Caring for Cattle During Heat Wave

DTN Staff

OMAHA (DTN) -- As a short but intense heatwave has been shifting across the country and the National Weather Service has been issuing extreme heat watches and warnings, livestock producers and feedlots will monitor and take extra steps so their cattle can handle dangerous heat and humidity levels.

Heat waves can stress livestock housed outside and change their water consumption. This could lead to poor weight gain, sickness and even death.

In this article, DTN includes some of the advice given by extension educators and other sources in past DTN stories on how to help cattle through high heat and humidity.

TRIPLE-DIGIT HEAT INDICES IN DAYS AHEAD

DTN Ag Meteorologist John Baranick wrote in his blog on Tuesday about how the potentially record-high temperatures experienced in the Southwest would shift eastward into the Plains. He said temperatures "will be well into the 90s and some pockets of triple-digit heat will pop up from western Kansas through southern South Dakota for a couple of days. The upper limit to the heat may not make it all the way up to the Canadian border in the Plains, but as the heat continues to drift eastward with the upper ridge this weekend, it will likely do so for southern Ontario.

"Meanwhile, temperatures in the 90s will overspread most areas east of the Rockies this weekend. Combined with high dew points in the 60s and 70s, heat indices are forecast to reach into the 100-110 F range for several days. This heat will shift mostly to the East Coast and Southeast as temperatures slowly back off early next week."

Baranick added, "Though the extreme heat will relax, temperatures will still be much above normal for this time of year for a lot of the eastern half of the country throughout next week." (https://www.dtnpf.com/…)

WHY IT MATTERS TO CATTLE

In a DTN article last year, Baranick stressed it is most important to watch the combination of temperature and humidity, and especially with fat cattle as they seem to be more susceptible to those conditions. "Truly, the combination of heat and humidity is bad for all animals, but to what degree is that dangerous for cattle is what needs watched," he said.

Still air with hot humid conditions and no clouds or precipitation becomes blistering. Lower temperatures at night help relieve the animals and forecasts into the 60s at night with winds acts as a nice air conditioner for them, Baranick said. However, highs in the mid- to upper-90s with dewpoints in the upper 60s to mid-70s -- such as forecast for this week -- aren't good for any animals.

HEAT STRESS ON CATTLE

Perhaps one of the worst recent cases of heat stress took place almost exactly three years ago as thousands of cattle died in Kansas feedlots. "Temperatures in the area were over 100 degrees Fahrenheit, there was humidity, and there was little to no wind to help cool the animals," DTN reported on June 20, 2022. "Temperature readings reported for Ulysses began to exceed the 100-degree mark on June 11. By June 13, the high temperature was reported at 104 degrees, with humidity levels ranging from 18% to 35%. Temperature and humidity levels began to break some on June 14. Just a few days prior to the heat setting in, highs had been in the 80s." (https://www.dtnpf.com/…)

A veterinarian who worked with feedlots in the Kansas area that got hit hard with losses in 2022 told DTN at the time that when a heat stress event hits, those animals most greatly affected are the ones toward the end of the finishing period. For three days that June, temperatures were in the triple digits, with nighttime humidity and little to no wind.

"These cattle were big, fat, ready to go to harvest, and for the most part, they were black-hided," Nels Lindberg said. He estimated weights for animals at that phase typically between 1,250 and 1,500 pounds each.

Baranick looked at the data tied to those three days of heat around the Ulysses area where the cattle died. He noted that dew points started to break into the higher 60s and hold there through the night, beginning Saturday. A dew point is the temperature air has to be cooled to reach a relative humidity of 100%. In general, dew points in the 50s during the summer months are comfortable. Once dew points hit 60 and above, they are considered to be extremely muggy and humid. The air temperature can never go below the dew point.

"Normally, we don't see dew points that high without it being windy as well," Baranick added in the 2022 article. "Usually, this part of the country sees the heat, but the lower dew points allow cattle to cool overnight. When this event took place, the higher dew points did not allow for that cooling. Also, we weren't seeing the winds we typically would under the conditions we had." (See more at https://www.dtnpf.com/…)

CATTLE CAN'T DISSIPATE HEAT EFFECTIVELY

"Typically pasture cattle aren't as susceptible to heat stress as feedlot cattle," said Grant Dewell, Iowa State University Extension beef veterinarian, last year in a DTN story. (https://www.dtnpf.com/…) "Pastured cattle have the ability to seek shade, water and air movement to cool themselves. Radiant heat from dirt or concrete surface is increased for feedlot cattle. At temperatures above 80 degrees Fahrenheit, cattle endure physiological stress trying to deal with their heat load."

Dewell said cattle cannot dissipate their heat load very effectively as compared to other animals, since they don't sweat effectively and rely on respiration to cool themselves. The fermentation process in their rumen generates additional heat in their body.

"During extreme weather conditions with insufficient environmental cooling at night, cattle will accumulate heat that they cannot disperse," he said.

TIPS FOR FEEDLOTS

Rob Eirich, University of Nebraska-Lincoln (UNL) director of Beef Quality Assurance and extension educator at the University of Nebraska-Lincoln in the Animal Science Department, said airflow in feedlot pens is very important to help animals cool down, as well as providing shade and sprinklers to help limit heat stress on those cattle. Ample access to water is important as well, as water consumption is the fastest way to reduce body temperature.

UNL developed a chart to help producers determine the risk facing cattle based on the temperature and the percent of relative humidity, Eirich said. The chart is based on research done by UNL and the USDA Meat Animal Research Center in Clay Center, Nebraska.

Eirich recommended on hot days feedlots process cattle early in the morning hours before 10 a.m. Working cattle can increase body temperature depending on the environmental conditions and processing time.

Some say handling cattle in the evening is good, but there is still a risk due to the animal's body temperature being elevated from high outside temperatures, Eirich said. He recommended that during the hottest season cattle be worked in smaller groups, so they don't stand in holding areas much longer than 30 minutes. Cattle producers should also consider having shade and good air movement in facilities.

"Work cattle slowly and use low-stress handling techniques," he said. "Processing cattle in any temperature elevates the animal's core temperature."

Eirich also suggested feedlot operators should consider reading UNL's NebGuide titled "Feedlot Heat Stress Management Guide" which can be found at https://extensionpubs.unl.edu/….

HEAD AND HUMIDITY IMPACT ON HEAVIER CATTLE

Dewell said to especially watch the heavier cattle in a feedlot when conditions are hot and humid as they cannot handle heat stress compared to lighter weight cattle. The increase in fat deposition prevents cattle from regulating their heat effectively. Black-hided cattle can have more problems with heat than other hide colors.

"Cattle that had severe respiratory disease early in the feeding period will have decreased ability to regulate their heat load," he added. Extra water tanks can be added to pens to be sure cattle are consuming the proper amount of clean water. He recommended a 1,000-pound animal needs about 1.5 gallons of water per hour.

Another recommendation is to feed cattle at least 70% of their feed two to four hours after peak ambient temperatures as heat production from feed intake peaks four to six hours after feeding. Changing the ration by lowering the energy content of the diet can decrease the heat load also.

Fly control is also important for both feedlot and pasture situations. Biting flies cause cattle to bunch up and decreases body cooling. (For more on how to control different flies to provide economic losses, see https://www.dtnpf.com/…)

NEED FOR ADDITIONAL WATER

The need for additional water consumption by beef cattle, especially, can lead livestock to experience water deprivation and salt toxicity.

"On hot days, animals will hover around a watering device. If there is only one in a pen or limited flow, and they cannot consume water for even two hours, water deprivation can become an issue," Steve Ensley, Kansas State University veterinary toxicologist, said in a DTN article last year.

The problem of water deprivation can happen at the same time as a condition called salt toxicity. Ensley explained that when an animal dehydrates, its body will pull fluid out of its brain. Then, sodium stored there gets trapped. The animal's inability to disperse this sodium outside the brain can create a toxic level of sodium. According to a North Dakota State University news release (https://www.ag.ndsu.edu/…), symptoms of salt toxicity in cattle can include salivation, increased thirst, abdominal pain and diarrhea followed by wobbling, circling, blindness, seizures and partial paralysis. "Sometimes the cattle become belligerent. Other central nervous signs include dragging a hind limb or knuckling of the fetlock joint," the release stated.

Alfredo DiCostanzo, a University of Nebraska Extension educator, said various factors affect water intake. Temperature, humidity and feed intake are the main drivers that affect how much water is needed.

HOW MUCH WATER DO CATTLE NEED?

"A quick reference to keep in mind as heat and humidity approach heat stress levels is the requirement of 1 gallon of water per pound of dry matter consumed," DiCostanzo said. "With warm nights and hot days, cattle are consuming 25 to 30 pounds of dry matter and will need to have access to 25 to 30 gallons of water daily."

According to DiCostanzo, cattle under heat stress will need the water they require for a 24-hour period to be available more quickly during periods of high heat. Feedlot managers should have water available sooner than usual with water flowing at a minimum of 8 to 10 gallons per minute to meet the needs of the cattle. At an expected water drinking rate of 1.1 to 3.7 gallons per minute, every animal must spend 7 to 22 minutes daily at the water trough.

"Adding extra water tanks to increase water access in 'problem' pens can help reduce heat loads caused by crowded water tanks, poor air movement, or lack of shade," he added.

Ensley said a feed bunk can be used to help with adding water for animals.

"Plug up a pen's feed bunk, fill it with water and sort half the animals out of the pen," Ensley said. "Allow them to drink for five minutes, and then rotate the other half back in. Do that every hour for 10 to 12 hours or until the animals are not rushing to water."

WHAT IF CATTLE ALREADY DEHYDRATED

If animals are already dehydrated and suffering from salt toxicity, allowing them to drink their fill of water too quickly can cause water intoxication, and they will display clinical signs quite quickly. Within 60 minutes of drinking too much, their brain will swell, and they can have seizures, collapse and not be able to get up. Some animals will get aggressive because of the damage to the neurons in the brain. If the condition progresses rapidly, it can lead to death.

Dehydrated animals suffering from salt toxicity should drink water in small amounts at frequent intervals, according to the NDSU news release. Severely affected animals may need to be given water by a stomach tube.

There is no antidote or specific treatment for water deprivation salt toxicity, so preventing dehydration by ensuring animals always have access to fresh water is critical, according to the NDSU news release.

Ensley advised installing a monitoring device on water distribution systems before extremely hot temperatures to ensure the pens are getting an adequate amount of water with good water flow.

"Livestock that have recovered from salt toxicity/water deprivation may have long-term effects," Ensley said. "They could go partially blind, but there are no food safety concerns," he said. "They should get up to the bunk and eat and drink. Producers should allow them to finish the feeding period." (See DTN article, "Heat Wave Changes Cattle Water Needs," https://www.dtnpf.com/….)

More management practices can be found at "Management Practices Important as High Temperatures, Humidity Stress Cattle," https://www.dtnpf.com/….

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Editor's note: This story includes information from previously published DTN stories by DTN staff.

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