URBANA, Ill. — Livestock agriculture is bearing the cost of extreme weather events. A new study from the University of Illinois Urbana-Champaign explores how heat stress affects U.S. dairy production, finding that high heat and humidity lead to a 1% decline in annual milk yield. Small farms are hit harder than large farms, which may be able to mitigate some of the effects through management strategies.
“Cows are mammals like us, and they experience heat stress just like we do. When cows are exposed to extreme heat, it can have a range of negative physical effects. There is an increased risk of infection, restlessness, and decreased appetite, which leads to a decline in milk yield. For dairy producers, the heat impact is a direct hit on their revenue,” explained study co-author Marin Skidmore, assistant professor in the Department of Agricultural and Consumer Economics (ACE), part of the College of Agricultural, Consumer and Environmental Sciences at the U. of I. She conducted the study with Jared Hutchins, assistant professor in ACE, and Derek Nolan, Illinois Extension specialist and teaching assistant professor in the Department of Animal Sciences at the U. of I.
Skidmore and her colleagues analyzed milk production data from nine U.S. Midwest states. They included over 56 million cow-level production records from 18,000 dairy farms from 2012 to 2016. They adjusted the milk data for protein and fat content to more accurately estimate milk quality, which determines the price.
“Previous studies have focused on fluid milk yield. But in our dairy marketing system, milk is sold on components. When you calculate revenue, it’s not just about how many gallons of milk, but whether it’s high-quality milk with high protein and fat content,” Skidmore said.
The researchers combined quality-adjusted production data with daily weather data for temperature and humidity. They calculated temperature-humidity index measurements, which most accurately reflect the heat stress a cow experiences, as high heat and humidity make it harder for the cow to cool down through sweating.
They found that, on average, 1% of annual milk yield is lost to heat stress. This may not sound like a lot, but it amounts to about 1.4 billion pounds of milk (adjusted for energy content) over five years for the 18,000 herds included in the study. Based on average milk prices, this is equivalent to about $245 million in lost revenue.
Read the full article from the College of ACES.
University of Illinois Extension develops educational programs, extends knowledge, and builds partnerships to support people, communities, and their environments as part of the state's land-grant institution. Extension serves as the leading public outreach effort for University of Illinois Urbana-Champaign and the College of Agricultural, Consumer and Environmental Sciences in all 102 Illinois counties through a network of 27 multi-county units and over 700 staff statewide. Extension’s mission is responsive to eight strategic priorities — community, economy, environment, food and agriculture, health, partnerships, technology and discovery, and workforce excellence — that are served through six program areas — 4-H youth development, agriculture and agribusiness, community and economic development, family and consumer science, integrated health disparities, and natural resources, environment, and energy.