The present study was performed to determine the protective role of dietary selenium (Se) yeast supplementation in porcine circovirus type 2 (PCV2) infected mice.Forty eight Kun Ming female mice were randomly assigned to Se yeast group (0.3%Se+basal diet,n=24) and control group (basal diet,n=24).After 3 days of adaptive feeding and 15 days treatment period with the experimental feed,all the mice were challenged by intraperitioneal injection of PCV2 at the dose of 2000 TCIDso (50% tissue culture infection dose,TCIDso).Serum total superoxide dismutase (SOD) activity,malondialdehyde (MDA) levels,tumor necrosis factor alpha (TNF-a),C-reactive protein (CRP) and interleukin-1 beta (IL-1β) levels were measured at 5th,lOth,15th,20th day after infection.The PCV2 virus load in liver,spleen,lung and microscopic lesions in the liver,spleen and lung also were determined on 5,10,15,and 20 after infection.Supplemental Se decreased (P<0.05) the serum levels of TNF-a,but had no significant effect on SOD activities and the levels of MDA,CRP and IL-ip between experimental and control groups.Dietary Se yeast supplementation had little effect on the PCV2 virus load in liver,spleen and lung.However,mice in the selenium yeast group showed a significant decrease m microscopic lesion scores in the lung and spleen compared with those in the control group (P<0.05).These data indicate Se yeast attenuated the PCV2 infection through altering the systemic inflammation and maintain the normal organ morphology.