I've got a field of winter rye that I've had the cows on for a few weeks.   I plan to no-till drill some sudangrass into it for summer grazing in a week to 10 days.   Should I spray Roundup to kill the rye or should I just plant the sudangrass into the rye stubble?   I'll be grazing the rye to the ground before drilling no matter what.   Will the rye be to competitive for the sudangrass?  Haven't planted sudangrass on the farm since grandpa sold the Holsteins and quit greenchopping in '77 so looking for any help I can get.