The Effects of Egg Yolk Concentration and Particle Size on Donkey Semen Preservation

The aim of the study was to evaluate the effect of concentrations of egg yolk on cooling preservation and particle sizes on cryopreservation for donkey semen. Two experiments were carried out: (1) Determination of a suitable concentration of egg yolk during donkey semen cooled storage; and (2) evaluation of effects of egg yolk particles sizes on sperm quality after freezing-thawing. For experiment 1, the different concentrations (0%, 0.5%, 1.0%, 1.5%, 2.0%, and 2.5%) of egg yolk were added into the cooling extender, and the semen samples were preserved at 4°C for evaluation every 24 hours. The results demonstrated that the group of 1.0% egg yolk displayed higher total motility after 96 hours of preservation (P < .05). For experiment 2, the fresh egg yolk was treated with different powers of ultrasound (400 W, 600 W, and 800 W) for different times (2, 5, 10, 20, and 30 minutes). The sperm frozen in the extenders supplemented with the egg yolk treated by different combinations of ultrasonic power and ultrasonic time, including (400 W, 10 minutes), (400 W, 15 minutes), (600 W, 2 minutes), (800 W, 2 minutes), (800 W, 20 minutes), and (800 W, 30 minutes) displayed higher values of motility compared with the control group (P < .05). In conclusion, the cooling extender containing 1.0% egg yolk can be successfully used for donkey semen cooling preservation, and the extender supplemented with small egg yolk particles could effectively improve donkey sperm qualities after freezing-thawing.