The effect of butylated hydroxytoluene (BHT) on bull spermatozoa frozen in two different extenders

This study evaluated the protective effect of butylated hydroxytoluene (BHT), a lipid-soluble antioxidant against cryopreservation damage on bull spermatozoa. Four BHT concentrations (0.5, 1, 2 and 4 mM) were evaluated. Sperm characteristics were evaluated when BHT was added to a post-thaw–freezing extender by measuring the degree of sperm lipid peroxidation (using malondialdehyde, MDA) and by measuring parameters such as motility and viability of spermatozoa. Production of MDA as an indicator of lipid peroxidation was obtained when BHT ranged from 0.5 to 1 mM in both extenders (P < 0.0001). Sperm motility and viability evaluated immediately after thawing was higher in BHT-treated spermatozoa, this was significant (P < 0.001) when the freezing egg yolk–citrate extender was supplemented with 0.5 and 1 mM BHT and when egg yolk–Tris extender was supplemented with 0.5 mM BHT. The addition of 0.5 and 1 mM BHT to semen egg yolk–citrate extender increased the viability of frozen semen after thawing (P < 0.007). The addition of 0.5 and 1 mM BHT to both extenders resulted in a significant (P < 0.0001) decrease in MDA production. In conclusion, the addition of BHT to freezing egg yolk–citrate extender improved the overall efficiency of thawed bull spermatozoa, but the addition of BHT to the freezing egg yolk–Tris extender did not.