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August 6, 2013
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Keeping cattle cool in summer heat critical

With the combined double whammy of intense summer heat partnered with drought conditions, it’s important to beef-up safety measures for cattle.

Whether livestock are out in the elements, or penned in, an animal science expert says they are directly and immediately affected by various current weather conditions.

“This drought has gotten everyone’s attention,” said Dr. Larry Hollis, professor and extension beef veterinarian at Kansas State University’s Department of Animal Sciences and Industry in Manhattan, Kan. “We’re having so many drought-related issues. There’s a whole list, such as lack of grass, toxic weeds, water quality and quantity, feed quantity and quality. A friend in Eureka, Kan., said he turned cows out this past weekend, and some died after drinking water contaminated with blue-green algae. We have half a dozen public lakes that already have blue-green algae warnings.”

Although some areas have received some rain and heat relief at times, Hollis is concerned about complacency, especially since heat stress is paramount right now. In fact, most of the issues that cattle are having, are resulting from effects of heat and drought-stress.

Hollis told The Fence Post, they are the two big drivers right now.

“Heat stress can kill cattle. Pay attention to what’s going on. We’ve had death losses each year in the past few years. It’s an annual occurrence. The critical things to watch are the temperature and how long it stays hot; combined with the relative humidity.”

Hollis encourages ranchers to examine and chart the temperature-humidity impact on cattle in the Livestock Weather Hazard Guide, which lists the actual air temperature, also called the ‘dry bulb temperature.’

That guide is available at

“We can look on this chart and see when the cattle are close to being in trouble, or when it’s an emergency situation. For example, when it gets to 84 degrees and we correlate it to 35 percent relative humidity, it immediately assigns it to the color-coded category of ‘alert.’ Then, we’re in trouble.”

In addition to temperature and humidity, Hollis reminds cattle producers that lack of wind and lack of cloud cover during the day, as well as lack of nighttime cooling below a 75 degree air temperature, further complicate livestock heat stress.

The combination of factors can combine to produce what Hollis calls ‘the perfect storm.’

“That will kill cattle, especially when these factors persist for three days in a row, cattle start dying,” he said.

He recommends several ways of monitoring them.

“Just watch cattle, and see how many breaths they take per minute. They pant, and that’s how they blow off heat. Their normal rate is less than 90 breaths per minute.

“An alert status is between 90-110 breaths per minute.

“Danger is 110-130.

“Emergency is over 130,” warned Hollis.

“Also watch for slobbering, that progresses to open-mouth breathing. And, watch for cattle moving to a high spot to catch a breeze,” he added.

Cattle with lung damage are more likely to die, since they have to pant a lot more anyway to compensate for reduced lung capacity, warned Hollis.

There are intensifying factors that particularly affect some breeds.

“Breeds such as non-Brahman influenced cattle are particularly impacted. Basically all our British (Angus, Hereford, Shorthorn,) and Continental breeds (Charolais, Maine-Anjou, Simmental/Gelbvieh, etc.) are more subject to heat stress. Also, fat-cattle are worse; which are prevalent in feed yards. Dark-hided cattle are worse off. Pregnancy intensifies it,” Hollis noted.

Providing shade if at all possible, is very helpful, Hollis said.

“Either natural shade such as trees, or getting under the shade of some natural object or under some sort of artificial structure like building shade is important,” said Hollis. “The thing we don’t want to do, is put cattle in a barn. Because although it will provide shade, a barn will stop the wind flow, and when cattle congregate, they generate more heat together. Weeds also grow up outside the pen and stop airflow.”

Also, in the heat of the summer, Hollis cautions against forcing cattle to stay in a low spot.

“In low spots, if there is any wind, they won’t get it. If there are any deaths, that’s where it usually happens first,” Hollis warned.

He recommends building mounds, so cattle have an elevated surface to get relief.

“In wet times of the year, mounds keep livestock dry. In hot weather, mounds enable them to gain exposure to whatever airflow is available, and catch any possible breeze,” suggested Hollis.

When considering the metabolic heat capacity of livestock, Hollis recommends feeding them late in the afternoon, so that the metabolic heat that they do produce when they eat, is not as intense.

“Cattle have an external heat load, and an internal heat load. The metabolic heat load peaks about four hours after they eat. So, you don’t want to feed them in the morning or mid-day, because four hours later, they struggle with all that heat load,” Hollis explained. “Cattle’s metabolic heat load typically increases as they digest hay. Hollis relayed that cattle produce less heat when they digest grain.

“If you have it available, feed them a higher grain and lower roughage diet, but check this with your nutritionist,” advised Hollis. It’s a metabolic heat load shift just by changing their diet.

“If you have to handle cattle during the hot months, start at first light in the morning, and be done by 10 a.m.”

Lawn-type sprinklers can be a good idea for cooling livestock. The whole idea is to dispense large droplets that wet the animal to the skin.

Hollis says, however if a cattle producer uses only mist units, such as the method used for pigs, that will raise the humidity and actually make conditions worse for the cattle. They need to have enough large droplets to wet them down to the skin.

Then, there’s the management of providing cool well water, and plenty of it. Water requirements will double during the heat.

“Normally, we figure one gallon per 100 pounds of body weight during the day. When it’s hot like this however, it doubles. So, adequate clean water, and preferably good quality water, which means it doesn’t have a lot of salt in it,” said Hollis, noting that salt increases thirst.

Cattle coming off fescue pasture grass, which often has a fungus on it, can face a difficult adjustment period when transferred to other pastures.

Hollis said fescue toxicity interferes with their ability to regulate their temperature.

“If you have that issue, it could kill them. Sometimes, when purchasing cattle especially from the southeastern states; extending as far west as eastern Kansas, Oklahoma, and Nebraska, this is a concern. Because we don’t have it in the western parts of the country, we’re not as familiar with it, so we often don’t know how to manage it. Let’s say you buy cattle in a sale barn in another state, and if it’s real hot, and they’ve been grazing fescue and you’re shipping them into a hot area, you could get into a potential wreck,” added Hollis.

Fly control is also important.

“Do a good job of fly control,” urged Hollis, “because flies make the cattle congregate and bunch up together, they can’t dissipate heat. I’ve actually seen cattle die when bunched up due to flies or when gathered for working,” Dr. Hollis advised.

Hollis had plenty of advice regarding what he calls ‘high-strung cattle,’ which can have issues in hot temperatures.

“Cows with a bad disposition should’ve been made into hamburger a long time ago. Other cattle that we call calm, gentle, or easy-to-handle cattle suffer less from heat stress. But the high-strung cattle, which are easily excitable, act like idiots and have a mind of their own and would just as soon run over you ... those are the ones that have a tougher time dealing with the heat.They’re high-strung and heat bothers them more.” ❖

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The Fence Post Updated Oct 16, 2013 02:43PM Published Aug 7, 2013 01:45PM Copyright 2013 The Fence Post. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.