Vitamina E e qualidade do sêmen bovino fresco e criopreservado

Abstract

The objective was to evaluate the effects of vitamin E on fertility of bulls. In the first study (Addition of vitamin E in the extender of cryopreservation and evaluation of the bovine semen fertility) the objective was to evaluate the addition of vitamin E to the extender cryopreserved bovine semen on the sperm quality, the level of oxidative stress and early development produced embryos "in vitro". We used 38 Nelore bulls with an average age of 36 months and mean body weight of 490 kg. The ejaculate was collected by electroejaculation method. Then the semen was immediately subjected to tests: volume, appearance and color ejaculate, whirling, motility, sperm vigor and sperm concentration for subsequent dilution. Aliquots were collected for assessments: morphology (major defects, minor and total), sperm viability (eosin-nigrosin staining), assessment of oxidative stress (TBARS - thiobarbituric acid reactive species). After the assessment of semen aliquots were diluted into four treatments: control treatment (CT) only lactose - gem (basic extender); Treatment 10 (T10) base extender with the addition of 10 mmol/mL of vitamin E; Treatment 30 (T30) basal extender with added 30 mmol/mL of vitamin E; 50 treatment (T50) using the base extender with the addition of 50 mmol/mL of vitamin E, so that the final concentration was 22.5 million spermatozoa / mL. The semen was cooled to 5 °C for 4 hours and then loaded into 0.5ml straws, frozen in nitrogen vapor for 15 minutes and stored in liquid nitrogen until the analysis. Straws were thawed in a water bath at 36 °C for 30 seconds and analyzed for motility, vigor, sperm viability, assessment of oxidative stress and fertility of the sperm through in vitro embryo production (FIV). The experiment was conducted in experimental completely randomized design and data analyzed using ANOVA and the effect of treatment was compared by the SNK (Student-Newman-Keuls) with a significance level of 10%. The spermatic did not differ between the mean values observed in the treatments (p>10). The control treatment resulted in less loss of quality in straight progressive motility after thawing (13.31 ± 2.34%) compared to other experimental groups T10 (5.36 ± 0.92%), T30 (8.15 ± 1,80%) and T50 (10.10 ± 1.57%). In the evaluation of oxidative stress sperm average values in the treatment T10 (50.91 ± 7.22ng / ml), T30 (65.88 ± 2.58 ng/ml) and T50 (84.22 ± 11.68 ng/ml) were superior to results obtained in the control treatment TC (13.07 ± 1.87 ng/ml) (p 0.0001). In PIV T50 produced higher in vitro embryos (39.85% ± 6.22%) than other treatments, T10 (27.26% ± 6.63), T30 (25.88% ± 5.69), however no significant differences from the control group (27.90% ± 3.89). Concluded that the use of vitamin E in the extender of cryopreservation of bovine semen did not preserve the quality of semen cryopreserved cell, did not reduce oxidative stress or improved in vitro production of embryos. In experiment 2 (Oral supplementation with vitamin E: sperm membrane integrity and semen quality in supplemented bulls to grazing) aimed to evaluate membrane integrity and sperm quality in Brangus bulls supplemented with vitamin E and raised on pasture. Were used 11 Brangus bulls were used with mean age of 120 months and mean weight of 442.2 kg, randomly distributed into two treatments: control group (CG) and vitamin E-supplemented group (GS-400 IU vitamin E / day) added to supplement concentrated. Each group was kept in a separate paddock of Panicum maximum cv. And concentrated Mombaça received daily in the amount of 4.5 kg/animal. Supplementation with vitamin E was performed for 60 days. During experimental period were performed four semen collections: one before the start of supplementation, another one with 30 and 60 days of supplementation, and 15 days after the end of supplementation. Semen was collected by electroejaculation in graduated tube, has measured volume, color and ejaculate appearance. They were then evaluated motility (MOT), vigor (VIG) and turbulence sperm. Tests were conducted to evaluate the sperm morphology (major defects, minor defects and total defects), sperm membrane integrity (hypoosmotic test, HIPO) and acrosomal membrane (fast green rose bengal staining, POPE) and to evaluate sperm viability (eosin nigrosin staining, EOS) and acrosome reaction (Stain Trypan staining). The experiment was conducted in completely randomized design with repeated measures. Data were analyzed by ANOVA and SNK test with a significance level of 10%. Found a significant interaction between treatment x collection in assessing the acrosome reaction (trypan) (P <0.10). Were found to effect the collection (Consistency) (p 0.0001), volume (VOLUME) (p = 0.0442); force (FORCE) (p = 0.0263), larger defects (p = 0.0515) ; total defects (p = 0.0703), hypoosmotic test (HIPO) (p = 0.0131) and acrosomal integrity (POPE) (p = 0.0006). There were no significant differences (p> 0.10) for the other variables: motility, concentration, turbulence, minor defects and scrotal circumference. With the results obtained in the experimental conditions of this study, we conclude that oral supplementation with vitamin E, 400UI/dia vitamin E did not alter the quality of semen or sperm membrane integrity of sperm cells.