Time to Talk Heat Stress!

By David Schmidt

Reprinted from: Animal Ag

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On June 9 the temperature climbed to 97 degrees F in Western MN. Not an unreasonable temperature for the region but maybe a little early in the season. This got me thinking about heat stress. I know some regions of the US are well into heat stress season but we are just getting there.

The good news is that reminders about heat stress, and what do do about it, are coming from everywhere. The most recent heat stress article that came across my desk was from Morning Ag Clips entitled “Don’t let your reproduction suffer this year.” The article summarized a study on reproductive losses in dairy that suggested pregnancy losses could occur with max THI (Temperature-Humidity Index) values as low as 55. The general recommended threshold value is an average (17-hour) THI of 68. 

I think most of us understand the general impacts of heat stress on productivity and all the nuances of impacts (night time cooling, acclimation, animal health, etc.). This makes parsing out the economic impact data from heat stress very challenging.

The USDA Economic Research Service recently made an attempt to quantify the losses in a report (September 2014) entitled “Climate Change, Heat Stress and U.S. Dairy Production“. They predicted the current loss in the US dairy industry to heat stress is about $1.2 billion per year. This estimate was based on many assumptions and statistics but gives some idea of the magnitude of the problem. On a per cow basis (average across the US, ignoring geographic variability and lots of other things) this is about a 5.8% loss in milk production per cow per year.

The report goes on to project the economic impacts of heat stress on the dairy industry in 2030 and 2050. No surprise, the results suggest even greater impacts (losses) in the future.

To me, there is no need to go beyond the current impacts and wonder what economical adaptation strategies can be put in place to reduce these losses now. From the numbers in the report, heat stress is currently costing about $250 per cow per year in lost milk production. What kind of cow cooling can be purchased for $250 per cow per year??

In case you did not know it, the USDA puts out cattle heat stress 7-day forecast maps. Yes, specific to cattle, but I think any species (even human) could find these forecasts useful.

Always Considering Climate – David

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