Thermotemporal dynamics of contaminant bacteria and antimicrobials in extended porcine semen G.C. Althouse * , M.S. Pierdon, K.G. Lu Department of Clinical Studies, New Bolton Center, University of Pennsylvania, 382 West Street Road, Kennett Square, PA 19348-1692, USA Abstract Bacterial contamination of extended porcine semen has been associated with deleterious effects on both semen quality and sow fertility. Retrospective, prospective and in vitro studies were performed to delineate the prevalence and behavior of certain bacterial contaminants in extended semen, and antimicrobial pharmacodynamics in various semen diluents. Retrospective review of extended semen samples submitted from North American boar studs for microbiological screening at the University of Pennsylvania Reference Andrology Laboratory in 2005 and 2006 yielded bacteriospermia prevalence rates of 17% (144/832) and 26% (256/984), respectively. In a prospective study of regional boar studs, of 91 extended semen samples tested over 1-y, 29% were positive for bacteriospermia. Retrospective and prospective studies both showed that the preponderance of contaminant positive samples occurred during the fall months (P < 0.05). To better understand behavior of select contaminant bacteria, generation intervals were determined for Serratia marcescens (SM) and Achromobacter xylosoxidans (AX) at 16, 22 and 37 8C. Generation times were temperature-dependent, with intervals decreasing two- to four-fold as incubation temperature increased. Growth patterns for SM, AX and Burkholderia cepacia were evaluated in various semen diluents. The different diluents exhibited constant or episodic patterns of growth within and among bacteria throughout the 5-d test period. Kill-time kinetics at 37 8C of several genera of bacteria in four semen diluents containing amoxicillin, gentamicin, tylosin, and lincomycin/spectinomycin (single drug or combination) ranged from 75 to over 360 min, and was highly dependent (P < 0.05) upon both type of bacteria and semen diluent. # 2008 Elsevier Inc. All rights reserved. Keywords: Bacteriospermia; Porcine semen; Semen extenders; Antimicrobials; Temperature 1. Introduction The global swine industry has made an effort to actively embrace certain assisted reproductive technol- ogies at the genetic nucleus and commercial farm level; the most common of these technologies currently utilized on most swine breeding farms is AI. Due in part to biosecurity concerns and scales of efficiency, extended porcine semen is collected and processed at dedicated boar studs and then delivered by ground or mail courier to the breeding farm. Depending upon sow management, courier availability and cost, extended semen delivery frequency can vary. These factors have led to the development and use of a multitude of currently marketed short- to long-term semen extenders that purport to maintain sperm viability for intervals as long as several days. The chance of bacterially contaminated extended porcine semen doses being produced has increased as www.theriojournal.com Available online at www.sciencedirect.com Theriogenology 70 (2008) 1317–1323 * Corresponding author. Tel.: +1 610 925 6320; fax: +1 610 925 8134. E-mail address: gca@vet.upenn.edu (G.C. Althouse). 0093-691X/$ – see front matter # 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.theriogenology.2008.07.010