PHOTO: Andrei Niemimäki/Flickr
Ryan Ridgway, DVM
August 24, 2016

Summer heat can be a blessing compared to this winter’s frigid temperatures, but it also brings many hardships for animal producers. During the summer months, your livestock are at an increased risk of intestinal parasites, flies, ticks and other illnesses.

As sloughs and surface water dry up, animals are more likely to pick up anthrax and clostridial spores, which are bacteria that survive in the soil and can often cause deadly diseases. Because the spores float on water, they rise to the surface in spring and concentrate as the water dries up. Animals then ingest the bacteria, causing diseases such as anthrax, blackleg and botulism, depending on which bacteria an animal ingests.

Summer is also a good time for algae blooms, and some types of algae—blue-green algae in particular—release toxins that are dangerous to animals. But worst and most frequent of all, livestock are at a risk of developing heatstroke just as humans are, particularly in areas of high humidity.

Every year, herds of animals die from dehydration because their water supply dried up between herd checks. At the same time, the heat stress robs producers of large sums of money because their animals aren’t producing as well as they should be.

Three Main Factors

Heat stress is caused by three environmental factors: humidity, temperature and air movement. Humidity reduces an animal’s ability to cool off by evaporative methods, such as sweating and panting. In areas of high humidity, animals experience heat stress at lower temperatures. Air movement helps cool the animal by cycling hotter air for cooler air and increasing their evaporative cooling.

To help determine the risk of livestock developing heat stress, animal researchers use livestock safety indexes such as this one:

  • Alert (75 to 78 degrees F): At this temperature range, early heatstroke is possible, and precautions should be taken, especially in confined spaces or if water is not readily available. Animals begin to decrease production due to temperature if they are not cooled off.
  • Danger (79 to 82 degrees F): These temperatures are dangerous to confined animals, and heatstroke is very likely, especially if there is no air movement or there is high humidity.
  • Emergency (83 degrees F or higher): Livestock should not be worked or moved and must be cooled down. No shade or air movement will make the heat stress worse. Fatalities are possible at these temperatures, especially with high humidity.

Temps Rise, Production Drops

Heat stress can be fatal if it is severe, and it can also impact your livestock’s production. High temperatures have been linked to reproductive problems such as reduced semen quality and lower birth weights.

They also lower milk and egg production and reduce growth rates, particularly when coupled with dehydration. Dairy cows, for example, decrease milk production by between approximately 20 to 50 percent in a single day during periods of moderate heat stress.

Your livestock’s water requirements also increase during the hot summer months. Cattle water needs approximately double from 40 degrees to 90 degrees, and lactating cows can require more than 18 gallons of water per day in average summer weather of 90 degrees, quickly leading to dehydration and death if good quality water is not available.

While other livestock species require different amounts of water, the trends are the same. As animals grow or lactate, or their environmental temperature and humidity increases, their water requirements likewise increase, so it’s important to adjust their water supply accordingly.

To minimize the impact heat will have on your herd this summer, use the following tips.

1. Match Breeds To The Environment

The best way to reduce your herd’s susceptibility to heat is by raising heat-tolerant breeds. Over time, certain breeds have evolved to thrive in heat while others do better in colder climates. If you choose a breed that naturally does better in heat, you won’t need to help keep them cool as often.

2. Always Have Water On Tap

Unless the temperature is extremely high, most of the symptoms of heat stress are actually due to dehydration. Cool, fresh drinking water also helps keep an animal’s core temperature down, reducing the risk of fatal heat stress. Always ensure there is enough space for the majority of your animals to drink at one time, as dominant animals may block others from drinking in excessive heat.

3. Provide Ways To Cool Off

Misting, water pools and mud wallows will help get your animals’ temperature down if cool water is used. Don’t use cold water, however, as it will actually slow cooling down and make heatstroke worse. Cold water causes the blood vessels in your animal’s skin to constrict, reducing how much blood is cooled.

4. Pay Attention To Air Circulation

Air circulation is important to help cool animals and move hot air out of the building. Fans help by blowing cool air at the animals, but there needs to be proper ventilation as well to ensure the heat doesn’t build up to dangerous levels.

Professor Emeritus Brian J. Holmes, farmstead engineering, at the Babcock Institute at the University of Wisconsin, writes in Ventilating Freestall Barns that a cow suffering from heat stress, placed in a barn and provided no relief will have a high respiration rate—about 100 breaths per minute.

“When air is blown at 700 cubic feet per minute onto the heat-stressed cow, her respiration rate will decline to about 90 breaths per minute,” he writes. “However, for heat stress to be significantly relieved, the respiration rate must be reduced to 60 breaths per minute.”

5. Set Up Shade Shelters

Direct sunlight increases the effective temperature by approximately 2 to 3 degrees, leading to an increased risk of heatstroke. Adequate shade lets your herd get out of the sun and reduces the risk of heat stroke.

“Livestock shelters do not need to be complicated or elaborate,” according to small ruminant educator Mike Metzger with the Michigan State University Extension. “Simple shade structures can be constructed from shade cloth, mesh fabric, tarps, canvas or sheet metal. Mature trees provide excellent shade (and shelter) and are usually the least-cost alternative.”

6. Serve Supper Later In The Day

Digestion actually produces heat—a surprising amount of heat, in fact. Feeding in the evening shifts this heat production to a cooler time of the day and it also changes when animals are most active. This frees them up to laze around through the heat of the day.

“Heat production from feed intake peaks four to six hours after feeding,” writes Grant Dewell, Iowa State University Beef Extension veterinarian.

Therefore, heat production in cattle fed in the morning will peak in the middle of the day when environmental temperatures are also elevated. Cattle should receive a least 70 percent of their feed two to four hours after peak ambient temperature. Changing the ration has been controversial but research indicates that lowering the energy content of diet will decrease the heat load. The general recommendation is to reduce the diet energy content by 5 to 7 percent.”

7. Don’t Handle Animals In The Heat

During times of heat, animals should not be handled, as muscle movement leads to increased body temperature. Only move them if it is to provide shade and water.

Dave Sparks, Oklahoma State University Cooperative Extension veterinarian and food animal quality and health specialist, says that activity level is perhaps the greatest heat stress danger. “Avoid working and processing animals when environmental factors approach the danger zone,” he warns. “If that isn’t possible, perform the activities early in the morning, before the day’s heat buildup begins and after the previous day’s heat buildup has dissipated.”

By following these tips, you can help keep your animals happy and thriving through the hottest summer months. Always remember to get advice from your local veterinarian to ensure your herd is prepared for the common issues in your area.

This article originally ran in the July/August 2015 issue of Hobby Farms.

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