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.

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.

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.

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.

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.

Few studies exist regarding the physiological responses of equestrian riders during actual or simulated competition. Interest has proliferated in recent years on the responses of riders, which is mainly due to the fatal tragedies that occurred in eventing in the late 1990s. More emphasis is also being placed on the importance of riders, fitness in order to improve athletic performance at the international level. The aim of the present study was to investigate the fitness and exercise capacity of female equestrian athletes, and to relate this to the metabolic requirements of dressage (DR), showjumping (SJ) and cross-country (XC) phases of the one-day event. Sixteen female collegiate riders (age = 24.5 ± 7.7 years; height = 166.6 ± 3.8 cm; weight = 60.4 ± 6.0 kg) competed in a simulated Horse Trials Pre-Novice competition riding either their own horse or one familiar to them. Anthropometric data were obtained for each rider (body mass index (BMI) = 21.7 ± 1.9; % body fat (BF) = 23.4 ± 5.3; lean body mass (LBM) = 48.5 ± 3.6). Each subject successfully completed all three phases of the event. There was a progressive increase in oxygen consumption (VO2) during the three phases (DR, SJ and XC) from a mean value of 20.4 ± 4.0 ml kg− 1 min− 1 (DR), 28.1 ± 4.2 ml kg− 1 min− 1 (SJ) to 31.2 ± 6.6 ml kg− 1 min− 1 (XC) (P < 0.001). Heart rate data showed a similar trend from a mean value of 157 ± 15 beats min− 1 (DR), 180 ± 11 beats min− 1 (SJ) to 184 ± 11 beats min− 1 (XC) (P < 0.001). Mean lactate concentration increased progressively from resting values: rest 2.5 ± 1.3 mmol, DR 4.8 ± 1.8 mmol, SJ 7.8 ± 2.4 mmol and XC 9.5 ± 2.7 mmol (P < 0.001). Urine osmolality was significantly (P < 0.001) increased from a pre-competition mean of 0.488 ± 0.270 mOsmol l− 1 to a post-competition mean of 0.684 ± 0.230 mOsmol l− 1. Mean hand grip strength was observed to decrease significantly (P < 0.01) from a pre-value of 32.3 ± 6.3 kg to a post-value of 29.8 ± 5.5 kg. Mean weight loss pre- to post-competition was 1.6 ± 1.1% body weight (P < 0.01). In conclusion, the study emphasises the variability in metabolic cost between riders performing in the same simulated competition but riding different horses, and highlights the difference in metabolic demand between the different phases.