Cryopreservation of Boar Semen Using 0.25 mL Straws

The purpose of this study is to establish an optimal protocol to cryopreserve boar semen. The results showed that the optimal procedures should be operated as follows. Firstly, boar semen were pre-diluted with ZORLESCO(ZO) solution and pre-equilibrated at room temperature for 1 h. After adding the extender Ⅰ, spermatozoa were equilibrated at 5 ℃ for 1.5 h, then equal volume of the extenderⅡ was added, holding 2 h for equilibration. Resulting spermatozoa were loaded into 0.25 mL straws and equilibrated for 10 min at 3 cm above the surface of liquid nitrogen (LN) , and submerged into LN promptly. When thawing, straws were put into water bath at 37 ℃ for 30 s. The above procedures yielded the highest post-thaw motility of 0.58±0.03 and the plasma integrity of (63.2±1.2)%, together with the normal acrosome was (51.4±2.6)%. The abnormality of spermatozoa after freezing was the lowest at (14.0±3.0)%.