Supplementation of an extender containing 5% glycerol with 100 mMtrehalose has been also reported to improve the fertility of frozen-thawed ram spermatozoa following artificial insemination in ewes [29]. In a recent report in mice [12], frozen-thawed spermatozoa cryopreserved with 300 mMtrehalose retained significantly better fertility (79%) than those frozen in 0.3 M glycerol (11%).