Efeito da adição de diferentes crioprotetores e antioxidantes na criopreservação do sêmen de ovinos da raça Santa Inês

Abstract

Aiming to evaluate the effect of adding different cryoprotectants (glycerol, ethylene glycol or acetamide) and antioxidants (resveratrol and quercetin) on in vitro viability of ram thawed semen samples, four adult males, Santa Ines crossbred, were used. After collect semen using an artificial vagina, aliquots of semen were evaluated macroscopic and microscopically and the pool of semen was divided and diluted in Tris-yolk medium, according to experiments and experimental groups. For the Experiment I, which evaluated the cryoprotectants addition, the experimental groups were classified as: G1 = Tris-yolk egg + 5% glycerol, G2 = Tris-yolk egg + 3% ethylene glycol, G3 = Tris-yolk egg + 5% ethylene glycol; G4 = Tris-yolk egg + 2% acetamide, G5 = Tris-yolk egg + 7% acetamide. However, the Experiment II, which were used the antioxidant treatments, was divided in three sub experiments: Exp 1 [resveratrol (0, 5, 10, 15 and 20 μg/mL, respectively, R0, R5, R10, R15 and R20)]; Exp 2 [quercetin (0, 5, 10, 15 and 20 μg/mL, respectively, Q0, Q5, Q10, Q15 and Q20)], and Exp 3 [without antioxidant (RQ0), 10 μg/mL of resveratrol (R10), 5 μg/mL of quercetin (Q5), and 10 μg/mL of resveratrol + 5 μg/mL of quercetin (R10Q5)]. After dilution, aliquots of semen were packed in straws (0.25 mL), frozen (-196 °C) and evaluated after thawing (37 oC/30 seconds) for progressive motility (PM), vigor, plasma membrane integrity (PMi), mitochondrial membrane potential (MMP) and acrosome integrity (ACi). It was found that in Experiment I, G1 showed higher PM (P<0.05) than G3, G4 and G5; vigor was higher (P<0.05) than G4 and G5; and PMi higher (P<0.05) than G2, G3, G4 and G5. However, there was no significant difference (P>0.05) among groups on the MMP and ACi parameters. In Experiment II, there was no difference among groups on the PM, vigor, PMi and ACi. MMP had significant difference (P<0.05) among experimental groups of their three sub experiments. So, in Exp 1, R0 group (36.67±8.01%) was higher than R20 (22.33±6.16%); in Exp 2, Q0 group (36.25±8.12%) was higher (P<0.05) than Q10 (9.33±6.54%), Q15 (6.25±5.98%) and Q20 (5.17±5.08%), and the Q5 (20.58±12.05%) was higher (P<0.05) than Q15 (6.25±5.98%) and Q20(5.17±5.08%) groups; and in Exp 3, RQ0 group (39.00±16.79%) was higher (P<0.05) than Q5 (18.00±13.76%) and R10Q5 (14.42±7.47%) groups. It can be concluded that glycerol (5%) is more effective in protecting ram spermatozoa submitted to deleterious effects of freezing than ethylene glycol (3 and 5%) and acetamide (2 and 7%); the addition of resveratrol and quercetin phenolic antioxidants, alone or in combination, reduces mitochondrial membrane potential of sperm frozen ram; and other studies should be performed to evaluate different concentrations and the effect of the addition on the fertility rate of ewes inseminated artificially.