In 1924, the U.S. dairy herd consisted of approximately 21 million cows, each producing around 4,167 pounds of milk annually. At the time, the average cow consumed about 21.4 pounds of dry matter (DM) daily. Advancements in genetics, nutrition, and management have led to a dramatic improvement in intake, productivity, and efficiency today.
The U.S. dairy herd now has 9.36 million cows — a 55% reduction in herd size from 1924. Each cow now produces, on average, 24,200 pounds of milk annually and eats approximately 60 pounds of DM daily. This shift has resulted in a three-fold bump in feed efficiency, as modern dairy cows produce significantly more milk from each pound of feed.
Despite this rise in individual productivity and intake, total methane emissions have declined since 1924 due to the reduction in herd size and greater feed efficiency. This underscores the environmental progress achieved in dairy production as the industry produces more milk with fewer cows and less total methane emissions.
Using the Ellis Model, a common tool in agricultural and environmental studies, we estimated daily methane emissions for dairy cows in both 1924 and 2024 based on their dry matter intake (DMI). Methane is measured in megajoules (MJ) to reflect its energy content, as each kilogram (kg) of methane contains approximately 55.5 MJ.
Continue reading this article published in Hoard’s Dairyman.
