Estudo da viabilidade do extrato da castanha-do-brasil (Bertholletía excelsa) na criopreservação de sêmen bovino

Abstract

Semen cryopreservation is widely used to increase the reproductive potential of animais of high genetic and zootechnical value; however, the protocols used result in a considerable number of spermatozoa that suffer some kind of lesion due to the formation of ice crystals, oxidative injuries, alterations On the sperm membrane and cryoprotective toxicity. The objective of this study was to evaluate the feasibility of the use of Brazil nut extract (Bertholletia excelsa) in the elaboration of the cryoprotective médium in substitution of egg yolk for cryopreservation of bovine semen. Experimental treatments consisted of 0, 25, 50, 75 and 100% replacement of the egg yolk by Brazil nut extract in cryoprotectant médium, with the same concentration of distilled water and Tryladil being established at ali dilutions. Eive bulls of the Nelore breed were used between 24 and 36 months, being the method to obtain the material the electroejaculation. The experimental design was a randomized complete block design, with five blocks, five treatments and five replications. The spermatozoa were counted in the Neubauer chamber to continuously carry out the dilutions in the experimental and packaging treatments. The blades were then sealed, cooled, frozen and stored at -196 0 C. After thawing, the samples were evaluated for morphology, kinetics, membrane integrity (HOST and epifluorescence), and then IVF. The regression test was used for the parametric data and for the non-parametric Kruskal Wallis, both at 5% significance. We used the simple Pearson correlation test between intact or damaged cells with mitochondrial membrane potential. In the morphological analysis, the minor and total defects had an increasing linear effect as a function of the substitution, showing that as the concentration of the extract was increased, the number of defects was higher; In the HOST test, a linear decreasing effect was observed, resulting in a larger number of cells with damaged membranes as it replaced the yolk with the chestnut extract. Similar behavior was observed in the membrane integrity analysis through epifluorescence, with a higher number of cells without mitochondrial membrane potential and lesions when 100% egg yolk was replaced by the extract. TTR showed quadratic effect for motility at zero hours and one and linear effect at the second hour of the test; However, the vigor presented difference only in the second hour, due to the replacement of the egg yolk with the Brazilian nut extract. It was also observed a quadratic effect for the total and progressive motilities evaluated by the CASA and cleavage rate in the IVF, ali of which were negatively influenced by the substitution of the egg yolk for the Brazil nut extract. Thus, the substitution of the egg yolk for Brazil nut extract was not efficient in semen cryopreservation, indicating that the LDL fraction of the yolk is essential. In addition, the selenium content found in the extract was considered high and toxic to spermatozoa.