Preliminary Examination of the Biological and Industry Constraints on the Structure and Pattern of Thoroughbred Racing in New Zealand over Thirteen Seasons: 2005/06–2017/18

SIMPLE SUMMARY: The training and racing schedules of Thoroughbred racehorses vary within a racing jurisdiction. Changes in regulation at a local or national level can alter the frequency of racing, age profile and the number of and duration of spells (rest periods) for horses in active race training. In order to consider any intervention to reduce injury risk at an industry level, it is important to understand all the parameters pertinent to the racing jurisdiction; both those constrained by biology and by the economics of the racing system. The number of horses and races in New Zealand is decreasing, with a concurrent increase in both the age of horses and the proportion of fillies racing. However, the pattern of race starts remained the same, highlighting the individual biological constraints of the horses in the system. If the industry is considered as a bio-economic system, then the racing system will converge towards efficiency and optimisation of resources. Within this framework, the described trend is likely to continue if the number of horses entering the system continues to decrease. Therefore, these data present a basis for the modelling of changes in racing regulations and injury intervention strategies within this conceptual framework to account for the economic and biological constraints. ABSTRACT: This study aimed to examine thirteen seasons of flat racing starts (n = 388,964) in the context of an ecological system and identify metrics that describe the inherent characteristics and constraints of the New Zealand Thoroughbred racing industry. During the thirteen years examined, there was a 2–3% per year reduction in the number of races, starts and number of horses. There was a significant shift in the racing population with a greater number of fillies (aged 2–4 years) having a race start, and subsequent longer racing careers due to the inclusion of one more racing preparation post 2008 (p < 0.05). Additionally, there was an increasingly ageing population of racehorses. These changes resulted in more race starts in a career, but possibly because of biological constraints, there was no change in the number of race starts per season, starts per preparation, or days spelling between preparations (p < 0.05). There was no change in the proportion of horses having just one race start (14% of new entrants), indicating that the screening for suitability for a racing career remained consistent. These data identify key industry parameters which provide a basis for future modelling of intervention strategies to improve economic performance and reduce horse injury. Consideration of the racing industry as a bio-economic or ecological model provides framework to test how the industry may respond to intervention strategies and signal where changes in system dynamics may alter existing risk factors for injury.