The objective of this study was to assess the effect on post-thawed sperm motility, viability and acrosome integrity of boar semen frozen in the freezing extender with chicken or duck egg yolks. The Sperm rich fraction of ejaculates from three Duroc boars were collected by a glove-hand technique. Samples with more than 80% motile sperm were used for this experiment. Semen was diluted with freezing extender (LEY) containing 11% (v/v) lactose, 20% (v/v) hen egg yolk with 3.5% (v/v) glycerol, and 0.5% (v/v) Orvus Es Paste(OEP, Nova Chemical Sales Inc., Scituate, MA. USA) to yield a final sperm concentration of 5×108 cells/ml. Following complete dilution, semen samples were loaded in 0.5 ml French medium straws (IMV technologies, France) and transferred to programmable semen freezer (SY-LAB Gerate GmbH, Austria). For freezing the semen samples, each straw was cooled from 5℃ to — 5℃ at 6℃/min, auto-seeding at — 5℃ and held for 60sec, samples were then cooled from — 5 to — 80℃ at 40℃/min, and thereafter from — 80℃ to — 150℃ at 60℃/min. The yolks used were sourced from fresh chicken and duck eggs. To evaluate the post-thaw sperm quality, semen was thawed at 38℃ for 20 sec and sperm motility, viability and acrosome integrity were assessed. Motility was assessed for %motile cell characteristics using computer-assisted semen analysis (CASA; SAIS SI-100, Medical supply, Korea). The percentage of sperm viability was assessed using LIVE/DEAD® sperm viability kit (Molecular probes, Eugene, OR, USA). The acrosome integrity was assessed by FITC-PNA staining. Sperm quality in terms of motility, viability and acrosome integrity showed higher after freezing in medium containing duck yolk than chicken yolk. However, there was no significant difference in sperm quality for the different types of yolk(p>0.05). * The result of this study showed that there was no significant difference between the egg yolk types when considering the sperm motility, viability and acrosome integrity of boar semen frozen in the freezing extender with chicken or duck egg yolks.