[Successful use in horses of deep-frozen semen specimens stored for 18 years]

In 1970 semen from a Haflinger-stallion was frozen by the pellet method. 18 years later semen samples were used to inseminate 4 mares. Inseminations were performed shortly after ovulation with a total number of motile spermatozoa between 150 and 636 x 10(6), the percentage of motile spermatozoa being 20% to 40%. Three mares conceived after a single insemination, one mare got pregnant after 4 inseminations during 3 oestrous periods. Meanwhile, 3 foals were born and one of the mares is still pregnant. The results demonstrate that long-term storage of frozen semen in liquid nitrogen does not impair its fertilizing capacity.