Effect of different concentrations of Trolox in association with docosahexaenoic acid on equine semen freezing.

The aim of this study was to evaluate the association of different concentrations of Trolox and the addition of a fixed concentration of DHA in the freezing of semen of Mangalarga Marchador stallions. To that end, 16 ejaculates were frozen in the following extenders: E1) BotuCrio (BC; Control); E2) BC + 50 ngml DHA + 30 µM Trolox (BCDHA30T); E3) BC + 50 ngml DHA + 40 µM Trolox (BCDHA40T); E4) BC + 50 ngml DHA + 50 µM Trolox (BCDHA50T). All the tested extenders were similar in preserving different kinematic parameters, cell functional integrity, compacted DNA, and high and intermediate mitochondrial activity (P>0.05). However, sperm cryopreserved in BCDHA40T showed higher velocities than sperm frozen in the control extender (P<0.05). The 30 µM concentration of Trolox was worse for sperm motility and the 50 µM concentration of Trolox did not adequately preserve the structural integrity of the membranes in an extender containing DHA when compared to the BotuCrio (P<0.05) extender. The use of Trolox in freezing extenders containing DHA did not maximize the effect of BotuCrio, except for in the case of sperm velocity parameters when at a concentration of 40 µM.