Braunvieh is a pure breed, actually may be one of oldest breeds on earth with records dating back to 800 BC, and come from the swiss alps. The Brown Swiss was developed off the Braunvieh around 1800 and now they are not genetically similar at all, except the color. The Braunvieh aren't a cross of any kind, but are cousins to Gelbvieh. Today nearly 40% of all cattle in Switzerland are Braunvieh.
I hope that helps!!!