Cluster-of-differentiation antigen 9 (CD9) gene expressed in the male germ line stem cells is crucial for sperm–egg fusion, and was therefore selected as candidate gene for boar semen motility and kinematic characteristics. This study was performed to investigatetheir association with semen motility and kinematic characteristics. DNA samples from 96 Duroc pigs with records of sperm motility and kinematic characteristics [Total motile spermatozoa (MOT), Curvilinear velocity(VCL), Straight-line velocity(VSL), the ratio between VSL and VCL(LIN), Amplitude of Lateral Head displacement(ALH)] were used in present study. A single nucleotide polymorphism (g.358A>T) in intron 6 was associated with MOT, VCL, VAP and ALH in Duroc population (p < 0.05). Therefore, we suggest that the porcine CD9 may be used as a molecular marker for Duroc boar semen quality, although its functional effect was not clear yet. These results will improve the understanding of the functions of the CD9 in spermatogenesis within the reproductive tracts, and will shed light on CD9 as a candidate gene in the selection of good sperm quality boars.

• Yong-dae Jeong(National Institute of Animal Science, Rural Development Adminstration)
• Eun Seok Cho(National Institute of Animal Science, Rural Development Adminstration)
• Jae-Seok Woo(National Institute of Animal Science, Rural Development Adminstration)
• Soo Jin Sa(National Institute of Animal Science, Rural Development Adminstration)