Handling Cattle in High Temps, Humidity

OMAHA (DTN) -- Temperatures this week will be dangerous for crops, people and livestock. The highest temperatures of the year could be seen this week in much of the central United States.

Livestock producers should implement different hot weather management strategies to keep their animals comfortable. High temperatures and high humidity levels are a bad combination for livestock, according to experts.

RECORD AUGUST HEAT

The heat is forecast to continue through Thursday this week, according to DTN Ag meteorologist Emeritus Bryce Anderson. In an Ag Weather Forum blog titled "Record August Heat Threatens Crops and Livestock," Anderson writes a powerful heat-producing high pressure dome in the Midwest is pushing temperatures upward (https://www.dtnpf.com/…).

Excessive heat warnings have been issued across the central and southeastern Plains through the western, central and southeastern Midwest.

The formation of former tropical storm Hilary in the eastern Pacific Ocean enhanced the intensity of this event, he wrote.

"Hilary is definitely playing a role in the intensity of the (central U.S) heat ridge," Nathan Hamblin, DTN weather risk communicator, said in the article.

DANGEROUS HEAD INDEX VALUES

Dangerous heat index values are in store for the Midwest, Anderson wrote. USDA Midwest Climate Hub Director Dennis Todey said in an email to Anderson that drying of ground in areas that recently received rain, along with plant evapotranspiration (ET), will be significant and contribute to the high heat index.

"So, you have sinking air ... increasing temperatures and then moisture from the surface that is also trapped under the ridge," Todey said. "Perfect set-up for high heat index episodes."

By the afternoon of Aug. 21, some areas in the central part of the country were already reaching almost 120 degrees Fahrenheit heat index, or what the temperature felt like with the humidity.

WATCH LIVESTOCK IN HIGH TEMPS

Anderson wrote livestock are in peril from this stressful heat and the high heat index potential.

Todey said livestock producers don't have many options with this high of heat index. Watering to cool animals doesn't do much and can actually make the situation worse by increasing the dew point around the livestock, he said.

High temperatures and rising levels of relative humidity are a bad combination for both feedlot and cow-calf operations, according to AJ Tarpoff, KSU Extension veterinarian, in a past interview with DTN. Cattle in feedlots can see higher levels of mortality, while cows in cow-calf operations tend to have issues with low levels of reproductivity if heat stress is bad enough.

Tarpoff said cattle dissipate heat less efficiently than other animals. They will pant to try to remove the heat through respiratory methods and will also sweat some, but only 10% of what human beings sweat.

Several factors affect how cattle dissipate heat, including body condition score (bcs), weight, existing health issues, hair color and hair coat thickness.

Cattle internal temperature peaks two hours after the peak of the environmental temperature, so even though the hottest part of the day is over, cattle could still be extremely hot. It takes at least six hours to dissipate the heat load on cattle, he said.

Tarpoff said day-after-day of hot conditions -- such as this week -- creates an accumulated heat load on cattle.

"This load is not able to be dissipated with just one overnight period," he explained.

MANAGEMENT CONSIDERATIONS

There are certain management practices that may limit the effects of heat stress on cattle.

Tarpoff recommended cattle producers have a plan in place to handle these conditions before the heat arrives.

This includes altering the feed -- reduce feeding activity during the hottest part of the day. Specifically, 70% of the daily feed could be delivered as late as possible in the afternoon.

Also, change how to handle the cattle: Never process cattle in the heat of the day, and if you do have to work the cattle, try to finish this chore by 10 a.m., he said.

HEAVIER CATTLE PRESENT STILL

South Dakota State University Extension Beef Feedlot Management Associate Warren Rusche wrote about how heavier cattle in feedlots can be more susceptible to heat stress (https://extension.sdstate.edu/…).

Fatigued cattle syndrome (FCS) is a condition that affects cattle mobility near the time of processing, Rusche said. Cattle affected by FCS display an unwillingness to move or in severe cases can go down.

Rusche said feedlot workers should move these cattle slower; cattle walked to a load-out area are much less likely to develop FCS, compared to those handled at a trot. If possible, move cattle to a pen closer to the load-out area, which minimizes the distance the cattle need to travel on shipping day.

Rusche said feedlot operators need to be aware of increased animal health concerns as temperatures increase. Heavier cattle don't tolerate hotter weather as well, especially if they have black hides.

"Strategies such as shades or sprinklers can make a big difference in relieving heat stress conditions in feedlot cattle," Rusche wrote.

Tarpoff said sun shades and sprinklers can be useful if they are used correctly.

Sun shades should cover 20 square feet per head per pen. This is a considerable investment; a more economic method to incorporate shade is to use it on the heaviest cattle or sick pens, he recommended.

Sprinklers should be used to wet cattle, but not create mud in the pen, Tarpoff said. Use them early in the morning or overnight -- don't run them in the heat of the day since this increases humidity in the pen environment.

Water availability should be watched closely during hot weather. Feedlot cattle should have 2 to 3 inches of trough space per head, he said.

"As the temperature goes from 70 degrees to 90 degrees, that animal will consume double the water consumption," he said.

HEAT STRESS TOOLS AVAILABLE

Tarpoff said cattle producers have many tools to monitor conditions available to them.

One of the most basic tools is the temperature and humidity index chart, which can be found in many different places. By knowing the temperature and humidity, producers can get a snapshot in time of current conditions and make pinpoint decisions from there, Tarpoff said.

Also, use the U.S. Meat Animal Research Center (USMARC) Forecast Maps (https://www.ars.usda.gov/…). This website consists of a seven-day forecast of cattle heat stress for the continental U.S., Tarpoff said.

For Kansas cattle producers, the Kansas Mesonet Animal Comfort Index (https://mesonet.k-state.edu/…) can give an up-to-the-minute update of heat stress across the state. A chart can be constructed to give even more details of heat stress in the last seven days, he said.

The University of Nebraska-Lincoln (UNL) Extension also wrote an article last week detailing resources available to cattle producers to combat heat stress. The article can be found at https://beef.unl.edu/….

MyDTN customers can access online the DTN Cattle Stress Index tool, which calculates conditions throughout the year. Type "Cattle Stress Index" in your MyDTN site's search box, then scroll down the Ag Weather page. You can set alerts and updates on when conditions reach specific values you configured for weather, including temperature and humidity.

Russ Quinn can be reached at Russ.Quinn@dtn.com

Follow him on X, formerly known as Twitter, @RussQuinnDTN

(c) Copyright 2023 DTN, LLC. All rights reserved.