Purina Mills, LLC is the farm animal feeds unit of Land O' Lakes. It was previously part of Ralston Purina, but the U.S. animal feeds portion was sold in 1986. Purina traces its roots back to 1894, when founder William H. Danforth began producing feed for various farm animals under the name Purina Mills. The predominant brand for each animal was generally referred to as "Chow"; hence there was "Purina Horse Chow", "Purina Dog Chow", "Purina Cat Chow", "Purina Rabbit Chow", "Purina Pig Chow", and even "Purina Monkey Chow". Later, in 1902, he merged with university professor Webster Edgerly, founder of Ralstonism, who was at the time producing breakfast cereals, to form the "Ralston-Purina Company". Ralston Purina sold Purina Mills, the U.S. animal feed business, to British Petroleum in 1986, while retaining the pet food and international animal feed businesses. In 1993, the Sterling Group of Houston led a leveraged buyout of Purina Mills. In 1998, it was purchased by Koch Industries, but a U.S. bankruptcy court cancelled out all equity held by Koch to maintain the companys viability. Purina Mills was purchased by Land O'Lakes in 2001.