The Thoroughbred Birth Cohort

26/09/2025

Delighted to share our latest publication available today free open access in Vet Record http://doi.org/10.1002/vetr.5777 describing racing and training outcomes, population dynamics, and horses' destinations over the 4-year study period.

Importantly, our findings suggest that wastage due to failure to train and race may be significantly lower than industry-level estimates suggest, highlighting potential traceability gaps at this level, most likely due to the dynamic nature of Thoroughbred populations.

Key findings:
- Thoroughbred populations are highly dynamic, leading to traceability gaps at industry-level that may inflate wastage estimates.

- Individual horse-level follow-up suggests that the majority of Thoroughbreds bred for racing enter training and appear on a racecourse.

- A better-defined target population, enhanced data integration, and cross-industry collaboration could improve traceability and help maintain social licence.

This study provides up-to-date benchmarking of the population dynamics of Thoroughbreds bred for flat racing and novel estimates of attainment of career milestones. Findings can directly inform industry traceability strategies that will help maintain its social licence to operate.

Background Analyses of industry-level data suggest that around one-third of the UK and Ireland Thoroughbred foal crop fail to enter training. Prospective follow-up of individual horses could provide...

02/09/2025

Delighted to share another new publication available free open access in Equine Veterinary Journal. This time from a collaboration with Rossdales Laboratories, Camilla Scott, Billy Fehin, Mandi De Mestre and Juan Carlos Arango-Sabogal, through which we have published a series of papers describing the prevalence of bacterial isolates and antimicrobial resistance in endometrial swab samples, and evaluated the accuracy of cytology and culture to diagnose endometritis in Thoroughbred broodmares.

In this study we investigated associations between pre-breeding endometrial swab findings and live-foal rates, using data from over 7,500 endometrial swab samples submitted to the laboratory over 7 breeding seasons.

This is the first study to use multivariable modelling methods to investigate associations between endometrial swab findings and live-foal rates in Thoroughbred broodmares, identifying novel and important relationships.

Key findings:

🐎 In contrast to other categories of bacterial isolate, mares with a profuse growth of Escherichia coli had significantly lower live-foal rates compared to those with no growth.

🐎 There was interaction between mares' age and cytology.
🐎 In mares >12 years of age, significant reductions in live-foal rates were observed between mares with >30% PMN and mares with ≤0.5% PMN.
🐎 In mares ≤12 years of age, live-foal rates were not significantly different between categories of PMN ( ≤0.5% PMN; 0.5%–5% PMN; >5%–30% PMN; >30% PMN:endometrial cells per high power field).

Take home messages:

👉 In young mares, endometrial inflammation (% PMN) appears less likely to impact fertility outcomes and, therefore, beyond the ruling out of venereal transmissible infections, an endometrial culture and cytology may be of somewhat limited value in young, clinically normal individuals.

👉 Conversely, the value of identifying and instituting effective reproductive management around the time of breeding in mares >12 years of age with evidence of a marked endometrial inflammatory response and in mares with profuse E. coli cultures cannot be understated.

👉 Critically, and in contrast to previous studies, through the evaluation of endometrial bacteriology species and growth separately, our findings have refined current knowledge and identified an important subset of mares with a profuse growth of E. coli, in which important knowledge gaps exist around the aetiologies underlying their poorer fertility outcomes.

http://doi.org/10.1111/evj.70086

26/08/2025

We are delighted to share the latest publication from our Horserace Betting Levy Board and Racing Foundation funded Thoroughbred birth cohort study, which is available online today free open access in Equine Veterinary Journal.

The study is first of its type to evaluate the effect of early-life experiences, in particular turn out and management practices, on later-life performance in a UK field setting. Our findings can be directly applied at the stud farm-level to help retain Thoroughbreds within the industry and achieve their athletic potential - outcomes that importantly align with priorities of the Horse Welfare Board's strategy to support the welfare of horses bred for racing.

Key findings:

🐎 Foals that spent more time turned out at pasture in the first six months of life, and foals that were weaned at an older age, were more likely to race at least once by the end of their fourth year of life (3-yo year).

🐎 The older the foals were at weaning, the greater number of race starts they made.

🐎 Foals that were turned out in larger paddocks during the first six months of life earned more prizemoney.

Take home messages:

👉 The first six months of life are a critical period of development in Thoroughbreds, during which it is essential that turnout and weaning practices provide sufficient opportunity for positive tissue adaptation and optimal development.

👉 Breeders are therefore encouraged to maximise turnout whenever possible and to consider weaning after this critical period, particularly in flat race-bred individuals where 2- and 3-yo performance is key.

For more information visit;

Background Gestational and early-life exposures may modulate development during growth and influence future athletic performance. Objectives To investigate associations between gestational and ear...

24/06/2024

Rebecca shared findings from our research at the Beaufort Cottage Educational Trust Gerald Leigh memorial lectures in Newmarket, which are now available to watch online. There was a great line up of speakers discussing strategies to optimise young stock growth and development.

Optimising Youngstock Growth and Development The Gerald Leigh Lectures were once again held at the Sales Paddocks, Newmarket on the 12th June 2024 by kind permission of Tattersalls. Gerald Leigh was a prominent owner breeder of racehorses based at Eydon Hall Farm in Northamptonshire. He established....

13/06/2024

Delighted to share our latest publication, in which we undertook hedonic price modelling of Tattersalls sales data to investigate determinants of Thoroughbred yearling sales price and evaluate the role of stallion covering fee, available in Vet Record online. http://dx.doi.org/10.1002/vro2.81

Findings can inform breeding decisions to maximise profitability, give context for current industry strategies and can inform valuations of breeding stock.

The Thoroughbred Breeders' Association
The Royal Veterinary College (RVC)
Thoroughbred Daily News

Veterinary Record Open is an open access journal dedicated to publishing specialist veterinary research across a range of topic areas from all veterinary disciplines.

04/03/2024

Thank you to Vet Record for featuring our latest research in this weeks selected highlights from other journals https://doi.org/10.1002/vetr.4017

TURNOUT PRACTICES INFLUENCE FOALS' FUTURE MUSCULOSKELETAL INJURY RISK
R Mouncey, J Arango-Sabogal, A de Mestre and others
Equine Veterinary Journal (2023)
doi: 10.1111/evj.14038

More extensive preweaning turnout practices reduce thoroughbred foals' risk of future musculoskeletal disease and injury

• What did the research find?
The overall incidence of musculoskeletal disease/injury in this cohort was 5.3 cases per 100 foal months at risk. Compared with foals turned out 24/7, those with average daily turnout times of between nine and 23 hours over a seven-day period had a 4.6-fold increase in their risk of musculoskeletal disease/injury (P

Veterinary Record is the official journal of the British Veterinary Association, publishing original research, reviews, and news on a wide range of veterinary topics.