Inter- and intraindividual variability of bacterial content in boar semen

The aim of this study was to evaluate inter- and intraindividual variability in total bacterial count (TBC) in raw and extended boar semen and to identify management- and animal-related factors associated with this variability. Semen samples from 92 clinically healthy boars of different breeds and ages, housed in barns with varying bedding, ventilation and cooling systems, were examined monthly over a 13-month period. Progressive motility of diluted sperm (PMSd) was assessed by computer-assisted semen analysis (CASA) on the day of collection (D0) and after 7 days of storage at 16°C (D7). Total bacterial count in raw semen (TBCr) and diluted semen (TBCd) was quantified by flow cytometry. Bacterial counts varied markedly between and within boars. Breed, age and season had no effect on TBCr (P > 0.05). Samples collected by hand tended to have higher TBCr on D0 than those collected using the semi-automatic system (b = 3.84, P = 0.096). Semen from two of 3 b had higher TBCr than the other (b = 5.53, P = 0.004 and b = 6.42, P = 0.032). A clear reason for this has not been found. TBCd was negatively associated with PMSd on D0 (b = -0.67, P = 0.002). These results demonstrate substantial variability in bacterial counts in boar semen and indicate that specific housing conditions and bacterial load in diluted semen may be associated with sperm quality.