In the study, the researchers compared T. equigenitalis growth in raw semen from a CEM-positive stallion and the same semen extended in media containing antibiotics. | Photo: Anne M. Eberhardt/The Horse

Researchers from the University of Kentucky Gluck Equine Research Center recently investigated whether antibiotics in a semen extender could inhibit the growth of the bacteria Tayorella equigenitalis, which causes contagious equine metritis (CEM), and escape detection of the bacteria in horses bred by artificial insemination.

CEM has a devastating effect on fertility; it is a very costly and serious disease in horse operations that practice natural cover. The United States has largely been considered CEM-free since 1978, when an outbreak occurred in Kentucky with significant costs to the Thoroughbred industry. Importation regulations currently apply to horses imported from countries considered endemic for the disease.

“Although there is no current threat to the U.S. horse population, it always raises concerns that imported horses may bring the disease into the U.S.,” said Mats Troedsson, DVM, PhD, Dipl. ACT, director of the Gluck Center and chair and of the Department of Veterinary Science