The aim of this study was to determine the effects of curcumin and dithio
erythritol added into bull semen extender on sperm parameters, lipid peroxida
tion, total glutathione and antioxidant potential levels of bull spermatozoa
following the freeze/thawing process. Twenty-seven ejaculates obtained from
three bulls were included in the study. Each ejaculate that was splitted into five
equal groups and diluted in a Tris-based extender containing curcumin (0.5
and 2 mm), dithioerythritol (0.5 and 2 mm) and no additive (control) was
cooled to 5 C and frozen in 0.25-ml French straws. The extender supple
mented with 0.5 mm dose of curcumin led to lower percentage of total abnor
mality (20.40 ± 2.36%) when compared to the control (30.60 ± 1.47%,
P < 0.05). Curcumin and dithioerythritol at 0.5 mm provided a greater protec
tive effect in the membrane functional integrity (54.40 ± 2.09% and
50.00 ± 2.68%), in comparison with control (37.20 ± 1.77%, P < 0.001).
Supplementation with antioxidants did not significantly affect the lipid peroxi
dation and antioxidant potential levels, while the maintenance of total glutathi
one levels in curcumin 0.5 mm was demonstrated to be higher than that of
control, following the freeze/thawing (P < 0.05). Supplementation with these
antioxidants prior to the cryopreservation process may be recommended to
facilitate the enhancement of sperm cryopreservation techniques.