L. Gillan1, G. Evans, W.M.C. Maxwell
1Department of Animal Science, University of Sydney, NSW, Australia
Tóm tắt
The effect of cryopreservation on the capacitation status and fertility of ram
spermatozoa was observed. After the chlortetracycline staining technique was
validated for ram spermatozoa, it was applied to fresh or long-term
frozen-stored spermatozoa. Fresh spermatozoa displayed mainly the F pattern
(non-capacitated; 61·3%), becoming B pattern (capacitated;
54%) and AR pattern (acrosome reacted; 41%) with incubation (6 h
at 37°C). In contrast, frozen spermatozoa displayed the B pattern
(65· 9%), becoming the AR pattern (64·2%) with
incubation. This demonstrates that cryopreservation may cause membrane changes
in ram spermatozoa functionally equivalent to capacitation. The differences in
capacitation status did not affectin vitro fertilization
rates between fresh and frozen spermatozoa, but pregnancy rates at Day 18
after intrauterine artificial insemination were higher for fresh than for
frozen spermatozoa. This difference was not evident at Day 50, possibly as a
result of the high embryonic loss between Days 18 and 50 when fresh
unincubated and frozen incubated spermatozoa were inseminated. Further
research is necessary to determine what part of the cryopreservation process
is responsible for the membrane changes in ram spermatozoa.
