Field fertility with exported boar semen frozen in the new flatpack container

The present study tested the field fertility of frozen-thawed (FT) Swedish boar semen packaged in flat plastic containers (FlatPacks) and exported for artificial insemination (AI) to overseas nucleus herds. Semen from 47 Swedish boars of Landrace (L), Yorkshire (Y), and Hampshire (H) breeds was frozen using a lactose-egg yolk-based extender with 3% glycerol and 10(9) spermatozoa/ml in 5 ml FlatPacks. For all breeds, FT sperm membrane intactness averaged 60%, while mean FT sperm motility ranged from 49 to 53%. A total of 308 litters resulted from 421 overseas inseminations with FT semen, with a mean farrowing rate (FR) of 73% and 10.7 mean number total piglets born. In a within-sow analysis for the purebred L and Y breedings, the FR and litter size of FT semen were compared with natural matings (NM) and on-farm AI with liquid semen (NW/AI breedings) at the same farms. Farrowing rate was 72.3 and 78.8% (P = 0.23), total piglets 11.3 and 11.6 (P = 0.44), and live piglets 10.1 and 10.2 (P = 0.77), for the FT semen and NM/AI breedings, respectively. The present results suggest that this freezing protocol and FlatPack container maintains high sperm viability post-thaw. Further the fertility levels when inseminated at overseas nucleus herds seem to be similar to those achieved with (NM/AI breedings) at the same farms. This freezing method may be a reliable alternative for the freezing/thawing of boar semen under commercial AI conditions.