Tocopherol in bovine semen cryopreservation extender: fertility and oxidative stress

Abstract Text: The study was conducted to evaluate effects of supplementation with tocoferol (α-tocopherol acetate) in bovine semen extender for cryopreservation on sperm quality and oxidative stress. Thirty eight Nelore bulls with average age of 36 months and average body weight of 490 kg were used. Ejaculate was obtained by electroejaculation and semen was diluted in lactose -egg yolk extender with 4% of glycerol. After semen+extender were divided in four fractions and subjected to four concentrations of vitamin E: TC- Control treatment, without supplementation medium; T10: 10 mmol mL of tocopherol supplementation/mL; T30: 30 mmol of tocopherol supplementation/ mL; T50: 50 mmol of tocopherol/ ml. Semen were frozen with a concentration of 45 million sperm per straw. Straws were thawed at 36 ° C for 30 seconds, and evaluated for sperm motility, sperm viability, and oxidative stress. The experiment was a completely randomized design and data were analyzed using ANOVA and SNK test (Student- Newman - Keuls) with a significance level of 5 %. Treatment control afforded less decrease in progressive motility rectilinear ( p = 0.0135 ) after thawing (13.31 ± 2.34 %) compared to the other experimental groups (T10: 5.36 ± 0.92 % ; T30: 8.15 ± 1.80 %; and T50: 27.90 ± 3.89 %). Oxidative stress on sperm in T10 , T30 and T50 treatments (50.91 ± 7.22 , 65.88 ± 2.58, 84.22 ± 11.68 ng / mL respectively) were higher (p = 0.0001) shown in the TC control treatment (13.07 ± 1.87 ng / ml). However, the treatment T10 provided a higher sperm viability (p = 0.0001, 73.91% ± 3.72) compared to supplementation levels (54.29% ± 4.20 T30, T50 46.41% ± 5.49), but was not superior to CT (68.95% ± 3.88). It can be concluded that use of antioxidants in bovine semen extender for cryopreservation did not protect sperm plasma membrane of lipid peroxidation, or against damage caused by cryopreservation, and the levels used in this work were detrimental to sperm fertility

Keywords: TBARS, fertility, antioxidant