It’s a favourite grievance in President Donald Trump’s Twitter blasts at his northern neighbour: “Canada is charging massive Tariffs to our U.S. Farmers … Canada has treated our Agricultural business and Farmers very poorly.”The source of Trump’s ire is the supply-management system that controls milk production in Canada and limits imports from the U.S.; America’s NAFTA negotiators want it dismantled.Even in Canada, critics view supply management as an anti-competitive tool that artificially inflates consumer prices, while other trading partners have also complained. But in the United States’ troubled dairy heartland, where low prices are forcing farm after farm into bankruptcy, many producers have taken a much different view lately — they’re actually embracing supply management as a potential saviour.Representatives of the Ontario dairy marketing board toured Wisconsin in March and Michigan last month, drawing hundreds of farmers eager to learn how the system works. More trips are planned for later this year to Ohio and Pennsylvania.“We had over 350 people participate in those five (Wisconsin) meetings — three of those meetings were standing room only,” said Darin Von Ruden, president of the Wisconsin Farmers Union. “We ended up way underestimating the amount of interest.”