Application of liquid semen technology under the seasonal dairy production system in New Zealand.

Systems for preserving semen in liquid form for artificial insemination were developed before cryopreserved semen became widely available in the 1960s. Advantages of liquid semen include reduced number of sperm per dose, reduced storage and transportation costs, increased insemination speed and safety in the field. A liquid semen dose requires one tenth the sperm number in a frozen semen dose to achieve equivalent fertility (24 day non-return rate: 67.6% for liquid versus 67.8% for frozen). The main disadvantage of liquid semen is its relatively short shelf life, thus limiting its application mainly to countries, like New Zealand and Ireland, with predominantly seasonal dairy production systems. Nevertheless, successful application of liquid semen technology can improve the rate of genetic gain by increasing the utilization of elite sires. This brief review covers the principles of liquid semen preservation and describes why and how this technology is implemented by Livestock Improvement Corporation in New Zealand.