The Influence of Dietary Energy Source on Microbial Diversity in the Equine Gastrointestinal Tract

Horses are commonly fed diets that contain different sources of energy including starch, fiber and fats. These different energy sources may be digested and absorbed in differing segments of the gastrointestinal tract, thereby altering the gut microbiome. Six mature Miniature Horse geldings (7.5 ± 3.5 yr; 134.5 ± 39.5 kg) were used in a 6 x 6 Latin Square design to evaluate the effect of different dietary energy sources on the microbial diversity of the equine gastrointestinal tract. Diets consisted of mixed grass hay plus one of three energy supplements (oats, beet pulp, rice bran) at two levels (high: 75% supplement/25% hay or low: 40% supplement/60% hay). All diets were identical for digestible energy; however, dry matter intake (DMI) varied. On d 14 of each period, fecal samples were collected and DNA was extracted, pooled by treatment and subjected to PCR-DGGE with primers specific to 16S rRNA gene sequences to evaluate changes in bacterial diversity. PCR-DGGE images were analyzed with BioNumerics software to generate dendrogram comparisons based on the position and number of bands with further evaluation using Principal Coordinate Analysis (PCA). Although there were numerical differences in band counts in the microbial populations evaluated, these data could not be statistically analyzed due to the low sample number (n=1) per treatment group. However, PCA and dendrogram analyses revealed distinct clusters which indicate changes in the microbial profiles of horses fed different energy sources. Further research using species-specific primers is needed.The Ohio State University Department of Animal SciencesNo embargoAcademic Major: Animal Science