Effect of Antibacterial Agents in Semen Extender on Bacterial Growth in Extended Canine Semen Held at 5°C and 20°C for Up to 48 Hours

It has long been believed by some theriogenologists and dog breeders that the antibiotics in commercial semen extenders would control the growth of bacteria introduced with the semen sample. However, manufacturers include those antibiotics to prolong the product shelf life, not for the inhibition of bacterial growth. We hypothesized that the growth of aerobic, anaerobic and Mycoplasma species will be controlled in semen extended with commercial canine extender when held at refrigerator (5°C) or room (20°C) temperatures for up to 48 hours. Semen was collected by manual ejaculation from 14 dogs and the semen split into 11 aliquots. One aliquot each was submitted for aerobic, anaerobic, and mycoplasma cultures. Half of the remaining semen from each dog was extended 1:1 by volume with Fresh Express® (Synbiotics, Kansas City, MO) and the other half was extended 1:1 by volume with CaniPro™ ApX2 Chill 5 (Minitube, Verona, WI). The extended semen was submitted for all three cultures immediately after addition of extender, and at 24 and at 48 hours after extension; half of the semen in each extender was held at 5°C and the rest at 20°C. Bacterial growth was compared between extenders, between storage temperatures, and over time. There was no significant growth in any sample held at 50 C. There was bacterial growth in some samples held at room temperature. Percentage progressively motile spermatozoa in a given sample is not a reflection of bacterial growth in the sample. […]