McALLEN, Texas — Texas cattle rancher Charles Kothman is down to six calves and their mothers after selling off 80 animals in recent months. The drought that has baked pastures and dried ponds has ranchers in Texas and Oklahoma — the nation’s top two beef producers — culling their herds. Some have sold off all their cattle, but Kothman is hanging on and hoping for rain. “I may get to the point that I say ‘no’ and take them over to the sale barn,” said Kothman, whose ranch is about 70 miles south of San Angelo. Some