(Adds details of site closure notice in paragraphs 1, 2 and 4) By P.J. Huffstutter CHICAGO, Aug 7 (Reuters) - Smithfield Foods, the world's biggest pork processor, is permanently closing 35 hog farm sites in Missouri and laying off 92 employees in October, according to a Missouri Worker Adjustment and Retraining Notification Act (WARN) notice. Murphy-Brown LLC, a division of Smithfield Foods, is "reducing its hog farming operations" across the state and "must reduce its workforce accordingly," the company said in the notice, which affects salaried and hourly workers.