Frozen storage of ram semen II. Causes of low fertility after cervical insemination and methods of improvement

Research up to 1993 is reviewed. Freezing and thawing of ram semen causes ultrastructural, biochemical and functional damage to a significant proportion of spermatozoa. These changes are accompanied by a reduction in motility, impaired transport and decreased viability of spermatozoa in the female genital tract, and reduced fertility after cervical insemination. s used to improve the fertility after cervical insemination include increased concentration of spermatozoa in the inseminate, treatment of ewes with or addition to the semen of hormones, double and deep cervical inseminations. The most effective method is to increase the depth of deposition of frozen-thawed semen into the cervical canal. Recently developed transcervical insemination techniques achieve deep cervical insemination or even uterine deposition of semen. However, at present satisfactory and reliable lambing results are only obtainable by using intrauterine insemination by laparoscopy.