Influence of butylated hydroxytoluene addition to cryodiluents on freezability and DNA integrity of Boer and Zaraibi buck spermatozoa

Abstract

Objective: To evaluate the cryoprotective effect of butylated hydroxytoluene on buck frozen semen. Methods: Semen was collected from Boer (n=6) and Zaraibi (n=6) bucks by electroejaculator for 5 weeks. Semen aliquots were diluted at 38 °C in Tris-buffer with egg yolk 15.0% (vol/vol) (Tris- egg yolk extender) or soya lecithin 2.5% (weight/vol) (Tris-soya lecithin extender) supplemented with butylated hydroxytoluene at 0.0 (as the control), 0.5, 1.0, 2.0 and 4.0 mM. Post-thawing motility (at 400x magnification), plasma (hypo-osmotic swelling test), acrosome (Trypan blue/Giemsa dual staining) membranes, DNA (comet assay), and lipid peroxidation (by malondialdehyde concentration) were assessed. Results: Spermatozoa motility was enhanced by butylated hydroxytoluene in Tris-soya lecithin extender at 0.5 mM in the two breeds, and in Tris-egg yolk extender at 1.0 mM in Boer and at 2.0 mM in Zaraibi bucks for up to 3 h post-thawing. Plasma and acrosome membranes and DNA integrity of the two breeds were maximally high with butylated hydroxytoluene at 1.0-2.0 mM in Tris-egg yolk extender and at 0.5-1.0 mM in Tris-soya lecithin extender. Lipid peroxidation was minimal with butylated hydroxytoluene at 1.0-2.0 mM in Tris-egg yolk and soya lecithin extenders in the two breeds. Butylated hydroxytoluene at 4.0 mM deteriorated spermatozoa motility, and plasma and acrosome membranes. Conclusions: The consequence of butylated hydroxytoluene on buck frozen-thawed spermatozoa varies with the levels of supplementation, buck breed, and phospholipid source in the extender. Semen parameters of Boer buck are better in their response to butylated hydroxytoluene than Zaraibi buck. Butylated hydroxytoluene at 1.0 and 2.0 mM in Tris-egg yolk extender, and at 0.5 mM in Tris-soya lecithin extender represents the best concentrations and profitably improves the semen quality of buck semen.