Artificial insemination (AI)
AI was carried out with a curved glass pipette whose caliber, outside diameter and length were 4.0 mm, 6.0 mm and 24.0 cm, respectively. The bend was pro- duced by heating the pipette in a flame at 5.0 cm from one end. To induce ovulation, female rabbits received
an intravenous injection with 100 IU of human chori- onic gonadotropin (hCG; Puberogen, Sankyo Yell,
Tokyo, Japan) at 7 h before AI was performed. All the females were inseminated with 50 millions of post-thaw motile spermatozoa cryopreserved as described above,
with inseminated volumes with varying (1.5 to 2.5 ml of the semen per female) depending on the straws. Preg- nant females were transferred to cages containing nest boxes. After delivery, the litter size and condition of the offspring were recorded.