Illumina sequencing of the V4 hypervariable region 16S rRNA gene reveals extensive changes in bacterial communities in the cecum following carbohydrate oral infusion and development of early-stage acute laminitis in the horse.

The study uses metagenomic methods to analyze changes in the bacterial communities found in a horse’s cecum after carbohydrate infusion and the development of early-stage acute laminitis. It was found that the relative abundance of certain Gram-positive and Gram-negative bacteria significantly increased, with decreases in normal flora, suggesting an overgrowth of pathogenic bacteria potentially contributing to enterocolitis, pyrexia, and lameness in laminitis induced by carbohydrate overload.

Study Design and Methodology

• Using the equine carbohydrate overload model of acute laminitis, the researchers investigated changes in bacterial communities within the cecum of horses.
• The horses were divided into groups, including control non-laminitic (8 horses), and laminitic induced with oligofructan (6 horses) or cornstarch (6 horses).
• Metagenomic methods were employed, sequencing the V4 hypervariable region of the 16S rRNA gene from microbiota in cecal fluid taken from the horses in each group.

Key Findings

• An upsurge in the relative abundance of Gram-positive bacteria, specifically Lactobacillus sp. and Streptococcus sp., was observed after both oligofructan and cornstarch infusion.
• Increased prevalence of potentially harmful Gram-negative bacteria, specifically Veillonella sp. and Serratia sp., was also found.
• The study recorded substantial decreases in the relative abundance of assumed normal flora in the horse’s cecum.

Interpretations and Conclusions

• Changes in the bacterial communities in the cecum play a role in the progression of early-stage acute laminitis in horses.
• The study proposes that the excess of pathogenic Gram-negative bacteria might cause enterocolitis, pyrexia, and lameness seen in the carbohydrate overload model of acute laminitis. However, as this is a pilot study, further research is needed to validate this hypothesis.
• The research presents valuable initial data for exploring the microbial dynamics in the equine gut and highlights the potential risks of carbohydrate overload in horses.