Impact of Early Life Turnout on Racing Performance
A fascinating study out of the UK has investigated how early foal management affects racing performance.
The paper, published in the Equine Veterinary Journal, followed 129 Thoroughbred foals across six stud farms in the United Kingdom and Ireland from birth through to the end of their three-year-old racing season. Researchers from the Royal Veterinary College and Cornell University tracked everything — daily turnout time, paddock size, weaning age, veterinary interventions, and eventual race results — to see which early-life factors were actually linked to performance. The key findings were:
Turnout Is Important
Foals that spent more hours per day outside in their first six months of life were significantly more likely to start in at least one race. The predicted probability of making it to the track ranged from around 24% for foals kept in at night consistently (eight hours or less of daily turnout), up to around 70% for those spending closer to 16 hours a day outside, trending toward 24/7 pasture access.
Bigger paddocks also mattered. Foals with more space available during those first six months earned meaningfully more prizemoney, with those in restricted turnout (two acres or less) estimated to earn under £7,000, compared with more than £13,000 for those with access to four or more acres.
The researchers believe the mechanism here is musculoskeletal development. The first six months of life is the fastest period of post-natal growth in Thoroughbreds — foals can reach 43% of adult bodyweight and 83% of adult height during this window. GPS studies of foals at pasture have shown that as grazing time increases, the frequency of high-intensity bouts — cantering, galloping, bucking, rearing — also increases with more space and time outside. These short bursts of intense locomotion appear to drive positive adaptation in bone, tendon, and cartilage during a period when those tissues are highly responsive to mechanical loading.
It's worth noting this aligns closely with the findings from an earlier paper by the same research group, which showed that restricted early-life turnout was also associated with higher rates of musculoskeletal disease and injury between 12 and 18 months of age.
Later Weaning May Be Beneficial
Age at weaning was independently associated with both the likelihood of racing and the total number of race starts. Foals weaned at four months of age had a predicted racing probability of just over 40%, while those weaned at eight months were approaching 90%. In terms of race starts, those weaned earliest averaged four starts by the end of their three-year-old year, while the latest-weaned were predicted to make thirteen.
This may partly be explained by the fact that on all farms in the study, weaning was done abruptly — foals were separated from their dams and often stabled with reduced turnout around this time. So earlier weaning also meant an earlier reduction in those critical hours of outdoor movement. The two factors are tangled together.
But the researchers also point to independent biological reasons why earlier weaning may be harmful. Abrupt weaning is a major stressor, and evidence from both equine and mammalian research suggests early maternal separation can alter hypothalamic-pituitary-adrenal axis function, impair glucose metabolism, and even influence body composition in later life — all of which can affect athletic capacity. Studies comparing bone mineral content in early- versus later-weaned foals have found that early weaning is associated with a measurable reduction in bone mineral gain in the weeks immediately following separation, an effect not seen in later-weaned foals.
In feral horse populations, foals allowed to wean naturally do so at around nine to ten months of age — and seem to show fewer stress responses during the process.
Influence of Genetics
A genuinely thought-provoking result is the following: When stallion and mare were included as random effects in the statistical models — a way of accounting for genetic variation between sires and dams — neither had a significant influence on race performance outcomes once early-life management factors were accounted for.
That's not to say genetics don't matter. But it does suggest that in this population, the environment in which a foal is raised during that critical first six months may have as much, if not more, bearing on whether it ever reaches the track than the pedigree alone. As the authors note, maximising athletic potential likely requires a positive interaction between genes and the environment they're expressed in.
Developmental Orthopaedic Disease
Foals that required veterinary intervention for developmental orthopaedic disease (DOD) in the first two years of life did show lower prizemoney earnings, but once the researchers accounted for turnout area, the independent effect of DOD disappeared. This is an interesting finding: it suggests that much of the deleterious effect attributed to DOD may be equally associated with the management of it. In this study, flexural limb deformities made up 74% of DOD cases, and box rest, restricted turnout, and early weaning are all commonly used in managing these affected foals.
Relevance for Australian Stud Farms
While this study was conducted in the UK and Ireland, the core findings are directly applicable here. Australian Thoroughbred breeding operates in a broadly similar framework, and the biological principles at play — developmental plasticity, musculoskeletal adaptation, weaning stress — are universal.
If anything, the warm climate and longer grazing seasons in most Australian breeding regions mean the opportunity for extensive turnout is even greater than in the UK, where weather often limits outdoor time.
The practical takeaways are:
Prioritise turnout time and space in the first six months of life. Foals need room to move, and they need time to do it. Stabling at night is common practice in the UK, but the data suggest that reducing box time and increasing access to larger paddocks during this window could have measurable effects on career outcomes.
Think carefully about weaning timing. Where management allows, later weaning may be beneficial from a developmental standpoint.
Be prudent when restricting exercise during DOD treatment. Discuss management strategies for DOD with your veterinarian with the goal to return the foal to turnout as early as possible.
A Note on Limitations
Like all observational studies, this one has limitations. The sample size of 129 foals is relatively modest, and the researchers acknowledge that some analyses may have lacked statistical power. Training-related data, which could independently influence race performance, were not available. And race results were largely drawn from British Horseracing Authority databases, which undercounts overseas starts.
That said, the study is the first of its kind to use prospective birth cohort data across multiple farms to examine these questions in Thoroughbreds, and its findings are consistent with the broader body of experimental and observational evidence.
Reference: Mouncey R, de Mestre AM, Arango-Sabogal JC, Verheyen KL. Born to run? Associations between gestational and early-life exposures and later-life performance outcomes in Thoroughbreds. Equine Vet J. 2025. DOI: 10.1111/evj.70084
If you have any questions about early-life foal management or developmental orthopaedic disease, please feel free to reach out to our team at admin@beaequine.com.au.
Return to the homepage.