Acupuncture Needle Stimulation on Some Physiological Parameters After Road Transport and Physical Exercise in Horse

The aim of this study was to evaluate the effect of acupuncture (AG) treatment on some hematochemical parameters in five Thoroughbred horses after road transport and exercise. Horses competed in two official races. For each race, animals were transported from their stables to the racetrack. Horses transported and competed in the first race represent the control group. Two weeks later, the same horses competed in the second race. Before road transport, they were treated with AG. From animals, blood samples were collected at rest (T_PRE), after unloaded (T_POST), 30 minutes after unloaded (T_POST30), at rest in the transit stall (R_PRE), at the end of the race (R_POST), and 30 minutes after the race (R_POST30). The effect of transport, exercise, and AG was evaluated on blood lactate, glucose, red blood cell, hemoglobin, hematocrit, mean corpuscular volume, and erythrocyte osmotic fragility (EOF) values. A significant effect of transport (P < .05) and exercise (P < .01) was found on all studied parameters in both groups. A significant effect of AG on lactate, glucose, and EOF values was found in transported (P < .001) and exercised horses (P < .05). The results found in this study showed that transport and exercise are potential stressors for the athlete horse that may affect its welfare and physical performance. The data suggest that AG stimulation promoted the increase of blood glucose values and the reduction of lactate and EOF levels suggesting its role in the improvement of the physiological adaptation to stressful stimuli and of physical performance of Thoroughbred horses.     

Training Program Intensity Induces an Acute Phase Response in Clinically Healthy Horses

Physiological and hematochemical changes associated with exercise have been extensively investigated in equine species. It is known that stress elevates circulating levels of acute phase proteins (APPs). This survey evaluated whether horses trained with different training programs exhibit changes in APP levels after exercise event. Twenty Saddle Italian horses (11 geldings and 9 females, 9 ± 1 years old, body weight of 425 ± 35 kg) were divided into two equal groups according to the intensity of training programs they were subjected: group A was subjected to an intense training program, group B was subjected to a moderate training program. At the end of the training period, horses were subjected to a simulated exercise event (show jumping course of 400 m length with 12 obstacles). From horses, blood samples were collected at rest conditions (T_REST) and after 12 and 24 hour from the end of exercise (T_{12 h} and T_{24 h}); the concentration of serum amyloid A (SAA), haptoglobin, albumin, total proteins, iron, and fibrinogen was assessed. The circulating levels of SAA, fibrinogen, and iron were influenced by simulated exercise event (P < .01), starting from 12 hour after the end of exercise, suggesting the onset of an acute phase–like response, and it would seem that training program intensity the horses underwent also affected the degree of response, although only SAA values were significantly different between groups (P < .001). The findings obtained suggest that jumping exercise induces an acute phase response; however, further studies are advocated to better evaluate mechanisms by which exercise activates this response in the athletic horse.     

Changes of Circulating Total and Free Iodothyronine in Horses After Competitive Show Jumping With Different Fence Height

The effect of exercise on circulating T₃, T_4, free (f) T₃, and fT₄ concentrations were studied before and after competitive show jumping in 24 trained jumper horses with an age range of 11–13 years and having the same level of show experience. All horses, randomly divided into three groups paired by gender, participated in three competition levels with the same circuit design over 10 fences, with five upright and five cross-pole fences .The three fence height groups were group I (n = 8), 1.10 m; group II (n = 8), 1.20 m; and group III (n = 8), 1.30 m. Repeated measures analysis of variance showed a statistically significant effect of competitive exercise on fT₃ changes in all groups, whereas the effect of competitive exercise on T₃ changes was exclusively seen in group III. Two-way repeated measures analysis of variance showed that the effect of fence height (P = .0002) and performance results were significant (P = .0486) only for T₃ changes. Performance also affected fT₃ changes (P = .0152). No significant correlation was found between total and free iodothyronines. These results suggest a dependence of T₃ and fT₃ changes on exercise-related variables and performance results and that the thyroid response is different with respect to the different exercise-related variables, such as the varying level of difficulty and performance results.     

Effects of Intravenous Detomidine on Intraocular Pressure Readings Obtained by Applanation Tonometry in Clinically Normal Horses

This study was conducted to determine effects of intravenous detomidine on intraocular pressure (IOP) readings obtained by applanation tonometry in clinically normal horses. Twenty horses were randomly divided into two groups of 10 each (treatment and control). All horses in the treatment group received intravenous detomidine alone (20 μg/kg). The horses in the control group received only intravenous saline (0.2 mL/100 kg). The IOP values were measured before the treatment (T₀) and then at 5 (T₅), 20 (T₂₀), 60 (T₆₀), and 120 (T₁₂₀) minutes after drug administration in both groups. A significant decrease in IOP values was observed in both right and left eyes of the horses in the treatment group at T₅, T₂₀, and T₆₀ in comparison with the baseline values (P < .001). The observed decrease was only statistically significant in the right eyes of the treatment group horses at T₁₂₀ (P = .044). Mean IOP was not significantly altered at any time point during the treatment period compared with the baseline evaluations in both eyes of the horses in the control group. This study demonstrates that the use of intravenous detomidine lowers IOP quickly.     

Effect of Experience on Adrenocortical and Thyroid Responses of Arabian Horses to Gymkhana Games

Gymkhana is an equestrian event consisting of speed pattern racing and timed games for riders on horses. The aim of the study was to evaluate the effects of gymkhana competition on total cortisol and total and free iodothyronine changes in 23 Arabian purebred horses, by taking into account the effects of previous sport experience on gymkhana riding events. Compared with pre-competition values, an increase of total cortisol concentration has been observed in experienced horses at 30 minutes (P < .001) after exercise and in inexperienced horses both at 5 minutes (P < .05) and at 30 minutes (P < .01) after exercise. Compared with pre-competition values, an increase of total triiodothyronine (T₃) concentration has been observed in experienced horses at 5 minutes (P < .05) after exercise. Data obtained showed that gymkhana riding events induced differential adrenocortical and thyroid responsiveness according to previous experience of sport horses. Hence, cortisol and iodothyronine patterns may provide additional information for the monitoring of gymkhana riding performance.     

Metabolic parameters and their relationship to energy balance in multiparous Simmental,Brown Swiss and Holstein cows in the periparturient period as influenced by energy supply pre‐ and post‐calving

A study was conducted to evaluate the effects of three energy supply (E) levels [low (L), medium (M), high (H)], both pre‐partum (PRE) and post‐partum (POST), and their interactions on metabolic parameters and energy balance (EB) in dairy cows of three breeds. In both phases, E levels applied to a total of 81 multiparous cows of breeds Simmental (SI), Brown Swiss (BS) and Holstein–Friesian (HF; n = 27 for each breed) were 75%, 100% and 125% of recommendations of the German Society of Nutrition Physiology, using a 3 × 3 factorial arrangement of treatments. During the pre‐calving period, serum concentrations of non‐esterified fatty acids (NEFA) were higher for L_PRE cows, and glucose concentrations were elevated for H_PRE cows. During the lactation period, NEFA concentrations were greatest for treatment L_POST. Mean concentrations of β‐hydroxybutyrate (BHB) were highest for cows of the L_POST treatment, intermediate for M_POST and lowest for H_POST. Glucose concentrations were lower for L_POST cows. SI cows had lower BHB concentrations both pre‐ and post‐calving and higher glucose concentrations during early lactation than the other breeds. BHB concentration POST was highest for BS cows. Restricted feeding PRE resulted in a better energy status of cows fed above energy requirements POST (E_PRE × E_POST interaction). HF cows had a higher EB pre‐calving, whereas SI cows had a less negative EB during early lactation, compared with the other breeds respectively. Correlations of serum NEFA, BHB and glucose concentrations with EB were strongest during the transition period. Results suggest that controlling energy intake during the dry period might be advantageous for the energy status of dairy cows after calving, whereas energy restriction in early lactation leads to metabolic stress. Evidence is provided of a clear relationship between EB and the blood metabolites NEFA and BHB, especially in the transition period.     

Tall fescue utilization by exercised - yearling horses

Little information has been published concerning the effects of endophyte-infected tall fescue consumption on performance of young growing horses. Therefore, this study evaluated exercise performance and growth by yearlings fed endophyte-infected fescue. Twelve Quarter Horse yearlings (12-16 months of age) were blocked by age and sex and randomly assigned to one of three groups. Group I received native prairie hay (P), Group II received endophyte-free fescue hay (EF) and, Group III received endophyte infected fescue hay (EI). Rectal temperatures were monitored daily and growth parameters (weight, hip and wither heights, and body fat) were measured at the start of the study (d 0) and every 2 weeks throughout the 106 d study. Additionally, blood samples were collected on d 0 and every 28 d for the duration of the study to monitor blood concentrations of calcium, phosphorus, prolactin (PRL), thyroxine (T₄), and triiodothyronine (T₃). Horses were exercised twice a week for 10-30 min. Respiration, heart rate, and rectal temperature were measured at the start and 5, 30, and 60 min postexercise. Growth parameters and daily rectal temperatures were not different (P >.05) among grdups. No differences (P >.05) occurred among groups in concentrations of serum calcium, phosphorus, PRL, T₃, and T₄. Respiration rates were lower (P <.05) at 30 and 60 rain postexercise for horses consuming fescue than for horses consuming prairie hay. Postexercise heart rates and rectal temperatures showed no difference (P <.05) among groups. These data suggest that young growing horses being exercised can utilize endophyte-infected fescue efficiently on a short-term basis.     

Copper,Zinc-Superoxide Dismutase Activity in Exercising Horses Fed Two Forms of Trace Mineral Supplements

Nine mature horses were used to evaluate superoxide dismutase (SOD) response to a low-intensity standard exercise test and the effect of copper (Cu) and zinc (Zn) supplement form on enzyme activity. The modified switchback experiment was conducted over seven 28-day periods. Horses were conditioned to perform an average daily workload of 3.93 kg∗km∗10⁻³ with a digestible energy (DE) demand of approximately 29 Mcal. Following a controlled Cu and Zn repletion-depletion diet sequence, horses were fed a diet intended to be marginally deficient in Cu and Zn with the minerals supplemented in either sulfate or organic chelate forms. Horses were then subjected to a standardized exercise test to enable evaluation of SOD activity during exercise and immediate recovery. In the final analyses, mineral contents of the experimental diets were significantly different (P < .05). The mean mineral concentration of the sulfate diet was 6.28 ppm Cu and 35.99 ppm Zn, while the chelate diet contained 23.62 ppm Cu and 90.67 ppm Zn. Even so, resting SOD activity was not altered by diet (1793.47 ± 323.00 U/g Hb for the sulfate diet, 1355.70 ± 148.32 U/g Hb for the organic-chelate diet), nor did SOD activity change in response to the low-intensity workout. The SOD activity was unchanged by feeding a Cu and Zn supplemented diet to horses fed to be in a mineral-deficient state. These exercise bouts did not appear to have a significant impact on SOD activity. Other types of oxidative stress should be considered when trying to evaluate the antioxidant responsiveness of this enzyme.     

Feeding practice and influence on selected blood parameters in show jumping horses competing in Switzerland

The aim of this study was to compare the nutritional management of show jumping horses in practice with recommendations from the literature. Additionally, the effects of these feeding practices on several blood metabolic parameters before and after exercise were studied. Blood samples were collected in the field from 27 different horses at 71 trials on the level M1 to S2 show jumping competitions in Switzerland and questionnaires on feeding practice of the studied horses were evaluated. The questionnaires revealed that during training and on tournament days horses received on average 3.1 kg of concentrate per day (min. 2.0 kg, max. 6.6 kg) divided into two to three meals. The horses were fed on average 6.9 kg of roughage per day (min. 4.0 kg, max. 13.0 kg). Additionally, it was observed that the horses received the last meal on average 6 h 10 min (min. 1 h 50 min, max. 12 h 30 min) before the start of the first show jumping turn, respectively, 7 h 30 min (min 1 h 50 min, max. 13 h 0 min) before the second turn. Seven horses (35%) had access to hay waiting in the trailer between two turns. The statistical analysis revealed no significant influence of the concentrate feeding time point on lactate, triglyceride and insulin levels, but a significant influence on free fatty acids (FFA) and blood glucose concentrations. Roughage feeding of the show jumping horses 2–4 h prior to exercise revealed the most remarkable changes in blood parameters during the show jumping course. These results received under field conditions should be approved in future under standardized conditions.     

Relationship between serum cortisol levels and some physiological parameters following reining training session in horse

The changes of cortisol, red blood cells (RBC), hemoglobin (Hb), hematocrit (Hct), heart rate (HR), respiratory rate (RR) and rectal temperature (RT) were evaluated after a reining training session in eight Quarter Horses. All parameters were measured before exercise (T0), immediately after exercise (T1), 1 h after exercise (T2), 2 h after exercise (T3) and 24 h after exercise (T4). One‐way analysis of variance (ANOVA) for repeated measures, followed Bonferroni's post hoc test, showed a significant effect of the reining training session (P < 0.0001) on cortisol, RBC, Hb, Hct, HR, RR and RT. Simple linear regression analysis showed the positive correlation (P < 0.05) between cortisol changes and variations of studied parameters in T1, T3 and T4. Exercise‐induced cortisol concentrations reflect the physiological response of reining training, suggesting that the changes observed are useful to assess the performance in reining horses and their reining training adaptability.     

Effect of Recovery Periods during Conditioning of Horses on Fitness Parameters

The effect of recovery from training has not been studied in horses. Therefore, the effect of recovery was examined with exercise of known effect within a conditioning period (CP). A standardized exercise test was performed at the beginning of CP to determine v₄, v₁₀, and v₁₈₀ (horse’s speed, which produced a blood lactate concentration of 4 and 10 mmol/L and a heart rate of 180 beats/min). Six horses were conditioned for three periods of 2 weeks, 5 times per fortnight at their individual v₁₀ for two bouts of 5 minutes on a treadmill. Every 2 weeks of conditioning was followed by 1 week with reduced workload. Standardized exercise test was repeated after each 2 weeks of conditioning and 2 weeks after finishing CP. Exercise speed was individually adapted to the new v₁₀ for every 2 weeks of conditioning. In addition, peak oxygen consumption before, after 3 weeks of conditioning, and at the end of the CP was measured. The mean v₄ increased steadily during CP. v₁₈₀ did not change, whereas peak oxygen consumption increased between the beginning and after 3 weeks of conditioning and leveled off thereafter. In conclusion, reducing the workload for 1 week after 2 weeks of conditioning 5 times per fortnight at v₁₀ for two bouts of 5 minutes allowed for a continuous increase of v₄, but the extent of the increase was smaller than in another study with a similar conditioning program but for the recovery week. The effect of recovery from training needs further studies.     

Normal electrocardiographic QT interval in race-fit Standardbred horses at rest and its rate dependence during exercise

ObjectivesCardiac repolarization, measured as QT and T_peak to T_end (T_pT_e) intervals on the ECG, is important, as irregularities caused by diseases, ventricular hypertrophy, drugs and genetic defects can trigger arrhythmias which predispose human patients to syncope and sudden cardiac death. In horses, repolarization is not well described and therefore QT analysis cannot yet be used diagnostically. Therefore, we sought to describe reference values for the normal QT and T_pT_e intervals in Standardbreds and to determine the best method for heart rate (HR) correction.Animals30 Standardbreds.MethodsQT and T_pT_e intervals were measured during rest and exercise and plotted against HR converted to R_peak to R_peak interval (RR). Data were fitted with relevant regression models. Intra- and inter-observer agreement was assessed using Bland–Altman analyses.ResultsData were best described by a piecewise linear model (r² > 0.97). Average prediction error of this model was smaller than for both Bazett and Fridericia corrections. Coefficient of repeatability of intra- and inter-observer variability was 8.76 ms and 5.64 ms respectively and coefficient of variation was 1.77% and 2.76% respectively. T_pT_e increased with RR in stallions.ConclusionsThe QT interval in Standardbred horses shortens with decreasing RR interval (increasing HR) as in humans, but in a markedly different order as it clearly follows a piecewise linear model. The equine QT interval can be measured easily and there is small intra- and inter-observer variability. This model of the equine QT interval provides clinicians with a method that could support a diagnosis of repolarization disturbances in horses.     

Relative Flow-Time Relationships in Single Breaths Recorded After Treadmill Exercise in Thoroughbred Horses

Analysis of individual breaths after exercise has potential for pulmonary function testing. The aims of this study were to investigate the dependence of measurements of pulmonary function in single breaths on time postexercise and tidal volume (V_T) after treadmill exercise. Five Thoroughbred horses without evidence of airway disease were used. Horses had been previously acclimated to treadmill exercise and to wearing a face mask. A Quadflow spirometer recorded airflow rates continuously during 90 seconds after intense treadmill exercise to fatigue. Indices of function were based on ratios of times within each breath and analyses of the shape of relative flow–time curves within inspiration and expiration. Restricted maximum likelihood, general linear regression, repeated-measures one-way analysis of variance (ANOVA), and two sample t-tests were used, with statistical significance at P < .05. Time postexercise had no effect on several ratios based on time for inspiration (T_I) and expiration (T_E), and times to peak flows (T_I/T_T, T_E/T_T, T_E/T_I, Tpef [peak expiratory flow]/T_E, and Tpif [peak inspiratory flow]/T_I). Many variables were significantly dependent on V_T. Occasional big respiratory cycles with V_T more than 10% greater than in the previous breath had significantly different means for relative flow (Rf)/(T_E/T_I), epz_50% (50% of the time from Tpef to end of expiration), epz_75% (75% of the time from Tpef to end of expiration), and ipz_75% (75% of the time from Tpif to end of inspiration). Predicted means for these variables differed by 10–20%. This study establishes guidelines for the selection of breaths after exercise, and describes a new approach to measurement of relative flow and time relationships. It was concluded that several time-based ratios have potential for measuring pulmonary function. However, care is needed when selecting breaths for calculation of most of the new relative flow–time variables.     

Hypoventilation following oxygen administration associated with alfaxalone–dexmedetomidine–midazolam anesthesia in New Zealand White rabbits

ObjectiveTo investigate the relationship between oxygen administration and ventilation in rabbits administered intramuscular alfaxalone–dexmedetomidine–midazolam.Study designProspective, randomized, blinded study.AnimalsA total of 25 New Zealand White rabbits, weighing 3.1–5.9 kg and aged 1 year.MethodsRabbits were anesthetized with intramuscular alfaxalone (4 mg kg^–1), dexmedetomidine (0.1 mg kg^–1) and midazolam (0.2 mg kg^–1) and randomized to wait 5 (n = 8) or 10 (n = 8) minutes between drug injection and oxygen (100%) administration (facemask, 1 L minute^–1). A control group (n = 9) was administered medical air 10 minutes after drug injection. Immediately before (PRE_oxy/air5/10) and 2 minutes after oxygen or medical air (POST_oxy/air5/10), respiratory rate (f_R), pH, PaCO₂, PaO₂, bicarbonate and base excess were recorded by an investigator blinded to treatment allocation. Data [median (range)] were analyzed with Wilcoxon, Mann–Whitney U and Kruskal–Wallis tests and p < 0.05 considered significant.ResultsHypoxemia (PaO₂ < 88 mmHg, 11.7 kPa) was observed at all PRE times: PRE_oxy5 [71 (61–81) mmHg, 9.5 (8.1–10.8) kPa], PRE_oxy10 [58 (36–80) mmHg, 7.7 (4.8–10.7) kPa] and PRE_air10 [48 (32–64) mmHg, 6.4 (4.3–8.5) kPa]. Hypoxemia persisted when breathing air: POST_air10 [49 (33–66) mmHg, 6.5 (4.4–8.8) kPa]. Oxygen administration corrected hypoxemia but was associated with decreased f_R (>70%; p = 0.016, both groups) and hypercapnia (p = 0.016, both groups). Two rabbits (one per oxygen treatment group) were apneic (no thoracic movements for 2.0–2.5 minutes) following oxygen administration. f_R was unchanged when breathing air (p = 0.5). PaCO₂ was higher when breathing oxygen than air (p < 0.001).Conclusions and clinical relevanceEarly oxygen administration resolved anesthesia-induced hypoxemia; however, f_R decreased and PaCO₂ increased indicating that hypoxemic respiratory drive is an important contributor to ventilation using the studied drug combination.     

Change in Some Physiologic Variables Induced by Italian Traditional Conditioning in Standardbred Yearling

The goal of this study was to quantify the effect of a traditional Italian conditioning method (CM). Six Standardbred yearlings were kept in standardized conditions for 140 days. From T1 (day 1) to T10 (day 10), the horses were hitched for 30 minutes/day to accustom them to a cart. From T11 to T70, they were jogged or exercised for 30 minutes/day at a slow trot (4.4 ± 0.3 m/second) and from T71 to T140 for 40 minutes/day (5 m/second ± 0.3 m/second). Every 15 days, the horses performed fast exercise for a distance of 5,000 m with increased speeds. Blood samples were collected before and after daily training (DT) every 21 days (P1…P7), to measure the following variables: erythrocytes (RBC), hemoglobin (Hb), packed cell volume (PCV), mean corpuscular hemoglobin concentration (MCHC), mean corpuscular hemoglobin (MCH), mean corpuscular volume (MCV), total protein (Pt), albumin, aspartate amino transferase (AST), alkaline phosphatase (ALP), creatine kinase (CK), lactate dehydrogenase (LDH), urea, creatinine, glucose, triglycerides, and blood lactate. A three-step standardized exercise test (SET) also was performed. Analysis of variance was used to study differences during the training. Tukey's post-hoc test was used for statistical multiple comparison (P ≤ 0.05 and 0.01). Lactate level did not show an increase over 4 mmol/L in all periods. Glucose was higher at P1 than P7. There was no correlation between method of conditioning and the level of CK, LDH, or AST. Conditioning method induced an increase in triglycerides for the change in exercise metabolism supply. According to SET, conditioning method induced an increase of SVO2_max (speed [m/second] reached to a theoretical maximal oxygen consumption), V₄ (speed [m/second] reached at a lactate content of 4 mmol/L), V₂₀₀ (speed [m/second] at 200 beats/minute) and HR₄ (heart rate [beats/minute] at 4 mmol/L of lactate). We concluded that the Italian conditioning method used in this study improved the fitness of horses.     

A prospective study on fitness,workload and reasons for premature training ends and temporary training breaks in two groups of riding horses

Little is known about wastage in riding horses and the factors like fitness and workload that may reduce injuries and maximise welfare. To evaluate fitness, workload and reasons for premature training ends (PTEs) and temporary training breaks (TTBs) during a nine week training period, two groups of riding horses were used: Group A consisting of 58 horses used for student equitation courses (32 with training prior to admission and 26 without) and Group B consisting of 26 horses owned by two riding schools (school-I and school-II). To assess fitness, all horses performed a standardised exercise test (SET) at the start (SET-I) and end of the training period (SET-II) measuring heart rate (HR bpm) and speed (m/s). In addition, all horses were monitored daily during the training period for their health and workload.In Group A, trained horses had significantly lower HRs in SET-I (P = 0.05) compared to untrained horses and in SET-II, trained horses tended to have lower HRs than untrained horses, though this was not statistically significant (P = 0.057). During the training period all horses received an identical workload. A total of 19.0% of Group A horses ended the training period prematurely for veterinary reasons (PTEV); of those untrained horses had earlier a PTEV in the training period (after 2.8 ± 1.3 weeks) than trained horses (after 4.1 ± 1.5 weeks, P = 0.030).In Group B, school-I and school-II horses did not differ significantly in fitness level nor in workload. More school-II horses ended the training period prematurely for veterinary reasons (n = 7; 70%) compared to school-I horses (n = 4; 25%, P = 0.032), although seven (63.6%) of these horses were still continuously used in riding lessons. In both groups (A and B), small injuries (without a temporary training break) were significantly associated with premature training ends for veterinary reasons later on: in Group A small injuries preceded 27.3% of the PTEVs (P = 0.005) and in Group B small injuries preceded 54.5% of the PTEVs (P = 0.030).In conclusion, as all horses in each subgroup had the same workload, the occurrence of PTEV seemed not associated with the workload. In Group A horses, level of fitness seems to be an important factor for the point in time injuries will occur during the training period. In all horses, injuries were more likely when a temporary training break was not taken following seemingly minor injuries. Since a lot of injured Group B horses were used in riding lessons against veterinary advice, this may indicate that riding school owners have different perception on welfare and if true this may cause serious welfare problems.     

Influence of Acute Exercise on Serum Homocysteine in Horse

The effect of acute exercise on serum homocysteine (sHCy) concentration was examined in 10 horses; five Sella Italiana and five Thoroughbreds. All horses underwent standard training before the study (show jumping for Sella Italiana horses and gallop racing for Thoroughbreds). For the study, blood samples were taken at rest, immediately after exercise, and during a recovery period (30 and 60 minutes after exercise) by external jugular venipuncture. sHCy values were determined by high-performance liquid chromatography. Heart rate and blood lactate were monitored to quantify the workloads. In show jumpers, there was a significant effect of sampling time on sHCy (P < .01), which increased significantly after exercise as compared with at rest. In Thoroughbreds, no statistically significant differences were observed in sHCy over time (F_(3,12) = 0.89, P = .05). The baseline values of sHcy were higher in Thoroughbreds than in show jumpers (P < .0002). We infer that physical activity causes biochemical changes that can influence the metabolic pathway of homocysteine in show jumpers, whereas the absence of a significant effect of exercise in Thoroughbreds may reflect an adaptive response of the enzymatic antioxidant defense system.     

To jump or not to jump? Strategies employed by leisure and sport horses

Show jumping is one of the most popular equestrian disciplines although strategic jumping per se is seldom used by free-living horses when negotiating obstacles that they might otherwise avoid. To establish if horses are naturally motivated to jump, we examined horses in a free-choice situation when negotiating various obstacles under test conditions. Eighteen leisure horses (LHs) and 16 sport horses (SHs) participated in a number of 2-choice tests. First, horses were presented with 2 optional routes during a “free-choice test” to reach a food stimulus. The choices were a shorter route (over an obstacle) or a longer route (around the obstacle). During 8 consecutive trials, the horses encountered an increase in obstacle height on every second trial as follows: 0, 20, 35, and 50 cm. In the “ridden test” after an initial conditioning period, the horses were tested with a Y-maze formation during 3 consecutive trials, where one element of the maze contained an obstacle arm (OA). The horses walked or trotted over the obstacle most frequently (59.9%) and jumped the obstacle in only 10.7% of the cases. For both the LH and SH groups, the horses' motivation to traverse the obstacle decreased as the obstacle height increased and only 44.1% of horses actually negotiated the 50-cm obstacle as compared with the 20-cm obstacle (85.3%). The LH group preferred to go around the obstacle significantly more often than the SH group (24 trials, 16.7% vs. 9 trials, 7.0%, for SH and LH, respectively; χ² = 6.81, N = 33, P = 0.0090). The LH group used a jumping strategy to clear the obstacle far less frequently (6 trials, 4.2%) than the SH group (23 trials, 18.0%; χ² = 9.96, N = 29, P = 0.0023). In the Y-maze trials, the LH group exhibited preference (40 per 54 trials, 74.1%; χ² = 12.5, P < 0.0001), and the SH group failed to exhibit any preference (20 per 48 trials; χ² = 1.33, P = 0.3123). There was no evidence of any correlation between the motivation to clear the obstacle and total number of OA choices in either the LH group (r_s = 0.13, P = 0.9594) or the SH group (r_s = ?0.25, P = 0.3492). The findings from the present study indicate that SHs are motivated and willing to jump obstacles more often than are LHs under similar conditions. However, the apparent reluctance of the horses overall to continue jumping as the obstacle height increases suggests that, in general, many horses could easily encounter excessive demands (overfacing) in sport. This issue should be carefully monitored in terms of equine training, competition, and welfare.     

Peripheral serotoninergic response to physical exercise in athletic horses

The purpose of this study was to evaluate the influence of exercise on plasma tryptophan (TRP) and free serotonin (f5-HT), whole blood-5-HT (WB-5-HT) and f5-HT/WB-5-HT ratio in Italian Saddle horses. Six clinically healthy Italian Saddle horses were subjected to a 450 meters obstacles course. Blood samples were collected from each horse by jugular venipuncture using vacutainer tubes with K₃-EDTA at rest, immediately after exercise, and after 30 min. TRP, f5-HT and WB-5-HT were analyzed by HPLC. Immediately after exercise, statistically significant increases of f5-HT (p<0.001) and WB-5-HT (p<0.001) were observed. After 30 min, f5-HT and WB-5-HT decreased compared to immediately after exercise, but were still significantly higher than rest values (p<0.01 and p<0.05, respectively). A significant linear regression between f5-HT and WB-5-HT was observed during experimental conditions. f5-HT and WB-5-HT modifications after exercise suggest an important role of peripheral serotoninergic markers in response to physical activity. The possible source of extra serotonin detected after show jumping should be clarified by further investigation.     

Atrial natriuretic peptide and cardiac troponin I concentrations in healthy Warmblood horses and in Warmblood horses with mitral regurgitation at rest and after exercise

ObjectiveAtrial natriuretic peptide (ANP) and cardiac troponin I (cTnI) serve as biomarkers for increased cardiac pressure/volume loading and for myocardial stress or damage. The objective was to describe the time course of plasma ANP concentrations (Cp_ANP) and plasma cTnI concentrations (Cp_cTnI) in horses with mitral regurgitation (MR) compared to healthy horses at rest and after exercise, and to describe the relationship of Cp_ANP with cardiac dimensions and intracardiac pressures.Animals15 healthy Warmblood horses and 7 Warmblood horses with MR.MethodsCardiac dimensions at rest were measured using echocardiography. All horses underwent standardized treadmill exercise. Biomarker concentrations and intracardiac pressures were measured at rest and after exercise. Hypotheses were tested using statistical methods. The level of significance was P < 0.05.ResultsHorses with MR showed increased left atrial (LA) and left ventricular (LV) dimensions but similar exercise capacity compared to healthy horses. Pulmonary capillary wedge pressures (PCWP) and Cp_ANP increased with exercise. Horses with MR had higher PCWP and higher Cp_ANP at rest and after exercise compared to healthy horses, with the maximum difference in Cp_ANP reached 10 min after exercise. Cp_ANP was significantly related to PCWP and – although inconsistently and only in healthy horses – to echocardiographic indices of LA and LV size and function. Cp_cTnI was low throughout the study in both groups.ConclusionsCp_ANP is increased in horses with MR and is related to LA pressures and to left heart dimensions. MR is not necessarily associated with exercise intolerance and exercise-induced myocardial stress or damage.