QUAIL EGG-YOLK - A NOVEL CRYOPROTECTANT FOR THE FREEZE PRESERVATION OF POITOU JACKASS SPERM

For many years, attempts have been made to establish a sperm bank for the Poitou jackass population which is threatened with extinction. Unf ortunately, no cryopreservation technique has ever been described for spermatozoa of this species. In an attempt to find a suitable techniqu e, we studied the relative effectiveness of chicken egg yolk and quail egg yolk in preserving the motility and characteristics of movement o f Poitou jackass spermatozoa during the freezing-thawing process. Seme n was diluted to 60 x 10(6) sperm/ml in a preservation medium containi ng 4% (v/v) glycerol with 0, 2, 5, 10, 15, or 20% (v/v) of chicken or quail egg yolk. The chemical composition of these two eggs was compare d. Effects were assessed using an automated analyzer which measured cu rvilinear velocity (VCL), straight line velocity (VSL), and the veloci ty of the average path. Linearity was defined as VSL/VCL x 100. The am plitude of the lateral head displacement was also measured. It was fou nd that after the freeze-thaw process, quail egg yolk improved the per centages of motile and progressively undulating spermatozoa and the mo vement characteristics compared with chicken egg yolk. The optimal con centration of quail egg yolk was 10%. The general composition of the t wo types of egg yolk were similar, but quail egg yolk contained signif icantly more phosphatidylcholine, less phosphatidylethanolamine, and a smaller ratio of polyunsaturated to saturated fatty acids than chicke n egg yolk. The improvement of motility for frozen-thawed Poitou jacka ss spermatozoa using frozen-thawed quail egg yolk compared to chicken egg yolk may be due to the differences in composition of the two yolks . (C) 1997 Academic Press.