Criopreservação de sêmen bovino com antioxidantes: avaliações funcionais e fecundação in vitro

Abstract

The aim of this study was to evaluate the addition of antioxidants in cryopreservation process of bovine semen, from complementary tests (stamina and sperm motility post thawing, quick thermos-resistance test, acrosomal and plasma membranes integrity, oxidative stress and sperm morphology) and in in vitro fertilization (IVF). Therefore, the ejaculate from nine animals was divided in four fractions, corresponding to one treatment each, these being: control group – semen diluted in Tris – yolk; vitamin group – semen diluted in Tris – yolk plus 2.5 mM/mL of vitamin C; glutathione group – semen diluted in Tris – yolk plus 2.5 mM/mL of reduced glutathione and associated group – semen diluted in Tris – yolk plus half of the concentration (1.25 mM/mL), later the semen was packed into french straws and submitted to cryopreservation through an automatized equipment, TK 3000®. For IVF, ovaries from slaughterhouses were aspirated to obtain oocytes grades I and II. These were submitted to in vitro maturation (IVM) followed by IVF; where each drop containing the matured oocytes, was combined with the capacitated semen, corresponding to each treatment. Fertilization rate was assigned to embryos divided into two or more blastomeres. There was statistical difference (P< 0.05) for sperm motility for the associated group, however the groups didn’t differ for sperm stamina, the same occurred to acrosomal and plasma membranes integrity. The associated group showed higher percentage of cells with oxidative stress (P< 0.05) and smaller percentage for major sperm defects. Glutathione group showed higher fertilization rate (P< 0.05). Therefore, we can conclude that the association of vitamin C and reduced glutathione favored sperm motility post thawing, however, the antioxidants didn’t show a preventive effect about the structural damage suffered by plasma membranes. And that the association of the antioxidants provides higher oxidative stress and the use of reduced glutathione guarantees increased fertilizing capacity.