The impact of bacterial contamination of the ejaculate and extender on the quality of swine semen doses

Abstract

The aim of this study was to verify the influence of the degree of bacterial contamination of boar ejaculate and semen extender on the quality of semen doses. The experiment was conducted in four boar studs, from which raw semen and two semen doses from each ejaculate were collected to evaluate the number of colony-forming units (CFU), pH, sperm morphology and motility. Extender samples were also evaluated for CFU. Ejaculates that had higher levels of contamination (> 220 CFU mL-1) resulted in semen doses with a greater degree of bacterial contamination but with no reduction in motility or alteration in pH. When the semen doses were classified according to the degree of contamination of the extender, a decrease in motility was observed after 108 and 168 h of storage (P < 0.05) in the group whose extender had ≥14,000 CFU mL-1 versus the group whose extender had ≤ 330 CFU mL-1. The pH remained stable during 168 h of storage in semen doses with extender that had lower contamination levels, but decreased from 7.2 to 6.0 between 24 and 168 h of storage (P < 0.05) in the group with extender that had higher levels of contamination. A higher number of abnormal acrosomes (P < 0.05) was observed after 168 h of storage in the semen doses whose extender was highly contaminated. The production of semen doses with low bacterial contamination and high sperm cell viability will only be possible with a strict hygienic control in semen processing, primarily with respect to the extender, combined with minimal contamination during collection.