Cryopreservation of the Semen Collected by Electroejaculation from the Hokkaido Brown Bear (Ursus arctos yesoensis)

Abstract

Four adult Hokkaido brown bears were used as semen donors, and semen characteristics were examined before freezing and after thawing. A total of 10 electroejaculates were diluted with Tris-egg yolk extender and cooled to 4°C over 90 min. Spermatozoa were equilibrated with 4.7% glycerol for 80 min. Semen packed in 0.25 ml plastic straws were frozen with liquid nitrogen vapor. Percentages (mean ± SD) of motile and live sperm were 96 ± 2 and 86.5 ± 7.2% before freezing, and 43 ± 5 and 67.4 ± 3.9% after thawing, respectively. Although the number of progressively motile sperm after thawing varied among samples (1.8 ± 1.2 × 10⁸ cells/ejaculate), frozen semen in the present study might serve for artificial insemination.