DETROIT LAKES, Minn. — It was a warm June evening when Nick Disse steered a pickup truck into the forested corners of Rock Ridge Bison Ranch, the couple-hundred-acre spread his family has worked and built for nearly 150 years. In the truck bed, his youngest son, Griffin, rode along, hopping out every so often to swing a gate open or closed. Beside Nick sat his wife, Paula. His daughter, Emma, was in the back seat. They were looking for the herd.…