The effect of the compatible solutes proline, glycine betaine and trehalose in
Tris-based diluents at varying pH, concentrations of egg yolk or glycerol on
the post-thaw motility characteristics and fertility of ram sperm was
examined. In addition, the amino acid glycine was compared with proline,
glycine betaine and a standard Tris-based diluent. Post-thaw motility was
assessed using a Hamilton–Thorn motility analyser. In the presence of
glycerol and egg yolk, proline and glycine betaine improved the post-thaw
motility characteristics of ram sperm. Regardless of the pH of the diluent at
which semen was frozen, the percentage of motile sperm was higher when frozen
in the presence of proline or glycine betaine than in their absence, whereas
proline and glycine betaine only improved the progressive and rapid
percentages of sperm for semen frozen in diluents at pH lower than 7.0. When
semen was frozen in the absence of egg yolk or glycerol all the motility
characteristics were reduced. Increasing the concentration of egg yolk in the
diluent from 5% to 10, 15 or 20% had no effect on the post-thaw
motility of sperm. The addition of 27 mM of proline or glycine betaine to the
diluent also improved post-thaw motility. However, at a concentration of 81
mM, proline and glycine betaine had a detrimental effect on the percentage of
motile sperm. Trehalose had no effect on the motility of sperm frozen in
glycerol-containing diluents, but motility was lower after cryopreservation in
glycine than in Tris-, proline- or glycine betaine-based diluents. There were
no differences in the fertility of sperm frozen in Tris-, proline or glycine
betaine diluents after cervical or laparo-scopic insemination of ewes.
Achiral amino acid glycine acts as an origin of homochirality in asymmetric autocatalysis
