A proposal for an online auction that could shake up the U.S. pricing model for cattle is set to make its public debut on Friday after a test run last week, with the support of a unit of the world’s largest meatpacker. Producers have worried for years that the country’s existing method for pricing cattle headed to slaughter can undervalue animals because it is based partly on a declining market of cash sales that are concentrated in certain geographic areas. Read more at Reuters…