The horse industry in the United States is diverse. Horses are used for racing, competitive riding, showing, recreational riding, and working cattle. Today the number of horses in the United States is estimated at 9.2 million, down from 21 million around 1900, when horses were a primary source of power and transportation, but up from 4.5 million in 1959 (the last time the United States Department of Agriculture counted horses). According to an American Horse Council study, in 2004 the horse industry had a $102-billion impact on the U.S. economy and provided 1.4 million jobs. The horse industry is growing and important. More than ever, we need each horse to be athletically sound and healthy. Consequently, the thrust of equine genetics research on horses during the last half century has been related to health and physiology.

Advances in biotechnology have provided powerful new tools. In 2006, the entire DNA sequence was determined for a Thoroughbred mare. That sequence was assembled and can be viewed online at several Web sites, including Genome.ucsc.edu, Ensembl.org, Ncbi.nlm.nih.gov/genome/guide/horse/index.html, uky.edu/Ag/Horsemap.

In addition, scientists performed partial DNA sequences on seven more horses, including another Thoroughbred, as well as an Akal-Teke, Andalusian, Arabian, Icelandic, Quarter Horse, and Standardbred. Comparing the DNA sequences led to the discovery of more than 1 million genetic differences among these horses. The significance of this work is apparent. Prior to 1990, only 50 genes had known genetic variation; following more than a decade of molecular genetics work on horses, variation had been discovered for an additional 3,000 sites by 2005.

The DNA sequencing work was done by the National Human Genome Research Institute to aid the investigation of human gene function. This work is the largest–ever–single contribution to equine research. DNA sequencing enables studies in all areas of equine research. Those of us working at the University of Kentucky Gluck Equine Research Center played major roles in the development of this resource, and we are well-situated to use the tool and solve problems which have resisted earlier technologies