Frozen storage of ram semen I. Processing, freezing, thawing and fertility after cervical insemination

Research up to 1993 is reviewed. Various methods for processing, freezing and thawing of semen have been elaborated and their effect on survival and fertility of spermatozoa have been examined in vitro or in fertility tests. Diluents initially used for freezing bull semen had their limitations and were modified or replaced by new media. The freezing diluents investigated included citrate-sugar-, milk-, lactose-, saccharose-, raffinose-, trisbased and other media containing protective agents (mainly glycerol and egg yolk), and other substances including antioxidants. Satisfactory sperm survival rates were obtained with a number of diluents and different combinations of the factors studied. Lambing results after cervical insemination varied depending on the parameters examined in the freezing technology or at insemination, but were low in comparison with those obtainable with fresh diluted semen. As a consequence, cervical insemination with frozenthawed semen had a relatively limited application in sheep.