Antibacterial defense and sperm quality in boar ejaculates.

The aim of the present study was to characterize the lysozyme concentration and the bacterial killing activity (BKA) of boar seminal plasma against E. coli and S. aureus in 119 fertile Pietrain boars (aged: 18.1 ± 10.5 months). Lysozyme concentration was 2.4 ± 1.2 μg/ml in seminal plasma. More than 80% of the samples (97 of 119) showed BKA against E. coli or S. aureus or both bacterial strains: Group 1 (BKA against E. coli and S. aureus, n = 38), Group 2 (BKA against E. coli, n = 13), Group 3 (BKA against S. aureus, n = 46), and Group 4 (no BKA, n = 22). Boars with BKA against E. coli (Group 1 plus 2) were older (P <  0.001) than boars with BKA against S. aureus only or without BKA. Thermo-resistance of spermatozoa was lowest in boars without BKA (P =  0.002). Lysozyme concentration was higher in boars with BKA against S. aureus only compared to boars with BKA against both bacterial species (P =  0.005) and boars with BKA against E. coli only (P =  0.047). In Group 2, the ratio of morphologically normal spermatozoa was lower than in all other groups (P <  0.001) and mitochondrial activity of spermatozoa was lower compared to Group 3 (P =  0.023). The results suggest an age related variance of BKA against E. coli in boar semen. BKA is related to different sperm quality characteristics. Further research is necessary to discover the molecular components, which are responsible for BKA of boar seminal plasma.