We studied the effect of the newly synthesized cryoprotectant EPG-20 (
polyethylene glycol ester with polyunsaturated fatty acids, mol.mass 2
0 kD) on the freezability of boar spermatozoa, Semen samples were froz
en by the pelleting method of Nagase-Niwa, as well as in 20-ml aluminu
m tubes. The addition of 0.5 % EPG-20 to the Serdica cryoprotective me
dium preserved the semen quality to a greater extent than the control
medium containing no EPG-20. It was found that freezing in aluminum tu
bes resulted in higher sperm motility, survival rates and percentage o
f intact spermatozoa than when cells were frozen in the form of pellet
s, the differences being statistically significant (p<0.001). Electron
-microscopic observations revealed that the medium supplemented with E
PG-20 manifested better protective effects on sperm ultrastructure. Hi
ghest cryosensitivity was recorded in sperm head plasmalemma, acrosome
and mitochondria. The nucleus and axial complex displayed a relative
cryoresistance.