Sheep eat bull thistle seedlings or small rosettes.
Although bull thistle made up 1 percent of the total seed plant canopy coverage in bighorn sheep wintering areas just outside Yellowstone National Park, the bighorn sheep did not use it. In Europe, goldfinches and linnets feed on bull thistle seeds. Because of its spiny stems and leaves, bull thistle is unpalatable to most livestock. The energy value and protein value of bull thistle for livestock is poor. The taproots of rosettes are peeled, boiled, and eaten, or the boiled roots are dried and ground into flour.