Preservability of bull spermatozoa in Tris-egg yolk extender enriched with different concentrations of butylated hydroxytoluene

Objective:To explore the effect of BHT on cattle spermatozoa during cooling and cryopreservation.Methods: Pooled bull semen were diluted by Tris-Citrate-Fructose egg yolk (TCFY) diluent considered as control (0 BHT) and different concentrations of BHT (1.0, 2.0, 3.0, 4.0, 5.0 and 6.0 mM were prepared in ethanol in prewarmed (37℃) test tubes. The ethanol was allowed to evaporate so that, a thin crystallized layer of BHT was deposited on the inner surface of the tubes. Then extended semen was added into the tubes and incubated at 37℃ for 5 min to allow uptake of BHT by spermatozoa. The tubes were cooled slowly (approximately for 2 h) up to 5℃ and equilibrated for 4 h. After equilibration, semen freezing process was carried out. Extended semen was subjected to evaluation (motility, alive sperm, intact sperm membrane (HOST) % and acrosome integrity) in both cooled and cryopreserved semen. Results:The result revealed that sperm motility of post-cooled spermatozoa improved (P