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 曟 in Tris-buffer with egg yolk 15.0% (vol/vol) (Trisegg
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 400伊 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.