Injury and disease in the young thoroughbred racehorse: associations with subsequent racing performance.
MSc(R) thesis, University of Glasgow.
Full text available as:
There is limited research detailing the precise reason for foals failing to achieve different life-stages from birth to racing, even though almost 50% of foals do not reach flat race training in the UK (Wilsher et al., 2006). In order to increase the proportion of the Thoroughbred foal population that reach the racecourse, a better understanding of the reasons behind failure and associated risk factors is required. The aims of this project were to:
• Identify veterinary reasons for foals failing to reach training and racing.
• Identify juvenile veterinary problems associated with reduced race performance.
Content analysis (Wordstat: Provalis Research, Canada), was used to extract information from a free-text dataset that included the histories of 1044 foals born within an international breeding operation between 2000 and 2004, inclusive. Chi-squared tests were used to identify associations between type of early career injury (prior to entering full training) and successful entry into training.
Further analyses explored associations between the three most common juvenile veterinary problems and performance in racing. Career profiles were collected for the entire cohort using the Racing Post’s online dataset (www.racingpost.com). Information collected included; number of career starts, wins and places, prize money earned through winning a race, total prize money won, Official Ratings (OR’s) and Racing Post ratings. Two sampled t-tests and Mann Whitney tests were used to identify associations between juvenile veterinary problems and different measures of race performance. Šidák-Bonferonni corrections were used to adjust for multiple comparisons. Multiple linear regression models were used to account for potential confounding effects of other variables on performance (gender, year of birth and month of birth) and sire and dam were also included as a random effect in the model.
Of the original cohort, 56.5% (590) of horses entered full training successfully, while still under the ownership of the breeding operation. Sixty-one (7%) horses died before reaching this stage. Of these, 38% (23/61) failed to reach weaning and 62% (38/61) died either before entering training or before being sold post-weaning. A total of 717 horses (69%) were identified as having had at least one veterinary problem during their early years. Two hundred and fifty-seven horses were identified with no veterinary problems and 70 horses included insufficient data to identify whether they had veterinary problems. The most common veterinary problem identified was musculoskeletal injury or disease (excluding fractures) (MSK), with 50% (522/1044) of horses being affected, followed by fractures, 214 (21%), and the respiratory system, 179 (17%). Other problems identified included gastrointestinal, neurological, ophthalmic, infection and reproductive ailments.
One hundred and three horses (9.9%) sustained a fracture before reaching an age when they would have entered training. Of these, 64 (62%) did not enter training under ownership of the breeding operation; of these 46 (72%) were sold or gifted before entering training, 13 (20%) died before entering training and the remaining five (6%) were still in pre-training or went directly to stud. A total of 326 horses (31%) sustained an MSK before reaching training age. Of these, 141 (43%) did not enter training under ownership of the stud; of these 109 (77%) were sold or gifted before entering training, 21 (15%) died before entering training and 11 (8%) were still in pre training or went directly to stud. Ninety one horses (9%) were identified with a respiratory problem prior to reaching training age. Of these, 48 (53%) did not enter training under ownership of the breeding operation; of these 43 (90%) were sold or gifted, four (8%) died before reaching training age and one (2.1%) was still in pre training. Horses that sustained a fracture during their juvenile years were significantly less likely to enter training compared with the remainder of the cohort (p-value <0.001). Of the original 1044 horses 658 (63%) horses raced at least once. Maximum and mean OR’s were significantly reduced in horses that sustained a fracture prior to reaching training age (p-value <0.001). Gender was retained as being significantly associated with the outcome in multiple linear regression models (p-value <0.05) but adding sire and dam as a random effect did not significantly change any of the outcomes.
These analyses demonstrate the importance of avoiding serious injury during the first two-years of life for Thoroughbred racehorses. Although this study has identified the major priorities which could contribute to loss in the Thoroughbred breeding industry, further work is needed to identify and initiate potential management techniques that may help to minimise the risk of injury in the early years of a Thoroughbred’s career.
Actions (login required)