Supplementation of ram semen extender to improve seminal quality and fertility rate

In sheep, artificial insemination serves as an important technique for breed improvement. In this context, genetic material from a small number of superior sires can be used in a large number of females. During this process, the storage of ram sperm may influence the efficiency of artificial insemination. Two main methods are currently used for ram semen storage: liquid storage and cryopreservation. The oxidative stress during the storage process can injure ram sperm and in some cases this leads to irreversible damage at the cellular level. To reduce such negative effects, different preservation protocols, extenders and protective components have been tested to improve ram sperm quality and to achieve greater fertility rates. This review provides an overview of the recent progress in extender supplementation using antioxidants and other compounds to improve ram semen quality parameters and fertility rates. It will emphasize on enzymes, vitamins, amino acids, proteins, some plant extracts and other compounds such as sugars, seminal plasma and fatty acids that can be used to supplement the extenders to reduce the formation of oxidants in ram semen and maintain its quality and enhance its fertility. It will also stress on how these supplements act, what were the tested levels giving beneficial effects on motility, viability, plasma membrane integrity and DNA fragmentation in liquid, cooled and post-thawing semen?