Avian Semen Cryopreservation: What Are the Biological Challenges?

Abstract

The value of the ability to cryopreserve and store germplasm has long been recognized for indefinite preservation of genetic material, especially for at-risk populations. In contrast to domestic livestock species, cryogenic storage of poultry semen is not reliable enough for germplasm preservation. The relatively low fertilizing ability of frozen/thawed poultry sperm most likely results from physiological sensitivity to the cryogenic process coupled with the requirement for prolonged sperm functionality in the hen reproductive tract; however, the concept of defining these physiological challenges has been underemphasized. For example, alterations in membrane carbohydrate content and diminished energy production in frozen/thawed sperm have important implications for successful gamete interaction. Recent data suggests that both glycoconjugate content and adenosine triphosphate (ATP) generation are affected by cryopreservation. Moreover, susceptibility to the cryogenic process seems to vary among lines and strains of birds, as illustrated by line-specific differences in ATP concentrations of frozen/thawed sperm from pedigreed commercial layers. Research based on biochemical and molecular comparisons of sperm among lines may lead to identification of factors that influence the freezability of poultry semen.

Specific features of in vivo and in vitro sperm storage in birds

“…Their low cytoplasmic content and relatively large surface of membranes exposed to adverse micro-environmental conditions (Lake, 1984;Etches, 1996) explain why the overall biophysical characteristics of membranes, including resistance to osmotic shock and membrane fluidity, appear critical for the success of cryopreservation (Blanco et al, 2000;Blesbois et al, 2005, 2006a andb). As a consequence, membrane damage induced by cryopreservation also results in impaired motility and decreased concentrations of various metabolic factors, including ATP concentration (Long, 2006). Limitation of membrane damage induced by cryopreservation has been attempted using specific diets to modify the lipid composition of the sperm membrane, including its cholesterol/phospholipid ratio and fatty acid composition (Ansah and Buckland, 1982;Blesbois et al, 1997).…”

Sperm variables as predictors of fertility in Black Castellana roosters: use in the selection of sperm donors for genome resource banking purposes

“…Spermatozoa are therefore the primary cell types preserved in most emerging genome resource banking projects . Since the fertilisation capacity of cryopreserved poultry sperm is dramatically lower than that of any domestic mammalian species (Long, 2006), fresh semen of high quality is required; the succession of thermal, osmotic and mechanical stresses suffered during cryopreservation (Blesbois and Brillard, 2007) renders low quality sperm ineffective. Since sperm quality variables and the capacity to survive cryopreservation show strong within-breed variability (Nishiyama, 1961;, in vitro semen evaluation for the selection of the best semen donors is necessary; only the most fertile roosters should be used as donors in genome resource banking projects.…”

Implementing artificial insemination as an effective tool for ex situ conservation of endangered avian species

“…Detailed reviews are available [12,44]. It is noteworthy that fertility with refrigerated or thawed sperm in the Golden eagle has mimicked the success achieved using fresh semen (Blanco, unpublished observations).…”

“…Inseminate volumes range from 5 to 10 mL in passerines [44], 33 to 150 mL in medium-sizes species (i.e., falcons, monals, trapogans) [48,50], 100 to 200 mL in cranes [26] and 600 to 1400 mL in ostriches [44]. The smaller the female's size, obviously the lesser the ability to accommodate a larger inseminate volume.…”