Long-term monitoring of clodronate in equine hair using liquid chromatography-tandem mass spectrometry.

Given the potential for long-term inhibition of bone remodeling/healing and detrimental effects to horses in training, bisphosphonates are tightly regulated in horseracing. Hair has proven to be an effective matrix for detection of drug administration to horses and has been particularly effective in detecting drugs for a long period of time post administration. Thus, hair may prove to be a useful matrix for detection of administration of this class of drugs. The objective of the current study was to develop an assay and assess the usefulness of hair as a matrix for long-term detection of clodronate to horses. Seven horses received a single intramuscular administration of 1.8 mg/kg clodronate. Hair samples were collected prior to and up to 6 months post administration. A liquid chromatography-tandem mass spectrometry method was developed and concentrations of clodronate measured in hair samples. The drug was first detected on day 7 in 4/7 horses, and on days 14, 28 and 35 in the remaining three horses. In 4/7 horses, clodronate was still detectable 6 months post administration. Results of this study demonstrate that, although there was significant inter-individual variability in detection times (63 to 180 days) and several intermediate times where the drug could not be detected but was subsequently detected in later timepoints, clodronate administration was detectable in hair for a prolonged period in most of the horses (4/7) studied.

Pharmacokinetics of intravenous flumetasone and effects on plasma hydrocortisone concentrations and inflammatory mediators in the horse.

BACKGROUND: Flumetasone is a potent corticosteroid reportedly used in horses to decrease inflammation associated with strenuous exercise. There are currently no reports describing the use of this drug in horses. OBJECTIVES: To describe the pharmacokinetics and effects on cortisol and eicosanoid concentrations, following administration of flumetasone to exercised horses. STUDY DESIGN: Parallel design. METHODS: Twelve exercised horses received a single i.v. administration of 5 mg of flumetasone. Blood and urine samples were collected before and for 72 h post-drug administration for determination of flumetasone and cortisol concentrations. Whole blood samples were collected at various time and challenged with lipopolysaccharide, calcium ionophore or methanol to induce ex vivo synthesis of eicosanoids. Concentrations of flumetasone, cortisol and eicosanoids were measured using LC-MS/MS and pharmacokinetic/pharmacodynamic analysis performed. RESULTS: Flumetasone was detected for 23.5 ± 1.73 h in blood. The volume of distribution at steady state, systemic clearance and elimination half-life was 5.90 ± 0.200 L/kg, 30.7 ± 0.166 mL/min/kg and 4.84 ± 0.83 h respectively. Cortisol concentrations were still suppressed at last time point collected (72 h). For cortisol, Kin , Kout and the t1/2out were 30.3 ± 1.56 ng/mL × h, 0.331 ± 0.02 1/h and 2.1 h respectively. Stimulation with lipopolysaccharide resulted in a decrease in TXB2 , PGF2 , LTB4 , 15-HETE and 5-HETE for up to 72 h and PGE2 for 24 h post-flumetasone administration. Stimulation of whole blood with calcium ionophore resulted in a decrease in LTB4 for up to 6 h and 15-HETE at 8 h. MAIN LIMITATIONS: Lack of sample collection for determination of biomarker concentrations beyond 72 h and the use of a single sample for determination of baseline cortisol concentrations. CONCLUSIONS: Flumetasone is rapidly cleared from blood following administration to horses. It is a potent anti-inflammatory with prolonged effects on production of cortisol and other inflammatory mediators.

An automated approach to the classification of impact spatter and cast-off bloodstain patterns.

In the forensic discipline of bloodstain pattern analysis, it has been suggested that there is a blurred boundary between characterising the features of a bloodstain pattern and determining the mechanism(s) that led to its deposition. This study proposes that bloodstain pattern classification can become a distinct and logical process by implementing an automated approach. To do this, an automated bloodstain pattern recognition system was developed to enable the distinction of two types of spatter bloodstain patterns. First, global pattern features based on common bloodstain pattern properties were extracted from laboratory-generated impact spatter and cast-off bloodstain patterns. Following this, automated feature selection methods were used to identify the combination of features that best distinguished the two bloodstain pattern types. This eventually led to the training and testing of a Fisher quadratic discriminant classifier using separate subsets of the generated bloodstain patterns. When applied to the training dataset, a 100% classification precision resulted. An independent dataset comprising of bloodstain patterns generated on paint and wallpaper substrates were used to validate the performance of the classifier. An error rate of 2% was obtained when the classifier was applied to these bloodstain patterns. This automated bloodstain pattern recognition system offers considerable promise as an objective classification methodology which up to now, the discipline has lacked. With further refinement, including testing it over a wider range of bloodstain patterns, it could provide valuable quantitative data to support analysts in their task of classifying bloodstain patterns.

Effectiveness of furosemide in attenuating exercise-induced pulmonary haemorrhage in horses when administered at 4- and 24-h prior to high-speed training.

BACKGROUND: Due to the high prevalence of EIPH in racehorses and its potential impact on the horse's health, furosemide administration is permitted up to 4-h prior to post time in most North American racing jurisdictions. Anecdotal reports suggest that administration of furosemide 24-h prior to strenuous exercise may be equally effective in decreasing the severity of EIPH. OBJECTIVES: To 1) compare the efficacy of furosemide in reducing the presence and severity of EIPH when administered 4- or 24-h prior to strenuous exercise 2) characterise electrolyte and blood parameters following administration of furosemide at 4- and 24-h prior to exercise. STUDY DESIGN: 3-way crossover. METHODS: Fifteen Thoroughbred racehorses received 5 mL of 0.9% NaCl or 250 mg of furosemide either 4- or 24-h prior to a 5-furlong simulated race. Blood samples were collected prior to and post-run for determination of furosemide, lactate, haemoglobin and electrolyte concentrations. One-hour post-race, an endoscopic exam and bronchoalveolar lavage (BAL) were performed. Horses were assigned an EIPH score based on predetermined criteria and the number of red blood cells in BAL fluid was determined. RESULTS: Endoscopic EIPH scores were lower in the 4-h vs. the 24-h (P = 0.03) furosemide groups. RBC counts in BAL fluid were lower in the 4-h furosemide vs. saline treatment groups (P = 0.01) but no difference was noted between the saline and 24-h furosemide groups (P = 0.3), nor between the 4- and 24-h groups (P = 0.5). MAIN LIMITATIONS: Small sample size and large range of running times for the 5-furlong work. CONCLUSIONS: While none of the treatments prevented EIPH, endoscopic scores and RBC counts in BAL fluid support the efficacy of furosemide in reducing the severity of EIPH. Endoscopic scores were lower in the 4-h furosemide group compared with 24-h administration. Red blood cell counts were lower in the 4-h furosemide group compared with saline treatment.

Pharmacokinetics of furosemide administered 4 and 24 hours prior to high-speed exercise in horses.

Furosemide is a diuretic agent used commonly in racehorses to attenuate the bleeding associated with exercise-induced pulmonary hemorrhage (EIPH). The current study describes serum and urine concentrations and the pharmacokinetics of furosemide following administration at 4 and 24 hrs prior to maximal exercise. Eight exercised adult Thoroughbred horses received a single IV administration of 250 mg of furosemide at 4 and 24 hrs prior to maximal exercise on a high-speed treadmill. Blood and urine samples were collected at time 0 and at various times for up to 72 hrs and furosemide concentrations determined using liquid chromatography-tandem mass spectrometry. Serum furosemide concentrations remained above the LOQ (0.05 ng/ml) for 36 hrs in 3/8 and 1/8 horses in the 4- and 24-hrs groups, respectively. Serum concentration data were best fit by a two-compartment model. There was not a significant difference in the volume of distribution at steady-state (0.594 ± 0.178 [4 hrs] and 0.648 ± 0.147 [24 hrs] L/kg) or systemic clearance (0.541 ± 0.094 [4 hrs] and 0.617 ± 0.114 [24 hrs] L/hrs/kg) between horses that were exercised at 4- and 24 hrs postdrug administration. The mean ± SD elimination half-life was 3.12 ± 0.387 and 3.23 ± 0.407 hrs following administration at 4 and 24 hrs prior to exercise, respectively.

An eye tracking study of bloodstain pattern analysts during pattern classification.

Bloodstain pattern analysis (BPA) is the forensic discipline concerned with the classification and interpretation of bloodstains and bloodstain patterns at the crime scene. At present, it is unclear exactly which stain or pattern properties and their associated values are most relevant to analysts when classifying a bloodstain pattern. Eye tracking technology has been widely used to investigate human perception and cognition. Its application to forensics, however, is limited. This is the first study to use eye tracking as a tool for gaining access to the mindset of the bloodstain pattern expert. An eye tracking method was used to follow the gaze of 24 bloodstain pattern analysts during an assigned task of classifying a laboratory-generated test bloodstain pattern. With the aid of an automated image-processing methodology, the properties of selected features of the pattern were quantified leading to the delineation of areas of interest (AOIs). Eye tracking data were collected for each AOI and combined with verbal statements made by analysts after the classification task to determine the critical range of values for relevant diagnostic features. Eye-tracking data indicated that there were four main regions of the pattern that analysts were most interested in. Within each region, individual elements or groups of elements that exhibited features associated with directionality, size, colour and shape appeared to capture the most interest of analysts during the classification task. The study showed that the eye movements of trained bloodstain pattern experts and their verbal descriptions of a pattern were well correlated.

Disposition of the anti-ulcer medications ranitidine, cimetidine, and omeprazole following administration of multiple doses to exercised Thoroughbred horses.

The use of anti-ulcer medications, such as cimetidine, ranitidine, and omeprazole, is common in performance horses. The use of these drugs is regulated in performance horses, and as such a withdrawal time is necessary prior to competition to avoid a medication violation. To the authors' knowledge, there are no reports in the literature describing repeated oral administrations of these drugs in the horse to determine a regulatory threshold and related withdrawal time recommendations. Therefore, the objective of the current study was to describe the disposition and elimination pharmacokinetics of these anti-ulcer medications following oral administration to provide data upon which appropriate regulatory recommendations can be established. Nine exercised Thoroughbred horses were administered 20 mg/kg BID of cimetidine or 8 mg/kg BID of ranitidine, both for seven doses or 2.28 g of omeprazole SID for four doses. Blood samples were collected, serum drug concentrations were determined, and elimination pharmacokinetic parameters were calculated. The serum elimination half-life was 7.05 ± 1.02, 7.43 ± 0.851 and 3.94 ± 1.04 h for cimetidine, ranitidine, and omeprazole, respectively. Serum cimetidine and ranitidine concentrations were above the LOQ and omeprazole and omeprazole sulfide below the LOQ in all horses studied upon termination of sample collection.

Elimination of cetirizine following administration of multiple doses to exercised thoroughbred horses.

Cetirizine is an antihistamine used in performance horses for the treatment of hypersensitivity reactions and as such a withdrawal time is necessary prior to competition. The objective of the current study was to describe the disposition and elimination of cetirizine following oral administration in order to provide additional serum concentration data upon which appropriate regulatory recommendations can be established. Nine exercised thoroughbred horses were administered 0.4 mg/kg of cetirizine orally BID for a total of five doses. Blood samples were collected immediately prior to drug administration and at various times postadministration. Serum cetirizine concentrations were determined and selected pharmacokinetic parameters determined. The serum elimination half-life was 5.83 ± 0.841 h. Average serum cetirizine concentrations were still above the LOQ of the assay (0.05 ng/mL) at 48 h (final sample collected) postadministration of the final dose.

Pharmacokinetics of guaifenesin following administration of multiple doses to exercised Thoroughbred horses.

Guaifenesin is an expectorant commonly used in performance horses to aid in the clearance of mucus from the airways. Guaifenesin is also a centrally acting skeletal muscle relaxant and as such is a prohibited drug with withdrawal necessary prior to competition. To the authors' knowledge, there are no reports in the literature describing single or multiple oral administrations of guaifenesin in the horse to determine a regulatory threshold and related withdrawal time. Therefore, the objective of the current study was to describe the pharmacokinetics of guaifenesin following oral administration in order to provide data upon which appropriate regulatory recommendations can be established. Nine exercised Thoroughbred horses were administered 2 g of guaifenesin orally BID for a total of five doses. Blood samples were collected immediately prior to drug administration and at various times postadministration. Serum guaifenesin concentrations were determined and pharmacokinetic parameters calculated. Guaifenesin was rapidly absorbed (Tmax of 15 min) following oral administration. The Cmax was 681.3 ± 323.8 ng/mL and 1080 ± 732.8 following the first and last dose, respectively. The serum elimination half-life was 2.62 ± 1.24 h. Average serum guaifenesin concentrations remained above the LOQ of the assay (0.5 ng/mL) by 48 h postadministration of the final dose in 3 of 9 horses.

Non-fatal injury occurrence in Southern California Thoroughbred racehorses 2009-2010.

Private-practice racetrack veterinarians in southern California recorded non-fatal injuries meeting defined criteria in Thoroughbreds for 1 year. Injury incidence was 2.29 injury events per 100 horse-months, which was lower than other studies where trainer reported injury data were collected. Of 477 injuries recorded, 344 (72.1%) were acute and 133 (27.9%) were chronic. Fractures were common (47.6% of injuries), with stress fractures accounting for 14% of injuries. Superficial digital flexor tendonitis and suspensory ligament desmitis accounted for 15.3 and 11.5% of injuries, respectively. Agreement between non-fatal injuries recorded in the current study and those recorded via an existing regulatory system (Equine Injury Database) was poor, with neither system capturing all injuries. Non-fatal injuries occurred 17-29 times more often than fatal injuries. Non-fatal musculoskeletal injury remains an ongoing issue for Thoroughbred racehorses, and an accurate, comprehensive system for recording these injuries is needed.

Pharmacokinetics and effects on thromboxane B2 production following intravenous administration of flunixin meglumine to exercised thoroughbred horses.

Flunixin meglumine is commonly used in horses for the treatment of musculoskeletal injuries. The current ARCI threshold recommendation is 20 ng/mL when administered at least 24 h prior to race time. In light of samples exceeding the regulatory threshold at 24 h postadministration, the primary goal of the study reported here was to update the pharmacokinetics of flunixin following intravenous administration, utilizing a highly sensitive liquid chromatography-mass spectrometry (LC-MS). An additional objective was to characterize the effects of flunixin on COX-1 and COX-2 inhibition when drug concentrations reached the recommended regulatory threshold. Sixteen exercised adult horses received a single intravenous dose of 1.1 mg/kg. Blood samples were collected up to 72 h postadministration and analyzed using LC-MS. Blood samples were collected from 8 horses for determination of TxB(2) and PGE(2) concentrations prior to and up to 96 h postflunixin administration. Mean systemic clearance, steady-state volume of distribution and terminal elimination half-life was 0.767 ± 0.098 mL/min/kg, 0.137 ± 0.12 L/kg, and 4.8 ± 1.59 h, respectively. Four of the 16 horses had serum concentrations in excess of the current ARCI recommended regulatory threshold at 24 h postadministration. TxB(2) suppression was significant for up to 24 h postadministration.

Disposition and metabolic profile of the weak androgen Dehydroepiandrosterone (DHEA) following administration as part of a nutritional supplement to exercised horses.

In order to ensure the welfare of performance horses and riders as well as the integrity of the sport, the use of both therapeutic and illegal agents in horse racing is tightly regulated. While Dehydroepiandrosterone (DHEA) is not specifically banned from administration to racehorses in the United States and no screening limit or threshold concentration exists, the metabolic conversion of DHEA to testosterone make its presence in nutritional supplements a regulatory concern. The recommended regulatory threshold for total testosterone in urine is 55 and 20 ng/mL for mares and geldings, respectively. In plasma, screening and confirmation limits for free testosterone (mares and geldings), of no greater than 0.1 and 0.025 ng/mL, respectively are recommended. DHEA was administered orally, as part of a nutritional supplement, to 8 exercised female thoroughbred horses and plasma and urine samples collected at pre-determined times post administration. Using liquid chromatography-mass spectrometry (LC-MS), plasma and urine samples were analyzed for DHEA, DHEA-sulfate, testosterone, testosterone-sulfate, pregnenolone, androstenedione, and androstenediol. DHEA was rapidly absorbed with maximal plasma concentrations reaching 52.0 ± 43.8 ng/mL and 32.1 ± 12.9 ng/mL for DHEA and DHEA sulfate, respectively. Free testosterone was not detected in plasma or urine samples at any time. Maximum sulfate conjugated testosterone plasma concentrations were 0.98 ± 1.09 ng/mL. Plasma testosterone-sulfate concentrations did not fall below 0.1 ng/mL and urine testosterone-sulfate below 55 ng/mL until 24-36 h post DHEA administration. Urine testosterone sulfate concentrations remained slightly above baseline levels at 48 h for most of the horses studied.

Pharmacokinetics and selected pharmacodynamics of cobalt following a single intravenous administration to horses.

Cobalt has been used by human athletes due to its purported performance-enhancing effects. It has been suggested that cobalt administration results in enhanced erythropoiesis, secondary to increased circulating erythropoietin (EPO) concentrations leading to improvements in athletic performance. Anecdotal reports of illicit administration of cobalt to horses for its suspected performance enhancing effects have led us to investigate the pharmacokinetics and pharmacodynamic effects of this compound when administered in horses, so as to better regulate its use. In the current study, 18 horses were administered a single intravenous dose of cobalt chloride or cobalt gluconate and serum and urine samples collected for up to 10 days post administration. Cobalt concentrations were measured using inductively coupled plasma mass spectrometry (ICP-MS) and pharmacokinetic parameters determined. Additional blood samples were collected for measurement of equine EPO concentrations as well as to assess any effects on red blood cell parameters. Horses were observed for adverse effects and heart rate monitored for the first 4 h post administration. Cobalt was characterized by a large volume of distribution (0.939 L/kg) and a prolonged gamma half-life (156.4 h). Cobalt serum concentrations were still above baseline values at 10 days post administration. A single administration of cobalt had no effect on EPO concentrations, red blood cell parameters or heart rate in any of the horses studied and no adverse effects were noted. Based on the prolonged gamma half-life and prolonged residence time, regulators should be able to detect administration of a single dose of cobalt to horses.

Detection and pharmacokinetics of three formulations of firocoxib following multiple administrations to horses.

REASON FOR PERFORMING STUDY: The use of firocoxib in horses and its ability to affect performance and potential to allow a horse to compete when it otherwise should not, necessitates establishing appropriate withdrawal time guidelines prior to performance. OBJECTIVES: To describe plasma concentrations and characterise the pharmacokinetics of 3 firocoxib formulations following multiple administrations of the label dose, with respect to recommended plasma thresholds for performance horses. STUDY DESIGN: Balanced 3-way crossover prospective study. METHODS: Nine healthy mature horses were administered firocoxib injectable solution (0.09 mg/kg bwt i.v. s.i.d. for 5 days), firocoxib paste (0.1 mg/kg bwt per os s.i.d. for 14 days) and firocoxib tablets (57 mg s.i.d. for 14 days). Blood samples were collected at Time 0 and at various times post drug administration until plasma concentrations were below the limit of detection of the assay. Plasma samples were analysed using liquid chromatography-mass spectrometry and data analysed using noncompartmental analysis. RESULTS: The mean plasma half-life was 1.64 ± 0.737, 1.70 ± 0.800 and 1.73 ± 0.767 days for injectable, paste and tablet formulations, respectively. Plasma concentrations fell below the Racing Medication and Testing Consortium's recommended threshold for racehorses (20 ng/ml) by 7 days post administration of the final dose for all formulations. Plasma concentrations never exceeded the threshold concentration (240 ng/ml) for horse competing in US Equestrian Federation events for any of the formulations. CONCLUSIONS: This study extends current knowledge regarding the pharmacokinetics of firocoxib and provides information that can be used to establish appropriate withdrawal time guidelines following multiple administrations, with respect to already established plasma regulatory threshold concentrations.

Pharmacokinetics and pharmacodynamics of butorphanol following intravenous administration to the horse.

Butorphanol is a narcotic analgesic commonly used in horses. Currently, any detectable concentration of butorphanol in biological samples collected from performance horses is considered a violation. The primary goal of the study reported here was to update the pharmacokinetics of butorphanol following intravenous administration, utilizing a highly sensitive liquid chromatography-mass spectrometry (LC-MS) assay that is currently employed in many drug-testing laboratories. An additional objective was to characterize behavioral and cardiac effects following administration of butorphanol. Ten exercised adult horses received a single intravenous dose of 0.1 mg/kg butorphanol. Blood and urine samples were collected at time 0 and at various times for up to 120 h and analyzed using LC-MS. Mean±SD systemic clearance, steady-state volume of distribution, and terminal elimination half-life were 11.5±2.5 mL/min/kg, 1.4±0.3 L/kg, and 5.9±1.5 h, respectively. Butorphanol plasma concentrations were below the limit of detection (LOD) (0.01 ng/mL) by 48 h post administration. Urine butorphanol concentrations were below the LOD (0.05 ng/mL) of the assay in seven of 10 horses by 120 h post drug administration. Following administration, horses appeared excited as noted by an increase in heart rate and locomotion. Gastrointestinal sounds were markedly decreased for up to 24 h.

Characteristics of Thoroughbred and Quarter Horse racehorses that sustained a complete scapular fracture.

REASONS FOR PERFORMING STUDY: To determine if scapular fractures occur in racehorses with distinctive characteristics. OBJECTIVES: To test the hypothesis that Thoroughbred (TB) and Quarter Horse (QH) racehorses with a scapular fracture have similar characteristics that are different from those of their respective racetrack populations. METHODS: Necropsy findings, case details, last race information and career earnings for TB and QH racehorses that had a scapular fracture in California between 1990 and 2008 were retrospectively compared between breeds. Horse signalment, career earnings, career starts and race characteristics were obtained for all California racehorses. Comparisons were made between affected horses, other racehorses that died, and all horses that raced, in California during the 19 year period. RESULTS: Seventy-three TB and 28 QH racehorses had a similar, complete comminuted scapular fracture with an articular component, and right forelimb predilection. The QHs had a higher incidence of scapular fracture incurred during racing than TBs (0.98 vs. 0.39/1000 starters). The TB and QH incident rates for musculoskeletal deaths incurred racing were 20.5 and 17.5/1000 starters, respectively; however, a greater proportion of TB musculoskeletal deaths occurred training (40% vs. 8%). Horses with a scapular fracture were more likely to be male and aged 2 or ≥ 5 years than the racetrack population. Most affected QHs (64%) were 2-year-olds; most TBs (74%) were aged ≥ 3 years. Scapular fractures occurred more commonly during racing in QHs (70%) than TBs (44%). Race-related scapular fracture was more likely to occur in a Maiden race than in a non-Maiden race. Horses with a scapular fracture had fewer career starts than the racetrack population. CONCLUSIONS AND POTENTIAL RELEVANCE: Despite breed differences for signalment and exercise distances, both breeds incur a complete scapular fracture that is more likely to occur in the right scapula of young and older, male racehorses, early in their race career or after few races. Quarter Horses sustain a catastrophic scapular fracture more frequently than TBs.

Pharmacokinetics and metabolism of dantrolene in horses.

Dantrolene is a skeletal muscle relaxant used commonly in performance horses to prevent exertional rhabdomyolysis. The goal of the study reported here was to begin to characterize cytochrome P450-mediated metabolism of dantrolene in the horse and describe the pharmacokinetics of the compound, formulated as a capsule or a compounded paste formulation, following oral administration. Dantrolene is rapidly metabolized to 5-hydroxydantrolene both in vivo and in vitro. Preliminary work with equine liver microsomes suggest that two enzymes are responsible for the metabolism of dantrolene, as evidenced by two distinct K(m) values, one at high and one at low substrate concentrations. For the pharmacokinetic portion of the study, a randomized, balanced 2-way crossover design was employed wherein eight healthy horses received a single oral dose of either capsules or paste followed by a 4 week washout period prior to administration of the second formulation to the same horse. Blood samples were collected at time 0 (prior to drug administration) and at various times up to 96 h postdrug administration. Plasma samples were analyzed using liquid chromatography-mass spectrometry and data analyzed using both noncompartmental and compartmental analysis. Peak plasma concentrations were 28.9 ± 21.6 and 37.8 ± 12.8 ng/mL for capsules and paste, respectively and occurred at 3.8 h for both formulations. Dantrolene and its major metabolite were both below the limit of detection in both plasma and urine by 168 h postadministration.

Serum biomarker levels for musculoskeletal disease in two- and three-year-old racing Thoroughbred horses: A prospective study of 130 horses.

REASON FOR PERFORMING STUDY: Biomarkers have shown some in vivo promise for the detection of musculoskeletal injuries, but further study to assess biomarker levels in clinical orthopaedic disease is required. OBJECTIVE: To assess 7 serum biomarkers for the detection of musculoskeletal injuries. METHODS: Two- and 3-year-old racehorses were entered into the study (n = 238). Exit criteria were lack of training for >30 days, or completion of 10 study months. Data from horses with solitary musculoskeletal injuries and completion of >2 months were analysed. Musculoskeletal injury was considered intra-articular fragmentation (IAF), tendon or ligamentous injury (TL), stress fractures (SF) and dorsal metacarpal disease (DMD). Monthly lameness examination and serum collection were performed. Serum was analysed for glycosaminoglycan (GAG), type I and II collagen degradation (C1, 2C), type II collagen synthesis (CPII), type II collagen degradation (Col CEQ), aggrecan synthesis (CS846), osteocalcin (OC) as a marker of bone formation and (C-terminal telopeptide of type I collagen) CTX as a marker of bone degradation. RESULTS: Of the 238 horses 59 injured and 71 uninjured control horses met the analysis criteria. Based on injury no significant differences in the proportions were observed for age, gender or lesion type, although a higher proportion of injuries occurred at the beginning of the study. Of injured horses, 16 (27%) sustained an IAF, 17 (29%) a TL injury, 7 (12%) SF and 19 (32%) were diagnosed with DMD. There were significant changes seen in biomarkers based on the injury incurred when longitudinal samples were assessed. Furthermore, based on the serum biomarkers collected prior to injury, horses could be correctly classified as injured or uninjured 73.8% of the time. CONCLUSIONS: A unique biomarker pattern occurred before each injury and this was beneficial in classifying horses as injured or uninjured. POTENTIAL RELEVANCE: Biomarkers have the potential to be used as a screening aid prior to musculoskeletal injury.

Factors influencing pre-race serum concentration of total carbon dioxide in Thoroughbred horses racing in California.

REASONS FOR PERFORMING STUDY: Many racing jurisdictions monitor pre-race serum concentration of total carbon dioxide (TCO2) among racing horses. To our knowledge, factors influencing concentration of TCO2 among horses participating in racing have not been systematically evaluated and reported. OBJECTIVES: To determine if characteristics of horses and racing conditions routinely recorded were significantly associated with pre-race concentration of TCO2, while accounting for and estimating effects of trainer and horse. METHODS: Pre-race serum TCO2 concentrations from 5028 starts made by 2,349 horses trained by 287 trainers at 2 racetracks in California during 2005 were examined. Data regarding characteristics of starters and race conditions obtained from a commercial database were recorded for each start. Data were analysed using mixed-effects, with TCO2 concentration as the dependent variable, and trainer and horse nested within trainer as random effects. RESULTS: Sex, class and distance of race, frusemide administration and cloudy weather conditions were significantly (P<0.001) associated with pre-race TCO2 concentration. Horses that finished in the top 3 positions had values that were slightly (0.2 mmol/) but significantly (P<0.001) greater than horses not finishing in the top 3. There were significant effects of trainer on pre-race TCO2 concentration. CONCLUSIONS: A variety of factors may influence pre-race TCO2 concentration in horses. Horses with better performance tend to have higher pre-race TCO2 concentrations. POTENTIAL RELEVANCE: TCO2 concentration is associated with improved performance although the magnitude of effect was quite small. Regulatory programmes based on monitoring should consider the influence of other factors on TCO2 concentration.