Cryopreservation is a non physiological method
that involves a high level of adaptation of
biological cells to the osmotic and thermic s
hocks that occur both during the cooling-freezing
procedure and during the thawing procedure. Bird
spermatozoa are cells that contain very little
cytoplasm and very large relative surface of plasma
tic membranes. The only cytoplasmic organites are
mitochondria. The nucleus contains
very condensed chromatin.
Damages occurring during the freezing-thawing procedures affect mainly cellular membranes
(plasmatic and mitochondrial) and in the worth case
the nucleus. Such damages affect fertility and its
duration. The duration of fertility is a very important
factor in birds due to the long term storage of
semen in the utero-vaginal glands of the female.
The main critical points that affect cell structures and metabolism during cryopreservation are 1) the
interactions between the spermatozoa and the internal
cryoprotectant agent added to the sperm to limit
temperature stress, 2) the temperature curve and 3)
the type of semen packaging. In consequence,
many studies has been performed to find the best
cryoprotectant agent, the highest combination of
freezing and thawing temperature curves and the least
deleterious system of semen packaging for
spermatozoa that permits traceability
and respect of healthy and sanita
ry conditions. Their results have
given rise to different procedures depending on th
e species and sometimes on different breeds of the
same species.