The use of cooled and frozen semen has, quite literally, given breeders a world of stallions to choose from when selecting a mate for their mares. These products also allow veterinarians to inseminate mares at the ideal time in her estrous cycle, regardless of whether the stud resides around the corner or across the ocean.

But there are still kinks in the system, and mare owners are sometimes disappointed when the semen fails to result in a pregnancy. Fortunately, there are steps veterinarians and stallion managers can take to help improve the quality of cooled and frozen semen.

At the 2015 World Equine Veterinary Association Congress, held Oct. 8-10 in Guadalajara, Mexico, Ed Squires, MS, PhD, Dipl. ACT (Hon), reviewed some of those methods. Squires is a professor at the University of Kentucky’s Gluck Equine Research Center, in Lexington.

Cooled Semen

“Even under ideal conditions, not all stallions have sperm that will survive cooling and storage,” Squires explained. “However, there are some common mistakes made in processing and shipping cooled semen that can adversely affect fertility.”

First, veterinarians and technicians need the appropriate equipment with which to evaluate semen and ship it properly.

“One must accurately be able to determine sperm concentration using a sperm counter and evaluate motility (movement) using a phase-contrast, heated-stage microscope,” he said.

For shipping, sperm should be diluted in an extender to a concentration of 25 to 50 million per milliliter, Squires said. “Generally 1 billion sperm are shipped in a volume of 40 milliliter