Removal of bacteria from boar semen using a low-density colloid

P. 272-278 Antibiotics are added to semen extenders when preparing commercial semen doses for artificial insemination according to national and international guidelines. However, this addition of antibiotics represents non-therapeutic usage and could be contributing to the development of antibiotic resistance. Colloid centrifugation was shown to reduce the load of bacteria present in boar semen and was capable of removing all bacteria if performed directly after semen collection, albeit with some loss of spermatozoa. The present experiment was conducted with a low density colloid to investigate whether it was possible to separate all of the spermatozoa from seminal plasma i.e. without selection for robust spermatozoa, or whether this would have a detrimental effect on sperm quality. Ejaculates from nine boars were extended in Beltsville Thawing Solution without antibiotics and were transported to the laboratory for Single Layer Centrifugation (SLC) on modified Porcicoll i.e. at a low density (S). A further modification was that a sterile inner tube was included inside some of the 50 mL centrifuge tubes to facilitate harvesting of the sperm pellet (M). Aliquots of all samples (control, S and M) were cultured for bacterial quantification and identification using standard microbiological methods. Sperm quality was evaluated daily. Three of the C and M samples and five of the S samples did not contain any bacteria. Mean bacterial counts for the remaining samples (colony forming units/mL) were as follows: C 259 ± 216; S 30 ± 22; M 33 ± 15 (P