Where have all the dairy bulls gone? By JERRY WEBB NEWARK, Del. - A catalog of changes that have taken place on America’s farms over the last 40 years would have to include such notable prograss as the adoption of hybrid corn, the disappearance of draft horses, the introduction of the combine and self-tieing baler, and a trend toard bigness. Scientists point proudly to their work with fertilizers and pesticides, and the in ventors and manufacturers beam over the mechanization