 Due to discoveries by Justus von Liebig and others, they thought that any feed that contains a set amount of protein, carbohydrates, fats, salts, and water was equivalent to any other.Babcock did not believe them, and joked with his German colleagues that cows could survive on coal and ground-up leather according to their calculations.After Hart replaced him as department chief in 1906, Babcock and others created an experiment to test his hypothesis.