Career profile of the Canadian Standardbred. III. Influence of temporary absence from racing and season.

The objective of the study was to examine the career profile of the average racehorse in order to establish normal values for performance. Records of race performance for a population of 762 horses randomly selected from the 1972 registrations of the Canadian Standardbred Horse Society were summarized and the pattern of racing by year and month from 1974 to 1983 inclusive recorded. Results were analyzed to determine the influence of sex, gait, age, and year of first race (starting year). The transformation log (1 + X) was used to achieve normality where necessary. Of the 762 horses, 507 raced, 56 (11.0%) of which took one or more complete seasons (years) off. No age predisposition was detected, and no significant difference in mean career performance between the group taking a season off and the remaining horses were found, with the exception of career length, which was longer for those temporarily absent from racing (p less than 0.001). No influence upon career pattern for horses off early in their career was observed but those off late showed indications of a subsequent fall in number of races per year and in times for the mile. Mean career duration was 25.66 to 28.38 months (95% confidence limits for the mean, n = 507). Absence from racing of at least one months duration was taken by 437 horses, mean percentage of career off 42.36 +/- 0.94% (mean +/- SEM), mean duration of periods off 4.43 to 4.71 months. Career duration in months and percentage off were only weakly related (r = -0.16).(ABSTRACT TRUNCATED AT 250 WORDS)