Can Gut Microbiota Predict Successful Racehorses?

Each year, over five million people attend British racecourses, generating billions of pounds for the economy and making horse racing the second biggest spectator sport in the UK.

With this in mind, the health and welfare of the horses are paramount, and research often focuses on minimizing the potential for injury and disease while boosting the horse's athletic performance.

Many attempt to train a champion through regular exercise plans, a well-thought-out diet, and regular health checkups for their adult horse, but a recent study suggests that a racehorse’s potential for success can actually be determined much earlier than this, when the horse is merely a foal. 

In this blog, we discuss a recent paper by Leng et al. (2024), which investigates how the gut microbiota of foals in the first few months of life predicts their athletic performance and risk of disease in later life.

The Formative Years

While bacteria, viruses, and fungi are often thought of as the villains in the story of health and disease, trillions of microbes — referred to as the microbiota — inhabit our bodies and have more positive impacts than you may realize. The majority of microbiota reside in the gut, where they facilitate digestion, maintain metabolic homeostasis, and prevent the invasion of more nefarious microbes (Pickard et al. 2017). 

Not only is a healthy gut microbiome important in the here and now, but several studies have shown the relationship between dysbiosis — imbalances in the microbiota — in early life and health impacts in later life. Diseases, such as asthma, diabetes, and cardiovascular diseases, to name a few, have been linked to alterations in these benevolent gut microbe populations. Such imbalances can be caused by factors like diet, the use of antibiotics, and even geographical location (Sarkar et al. 2021).

The diversity of the microbiota in foals has been previously investigated. Shortly after birth, a transient, unstable microbiota colonizes the gut, which is highly susceptible to changes in the environment. This highly dynamic nature of the microbial populations tends to settle at around day 50 post-partum, when significant changes in the species abundance are no longer observed (Lindenberg et al. 2019).

So, could changes in the microbiota during this vulnerable period in early life impact the success of a racehorse in later life?

The Proof Is in the Poo

Leng et al. sought to investigate this question by utilizing a cohort of 52 thoroughbred foals, specifically bred for racing, and studying them until they were three years old. The gut microbiota of the animals was assessed by collecting fecal samples at nine timepoints within the first year of life (2, 8, 14, 28, 60, 90, 180, 272, and 365 days after birth) and performing 16S rRNA gene sequencing to identify microbial diversity.

Alongside the fecal samples, the horses' health and athletic performance were also tracked. Weekly health updates assessing any respiratory, gastrointestinal, orthopedic, or soft tissue issues were recorded, and results from participation in regulated horse races were acquired.

The researchers found that foals with low bacterial diversity in the gut in early life had significantly higher incidence rates of respiratory, orthopedic, and soft tissue health events. In particular, the association was strongest for respiratory disease.

When analyzing athletic performance, significant positive associations were observed between microbial diversity at 28 days and the three outcomes measured: average prize money earnings, average race placings, and official rating — a handicap metric given to a horse by the regulatory authority based on their performance across multiple races.

The scientists also explored how the use of antimicrobial treatment in early life impacted health and performance. Treatment with antimicrobials, particularly antibiotics, has previously been shown to impact gut microbiota, leading to pathologies such as asthma and infectious diseases (Pilmis et al. 2020).

In the present study, they found that, as anticipated, foals administered with antimicrobials within the first month of life had significantly lower bacterial diversity. Interestingly, antimicrobial use was also associated with significantly lower average prize money earnings in their racing careers and an augmented risk of respiratory disease. The official rating of horses that had received antimicrobials as foals was also lower than those that had not, however, this was not statistically significant.

As of yet, the reason why gut diversity at 28 days old in foals influences the respiratory health and athleticism of the horse in later life remains unknown. The authors of the study suggest that future research could focus on further illuminating how certain factors, such as the mother’s diet, milk composition, and health history, impact microbial diversity in foals.

 Overall, this study provides evidence for interventions in early life to support the rearing of superior equine athletes, including maintaining a balanced gut microbiota and avoiding antimicrobials where possible.

So, it appears that a healthy gut is the dark horse in this race!