BROOKINGS, S.D. — Heat stress in the livestock herd is always a concern during the dog days of summer. However, this year producers need to be even more cautious due to the large number of heavier cattle that have been backed up in feedlots with packer capacity continuing to be strained by labor issues and workers contracting COVID-19.
South Dakota State University Extension Ruminant Nutrition Specialist Warren Rusche says the cattle industry set itself up for the perfect storm. The U.S. Department of Agriculture data indicates carcass weights are running from 40 to 45 pounds over a year ago, which means live weights are significantly higher than normal. To compound that, a larger percentage of cattle in the Northern Plains are black hided and retain heat.
Heavier cattle are more susceptible to heat stress and may feel the effects at lower temperatures and humidity than cattle that are not carrying excess weight.
“Simply because as that animal’s mass increases you know their ability to dissipate heat goes down, just because think of it this way, they’re a bigger furnace,” Rusche says.
He says an 1,100- or 1,200-pound steer can tolerate hotter temperatures than a 1,600-pound steer.
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“And we know there are cattle that size here in the Northern Plains and that may be the tipping point for some of those,” he says.
Those cattle will need to be closely monitored this summer for signs of stress to prevent a train wreck and additionally marketed as timely as possible.
Rusche says one factor that will help is cattle have been able to acclimate to the heat over time. He says the biggest problem is when the weather goes from cooler springtime temperatures to excessive heat quickly and cattle have not had time to become adapted.
There are many strategies for preventing heat stress and death loss in the herd, such as avoiding unnecessary cattle handling or avoiding the heat of the day if producers do have to work or move cattle to market.
“Those cattle should be handled early in the morning to try to minimize the heat stress,” he says.
Other interventions that don’t require a big investment including making sure livestock have access to additional water, which Rusche says may require bringing in additional tanks. Air movement is also critical, and cattle producers are advised to take inventory of their feedlot facilities. There may be some pens that do not have adequate air movement and may need to stand empty for the summer.
“Or at least don’t put those nearly market ready heavy black cattle in. We want to put them somewhere where they can get a little more air movement,” he says.
Some operations also have had success in putting bedding out because it helps insulate the heat from the black soil being transferred over to the animal, plus it reflects some sunlight.
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Longer term investments consist of things like adding shades to the pens or a sprinkler system.
“The advantages of a shade system are that once they are set up, it’s a set it and forget it technology. The downside is, it an investment,” Rusche says.
If dollars are limited, those shades can be strategically placed where the most susceptible cattle are located such as over a sick pen or where the heavy market ready cattle are concentrated. Sprinkler systems are also very effective especially when combined with good air movement. The challenge is those must be managed and timed. If cattle are shocked with cold water too late producers can do more harm than good, and it adds to the mud in the pens.
Nutritional options such as ration changes are much more limited.
“Adding more roughage probably helps from a standpoint of keeping cattle on feed, but digesting roughage adds heat to the metabolic system of the animal,” he says.
Plus, once cattle go off feed and intake drops it can be difficult to get them back on a normal ration, especially as they get heavier. However, there are some additives on the market some producers are using with success and Rusche recommends discussing those options with a cattle nutritionist.
Bunk management is a better approach from a nutritional standpoint. Rusche recommends changing the time cattle are fed to the cooler times of the day. He says that will help animals deal with the metabolic heat load.
“Splitting the feeding or shifting more of the feed deliveries to late afternoon or early evening helps. It’s sort of like us: If we eat a big meal in the heat of the day, we don’t feel so good,” he adds.
