Study Shows Proper Storage and Shipment of Semen Is Important for AI Breeding
Artificial insemination (AI) gives breeders an opportunity to breed dogs that otherwise might not be possible due to geographical location, behavior incompatibilities or other factors. A recent study examined whether antibiotics added to commercial semen extenders to increase shelf life inhibit the growth of bacteria in semen samples.
“Breeders are not shipping females for natural breeding as much today and thus are turning more to AI,” says Ginny Altman, vice president of the American German Shepherd Dog Charitable Foundation. “Since semen collection introduces bacteria into the semen sample from normal bacterial flora, we wanted to learn whether the antibiotics used in extenders control the growth of bacteria.”
The study,1 funded by the AKC Canine Health Foundation with support from the American German Shepherd Dog Charitable Foundation, was led by Carla Barstow, DVM, and Margaret Root Kustritz, DVM, PhD, DACT, professor of small animal reproduction at the University of Minnesota College of Veterinary Medicine. They recruited 14 male dogs from members of all-breed clubs in the Minneapolis area. Included were six Samoyeds, six Malamutes, one English Springer Spaniel, and one Labrador Retriever, ranging from 2 to 9 years of age.
“We hypothesized that the growth of aerobic, anaerobic and Mycoplasma bacteria would be controlled in semen extended with commercial canine extenders when stored at refrigerator or room temperatures for up to 48 hours,” Barstow says.
“Our study was intended to mimic what can happen in the real world. It is important for the receiving veterinarian who will do the AI procedure and the brood bitch owner to know that the semen product they are using is safe. In reality, manufacturers include antibiotics in extenders to prolong shelf life, not inhibit bacterial growth.”
Commercial semen extenders are used with chilled and frozen semen. Extenders are liquid media that support spermatozoa by providing nutrients and a buffering capacity to offset changes in temperature that occur during storing and shipping.2
Chilled semen must be shipped and inseminated in a bitch within 24 hours of collection to retain viability and reduce the risk of disease. In addition to normal bacterial flora from a male dog’s urethra, semen can be infected from urine in the urethra and organisms that are shed from prostatic or testicular fluid caused by systemic infection.
Preventing disease transmission by AI will protect bitches only if an antibiotic is added to the semen. Two commercial canine extenders commonly used by theriogenologists, or reproduction specialists, were tested in the study. One extender contains several antibiotics, and the other has a single antibiotic.
“Semen shipments may have been sitting on a hot truck all day with melted ice packs,” Barstow says. “Worse yet, they may have been left in an uncontrolled environment in which you have no idea whether the box was opened or whether the ice packs were left in place.”
In the study, each semen sample was separated into 11 samples. Three cultures, considered neat samples, had no extender added and were tested for anaerobic, aerobic and Mycoplasma bacteria. The remaining semen was separated into two groups for adding the respective extender products. The individual extender groups were stored at room temperature (20 degrees Celsius) or refrigeration temperature (5 degrees Celsius) and tested for aerobic and Mycoplasma bacteria at collection, 24 hours and 48 hours.
“We noted an expected motility loss in the first 24 hours,” says Barstow. “We also found that the motility of spermatozoa was not affected by the presence of bacteria, thus motility is not a measure to determine whether a sample contains bacteria.”
Related to bacterial growth, 35 percent of dogs had significant growth of bacteria in their semen, which is in accord with information from the literature, Barstow says. Bacterial growth was controlled in samples that were held at refrigeration temperature, but not in all the samples that were held at room temperature.
“Importantly, there was no significant growth in any refrigerated sample, which is the protocol for shipping chilled semen samples,” she says. “The question was whether extenders work as we thought they did, and yes, we showed they do.”
1 Barstow C, Root Kustritz MV. Effects of Antibacterial Agents in Semen Extender on Bacterial Growth in Extended Canine Semen Held at 5°C or 20°C for Up to 48 Hours. Clin Therio J. 2014;6:231-237.
2 Root Kustritz MV. The Dog Breeder’s Guide to Successful Breeding and Health Management.
St. Louis: Saunders Elsevier. 2006.