Qualidade do sêmen fresco e criopreservado de touros pantaneiros : efeito da época do ano e antioxidantes

• Autor(a) principal: Silva, Luis Eduardo Senra e
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFMT
• Texto Completo: http://ri.ufmt.br/handle/1/452
• topic: Antioxidantes; Estresse oxidativo; Sazonalidade; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA; Antioxidant; Oxidative stress; Seasonality

Heat stress usually leads to testicular degeneration in cattle breeding and Bos taurus are less resistant to alterations. Although the Pantaneiro breed is European origin the animals are adapted to Pantanal region, and thus it is unclear what their susceptibility to high temperatures and influence in relation to semen quality. Regarding the cryopreservation of semen , it is known that a major cause of the reduction in quality is oxidative stress, although many investigations have been made to provide antioxidants agents to animals and decrease the lipid peroxidation caused by radical free, contradictory results have been found and many researchers have taken into account the physiological status of the animals. In this context, our objective was to evaluate the seasonality on sperm quality Pantaneiro bulls, as well as identify the effect of adding antioxidants to semen extender in times of different climatic conditions. In experiment 1, 7 Pantaneiro breeding and 3 Nellore were used, semen collection was taken in January and July 2013 were evaluated, circumference and testicular consistency, motility, vigor, viability, concentration, acrosomal membrane integrity, sperm morphology, activity mitochondrial cytochemistry and the amount of thiobarbituric acid reactive substances. The experiment was conducted in a completely randomized design and a 2x2 factorial arrangement (2 breeds and 2 seasons). The membrane integrity was lower in the winter season (95.76% ± 1.77 vs. 87.07% ± 4.78, P = 0.03 ), the Nelore breed had higher amount of minor defect in summer (2.16% ± 1.09 vs. 0.57% ± 0.31; P= 0.02 ), higher percentage of larger defect (61.91% ± 5.92 vs. 26% ± 3.83 P= 0.01) and total defects (62.58% ± 5.63 vs. 27.33% ± 3.91 P= 0.03) in winter. The frozen semen was not affected by breed, season or interaction between them. These results can be explained by the adaptation of animals Pantaneiro to the Pantanal region, breeding Pantaneiro are more suitable, since his seminal quality is not adversely affected by the season. In experiment 2, the same animals were used, but at the time of dilution of semen was added 10 mM Trolox/20x106 sperm, or 2.25 mg of ascorbic acid/20x106 sperm, or even a combination of them. After thawing the analysis of motility, viability, sperm viability, acrosomal membrane integrity, mitochondrial activity cytochemical and spontaneous lipid peroxidation was performed. The experiment was conducted in a completely randomized design, and 2x2x4 factorial arrangement (2 breeds and 2 seasons and 4 antioxidants treatments). The motility, viability, acrosome integrity and mitochondrial activity were reduced with the addition of antioxidants (P<0,05) in particular the interaction between vitamin C and Trolox. Although the addition of antioxidants did not change the level of lipoperoxidation. The results can be explained by decreased levels of reactive oxygen species caused by antioxidants and a possible inhibition of signaling events such as sperm movement and activity of mitochondria, thus we can infer that the animals had not used vitamin deficiency and their demand, especially vitamin E, was met by supply.