Semen quality and semen storage.

Poultry semen quality and semen storage respectively can be considered in terms of the intrinsic components of spermatozoa and seminal plasma and their properties, and of the oviducal sperm-storage systems and their regulation. However, the focus of this chapter is on the technologies for assessing semen quality and for storing semen in vitro. Semen quality is considered as methods for sperm quality evaluation to identify males of different fertilizing abilities. It is shown that sperm quality assays can be used to predict fertilizing ability and to select the 'best breeders' from a flock of chickens or turkeys when artificial insemination is employed. It may also be possible to select for sperm quality traits in breeding programmes. Sperm quality assays have, however, been shown to be poor monitors of the loss of fertilizing ability that occurs in semen during storage. Semen storage is reviewed in terms of cryopreservation, which enables long-term storage of spermatozoa at -196°C, the temperature of liquid nitrogen, and liquid semen storage, usually at lower than ambient temperatures above 0°C for up to 24 or 48 h. The most significant advance in sperm cryopreservation technology is the recent establishment of poultry sperm banks in several countries - the result of an international realization of the rate of loss of poultry breeds and lines. The background to the cryopreservation technology used in these cryobanks is considered with a view to providing an appreciation of the opportunities and limitations of poultry sperm cryopreservation. Liquid semen storage of chicken spermatozoa at temperatures of around 5°C is a well-established, although little-used, technology. Turkey sperm storage is successfully utilized in commercial breeding operations, but the efficiency of such systems in maintaining sperm fertilizing ability in vitro for 24 h pale into insignificance in comparison to the in vivo oviducal storage system, which can maintain fertilizing ability for many weeks.