Microbiome and Dental Changes in Horses Fed a High Soluble Carbohydrate Diet

This study investigated the oral microbiome of horses maintained on a high soluble carbohydrate diet based on sugarcane, in comparison to those fed a pasture-based diet composed of Cynodon spp., aiming to identify associations between dietary intake, the composition of oral microbial communities, and the occurrence of dental caries and diastemata. A total of 20 healthy horses, both male and female, with an average age of 9 ± 3 years and weight of 400 ± 100 kg, without a defined breed, were selected. They were divided into two groups: the High Soluble Carbohydrate Group (HSCCG), consisting of 10 horses fed sugarcane for at least 3 years, and the Low Soluble Carbohydrate Group (LSCCG), consisting of 10 horses fed pasture with Cynodon spp. Dental examinations were performed using an adapted oral endoscope to assess caries and diastemata, and saliva samples were collected for microbiota analysis. Statistical analyses included a Student's t-test and Mann-Whitney test, with significance set at p < 0.05. Horses in the HSCCG had a higher presence of peripheral caries (p = 0.001), as well as differences in the degree (p = 0.010), class (p = 0.05), and presence of diastemata. Microbial diversity indices (Chao, inverse Simpson, and Shannon) showed no significant differences, but the relative abundance differed (p = 0.003). Linear Discriminant Analysis revealed distinct microbial profiles: Candidatus Saccharibacteria and Bacteroidetes were more abundant in the HSCCG, while Cyanobacteria_Chloroplast and Proteobacteria dominated in the LSCCG. Over 35 genera differed significantly between groups. The study concludes that diet plays a significant role in shaping oral microbiota and influencing the development of dental caries in horses.