Effect of furosemide on performance of Thoroughbreds racing in the United States and Canada.

OBJECTIVE: To determine the effect of furosemide on performance of Thoroughbreds racing on dirt surfaces at tracks in the United States and Canada. DESIGN: Cross-sectional study. ANIMALS: All Thoroughbreds (n = 22,589) that finished a race on dirt surfaces at tracks in the United States and Canada between June 28 and July 13, 1997 in jurisdictions that allowed the use of furosemide. PROCEDURE: Race records were analyzed by use of multivariable ANOVA procedures and logistic regression analyses to determine the effect of furosemide on estimated 6-furlong race time, estimated racing speed, race earnings, and finish position. Principal component analysis was used to create orthogonal scores from multiple collinear variables for inclusion in the models. RESULTS: Furosemide was administered to 16,761 (74.2%) horses. Horses that received furosemide raced faster, earned more money, and were more likely to win or finish in the top 3 positions than horses that did not. The magnitude of the effect of furosemide on estimated 6-furlong race time varied with sex, with the greatest effect in males. When comparing horses of the same sex, horses receiving furosemide had an estimated 6-furlong race time that ranged from 0.56 +/- 0.04 seconds (least-squares mean +/- SE) to 1.09 +/- 0.07 seconds less than that for horses not receiving furosemide, a difference equivalent to 3 to 5.5 lengths. CONCLUSIONS AND CLINICAL RELEVANCE: Because of the pervasive use of furosemide and its apparent association with superior performance in Thoroughbred racehorses, further consideration of the use of furosemide and investigation of its effects in horses is warranted.     

Effects of furosemide on the racing times of Thoroughbreds

The effects of furosemide on the racing times of 79 horses without exercise-induced pulmonary hemorrhage (EIPH) and 52 horses with EIPH were investigated. Racing times were adjusted to 1-mile equivalent racing times by 2 speed handicapping methods, and analysis of covariance was used to adjust actual racing times by winning time and distance for each race. All 3 methods of determining racing time indicated that geldings without EIPH had significantly faster racing times (P less than 0.05) when given furosemide before racing than when furosemide was not given before racing. Females and colts without EIPH were determined to have faster racing times when furosemide was given before racing, but the difference was not significant. Geldings with EIPH had significantly faster racing times (P = 0.0231) when given furosemide before racing, as determined by one of the speed handicapping methods. There was a strong correlation (range 0.9314 to 0.9751) between the 1-mile equivalent racing times, as determined by the 2 speed handicapping methods for horses with and without EIPH. Furosemide failed to prevent the development of EIPH in many horses that were previously considered to be EIPH-negative. When given furosemide, 62 (25.3%) of 235 EIPH-negative horses were EIPH-positive after racing. Furosemide had questionable efficacy for prevention of EIPH in known EIPH-positive horses. Thirty-two (61.5%) of 52 EIPH-positive horses given furosemide before a race remained EIPH-positive after that race.     

Physiologic effects of furosemide in combination with water restriction when administered at 4 and 24 hours prior to high-intensity treadmill training

Although controversial, due to its reported effectiveness in attenuating bleeding associated with exercise-induced pulmonary hemorrhage (EIPH), furosemide is currently a permitted race day medication in most North American racing jurisdictions. The objective of this study was to assess the efficacy of furosemide in reducing the presence and severity of EIPH when administered 24 hr prior to strenuous treadmill exercise. Eight exercised Thoroughbred horses received saline or 250 mg of furosemide either 4 or 24 hr prior to high-speed treadmill exercise in a balanced 3-way cross-over design. Blood samples were collected for determination of furosemide, lactate, hemoglobin, blood gas, and electrolyte concentrations. Heart rate and pulmonary arterial pressure were measured throughout the run and endoscopic examination and bronchoalveolar lavage (BAL) performed. Horses were assigned an EIPH score and the number of red blood cells in BAL fluid determined. Although not significantly different, endoscopic EIPH scores were lower in the 4-hr versus the 24-hr and saline groups. RBC counts were not significantly different between the treatment groups. Pulmonary arterial pressures were significantly increased at higher speeds; however, there were no significant differences between dose groups when controlling for speed. A small sample size and unknown bleeding history warrant a larger-scale study.     

Efficacy of furosemide in the treatment of exercise-induced pulmonary hemorrhage in Thoroughbred racehorses

The repeatability of endoscopic observations of exercise-induced pulmonary hemorrhage (EIPH) and the efficacy of furosemide as a prophylactic treatment of horses with EIPH were studied in Thoroughbred race horses after consecutive breezes (at or near maximum speed, approx 16 m/s). Of 56 horses examined greater than or equal to 2 times, 21 (38%) had identical EIPH scores, whereas 26 (46%) and 9 (16%) had scores that differed by greater than or equal to 1 grade. In 56 nontreated horses, there was good agreement between 2 consecutive observations (K = 0.59, Z = 4.54, P less than 0.001). Similar comparisons after placebo (saline solution) treatment of 21 horses yielded fair to good agreement, whereas poorer agreement was seen after furosemide treatment of 23 horses. Comparison of average and maximum EIPH scores of 44 horses with a minimum of 4 observations (2 nontreated, 1 saline-treated, and 1 furosemide-treated) indicated that although furosemide did not stop EIPH, it did reduce the EIPH score in 28 (64%) horses.     

Effects of furosemide on the racing times of horses with exercise-induced pulmonary hemorrhage

In 3 groups of horses with exercise-induced pulmonary hemorrhage (EIPH), comparisons of racing times and finishing positions were made between the 5 races before the horses were given furosemide and 5 races after furosemide administration. The horses were grouped according to 3 methods used to diagnose EIPH: group 1, observation of hemorrhage at the nostrils within 1 hour after a workout or race; group 2, observation of pulmonary hemorrhage only by endoscopic examination after a race or workout; and group 3, observation of hemorrhage at the nostrils during a race or immediately after a race. Group 4 horses were randomly selected horses running during the study period and were not given furosemide. The statistical method was analysis of covariance and the dependent variable was horses' time per distance. The study compared the 4 groups of horses, using the estimated value of the horses (less than or equal to +10,000 or greater than +10,000), and the horses' interaction in races 1 through 5 before and races 6 through 10 after furosemide treatment. The horses' times were adjusted by the relevant covariates, distance, track variant, and winning time per distance. Significant changes in horses' time per distance were not noticed when comparing values from races 1 through 5 with those in races 6 through 10 in group 1 horses.(ABSTRACT TRUNCATED AT 250 WORDS)     

Risk factors for atrial fibrillation during racing in slow-finishing horses

OBJECTIVE: To determine prevalence of atrial fibrillation (AF) immediately after racing among racehorses that finished well behind the winners and examine potential risk factors for AF in these horses. DESIGN: Case-control study. ANIMALS: 39,302 racehorses representing 404,090 race starts in races sanctioned by the Japan Racing Association between 1988 and 1997. PROCEDURE: Horses that finished > or = 4 (turf races) or 5 (dirt races) seconds behind the winner or that did not complete the race were examined for AF within 5 minutes after the race. Logistic regression and chi2 analyses were used to determine whether sex, age, race distance, race surface, year, or development of epistaxis was associated with development of AF. RESULTS: Estimated minimum frequency of AF was 0.03% (123 instances of AF following 404,090 race starts), and estimated minimum prevalence of AF among racehorses was 0.29% (115 horses with AF among 39,302 racehorses). Estimated frequency of AF among horses that finished slowly or did not finish was 1.39% (120 instances of AF among 8,639 examinations), and estimated prevalence of AF in horses that finished slowly was 1.23% (92 instances of AF among 7,500 horses) or 1.01% when only the first time a horse finished slowly was considered (76 instances of AF among 7,500 horses). Atrial fibrillation was paroxysmal in most horses. Among horses that finished slowly, 4-year-old and older horses and horses that raced on turf were more likely to develop AF. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that the likelihood of AF among racehorses that finish slowly is related to age and racing surface.     

Effect of an external nasal dilator strip on cytologic characteristics of bronchoalveolar lavage fluid in Thoroughbred racehorses

OBJECTIVE: To determine the effects of an external nasal dilator strip on cytologic characteristics of bronchoalveolar lavage (BAL) fluid in racing Thoroughbreds. DESIGN: Clinical trial. ANIMALS: 23 Thoroughbred racehorses in active training. PROCEDURE: Each horse raced on 2 occasions: once while wearing an external nasal dilator strip and once while not. Bronchoalveolar lavage was performed 12 to 18 hours after each race, and BAL fluid was analyzed for RBC and leukocyte counts and hemosiderin content. RESULTS: Mean +/- SEM count of RBCs in BAL fluid when horses raced without the nasal dilator strip (84.6 +/- 275 cells/microL) was not significantly different from count when they raced with it (41.7 +/- 12.2 cells/microL). Horses were grouped as having mild or severe bleeding on the basis of RBC count in BAL fluid after horses raced without the nasal dilator strip. Mean count when horses with severe bleeding raced without the nasal dilator strip (271.0 +/- 63.7 cells/microL) was significantly higher than mean count when these horses raced with the strip (93.8 +/- 376 cells/microL). Mean count of lymphocytes in BAL fluid was significantly lower after horses raced with the external nasal dilator strip. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that use of an external nasal dilator strip in Thoroughbred racehorses may decrease pulmonary bleeding, particularly in horses with severe exercise-induced pulmonary hemorrhage.     

Review of furosemide in horse racing: its effects and regulation

Furosemide has been used empirically and has been legally approved for many years by the US racing industry for the control of exercise-induced pulmonary haemorrhage (EIPH) or bleeding. Its use in horses for this purpose is highly controversial and has been criticized by organizations outside and inside of the racing industry. This review concentrates on its renal and extra-renal actions and the possible relationship of these actions to the modification of EIPH and changes in performance of horses. The existing literature references suggest that furosemide has the potential of increasing performance in horses without significantly changing the bleeding status. The pulmonary capillary transmural pressure in the exercising horse is estimated to be over 100 mmHg. The pressure reduction produced by the administration of furosemide is not of sufficient magnitude to reduce transmural pressures within the capillaries to a level where pressures resulting in rupture of the capillaries, and thus haemorrhage, would be completely prevented. This is substantiated by clinical observations that the administration of furosemide to horses with EIPH may reduce haemorrhage but does not completely stop it. The unanswered question is whether the improvement of racing times which have been shown in a number of studies are due to the reduction in bleeding or to other actions of furosemide. This review also discusses the difficulties encountered in furosemide regulation, in view of its diuretic actions and potential for the reduction in the ability of forensic laboratories to detect drugs and medications administered to a horse within days or hours before a race. Interactions between nonsteroidal anti-inflammatory drugs (NSAIDs) and furosemide have also been examined, and the results suggest that the effects of prior administration of NSAID may partially mitigate the renal and extra-renal effects which may contribute to the effects of furosemide on EIPH.     

Frequency of and risk factors for epistaxis associated with exercise-induced pulmonary hemorrhage in horses: 251,609 race starts (1992-1997)

OBJECTIVE: To determine the frequency of epistaxis during or after racing among racehorses and identify factors associated with development of epistaxis. DESIGN: Retrospective study. SAMPLE POPULATION: 247,564 Thoroughbred and 4,045 Anglo-Arab race starts. PROCEDURE: Race start information (breed, age, sex, racing distance, and race type) was obtained for Thoroughbred and Anglo-Arab horses racing in Japan Racing Association-sanctioned races between 1992 and 1997. All horses that raced were examined by a veterinarian within 30 minutes of the conclusion of the race; any horse that had blood at the nostrils was examined with an endoscope. If blood was observed in the trachea, epistaxis related to exercise-induced pulmonary hemorrhage (EIPH) was diagnosed. RESULTS: Epistaxis related to EIPH was identified following 369 race starts (0.15%). Frequency of EIPH-related epistaxis was significantly associated with race type, age, distance, and sex. Epistaxis was more common following steeplechase races than following flat races, in older horses than in horses that were 2 years old, following races < or =1,600 m long than following races between 1,601 and 2,000 m long, and in females than in sexually intact males. For horses that had an episode of epistaxis, the recurrence rate was 4.64%. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that frequency of EIPH-related epistaxis in racehorses is associated with the horse's age and sex, the type of race, and the distance raced. The higher frequency in shorter races suggests that higher intensity exercise of shorter duration may increase the probability of EIPH.     

Values of urine specific gravity for thoroughbred horses treated with furosemide prior to racing compared with untreated horses.

The distribution of specific gravity values for 2,599 urine samples collected from racing Thoroughbred horses that were known to have received furosemide prior to racing was compared with that for 1,669 urine samples from racing Thoroughbred horses that reportedly had not received furosemide. Values of specific gravity for furosemide-treated horses were significantly lower (P < 0.001) than those for horses that had not received furosemide, and the proportion of horses with urine specific gravity either <1.010 or <1.012 was significantly greater (P < 0.001) among the furosemide-treated horses. These data indicate that evaluation of urine specific gravity would be a useful component of drug testing programs for regulation of furosemide use.     

Effect of training location and time period on racehorse performance in New Zealand. 1. Descriptive analysis

AIM: To describe characteristics of Thoroughbred training stables in Matamata and in all other locations in New Zealand combined, over two 19-month time periods in 1996–1997 and 1998–1999, representing equal length periods immediately prior to and after the construction of a new training surface at the Matamata Racing Club.

METHODS: Retrospective records covering all horses training and racing in New Zealand during two 19-month time periods (1996–1997 and 1998–1999), covering 161 locations, were obtained from New Zealand Thoroughbred Racing (NZTR). Outcome variables included whether a horse was raced again in the 6 months following any start in the first 13 months of either time period, number of race starts for every horse, and finishing position. Summary measures with confidence intervals (CI) and unadjusted odds ratios (OR), measuring strength of associations for various factors, were computed.

RESULTS: The datasets contained information on 45,446 horses, 11,336 races, 5,110 trials and a total of 110,643 race starts. Horses trained at Matamata represented 8% (3,715) of the total horse datasets, and accounted for 11,977 race starts (10.8%). They were more likely to start in a race or trial in either time period and were 1.4 and 1.3 times as likely to finish first, second or third compared with horses trained at other locations in 1996–1997 and 1998–1999, respectively. A 6-month no-race period occurred for 9,306/12,584 (74%) horses that started at least once in the first 13 months of either time period. Horses trained at Matamata were less likely to have a 6-month no-race period than horses trained at other locations in both time periods. There was no effect of time period within each location on the probability of either a horse having a 6-month no-race period or of a race start being followed by a 6-month no-race period, but there was an overall effect of time and more 6-month no-race periods were observed in 1998–1999 relative to 1996–1997.

CONCLUSION: Summary statistics are presented for Thoroughbred racing in New Zealand over two 19-month time periods. Differences between the populations of horses trained in Matamata compared with those trained at other locations were attributed, in part, to the fact that many of the more successful racehorse trainers in the country have stables at Matamata. As a result, the population of horses in Matamata may not be representative of the racehorse population in New Zealand. Although more likely to win or place in both time periods, the magnitude of the advantage to horses in Matamata was reduced in 1998–1999 relative to 1996–1997, and this could be due, in part, to effects of the new track surface at Matamata. There was no evidence of a rise in risk of a 6-month no-race period following any race start in those horses trained in Matamata in 1998–1999 relative to either horses trained at other locations or to horses trained in Matamata during the earlier time period.     

Postoperative Race Performance is Not Correlated with Degree of Surgical Abduction After Laryngoplasty in National Hunt Thoroughbred Racehorses

Objectives— To (1) assess the degree of arytenoid cartilage abduction lost after laryngoplasty (LP) in Thoroughbred National Hunt racehorses and (2) to correlate postoperative racing performance with degree of arytenoid abduction after LP. Study Design— Case series. Animals— National Hunt Thoroughbred racehorses (n=68). Methods— Grade of postoperative arytenoid abduction for National Hunt racehorses that had LP with ventriculocordectomy was assessed at 1 day, 6 days, and 6 weeks after LP. Race records were analyzed to ascertain if there was correlation between the degree of arytenoid cartilage abduction and various measures of race performance (return to racing postoperatively, total earnings in 5 races immediately postoperatively, and lifetime number of starts postoperatively). Results— Median postoperative arytenoid abduction was grade 2 on day 1 but had decreased to grade 3 by 6 weeks. Horses with grades 1, 2, and 3 abduction 1 day after surgery had median losses of 1, 1, and 0.5 abduction grades, respectively, at 6 weeks. Horses with grade 1 abduction on day 1 were significantly more likely to lose abduction by day 6 after surgery than horses with grade 3 abduction on day 1. There was no statistically significant correlation between the postoperative grade of arytenoid abduction at any time point and earnings in 5 races after surgery, likelihood of racing postoperatively, or total number of lifetime race starts postoperatively. Conclusions— Horses with maximal (grade 1) surgical arytenoid abduction are significantly more likely to suffer postoperative loss of abduction than those with grade 3 abduction. Postoperative grade of abduction does not appear significantly correlated with markers of racing performance in National Hunt racehorses; however, very few horses with poor (grade 4 or 5) abduction were included and thus conclusions regarding racing performance in such horses cannot be drawn from this study. Clinical Relevance— Seemingly, most horses with grade 3 laryngeal abduction can race successfully and perhaps surgeons should not be disillusioned by the appearance of only moderate (grade 3) abduction in the long term after LP in racehorses.     

Effect of training location and time period on racehorse performance in New Zealand. 1. Descriptive analysis

AIM: To describe characteristics of Thoroughbred training stables in Matamata and in all other locations in New Zealand combined, over two 19-month time periods in 1996-1997 and 1998-1999, representing equal length periods immediately prior to and after the construction of a new training surface at the Matamata Racing Club. METHODS: Retrospective records covering all horses training and racing in New Zealand during two 19-month time periods (1996-1997 and 1998-1999), covering 161 locations, were obtained from New Zealand Thoroughbred Racing (NZTR). Outcome variables included whether a horse was raced again in the 6 months following any start in the first 13 months of either time period, number of race starts for every horse, and finishing position. Summary measures with confidence intervals (CI) and unadjusted odds ratios (OR), measuring strength of associations for various factors, were computed. RESULTS: The datasets contained information on 45,446 horses, 11,336 races, 5,110 trials and a total of 110,643 race starts. Horses trained at Matamata represented 8% (3,715) of the total horse datasets, and accounted for 11,977 race starts (10.8%). They were more likely to start in a race or trial in either time period and were 1.4 and 1.3 times as likely to finish first, second or third compared with horses trained at other locations in 1996-1997 and 1998-1999, respectively. A 6-month no-race period occurred for 9,306/12,584 (74%) horses that started at least once in the first 13 months of either time period. Horses trained at Matamata were less likely to have a 6-month no-race period than horses trained at other locations in both time periods. There was no effect of time period within each location on the probability of either a horse having a 6-month no-race period or of a race start being followed by a 6-month no-race period, but there was an overall effect of time and more 6-month no-race periods were observed in 1998-1999 relative to 1996-1997. CONCLUSION: Summary statistics are presented for Thoroughbred racing in New Zealand over two 19-month time periods. Differences between the populations of horses trained in Matamata compared with those trained at other locations were attributed, in part, to the fact that many of the more successful racehorse trainers in the country have stables at Matamata. As a result, the population of horses in Matamata may not be representative of the racehorse population in New Zealand. Although more likely to win or place in both time periods, the magnitude of the advantage to horses in Matamata was reduced in 1998-1999 relative to 1996-1997, and this could be due, in part, to effects of the new track surface at Matamata. There was no evidence of a rise in risk of a 6-month no-race period following any race start in those horses trained in Matamata in 1998-1999 relative to either horses trained at other locations or to horses trained in Matamata during the earlier time period.     

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.     

Epidemiologic analysis of factors influencing exertional rhabdomyolysis in Thoroughbreds

OBJECTIVE: To determine incidence, effect on performance, and management practices associated with exertional rhabdomyolysis (ER) in Thoroughbreds. SAMPLE POPULATION: Medical records for 984 Thoroughbreds and a survey of trainers of horses with and without ER. PROCEDURES: Medical records for 984 Thoroughbreds stabled at a midwestern racetrack were examined to determine the incidence of ER during the 1995 racing season. A retrospective questionnaire was administered to trainers to determine management practices associated with ER in 59 Thoroughbreds with ER and 47 control Thoroughbreds in training. Multiple logistic regression was used to determine management factors associated with ER. RESULTS: ER affected 48 of 984 (4.9%) Thoroughbreds. Two-year-old females were most frequently affected, and 36 of 96 (37.5%) trainers had > or = 1 horse with ER. Horses with ER were more likely not to race during the racing season, compared with control horses. For horses that raced, differences were not found with respect to racing performance between ER and control horses. Exertional rhabdomyolysis developed frequently in susceptible horses that had > or = 1 day of rest prior to exercise and that galloped during exercise. Horses with ER were commonly fed > 4.5 kg of grain daily. Nervous and extremely nervous horses were 5.4 times more likely, and horses with some form of lameness were 4.2 times more likely, to have ER. CONCLUSIONS AND CLINICAL RELEVANCE: Exertional rhabdomyolysis is common in Thoroughbreds, and ER can be affected by temperament, sex, age, diet, exercise routines, and lameness. Management that minimizes excitability, particularly when tailored to each horse, may be most effective for controlling ER.     

Palmar carpal osteochondral fragments in racehorses: 31 cases (1994-2004)

OBJECTIVE: To evaluate records of racehorses with palmar carpal osteochondral fragments and determine whether the fragments were indicators of the severity of pathologic joint changes or prognosis. DESIGN: Retrospective case series. ANIMALS: 31 racehorses. PROCEDURES: Medical records, radiographs, and videos of arthroscopic procedures were reviewed. Information gathered included signalment; location, number, and size of the primary lesion; number and size of palmar carpal fragments; and details pertaining to surgical procedures. Outcome variables were obtained from race records. RESULTS: 31 horses met the selection criteria. Multiple palmar fragments were diagnosed in 58% of horses; small fragments (< 3 mm in diameter) were most common (52% of horses). Fifty-two percent of the horses returned to racing, 48% returned to racing and earned money, and 32% had at least 5 more starts. Horses with multiple fragments had significantly less earnings per start and lower performance index values after surgery than those with 1 fragment. Horses with palmar fragments < 3 mm in diameter were significantly less likely to return to racing and have 5 starts or to win money after surgery than horses with larger fragments. CONCLUSIONS AND CLINICAL RELEVANCE: Palmar carpal osteochondral fragments can be used as an indicator of clinically important joint pathology and as a prognostic indicator in racehorses. Horses with multiple small fragments were less likely to successfully return to racing than horses with only dorsally located carpal fragments or horses with 1 or 2 large palmar fragments. When possible, removal of palmar carpal osteochondral fragments should be considered.     

The association of 2‐year‐old training milestones with career length and racing success in a sample of Thoroughbred horses in New Zealand

Reasons for performing study: There is increasing evidence that exercise early in life has a positive effect on musculoskeletal health. At present, there is little whole population research investigating the effect of racing as 2‐year‐olds on future racing career. Objectives: To investigate the association between attaining training milestones as 2‐year‐olds with length of career and racing success in Thoroughbred horses in New Zealand. Methods: Retrospective data were obtained of the 2001/02‐born Thoroughbred foal crop. The 3 training milestones were: registered with a trainer, trialled and raced. The association of the training milestones with career length was measured using the outcomes: number of race starts and number of years raced, in a Cox regression model. Logistic regression models analysed the association of the training milestones with the outcomes: won or placed in a race. Linear regression was performed to assess the association of training milestones with total career earnings. Results: Of 4683 horses in the population; 3152 horses were registered with a trainer, 2661 horses trialled and 2109 horses raced. Horses that raced as 2‐year‐olds had significantly (P<0.001) more race starts than those first raced as 3‐year‐olds or older, this was also true when the 2‐year‐old year data were omitted. Horses that raced as 2‐year‐olds had significantly (P<0.001) more years racing. Horses registered with a trainer, trialled or raced as 2‐year‐olds were more likely to have won or been placed in a race than those that achieved the milestones as 3‐year‐olds or older. Horses that first trialled and raced as 2‐year‐olds had greater total earnings than those that first trialled or raced at a later age. Conclusions and potential relevance: Two‐year‐old training milestones had a strong association with positive racing career outcomes. Horses in training or racing as 2‐year‐olds may have better musculoskeletal health throughout life than horses that are first in training or racing at a later age.     

Frequency of musculoskeletal injuries and risk factors associated with injuries incurred in Quarter Horses during races.

OBJECTIVE: To determine the frequency and anatomic location of musculoskeletal injuries incurred by Quarter Horses during races and to compare data from injured horses and matched control horses. DESIGN: Matched case-control study. ANIMALS: 97 Quarter Horses that sustained a musculoskeletal injury during races and 291 horses from the same races that were not injured. PROCEDURE: Data examined included racing history, race-entrant characteristics, racing events determined by analysis of videotapes of races, and, when performed, results of prerace physical inspections. Data for injured horses were compared with data for control horses, using conditional logistic regression. RESULTS: Incidence of a catastrophic injury among Quarter Horses during races was approximately 0.8/1,000 race starts, whereas incidence of musculoskeletal injury during racing was approximately 2.2/1,000 race starts. Odds of musculoskeletal injury were approximately 8 times greater among horses assessed to be at increased risk of injury on the basis of results of prerace physical inspection than for horses not considered to be at increased risk of injury. Evidence was lacking that 2-year-old horses were at increased risk of injury or that sex influenced the risk of injury among Quarter Horses during races. CONCLUSIONS AND CLINICAL RELEVANCE: Incidence of racing injury among Quarter Horses appears to be lower than that observed among Thoroughbreds. Regulatory veterinarians can identify horses at increased risk of injury on the basis of prerace physical inspection, indicating that these inspections could be used to reduce the risk of injury during races.     

Equine bronchoalveolar lavage cytology: survey of Thoroughbred racehorses in training

SUMMARY Sixty-two Thoroughbred horses aged between 1 and 7 years in training in Sydney had bronchoalveolar lavage (BAL) samples collected for cytological examination. All horses, except the yearlings and those with a cough, had raced at the time of the examination and the trainers reported satisfactory performance. Free erythrocytes were found In 73% of samples and haemoslderophages In 90% of the samples, Indicating Immediate or past occurrences of exercise-Induced pulmonary haemorrhage (EIPH). Bronchoalveolar fluid from the yearlings contained significantly less (P / 0.05) erythrocytes and haemosiderophages than samples from horses In other age groups. In the older horses, there was also more haemosiderln within the macrophages. No differences In BAL cytology could be attributed to gender, and there was no relationship between BAL cytology and racing performance. The main cytological findings were (mean ± sd): total nucleated cells - 832 ± 578/μL with the main cell types being: macrophages - 59 ± 10% (haemosiderophages - 20 ± 24%); neutrophlls - 9 ± 6%; lymphocytes - 31 ± 9%. The erythrocyte count was 10.3 ± 17.7% of the total cell count. Horses with chronic coughing had a higher proportion of macrophages and a lower proportion of lymphocytes in the leucocytes obtained from BAL. There was a higher occurrence of EIPH detected In BAL findings than that previously reported when endoscopic examination has been used to diagnose EIPH. The occurrence and severity of EIPH as Indicated by the BAL findings was found to be related to exercise Intensity. The cytological findings were similar to those reported in horses in the northern hemisphere. We conclude that BAL cytology may be useful In the diagnosis of various lower respiratory tract disorders and that exercise-induced pulmonary haemorrhage occurs In virtually all horses In race training.