Effect of Viscosity in the Medium for Sperm Cryopreservation of Golden Eagle (<i>Aquila Chrysaetos</i>)

BACKGROUND: The development of assisted reproduction techniques for birds is useful for ex situ conservation but is limited. For the golden eagle ( Aquila chrysaetos ), only artificial insemination procedures using extenders developed over 50 years ago have been described. OBJECTIVE: To evaluate the effect of the viscosity of the cryopreservation medium on the acrosomal reaction ability of A. chrysaetos sperm. MATERIALS AND METHODS: Viscosity was determined in 45 ejaculates. A design using the Lake medium, 6% dimethylacetamide (DMA), and Ficoll (10%, 35%, and 45%) was developed to create conditions of viscosity that was lower, similar, and higher than those determined in fresh semen. RESULTS: The viscosity of fresh semen was 3.2320 mPa/s. In aliquots of the Lake medium supplemented with 6% DMA and 10%, 35%, and 45% Ficoll, the viscosities were 2.1698 mPa/s, 3.5393 mPa/s, and 6.1123 mPa/s, respectively. Post-thaw, in the aliquot with 10% Ficoll, 74% of sperm were alive, with 28% mobility, and 21% exhibited an acrosomal reaction with percentages that were significantly lower (P&lt;0.05) than those observed in sperm frozen with 30% and 45% Ficoll. CONCLUSION: Viscosity has a positive influence on the viability of cryopreserved semen.