The success of a racehorse may rely on its gut microbiome in early life

Racehorses who have a more diverse gut microbiome as foals appear to perform better and have a lower risk of health complications.

The findings suggest that, as suspected in humans, there are critical periods in the horse’s gut microbiome for establishing a bacterial composition that may contribute to an individual’s long-term health and fitness.

Christopher Proudman Researchers from the University of Surrey in the UK analysed DNA sequences from fecal samples from 52 thoroughbred foals born at five stud farms in 2018.

The researchers took samples nine times over the first year of life: at 2, 8, 14 and 28 days of age, and at 2, 3, 6, 9 and 12 months of age. Once the animals were a year old, they were transferred to 29 racing training centres across the UK.

The researchers then measured the athletic performance of the two- and three-year-old horses during the races, and collected data on rankings and total prize money, as well as recording the horses’ respiratory systems, orthopedic health, and soft tissue health.

The team found that greater bacterial diversity at 28 days of age was associated with better performance in the race. The researchers also detected two bacterial families: Anaeroplasmataceae and Bacillaceae was associated with having a competitive advantage.

In contrast, low bacterial diversity at 1, 2 and 9 months of age was found to be associated with an increased risk of orthopedic and other problems, such as muscle strains and “hairline” fractures. The team also found that certain bacterial families, when abundant around the first week or two of life, were associated with an increased risk of respiratory and musculoskeletal diseases later in life.

Foals treated with antibiotics (which can affect gut microbiomes) during the first few weeks of life had significantly lower bacterial diversity than untreated foals at day 28, Proudman said. These animals subsequently produced fewer winnings and developed respiratory disease at 10 times the rate of untreated foals from age 6 months onwards.

The early health problems that prompted antibiotic treatment may have actually affected later performance and health. Simon Daniels Researchers from the Royal Agricultural University in Gloucestershire, UK, say it’s realistic to think that antibiotics themselves reduce bacterial diversity, leading to poorer health and performance.

“Although more evidence is needed before any firm conclusions can be drawn, it appears that how young horses are managed is particularly important for their later athletic performance,” Daniels says.