Effect of oleic-linoleic acid and β-sitosterol to freezing extender of bulls and stallions semen Efeito da adição de ácido oleico-linoleico e β-sitosterol ao diluente de congelação do sêmen de touros e garanhões 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); β-sitosterol (β-sit), a plant analog of cholesterol; and OLA + β-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 μM and 74 μM, B1 and B2 – β-sit at concentrations of 1 µg mL-1