SAN ANTONIO, Texas (Reuters) - Fast-food chain Panera Bread has loosened its standards for animal welfare and so-called clean ingredients in its food ahead of a planned IPO, according to internal company documents seen by Reuters.

Its stores across the U.S. were directed in late February to begin removing signs and artwork that include the phrases "No Antibiotics Ever," "Vegetarian Fed," "Grass Fed Pasture Raised," "Animal Welfare," or any mention of "Hormones," the internal documents said. The work is set to be completed by March 27, according to the documents.

The soup and sandwich company, seen as having higher standards than many competitors for sourcing ingredients, recently changed internal policies to remove the requirement its suppliers only use cattle that are pasture-raised, the documents said.

Its new policy allows the use of some antibiotics in pork and turkey products, and allows chicken and cattle to be fed with feed containing animal products.

The relaxing of standards marks a shift in corporate strategy for Panera, which the internal documents refer to as an "evolution" of "clean and animal welfare policies."

Asked to comment, a Panera spokesperson said in a statement: "As we grow to reach more guests, we continue to hold ourselves to high standards for the ingredients we use and are continuously making changes to our menu to deliver high quality products."

Based near St. Louis the chain has more than 2,000 stores in the U.S. and Canada. It was acquired and taken private in 2017 for $7.5 billion by Luxembourg-headquartered private equity firm JAB Holdings. Last May, Panera Bread announced it was planning an eventual IPO.