Liquid storage of ram semen: a review

Research from 1930 to 1992 is reviewed with regard to storage of semen at reduced (0-5 degrees C or 10-15 degrees C) and at ambient temperatures. Diluents investigated have included synthetic buffers combined with sugars and egg yolk or its fractions, milk from various sources, glycine, and other substances. Irrespective of the diluent, dilution rate, temperature or conditions of storage, the spermatozoa deteriorate with time of storage. Changes include reduction in motility and morphological integrity of spermatozoa, accompanied by a decline in their survival in the female reproductive tract, reduction in fertility and increased embryonic loss. In critical studies, fertility declined rapidly when semen stored for more than 24 h was used for cervical insemination, but after intrauterine insemination some spermatozoa maintained their fertilizing capacity up to 10 days. Laparoscopic intrauterine or transcervical inseminations could be the means of improvement of fertility. These methods may eliminate the problem of sperm transport through the cervix and ageing of spermatozoa in the reproductive tract, thereby improving fertilization of ova and reducing embryonic loss.