Spermatozoa cooled to 5C one day after collection from porcine commercial semen doses retain sperm functionality with reduced bacterial load

BackgroundCommercial porcine semen is stored at 17 degrees C, leading to a reduction of sperm quality and increase of bacterial growth. ObjectivesTo evaluate the effect of 5 degrees C storage on porcine sperm functionality cooled one day after collection. Materials and methodsSemen doses (n = 40) were transported at 17 degrees C and cooled at 5 degrees C one day after collection. Spermatozoa were evaluated at Days 1, 4, and 7 for motility, viability, acrosome integrity, membrane stability, intracellular zinc, oxidative stress, and bacterial growth. ResultsContaminated semen doses predominantly exhibited Serratia marcescens, with increasing bacterial load during 17 degrees C storage. Under hypothermal storage, negative doses for bacteria growth at Day 1 remained negative, and bacterial load did not increase in bacterial contaminated samples. Motility was significantly reduced through 17 degrees C storage, but at 5 degrees C, motility was only reduced at Day 4. Samples with bacterial growth (35.0%, 14/40) had significantly reduced motility at 17 degrees C, but motility was unaltered at 5 degrees C. Plasma membrane and acrosome integrity without bacterial contamination were unaffected at 17 degrees C, but were significantly reduced at 5 degrees C on Day 7. Plasma membrane and acrosome integrity significantly decreased with bacterial contamination regardless of temperature. High mitochondrial activity in viable spermatozoa without bacteria was not altered by temperature, but was significantly reduced by bacterial contamination at 17 degrees C. Membrane stability was significantly reduced at Day 4, but tended (p = 0.07) to be higher in samples without bacterial growth. Viable spermatozoa exhibiting high zinc were significantly reduced throughout storage regardless of temperature. Oxidative stress levels were not altered, but significantly increased with bacterial contamination at 17 degrees C. Discussion and conclusionPorcine spermatozoa cooled to 5 degrees C one day after collection retain functional attributes similar to spermatozoa stored at 17 degrees C, but have a reduced bacterial load. Cooling extended boar semen to 5 degrees C is feasible after transport to avoid modifying semen production.