Final answer:
Since the 1940s, there has been a dramatic shift in energy inputs for raising cattle, moving from a system where food production required less energy than the food's energy content.
Step-by-step explanation:
The way we raise cattle today is vastly different from the practices of the 1940s. Previously, in the early phases of agriculture, the energy content of the food produced was significantly higher than the energy input required for its production. However, with the modernization of agriculture, especially since the industrial transition, the balance has shifted dramatically. In contemporary farming, particularly in the United States, the energy content of food is substantially less than the energy used in its production and supply chain. The majority of this energy is spent in the form of fossil fuels, which underscores a significant increase in energy inputs over the past decades.
The shift towards industrial farming has led to an increased reliance on fossil fuels for mechanization, transportation, and the synthesis of agricultural chemicals. This has resulted in a greater energy expenditure in raising cattle. For example, the production of 1000 dietary calories (kcal) through cattle farming is far more energy-intensive than producing the same caloric content via crops such as corn or soybeans.