Field fertility of frozen boar semen: a retrospective report comprising over 2600 AI services spanning a four year period.

Worldwide, greater than 90% of sows are inseminated with fresh semen. Less than 1% is inseminated using frozen semen. Albeit, frozen semen is an effective technology for the transfer of genes between breeding pyramids and also to reliably provide semen for planned matings. Little information exists on the long term use of frozen boar semen in commercial pork production operations. The objective in the present study was to assess application of frozen semen throughout a 4 year period comprising more than 2600 AI services. The frozen semen sourced from a boar stud in Manitoba, Canada. All artificial insemination (AI) occurred on a single 1800 sow farm in Indiana, USA. The sperm-rich fraction was collected and only those collections having ≥80% motility and ≤15% abnormalities were further processed. Semen was prepared for cryopreservation using Androhep(®) CryoGuard™, packaged in 0.5mL French straws (average 500 million total sperm per straw) and frozen using a programmable freezer (IceCube™). For each frozen ejaculate, a post-thaw quality check was performed. Ninety eight percent of the ejaculates that were frozen showed at least a 50% post-thaw motility and were approved for shipment. For AI, eight straws were thawed (to achieve at least 2.0×10(9)motile sperm) and diluted with 60mL of extender pre-warmed to 26°C. Within 2-5min of thawing, the sows or gilts were inseminated via intra-cervical deposition using a standard AI pipette. Sows and gilts were inseminated three times PM/AM/PM and AM/PM/AM, respectively. Of 2696 recorded services, 2122 (78.7%) of the females farrowed. The mean (±SD) total number piglets born were 12.5 (±3.9). A progressive improvement of fertility over time was observed mainly due to adaptive procedures associated with an introduced technology. In summary, acceptable fertility is possible with frozen semen and has merit for application as a reproductive management tool.