Of course, cows haven't always produced so much milk. As Nicolette Hahn Niman accounts in her book Righteous Porkchop: Finding a Life and Good Food Beyond Factory Farms, early in our country's history, cows weren't even milked year round, but only in the months where there was good enough grass. "Like cured meats, butter and cheese were methods of preserving milk during the seasons of plenty for the cold months to come,"
And cows used to serve multiple purposes -- milk, meat, and labor. But increasingly cows were bred for single traits, such as milk production. After World War II, industrialization of our food system ramped up with the availability of cheap energy, pesticides, fertilizers, and mechanization. By 2005, Niman writes, cows' yields were increased by seven fold in a century's time -- mainly through manipulations of breeding and diet and the additions of antibiotics and hormones