Effects of platelet-activating factor and platelet-activating factor: acetylhydrolase on in vitro post-thaw boar sperm parameters

Cryopreservation of boar sperm compromises fertility after thawing by reducing sperm longevity and inducing acrosome reaction-like changes. In an attempt to improve the post-thaw motility and acrosome integrity of boar sperm, semen was frozen using a modified Westendorf method in which the medium was supplemented with either platelet-activating factor (PAF) or a recombinant platelet-activating factor:acetylhydrolase (PAF:AH; Pafase) before or after freezing. Platelet-activating factor is a phospholipid that is present in boar semen and PAF:AH is the naturally occurring enzyme that converts PAF to biologically inactive Lyso-PAF. Addition of PAF to the cryopreservation medium improved post-thaw motility immediately after thawing and after 3 h incubation at 37 °C (60.0 ± 0.0% and 25.0 ± 2.9%; mean ± S.E.M.) compared to the control sperm (41.7 ± 1.7% and 10.0 ± 2.9%; P < 0.05). Acrosome integrity was higher immediately after thawing and after 3 and 6 h incubation at 37 °C when sperm were frozen in the presence of Pafase (55.7 ± 3.2%, 45.7 ± 3.7% and 23.0 ± 3.1%), compared to the control sperm (42.7 ± 1.5%, 25.7 ± 5.7% and 12.3 ± 2.7%) and sperm frozen in the presence of PAF (33.0 ± 3.7%, 26.3 ± 2.2% and 11.7 ± 0.3%; P < 0.05). Addition of PAF to sperm after thawing improved motility immediately post-thaw (41.6 ± 2.6%), compared with addition of Pafase (23.3 ± 2.2%) or the control sperm with no supplementation of the medium (26.7 ± 2.2%; P < 0.05). However, this beneficial effect was lost by 3 h post-thaw. Supplementation of boar semen cryopreservation medium with PAF and Pafase appeared to have beneficial effects on the in vitro quality of the sperm post-thaw.