The relationship of training milestones with racing success in a population of Standardbred horses in New Zealand.

Abstract: To investigate the association between attainment of training milestones by 2-year-old horses with racing outcomes in a population of Standardbred racehorses in New Zealand. Methods: Retrospective records of the 2001/2002-born Standardbred foals were obtained. The three training milestones used were: registered with a trainer, entered in a trial, and competed in a race. The racing outcomes were length of career in years raced and number of race starts, and total earnings. Cox regression analysis was used to assess the association between attainment of the three milestones by 2-year-olds and the number of race starts and years raced. Logistic regression models were used to determine the association between attainment of the milestones by 2-year-olds and the outcomes won and placed in a race. Linear regression was used to model the association between attainment of the milestones by 2-year-olds and annual earnings and total earnings (transformed using Ln (earnings+NZ$100)). Results: Of 3,032 horses in the population, 1,018 (33.6%) registered with a trainer, 609 (20.1%) trialled, and 272 (9.0%) raced as 2-year-olds. Horses that first raced as 2-year-olds had a longer racing career and more race starts than those that that did not race as 2-year-olds (p<0.001); this was also true when starts in the 2-year-olds were omitted from analyses. Horses that were registered with a trainer, trialled or raced as 2-year-olds were more likely to have won or placed in a race than those that did not achieve the milestones as 2-year-olds (p<0.001). Linear regression showed horses that trialled and raced as 2-year-olds had greater total earnings than those that did not, and male horses had a greater total earnings than female horses. Conclusions: Only one third the Standardbred racehorses born in 2001/2002 registered with a trainer as 2-year-olds, but the results of this study indicate that horses that began training, trialling, or racing as 2-year-olds had longer and more successful careers than those that did not achieve the milestones as 2-year-olds. Further investigation is required to quantify the management practices of these horses to determine the factors that may be associated with a successful racing career.