OTTAWA (CP) — A grim summer for western farmers got worse Friday when Canada lost a major trade ruling on wheat exports to the United States. The U.S. Commerce Department ruled that Canadian durum wheat and hard red spring wheat shipments are subsidized and being dumped in the United States. Mad cow disease, drought and grasshoppers have ravaged Prairie beef and grain producers, and the last thing they needed was a thumbs-down at the trade table, said Neal Hardy, president of the Saskatchewan Association of Rural Municipalities. ‘‘We just come through drought. We just come through grasshoppers. We’ve come through BSE (mad cow disease) in our cattle industry and now a tariff added on,’’ he said. ‘‘Tie them all together and that’s one more impact that we don’t need out there as farmers in Canada.’’ Duties of 14.16 per cent should be imposed on Canadian hard red grain wheat and 13.55 per cent on Canadian durum wheat, the ruling said. Canada is unhappy with the decision and is preparing to fight back, said Ralph Goodale, minister responsible for the Canadian Wheat Board. ‘‘We think it’s wrong in fact and wrong in law,’’ he said. ‘‘And we’ll be considering every means by which we can oppose this decision.’’ Goodale would not say exactly how the federal government might respond. ‘‘We’ll consider very carefully what is the most effective way to make our point,’’ he said. Canada may have opportunities to appeal the ruling under the North American Free Trade Agreement or the World Trade Organization. The U.S. International Trade Commission now has 45 days to issue a final report, which will determine how badly Canadian grain exports are hurting U.S. producers. ‘‘The critical decision will be in a month or two when the (trade commission) which is a somewhat more independent and arm’s length agency than the U.S. government, when it makes a determination with respect to injury,’’ said Goodale. ‘‘That is really the crucial question.’’ Final duties on the exports would only apply if the ITC found the Canadian wheat threatened U.S. producers, said a statement by Pierre Pettigrew, the federal trade minister. Wheat board chairman Ken Ritter said Canadian farmers are being hurt by protectionist politics in the United States.