The effects of signalment, diet, geographic location, season, and colitis associated with antimicrobial use or Salmonella infection on the fecal microbiome of horses.

The research explores the impact of various factors such as dietary intake, environment, and specific diseases on the fecal microbiome of horses, concluding that while diet can affect the fecal microbiome, an encounter with diseases like colitis has a more significant influence.

Introduction and Objectives

• The study’s broad objective is to evaluate how variables such as age, breed, sex, location, changing seasons, and diet, along with diseases such as antimicrobial-associated diarrhea (AAD) and salmonella infection influence the fecal microbiota of horses.
• The research particularly focuses on healthy horses, horses suffering from AAD (diarrhea caused by the use of antibiotics), and those infected with Salmonella.

Methodology

• The sample consisted of 80 healthy horses from various geographical locations in the U.S., 14 horses affected by AAD, and 12 horses exhibiting spontaneous colitis and tested positive for Salmonella infection.
• The horses were all above one year old and their diets were classified on a scale including forages (pasture and hay) and differentially fibered and portioned concentrates.
• DNA was extracted from the fecal matter and subjected to Illumina sequencing of 16S rRNA genes to identify the gut microbiota present.

Results

• Findings show that changes in the microbiome were observed in healthy horses depending on the grain diet they were fed: those fed higher amounts of grain had different clusters of bacteria than those fed lower amounts.
• AAD and Salmonella-infected horses had reduced “richness and evenness” of fecal microbiota in comparison to healthy horses.
• In AAD horses, there was an increased prevalence of Bacteroidetes and Proteobacteria and a decrease in Verrucomicrobia. Salmonella-infected horses, however, had lesser Firmicutes when compared to healthy horses.

Conclusions

• The outcomes suggest that dietary factors do impact the horse’s fecal microbiome, particularly the quantity of grain consumed.
• However, the research concludes that the presence of diseases like colitis has a much more substantial impact on the fecal microbiome.
• It was further observed that the impact on microbiome was more severe in horses with ADD as compared to those infected with Salmonella.