Studies on the Ability of Ram Semen Extenders to Preserve Sperm Quality During Storage at 23 °C

Abstract

Artificial insemination facilitates propagation of elite genetics and thus rapid genetic gain in animal agriculture. A cornerstone of the ease of use of this technology is the successful storage of semen, either in liquid or frozen form, to prolong the fertile lifespan of spermatozoa. This is achieved by reducing the metabolic rate of spermatozoa through controlled reduction of temperature and/or change of the chemical properties of storage diluents. However, the reduction of temperature during semen preservation is damaging to spermatozoa and can reduce their fertility, particularly during frozen storage. Reduced temperatures induce harmful temperature dependant phase transitional damage. This damage occurs in the form of DNA fragmentation, increased radical synthesis, disruption to the homeostatic architecture of the plasma membrane, and ceasing of cellular respiration functions. Collectively, this is known as cold shock and can happen during both liquid and frozen storage. When spermatozoa are subjected to cold shock, their viability, motility and fertilising capabilities are reduced, as is the efficiency of their use in artificial insemination programs. This thesis will investigate new and emerging techniques to improve the liquid storage of ram spermatozoa. It will examine if emerging pro-survival factors such as pyruvate, melatonin and L-carnitine prolong the lifespan of ram spermatozoa in liquid storage at various temperatures. The effectiveness of these compounds to facilitate room temperature storage for ram spermatozoa will be explored, an advance that may have logistical benefits for some AI programs conducted in the days following semen collection.