Labor contract negotiations at ports along the West Coast have stalled shipments of U.S. meat and goods to export markets, and that’s hitting Iowa farmers hard. At stake: millions of dollars’ worth of products and hard-won trade relationships with export partners throughout the world, they say.

And the damage is getting worse each day, said Chad Hart, associate professor of economics at Iowa State University. "The longer this goes on, the more of an impact it will have," he said.

Behind the port slowdown is an ongoing labor contract negotiation between management representatives of the Pacific Maritime Association and the International Longshore and Warehouse Union. The worker contracts ex­­pired in July 2014. For more than three months, the union members have engaged in a worker slowdown because they are working without a contract. Workers at all 29 ports from Bellingham, Washington, to San Diego have engaged in the worker slowdown; workers at the Long Beach, Calif., and Los...