Semina: Ciências Agrárias (Jun 2015)
Effect of oleic-linoleic acid and ?-sitosterol to freezing extender of bulls and stallions semen
Abstract
Addition of polyunsaturated fatty acids and/or cholesterol to a freezing diluent can modify the sperm plasma membrane composition, influencing its behavior during cryopreservation, thus, favoring seminal cryoresistance. The present study aimed to evaluate the effects of the addition of oleic-linoleic acid, (OLA); ?-sitosterol (?-sit), a plant analog of cholesterol; and OLA + ?-sit in combination to a freezing diluent, on the cryopreservation bull and stallion semen. The following variables were analyzed: motility/vigor, plasma and acrosomal membrane integrity (by Trypan Blue/Giemsa staining), mitochondrial activity (by DAB staining), and lipid peroxidation (by a TBARS assays). The lipids were added according to experimental treatments: C – control group, A1 and A2 – OLA at concentrations of 37 ?M and 74 ?M, B1 and B2 – ?-sit at concentrations of 1 ?g mL-1 and 2 ?g mL-1; AB1 and AB2 – OLA 37 ?M + ?-sit 1 ?g mL-1 and OLA 74 ?M + ?-sit 2 ?g mL-1, respectively. The study was divided into three experiments; in Experiment 1, the concentrations of the groups A1, B1, and AB1 were evaluated, whereas in Experiment 2 the concentrations of the groups A2, B2, and AB2 were analyzed, both experiments were performed with bull semen. We conducted Experiment 3 using equine semen with the addition of lipids at all of the concentrations described. Data were subjected to analysis of variance, using the GLM procedure of SAS, with treatment means compared by Duncan test considering 5% significance. These variables differed significantly after thawing the semen post-collection. However, there was no significant difference between treatments when variables were compared within the same time point, except for Experiment 2, where there was a decrease in motility and vigor decrease post-thaw in the groups following ?-sit addition (C – 51.0 ± 13.7%/2.9 ± 0.4; B2 – 35.8 ± 15.8%/2.3 ± 0.6; AB2 – 38.5 ± 16.6%/2.5 ± 0.5, respectively; p < 0.05). In conclusion, the tested concentrations of these lipids did not confer greater cryoresistance to the spermatozoa, and were not effective in preserving the structural integrity of plasma and acrosomal membranes after thawing. Furthermore, there was no change in the mitochondrial activity and lipid peroxidation due to lipids addition.
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