DES MOINES, Iowa (AP) — McDonald's Corp. says it will require its U.S. pork suppliers to provide plans by May to phase out the use of stalls that confine pregnant sows.The Humane Society of the United States is touting Monday's announcement as a major victory in its fight to stop the use of the stalls it considers inhumane.Some of McDonald's suppliers have already announced plans to phase out the stalls.The joint statement released Monday by McDonald's and the Humane Society says the fast food chain wants all its of its suppliers to do so.McDonald's spokesman Dan Gorsky says suppliers including Smithfield Foods and Cargill have made progress in adopting alternatives to so-called gestation crates and the company will discuss the next steps with all of its suppliers after receiving their plans.