Phenotypic and genetic factors that affect the likelihood of Standardbred foals achieving a race start

This study was conducted to quantify the probability of a Standardbred foal attaining early career milestones and to estimate some environmental and genetic factors that influence achievement of those milestones. Data for all Standardbred foals registered at birth in New Zealand from 1995 to 2018 were used to estimate variance components and fixed effects influencing attainment of three early-career traits; registered with trainer (REG), starting in a trial (TRIAL) and starting in a race (RACE). The study population comprised 65,256 foals. Of these, 65.5% attained REG, 55.4% progressed to TRIAL and 45.9% commenced racing. The phenotypic variance (V_p) for REG was 0.212 with an additive genetic variance (V_a) of 0.025 ± 0.002 and the owner component was 0.023 ± 0.001. V_p for TRIAL was 0.126 with the trainer variance component (V_t) (0.021 ± 0.001) exceeding the V_a 0.016 ± 0.002. V_p for RACE was 0.205 with V_t (0.021 ± 0.001) exceeding V_a 0.016 ± 0.002. Horse sex, gait, birth month and sire stud fee influenced the likelihood of a foal attaining each milestone. Attainment of early career milestones in Standardbred horses reflects the combined influence of genetic, management and industry factors.