Efeito de diferentes métodos de congelamento, diluentes e tempos de resfriamento sobre a qualidade do sêmen suíno criopreservado

Ano: 2011 | Volume: 39 | Número: 1

Autores: Ivan Bianchi, Elisângela Mirapalheta Madeira, Augusto Schneider, Viviane Rohrig Rabassa, Érico Kunde Corrêa, Thomaz Lucia Jr., Marcio Nunes Corrêa

Palavras-chave: inseminação artificial, criopreservação, espermatozóides, lipoproteína de baixa densidade, gema de ovo

Resumo Inglês:

Background: Artificial inseminations in swine are conducted with liquid semen cooled at 15 to 18ºC for 1 to 5 d. Frozen semen
in not routinely used due to its poor reproductive performance in comparison with cooled semen. In semen freezing protocols,
egg yolk is added to extenders to protect the sperm membrane against cold shock. The cryoprotectant effect of egg yolk is
attributed to the presence of low density lipoprotein (LDL) in its composition. Thus, replacement of egg yolk by LDL in the
composition of extenders may be feasible to reduce cryoinjuries in sperm cells due to cold shock. During the process of sperm
freezing the cell receive structural and functional injuries that could impair the fertilization process. Two experiments were
conducted to evaluate the effect of freezing method, extenders and duration of the freezing process.
Materials, Methods and Results: In experiment 1 post-thawing motility of the Westendorf (WE) method was higher (P <0.05)
than Paquignon (PA) method at 10 min (46.0±1.7 and 34.3±1.4, respectively) and 30 min (45.5±2.1 and 32.9±1.3, respectively).
Membrane integrity 10 min after thawing was higher (P <0.05) in WE than PA method (45.2±1.3 and 33.7±2.7, respectively).
In experiment 2 motility 10 min after thawing was higher (P <0.05) in BTS extender (43.0±1.7) than in PIGPEL-5 (34.0±1.7)
and PIGPEL5-LDL (33.0±1.7), as well as 30 min after thawing, being 37.0±1.5 for BTS, 32.0±1.5 for PIGPEL-5 and 31.0±1.5
for PIGPEL5+LDL. There was a difference (p <0.05) in pre-freezing motility between Short and Standard methods at 10 min
(39.0±0.7 and 35.0±1.2, respectively) and 30 min (35.0±0.7 and 32.0±0.9, respectively), but no difference (P >0.05) in
membrane integrity after thawing between Short (40.3±2.4) and Standard (38.7±2.8) methods. The analysis was performed
using the software SAS.
Discussion: Sperm motility and membrane integrity were greater for the WE method than for the PA method, which can be due
to the presence of seminal plasma during cooling, since the benefits of the presence of seminal plasma proteins have been
widely reported. In the PA method, the glycerol-based freezing extender was added to semen at 15ºC, remaining in contact with
the semen for 60 min before freezing. On the other hand, in the WE method, the glycerol-based freezing extender was added
to semen only at the temperature of 5ºC. Thus, the reduced sperm motility and membrane integrity observe in the PA method
may have occurred as a function of the prolonged exposure to glycerol. The presence of a non-penetrating cryoprotectant
(either egg yolk or LDL) during cooling at temperatures greater than 15ºC did not benefit sperm motility and membrane
integrity. That may have been due to the low content of both egg yolk and LDL added to the extender (2%) which may not been
enough to ensure cryoprotection. The 120m cooling period up to 15ºC was efficient on stabilizing the sperm cells in the
extenders, protecting then against cold shock, which allowed a substantial reduction in the period necessary to complete the
freezing process. The use of WE method associated BTS extender and Short freezing method was the most efficient protocol
for boar semen cryopreservation.