RECENT PROGRESS IN THE PRESERVATION OF RAM SEMEN

The processing and storage of ram semen reduce the motility and disrup t the membrane integrity of spermatozoa. It is generally assumed that these changes are detrimental and are associated with a loss of fertil ising capacity. Despite many years of empirical research that has esta blished a variety of methods for the processing, storage and inseminat ion of spermatozoa, fertility is generally lower after cervical insemi nation with stored than fresh semen, The components of the sperm cell responsible for this low fertility are not clearly understood, However , recent evidence suggests that while many spermatozoa remain motile a fter storage, the membranes of the motile cells are destabilised to th e point where they may not survive Further ageing in the female tract after cervical insemination. These membrane changes are similar to the capacitation and acrosome reaction of spermatozoa, Thus, stored sperm atozoa may require less capacitation time in the female tract, and may readily fertilise oocytes if placed in their immediate vicinity, as w ith in vitro fertilisation, tubal or even intrauterine insemination. I t may be possible to prevent or reverse some of these membrane changes , for example using antioxidants, and thus improve fertility following cervical insemination of sheep.