Congelamento de sêmen suíno: estudo de crioprotetores intra e extracelulares, metodologias de congelamento e marcador molecular de congelabilidade

Abstract

Although boar semen is available in the frozen format since 1975, its use has been restricted to very specific situations for many reasons: it requires spermatozoa concentration per dose twice to three times higher than that for cooled semen; semen processing is labor intensive; and farrowing rate and litter size are reduced. Thus, most of the artificial inseminations in swine are performed at the day of semen collection or at most at the following day, using liquid semen conditioned between 15 and 18 ºC. The aims of this thesis were: to evaluate distinct extenders for cooling semen, methods for freezing, centrifugation temperatures, the use of amides as penetrating cryoprotectants and of low density lipoprotein as nonpenetrating cryoprotectants, and the presence of specific protein factors in seminal plasma in the results that could be associated with boar semen freezability. Five experiments have been executed: four with evaluations in vitro (motility and cell membrane integrity); and one with fertilization in vivo. The control treatment was the freezing with glycerol at 3% concentration. The semen processing method that provide more efficient results consisted of semen cooling during 120 min up to a centrifugation temperature of 15 °C. We also identified a 26 kDa factor in the seminal plasma that is associated with maintenance of the integrity of the sperm cell membrane post-thawing. Additionally, parameters of semen quality in vitro with the use of dimetilacetamide at 5% were better than those observed with the most used penetrating cryoprotectant (glycerol 3%) as control, although no difference between those cryoprotectants was observed in vivo. This study demonstrated the association of components in the seminal plasma with the sperm quality, and presenting an alternative protocol of semen freezing-thawed boar semen based in the use of dimetilacetamide at 5%.