Resumen de Short communication. The percentage of egg yolk in the freezing media affects mouflon (Ovis musimon) epididymal sperm cryosurvival

Lucía Martínez Fresneda, Milagros Esteso, Adolfo Toledano Díaz, Cristina Castaño, Rosario Velázquez, Antonio López Sebastián, Paloma Prieto, Francisco Alberto García Vázquez, Julián Santiago Moreno

• Sperm cryopreservation protocols are not well defined in many wild species such as the mouflon. The aim was to study the effect of different concentrations of EY on mouflon epididymal sperm cryosurvival. Samples were collected by the flushing method and cryopreserved by the conventional freezing technique in straws using a TEST (TES, Tris, glucose) 5% v/v glycerol medium containing either 6% v/v (n=16) or 12% v/v (n=13) clarified EY. The membrane integrity, acrosome integrity, motility, and morphological abnormalities were assessed in fresh and frozen/thawed samples. Fresh sperm quality parameters did not differ between groups except for the acrosome integrity that was lower in the TEST-6% EY than in the TEST-12% EY group (88.9 ± 2.1% vs 94.7 ± 0.8%). Membrane integrity (31.6 ± 4.6% vs 11.6 ± 4.5%), total motility (32.8 ± 4.6% vs 17.2 ± 5.6%), progressive motility (13.3 ± 2.7% vs 6.1 ± 2.9) were higher in frozen-thawed sperm with TEST-6% EY than with TEST-12% EY (p<0.05). Other motility parameters such as curvilinear velocity, straight-line velocity, average path velocity and amplitude of lateral head displacement were also higher (p<0.05) in frozen-thawed sperm with TEST-6% EY. Frozen-thawed acrosome integrity (85.1 ± 3.3% vs 91.9 ± 2.3) and morphological abnormalities (34.0 ± 3.7% vs 29.1 ± 3.6%) did not differ between extenders. In conclusion, high EY concentration had detrimental effects on post-thaw quality parameters, therefore the use of TEST based extender containing 6% EY is recommended for the cryopreservation of mouflon epididymal sperm.