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


OBJECTIVE
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
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.
Massey Equine, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand. J.C.Tanner@massey.ac.nz
J C
JC
Tanner
C W
CW
Rogers
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EC
Firth
D000375:Aging; D000818:Animals; D005260:Female; D006736:Horses / Q000502:physiology*; D008297:Male; D009520:New Zealand; D010805:Physical Conditioning, Animal / Q000502:physiology*; D012420:Running; D013177:Sports