Bioavailability of detomidine administered sublingually to horses as an oromucosal gel.

The objective of the study was to determine the absorption, bioavailability and sedative effect of detomidine administered to horses as an oromucosal gel compared to intravenous and intramuscular administration of detomidine injectable solution. The study was open and randomized, with three sequences crossover design. Nine healthy horses were given 40 µg/kg detomidine intravenously, intramuscularly or administered under the tongue with a 7-day wash-out period between treatments. Blood samples were collected before and after drug administration for the measurement of detomidine concentrations in serum. The effects of the route of administration on heart rate and rhythm were evaluated and the depth of sedation assessed. Mean (±SD) bioavailability of detomidine was 22% (±5.3%) after sublingual administration and 38.2% (±7.9%) after intramuscular administration. The sedative effects correlated with detomidine concentrations regardless of the route of administration. We conclude that less detomidine is absorbed when given sublingually than when given intramuscularly, because part of it does not reach the circulation. Sublingual administration of detomidine oromucosal gel at 40 µg/kg produces safe sedation in horses. Slow absorption leads to fewer and less pronounced adverse effects than the more rapid absorption after intramuscular injection.

A Nordic survey of management practices and owners' attitudes towards keeping horses in groups.

Keeping horses in groups is widely recommended but limited information is available about how this is implemented in practice. The aim of this survey was to describe how horses are kept in the Nordic countries in relation to sex, age, breed, and equestrian discipline and to assess owners' attitudes toward keeping horses in groups. Horse owners in Denmark, Finland, Norway, and Sweden were approached using a web-based questionnaire, which was translated into 4 languages and distributed online via equestrian forums, organizations, and social media. The number of respondents was 3,229, taking care of 17,248 horses. Only 8% of horses were never kept in groups, 47% were permanently grouped for 24 h/d, and 45% were stabled singly but grouped during turnout. Yearlings were most often permanently kept in groups (75%), mares and geldings more commonly during parts of the day (50 and 51%, respectively), and stallions were often kept alone (38%). Icelandic horses were more likely to be permanently kept in groups (36%) than warmbloods (16%) and ponies (15%). Twice as many competition horses (51%) were never grouped compared with horses used for breeding (20%) or leisure purposes (15%). The majority of respondents (86%) strongly agreed that group housing benefits horse welfare and that it is important for horses to have the company of conspecifics (92%). Nevertheless, not all horses were kept in groups, showing that attitudes toward group housing may not necessarily reflect current management. The risk of injury was a concern of many respondents (45%), as was introducing unfamiliar horses into already established groups (40%) and challenges in relation to feeding in groups (44%). Safety of people (23%) and difficulties handling group-kept horses (19%) were regarded as less problematic. Results suggest that the majority of horses have the possibility to freely interact with other horses, either as fulltime members of a group during 24 h/d or during turnout. Future research should address the extent to which being a part-time member of a group affects horse welfare. For permanent group housing to become more widespread, such as it is the case for most farm animals, future research could focus on solving some of the reoccurring problems perceived with keeping horses in groups. The dissemination of evidence-based information on all aspects around keeping horses in groups can ultimately stimulate further positive changes in the management of group-kept horses.

Accumulation of uric acid in plasma after repeated bouts of exercise in the horse.

Plasma concentration of uric acid, total peroxyl radical-trapping antioxidative parameter (TRAP), blood lactate concentration and plasma activity of xanthine oxidase (XO) were measured in six Standardbreed trotters after six bouts of exercise with increasing intensity on two separate days three days apart. Blood samples were taken immediately, 5, 10, 15, 30 and 60 min after each heat and 2, 4, and 6 hr after the last heat. Exercise caused an increase in TRAP and in the concentrations of lactate and uric acid. Plasma uric acid concentration increased exponentially with respect to time after the last heat performed maximal speed, indicating a rapid increase in the rate of purine degradation. Plasma XO activity increased during exercise, but the intensity of exercise had only a minor effect on the level of XO activity. In conclusion, these data suggest that a threshold for the plasma accumulation of uric acid in terms of the intensity of exercise may exist and that XO may play a role in the formation of uric acid in horse plasma. Intense exercise causes an increase in the plasma antioxidant capacity that in the horse is mainly caused by the increase in the plasma uric acid concentration.

Resynthesis of glycogen in skeletal muscle from standardbred trotters after repeated bouts of exercise.

OBJECTIVE: To determine glycogen resynthesis rate and changes in plasma metabolite concentrations in horses before and after repeated exercise. ANIMALS: 6 clinically normal Standardbred trotters. PROCEDURE: Horses trotted distances of 3,000, 3,000, and 2,000 m (trial A) and 3 days later, trotted 2,100, 2,100, and 1,600 m (trial B). Horses had 1 hour rest periods between bouts of exercise. Trotting speed was increased with each exercise bout, up to a near maximal. Muscle biopsy specimens and venous blood samples were obtained before each trial and 0, 4, 24, 48, and 72 hours after the third bout. Blood samples were also taken between exercise bouts. Muscle glycogen content and plasma glucose, glycerol, nonesterified fatty acid, and triglyceride concentrations were determined. RESULTS: Muscle glycogen content was significantly decreased immediately after exercise from 473 +/- 45 to 329 +/- 79 mmol/kg of dry weight in trial A, and from 472 +/- 128 to 347 +/- 59 mmol/kg in trial B. Further decreases were measured 4 hours after exercise. Glycogen resynthesis was negligible 24 hours after exercise. Basal muscle concentrations of glycogen were obtained 72 hours after exercise in trial A (472 +/- 128 mmol/kg), but not in trial B (279 +/- 52 mmol/kg). Plasma concentrations of glucose were greater than or equal to before-exercise values. Plasma concentrations of lipid metabolites, glycerol, triglycerides, and nonesterified fatty acids, were less than before-exercise values 2 to 72 hours after exercising. CONCLUSIONS: Repeated bouts of exercise decrease glycogen repletion rate, which is not attributable to hypoglycemia, but may be influenced by limited availability of lipids for energy production.

Accumulation of allantoin and uric acid in plasma of exercising trotters.

Plasma concentrations of hypoxanthine, uric acid, and allantoin, which are breakdown products of adenine nucleotides, were measured in Standardbred and Finnhorse trotters during and after an exercise test on a high-speed treadmill, after an incremental exercise test performed on a racetrack, and after a racing competition. Fiber-type composition of the middle gluteal muscle and the muscle concentrations of adenine nucleotides and inosine monophosphate were measured after the racetrack test. Changes in the concentration of hypoxanthine were not observed in any of the tests. Peak concentration of uric acid was measured between 5 and 30 minutes after exercise, and it was three- to tenfold higher than the value at rest. The variability can be explained by intensity of the exercise test and variation among horses. The concentration of allantoin after exercise was 2 to 3 times as high as that at rest, depending on the intensity of the exercise, although the absolute increase was about 10 times as high as the increase in the concentration of uric acid. Peak values of allantoin for the treadmill and the racetrack tests were obtained 4 to 6 minutes after exercise and < 30 minutes after the races. Peak concentration of allantoin correlated positively with the percentage of type-II (IIA+IIB) fibers in the middle gluteal muscle. Significant correlations were not observed between plasma concentration of uric acid or allantoin and muscle concentrations of adenosine triphosphate (ATP) or inosine monophosphate. It can be concluded that in horses, breakdown of ATP during and after exercise continues until allantoin is produced.(ABSTRACT TRUNCATED AT 250 WORDS)

Freezability and fertility results with uncentrifuged stallion semen.

The first (1 to 3) sperm-rich fractions of the ejaculate were collected from 4 stallions using an open-ended vagina. The volume of the collected fractions was 12 +/- 8 ml with a density of 475 +/- 200 million spermatozoa/ml. Before freezing, the semen was diluted with a skim-milk based extender 1:1 to 1:8 (volume of semen: volume of extender), depending on the initial sperm concentration to achieve a final concentration of 100 million/ml. The total number of spermatozoa in an insemination dose ranged from 0.7 to 1 billion spermatozoa. Within 12 h after ovulation, 48 mares were inseminated in 70 cycles. The total single-cycle pregnancy rate at day 21 was 24%, but varied from 10% to 33% per cycle among the stallions.

Immunohistochemical analysis of MCT1 and CD147 in equine skeletal muscle fibres.

Monocarboxylate transporter 1 (MCT1) and its ancillary protein CD147 facilitate efflux of lactate from the muscle. Expression of MCT1 and CD147 were studied with immunohistochemistry in type I, IIA, IIAB and IIB fibres of equine gluteal muscle. Staining intensity of MCT1 in the cytoplasm as well as in the membranes of fibre types decreased in the order I=IIA>IIAB>IIB and correlated with the oxidative capacity. Capillaries were pronounced in the MCT1 staining. CD147 antibody stained plasma membranes of all fibre types evenly, whereas the staining in the cytoplasm followed that of MCT1. In the middle gluteal muscle the expression of MCT1 follows the oxidative capacity of muscle fibres, but the expression of CD147 in sarcolemma does not vary among fibre types. The use of horse specific MCT1 and CD147 antibodies can in future studies help to evaluate lactate efflux from different muscle fibre types.

alpha-Lipoic acid supplementation enhances heat shock protein production and decreases post exercise lactic acid concentrations in exercised standardbred trotters.

Heat shock protein (HSP) expression is an adaptive mechanism against the disruption of cell homeostasis during exercise. Several antioxidant supplementation strategies have been used to enhance tissue protection. In this study, we examined the effects of a redox modulator, alpha-lipoic acid (LA) on HSP responses in six standardbred trotters following intense aerobic exercise. DL-LA supplementation (25 mg kg(-1) d(-1)) for five weeks increased the resting levels of HSP90 (1.02+/-0.155 in control and 1.26+/-0.090 after supplementation in arbitrary units) and the recovery levels of inducible HSP70 (0.89+/-0.056 in control and 1.05+/-0.089 after supplementation in arbitrary units) in skeletal muscle. Furthermore, LA increased skeletal muscle citrate synthase activity at rest and lowered the blood lactate concentration during exercise without any changes in the heart rate. LA had no effect on concentrations of HSP60, HSP25 or GRP75 in skeletal muscle. LA decreased the exercise-induced increases in plasma aspartate aminotransferase and creatine kinase concentrations during recovery. Our results suggest that LA supplementation may enhance tissue protection and increase oxidative capacity of the muscle in horse.

Monocarboxylate transporters (MCT) as lactate carriers in equine muscle and red blood cells.

REASONS FOR PERFORMING STUDY: Monocarboxylate transporters (MCT) facilitate the transport of lactate across membranes. In red blood cells (RBC) the transport activity varies interindividually due to differences in the amount of an ancillary protein CD147. Similar variations in muscles could have a great influence on lactate accumulation during exercise. OBJECTIVES: To study the expression of MCT isoforms and CD147 in the middle gluteal muscle. METHODS: Venous blood and muscle biopsy samples were taken from 14 Standardbred horses. Lactate transport activity in RBC and the amounts of MCT1, 2, 4 and CD147 were measured. RESULTS: In muscle MCT1, MCT4 and CD147 were found. Amount of MCT1 was variable and not dependent on age or training. Expression of MCT4 increased with age and correlated positively with CD147. CD147 in muscle correlated with that in RBC. MCT4 in muscle and CD147/MCT1 in RBC were higher in race fit than in moderately trained horses. CONCLUSIONS: MCT isoform profile in equine muscle is similar to that in man. The correlation between CD147 in muscle and RBC supports the view that lactate transport activity in muscles may vary interindividually as with RBC. POTENTIAL RELEVANCE: A larger number of horses need to be analysed to confirm the relationship of CD147 in muscle and RBC; and to allow the use the lactate transport activity in RBC as an indicator of the respective activity in muscles.

MCT1 and CD147 gene polymorphisms in standardbred horses.

REASONS FOR PERFORMING STUDY: Transport of lactate across membranes is facilitated by proton-monocarboxylate transporters (MCT). The most widely distributed isoform is MCT1, which needs an ancillary protein CD147. Studies on erythrocytes have shown that high activity of MCT1 is inherited as the dominant allele and that activity is regulated through CD147. Mutations of human MCT1 have been described that appear to impair lactate transport in muscles and cause exertional rhabdomyolysis. There are no reports of this potential relationship in the horse. OBJECTIVES: To obtain sequences of equine MCT1 and CD147 to examine differences between horses with high and low lactate transport activity in their erythrocytes. METHODS: Muscle biopsy samples were taken from 3 healthy Standardbred horses and from 7 horses which according to the owners had signs of myopathy after intense exercise. DNA and RNA were isolated and PCR analysis and sequencing performed. RESULTS: Currently, PCR fragments covering 100% of MCT1 and 70% of CD147 coding region are retained and sequence analysis has demonstrated one single nucleotide polymorphism (SNP) in the C-terminal area of MCT1 and one SNP in the extracellular domain of CD147. Both cause an amino acid change. The SNPs found are not related to lactate transport activity in erythrocytes or signs of myopathy. CONCLUSIONS: More samples need to be analysed to make conclusions on the significance of the polymorphisms found. Furthermore, full sequence coverage of the coding region of CD147 is needed. POTENTIAL RELEVANCE: The molecular probes produced could be used as tools to study gene regulation of lactate transport.

Comparison on plasma caesium kinetics in goats and horses with special emphasis on exercising horses.

AIMS: Like potassium (K+), caesium (Cs+) tends to concentrate intracellularly. The aim here was to determine how moderate exercise affects the uptake of Cs+ from blood plasma. METHODS: After an intravenous Cs+ dose of 5 micromol kg(-1), plasma Cs+ concentration was followed for 100 min in goats and for 60 min in horses. The latter were divided into two groups, one resting and the other trotting on a treadmill (inclination 3 degrees, speed 5 m s(-1)). RESULTS: The plasma Cs+ concentration follows a multiphase exponential decay curve, which initially could be approximated with a two-phase curve. The initially high rate constant (approximately 10 h(-1)) decreased to around 1 h(-1) in 40 min. Exercise more than doubled the rate of removal of Cs+ from plasma between 20 and 40 min after the start of exercise. After exercise, the rate returned to resting levels within 10 min. Plasma K+, on the contrary, declined for at least 20 min after exercise had ended. CONCLUSIONS: Moderate exercise significantly increases the rate of removal of Cs+ from the bloodstream. After exercise, the rate returns to the resting levels within 10 min. The increased rate of Cs+ removal during exercise is likely due to increased activity of Na+, K+-ATPase in working skeletal muscles.

Effects of nandrolone treatment on recovery in horses after strenuous physical exercise.

To test the effect of nandrolone on their recovery, six adult half-bred riding horses performed a competition exercise test (CET) and a standardized exercise test (SET) on consecutive days before and after a 2-week treatment with the anabolic steroid nandrolone laurate. Blood samples were collected during and between these tests for the determination of red cell volume and concentrations of blood lactate, plasma glucose, non-esterified fatty acids, glycerol, triglycrides, erythropoietin, cortisol, insulin, and glucagon. Muscle biopsy specimens were taken immediately after the CET and before the SET for analysis of glycogen content, citrate synthase, and 3-hydroxyacyl CoA dehvdrogenase activity. Nandrolone administration increased the rate of muscle glycogen repletion after exercise, an increase that may be explained by increased glucose output by the liver, higher plasma insulin concentration, and increased insulin-independent glucose transport, but not by better availability of lipid fuels during recovery.

Fluid, electrolyte, and acid-base responses to exercise in racehorses.

During both high-intensity and short-distance exercise, the high rate of expended energy is met by anaerobic oxidation of glucose to lactic acid; this is the main cause of metabolic acidosis observed during racing. In addition, plasma volume decreases because water moves from the vasculature to the intracellular and interstitial spaces at the onset of intense exercise. These fluid shifts, together with active ion-exchange between blood and tissue, cause marked changes in electrolyte concentrations. This article reviews the mechanisms of acid-base disturbances, fluid shifts, and electrolyte changes, and discusses related areas such as buffer capacity, lactic acid distribution, and the effects of training. The influences of health, dietary cation-anion balance, supplements, and medication such as creatine, sodium bicarbonate, and furosemide are emphasized.

Metabolic and hormonal changes after exercise in relation to muscle glycogen concentrations.

To test whether, in horses, the concentration of muscle glycogen can be influenced by increasing the uptake of glucose into the muscle cells or by providing a gluconeogenic precursor, 9 trained half-bred riding horses performed on a treadmill a 1.5 h competition exercise test (CET). Each horse performed CET 3 times and 30 min after CET, each was given one of the following solutions: isotonic glucose-electrolyte (GE) solution, GE supplemented with 50 g leucine (GEL) to increase insulin secretion, or GE supplemented with 200 ml propionic acid (GEP), a gluconeogenic precursor. Administration of GE solutions caused no increase in plasma glucose concentration. The highest concentration of insulin was measured after GEL, but also in the GE group the concentration of insulin increased. GEP completely inhibited the increase in insulin concentration. Concentration of glucagon was increased 6 and 22.5 h after CET. None of the post exercise treatments influenced significantly the glycogen content at 22.5 h after CET. This indicates that neither i) elevation of insulin concentration to increase muscle-uptake of glucose, nor ii) increase in the availability of a glucose precursor, propionic acid, was able to increase accumulation of glycogen in the middle gluteal muscle.

Generalized fatal BaSO4 embolism from vaginal application of colonographic enema. A case report.

A 72-year-old woman died due to BaSO4 embolism from a ruptured vagina during colonography. The agony lasted for only 30 minutes. Post-mortem X-rays revealed opaque material in the region of the uterus and in the lungs. A tear, including a ruptured vein, filled with white material (BaSO4) was found in the vaginal wall. Barium was demonstrable in the microscopic sections of lungs, brain, liver and kidneys with rhodizonate staining. The case was classified as a therapeutic accident.

Effect of exercise on plasma ferritin concentrations: implications for the measurement of iron status.

Iron is of key importance for aerobic metabolism, and natural feeds of the horse are fairly rich sources of iron. Accordingly, the known incidence of iron deficiency anaemia is apparently rare in performance horses; despite this, iron deficiency in performance horses continues to be of concern to trainers and veterinarians. Effects of exercise on plasma ferritin concentrations were therefore studied in Standardbreds, Finnhorses and half-bred riding horses. Blood samples were taken after a moderate exercise test on a racetrack, a competition exercise test on a treadmill and a race. Even moderate exercise caused an increase in plasma ferritin concentration, with the increase being greater as the intensity and duration of exercise increased. Return to the basal level was slower after maximal-intensity exercise than after moderate exercise. In conclusion, although ferritin is a useful marker of low iron stores, samples should be taken only after at least 2 days rest following strenuous exercise.

Restoration of water and electrolyte balance in horses after repeated exercise in hot and humid conditions.

Nine adult riding horses performed on a treadmill a competition exercise test (CET) and 24 h later a standardised exercise test (SET) at mean temperature 28 degrees C and relative humidity 58%. Each horse performed the tests 5 times at 2 week intervals. The horses were given isotonic glucose-electrolyte solution via a nasogastric tube 30 min after the CET, except after the last trial when water was given. Blood lactate, plasma concentration of aldosterone, arginine vasopressin, protein, sodium, potassium, chloride, magnesium and calcium were measured. Heart rate at blood lactate concentration 4 mmol/l (PLa4) in the SET, plasma volume (PV) and red cell volume (CV) were determined. Mean weight loss after CET was 3.1% and did not change significantly during the study. Bodyweight loss (BWL2) before SET (-1.8% after the first trial) decreased linearly with time (P < 0.05) and was -0.8% after the fourth trial. After the fifth trial, when only water was given, the weight loss was -2.5%. PLa4 correlated significantly (P < 0.001) with BWL2 when BWL2 was greater than -1.2%. The horses acclimated to exercise in hot and humid conditions as indicated by better recovery of bodyweight, increased PV, lower peak lactate concentrations and heart rate and attenuated decrease in the concentrations of sodium and chloride. It is concluded that changes in bodyweight provide a good indication of recovery of horses after exercise in hot and humid conditions; and administration of an isotonic glucose-electrolyte rehydration solution after exercise helps to overcome dehydration better than water alone.

Plasma atrial natriuretic peptide during and after repeated exercise under heat exposure.

Plasma atrial natriuretic peptide (ANP) responses were studied in horses during and after a competition exercise test (CET) designed to simulate the endurance test of a 3-day event and including test Phases A-D. CET was repeated 5 times at 2 week intervals at mean temperature +28 degrees C and relative humidity (RH) 58%. Heart rate (HR) was monitored during CET. After CET, the horses were rehydrated with isotonic glucose-electrolyte solution or water. ANP, NH2-terminal pro-atrial natriuretic peptide (NT-ANP), aldosterone, arginine vasopressin (AVP) and plasma proteins (PP) were measured during CET and recovery. ANP rose with intensity and duration of exercise from 8 pmol/l to 15 pmol/l at a gallop (Phase B), remained elevated at Phases C-X, and peaked (23 pmol/l) at a canter (Phase D). Thereafter, ANP decreased to the pre-exercise level within 2.5 h irrespective of rehydration. Repeated exercise bouts failed to affect plasma ANP, although other adaptive changes occurred. No diurnal variation in plasma ANP appeared. In NT-ANP, the most marked elevation occurred during Phases C-D. In contrast to ANP, the decrease was minor for 1 h after the canter. ANP did not correlate with AVP or HR. In conclusion, exercise per se affected equine plasma ANP but the possible effect of thermal stress could not be demonstrated. The differences between ANP and NT-ANP responses indicate differences in their release or elimination and suggest that the cardiac prohormone cleavage may occur intracellularly or simultaneously with secretion, not in circulation.

Factors affecting accumulation of lactate in red blood cells.

In horses, both the post exercise distribution of lactate between plasma and red blood cells (RBC) and the activity of lactate transporters on the RBC membrane vary widely between individuals. In this study, we investigated the effects of pH, time and temperature on lactate distribution in vitro, and compared the in vitro activity of lactate transporters with the accumulation of lactate into RBC in vivo. To accomplish this, we took venous blood samples at rest and after trotting races. The post exercise accumulation of lactate into RBC was shown to depend on the activity of lactate transporters. The results, in vitro, also indicate that pH, incubation time and temperature influence the activity of lactate transporters and the accumulation of lactate into RBC, underscoring the fact that in practice it is important to standardise the measurement conditions of lactate. These results support the view that whole blood lactate concentrations should be measured in estimating the accumulation of lactate from exercising muscles into the blood, because the effect of blood pH, temperature, time to centrifugation of the sample and also interindividual variation in lactate transport into RBC are therefore minimised.