generally said to have occurred along with the Industrial Revolution. It came about in part because of the Industrial Revolution and it helped allow the Industrial Revolution to happen. The second agricultural revolution was based on a greater use of technology.
Mechanization began replacing animal and human labor in the United States during the late nineteenth century
GMO's cause animals to create more fat so they can't act like they normally do. Also they feed them the wrong food so there waste which can be a fertilizer is now just sittin there.