Why do cows eat chocolate?

Now, this is a question that someone asked me because of the chocolate milk question (link here). So here's the thing, ONLY, brown cows eat chocolate. The reason that brown cows eat chocolate is that there are machines on the farms that identify if a cow is brown or not and if it is, then the machines will feed it chocolate. The farmers have it this way because they love chocolate milk, and there is no other way to obtain it than getting it from brown cows. Research shows that regular cows will not produce chocolate milk if they eat chocolate as brown cows do. Nobody really knows why.