You know the drill: Kill the bacterium that’s attacking the immune system then prepare yourself for the relentless fungus to come out and play in its wake. This bug balance upheaval is the reason we reach for yogurt when we go on antibiotics or we pursue a probiotic supplement if we start feeling "off." Some owners apply similar strategies when caring for horses. But one veterinarian believes it’s not just a matter of wrangling fluctuations of one or two bugs at a time; diversity among our horses’ microflora could be far greater than we’ve imagined, and addressing that balance might prove a bit more complex.

Scott Weese, DVM, DVSc, Dipl. ACVIM, a professor in the Department of Pathobiology at the University of Guelph’s Ontario Veterinary College, presented on the concept of microbiomes and their function at the Ninth International Conference on Equine Infectious Diseases, held in October 2012 in Lexington, Ky.

He defined a microbiome as the totality of microbes, their genomes, and interactions in a particular environment. A microbiome comprises different microbial "communities" on different sites of an organism’s body–for example, nasal passages, oral cavities, skin, and various organs–and researchers are examining these communities’ function in health and disease in a number of species. Weese and his team are focusing on horses.

Veterinarians know very little about the equine microbiome, he admitted, but with new technology they’re starting to understand its complexity and diversity. When his team examined the microflora in the hindguts of normal, healthy horses and those with idiopathic colitis (unexplained inflammation of the colon), they noticed "rather remarkable differences between our normal and our diarrheic horses