Horse Gut Microbiome, Behavior & Welfare Study

The study included 185 healthy sport horses recruited from a larger population of 376 horses housed at the French National Riding School in Saumur, France.

The cohort included multiple breeds, sexes, disciplines and performance levels. The mean age was approximately 10.5 years.

Fecal and blood samples were collected at two time points: October 2016 and June 2017, approximately eight months apart.

To be included, horses had remained in the same housing for at least six months before the study and throughout the study period. Horses were required to have no gastrointestinal disorder during the four months before sampling and no antibiotic or immune-modulating treatment during the preceding four months.

Microbiome data were analyzed alongside detailed environmental, equitation, behavioral and host-related measurements to identify variables associated with between-horse and within-horse microbial variation over time.

There was no nutritional or microbiome intervention; this was a longitudinal observational study.

Fecal microbial communities were characterized at two time points using sequencing of the V3–V4 region of the bacterial 16S rRNA gene.

The sequencing generated more than 13 million high-quality reads and identified 15,154 filtered operational taxonomic units.

The researchers simultaneously examined 41 environmental and host-related variables. These included equitation specialty and discipline, diet, housing and bedding, age, sex, body condition, parasite status, fecal pH, fungal and protozoal loads, hematological measurements and behavioral indicators.

Behavioral observations included oral and locomotor stereotypies, unresponsiveness to the environment, hypervigilance and aggressiveness.

Statistical analyses were then used to determine which variables were associated with differences in microbial community composition and to estimate microbiability for selected host traits.