The nation’s cattle-futures markets are likely to continue a down trend today. Even as investigators became increasingly certain the first and only case of Mad Cow disease in the U-S came from Canada, live cattle futures fell Monday. Late last week, contracts for live cattle and feeder cattle on the Chicago Mercantile Exchange fell the limit. Rules limit any one-day dump or drop to three cents a pound, and as a result, trading shut down within minutes of the open. The trading limit was increased Monday, allowing prices to fall by as much as five cents a pound. But markets usually trade thinly over the holidays. And beef prices have been at historic highs for months now with strong exports and high-protein diets helping fuel continuing domestic demand. The abrupt closing of some overseas markets is likely to mean lower prices for farmers but also cheaper beef at the meat counter. Stocks that fell after the Mad Cow news are already rebounding for McDonalds, Outback Steakhouse and Tyson Foods, and lower beef prices will help other restaurants that have struggled for months with the high price of menu items.