United States Department of Agriculture

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Economic

Research

Service

Economic

Research 

Report 

Number 175

September 2014

United States Department of Agriculture

Climate Change, Heat Stress, 

and U.S. Dairy Production

Nigel Key, Stacy Sneeringer, and David Marquardt

September 2014

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at www.ers.usda.

gov/publications/erreconomic-researchreport/err175

Nigel Key, Stacy Sneeringer, and David Marquardt

Climate Change, Heat Stress, 

and U.S. Dairy Production

What Is the Issue?

In many parts of the United States, climate change is likely to result in higher average temperatures, hotter daily maximums, and more frequent heat waves, which could increase heat stress 

for livestock. Heat stress is characterized by changes in respiration, heart rate, sweating, blood 

chemistry, and hormones. It can also alter the metabolism of minerals and water and the digestion of nutrients. Animals generally increase their water intake and reduce their feed intake. 

Depending on the species, heat stress can reduce meat and milk production and lower animal 

reproduction rates. Livestock producers can mitigate heat stress with shade structures, cooling 

systems, or altered feed, but these methods increase production and capital costs. Dairy cows 

are particularly sensitive to heat stress; higher temperatures lower milk output as well as its fat, 

solids, lactose, and protein content. 

The U.S. Global Change Research Program (USGCRP) recognizes that increased heat stress will 

increase livestock production costs, lower feed efficiency, and compromise livestock health. While 

the physiological and production responses to heat stress have been widely studied, there have 

been no attempts to quantify the costs to the U.S. dairy industry of climate change-induced heat 

stress. In this report, we use operation-level economic data coupled with finely scaled climate data 

to estimate how the local thermal environment affects U.S. dairies’ effectiveness at producing 

outputs with a given level of inputs. We use this information to estimate the potential decline in 

milk production in 2030 resulting from climate change-induced heat stress.

What Did the Study Find? 

The report found evidence of a significant negative relationship between heat stress and the 

productivity of U.S. dairies. In 2010, heat stress lowered the value of annual milk production 

for the average dairy by about $39,000, which equates to $1.2 billion in lost production for the 

entire dairy sector. 

Climate model predictions indicate that, on average, U.S. dairies will experience an annual 

temperature increase between 1.45 and 2.37 degrees Fahrenheit by 2030. Assuming no 

adjustments in milk prices, we estimate that the additional heat stress from climate change will 

in 2030:

• Lower milk production for the average dairy by 0.60 to 1.35 percent, depending on the 

climate model used; 
• Cause some production loss to almost all dairies, with 4 to 18 percent of dairies experiencing a loss greater 

than 2 percent; 

• Lower total annual production at the State level between 0.05 percent and 4.4 percent, with the greatest 

losses occurring in Southern States; and

• Lower receipts from total annual milk production at the national level by $79-$199 million, at 2010 prices.

Allowing for higher market prices resulting from the contraction in milk production, we estimate that additional 

climate change-induced heat stress will in 2030:

• Lower consumer welfare by $64-$162 million because of higher milk prices, and

• Lower producer welfare by $42-$108 million because of higher production costs. 

Allowing for a continuation of past trends in dairy location and scale of production does not substantially alter 

the magnitude of the estimated effects of climate-induced heat stress on dairy production. Production effects in 

the study were mitigated only slightly if dairies moved out of regions forecast to undergo the greatest increases 

in heat stress, because dairies in these regions contribute relatively little to national output. 

While the estimated reductions in output are modest over the next 20 years, losses from heat stress could 

increase substantially in later decades, depending on the extent of future climate changes. However, there is 

potential scope for adaptation to future climate change. Because the effects of climate change-induced heat 

stress will likely increase gradually over time, costs can be mitigated by research and development into heat 

mitigation technologies and practices. Possible innovations include energy-efficient cooling for animal housing, 

the adoption of heat-tolerant breeds, and improvements in scientific knowledge about the interactions among 

feed, nutrition, and heat stress. 

How Was the Study Conducted?

This report uses operation-level economic data and finely scaled climate data to estimate how the local thermal 

environment affects the technical efficiency of U.S. dairies. We first estimate the average annual heat load for 

livestock—the amount of humidity-adjusted heat that animals are exposed to—in different regions using 16 

years (1990-2005) of daily weather data. We match this climate information with farm production data drawn 

from the Agricultural Resource Management Surveys of U.S. dairies conducted jointly by USDA’s Economic 

Research Service and National Agricultural Statistics Service in 2005 and 2010. We then estimate the relationship between the average annual heat load and dairy productivity using an econometric production model. 

Results from this model provide information about how much milk output would decline if there were an 

increase in the heat load. 

Next, we use forecasts from four global climate models to provide a range of predicted heat loads in different 

regions in 2030. Using these climate forecasts and estimates from the econometric production model, we forecast the potential milk production losses associated with climate change. We explore how the magnitude of the 

production effects varies across States. We also explore how these effects would differ if geographical growth 

patterns in milk output were to follow historical trends, or if production were to shift from States experiencing 

relatively large increases in temperature to States experiencing smaller increases. 

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