225 OXIDATIVE STRESS AND MEMBRANE INTEGRITY OF CRYOPRESERVED SPERMATOZOA WITH VITAMIN C

Abstract

Disturbances in oxidant/production in favour of oxidizing cause oxidative stress during the cryopreservation process. Vitamin C is an antioxidant non-enzymatic present in seminal plasma that protects sperm from oxidative stress. The aim of this study was to evaluate supplementation with ascorbate in a cryopreservation medium on oxidative stress and quality of cryopreserved sperm membranes. It was used in 24 bulls averaging 31 months and 732 kg, kept on pasture for this experiment. One ejaculate was collected from each breeder by electrostimulation. The treatments were CO-Control (no additives) and AS-ascorbate (0.45 mg mL^–1). Ascorbate was added to diluted semen at the time of filling in 0.5-mL straws before the cryopreservation process. Thawing was performed in a water bath at 37°C for 30 s. After thawing the samples, aliquots for assessment of plasma and acrosome membrane integrity and evaluation of oxidative stress [TBARS concentration spontaneous (TE) and induced (TI)] were taken. The experiment was conducted in a completely randomised design. Data were analysed by ANOVA and compared by the Tukey average test with a significance level of 5%. No differences were observed (CO- 31.67 ± 2.81 v. AS- 31.08 ± 2.42, P > 0.05); the quality of the sperm membrane and oxidative stress (TECO: 5.98 ± 2.13 v. TEAS: 6.62 ± 2.33, P > 0.05 and TICO: 62.34 ± 8.22 v. TIAS: 58.52 ± 8.27, P > 0.05) in sperm cryopreserved with ascorbate were similar to the control group. Typically, animals under adequate nutritional conditions produce adequate amounts of ascorbate; perhaps because of that the treatment using exogenous ascorbate did not present a significant result. The supplementation of extender with ascorbate did not affect oxidative stress and the quality of the plasma membrane and acrosome sperm cryopreserved. Preliminary studies had shown that the addition of higher concentration (4,5 mg mL^–1) of ascorbate has a beneficial effect on oxidative stress and membrane integrity (P < 0.05). Thus, further research should be done to better understand the effects of ascorbate in bovine semen.