PARIS, Feb 17 (Reuters) - U.S. investment firm Artisan Partners called on French food group Danone to separate its medical nutrition business from its baby foods unit to boost returns, French daily Le Figaro reported on Wednesday. Artisan Partners, which said it had built up a stake of more than 3% in the Activia yoghurt maker, also said that Danone’s Asian Mizone unit could be offloaded. “Medical nutrition must be separated from baby nutrition, two businesses that have nothing to do with each other,” Jan Bennink, an adviser for Artisan Partners, told Le Figaro. Bennink also said Danone’s brands Evian, Badoit and Volvic were key priorities for the company. Danone came under more pressure last week to make management changes as some shareholders voiced criticism of weak returns at the food group and demanded it split the roles of chief executive and chairman.