The protective effect of egg yolk from different avian species during the cryopreservation of Karayaka ram semen

Egg yolk is one of the most widely used cryoprotective components for sperm preservation and a wide range of factors affect its action on sperm motility, viability and fertilizing ability. The aim of this experiment was to determine the effect of different species egg yolk, namely the domestic chicken (Gallus gallus domesticus), the goose (Anatidae anser), turkey (Meleagris gallopavo), duck (Anatidae anas platyrhynchos), Japanase quail (Coturmix japonica) and chucker (Alectoris chukar) on sperm quality following cryopreservation of ram semen. Ejaculates were collected using the artificial vagina from three Karayaka rams and spermatological characteristics assessed for the pooled semen. Semen samples were evaluated as split ejaculates in the trial and samples extended with a Tris-citric acid-glucose extender containing the different avian egg yolk (15%) and glycerol (5%). The semen straws were equilibrated at 4°C for 2h, frozen in liquid nitrogen vapour (for 15min at −120°C) and stored in liquid nitrogen (−196°C). After thawing (37°C for 30s), sperm motility, viability, abnormal acrosome and membrane integrity (HOST) were evaluated. Results showed chucker egg yolk to have the best cryoprotective effect in terms of the highest sperm motility (54.0%), compared to the other five avian egg yolks (p <0.05) evaluated. Sperm frozen in chucker egg yolk also showed a higher percentage viability (59%), than sperm stored in quail and turkey egg yolk (p <0.05). The percentage of acrosomal abnormalities after thawing was lower in the chucker egg yolk, than the other species (p <0.05). There was no significant difference in sperm membrane integrity between the egg yolks, except for the quail (p <0.05). Results suggest that chucker egg yolk could be used as an alternative for chicken egg yolk, in a semen extender in cryopreservation, but it warrants further evaluation in fertility trials.