Contribution of boars to reproductive performance and paternity after homospermic and heterospermic artificial insemination.

Heterospermic AI is commonly used in swine despite preventing precise evaluation of individual boar fertility. The present study compared the contribution of four boars (A, B, C and D) for reproductive performance and for paternity using homospermic and heterospermic (AB, AC, AD, BC, BD and CD) AI (n=204 for homospermic AI; n=307 for heterospermic AI). Blood samples from the four boars, from all sows inseminated with heterospermic doses and from the umbilical cords of their piglets, as well as tissue smears from mummified fetuses, were genotyped using single nucleotide polymorphisms (SNPs). Differences among boars were detected for the in vitro oocyte penetration rate and for the number of spermatozoa per oocyte (P<0.05), but not for sperm motility, mitochondrial functionality and integrity of the membrane, acrosome and DNA (P>0.05). Homospermic and heterospermic AI resulted in similar (P>0.05) farrowing rates (90.5% and 89.9%, respectively) and total litter size (12.4±0.4 and 12.7±0.7, respectively). Farrowing rate was lower for Boar B than for Boar C (P<0.05), but no other differences in reproductive performance among boars were observed with homospermic AI. The SNPs determined the paternity of 94.2% of the piglets sired by heterospermic AI. In the AC pool, paternity contribution per boar was similar (P>0.05), but differences between boars occurred in all other pools (P<0.05). Boar D achieved the greatest paternity contribution in all pools and parity categories (nearly 60%), whereas Boar B sired the fewest piglets (at most 40%). Reproductive performance was similar with homospermic and heterospermic AI, but differences in performance among boars undetected with homospermic AI were only evident after genotyping the piglets sired through heterospermic AI.