Nov 9 (Reuters) - Dean Foods Co posted a $1.6 billion loss as it took a large charge to reflect a lower value for its fresh dairy business. The company took a $1.9 billion charge to write down goodwill in the dairy business, which it had built up through acquisitions over the years. Falling demand and prices over several years have hurt the value of that business. Excluding the charge, the top U.S. dairy company's earnings beat analysts' estimates. KEY POINTS Q3 20