How do different concentrations of Clostridium perfringens affect the quality of extended boar spermatozoa?

Bacteriospermia in boar fresh and extended semen is a frequent finding that produces alterations on sperm quality and, consequently, causes economic losses in artificial insemination (AI) centres. The present study sought to evaluate the effect of different infective concentrations of Clostridium perfringens on boar sperm quality, assessed as sperm motility (CASA), morphology and viability, through 11 days of storage at 15 °C (experiment 1), and after 96 h of incubation at 37 °C (experiment 2). With this purpose, different seminal doses were artificially inoculated with different infective concentrations of C. perfringens, ranging from 102 to 108 cfu mL−1. The negative controls were non-inoculated doses. Sperm quality was checked after 0, 1, 2, 3, 4, 7, 8, 9, 10 and 11 days of storage at 15 °C in experiment 1, and after 0, 24, 48, 72 and 96 h at 37 °C in the second experiment. Moreover, the presence/absence of bacteria was detected by PCR analyses during both experiments at different time points.In both experiments, sperm morphology of inoculated samples did not differ from the negative control. Conversely, detrimental effects on sperm viability and motility were observed after 24 h of incubation/storage at the highest infective concentrations in both experiments. The deleterious effects observed because of the presence of C. perfringens in semen emphasise the relevance of detecting bacteria in extended doses destined to AI. So, this study suggests that the evaluation of bacterial contamination in semen is a procedure that should be routinely applied while assessing sperm quality in AI centres to avoid the use of doses with low sperm quality and the possible spread of bacterial contaminants.