− 1) and trot (3.5 m s− 1) on a treadmill set at − 6, − 3, 0, 3 and 6%. Compared with level exercise, HR was higher at both 3 and 6%, and lower at − 3 and − 6% in walk and trot (P < 0.001). The estimated COT (beats kg− 1 m− 1 × 103) increased by an average of 30 and 48% at 3 and 6% gradient in walk, and by an average of 29 and 46% at trot compared with level exercise (P < 0.001), respectively. At negative gradients, COT decreased by 20 and 33% at walk, and by 17 and 24% at trot for − 3 and − 6% gradients (P < 0.001), respectively. Stride duration and stride length were longer, and stride frequency was lower at negative gradients compared with positive gradients (P < 0.001). In trot, the duty factor was increased in the forelimb and decreased in the hindlimb on negative compared with positive gradients (P < 0.001). Physiological workload in horses reduces from positive to negative gradients in walk and trot; however, the metabolic advantage of faster gaits, estimated by COT, diminishes as the gradient becomes more negative. This may reflect increased energy demands associated with maintaining balance and braking on negative slopes, and the locomotion strategy adopted.

This study hypothesized that ginger (Zingiber officinale) and cranberry (Vaccinium macrocarpon) extracts would alter the physiological response to exercise as well as markers of muscle damage, and mRNA expression for the inflammatory cytokines tumour necrosis factor-α (TNF-α), interferon-γ (IFN-γ) and interleukin-6 (IL-6) after an exhaustive bout of exercise in horses. Nine unfit Standardbred mares (age 10 ± 4 years, ~450 kg) completed three graded exercise tests (GXTs) in a crossover design, where they were assigned to the initial order of treatment in a randomized fashion. The GXTs were conducted between 07.00 and 12.00 hours, 7 days apart. Mares received either water (2 l), cranberry (~30 g in 2 l of water) or ginger (~30 g in 2 l of water) extract 1 h prior to testing. Blood samples were taken prior to dosing (pre-exercise), at the end of each step of the GXT, at the end of the exercise and at 2, 5 and 30 min, 1, 2, 4 and 24 h post-GXT. Plasma total protein (TP) concentration and haematocrit (HCT) were analysed immediately following the tests. Analysis of creatine kinase (CK) and aspartate aminotransferase (AST) was done commercially. There was no effect of treatment (P>0.05) on VO2max, run-time to fatigue, core temperature, TP or HCT. CK was substantially elevated (P < 0.05) in the ginger group at 4 h post-GXT. All CK levels returned to baseline 24 h post-GXT. No change (P>0.05) was noted in AST. A slight increase (P < 0.05) in CK was seen in all groups at 2 h post-GXT. The cranberry group had significantly lower TNF-α mRNA expression than the control and ginger groups. Ginger appeared to influence (P < 0.05) the upregulation and expression of IFN-γ mRNA at 30 min post-GXT, but, more strikingly, significantly decreased recovery time defined as the time for VO2 to recover from the peak observed at fatigue to a post-exercise plateau (ginger = 101 ± 3 s, water = 130 ± 14 s, cranberry = 131 ± 16 s). No effect of treatment or exercise (P>0.05) was seen on IL-6 mRNA expression. Results suggest that cranberry extract blunts the upregulation and expression of TNF-α mRNA, while ginger extract reduces cardiovascular recovery time in horses completing a short, exhaustive bout of exercise.

Fibre type composition of skeletal muscle in horses varies due to factors like breed, age and training. Variations due to these factors in muscle fibre type composition of the Swedish cold-blooded trotter, a heavier and slower breed than the Standardbred trotter, have not previously been reported. The objective of this study was therefore to investigate muscle fibre type composition of young and racing cold-blooded trotters using both histochemical and immunohistochemical methods. Muscle biopsies (gluteus medius) were obtained from 2-year-old (n = 18) and 4–8-year-old horses (n = 6). Four of the 2-year-old horses were sampled again during their 4-year-old season. All of the horses were in professional training and the group included superior racehorses. Fibre types (I, IIA and IIB) were visualized with the myosin ATPase technique. Some samples were also stained immunohistochemically to identify MHCI, MHCIIA and MHCIIX fibres using myosin heavy chain (MHC) antibodies. The oxidative capacity of the fibres was subjectively evaluated from NADH-tetrazolium reductase stains. Type I and type IIA fibres were all identified as MHCI and MHCIIA fibres, respectively, whereas type IIB fibre population included both pure MHCIIX and hybrid MHCIIAX fibres. The older racehorses had a higher proportion of type MHCIIA and a lower proportion of type MHCIIX fibres than the 2-year-old horses. Areas of type I fibres were larger and those of type IIB fibres were smaller in racing horses compared with young horses. The proportion of type MHCIIX fibres that stained medium for oxidative capacity increased with age and training. In conclusion, training and racing induce muscular adaptations in cold-blooded trotters as in other breeds. Furthermore, immunohistochemical methods detect hybrid fibres indicating that transitions of fibre types may occur.

The aim of this study was to investigate the effect of high-intensity training on lactate transporters (monocarboxylate transporters (MCTs)) in Thoroughbred horses. Five Thoroughbreds (three males and two geldings; 3–10 years old; 478 ± 13 kg) ran at 100% maximal oxygen uptake (VO2max) for 1 min (3 days per week, 3 weeks) or 2 min (2 days per week, 4 weeks) on a treadmill for 7 weeks. VO2max and ability to sustain an incremental all-out test of maximal running were measured, and muscle samples were obtained from the gluteus medius muscle at rest before and after the training. The performance in the all-out test and VO2max were increased after the training. The protein content of MCT1 and MCT4 in the gluteus medius muscles was not significantly altered. However, MCT1 showed a relationship with the duration of maximal exercise after the training. The changes in MCT4 showed a relationship with the increase in exercise duration by the training. These results suggest that in Thoroughbreds, although the overall changes in MCT protein after endurance training are small, MCT1 and MCT4 can play important roles in the capacity to sustain maximal exercise.

The purpose of this study was to test the hypothesis that the gastric ulcer medications, ranitidine and omeprazole, would alter plasma concentrations of total carbon dioxide (tCO2), lactate (LA), Na+, K+, Cl−  and total protein (TP), as well as calculated plasma strong ion difference (SID) and packed cell volume (PCV) in horses subjected to a simulated race test (SRT). Twelve unfit Standardbred mares (~520 kg, 9–18 years) were used in a randomized crossover design with the investigators blind to the treatment given. Each mare received a treatment three times daily (TID) at 06.30, 12.30 and 18.30 hours. The treatments administered orally were omeprazole (4 mg kg− 1 was given in the morning with apple sauce given at the later, two dosing times to encourage good behaviour), ranitidine (6 mg kg− 1 crushed and mixed in 20 ml apple sauce) and control (20 ml apple sauce TID). Each horse completed a series of SRTs with blood samples taken via jugular venipuncture at five intervals (prior to receiving treatment, prior to SRT, immediately following exercise and at 60 and 90 min post-SRT). During the SRTs, each horse ran on a treadmill fixed on a 6% grade for 2 min at a warm-up speed (4 m s− 1) and then for 2 min at a velocity predetermined to produce VO2max. Each horse then walked at 4 m s− 1 for 2 min to complete the SRT. Plasma tCO2, electrolytes, LA and TP concentrations and PCV–TP were measured in duplicate at all intervals. No differences (P>0.05) were detected between control, ranitidine or omeprazole for any of the measured variables. There were differences (P < 0.05) in tCO2, SID, PCV, TP, LA and electrolyte concentrations relative to sampling time. However, these differences were attributable to the physiological pressures associated with acute exercise and not an effect of the medication. It was concluded that ranitidine or omeprazole did not alter plasma tCO2 concentration.

Studies investigating the role of oxidative stress in both the ageing process and osteoarthritis (OA) in human beings are limited by the unavailability of samples from healthy subjects. OA occurs naturally in the horse and has been used as a model of human OA. The objective of this study was to determine the effect of ageing and OA on the non-enzymatic synovial fluid antioxidant status of the horse. The concentrations of ascorbic acid, dehydroascorbate (DHA, oxidized ascorbic acid), uric acid, glutathione, α-tocopherol and thiobarbituric acid reactive substances (TBARS) were determined in paired synovial fluid and plasma samples from 25 horses aged between 3 and 25 years. Osteoarthritic lesions were scored from 0 (healthy) to 4 (severe OA). Glutathione was not detectable in synovial fluid. Neither plasma nor synovial fluid antioxidant concentrations were affected by age. Ascorbic acid concentrations in plasma correlated strongly with those in synovial fluid from both healthy (P < 0.001) and diseased joints (P = 0.003). Synovial fluid concentrations of ascorbic acid and uric acid were not influenced by OA compared with healthy joints. However, the concentration of DHA was slightly, but significantly, elevated in synovial fluid from joints with severe OA (95% CI: [2.2, 11.8] μmol l− 1; P < 0.001). OA is associated with only a mild oxidative burden, which does not appear to overwhelm the synovial fluid antioxidant capacity. Consequently, antioxidant supplementation is unlikely to have a beneficial effect in the treatment of OA.

Obesity is considered a risk factor for laminitis, insulin resistance and other medical problems in horses. The objective of this study was to test the hypothesis that a feeding and exercise programme would induce weight loss and affect indices of health in overweight horses. Twenty-three overweight (BCS 6.5–9.0) QH and TB horses were assigned to three groups: calorie restriction (DIET), calorie restriction plus exercise (DIETX) and a control group at weight maintenance (CON). Measurements included body weight, body condition score, rump fat thickness, glucose, insulin, leptin, non-esterified fatty acids (NEFA) and triglycerides. Frequently sampled intravenous glucose tolerance tests measured insulin sensitivity (SI), glucose effectiveness and acute insulin response to glucose (AIRg). Disposition index (DI) was calculated. DIETX underwent a fitness test (graded exercise test) on a treadmill before and after the experimental period, and performed a standardized submaximal exercise regimen in an Equi-ciser™. Horses in the DIETX group lost more weight (P < 0.01) than DIET or CON. DIET also lost more weight versus CON (P < 0.05). All groups had decreases (P < 0.05) in BCS, with DIETX and DIET exhibiting the largest decreases. DIET and DIETX decreased (P < 0.05) in rump fat thickness. Cortisol decreased (P < 0.05) in DIET, and NEFA decreased in DIETX pre- versus post-weight loss. There were decreases (P < 0.05) in leptin and AIRg in DIET and DIETX pre- versus post-weight loss. DI was decreased (P < 0.05) in DIET and CON. SI was decreased (P < 0.05) only in CON. Calorie restriction and calorie restriction plus exercise programmes were successful in achieving weight loss in overweight horses. Indices of obesity, physiological stress and fat metabolism can be significantly altered with calorie control and exercise.