The gene responsible for causing the swaybacked appearance of many American Saddlebred horses might be playing an advanced game of "hide and go seek," but genetic researchers at the University of Kentucky's Gluck Equine Research Center are one step closer to uncovering this gene and, thus, helping breeders one day avoid perpetuating the trait.

Swayback, also referred to as lordosis, lowback, or softback, is the excessive curvature of the spine.

According to Gluck scientist Ernest Bailey, PhD, who studies immunogenetics and genomics and is a co-author on the study, a former doctoral student in his program laid the groundwork for the recent study in 2003 , demonstrating that swayback had a hereditary basis in Saddlebreds.

Researchers have shown that extreme lordosis is associated with pathology (physical damage to the spinal cord and associated tendons, ligaments, and other anatomic structures).

"If the gene or genes responsible for extreme lordosis in the American Saddlebred could be determined, then breeders would have a better understanding of the condition and be able to use this information in their breeding programs," noted Bailey.

To help elucidate the genetic causes of swayback in Saddlebreds, Bailey's graduate student Deborah Cook analyzed entire genomes of 20 affected and 20 unaffected horses. She noted one genetic marker was significantly associated with the presence of swayback, suggesting a region on Chromosome 20 possessed a gene that could cause inheritance; 17 of the 20 affected horses had t