 The purpose of this study was to compare the digestibility of grass hay, fecal and plasma volatile fatty acid, VFA, concentrations, and fecal bacterial abundance in overweight and moderate-conditioned mares. Overall, no significant differences were found in any of these parameters between the two groups. However, mean plasma acetate concentration was significantly higher in overweight mares compared to moderate-conditioned mares. This suggests that there may be a link between gut microbes and obesity in horses. This article was authored by Megan L. Shepherd, Monica A. Ponder, Amy O. Burke and others.