Current status in avian semen cryopreservation

Semen cryopreservation in domestic birds has been studied extensively in the past fifty years. However, efficient methods to freeze semen of chicken of different breeds have emerged only in the last decade of the 20th century. Methods using the cryoprotectants glycerol, dimethyl acetamide and dimethyl sulfoxide, slow or rapid freezing-thawing procedures, pellets or vials or straws packaging have been developed. Other methods have been studied in turkeys, guinea fowl, ducks, ganders and some wild species. They are often less successful than chicken freezing methods with wide intra-species variability. Reliable predictors of suitability of semen for cryopreservation are also needed to improve freezing methods and to optimize the management of frozen semen. The quality of whole fresh semen measured by classical morphologic, metabolic and mobility tests is an indicator. More specialized tests such as membrane fluidity of fresh spermatozoa are indicative of the freezing ability of the gametes. The main use of semen cryopreservation in birds is the ex situ management of genetic resources in the context of dramatic decrease in avian genetic biodiversity. This is achieved through germplasm cryobanks. There are three main national avian germplasm cryobank programmes in 2006, operating in North America, The Netherlands and France. They mainly include semen and blood samples issued from Public Research Lines, indigenous breeds and individual specific genotypes. The future need for semen cryopreservation programmes will focus mainly on three objectives 1) improvement of predictors of male suitability for semen freezing, 2) emergence of standardized methods of semen freezing in species other than chicken and 3) increasing development of avian cryobanks.