Uric acid responses to endurance racing and relationships with performance, plasma biochemistry and metabolic alterations

The Role of Intestinal Microbial Metabolites in the Immunity of Equine Animals Infected With Horse Botflies

The microbiota and its metabolites play an important role in regulating the host metabolism and immunity. However, the underlying mechanism is still not well studied. Thus, we conducted the LC-MS/MS analysis and RNA-seq analysis on Equus przewalskii with and without horse botfly infestation to determine the metabolites produced by intestinal microbiota in feces and differentially expressed genes (DEGs) related to the immune response in blood and attempted to link them together. The results showed that parasite infection could change the composition of microbial metabolites. These identified metabolites could be divided into six categories, including compounds with biological roles, bioactive peptides, endocrine-disrupting compounds, pesticides, phytochemical compounds, and lipids. The three pathways involving most metabolites were lipid metabolism, amino acid metabolism, and biosynthesis of other secondary metabolites. The significant differences between the host with and without parasites were shown in 31 metabolites with known functions, which were related to physiological activities of the host. For the gene analysis, we found that parasite infection could alarm the host immune response. The gene of “cathepsin W” involved in innate and adaptive immune responses was upregulated. The two genes of the following functions were downregulated: “protein S100-A8” and “protein S100-A9-like isoform X2” involved in chemokine and cytokine production, the toll-like receptor signaling pathway, and immune and inflammatory responses. GO and KEGG analyses showed that immune-related functions of defense response and Th17 cell differentiation had significant differences between the host with and without parasites, respectively. Last, the relationship between metabolites and genes was determined in this study. The purine metabolism and pyrimidine metabolism contained the most altered metabolites and DEGs, which mainly influenced the conversion of ATP, ADP, AMP, GTP, GMP, GDP, UTP, UDP, UMP, dTTP, dTDP, dTMP, and RNA. Thus, it could be concluded that parasitic infection can change the intestinal microbial metabolic activity and enhance immune response of the host through the pathway of purine and pyrimidine metabolism. This results will be a valuable contribution to understanding the bidirectional association of the parasite, intestinal microbiota, and host.

Uric Acid and Cortisol Levels in Plasma Correlate with Pre-Competition Anxiety in Novice Athletes of Combat Sports

Pre-competition anxiety is very prevalent in novice athletes, causing stress and drastic decreases in their performances. Cortisol plays a central role in the psychosomatic responses to stress and also in the physiology of strenuous exercise. Growing evidence links uric acid, an endogenous antioxidant, with oxidative stress and anxiety, as observed in many depressive-related disorders. We here compared anxiety inventory scores (BAI and CSAI-2), cortisol and biomarkers of oxidative stress in the plasma of novice combat athletes (white and blue belts) before and after their first official national competition, when levels of stress are presumably high. Although the novice fighters did not reveal high indexes of anxiety on questionnaires, significant correlations were confirmed between cortisol and cognitive anxiety (Pearson’s r = 0.766, p-value = 0.002, and a ‘strong’ Bayesian inference; BF10 = 22.17) and between pre-post changes of plasmatic uric acid and somatic anxiety (r = 0.804, p < 0.001, and ‘very strong’ inference; BF10 = 46.52). To our knowledge, this is the first study to report such strong correlations between uric acid and pre-competition anxiety in novice combat athletes. The cause-consequence association between these indexes cannot be directly inferred here, although the interplay between uric acid and anxiety deserves further investigation.

Does the type of exercise affect tryptophan catabolism in horses?

Tryptophan (Trp) is an essential amino acid which metabolises via the kynurenine pathway to generate a number of bioactive substances referred to as kynurenines. Among those are 3-hydroxykynurenine (3-HKyn) and quinolinic acid, which are neurotoxic, as well as kynurenic acid (Kyna) and xanthurenic acid (XA), which, similarly to nicotinamide (NAm), show neuroprotective and anti-depressive effects. Routine exercise is known to modulate Trp metabolism in skeletal muscle and is thus believed to reduce the risk of depressive states in humans and laboratory animals. Analogously, it was hypothesised that exercise can influence Trp metabolism in horses as well. The aim of this study was to evaluate the influence of two different types of exercise on Trp metabolism in horses of the same breed. A total of 32 purebred Arabian horses were involved in the study. The 22 three-year-old racehorses were subjected to short-time intense exercise. Ten other horses were made to perform endurance competitions at a distance of 80 km. Blood samples were collected at rest and following the end of the exercise period. Plasma concentrations of Trp, kynurenine (Kyn), Kyna, 3-HKyn, XA and NAm were determined using Ultra-High Performance Liquid Chromatography-Electrospray Ionisation-Tandem Mass Spectrometry. Short-time intense exercise led to an increase in plasma concentrations of Kyn, Kyna and XA. The endurance effort induced an increase in Kyna and a decrease in Trp and NAm levels. Both types of exercise, short-time intensive exercise and endurance exercise induced an increase in Trp metabolites, especially Kyna, and did not induce an increase in Trp level. Thus, from a pathophysiological perspective of the kynurenine pathway's influence on mental state, both types of exercise induced beneficial effects in horses.

Evaluation of Different Blood Parameters From Endurance Horses Competing at 160 km

The purpose of this study was to assess a change in different blood parameters before and after a 160 km endurance race and to evaluate differences in cardiac biomarkers between horses that completed the race and horses that did not. The study population consisted of 52 healthy endurance horses. Horses participating in the study were assigned to three groups: horses that successfully completed the race ("finishers"), horses that failed to qualify at the veterinary check for primarily metabolic reasons ("metabolic") and horses that failed to qualify at the veterinary check for primarily gait related reasons ("gait related"). The latter two groups were combined to form a final group of "non-finishers" that were excluded for either "gait related" or "metabolic" disorders. Venous blood samples were taken before and after the endurance race. Serum and EDTA-plasma were analyzed for cardiac troponin I (cTNI), heart fatty acid binding protein (HFABP), alpha-hydroxybutyrate dehydrogenase (α-HBDH), atrial natriuretic peptide (ANP), lactate dehydrogenase (LDH), symmetric dimethylarginine (SDMA) and asymmetric dimethylarginine (ADMA). Lactate dehydrogenase (P = .001), SDMA (P= .001) and ADMA (P= .002) increased significantly after the endurance race in the finisher group. A significant increase in cTNI and α-HBDH concentration after the endurance race compared to the values before the endurance race was detected in the finisher (P= .001, P= .001) and gait related group (P= .002, P= .007). The longer the distance completed, the more these five blood parameters increased. No differences between the groups could be found and none of the measured blood parameters showed significant differences among groups before or after racing.

Age and Hydration of Competing Horses Influence the Outcome of Elite 160 km Endurance Rides

High elimination rates and the concern for horse welfare are important issues in endurance riding. An improved understanding of the causes of elimination could increase completion rates in this sport. We have identified pre-ride risk factors that allow an assessment of potential elimination before the ride. A longitudinal cohort study was performed among 49 healthy horses competing in the 160 km endurance ride at the 2016 World Championship of Endurance Riding in Samorin/Slovakia. Blood samples were drawn before the ride. For statistical evaluation, horses were categorized in three groups: finishers, lame and metabolically eliminated horses. Risk factors were calculated for each group using multinomial logistic regression. A 1% increase in hematocrit levels was associated with a higher OR for elimination (lameness: OR 1.26, p = 0.017; metabolic: OR 1.34, p = 0.010). Furthermore, increased potassium values correlated negatively with the race outcome. For a 1 mmol/l increase in potassium, the lameness OR was 4.21, p = 0.039 and metabolic OR was 1.15, p = 0.848. Eight-year-old horses had a 100% elimination rate and survival analyses showed a significantly higher hazard for elimination (p = 0.025). We thus conclude that age and hydration affect the outcome of elite endurance rides. Further investigation of age as a risk factor seems to be clinically relevant and adjustments of FEI qualification modes may be appropriate.

Speed and Blood Parameters Differ between Arabian and Žemaitukai Horses during Endurance Racing

Fédération Equestre Internationale (FEI) has described equine endurance racing as the second largest discipline in the world, above which is only show jumping. The Žemaitukai is an ancient indigenous Lithuanian horse breed known since the 6th or 7th century. The Arabian horse breed is one of the oldest human-developed horse breeds in the world. Compared with other race horse breeds, the muscle tissue of Arabian horses is characterized by significant differences in structure-a predominance of oxidative fiber type I is observed in Arabians, making them the prevailing breed in endurance racing. The Arabian horses are recognized as the leading breed in endurance competitions. Speed, pace, and total time in the race strategy have been extensively studied in human sports, and in contrast, this strategy appears to have been virtually ignored in equestrian sport, despite the potential for contributing to performance optimization. In relation to speed and total time in the race, there are limited data on postrace physical, biochemical, and blood gas parameters of endurance horses. Thus, this study was carried out to investigate the effects of speed on the blood parameters of the Arabian and Žemaitukai horses during an endurance race. Blood samples were taken before and immediately after the exercise. Biochemical and blood gas indicators were analyzed. The study showed significant increases in mean blood gasometrical indicators, such as partial carbon dioxide pressure (8.09-15.18%, p < 0.001); base excess in the extracellular fluid (14.01%, p < 0.001 in the Arabian horses and 172.01% in the Žemaitukai breed, p = 0.006); decreases of the blood electrolyte ionized calcium (4.38-8.72%, p < 0.001) and the hematocrit and hemoglobin values (20.05-20.12%, p < 0.001 in the Arabian horses and 6.22-6.23% in the Žemaitukai breed, p = 0.003-0.004); and decreases in the base excess in the blood values (29.24-39.38%, p < 0.001) and lactate (13.45-31.97%, p < 0.001) in the blood of both breeds in the post-competition horses. Significant increases after competition were determined for the values of creatinine (21.34-30.82%, p = 0.001-0.004), total bilirubin (50.84-56.24%, PH < 0.001), and albumin (2.63-4.48%, p = 0.048-0.001) for both breeds. For the faster Arabian horse breed, recovering after racing took half the time that the local Žemaitukai breed did.

Expression of Phosphatonin-Related Genes in Sheep, Dog and Horse Kidneys Using Quantitative Reverse Transcriptase PCR

Simple Summary

Traditionally, it has been thought that control of body phosphorus was secondary to the tighter control of calcium. However, over the last 20 years, an extensive system for control of body phosphorus by proteins called phosphatonins has been shown to exist. Most research on phosphatonins has been done in rat or mouse models. This paper looks at whether important proteins and phosphorus channels in the phosphatonin pathways are present in the kidneys of dogs, horses and sheep. The results showed that all of the components of the phosphatonin system are present in these species, but that there are species differences in which protein or channel is most common, and in the relationships between the proteins and channels. This research is important because the phosphatonin system is involved in the progression of chronic kidney disease in humans and animals, and differences in the systems between animal species may affect treatment of chronic kidney disease.

Abstract

The aim of this preliminary study was to determine the relative expression of phosphatonin pathway-related genes in normal dog, sheep and horse kidneys and to explore the relationships between the different genes. Kidneys were collected post-mortem from 10 sheep, 10 horses and 8 dogs. RNA was extracted, followed by reverse transcriptase quantitative polymerase chain reaction for fibroblast growth factor receptor 1 IIIc (FGFR1IIIC), sodium-phosphate co-transporter (NPT) 1 (SLC17A1), NPT2a (SLC34A1), NPT2c (SLC34A3), parathyroid hormone 1 receptor (PTH1R), klotho (KL), vitamin D receptor (VDR), 1a-hydroxylase (CYP27B1) and 24-hydroxylase (CYP24A1). NPT2a was highly expressed in the dog kidneys, compared with those of the horses and sheep. NPT1 had greatest expression in horses and sheep, although the three different NPTs all had relatively similar expression in sheep. There was little variability in FGFR1IIIc expression, particularly in the dogs and horses. FGFR1IIIc expression was negatively correlated with NPT genes (except NPT2a in sheep), while NPT genes were all positively correlated with each other. Unexpectedly, klotho was positively correlated with NPT genes in all three species. These results provide the basis for further research into this important regulatory system. In particular, species differences in phosphatonin gene expression should be considered when considering the pathogenesis of chronic kidney disease.

Changes in biochemical parameters in horses during 40 km and 80 km endurance races

During intensive physical activity horses are exposed to thermolysis, electrolyte loss and rising amounts of catabolic products, which results in alterations of biochemical blood parameters due to the horse’s adaptation to metabolic stress. The aim of the present study was to determine the effect of intensive physical activity on serum biochemical parameters in horses competing in 40 and 80 km endurance races. Blood samples were taken from 28 horses before and after the race over four competitions, with a total of 53 samples analyzed. Biochemical parameters studied included creatine kinase, lactate dehydrogenase, aspartate aminotransferase, urea, creatinine, gamma-glutamyl transferase, glucose, triglycerides, cholesterol, sodium, potassium, calcium and magnesium. The extent of change in pre- and post-race values was compared between categories of age, gender, breed, distance and average speed of horses. Creatine kinase and blood glucose values prior to the race were higher than the reference values. Values of renal parameters and parameters of muscle damage increased after the races, and the degree of change was more pronounced at longer racing lengths, as well as at lower average speed. Electrolyte loss was more prominent during longer races. This study demonstrated that endurance races cause evident changes in serum electrolyte concentrations, renal parameters and markers of muscle damage in horses. These changes are observable in horses at both short and long duration endurance races.

Uric acid enhances longevity and endurance and protects the brain against ischemia

Among mammals, there is a positive correlation between serum uric acid (UA) levels and life span. Humans have high levels of UA because they lack a functional urate oxidase (UOX) enzyme that is present in shorter lived mammals. Here, we show that male and female mice with UOX haploinsufficiency exhibit an age-related elevation of UA levels, and that the life span of female but not male UOX+/- mice is significantly increased compared to wild-type mice. Serum UA levels are elevated in response to treadmill exercise in UOX+/- mice, but not wild-type mice, and the endurance of the UOX+/- mice is significantly greater than wild-type mice. UOX+/- mice exhibit elevated levels of brain-derived neurotrophic factor, reduced brain damage and improved functional outcome in a model of focal ischemic stroke. Levels of oxidative protein nitration and lipid peroxidation are reduced in muscle and brain tissues of UOX+/- mice under conditions of metabolic and oxidative stress (running in the case of muscle and ischemia in the case of the brain), consistent with prior evidence that UA can scavenge peroxynitrite and hydroxyl radical. Our findings reveal roles for UA in life span determination, endurance and adaptive responses to brain injury, and suggest novel approaches for protecting cells against injury and for optimizing physical performance.

The effect of repeated barrel racing on blood biomarkers and physiological parameters in Quarter Horses

The objective of this study was to evaluate barrel horses undergoing a field test with one repetition. Quarter-Horses were used (14 males and females; average age: 6.5 years old), and they ran two times for 5 min in the same field. Six different periods were evaluated: rest (T-0), immediately after the first (T-1) and second races (T-2), and after 15 (T-15), 30 (T-30) and 240 min (T-240) of recovery. Heart rate (HR), speed, distance and duration were measured using a HR monitor with GPS during the races. Blood was collected to determinate glucose, lactate, total proteins (TP), albumin, globulin, urea, creatinine, uric acid (UA), triglycerides, cholesterol, non-esterified fatty acids (NEFA), gammaglutamyltransferase (GGT), creatine kinase (CK), and cortisol concentrations, as well as to perform a haemogram. The results were analysed using ANOVA and Tukey’s tests using a P-value of 5%, and they showed a maximum HR>200 bpm after both races. The largest %HR>>170 bpm occurred in the second race (P<0.05). Glucose and lactate concentrations were elevated at T-2 (P<0.05). TP, creatinine, UA and triglycerides concentrations remained elevated at T-1, T-2 and T-30 (P<0.05). TP and creatinine concentrations returned to basal concentrations at T-30 (P>0.05), and UA and triglycerides returned to base concentrations at T-240 (P>0.05). NEFA, cholesterol, GGT and CK concentrations did not change (P>0.05). Cortisol concentrations were higher at T-2 (P<0.05) but at T-240 were similar to T-0 (P>0.05). Red blood cell concentrations and haematocrits had higher values after the second race (P<0.05). These results showed that barrel horses had intense exercise and that two races with a short rest interval between them produced similar metabolic and physiologic adaptations between races, showing that the proposed protocol may be a useful tool for field characterisation of horses’ training and may contribute to the implementation of adequate training and nutritional programs.

Antioxidant and haematological biomarkers in different groups of horses supplemented with polyunsaturated oil and vitamin E

Oxidative stress has been correlated with pathologies that impair the performance of athlete horses. The aim of this study was to assess the effects of supplementation with a mixture of polyunsaturated oil and vitamin E on the antioxidant and haematological biomarkers of horses. Horses under maintenance care (n = 6) and horses in training (n = 10) received 100 and 300 ml of the oil mixture respectively. Supplementation was provided for a period of 8 weeks, together with isocaloric inclusion. Blood samples were collected at three time periods (pretest, after 4 weeks and after 8 weeks) to analyse the following: the red blood cell count (RBCc); haemoglobin (Hb); haematocrit (HT); leucocytes; lymphocytes; platelets; the mean corpuscular volume (MCV); the mean corpuscular haemoglobin concentration (MCHC); the standard deviation of the red blood cell distribution width (RDW-SD); the coefficient of variation of the red blood cell distribution width (RDW-CV); glutathione peroxidase (GPx); superoxide dismutase (SOD); uric acid (UrAc); total plasma proteins (TPP); and creatine kinase (CK). After the 8 weeks of supplementation, animals under maintenance care exhibited significant increases in SOD, UrAc, the white blood cell count (WBCc), the RDW-SD and the RDW-CV (p < 0.05). The animals in training exhibited increases in GPx, SOD and UrAc (p < 0.05). In conclusion, supplementation with polyunsaturated oil and vitamin E increases blood antioxidants among animals under maintenance and in training, with different trends, while contributing to the fight against oxidative stress in each group analysed.

Protein catabolism and high lipid metabolism associated with long-distance exercise are revealed by plasma NMR metabolomics in endurance horses

During long distance endurance races, horses undergo high physiological and metabolic stresses. The adaptation processes involve the modulation of the energetic pathways in order to meet the energy demand. The aims were to evaluate the effects of long endurance exercise on the plasma metabolomic profiles and to investigate the relationships with the individual horse performances. The metabolomic profiles of the horses were analyzed using the non-dedicated methodology, NMR spectroscopy and statistical multivariate analysis. The advantage of this method is to investigate several metabolomic pathways at the same time in a single sample. The plasmas were obtained before exercise (BE) and post exercise (PE) from 69 horses competing in three endurance races at national level (130-160 km). Biochemical assays were also performed on the samples taken at PE. The proton NMR spectra were compared using the supervised orthogonal projection on latent structure method according to several factors. Among these factors, the race location was not significant whereas the effect of the race exercise (sample BE vs PE of same horse) was highly discriminating. This result was confirmed by the projection of unpaired samples (only BE or PE sample of different horses). The metabolomic profiles proved that protein, energetic and lipid metabolisms as well as glycoproteins content are highly affected by the long endurance exercise. The BE samples from finisher horses could be discriminated according to the racing speed based on their metabolomic lipid content. The PE samples could be discriminated according to the horse ranking position at the end of the race with lactate as unique correlated metabolite. As a conclusion, the metabolomic profiles of plasmas taken before and after the race provided a better understanding of the high energy demand and protein catabolism pathway that could expose the horses to metabolic disorders.

The welfare of young Polish Konik horses subjected to agricultural workload

Every year a new group of young Polish Konik colts are separated from the forest herds to be trained in the stable breeding system. The aim of this study was to evaluate how the young Polish Konik horses who had been born in a forest reserve adapt to and tolerate draft work. Two groups of 6 horses each were studied: (a) 3- to 4-year-old colts and (b) 7- to 13-year-old stallions. An effort response was estimated by heart rate (HR) registration and biochemical analysis of hematocrit; blood lactic acid (LA) level; and plasma concentration of glucose, triacylglycerols, uric acid, total protein, and cortisol as well as the activity of creatine kinase and lactate dehydrogenase. The mean HR workload response was significantly higher in the group of colts than in the adult stallions: 141 ± 19.3 bpm versus 124 ± 14.4 bpm, respectively. Blood LA level determined after effort was also significantly higher in colts than in stallions: 2.17 ± 0.42 and 1.40 ± 0.16 mmol/l, respectively. The increases in HR and blood LA levels in the colts were higher than in adult stallions, but such increases did not exceed the values characteristic for young working horses. Therefore, the Polish Konik colts evaluated in this study, and new colts who will be separated from the forest herds and brought to the stables in the future, can be subjected to the same work routine that has been used historically because it is not beyond their capabilities.

Hematologia e bioquímica sérica de equinos de concurso completo de equitação em treinamento

Avaliaram-se a hematologia e a bioquímica sérica em equinos de concurso completo de equitação (CCE) em treinamento durante testes de esforço incremental em esteira ergométrica de alta velocidade. Foram utilizados 16 equinos em delineamento experimental inteiramente ao acaso com quatro tratamentos e quatro repetições em esquema de parcelas subdivididas, utilizando-se como fontes de variação nos tratamentos a idade e o histórico de treinamento em CCE. As parcelas foram constituídas pelos testes incrementais realizados nas fases inicial e final do treinamento. As subparcelas foram representadas pelos tempos de avaliação e coletas. Os equinos do grupo experimental novos iniciantes apresentaram valor médio do hematócrito de 43,24%, sendo inferior ao hematócrito do grupo adultos iniciantes, 45,63%, novos experientes, 46,39%, e competidores, 47,74%. Houve diferença (P<0,05) entre os testes físicos realizados nas fases inicial e final do treinamento, com redução na concentração plasmática de glicose, de 112 para 98,88mg/dL, nas concentrações séricas de creatinina, de 1,41 para 1,29mg/dL, e de proteínas totais, de 6,52 para 6,38g/dL, na contagem de monócitos, de 0,54 para 0,48 10³/mm³, e com aumento na concentração plasmática de lactato, de 3,31 para 3,79mmol/L, na concentração sérica de ácido úrico, de 1,44 para 1,77mg/dL, no hematócrito, de 44,19 para 46,90%, na concentração de hemoglobina, de 14,33 para 15,10g/dL, e na contagem de leucócitos totais, de 9,26 para 9,61 10³/mm³. O treinamento dos equinos de CCE aumentou o condicionamento físico dos equinos, com maior capacidade de metabolização do lactato após o exercício e aumento nos valores basais do hematócrito e da concentração de hemoglobina.

Effects of acute creatine supplementation on iron homeostasis and uric acid-based antioxidant capacity of plasma after wingate test

Background

Dietary creatine has been largely used as an ergogenic aid to improve strength and athletic performance, especially in short-term and high energy-demanding anaerobic exercise. Recent findings have also suggested a possible antioxidant role for creatine in muscle tissues during exercise. Here we evaluate the effects of a 1-week regimen of 20 g/day creatine supplementation on the plasma antioxidant capacity, free and heme iron content, and uric acid and lipid peroxidation levels of young subjects (23.1 ± 5.8 years old) immediately before and 5 and 60 min after the exhaustive Wingate test.

Results

Maximum anaerobic power was improved by acute creatine supplementation (10.5 %), but it was accompanied by a 2.4-fold increase in pro-oxidant free iron ions in the plasma. However, potential iron-driven oxidative insult was adequately counterbalanced by proportional increases in antioxidant ferric-reducing activity in plasma (FRAP), leading to unaltered lipid peroxidation levels. Interestingly, the FRAP index, found to be highly dependent on uric acid levels in the placebo group, also had an additional contribution from other circulating metabolites in creatine-fed subjects.

Conclusions

Our data suggest that acute creatine supplementation improved the anaerobic performance of athletes and limited short-term oxidative insults, since creatine-induced iron overload was efficiently circumvented by acquired FRAP capacity attributed to: overproduction of uric acid in energy-depleted muscles (as an end-product of purine metabolism and a powerful iron chelating agent) and inherent antioxidant activity of creatine.

Decreased oxidative phosphorylation and PGAM deficiency in horses suffering from atypical myopathy associated with acquired MADD

Earlier research on ten horses suffering from the frequently fatal disorder atypical myopathy showed that MADD (multiple acyl-CoA dehydrogenase deficiency) is the biochemical derangement behind atypical myopathy. From five horses that died as a result of this disease and seven healthy control horses, urine and plasma were collected ante mortem and muscle biopsies were obtained immediately post-mortem (2 patients and 7 control horses), to analyse creatine, purine and carbohydrate metabolism as well as oxidative phosphorylation. In patients, the mean creatine concentration in urine was increased 17-fold and the concentration of uric acid approximately 4-fold, compared to controls. The highest degree of depletion of glycogen was observed in the patient with the most severe myopathy clinically. In this patient, glycolysis was more active than in the other patients and controls, which may explain this depletion. One patient demonstrated very low phosphoglycerate mutase (PGAM) activity, less than 10% of reference values. Most respiratory chain complex activity in patients was 20-30% lower than in control horses, complex II activity was 42% lower than normal, and one patient had severely decrease ATP-synthase activity, more than 60% lower than in control horses. General markers for myopathic damage are creatine kinase (CK) and lactic acid in plasma, and creatine and uric acid in urine. To obtain more information about the cause of the myopathy analysis of carbohydrate, lipid and protein metabolism as well as oxidative phosphorylation is advised. This study expands the diagnostic possibilities of equine myopathies.

Oxidant-antioxidant imbalance in horses infected with equine infectious anaemia virus

This study assesses the impact of equine infectious anaemia virus (EIAV) infection on the oxidant/antioxidant equilibrium of horses. Blood samples from 96 Romanian horses aged 1-25 years, were divided into different groups according to their EIAV-infection status, age, and time post-seroconversion. The effect of infection on oxidative stress was estimated by measuring enzymatic antioxidants (superoxide dismutase [SOD], glutathione peroxidase [GPx] and catalase), non-enzymatic antioxidants (uric acid and carotenoids), and lipid peroxidation (malondialdehyde [MDA]). Infection modified the oxidant/antioxidant equilibrium in the horses, influencing GPx and uric acid levels (P<0.05). Time post-seroconversion also contributed to oxidative stress imbalance, exhibiting a significant influence on both SOD and MDA concentrations in the blood (P<0.05). Animal age did not have a significant influence on oxidative stress. Recently infected horses (<1 year following seroconversion), and horses >5 years old, represented the most vulnerable category in terms of oxidative stress, followed by recently infected animals <5 years old. The results of this study are novel in implicating EIAV infection in the development of oxidative stress in horses.

Dehydration, electrolyte imbalances and renin-angiotensin-aldosterone-vasopressin axis in successful and unsuccessful endurance horses

REASON FOR PERFORMING STUDY

Limited information exists concerning the defence of homeostasis during endurance competitions and the relationship with performance.

OBJECTIVES

This research analysed renin (REN), angiotensin II (ANG), aldosterone (ALD) and vasopressin (AVP) in horses covering different distances, assesses differences between successful and eliminated horses and evaluates correlations between hydration status, renal function, electrolytes, REN, ANG, ALD and AVP.

METHODS

Packed cell volume (PCV), velocity and serum concentrations of REN, ANG, ALD, AVP, Na, K, Cl, Ca, Mg, P, creatine kinase, aspartate aminotransferase, lactate dehydrogenase, total proteins (TSP), albumin (ALB), serum uric nitrogen (SUN), creatinine (CREAT) and lactate were analysed in both successful horses (SH) and in horses eliminated due to metabolic problems (MH). Two types of competition were studied: 91 km in one day (Competition A: 20 SH, 9 MH) and 166 km in 2 days, 83 km/day (Competition B: 10 SH and 5 MH).

RESULTS

Research analysed renin was not affected by exercise, whereas ANG, ALD and AVP increased. In the SH group, resting ALD and AVP concentrations at the beginning of the second day of Competition B were higher than preride values. Vasopressin did not change during the second day of Competition B, whereas ALD progressively increased. Metabolic problems of both groups showed more evident dehydration (higher PCV, TSP, ALB, SUN and CREAT) and electrolyte alterations (more intense decreases of Na and Cl) than SH at the different sampling times. Metabolic problems presented higher ALD and AVP concentrations. Angiotensin II was higher at certain sampling times in the horses.

CONCLUSIONS

Endurance horses with dehydration and electrolyte disturbances showed a more intense activation of the REN-ANG-ALD-AVP axis.

POTENTIAL RELEVANCE

The study of the response of the REN-ANG-ALD-AVP axis during prolonged exercise in horses with different performance will aid to minimise the risk of metabolic diseases during competitions.

Modulation of circulating purines and pyrimidines by physical exercise in the horse

This study was designed to examine the influence of sub-maximal exercise on purine and pyrimidine catabolism in horses. Ten horses were initially trained for 12 weeks at the end of which they underwent a standardized exercise test (SET); venous blood samples were taken at rest, 5 and 30 min after the SET. Six untrained healthy horses, from which a blood withdrawal was taken at rest, were used as the control group. Samples were analyzed by HPLC for the simultaneous determination of uric acid, uridine, β-pseudouridine and creatinine in plasma. Glucose and lactate were measured in blood. Trained horses had basal uridine levels significantly lower than sedentary horses. The SET caused significant increase in plasma uric acid, uridine, β-pseudouridine and creatinine. Following the SET, a significant negative correlation was found between plasma uridine and glucose, whilst a significant positive correlation was observed between plasma uric acid and creatinine. These results indicate that increase in energy demand during exercise in the horse causes not only the degradation of purine but also of pyrimidine compounds, the latter possibly exerting a control on glucose uptake as also demonstrated in human beings.

Trot asymmetry in relation to physical performance and metabolism in equine endurance rides

REASON FOR PERFORMING STUDY

Trot is a symmetric gait and asymmetry might appear or increase during endurance rides due to lameness, pain or excessive fatigue.

HYPOTHESIS

To assess whether trot asymmetry increases during endurance competitions, whether it is possible to discriminate between horses with different performance and also its possible relationship with metabolism.

METHODS

Fifty-eight horses were filmed at trot during the lameness examinations in the vet-gates, before the competition (BCO), and after phases 1 (at 29 km), 2 (at 59 km) and 3 (at the end of the ride, at 80 km) and stride duration (SD) measured in all 4 limbs. A locomotion symmetry index (LSI) was calculated by comparing SD in the diagonal pairs of limbs. In all the cases, the longer diagonal pair SD was compared to the shorter. Horses were classified as symmetric (SyH) when LSI was lower than mean + 2s.d. and asymmetric (ASyH) when LSI was higher than mean + 2s.d. of the data obtained in BCO. Venous samples were withdrawn in the vet-gates and PCV, WBC, creatinine, TPP, uric acid, CK, AST, LDH, Na, K and Cl were measured. Horses were divided into different performance groups: successful (SH), lame (LH) and metabolic (MH), and according to ride velocity, the SH group was also divided into faster finishers (FF) and slower finishers (SF).

RESULTS

The percentages of SyH were high (>80%) and very similar between the different performance groups. LSI became more asymmetrical in the vet-gates, especially in the LH and MH groups. LSI presented negative correlations with the velocities during the rides and in the vet-gates and CK. The ASyH had higher velocities during the rides and plasma CK and lower velocities during the vet-gates and plasma uric acid concentrations.

CONCLUSIONS

Although trot asymmetry increases during endurance events, LSI calculated comparing SD in the two diagonal pair of limbs did not allow the differentiation of horses with different performance.