U.S. livestock agriculture contributes a total of 4.2% of all U.S. GHG. "Globally, the U.S. Livestock sector is the country with the relatively lowest carbon footprint per unit of livestock product produced (meat, milk or egg),” says Mitloehner.

Of the 4.2%, beef cattle contribute 2.2%, dairy cattle 1.37%, swine, 0.47%, poultry, 0.08%, and sheep and goats, 0.04%. Horses contribute another 0.04%. “[These numbers] are very far from the 18 to 51% range that advocates often cite,” he says. In contrast, the U.S. transportation sector contributes 27% and energy production contributes 31%.

“The reason for [livestock’s] achievement largely lies in the production efficiencies of these commodities, where by fewer animals are needed to produce a given quantity of animal protein food,” he says.

U.S. dairy cows produce on average 22,248 lb. of milk per year compared to Mexican cows which produce 10,500 lb. and Indian cows which produce 2,500 lb. Consequently, it takes two Mexican cows to produce as much milk as an American cow, and it takes nine Indian cows to produce that same amount. “Production efficiencies are inversely related—when the one rises, the other falls,” Mitloehner says.

Comment:  Finally, some good news about agriculture in the U.S.

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