Objective:To evaluate the effect of cooling rates, selenium supplementation, and three semen extenders on cooled and frozen-thawed Saanen buck sperm.Methods:Twenty Saanen bucks were divided into two groups:the selenium supplemented group and the control group. Ejaculates were collected once weekly by artificial vagina. The first experiment examined the effects of cooling rates and selenium supplementation on semen characteristics of Saanen bucks. Pooled semen was diluted with triladyl extender and split into two aliquots for slow and fast cooling. The second experiment explored the effect of selenium supplementation and semen extenders on post-cryopreserved sperm quality. Ejaculates from each group were divided into three aliquots and diluted with three extenders (i.e. clarified egg-yolk, whole egg yolk, Tris without egg-yolk extenders). All samples were cooled for 2 h at 4 ℃ and frozen at -196 ℃ for 24 h. The sperm characteristics such as sperm motility, acrosome integrity, normal morphology, and viability were evaluated by using a phase-contrast microscope. Results:In the first experiment, all sperm characteristics were significantly increased in selenium supplemented samples when slow cooling was used (P<0.05). In the second experiment, in cooled semen, sperm motility and viability were significantly increased in both clarified egg yolk and Tris without egg yolk extenders in selenium supplemented samples as compared with whole egg yolk extender, respectively (P<0.05). After freezing-thawing, all sperm parameters of selenium supplemented samples in clarified egg yolk extender were significantly greater than those in Tris without egg yolk extender (P<0.05). However, normal morphology and acrosome integrity of selenium supplemented samples in whole egg yolk extender were similar to those of selenium supplemented samples in clarified egg yolk extender. Conclusions:The characteristics of cooled and post-cryopreserved sperm are greater when clarified egg yolk extender is used in semen from selenium supplemented bucks.