Competition lifespan survival analysis in the Norwegian‐Swedish Coldblooded Trotter racehorse

Return of showjumping horses to sporting activity after colic surgery

BACKGROUND

The return to performance after colic surgery is crucial for competition horses. While studies have investigated racehorse performance following colic surgery by analysing racing participation and earnings, this approach does not apply to showjumping horses, leaving a gap in the literature regarding their objective performance evaluation.

OBJECTIVES

To assess the short- and long-term survival and return to performance in showjumping horses after colic surgery.

STUDY DESIGN

Retrospective case series.

METHODS

Medical records of horses with acute colic requiring surgical treatment were analysed, and data for showjumping horses (Group 1) were retrieved. Telephone follow-ups were conducted and national competition databases were used to collect pre- and postoperative showjumping competition entries for Group 1 and for randomly selected horses (Group 2) participating in the same competitions as a comparison group.

RESULTS

Of 253 horses undergoing colic surgery, 96 were recorded as showjumpers. The median long-term survival was 2.73 (0.01-6.14) years. Among these horses, 59 were competing at the time of surgery, and of these, 46 (78%) returned to competition and 41 (89.1%) competed at the same or higher level, while 5 (10.9%) competed at a lower level. At a 2-year follow-up, 63.6% of the showjumping horses that underwent colic surgery were alive. No significant differences were observed in the level of competition and career length between horses, which underwent colic surgery, and the randomly selected comparison group.

MAIN LIMITATIONS

Small sample size and a single-centre design.

CONCLUSIONS

Showjumping horses can make a successful return to competition after colic surgery, with the majority performing at the same or higher level as before the procedure.

Should performance at different race lengths be treated as genetically distinct traits in Coldblooded trotters?

Speed, in the form of racing time per kilometre (km), is a performance trait of the Swedish-Norwegian Coldblooded trotter included in the joint Swedish-Norwegian genetic evaluation. A few popular stallions have dominated Coldblooded trotter breeding, which has led to an increasing average relationship between individuals in the population. This study investigated the scope for broadening the breeding goal by selecting for racing time per km over different race lengths (short: 1640 m, medium: 2140 m and long: 2640 m), as this could encourage the use of breeding sires that are less related to the population. Performance data on three- to 12-year-old Coldblooded trotters in all Swedish races run 1995-2021 were obtained from the Swedish Trotting Association. These data consisted of 46,356 observations for 8375 horses in short-distance races, 430,512 observations for 11,193 horses in medium-distance races and 11,006 observations for 3341 horses in long-distance races. Variance components and genetic correlations were calculated using a trivariate animal model with Gibbs sampling from the BLUPF90 suite of programs. Breeding values for the three traits were then estimated using univariate animal models with the same fixed and random effects as in the trivariate model. Heritability estimates of 0.27-0.28 and genetic correlations between racing time per km at the different distances of 0.97-0.99 were obtained. Despite the strong genetic correlation between the traits, there was some re-ranking among the top 10 and top 30 stallions based on distance-specific breeding values. Estimated rank correlation between breeding values for racing time per km in short- and medium-distance races was 0.86, while between short- and long-distance races and between medium- and long-distance races it was 0.61. Mean relationship within the top 10 and top 30 stallions based on breeding values for racing time per km at each distance was 0.31-0.33 and 0.23-0.24 while mean relationship to the rest of the population ranged from 0.17 to 0.18 for all groups, although the 10 and 30 top-ranking stallions differed somewhat in the traits. Estimated average increase in inbreeding was 0.1% per year of birth and 1.2% per generation. The strong genetic correlation between racing time per km at different distances did not support their use as genetically distinct traits. Re-ranking of stallions for racing time per km at different race lengths could favour the use of a larger number of stallions in breeding, but according to our results it would not promote the use of stallions that are less related to the total population. Other traits like longevity or health traits, for example, career length and orthopaedic status, may be more relevant in broadening the breeding goal and preventing a few sires dominating future breeding, and this would be interesting to study further.

Racing-associated fatalities in Norwegian and Swedish harness racehorses: Incidence rates, risk factors, and principal postmortem findings

BACKGROUND

There are no reports on the number of fatalities or causes of death in the Norwegian and Swedish harness racehorses.

OBJECTIVES

The incidence rates (IRs), risk factors, and postmortem findings in horses that died or were euthanized associated with racing between 2014 and 2019 were investigated.

ANIMALS

Thirty-eight Standardbreds and 10 Norwegian-Swedish Coldblooded Trotters died or were euthanized associated with racing. A total of 816 085 race-starts were recorded.

METHODS

Incidence rates were calculated for both countries and horse breeds. Risk factors for sudden death were identified using a case-control logistic model. Postmortem examinations were performed in 43 horses.

RESULTS

The overall fatality IR was 0.059/1000 race-starts. Traumatic injuries accounted for 14.5%, while sudden death for 85.5% of fatalities. Only minor differences between countries and breeds were recorded. The number of starts within the last 30 days increased the risk of sudden death (5 starts odds ratio (OR) 228.80, confidence interval (CI) 10.9-4793). An opposite non-linear effect was observed in number of starts the last 180 days (>10 starts OR 0.12, CI 0.02-0.68). Seven horses were euthanized because of catastrophic injury. Acute circulatory collapse because of suspected cardiac or pulmonary failure or both was recorded in 30 horses, while major hemorrhage after vessel rupture was the primary cause of death in 10 cases. One horse collapsed and died but was not submitted for autopsy.

CONCLUSIONS AND CLINICAL IMPORTANCE

Comparatively low rates of catastrophic orthopedic fatalities were reported, while causes and IR of sudden death were similar to previous studies.

Investigation of Factors Influencing Thoroughbred Horses' Racing Career Length in Turkey

The aim of this research was to determine the average length of a Thoroughbred horse's racing career in Turkey using survival functions of Thoroughbred horses with various characteristics. In addition, the aim was to identify risk factors that could influence the duration of a Thoroughbred horse's racing career and develop a survival model that took these factors into account. A total of 11,721 Thoroughbred horses born in 2007 and later were included in the study population. The horses involved in the study were followed for a minimum of 1 year. Kaplan-Meier analysis was used to calculate the average length of racing career for each factor studied. Extended Cox regression analysis was used to determine the risk factors upon time of career ending and to create a survival model. Results showed that, the mean career length of Thoroughbred horses was 17.79 months (95% CI: 17.41-18.13). Also, "starting age of the race," "number of starts," "type of track where the race started," "racing on a single type racetrack" and "earning status" were found risk factors that affect the length of the racing career. Earnings was the top relative contributor to the established model, and its sole adjusted effect showed that being in the lowest earning group increased the hazard of career ending 2.28 times (95% CI:1.98-2.61) compared to horses with highest earning group. In conclusion, clear differences upon the length of racing career was observed for each investigated factor. Future studies should be considerate of these differences when analyzing population data.

Two-dimensional, M-mode and left atrial velocity echocardiographic measurements in healthy Norwegian-Swedish Coldblooded Trotters

INTRODUCTION

The Norwegian-Swedish Coldblooded Trotter (NSCT) is an important breed in Norwegian and Swedish harness racing. In spite of this, little is known about its cardiac measurements and factors that may influence these. The aims of this study were to establish reference intervals (RI) for a series of conventional echocardiographic variables, primarily of the left heart, in NSCTs in race training and to evaluate any effects age, gender, estimated body weight (EBW), number of starts and racing performance may have on these.

ANIMALS

Sixty-three apparently healthy NSCTs in race training.

METHODS

Observational study, convenience sampling. All horses were examined unsedated in their normal stabling environment. Auscultatory and echocardiographic examinations were performed. Means, standard deviations, medians and confidence intervals of the RI limits were used to summarize the data. The relationship between selected echocardiographic variables and age, gender, EBW, racing performance and number of starts were explored using linear regression analyses.

RESULTS

Reference intervals were determined for routinely used echocardiographic variables. Data for left atrial velocity were also obtained. Increasing age, number of starts and money earned significantly increased all cardiac measurements. Males had significantly higher ventricular measurements than females. Great vessel measurements increased with increasing EBW. Horses with faster recorded racing times had generally significantly increased cardiac measurements. Clinically insignificant valvular regurgitation was a common finding, particularly at the tricuspid and pulmonary valves.

CONCLUSIONS

The RIs described and the factors that may affect these will assist clinicians in interpreting echocardiograms of NSCTs with suspected cardiac disease or poor performance.