Effect of Colloid Centrifugation and Cold Storage of Boar Semen at 4 °C on Bacterial Load and Sperm Quality

Background/Objectives: Alternatives to antibiotics in semen extenders used for pig breeding are needed. Cold storage of boar semen is possible in certain extenders; however, bacteria can still survive. Colloid centrifugation can remove bacteria; therefore, a combination of colloid centrifugation and cold storage on the bacterial load and sperm quality of boar semen was investigated. Results: The sperm quality in the original samples were similar in samples with and without antibiotics, respectively. At Day 4, the bacterial count was not different between controls stored at 17 degrees C with antibiotics and SLC cold-stored samples without antibiotics. The proportion of dead sperm increased in controls at 16-18 degrees C (28.12 +/- 21.72% vs. 32.88 +/- 20.94%; p < 0.05), and DNA fragmentation increased from 1.5 +/- 1.02% at Day 0 to 6.1 +/- 3.64% at Day 4 (p < 0.01), whereas it did not deteriorate in the cold-stored samples (Day 4: %DFI 2.00 +/- 1.65% and 1.90 +/- 1.05% for SLC samples with and without antibiotics, respectively). Methods: Aliquots of boar ejaculates were extended in Androstar Premium with and without antibiotics. The samples without antibiotics were processed by Single Layer Centrifugation (SLC) through Porcicoll; sperm pellets were resuspended in AndroStar Premium, with or without antibiotics, cooled slowly, and stored for 4 days at 4 degrees C. Controls (aliquots extended in AndroStar Premium with antibiotics) were stored at 17 degrees C. The bacterial load and sperm quality were assessed in the original samples and after 4 days of storage. Conclusions: Single Layer Centrifugation combined with cold storage is an effective method for reducing the bacterial load in boar semen, with or without antibiotics.