Final answer:
Corn replaced grass and hay as the principal cattle feed due to its cost-effectiveness and policies that made it abundantly available. The shift to corn has been influenced by economic factors and government policies, while also reflecting changes in agricultural practices over time.
Step-by-step explanation:
Corn, also known as maize, replaced grass and hay as the principal feed for cattle. This shift was largely due to economic factors, as corn became a more cost-effective option. Historically, cattle grazed on grass, which is their natural diet. However, with agricultural practices and government policies making corn both abundant and inexpensive, farmers began to feed cattle corn to fatten them quickly for market. This practice not only catered to economic efficiency but also to the demands of a growing market for beef. Today, cattle are often raised in feedlots where they are fed a steady diet of corn and silage, a transition that has been influenced by crop production trends and prices, as demonstrated in the case of the upper Midwest region once known as "King Wheat."
Corn's significance goes beyond just feeding livestock; it is a staple crop developed thousands of years ago in central Mexico and has been selectively bred to produce more and bigger seeds over generations. It is incredibly versatile and used to make a variety of products, including biofuels like ethanol, plastics, and as a fundamental food source for both humans and animals. U.S. government policies have affected the production of corn in several ways, including the support of biofuel manufacturing and policy decisions that indirectly encourage the use of corn in school lunches and other food products.