Increasing storage time of extended boar semen reduces sperm DNA integrity

There is an extensive use of artificial insemination (AI) in the pig industry. Extended liquid boar semen may be used for insemination for up to 5 days after collection. The objective of this study was to determine the changes in sperm quality, when boar semen was extended and stored at 18 °C for up to 72 h post-collection. The study included three ejaculates from five boars, for each of the four breeds: Duroc, Hampshire, Landrace and Danish Large White (n = 60 ejaculates). The sperm chromatin structure assay (SCSA) showed an increase in DNA fragmentation index (DFI) after 72 h of incubation (P < 0.001), with no differences between breeds (P = 0.07). For two Hampshire boars, all ejaculates had a large increase in DFI after 24 h of incubation. The standard deviation of DFI (SD-DFI) differed between breeds, with the SD-DFI for Hampshire being significantly greater than for the other breeds. The SD-DFI did not change during the 72 h of storage. Sperm viability was determined using SYBR-14 and propidium iodide in combination with flow cytometry. The sperm viability did not differ between breeds (P = 0.21), but a difference in viability during storage (P < 0.001) was detected. In conclusion, the SCSA cytogram patterns were consistent for different ejaculates within boars and storage of extended boar semen at 18 °C for 72 h significantly decreased the integrity of sperm DNA.