Abstract
The aim of this study was to examine the effect of different concentrations of egg yolk EY (0%, 10%, and 20%) in the semen extender during the cryopreservation process of goat semen out of the breeding season. A total of 12 ejaculates were collected from six Anglo Nubain dairy bucks as two ejaculates for each buck aged between (1-5) years over a two week period by using Electro-ejaculation (EEJ) during the non-breeding season. Post collection, the semen samples were evaluated for motility and mass activity. Subsequently, the semen samples were initially diluted in Tris solution (without Egg yolk or Glycerol) in order to preserve the motility of sperm cells. The semen samples from each buck were evaluated for pre-freezing motility and morphology then divided into three sub-samples and diluted in Tris extender with T1 (control) 0% EY, T2 10% EY, and T3 20% EY. The semen samples were frozen in liquid nitrogen (-196 C). After thawing, the semen samples were evaluated for sperm motility and morphology. The morphology of sperm did not differ among treatments nor between pre-freezing and post-thawing evaluations. However, the motility of semen diluted with 10% EY was (P<0.05) numerically but not statistically higher than semen diluted with 0% and 20% EY. According to the obtained results of this study, it is recommended that a 10% EY level or less be included in the Tris extender during cryopreservation of goat semen for superior motility and morphology results.

Key words: Cryopreservation, egg yolk, goat sperm.